anotações - cerpch

Transcrição

anotações - cerpch

Comitê Diretor do CERPCH
Director Committee
CEMIG / FAPEPE / IEE-USP / FURNAS /
IME / ELETROBRAS / ANEEL / MME
Comitê Editorial
Editorial Committee
Presidente - President
Geraldo Lúcio Tiago Filho - CERPCH/UNIFEI
Editores Associados - Associated Publishers
Adair Matins - UNCOMA - Argentina
Alexander Gajic - University of Serbia
Alexandre Kepler Soares - UFMT
Ângelo Rezek - ISEE/UNIFEI
Antônio Brasil Jr. - UnB
Artur de Souza Moret - UNIR
Augusto Nelson Carvalho Viana - IRN/UNIFEI
Bernhard Pelikan - Bodenkultur Wien - Áustria
Carlos Barreira Martines - UFMG
Célio Bermann - IEE/USP
Edmar Luiz Fagundes de Almeira - UFRJ
Fernando Monteiro Figueiredo - UnB
Frederico Mauad - USP
Helder Queiroz Pinto Jr. - UFRJ
Jaime Espinoza - USM - Chile
José Carlos César Amorim - IME
Marcelo Marques - IPH/UFRGS
Marcos Aurélio V. de Freitas - COPPE/UFRJ
Maria Inês Nogueira Alvarenga - IRN/UNIFEI
Orlando Aníbal Audisio - UNCOMA - Argentina
Osvaldo Livio Soliano Pereira - UNIFACS
Regina Mambeli Barros - IRN/UNIFEI
Zulcy de Souza - LHPCH/UNIFEI
Editorial
Editorial
Regulação
Regulation
Agenda 06
Schedule
Artigos Técnicos 07
TECHNICAL COMMITTEE
Technical Articles
Ficha catalográfica elaborada pela Biblioteca Mauá –
Bibliotecária Margareth Ribeiro- CRB_6/1700
R454
Revista Hidro & Hydro – PCH Notícias & Ship News, UNIFEI/CERPCH,
v.1, 1998 -- Itajubá: CERPCH/IARH, 1998 – v.15, n. 60, jan./mar. 2014.
Expediente
Editorial
Tradução
Revisão
Impressão
Geraldo Lúcio Tiago Filho
Camila Rocha Galhardo
Adriana Barbosa MTb-MG 05984
Adriana Barbosa
Camila Rocha Galhardo
Fabiana Gama Viana
Angelo Stano
Net Design
Lidiane Silva
Cidy Sampaio
28
Expansão via usina-plataforma
Expansion via plant-platform
Prof. François AVELLAN, EPFL École Polytechnique Fédérale de Lausanne,
Switzerland, [email protected], Chair;
Prof. Eduardo EGUSQUIZA, UPC Barcelona, Spain, [email protected], Vice-Chair;
Dr. Richard K. FISHER, VOITH Hydro Inc., USA, [email protected], Past-Chair;
Mr. Fidel ARZOLA, EDELCA, Venezuela, [email protected];
Dr. Michel COUSTON, ALSTOM Hydro, France, [email protected];
Dr. Niklas DAHLBÄCK, VATENFALL, Sweden, [email protected];
Mr. Normand DESY, ANDRITZ Hydro Ltd., Canada, [email protected];
Prof. Chisachi KATO, University of Tokyo, Japan, [email protected];
Prof. Jun Matsui, Yokohama National University, [email protected];
Dr. Andrei LIPEJ, TURBOINSTITUT, Slovenija, [email protected];
Prof. Torbjørn NIELSEN, Norwegian University of Science and Technology, Norway,
[email protected];
Mr. Quing-Hua SHI, Dong Feng Electrical Machinery, P.R. China, [email protected];
Prof. Romeo SUSAN-RESIGA, “Politehnica” University Timisoara, Romania, [email protected];
Prof. Geraldo TIAGO F°, Universidade Federal de Itajubá, Brazil, [email protected].
Editor
Coord. Redação
Jornalista Resp.
Redação
Colaborador
Projeto Gráfico
Diagramação e Arte
04
Trimestral.
Editor chefe: Geraldo Lúcio Tiago Filho.
Jornalista Responsável: Adriana Barbosa – MTb_MG 05984
ISSN 1676-0220
1. Energia renovável. 2. PCH. 3. Energia eólica e solar. 4. Usinas hi_
drelétricas. I. Universidade Federal de Itajubá. II. Centro Nacional de Re_
ferência em Pequenas Centrais Hidrelétricas. III. Título.
Joana Sawaya de Almeida
Patrícia Kelli Silva de Oliveira
Editora Acta Ltda
Hidro&Hydro - PCH Notícias & SHP News
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The Hidro&Hydro - PCH Notícias & SHP News
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ISSN 1676-0220
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3
EDITORIAL
HIDRO&HYDRO: PCH NOTÍCIAS & SHP NEWS, 60 (1), JAN,FEV,MAR/2014
Dear readers,
Prezado Leitor,
A grande luta dos empreendedores de usinas hidrelétricas com os ambientalistas, ao longo dos tempos, sempre foi em relação aos impactos
que a construção de uma hidrelétrica causa no local de sua implantação.
Há algum tempo o Brasil começou a estudar o conceito de usina-plataforma e várias pesquisas foram realizadas a respeito. A usina-plataforma
foi concebida com o intuito de causar uma menor intervenção humana ao
meio ambiente.
E esse ano o projeto começa a sair do papel por meio da construção
de uma hidrelétrica no Pará.
Nessa edição a revista traz uma reportagem que aborda a licitação
da hidrelétrica São Luiz do Tapajós que será a primeira hidrelétrica a usar
esse conceito de usina.
A reportagem mostra os detalhes desse tipo de construção, os custos
e a capacidade de geração que se pretende obter com o empreendimento.
Over time, the great struggle between the entrepreneurs of hydropower plants and environmentalists has always been in relation to the impacts
that the construction of a hydropower plant causes in its implantation site.
Some time ago, Brazil began to study the concept of plant platforms
and various research projects were completed in this respect. The plant
platform was conceived with the intention to cause less human impact
on the environment.
And this year the project will come off paper through the construction
of a hydropower plant in Pará.
In this edition of the magazine, we feature a story that outlines the
bidding of the hydropower plant São Luiz do Tapajós, which will be the
first hydropower plant to use this factory conception.
The story shows the details of this type of construction, the costs and
the generation capacity to be achieved with the development.
Have a good read!
Boa leitura!
Apoio:
IAHR DIVISION I: HYDRAULICS
TECHNICAL COMMITTEE: HYDRAULIC MACHINERY AND SYSTEMS
4
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AGENDA/SCHEDULE
NEWS
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Technical Articles Seccion
TECHNICAL ARTICLES
SIMULATION OF THE TURBINES TRANSIENT OPERATION USING THE ALLEVI PROGRAM ............................................................. 8
Vicent B. Espert Alemany, Edmundo Koelle, Javier Soriano Olivares, Enrique Cabrera Marcet
THE CORROSIVE POWER OF GOLDEN MUSSEL (L. FORTUNEI) MACROFOULING ON STEEL STRUCTURESG.....................................14
Flavio Sandro Lays Cassino, Paulo Henrique Vieira Magalhães, Vicente Braz Trindade, Júnia Ananias
ARTIGOS TÉCNICOS
TURBINE BUILT WITH SYMMETRICAL PROFILE BLADES, LIKE TYPE WELLS TURBINE, FOR USE IN TIDAL POWER PLANTS ...............19
Prof. Dr. Geraldo Lucio Tiago Filho, Eng. Antonio Carlos Barkett Botan, Thiago Oliveira, Profa. Regina Mambeli Barros
PERFORMANCE ANALYSIS THROUGH COMPUTATIONAL FLUID DYNAMICS OF AXIAL ROTOR WITH
SYMMETRIC BLADES USED IN TUNNELVENTILATION..............................................................................................................22
Angie Lizeth Espinosa Sarmiento, Yina Faizully Quintero Gamboa, Waldir de Oliveira, Ramiro Gustavo Ramirez Camacho
IAHR DIVISION I: HYDRAULICS
TECHNICAL COMMITTEE: HYDRAULIC MACHINERY AND SYSTEMS
Classificação Qualis/Capes
B5
B4
ENGENHARIAS I; III e IV
Biodiversidade
Interdisciplinar
Áreas de: Recursos Hídricos
Meio Ambiente
Energias Renováveis
e não Renováveis
A revista está indexada no DOI sob o prefixo 10.14268
7
7
SIMULATION OF THE TURBINES TRANSIENT
OPERATION USING THE ALLEVI PROGRAM
Vicent B. Espert Alemany
2
Edmundo Koelle
3
Javier Soriano Olivares
4
Enrique Cabrera Marcet
1
ABSTRACT
When designing hydroelectric power plants it is fundamental to simulate the system behavior in unsteady conditions following a total
load rejection. The main objective of this simulation is to define wicket gates closure laws that allow the system to meet certain design
specifications. To carry out this simulation the turbine characteristic curves should be used, which are obtained from the hill diagrams
of turbines geometrically similar to those to be installed. The Allievi program can be used to carry out this simulation, extrapolating
the turbine hill diagram beyond the area covered by the available data. In this paper the simulation of three Francis turbines total load
rejection is presented, showing the capabilities of the program and its possibilities to be used in hydropower projects.
KEYWORDS: Hydraulic transients, Hydraulic turbines, Turbine hill diagrams, Simulation.
1. INTRODUCTION
When designing a hydroelectric power plant the choice of
type, diameter and rotation speed of the turbines to be installed
is carried out from different parameters such as the total head,
the available flow rate and the power that is wanted to obtain.
For this choice there turns out to be fundamental the knowledge
of the turbine hill diagrams [1]. From these curves, and using
the affinity laws, it is possible to know the behavior of the above
mentioned turbines in different operation conditions.
Once the turbines have been chosen, the maximum overpressure produced when the wicket gates close after a total load rejection can be evaluated by means of the Michaud’s equation,
admitting that the closing time is greater than the time characteristic of the penstock [2]. At the same time, the maximum
overspeed reached by the turbines after the total load rejection
is estimated using certain semiempirical expressions available in
the literature [1, 3].
After these calculations, the designed system must be simulated in transient flow, in order to ratify the previous results or to
modify the characteristics of the system when the results of the
simulation advise it. To carry out this simulation the characteristic curves of the turbines have to be used. These characteristic
curves are obtained from the hill diagram of the series of turbines
geometrically similar to those candidates to be installed.
In general, the hill diagrams do not provide enough information to simulate the behavior of the turbines after the total
load rejection. This is because this diagram only includes a zone
of the plane N11 - Q11 in the vicinity of the best efficiency point
where the turbines must be operated under steady state conditions. In the case of the total load rejection, and while the wicket
gates are closing, the runners increase their rotation speed until
a maximum value, after which it decreases until full stop. This
behavior will make the operating point of the turbines to move
initially within the hill diagram, leaving the area represented by
the diagram when the turbine operating conditions exceed certain limits.
It can be seen that the hill diagrams do not provide enough
information to simulate the behavior of the turbines after a total load rejection. A possible solution is to use turbine universal
curves such as the Suter curves, but these curves have been
ITA, UPV (Valencia,
Koelle Engineering.
ITA, UPV (Valencia,
4
ITA, UPV (Valencia,
1
2
3
8
elaborated only for turbines of 0.82 rad/s specific speed [4]. The
Allievi program for calculation and simulation of hydraulic transients provides a solution to this problem. This program, which
includes in its formulation the operation of commercial turbines
in transient flow, extrapolates the hill diagrams beyond the area
covered by the available data. In this way the behavior of turbines can be simulated as realistically as possible until the complete closure of the wicket gates. Using this extrapolation the results obtained are considered to be acceptable because they are
the only ones that can be obtained with the available information.
2. CHARACTERISTIC CURVES OF COMMERCIAL TURBINES
The characteristic curves of a turbine define its behavior under any operating conditions. These curves relate different operation parameters, while others remain constant. For Francis
turbines the parameters that can be defined are the runner diameter (Dt), the turbine flow (Qt), the net height (Hn), the power
in the turbine shaft (Pt), the efficiency (ηt), the shaft torque (Mt),
the rotation speed (Nt) and the opening of the wicket gates (α).
In Kaplan turbines this relationship is completed with the runner
blade angle (β).
As the characteristic curves relate two of these parameters when others remain constant, for example Qt = Qt(Nt) with
α = constant or Pt = Pt(α) when Nt = constant in the case of a Francis turbine, the amount of characteristic curves to handle is important, especially when the most suitable turbine to be installed in a
certain system is chosen. For this reason the usual procedure is to
use the hill diagram, which is obtained testing the model turbine
or simulating its behavior through CFDs. For each operating point
of the model turbine, obtained by test or simulation, different unit
values can be defined using the affinity expressions
(1)
By definition, the unit values are the values expected from a
turbine geometrically similar to the model, of 1 m diameter, subject to 1 m net head, and in an operating point similar to the best
efficiency point of the model turbine [5]. The curves obtained
from the unit values forms the hill diagram and, within the limits
imposed by the affinity theory, this diagram is the same for any
Spain), e-mail: [email protected]
(SP, Brazil), e-mail: [email protected]
HIDRO&HYDRO: PCH NOTÍCIAS & SHP NEWS, 60 (1), JAN,FEV,MAR/2014, DA PÁG. 08-13
TECHNICAL ARTICLES
turbine geometrically similar to the model.
Fig. 1 shows the hill diagram obtained testing a 460 mm Francis turbine model, and Fig. 2 shows the Hn = Hn (Qt) characteristic
curves for a geometrically similar 800 mm turbine at 720 rpm
rotation speed. Fig. 2 has been obtained applying relations (1)
to the values from Fig. 1 for different wicket gate openings α. In
the same way other characteristic curves, such as Pt = Pt (Qt) and
ηt = ηt(Qt), can be obtained for the same wicket gate openings.
tion is derived using the (N11ij, Q11ij) pairs, obtaining
Q11i = Aai + Bai · N11
• Quadratic regression equations without constant term
are derived using the (αi, Aai) and (αi, Bai) pairs, yielding
Aa = Bb · α + Cb · α2 and Ba = Bc · α + Cc · α2
Following this procedure, the linear regression equation is as
follows:
(3)
which provides null flow rate when the wicket gates are closed
(α = 0).
Applying a similar procedure to the unit torque values M11ij
(instead of Q11ij), a linear regression equation M11 = Ad(α) + Bd(α)
· N11 are obtained. In this case the next two variations are considered:
• From the linear regression equations M11i = Adi + Bdi · N11
obtained in the first step, in the second step quadratic regression equations with constant term are derived, using the (αi,
Adi) and (αi, Bdi) pairs. These quadratic equations are Ad = Ae
+ Be · α + Ce · α2 and Bd = Af + Bf · α + Cf · α2
• For the second step a linear regression equation will be derived for Ad (and/or for Bd) if its coefficient of determination is
higher than in the quadratic regression equation
In this case the linear regression equation is:
Fig. 1: Hill diagram for a serie of Francis turbines.
(4)
which should provide negative torque when the wicket gates
are closed (α = 0) and the runner has positive rotation speed
(N11 > 0).
4. THE ALLIEVI PROGRAM
Fig. 2: Hn = Hn(Qt) curves for a 800 mm Francis turbine at 720 rpm rotation speed.
3. EXTRAPOLATION OF TURBINE HILL DIAGRAMS
The characteristic curves shown in Fig. 2 highlight the limitations that appear when attempting to use the information contained in the hill diagram, Fig. 1, to simulate the behavior of a
turbine in unsteady state conditions. The information available is
limited to efficiencies equal or higher than 76 %, with wicket gate
openings between 14 and 34 degrees. To overcome these limitations the Allievi program extrapolates the hill diagram beyond the
area covered by the data available.
To generate the extrapolation functions nα wicket gate openings are available in the hill diagram. For the wicket gates opening i, of value αi, ηi points are defined so that for the point j of the
opening i the parameters N11ij, Q11ij and ηij can be read from the
hill diagram. With these values the corresponding unit torque can
be calculates through the relationship
(2)
Then a linear regression equation Q11 = Aa(α) + Ba(α) · N11
whose coefficients depend on α is defined in the following way:
• For each wicket gates opening i a linear regression equa-
The ALLIEVI program has been used to simulate the transient
flow of the case of study. This program simulates the transient
state operation of a hydraulic system, which can comprise both a
single pipeline as well as complex systems made up of branched
or looped networks.
In a pipeline, hydraulic transient modeling is performed by
applying the mass and momentum conservation equation to a
control volume that includes the pressure wave flowing through
the pipe. This allows for a two non-linear differential equations
with two unknowns set, i.e. piezometric head H = H(x, t) and
flow rate Q = Q(x, t), both unknowns depending of the coordinate
along the pipeline and of the time [6, 7].
As this equations set has no analytical solution, the usual procedure followed is to assume that the solution will be obtained at
certain time instants (separated by Dt) and at specific points along
the pipeline (separated by Dx), in order to meet the condition
(5)
where a is the pipeline wavespeed. In the case of water, this
wavespeed is calculated by means of the equation
(6)
in which the coefficient C depends on the pipe material.
Based on this assumption, the differential equations are
transformed into a system of two linear algebraic equations with
two unknowns, which can be used to calculate the piezometric
9
head H and the flow rate Q at point i of the pipeline and at the
instant n + 1, based on the values of H and Q of the points i - 1
and i + 1 at the instant n. This algorithm is known as method of
the characteristics, and is the calculation method on which the
Allievi program is formulated.
The algebraic equations can be solved for all the calculation
points of any pipeline except at its ends, where one of the two
equations does not exist. At these ends, where it is assumed
that the pipeline is connected with a system element, the equation which is lacking is replaced by the equation or set of equations representing the behavior of the element, which are called
boundary conditions. Thus, the Allievi program allows for the
simulation of the transient flow operation of a hydraulic system
including the following elements:
provides the best efficiency point). Neglecting minor losses the
steady-state conditions, calculated using the Allievi program, are
as follows:
•
•
•
•
•
Given the system data and the initial conditions detailed above,
the transient behavior of the system was simulated following the
total load rejection of the generators. For the different simulations
carried out a calculation time of 100 s was used, with a time-step
size of 0.01 s. With this time step, at least two calculation intervals
are achieved in the shorter pipes (the draft tubes DfTb1, DfTb2
and DfTb3). In all the cases the total load rejection happened at
the moment the simulation was started, and different wicket gate
closing laws were used to check their effect on the resulting maximum overpressure and overspeed values.
Reservoirs, with or without spillways
Pumping stations
Turbines
Valves or minor losses
Protection systems, consisting of air vessels, surge tanks or
unidirectional tanks
• Air valves
• Flow or head laws at the end of a pipeline
In a hydraulic system the transient flow results from a change
in one of the system elements leading to the alteration of steady
state operation. In the Allievi program, steady state is obtained
by processing the calculation of transient state under any given
operating condition, where the system elements are in their original position and no changes have been made. When this calculation leads to steady state conditions, these conditions are taken
as initial values for transient calculations.
5. CASE OF STUDY: HYDROELECTRIC POWER PLANT
WITH THREE FRANCIS TURBINES
As a case of study the transient operation of a hydroelectric
power plant equipped with a penstock feeding three Francis turbines will be simulated. The objective of this simulation is to calculate the maximum overpressure and overspeed to be produced
in the turbines after a total load rejection followed by the wicket
gates closure with different closure laws.
Fig. 3 shows the system diagram for this case, including the
data used in the simulation. The turbines have 800 mm diameter,
and their nominal rotation speed is 720 rpm. The hill diagram
of these turbines is that shown in Fig. 1, with the characteristic
curves shown in Fig. 2.
• Static head: 650 – 570 = 80 m
• Total flow: 16.60 m3/s
• Water speed in the first stretch of the penstock (PenSt1):
2.35 m/s
• Water speed in the second stretch of the penstock (PenSt2):
3.38 m/s
• Turbine flow: 5.53 m3/s
• Turbine inlet pressure (N04, N06 and N08 nodes): 83.60 mwc
• Net head in each turbine: 78.59 m
• Power in the turbine shaft: 3.78 MW
• Efficiency of each turbine: 88.53 %
5.1.Total load rejection. Linear closure of the wicket gates
The first case relates to the linear closure of the wicket gates
in 5 s after the total load rejection. A summary of the results
obtained is shown in Fig. 4 to 7, from which the following conclusions can be drawn:
Fig. 4. The maximum and minimum piezometric head envelope
in the two stretches of the penstock (PenSt1 and PenSt2) and in the
turbine inlet branch (FPpT1) are shown. In the simulated closure it
can be observed negative pressure in some parts of these pipes.
Fig. 5. Pressure evolution at the turbine inlet (node N04). The
pressure increases due to the reduction in the flow when the wicket
gates start to close, up to the point at which the wicket gates get
closed within 5 s. After that, transient flow develops between the
upper reservoir and the closed wicket gates (without affecting the
turbine runner), giving rise to the pressure oscillations observed in
Fig. 5. The maximum pressure at the turbine inlet is 176.67 mwc,
and the minimum pressure -5.89 mwc.
Fig. 3: System diagram to simulate its transient operation using the Allievi
program.
To carry out the simulations it will be assumed that under
steady-state conditions the three turbines are in operation, with
a wicket gates opening of 24 degrees (value very close to which
10
Fig. 4: Maximum and minimum head envelop in the penstock up to the
turbine inlet. Linear closure of the wicket gates in 5 s.
Fig. 5: Pressure evolution in the turbine inlet section. Linear closure of the
wicket gates in 5 s.
Fig. 7: Turbine operation points on the hill diagram. Linear closure of the
wicket gates in 5 s.
Fig. 6. Evolution of the turbine rotation speed in percentage
values. The rotation speed increases after the total load rejection. It can be observed that the maximum rotation speed happens at 4.1 s, before the end of the wicket gates closure. After
that, and until the complete closure of the wicket gates, the flow
in the turbine inlet is reduced so much that it can no longer maintain the rotation speed achieved. With the wicket gates already
closed, the runner continues to rotate by inertia and at a decreasing rotation speed, until it comes to a complete stop. The
maximum rotation speed reached is 135.02 % of the idle speed
(720 rpm), or 972. rpm.
Fig. 7. Evolution of the turbine operation point on the hill
diagram. As can be observed in this figure, until 2.10 s the operating point moves over the area of the hill diagram for which
data are available, and from this time it moves out of this area.
Therefore, in order to complete the calculation, the procedure
followed by the Allievi program is to define the hill diagram by
means of analytical equations to allow the behavior of the turbine to be simulated until the complete closure of the wicket
gates.
The conclusions that can be deduced from this simulation are
the following:
These values should be compared with the specifications imposed to this system. If at least one of them is higher than the
maximum imposed, for example the overpressure value, new
simulations should be done with higher closure time. The results
of these simulations are shown in Fig. 8, were it can be seen that
when the closure time increases, the overspeed increases and
the overpressure decreases.
Fig. 8 shows that in this system some specifications can’t be
met simultaneously with a linear closure law. It is the case, for
example, of 40 % for the maximum overpressure (closure time
higher than 10.75 s) and 50 % for the maximum overspeed (closure time lesser than 9.75 s). Consequently other closure laws
such as two step closure should be simulated in order to meet the
specifications. This is done in the next simulations.
• The overpressure reached at the turbine inlet is (176.67 83.60 )x100/83.60 = 111.3 %
• The overspeed reached is 35.02 %
5.2.Total load rejection. Two step closure of the wicket gates
The behavior of the system is simulated in the case of two
step wicket gates closure after the total load rejection. In this
case, if the initial opening of the wicket gate is 24º, in the first
step there is a linear closure until an opening of 7.2º (30 % of
the initial opening), and in the second step there is another linear
closure until the total closure.
Fig. 8: Maximum overpressure and maximum overspeed for different time
closing of the wicket gates in a linear closing law.
Fig. 6: Evolution of the turbine rotation speed. Linear closure of the wicket
gates in 5 s.
Assuming that the duration of the second step is 1.5 times the
duration of the first step (i. e., 6 s for the first step and 9 s for
the second step, in total 15 s), Fig. 9 shows the overpressure and
overspeed obtained with a first step duration between 4 and 10 s
(10 to 25 s for total closure duration). In this figure it can be seen
that to obtain an overpressure less than 40 % and an overspeed
11
ARTIGOS TÉCNICOS
less than 50 %, the first step duration ranges between 6.5 and
6.8 s (total duration between 16.25 and 17.0 s)
Fig. 9: Maximum overpressure and maximum overspeed for different first
step time closing of the wicket gates in a two step closing law.
It has been simulated the total load rejection with two step
wicket gates closure of 6.67 s for the first step and 10.0 s for the
second step (in total, 16.67 s). The results obtained are summarized in Fig. 10 to 13, from which the following conclusions
can be drawn:
Fig. 12: Evolution of the turbine rotation speed. Two step closure of the
wicket gates in 16.67 s.
Fig. 10. Negative pressures have not been developed along
the pipes. The distances between the piezometric head envelopes
and the pipeline indicate that it is not necessary to install protection devices.
Fig. 11. The maximum pressure at the turbine inlet is 115.77
mwc, and occurs at the end of the first step. The maximum overpressure is (115.77 - 83.60 )x100/83.60 = 38.5 %. The minimum pressure at the turbine inlet is 76.30 mwc.
Fig. 13: Turbine operation points on the hill diagram. Two step closure of
the wicket gates in 16.67 s. Hill diagram defined by analytical functions.
Fig. 10: Maximum and minimum head envelop in the penstock up to the
turbine inlet. Two step closure of the wicket gates in 16.67 s.
Fig. 14: Turbine operation points on the hill diagram. Two step closure of
the wicket gates in 16.67 s. Hill diagram defined by the available data.
Fig. 11: Pressure evolution in the turbine inlet section. Two step closure of
the wicket gates in 16.67 s.
12
Fig. 12. The maximum rotation speed occurs at 7.5 s, less than
1 s after the beginning of the second step, being 149.68 % of the
idle speed. In this case the maximum overspeed is 49.68 %.
Fig. 13. Until 4.05 s the operating point moves over the area
of the hill diagram for which data are available, and from this
time it moves out of this area. It can be seen clearly the end of
TECHNICAL ARTICLES
the first step (6.67 s) and the end of the inlet descending pressure period (8.80 s, Fig. 11).
It has been also simulated the total load rejection with the
same two step closure law, but using for the calculation the hill
diagram data available (without defining the hill diagram by
means of analytical functions). Fig. 14 shows that the turbine
operation point on the hill diagram moves out of this area at the
instant 3.98 s, from which the calculation cannot go on
Comparing Fig. 13 and 14 until approximately 4 s it can be
concluded that the results obtained with the hill diagram defined
by the available data and by analytical functions are practically
the same. This fact validates the use of the hill diagram defined
by the analytical functions presented in the paragraph 3.
rejection. These maximum values depending of the wicket
gate closing law to be implemented
• In general, if the closing time increases the maximum overpressure decreases and the maximum overspeed increases.
Beside, two step closing laws produce better results than one
step ones. Therefore, only the simulation allows knowing the
most suitable closing law
• The results obtained simulating the turbines behavior with
the hill diagram defined by the available data or by analytical
functions are practically the same. This fact justifies the use
of extrapolated hill diagrams to simulate the turbines behavior up to the complete closure of the wicket gates.
7. REFERENCES
6. CONCLUSIONS
In this paper the unsteady behavior of a hydropower system
after its total load rejection is simulated. To carry out this simulation the characteristic curves of the turbines are required, curves
that are obtained from the hill diagram of those turbines. But the
hill diagrams include only turbine operation points in the vicinity
of the maximum efficiency point. By this reason, for a correct
simulation it is needed to extrapolate the hill diagram up to the
complete closing of the wicket gates.
Having presented a case of study with three Francis turbines
in which a total load rejection happens when the system is operating in nominal conditions, it can be obtained the next conclusions:
• The Allievi program is able to simulate the transient flow of a
hydropower system after a total load rejection
• The results of the simulation allow knowing the maximum
overpressure and overspeed in the turbines after a total load
• [1] Bureau of Reclamation, 1976. “A Water Resources Technical Publication. Engineering Monograph No. 20”. U.S. Department of Interior
• [2] Abreu, J; Cabrera, R.; Espert, V.B.; García-Serra, J.;
Sanz, F., 2012. “Transitorios Hidráulicos. Del Régimen Estacionario al Golpe de Ariete”. Ed. Universidad Politécnica de Valencia
• [3] Ilyinykh, I.I., 1982. “Hydroelectric Stations”. Mir Publishers. Moscow
• [4] Pena de Andrade, J.G., 1994. “Análise e otimização da
operação de usinas hidroelétricas”. Ph. D. Thesis. Universidade Estadual de Campinas (São Paulo)
• [5] Mataix, C. ,1975. “Turbomáquinas hidráulicas”. Ed. ICAI.
Madrid
• [6] Wylie, E.B.; Streeter, V.L., 1982. “Fluid Transients”. Feb
Press. Ann Arbor (Michigan)
• [7] Thorley, A.R.D., 2004. “Fluid Transients in Pipeline Systems (2nd Ed.)”. Professional Engineering Publishing. London
ANOTAÇÕES
13
ARTIGOS TÉCNICOS
THE CORROSIVE POWER OF GOLDEN MUSSEL (L. FORTUNEI)
MACROFOULING ON STEEL STRUCTURESG
1
Flavio Sandro Lays Cassino
Paulo Henrique Vieira Magalhães
1
Vicente Braz Trindade
1
Júnia Ananias
2
ABSTRACT
Abstract In this study it was performed a detailed morphological-structural analysis of the corrosion products resulting from golden mussel (Limnoperna fortunei) macrofouling on steel structures. Scanning electron microscopy, without previous metallization of the observed
structures, was utilized in the study. With this analysis it was possible to build a new scenario for understanding this corrosion process,
as several important facts were observed. Firstly, the presence of at least three types of bacteria able to corrode metals was detected:
sulphate reducing bacteria, iron-depositing bacteria, and Fe3+ reducing anaerobic bacteria which produce ferrous hydroxy carbonate from
magnetite. The presence and proliferation of colonies of these micro-organisms can be in many ways favored by the dense mussel fouling. Also, the analysis of the cross-sectional structure of the corrosion layer allowed identifying the basic mechanism by which the metal
is consumed by the corrosion process.
KEYWORDS: morphological-structural analysis, golden mussel, micro-organisms
1. INTRODUCTION
Just after the first record, in late 1991, of the golden mussel
at Rio da Prata estuary in Argentina it was instantly recognized
the environmental threat that meant. Since then a number of
works related to the monitoring and the study of the multiple
risks and impacts that may result from the presence of this species on ecosystems and human activities in several countries in
South America [1].
In these nearly twenty years of research a huge amount
of knowledge has been accumulated about this case of
bio-invasion, both as regards the biological aspects, as the dynamics and strategies of this invasive species in their new habitat. And, even though in 2001 the presence of the Limnoperna
fortunei was already recorded in Brazil, Paraguay and Uruguay
[1], was such knowledge, combined with educational campaigns
and surveillance in all countries involved, which undoubtedly
avoided major disasters and allowed to keep the spread of the
golden mussel at a relatively slow rate of about 240 km / year.
Its presence in São Simão Dam, Rio Parnaíba, was detected only
around 2008 [2].
However, there is still much to do to achieve a position of
effective control of the ineradicable presence of the golden mussel in South America. In this direction, one of the important issues that must be analyzed refers to the apparent acceleration
of the corrosive degradation of steel structures when subject to
the golden mussel fouling. Combined with the various problems
caused by these mollusks, which have changed the routine of
operation and maintenance of hydroelectric power and water
catchment systems, this enhanced corrosion of steel structures
like pipes, floodgates, valves, heat exchangers, etc., besides representing economic loss, significantly increases the possibility of
risk situations the operation of the plants. Therefore, understand
the mechanisms of the corrosive action of the golden mussel
fouling and to know how quantify its corrosive power represent
key points to keep in service and to design the steel components
and parts that will be subject to periodic fouling.
The few works that were found addressing the corrosion
caused by golden mussel fouling, had their focus on the role
of the corrosive chemicals used to eliminate infestations; substances that are normally potent oxidants (chlorine gas, ozone,
chlorine dioxide etc.), and even used in low concentrations may
cause undesirable effects [6,7]. In these works, the unhindered
corrosion caused by fouling was taken as a control situation to
compare the results of the action of anti-fouling substances. The
conclusion to be drawn from these studies is that, during a given
time interval, any steel surface that remains infested seems to
degrade more rapidly than those in which the fouling has been
partially or completely eliminated by any chemical agent [6].
Given this conclusion it is becomes essential to find the answers
to several fundamental questions concerning the mechanisms
by which this intense corrosion process occurs. For example, although it has already been advanced that the most likely hypothesis to explain this accelerated corrosion process is the action
of anaerobic sulfate reducing bacteria (SRB), which could take
advantage of the anoxic environment in the fouling layer [8], between the works that were found none addressed this hypothesis
specifically. Further, the important issue of the mechanism by
which the corrosion front propagates in the steel structure was
not analyzed and there appears to be insufficient experimental
data to estimate the kinetics of this process.
Given this scenario, this paper presents a systematic attempt
to understand the main aspects that somehow are connected to
the corrosive action of the golden mussel fouling. In this first
stage, are reported the results of a detailed morphological study
of Limnoperna fortunei fouling, performed by Scanning Electron
Microscopy (SEM), together with the preliminary results of an
annual monitoring work in which a direct comparison is made
between the rate of corrosion of steel coupons exposed to golden
mussel infestation and the rate of corrosion equal coupons exposed to the same conditions as the firsts but free of fouling.
2. METHODOLOGY
The morphological and microstructural analysis was performed using scanning electron microscopy (SEM) without prior
metallization of the samples. In all three samples subjected to
Limnoperna fortunei incrustation in different conditions and for
different times, according to Table 1, were analyzed. The steel
used in this study is the low carbon steel A-36. Samples 1 and
2 were exposed to fouling at the Laboratório de Estudos do
Limnoperna fortunei of the Center of Hydraulic Research/UFMG
Departamento de Engenharia Metalúrgica e de Materiais, Escola de Minas – UFOP
Departamento de Engenharia de Controle e Automação, Escola de Minas – UFOP
1
2
14
TECHNICAL ARTICLES
(CPH/LELf/UFMG). Sample 3 was subjected to fouling in natural
conditions at the Itaipu Lake.
Table 1: Fouling conditions for the analyzed samples.
Sample (Area)
Fouling conditions
Fouling stage
sample 1 -10,0 X 3,0 cm2
in vitro
initial<1month
(biofilm without mussel)
sample 2 -10,0 X 3,0 cm2
in vitro
intermediate~6months
(with mussels)
sample 3 -12,0 X 10,0 cm2
natural conditions
advanced~12meses
(many mussels)
For the annual monitoring work which periodically compares
the corrosion rate of metallic coupons subjected to fouling in natural conditions with that of equal coupons submitted, except for
the fouling, to the same corrosive conditions, we used the following methodology: a set of PVC panels were prepared and in each
one were fixed, by nylon clamps, twelve A-36 steel coupons with
10 x 3 cm2, as in Figure 1 that shows a panel from which was
already withdrawn the first coupon.
Fig. 1: Model of the panels with
the arrangement of steel coupons
used for the corrosion tests. Inside the PVC pipes is placed a rod
of steel to avoid the tendency of
the assembly to floating.
Three of these panels were immersed in fresh water contaminated by Limnoperna fortunei in Itaipu Lake at the Portinho Biological Station. From this first set of coupons subject to fouling, one
coupon of each panel will be withdrawn every month to evaluate
the corrosion process in the presence of mussel.
Two other panels, immersed at points next to the first three
ones, were previously enwrapped by a network 40 micron of
mesh opening to keep the coupons surface inaccessible to the
mussel larvae, which are much larger with about 200 µm. This
second set of coupons will therefore be free of fouling, but it will
be under the same physico-chemical conditions and, except by
the mollusks, almost the same biological conditions of the first
set; since these coupons are protected against macrofouling by
the network, the biofilm that will grow over their surfaces will be
same as if the water were not contaminated with the golden mussel. This methodology will allow qualifying and quantifying the
exact role of the presence of the golden mussel on the kinetics of
the corrosion process of metal surface.
This work presents one analysis of the corrosion coupons by
means of a morphological study of the corrosion products. Analyzes were made of the sample surfaces and cross sections.
Results and Discussion
Figure 2 shows the macroscopic state of the three analyzed
samples. On the sample 1 surface a biofilm was formed with the
presence of bacteria, algae and, possibly, other micro-organisms,
but there were no time to fixing and development of mussel larvae. It can be observed that the corrosion process on this sample
produced small areas with slight variations of light/dark (or, less
corroded/more corroded) uniformly distributed over its entire
surface, which may be related to the distribution of areas preferentially cathodic or anodic that were formed at the early stages
of the corrosion process.
On sample 2, the mussel could reach up to 30 mm, but in
small amount of individuals; the corroded surface has a more
uneven appearance with the thickness of the corrosion products
varying widely from region to region of the surface.
On sample 3 a severe corrosion process produced a thick
layer of corrosion products that developed simultaneously to a
dense mussel fouling. In a detail of this sample shown in Figure
3, it can be seen that the thickness of the corrosion layer is much
greater than that of the remaining metal sheet (at least 3 times
the thickness of the plate).
Fig. 2: The fouling stages of the analyzed samples. Sample (1) without
mussel, sample (2) with mussels grown in vitro for 6 months, sample (3)
fouling developed in field conditions for 12 months.
Fig. 3: Detail of sample 3 where the layer of corrosion products is viewed
in profile. There is a complex surface topography and a tendency to stratifications parallel to the metal surface, some fractures parallel and perpendicular to the stratification can also be seen.
Figure 4 shows images obtained by SEM, without prior metallization, of some morphological and microstructural features of
the corrosion process at the surface of sample 1. It can be seen
that even in the absence of mussel fouling, corrosion influenced
by the aquatic micro-organisms is already an aggressive process
which produces various corrosion products with different morphologies. The presence of fracture systems at various scales
shows the great fragility of the corrosion layer (Fig. 4c and 4d).
Figure 4a shows some globular structures with sizes between 3
and 15μm, on the larger ones many cracks can be seen (Fig. 4d).
These structures appear to be the result of the growth and
the coalescence of small tubercles, shown in Figure 5, typical of
the action of iron bacteria, also called iron-depositing bacteria
that produce reddish-orange deposits of iron oxides and iron hy-
15
droxides. The regions colonized by this type of bacteria are transitional zones where the deoxygenated water from an anaerobic
environment flows into an aerobic medium, exactly the situation that should be created within these tubercles [9]. Figure 4c
shows a morphology of crystals in needles and thin plates typical
of lepidocrocite (Fe3+O(OH)), which is dimorphous with goethite
[10]. These two iron-oxyhidroxides are the major components of
the corrosion products.
rust), a corrosion product characteristic of the action of sulphate
reducing bacteria (SRB). The outermost layer (layer 3), shown at
large amplification in Figure 7d, presents globular shapes and tubercles similar to those observed on sample 1, the observed morphology is typical of goethite. The surface separating the lower
strata from the intermediate one, shown in Figure 7b, is almost
flat and displays some fractures.
Fig. 5: Tubercle
shaped structures,
formed on sample
1, typical of the
action of iron-depositing bacteria.
Figure 6 shows images without metallization of morphological features of the corrosion products formed on the surface of
sample 2. It may be noted that the outer surface has a rough
appearance, showing fractures and pores of the corrosion layer
(Fig. 6a). Figure 6b shows the presence of diatoms in the fouling
biofilm.
Fig. 7: Morphology of the corrosion products formed on sample 2: (a) the
3-layer structure, (b) a magnified view of the second layer, (c) magnified
view of the first layer and (d) details of third layer.
Figure 8 shows the surface of the metal substrate (steel plate)
just after detachment of a fragment of the corrosion layer. Many
corrosion products remain adhered to the metal, a few crystals
have an acicular or thin lamellae morphology which is characteristic of ferrous hydroxy carbonate (Fe2(OH)2CO3), which is a
well-known biological decomposition product of magnetite by anaerobic bacteria [11], certainly this magnetite is present between
the corrosion products. Many fractures of the corrosion products
that are still adhered to the metal can be observed.
Fig. 6: Structural features of
the outer surface of the corrosion products layer on sample
2 and the presence of diatoms
in the biofilm fouling.
For the sample 2 it was possible to analyze the inner surface of the corrosion layer, the one which is in contact with the
metal substrate. For this purpose, a fragment of the corrosion
layer was carefully detached from the steel substrate, this also
allowed observing the structures on the metal surface after detaching the fragment of the corrosion layer. Figure 7 shows the
inner surface of the corrosion layer. As the fragmentation of the
scale did not occur on the same plane, it can be clearly observed
the existence of three distinct layers suggesting the formation of
different corrosion products (see Figure 7a). The bottom layer
(layer 1), which is in contact with the steel substrate, is formed
mainly by hexagonal crystals (see Figure 7c), with the typical
morphology of the Fe(III) hydroxy sulphate Fe(OH)SO4 (green
16
Fig. 8: Surface of the
metallic substrate observed just after detachment of a fragment
of the corrosion layer.
Many corrosion products
remain adhered to the
metal surface.
Sample 2 was also used to perform the analysis of the cross
section of the corrosion layer and of the steel substrate, what is
shown in Figure 9. It can be observed the formation of various
corrosion products along the cross section of the layer, and it can
be clearly seen the existence of the three layers of major corrosion products (see Figure 9a and 9b).
Fig. 9: The analysis of the cross section of the sample 2: (a) layer of corrosion, (b) formation of various layers of corrosion products , (c) corrosion
inicial stage – steel attack and (d) degradation of the steel substrate after
the stage described in (c).
Analyses of the sample 3 are shown in Figure 10. It was possible to analyze by Scanning Electron Microscopy (SEM) the surface of the valves of mussels encrusted without prior metallization. The Figure 10a shows that the entire surface of the valve
is covered with various corrosion products, some very similar to
those found in the samples 1 and 2. The Figure 10b shows a thin
layer, probably formed from iron oxides and hydroxides, locally
damaged revealing the valve surface. Diatoms in fouling biofilm
were observed as shown in Figure 10 c. In Figure 10 d is shown
the mussel byssus fixed on the valve from another mussel. It is
observed that the byssus also begins to be covered with corrosion products.
eration of corrosive metal degradation appears to be a synergic
action of several types of microorganisms, particularly aerobic
and anaerobic bacteria, whose proliferation can be facilitated
by the presence of the mussel through several ways. The initial
process of the attack on the metal surface can be clearly evidenced through the observations of samples cross sections. This
is particularly important for the means of protection used by engineering, which eventually can be employed as a barrier against
fouling, and to choose the best systems of removal and fouling
control. However more research for a better understanding of
the mechanisms of nucleation and growth of corrosion products
need to be carried out through the chemical characterization of
corrosion products and determination of the kinetics of the corrosive process.
Regarding the work of annual monitoring of corrosion rates of
encrusted surfaces under natural conditions, which is in the initial
stage of progress, the preliminary results of the first samples,
taken from the panels that were submerged, show that even
free of fouling, the corrosion process of coupons is already at an
advanced stage (see Figure 11). This process generates a typical ferruginous mud resulting from the action of iron-depositing
bacteria.
Fig. 11: State of the first steel coupons
removed from panels immersed in the
Itaipu Lake after a month of immersion. The ferruginous mud can indicate
the action of iron-depositing bacteria.
3. CONCLUSIONS
The morphological analysis of metal corrosion process associated with fouling Limnoperna fortunei allowed understanding the
basic mechanisms of the corrosive process. Important facts might
be observed, such as the possible joint and synergetic action of
at least three types of bacteria: sulphate reducing bacteria, irondepositing bacteria, and Fe3+ reducing anaerobic bacteria which
produce ferrous hydroxy carbonate from magnetite. The presence and proliferation of colonies of these micro-organisms can
be in many ways favored by the dense golden mussel fouling.
The analysis of the cross-sectional structure of the corrosion
layer allowed identifying the basic mechanism by which the metal
is consumed by the corrosion process. This process leads to the
formation of a region of internal corrosion with subsequent deterioration of the metal, characterized by the detachment of parts
thereof, until its complete corrosion.
Acknowledgments
We thank FAPEMIG and VALE for supporting Network for Advanced Studies in Limnoperna fortunei (REALf) and the ITAIPÚ
Binational in the person of Dr. Domingo Fernandez.
Fig. 10: Analyses of the mussels valves encrusted in the sample 3 covered
of corrosion products.
The results of this morphological analysis of steel surfaces
corrosion subject to fouling of Limnoperna fortunei shows that it
is a highly complex process. The main responsible for the accel-
4. REFERENCES
• [1] Gustavo Darrigran, in Monitoring and Control of Macrofouling Mollusks in Fresh Water Sysrems, Gerald L. Mackie
and Renata Claudi, Editors, 2nd Ed. CRC Press, 2010.
17
• [2] Maria Edith Rolla e Hélen Regina Mota, in Monitoring and
Control of Macrofouling Mollusks in Fresh Water Sysrems,
Gerald L. Mackie and Renata Claudi, Editors, 2nd Ed. CRC
Press, 2010.
• [3] Brenda J. Little, Jason S. Lee, Microbiologically Influenced
Corrosion, John Wiley and Sons, 2007.
• [4] Reza Javaherdashti, Microbiologically Influenced Corrosion - An Engineering Insight, Springer -Verlag, 2008.
• [5] Thomas R. Jack, Biological Corrosion Failures, 2002 ASM
International, ASM Handbook Volume 11: Failure Analysis
and Prevention, 2002.
• [6] Otto Samuel Mäder Netto, Controle da Incrustação de Organismos Invasores em Materiais de Sistema de Resfriamento
de Usinas Hidrelétricas, Dissertação de Mestrado, Programa de
Pós-Graduação em Engenharia e Ciência dos Materias, PIPE
Universidade Federal do Paraná, 2011.
• [7] Edemir Luiz Kowalski, Silmara Carvalho Kowalski, Revisão
Sobre os Métodos de Controle do Mexilhão Dourado em Tubulações, Revista Produção On Line, vol. 8, Num. 2, julho 2008.
• [8] Mata, F.A.R.; Dias, C.A.; Patrício, F.C.; Rolla, M.E., Carvalho, M.D.; Freitas, L.C. 2008. Avaliação da eficiência da substância MXD-100 na prevenção de incrustação e corrosão, por
lama ferruginosa, nos trocadores de calor tipo placa, da usina
de Nova Ponte (CEMIG/MG). III Seminário Brasileiro de Meio
Ambiente e Responsabilidade Social no Setor Elétrico.
• [9] Microbiolocally Influenced Corrosion, B. J. Little, J. S. Lee,
John Wiley and Sons, Inc., Publication, 2007.
• [10] ANTUNES, Renato Altobelli; COSTA, Isolda and FARIA,
Dalva Lúcia Araújo de. Characterization of corrosion products
formed on steels in the first months of atmospheric exposure.
Mat. Res. [online]. 2003, vol.6, n.3.
• [11] Kukkadapu, Ravi K.; Zachara, John M.; Fredrickson,
James K.; Kennedy, David W.; Dohnalkova, Alice C.; and
Mccready, David E., "Ferrous hydroxy carbonate is a stable
transformation product of biogenic magnetite" (2005). US
Department of Energy Publications. Paper 139.
ANOTAÇÕES
18
TURBINE BUILT WITH SYMMETRICAL PROFILE BLADES,
LIKE TYPE WELLS TURBINE, FOR USE IN TIDAL POWER PLANTS
Prof. Dr. Geraldo Lucio Tiago Filho
Eng. Antonio Carlos Barkett Botan
3
Thiago Oliveira
4
Profa. Regina Mambeli Barros
1
2
ABSTRACT
With the increasing of society’s concern about the environment, several alternatives to obtain electricity using natural means without
harm it has been studied. As the tides movement is a natural cyclical movement, it becomes a source of renewable energy, which has
been widely utilized for power generation over the years. The turbines with type Wells rotor are turbines with self-rectifying characteristics and with fixed geometry of the blades. The main characteristic of this type of rotor is to allow flow in both directions. For this
reason, these turbines have been indicated to be used for the energy extraction on oscillating water column (OWC) wave power plants
to convert pneumatic energy into mechanical energy of rotation. An example of the use of the Wells turbine widely cited is the Pico’s
eave power plant, in the archipelago of the Azores in Portugal. This research aims to study the viability of using this type of turbine
operating with water in tidal power plants.
KEYWORDS: Wells turbine, tidal power, renewable energy.
1. INTRODUCTION
C
Tidal Power
Due tidal energy is a clean energy and renewable source, and
with comparable costs to a hydropower plant (Ferreira, 2007),
has been an electric energy source well utilized, even thou with a
few sites available for its extraction in the World. It is about the
energy obtained by the movement of the water masses, where
the potential power is obtained by the head of the tides and the
kinect power obtained by the stemming currents.
The potential tidal power can be exploited on single way operation (single cycle operation) or on two-way operation (double
cycle operation). For this study, it’s considered the case of twoway operation.
Fig. 2: Schemes of Wells turbine: (a) rotor overview (Raghunathan, 1995);
(b) Wells turbine with guide vanes (Darabi and Poriavali, 2007); (c) Wells
turbine with variable pitch blades (García, 2008).
Developed by the Professor Alan Arthur Wells, the turbine
which was named after him has self-rectifying characteristics
keeps the rotation movement on the same way, independent of
the direction of the flow because the symmetric shape of the
blades. The Wells turbine are commonly used in devices for exploitation of wave energy like Oscillating Water Column (OWC)
for the conversion of pneumatic energy to mechanic energy of
rotation.
2. THE ROTOR DEVELOPMENT
The Model
Fig. 1.1: Single cycle operation of
a tidal plant (Jog, 1989).
Fig. 1.2 – Double cycle operation
of a tidal plant (Jog, 1989).
The Wells Turbine
A
B
It was developed for this study a rotor with symmetric blades
in NACA 0015 profile. The group of study had datas for the drag
and lift coefficients for this model, so it made the forces calculations possible. All the calculations were based on works of Raghunathan (1995), Souza (1991), Macintyre (1983) and Setogushi
et al (2003).
The internal diameter Di (m), or the hub diameter, is given by
the relation rc = Di/De, when is recommended to use the value of
rc = 0.6, due it has established a bigger efficiency in comparison
with other values already studied (Raghunathan,1995), but it not
delimits studies about the variation of this value.
The quantity of blades that constitutes the rotor, although
some studies suggest the number of 6, is a value related to the
blade length and the solidity factor of the turbine. The solidity
factor ς is given by the equation 1, and is a mutual interference
measure between the blades, which blocks the flow inside the
Diretor do Instituto de Recursos Naturais – IRN, Universidade Federal de Itajubá
Mestrando em Engenharia de Energia, Universidade Federal de Itajubá
Graduando em Engenharia Mecânica, Universidade Federal de Itajubá
4
Pesquisadora CERPCH
1
2
3
19
turbine. An increase on the solidity has a negative effect on the
efficiency, caused by an increase on the losses of kinetic energy
on the output.
(1)
Eq. 1: Solidity Factor ς
Where:
z = quantity of blades;
c = chord lenght of the blades (m);
rc = hub to the tip ratio.
The symmetrical blades developed for this study have NACA00xx profile. NACA profiles were developed by National Advisory
Committee for Aeronautics, and for this study, and its calculation
is given on equation 2:
(2)
Eq. 2: NACA-00xx profile equation.
Where:
c = chord lenght (m);
x = position from 0 until the chord lenght c;
y = value of the thickness in function of x (from the center
line until the surface);
t = maximum thickness given by the fraction of the chord (the
last two numbers of NACA profile divided by 100).
Fig. 5: Velocity triangles on the outlet represented for the rotor hub diameter (a), rotor medium diameter (b) and rotor tip diameter (c).
The rotor developed for this study has an inclination α of 13
degrees, combined with the guide vanes. This is combination is
result of a study which were considered the drag and lift forces,
and the study of the velocity triangles.
It was considered to fix a parameter for a constant rotation,
where the tangential velocity varies across the blade length. The
variation of the angle and the chord of the blade and the variation
of the angle across the guide vanes length promotes stability on
the relative velocity on the inlet and on the outlet of the blade
(in this case, is considered the use of a stator). Figures 4 and
5 represent the velocity triangles on the blades across the hub
diameter, the medium diameter and the rotor tip diameter for the
inlet and outlet respectively.
4. CONCLUSION
Following the premise that this paper aims to introduce a
study on the use of tidal power turbines in Wells, and at this first
stage of developing the rotor was accomplished, it was concluded
that the option of using these turbines in water, changes are required on its configuration. The use of guide vanes and also to
change the angle of the blades are devices which tend to improve
the performance of the turbine.
Fig. 3: Rotor Wells shape proposed to this study.
3. RESULTS
Velocity Triangles
Fig. 6: Wells turbine with guide vanes and variable pitch blades. (A) high
tide flow (B) low tide flow.
5. REFERENCES
Fig. 4: Velociy triangles represented for the rotor hub diameter (a), rotor
medium diameter (b) and rotor tip diameter (c).
20
• DARABI, A. E PORIAVALI, P., 2007, Guide Vanes Effect of
Wells Turbine on OWC Wave Power Plant Operation, World
Congress of Engineering 2007 Vol.1, London, U.K.
• FERREIRA, R. M. S. A., 2007, Aproveitamento da Energia das
Marés – Estudo de Caso: Estuário do Bacanga, Dissertação
– UFRJ.
• GARCIA, B. P., 2008, Estudio de Una Turbina de Impulso Radial para el Aprovechamiento de la Energía del Oleaje, Tese de
Doutorado, Universidad de Valladolid.
• JOG, M. G., 1989, Hydro-Electric and Pumped Storage Plants.
John Willey & Sons.
• MACINTYRE, A. J., 1983, Máquinas Motrizes Hidraulicas, Guanabara Dois.
• RAGHUNATHAN, S., 1995, The Wells Air Turbine for Wave Energy Conversion, Prog. Aerospace Sci, Vol. 31.
• RODRIGUES, C. M. F., 2009, Projecto das Pás Directizes Fixas
de Uma Turbina Auto-Rectificadora de Acção para Aproveitamento da Energia das Ondas, Dissertação – Instituto Superior
Técnico, Universidade Técnica de Lisboa.
• SETOGUCHI, T., SANTHAKUMAR, S., TAKAO, M., KIM, T. H.,
Kaneko, K., 2003, A Modified Wells Turbine for Wave Energy
Conversion, Renewable Energy 28, Pergamon.
• SOUZA, Z., 1991, Dimensionamento de Máquinas de Fluxo,
Editora Edgard Blücher.
ANOTAÇÕES
21
PERFORMANCE ANALYSIS THROUGH COMPUTATIONAL FLUID DYNAMICS OF
AXIAL ROTOR WITH SYMMETRIC BLADES USED IN TUNNEL VENTILATION
PERFORMANCE ANALYSIS THROUGH COMPUTATIONAL FLUID DYNAMICS
OF AXIAL ROTOR WITH SYMMETRIC BLADES USED IN TUNNELVENTILATION
Angie Lizeth Espinosa Sarmiento
2
Yina Faizully Quintero Gamboa
3
Waldir de Oliveira
4
Ramiro Gustavo Ramirez Camacho
1
ABSTRACT
The main feature of a Reversible Jet Fan is to provide the same air flow and thrust in both directions of flow, keeping the maximum ratio
thrust-power to any power range of an electric motor. These conditions could be achieved with the use of a rotor formed by doublesymmetric airfoils, for example, an elliptical airfoil. This paper presents a rotor blade design of a reversible axial rotor of a jet fan usually
used for ventilation of road tunnels. The design is based on a methodology that uses a non-free vortex condition to solve the radial
equilibrium equation. This project was developed from certain data available in the literature of elliptical profiles arranged in linear cascades representing axial rotors, gotten by means of Computational Fluid Dynamics (CFD) tools. Moreover, the aerodynamic performance
characteristics of a reversible axial rotor were found both in the design point and outside of it for a specific rotation using Computational
Fluid Dynamics Methods by means of the commercial software Fluent®. Through numerical simulation results, it is possible to plot aerodynamic performance curves, total pressure, thrust and fan’s shaft power, which show good agreement in relation to the design data.
KEYWORDS: Reversible jet fan; Axial-flow fan; Rotor blade design; Non-free vortex; Computational Fluid Dynamic; Fan performance
curves.
1. INTRODUCTION
Jet fans are commonly used in road tunnel ventilation, in
relatively short lengths, usually less than 5 km. Banks of these
fans are installed on the roof of the tunnel, at certain intervals,
thereby producing an effective flow of air from one side of the
tunnel to the other.
By saving energy, jet fans operate when the air quality deteriorates enough to require the forced ventilation assistance. Jet
fans for longitudinal ventilation of road tunnels are fans of axial
type. The rotor of this type of fan has a low hub ratio (ratio between the inner diameter and the outer diameter of the rotor).
Generally, the hub ratio for this sort of rotor is in the range of
0,3 to 0,4. Consequently, these ones have high specific rotations
characterized by high flow rates and low pressures. The number
of blades of these rotors is usually between 6 and 12, depending on the performance characteristics and on the aerodynamic
noise required.
With the aim of varying the speed of the air jet, and accordingly the thrust produced by the fan, the blades are attached to
the hub of the rotor, so that the mounting angle can be adjusted
in the desired position.
Relative to the flow direction, jet fans are classified into
two types: unidirectional and bidirectional, the latter also being
known as reversible. The unidirectional type is most appropriate for the longitudinal tunnel’s ventilation in a single direction
of vehicular traffic; because its reversion (direction reversion of
rotation of the rotor) results in 50% to 60% of the thrust in the
direction of normal rotation. Each radial section, along the blades
of this type of fan is generally made with a curved airfoil having
different leading edge and leading trailing.
In the case of reversible jet fans, the blades are formed by
symmetrical profiles in all radial sections thereof. Such profiles
may have shape of "S" or any other shape without cambering
what present bidirectional symmetry (symmetry with respect to
the chord line and in relation to the line perpendicular to the mid-
Universidade
Universidade
Universidade
4
Universidade
1
2
3
22
Federal
Federal
Federal
Federal
de
de
de
de
Itajubá,
Itajubá,
Itajubá,
Itajubá,
Av.
Av.
Av.
Av.
BPS
BPS
BPS
BPS
1303,
1303,
1303,
1303,
Pinheirinho,
Pinheirinho,
Pinheirinho,
Pinheirinho,
Itajubá-MG,
Itajubá-MG,
Itajubá-MG,
Itajubá-MG,
Brazil,
Brazil,
Brazil,
Brazil,
e-mail:
e-mail:
e-mail:
e-mail:
line of the cord) as the elliptical profile. These geometric characteristics of the blade are responsible for the low performance and
thrusts compared with the unidirectional jet fans. Regarding the
reversible jet fans, there are few jobs available in the literature.
In the sequel, some relevant works are commented.
Köktürk (2005) presents an aerodynamic design methodology
for reversible axial fans. This methodology uses the results of cascades analyses of axial flow machine, through Computational Fluid
Dynamics (CFD), using the commercial software Fluent ®. All linear
cascades analyzed are formed by elliptical profiles with maximum
aspect ratio of 8% of the length of his chord. For each angle of attack,
the author varied incidence speed and blade spacing. In this study,
aerodynamic performance characteristics of axial rotor were also obtained, concluding that the maximum efficiency is not achieved at the
point of design, but at a point very close to it.
In the paper of Ballesteros et. al., 2002 was carried out a
numerical and experimental study of air circulation inside of a
reversible jet fan, whose rotor had blades formed with elliptical
profiles, to provide the same pressure in both directions of operation. In this analysis was used the commercial software Fluent ®.
In the experiments were obtained radial distributions of the static
pressure, total pressure and of the different velocity components
in different sections of the fan, agreeing numerical and experimental results. In this work the authors seek to obtain a tool to
facilitate the design and improve the development of new fans,
also observe the flow behavior in inaccessible areas in laboratory
tests. It is worth mentioning that the last two works were conducted by researchers at the University of Oviedo, Gijón, Spain.
In this city, is located the Zitron matrix, a leading manufacturer
of various types of fans.
Thus, the main objective of this paper is to analyze the aerodynamic performance characteristics of reversible axial-flow rotors of jet fan obtained in preliminary studies, in order to optimize this type of machine for certain operating conditions.
[email protected]
[email protected]
[email protected]
[email protected]
OF AXIAL ROTOR WITH SYMMETRIC BLADES USED IN TUNNEL VENTILATION
2. DESIGN METHODOLOGY
This section features, initially, the main geometric quantities
of the rotor. Next, the methodology of aerodynamic design for
the reversible axial rotor is presented.
2.1 Main geometrical quantities of the reversible axial rotor
To obtain the rotor flow, Q, is necessary to carry out an iterative procedure (Espinosa, et al., 2011) which is fixed outside
diameter of the rotor, De. Therefore, it must be checked if De
agrees with the axial rotors optimized for the set of values of
rotational speed, n, flow, Q and total pressure ΔpT corresponding
to the point of optimum performance (max) rotor. The diameter
De can be obtained by the coefficient diameter, δ, through of
Cordier type graphs that relate the lightness coefficient, σ, whit
δ, (Cordier, 1955). Expression of σ and δ are given in the Eq. (1)
and Eq. (2).
(1)
(2)
A graph correlating σ with δ, specific for axial rotors of low
ratios of hub, typical of rotors of fan jet, is shown in Eck (1973).
Based on this graph, δ and σ can be correlated by Eq.(3).
(3)
After obtaining δ by Eq. (3), and considering the Eq. (2), the
outer diameter of the rotor, De, is calculated by Eq. (4).
(4)
The hub diameter of the rotor, Di, generally, is determined
by the hub ratio, ν = Di /De, which can be obtained from specific
graphics. Eck (1973) provides a minimal hub ratio for various
installations of rotors and of axial fans. In the case of axial rotor
of jet fans, Di is determined by the outer diameter of the housing
of the electric motor, Dcar. Once established the shaft power, Pe,
rotational speed, n and the type of fixation of the electric motor,
Di should be slightly higher or at least equal to Dcar. Thus,
of non-free vortex, for example, Yahya (1983), for design of the
blades. In these methods, both the specific work of the rotor,
Ypá, and meridional velocity, cm, are no longer constant along
the length of the rotor blades. In this paper is used, a type of
non-free vortex adopted by Wallis (1993), where the circumferential component of the absolute velocity after rotor, cu6, varies
linearly along the blade. This condition is represented of dimensionless form by Eq. (8).
(8)
where 6 is the swirl coefficient at the exit of the blades, cm
the mean meridional velocity along the blade, x = r/re the ratio
of a given radius r and the outer radius re, with r between the
hub radius ri and outer radius re, and a and b constants to be
determined.
The main reason for choosing the condition of non-free vortex
represented in the Eq. (8) is due to the fact of to work with hub
ratios, ν, relatively low, which are typical of jet fans. For these
fans, the hub diameter, Di = 2ri, generally, is considered equal
to the outer diameter of the housing of the electric motor that
directly drives the rotor. Therefore, for certain thrust produced
by the jet fan will result an electric motor with shaft power, rotational speed and defined housing, and also a defined outer diameter of the rotor, resulting in hub ratios with values generally
lower than 0,4. For these hub ratios, if is used free-vortex condition would results in inefficient rotor and presents a strong twist
of the blades in the region close to the hub of the rotor, thereby
influencing the characteristics of aerodynamic performance.
The approximate solution of the equation of momentum along
the blade, considering that no swirl of the flow at the inlet of the
rotor (pre-rotation), that is, the circumferential component of the
absolute velocity at the inlet, cu3 = 0, Fig. 1, can be obtained by
(Wallis, 1993):
(9)
where cm6 is the meridional component of the absolute velocity
at the exit, cm3 is the meridional component of the absolute velocity at the inlet and f is the flow coefficient defined by Eq. (10).
(10)
(5)
Known Di and De, the hub ratio, ν, is determined by Eq. (6).
(6)
The ratio hub should not be less than that recommended by
Eck (1973). Another important geometric quantity is the number
of rotor blades, Npá. In jet fans, the number of rotor blades is
usually established according to Eq. (7) Bleier (1998).
(7)
2.2 Aerodynamic design of reversible axial rotor
In the solution of radial equilibrium equation (equation of
momentum in the radial direction) are adopted, certain types
Fig. 1: Representative linear cascade
of a radial section of
reversible axial rotor
indicating only one
direction of flow.
23
PERFORMANCE ANALYSIS THROUGH COMPUTATIONAL FLUID DYNAMICS OF
AXIAL ROTOR WITH SYMMETRIC BLADES USED IN TUNNEL VENTILATION
In the Eq. (9), x represents a fixed value of x (for a given rotor design), that to be obtained by an iterative process, in order
to fulfill the condition given by Eq. (11).
(11)
Considering Eq. (11), and also due the meridional (axial)
component of the absolute velocity at the inlet of the rotor, cm3,
be considered uniform along the blade, the first term of the right
side of Eq. (9) becomes in
(12)
The last term of the right side of Eq. (9) is obtained through
integration, resulting
Fig. 3: Refinement leading edge and trailing edge of the blade.
Because the domain is repeated in each blade, it is not necessary to model this entire for the simulation, so, only the volume
around one blade is meshed, which represents one-twelfth of the
entire rotor. The number of elements of the mesh is 2.401.048.
(13)
The x value is determined such that when multiplies by x the
meridional velocity distribution after the rotor,
, given
in Eq. (9), and integrated in accordance with Eq. (14), produces
a value of
e qual one or very near this, through an iterative process.
(14)
Fig. 4: Layout of distribution of elliptical airfolils
along the blade corresponding to cylindrical sections rectified in planes.
where xi = ri /re.
3. NUMERICAL SIMULATION
The rotor used is designed for a flow of 22,7 m /s and a rotational speed of 1760 rpm. The main geometrical characteristics
are: Di = 380 mm, De = 1000 mm and Npá = 12. In the analysis of
the different cases studied some hypotheses as steady state and
incompressible fluid and isothermal are considered. The density
and dynamic viscosity used in the simulations are ρ = 1,225 kg/
m3 and μ = 1,7894 e-5 kg/m s, respectively. It employs the turbulence model k-ω SST with first-order discretization.
3
3.1 Geometry and mesh
In Fig. 2 the rotor geometry is shown. It was made in commercial
software
Solid Edge ST4 ®
and
subsequently
exported for Icem®
program, where the
computational mesh
is created. A nonstructured mesh is
used with tetrahedral elements and
triangular
prisms.
In Fig. 3, can be
observed the refining conducted in the
leading edge and
trailing edge of the
blade. This refineFig. 2: Perspective view of the reversible axial roment is vital, betor.
cause the quality of
the mesh in these areas is reflected in obtaining a reliable solution.
24
In Fig. 4 is shown the radial distribution of elliptical airfoils, corresponding to cylindrical sections in planes rectified, for the nonfree vortex condition. In this figure are also shown the stagger angles of each airfoil. When in the aerodynamic design of the rotor is
used the freevortex condition, the stagger angles in sections closest
to the hub are small, resulting in a twist higher as compared with
the stagger angles obtained for the case of non-free vortex, where
these angles has minor differences between them.
3.2 Boundary conditions
The boundary conditions are imposed in the Fluent® software, which solves the governing equations for the discretized
domain. On the inlet surface is fixed the condition velocity-inlet,
where must be specified the initial gauge pressure, considered
as 0 Pa. In the outlet surface is uses the outflow condition. Rotational periodicity condition is established in the areas which have
a natural repetition.
Fig. 5: Boundary conditions used in the simulations.
The wall boundary condition is used in solid regions where
fluid flows; these surfaces may be stationary or mobile. In this
study is chosen for the hub and the blade the option of rotational
OF AXIAL ROTOR WITH SYMMETRIC BLADES USED IN TUNNEL VENTILATION
motion in relation to the zone of the adjacent cell, the other surfaces being treated as stationary faces. In Fig. 5 are summarized
the boundary conditions mentioned above.
4. RESULTS
Fig. 8; Relativevelocity
colored
by velocity magnitude (m/s) for the
reversible
axial
rotor at the point
of maximum aerodynamic
performance.
4.1 Characteristics curves of reversible axial rotor
The characteristics curves are evaluated for a single rotation,
1760 rpm. In Fig. 6, are represented the curves of aerodynamic
performance, total pressure, shaft power and thrust obtained
from the numerical simulation in Fluent®. The layout of these is
made varying the flow, Q, or axial velocity at the rotor inlet (ca o
cm) for 12 different operating points.
Can be appreciated that pumping limit is approximately
12 m3/s. The number of cases simulated with flows below this limit
is less, because in this region is not possible adequately represents
the behavior of the fluid, for
≠being in the unstable operation zone. Also is noted
that the maximum efficiency
point of the fan (69,58 %)
is located in 16,55 m3/s,
and not in 22,7 m3/s, flow
for which was designed the
rotor. At the design point is
found in the simulations a
performance of 62,06 %, a
shaft power of 24,19 cv and
Fig. 6: Characteristic curves of reversible a thrust of 807,76 N.
axial rotor designed according to the condition of non free-vortex for 1760 rpm.
4.2 Aerodynamic performance characteristics of
reversible axial rotor
In sequence, some results obtained with the program computational FLUENT® and the program CFD - Post® are presented.
The different graphs shown in this section were obtained to analyze the operating point corresponding to the maximum performance obtained in the simulations.
In Fig. 7 (a) the contours of static pressure on pressure side
of the blade are shown. These contours indicate that there are
pressures higher in regions close to the leading edge, and lower
pressures near the trailing edge. In addition, the major pressures
correspond to the sections closest to the tip of the blade and not
to those closer to the hub.
In Fig. 7 (b) the contours of static pressure on suction side of
the blade are shown. In this figure it is noted that the lower pressure are located near to the leading edge, gradually increasing
until the region near to the trailing edge. Also, can be seen that
the pressure decrease as it gets closer to the blade tip.
In Fig.8 the vectors of relative velocities along the blade are
represented. It can be observed that the condition of tangency
of these vectors with respect to the blade is satisfied, i.e., those
vectors accompany appropriately the airfoils of each radial section of the rotor, from the leading edge to the trailing edge.
Fig. 7: Contours of static pressure (Pascal) (a) on the pressure side of the
blade (b) on the suction side of the blade.
5. CONCLUSIONS
The main geometric quantities of the rotor, and the most important quantities used in the aerodynamic design methodology
of the blades of the reversible axial rotor, that uses the condition
of non free-vortex for the solution of the radial equilibrium equation were determined.
Simulations in CFD were made which allowed the construction of the characteristics curves of aerodynamic performance,
total pressure, shaft power and thrust of axial rotor that having
blades with elliptical format profiles. These curves show that the
recommended working range is between 13 m3/s and 23,5 m3/s.
Furthermore, is observed that the point of maximum hydraulic
performance is located in 16.55 m3/s, and not in 22.7 m3/s, flow
for which was designed the rotor. This difference is due to that
the flow in the inlet of rotor, at a point very close to this, it is not
only influenced by the presence of the blades but also by the
cube of the same, especially in the closest regions to hub that
in those closest to the casing. In a similar manner, the angle of
the incident flow in the rotor, especially in radial sections closest
to the hub, results not being the angle for the condition without
shock, thus will appear shock losses (losses of incidence) where
is expected the absence of such losses (design point).
These facts make that decreases the performance of rotor
and that its maximum value is displaced, usually, for flow rates
lower than that of the design point.
Some aerodynamic performance characteristics of the reversible axial rotor were found, as the contours of static pressure in
both the pressure side and the suction side of the blade, showing
the areas in which are located higher and lower pressures.
6. REFERENCES
• Ballesteros, R., Álvarez, G., Santolaria, C., Fernández, J. M.
and Argüelles, K., 2002. “Análisis numérico y experimental
del flujo en un ventilador de chorro”. In Proceedings of the
XV Congreso Nacional de Ingeniería Mecánica. Cadiz, Spain.
• Bleier, F. P., 1998. Fan Handbook: Selection, Application and
Design. McGraw-Hill.
• Cordier, O., 1955. Ähnlichkeitsbetrachtung bei Strömungsmaschinen. VDI-Zeitschrift, Band 97, Nr. 34, S. pp 12331234.
• Eck, B., 1973. Fans: design and operation of centrifugal,
axial-flow and cross-flow fans. Pergamon Press.
• Espinosa, A. L. S., Fajardo, L. C., Ramírez, R. G. C. and Oliveira, W., 2011. “Projeto aerodinâmico de rotor axial reversível
de ventilador de jato”, In: Proceedings of the X Congresso
Iberoamericano de Engenharia Mecânica-CIBEM10. Oporto,
Portugal. Köktürk, T., 2005. Design and performance analysis
of a reversible axial flow fan. M.Sc. thesis, Middle East Technical University, Turkey.
• Wallis, R. A., 1993. Axial Flow Fan and Ducts, Krieger Publishing Company.
• Yahya, S. M., 1983. Turbines, compressors and fans. Tata Mc
Graw-Hill Publishing Company Limited.
25
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26
27
REGULAÇÃO
EXPANSÃO VIA USINA-PLATAFORMA
Da redação Quando o país começou a falar sobre a implantação do conceito
de usina-plataforma, solução menos agressiva ao meio ambiente,
a previsão era realizar o primeiro leilão em 2011, com a hidrelétrica de São Luiz do Tapajós, de 6.133 MW, entrando em operação
em 2016. Três anos depois e uma série de entraves ambientais,
jurídicos e atrasos nos estudos de viabilidade que minguaram a
participação hídrica nos últimos leilões, o governo volta a falar em
licitar a megausina localizada no rio Tapajós (PA) este ano.
Projeto considerado estruturante e prioritário pela Resolução
nº 3 do Conselho Nacional de Política Energética (CNPE), São Luiz
do Tapajós, se sair da gaveta, terá peso considerável para o país.
Dos 19.917 MW de projetos hidrelétricos incluídos no Plano Decenal de Energia (PDE 2022), a usina representará mais de 30%
da capacidade prevista para entrar daqui a oito anos.
Além do bloco considerável de energia hidrelétrica, São Luiz
do Tapajós também vai representar um desafio para a engenharia brasileira. O projeto será o primeiro a adotar, no país, o conceito de usina-plataforma, uma solução para preservar o meio
ambiente de uma região onde está localizada a maior parte do
potencial do país estimado em 260 GW.
"O governo trabalha para licitar a usina este ano", informou
Maurício Tolmasquim, presidente da Empresa de Pesquisa Energética (EPE) logo após o último leilão de energia de 2013. Coordenado
pela Eletrobras, o grupo responsável pelos estudos de viabilidade
tem até 31 de julho para concluir o trabalho, de acordo com prazo
estabelecido pela Agência Nacional de Energia Elétrica (Aneel).
O prazo anterior para entregar os estudos ao Instituto
Brasileiro de Meio Ambiente e dos Recursos Naturais Renováveis
(Ibama) era 20 de novembro do ano passado. Os estudos de São
Luiz do Tapajós, assim como os da hidrelétrica de Jotobá (2.338
MW), no mesmo rio, foram retomados em agosto de 2013.
Estima-se que, com 6.133 MW, São Luiz do Tapajós, produza
por ano quase 30 mil GWh. A usina terá uma área inundada
de dois mil metros quadrados, deixando uma área protegida de
aproximadamente 100 mil metros quadrados.
Conceito da usina
Os entraves ambientais para licitar novos projetos hidrelétricos
levaram o governo a lançar mão do modelo de usina plataforma, o
que significa fazer um projeto encravado numa região de floresta.
O conceito busca evitar a criação de vilas e núcleos urbanos no em
torno da hidrelétrica, com grande mobilização de trabalhadores,
como normalmente acontece em obras deste porte.
Na fase de construção da obra da usina-plataforma, modelo
apresentado anos atrás por Márcio Zimmermann, secretário-executivo do Ministério de Minas e Energia (MME), os trabalhadores
trabalhariam em turnos, sendo transportados para o local por
helicóptero ou por terra. Quando em funcionamento, a usina teria
uma operação toda automatizada, requerendo o trabalho de um
número menor de pessoas.
"A ideia da usina-plataforma é a baixa intervenção humana
ao meio ambiente em redor. Em outras palavras, não há perda
de florestas para a urbanização, o que permite a preservação",
explica Leontina Pinto, diretora executiva da Engenho, Pesquisa,
Desenvolvimento e Consultoria.
28
Arquivo Pessoal
Governo trabalha para licitar este ano São Luiz do Tapajós, no Pará,
primeira hidrelétrica a usar o conceito que busca menor impacto ambiental
Imagem da região estudada para a implantação da hidrelétrica de São Luiz
do Tapajós, no rio Tocantins. Grupo de Estudos do Tapajós, formado por
Eletrobras, Eletronorte, GDF SUEZ, Cemig, Copel, Neoenergia, EDF, Endesa
Brasil e Camargo Corrêa, tem prazo até 31 de julho para concluir estudos
de viabilidade.
Image of the region studied for the implantation of São Luiz Tapajós
Hydroelectric Plant, Tocantins River. Study Group Tapajos formed by
Eletrobras Eletronorte GDF Suez, Cemig, Copel, Neoenergia, EDF, Endesa
Brazil and Camargo Correa, has until July 31 to complete viability studies.
Sobrecusto
Segundo estimativa do mercado, a construção das duas hidrelétricas, no rio Tapajós, deve ficar em torno de R$ 26 bilhões,
sendo cerca de R$ 15 bilhões para erguer São Luiz do Tapajós.
Este valor pode ainda ser bem maior, uma vez que a ampliação
do projeto para 7.880 MW está em análise. O valor final depende,
claro, de outras variáveis que serão incorporadas no projeto final.
"Não conheço o sobrecusto associado ao conceito plataforma,
mas o transporte por via aérea deve ser mais oneroso do que a
construção convencional", diz a professora Leontina Pinto. "Como
todo novo conceito, julgo que sua implementação terá imprevistos
e ajustes – que só serão conhecidos a longo prazo", acrescenta.
Embora considere crucial o país explorar o potencial hidrelétrico que tem na região Amazônica, João Carlos Mello, presidente
da Thymos Energia e Consultoria, considera o modelo de usinaplataforma uma utopia. Para ele, ainda não existe um cálculo
sobre o sobrecusto que uma obra de tal porte teria, sobretudo,
pela logística que envolveria.
"Certamente, será um custo alto", diz. Para ele, se o planejamento quer retomar um pouco dos reservatórios, Tapajós, com
um conjunto de sete usinas que somam um potencial de 14 mil
MW, é um bom caminho. A professora Leontina Pinta reforça,
afirmando que o modelo plataforma não implica em abrir mão de
reservatórios.
Segundo ela, a construção e operação da usina-plataforma
elimina apenas o custo ambiental da implantação de núcleos
HIDRO&HYDRO - PCH NOTÍCIAS & SHP NEWS | ISSN 1676-0220
REGULATION
EXPANSION VIA PLANT-PLATFORM
Translation: Joana Sawaya de Almeida
Government works to bid this year, São Luiz do Tapajos, Para, first hydroelectric
plant to use the concept that seeks to lower environmental impact
until July 31st to conclude the work, according to the deadline set
by the National Electrical Energy Agency (Aneel).
The previous deadline to deliver the studies to the Brazilian
Institute of the Environment and Renewable Natural Resources
was November 20th of last year. Studies of São Luiz de Tapajos
as well as of the hydroelectric plant at Jotobá (2.338 MW), in the
same river, were resumed in August 2013.
It is estimated that, with 6,133 MW, Sao Luiz de Tapajos will
produce, per year, almost 30,000 GWh. The plant will have a
flooded two thousand square meters area, leaving a protected
area of approximately 100,000 square meters.
Plant concept
When the country began to speak about the implantation of
the concept of the plant platform with less impact on the environment, the prediction was to hold the first auction in 2011,
with the hydroelectric plant São Luiz Tapajos, with 6,133 MW,
with operation beginning in 2016. Three years later and a series of environmental barriers, delays and legal feasibility studies
dwindled the hydroelectric participation in recent auctions, the
government begins to discuss a bid for a mega-plant located in
the Tapajos River (PA) this year.
Project considered structuring and priority by the Council
Resolution no. 3 of the Conselho Nacional de Política Energética
(CNPE), São Luiz de Tapajos, if it leaves the drawing board, will
have considerable weight for the country. Of the 19,917 MW of
hydroelectric plant projects included in the Plano Decenal de Energia (PDE 2022), the plant will represent more than 30% capacity, predicted to begin eight years from now.
Beyond the considerable block of hydroelectric energy, São
Luiz de Tapajos will also pose a challenge to Brazilian engineering. The project will be the first of the country to adopt the concept of a plant platform, a solution to preserve the environment
of a region where most of the potential of the country, estimated
at 260 GW, is located.
“The government works to bid this plant this year,” informed
Maurício Tolmasquim, president of the Energy Research Company
(EPE) soon after the last energy auction of 2013. Coordinated by
Electrobras, the group responsible for the viability studies has
Environmental barriers to bid new hydroelectric plant projects
led the government to make use of the model of the platform
plant, which means doing a project stuck in a forest region. The
concept seeks to avoid the creation of villages and urban cores
around hydroelectric plants, with great mobilization of workers,
as usually happens in works of this size.
In the construction phase of the plant-platform model presented years ago by Márcio Zimmerman, executive secretary of
the Ministry of Mines and Energy (MME), the workers worked
in shifts, being transported to the site by helicopter or by land.
When operational, the plant would have an automated the whole
operation, requiring the work of less people.
“The idea of the plant platform is under human intervention
to the surrounding environment. In other words, there is no loss
of forests to urbanization, which allows preservation,” explains
Leontina Pinto, executive director of Ingenuity, Research, Development and Consulting.
Additional costs
According to estimates of the market, the construction of the
two hydroelectric plants, in the Tapajós River, should be around
R$26 billion, with about R$15 billion to build São Luiz de Tapajos. This value could be even higher since the expansion of the
project to 7,880 MW is under review. The final value depends, of
course, on other variables that will be incorporated into the final
design.
"I don’t know the extra costs associated with the platform
concept, but transportation by air must be more expensive than
that of conventional construction," says Professor Leontina Pinto.
"Like every new concept, I believe that their implementation will
have unforeseen adjustments - which will be known only in the
long term," she adds.
Although he considers it crucial to the country to explore the
hydroelectric potential of the Amazon region, João Carlos Mello,
president of the Thymos Energy and Consulting, considers the
model of the plant platform utopia. For him, there is still no calculation of the extra cost that a work of such scope would, mainly,
by logistics, would involve.
“Certainly, there will be a high cost,” he says. For him, if the
planning wants to return a bit of the reservoirs, Tapajós, with a
set of seven plants that add up to a potential of 14,000 MW, is a
good way. The professor, Leontina Pinto reinforces, affirming that
29
REGULAÇÃO
urbanos. "Não impede a construção de reservatórios, pois você
pode ter uma enorme área inundada sem ter feito estradas ou
vilas para a acomodação de trabalhadores", diz a diretora da
Engenho. Para ela, está mais do que na hora de o país discutir o
modelo energético que quer.
"Devemos abrir mão do potencial amazônico e enfrentar uma
possível escassez, inclusive com o custo ambiental da pesada
geração termoelétrica? Devemos buscar uma solução mais balanceada?, questiona.
Dados do artigo "Por que o Brasil está trocando as hidrelétricas e seus reservatórios por energia mais cara e poluente?,
escrito por Márcio Tancredi e Omar Alves Abbud, da Consultoria
Legislativa do Senado Federal, mostram como a capacidade do
setor elétrico de acumular água nos reservatórios caiu nas usinas
leiloadas entre 2000 e 2012.
Dos 42 projetos licitados no período, num total de 28,8 mil
MW, apenas 10 usinas, com 1.940 MW, possuem reservatórios.
Com 26,8 mmil MW, os demais 32 são a fio d"água. Ou seja,
apenas 6,73% da capacidade de geração proveem de usinas
com reservatório.
Pressão socioeconômica
No entanto, mesmo com a proposta do modelo de construção
que será adotado, seria preciso enfrentar a questão ambiental
e indígena da região. Assim como aconteceu com a hidrelétrica
de Belo Monte (11.300 MW), no rio Xingu, as pressões sociais e
ambientais farão parte do dia a dia de todo o processo de elaboração e licitação de São Luiz do Tapajós, localizada na região
dos índios Munduruku. No Ministério Público Federal do Pará já
existem ações contra a instalação da usina.
"As dificuldades para construir hidrelétricas nos casos dos
rios Xingu e Tapajós são as mesmas. E da mesma forma, não
há como se determinar se a regra do aproveitamento ótimo foi
cumprida nos estudos da bacia do Tapajós. É possível que a
auto-restrição a que redução de custos e as facilidades
de licenciamento ambiental costumam induzir tenha
influenciado o inventário da bacia", aponta o artigo da Consultoria Legislativa do Senado
Federal.
30
the model platform does not imply giving up reservoirs.
According to her, the construction and operation of the plant
platform only eliminates the environmental cost of the implantation of urban cores. "It does not prevent the construction of
reservoirs, because you can have a huge flooded area without
roads or towns done for the accommodation of workers," says
the director of Ingenuity. For her, it is more than time for the
country to discuss the energetic model it wants.
Must we give up the Amazonian potential and face a possible
shortage, including the environmental cost of heavy thermoelectric generation? Should we seek a more balanced solution?” she
questions.
Data from the article "Why Brazil is swapping hydroelectric
plants and their reservoirs for more expensive and polluting energy?" written by Márcio Tancredi, and Omar Ahmed Abbus, the
Legislative Advisory of the Senate, shows how the ability of the
electric sector to accumulate water reservoirs is falling in the
mills auctioned between 2000 and 2012.
Of the 42 projects bid in the period, with a total of 28,800
MW, only 10 plants, with 1,940 MW, have reservoirs. With 26,800
MW, the other 32 work with the flow of the river. Or, only 6.73%
of the capacity of generation comes from plants with reservoirs.
Socioeconomic pressure
However, even with the proposed construction of the model
that will be adopted, it would have to face the environmental and
indigenous matters in the region. As with the Belo Monte Hydroelectric Plant (11,300 MW), on the Xingu River, social and environmental pressures will be part of the daily lives of the whole process
of elaboration and bid of São Luiz Tapajós, located in the region of
the Mundurukú Indians. In the Federal Public Prosecutor of Pará
there are already actions against the installation of the plant.
"The difficulties to build hydroelectric plants on the Tapajos
and Xingu rivers are the same. And similarly, there is no way to
determine if the rule of optimum utilization was fulfilled in studies of the Tapajos basin. It is possible that self-restriction of the
reduction of costs and the ease of environmental licensing are
usually induced have influenced the inventory of the basin,"
points out the article from the Senate Legislative Advisory.

anotações - cerpch

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