Maruzewski, Pierre
(Ecole polytechnique federale de Lausanne, Laboratory of Hydraulic Machines)
,
Hasmatuchi, Vlad
(Ecole polytechnique federale de Lausanne, Laboratory of Hydraulic Machines)
,
Mombelli, Henri-Pascal
(Ecole polytechnique federale de Lausanne, Laboratory of Hydraulic Machines)
,
Burggraeve, Danny
(British Columbia Hydro Generating Engineering Country)
,
Iosfin, Jacob
(British Columbia Hydro Generating Engineering Country)
,
Finnegan, Peter
(British Columbia Hydro Generating Engineering Country)
,
Avellan, Francois
(Ecole polytechnique federale de Lausanne, Laboratory of Hydraulic Machines)
In the process of turbine modernizations, the investigation of the influences of water passage roughness on radial flow machine performance is crucial and validates the efficiency step up between reduced scale model and prototype. This study presents the specific losses per component of a Francis tu...
In the process of turbine modernizations, the investigation of the influences of water passage roughness on radial flow machine performance is crucial and validates the efficiency step up between reduced scale model and prototype. This study presents the specific losses per component of a Francis turbine, which are estimated by CFD simulation. Simulations are performed for different water passage surface roughness heights, which represents the equivalent sand grain roughness height. As a result, the boundary layer logarithmic velocity profile still exists for rough walls, but moves closer to the wall. Consequently, the wall friction depends not only on roughness height but also on its shape and distribution. The specific losses are determined by CFD numerical simulations for each component of the prototype, taking into account its own specific sand grain roughness height. The model efficiency step up between reduced scale model and prototype value is finally computed by the assessment of specific losses on prototype and by evaluating specific losses for a reduced scale model with smooth walls. Furthermore, surveys of rough walls of each component were performed during the geometry recovery on the prototype and comparisons are made with experimental data from the EPFL Laboratory for Hydraulic Machines reduced scale model measurements. This study underlines that if rough walls are considered, the CFD approach estimates well the local friction loss coefficient. It is clear that by considering sand grain roughness heights in CFD simulations, its forms a significant part of the global performance estimation. The availability of the efficiency field measurements provides an unique opportunity to assess the CFD method in view of a systematic approach for turbine modernization step up evaluation. Moreover, this paper states that CFD is a very promising tool for future evaluation of turbine performance transposition from the scale model to the prototype.
In the process of turbine modernizations, the investigation of the influences of water passage roughness on radial flow machine performance is crucial and validates the efficiency step up between reduced scale model and prototype. This study presents the specific losses per component of a Francis turbine, which are estimated by CFD simulation. Simulations are performed for different water passage surface roughness heights, which represents the equivalent sand grain roughness height. As a result, the boundary layer logarithmic velocity profile still exists for rough walls, but moves closer to the wall. Consequently, the wall friction depends not only on roughness height but also on its shape and distribution. The specific losses are determined by CFD numerical simulations for each component of the prototype, taking into account its own specific sand grain roughness height. The model efficiency step up between reduced scale model and prototype value is finally computed by the assessment of specific losses on prototype and by evaluating specific losses for a reduced scale model with smooth walls. Furthermore, surveys of rough walls of each component were performed during the geometry recovery on the prototype and comparisons are made with experimental data from the EPFL Laboratory for Hydraulic Machines reduced scale model measurements. This study underlines that if rough walls are considered, the CFD approach estimates well the local friction loss coefficient. It is clear that by considering sand grain roughness heights in CFD simulations, its forms a significant part of the global performance estimation. The availability of the efficiency field measurements provides an unique opportunity to assess the CFD method in view of a systematic approach for turbine modernization step up evaluation. Moreover, this paper states that CFD is a very promising tool for future evaluation of turbine performance transposition from the scale model to the prototype.
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문제 정의
The authors would like to express sincere gratitude to the staff of the EPFL Laboratory for Hydraulic Machines for its support and advices to well lead this work.
제안 방법
The quality of grids is estimated by evaluating the sensitivity of the pressure coefficient Cp versus three kinds of mesh defined from the coarsest to the finest. The properties and the error of these meshes applied to the draft tube are presented in Table 2.
The scope of the present paper is to present the methodology of prediction for the efficiency step up based on CFD numerical simulation taking into account the turbine component wall roughness and to validate this step up with respect to the available experimental results obtained from both field and model tests. First the BC Hydro Francis turbine case study and EPFL base line tests are presented.
대상 데이터
GMS houses 10 generating units that have a combined maximum output of 2’730 MW. The GMS turbines consist of medium head hydraulic Francis turbines. The case study is about turbines 1 to 5, commissioned in 1968 see Fig.
The GMS turbines consist of medium head hydraulic Francis turbines. The case study is about turbines 1 to 5, commissioned in 1968 see Fig. 2; these turbines have a rated power of 265 MW under 161 mWC head.
The dam is 186 m high and 2’068 m long along its crest.
성능/효과
93% of total specific losses. Finally, the analysis of the results made apparent that it is more beneficial to rehabilitate the guide vane and the runner, than the spiral casing, the stay vanes or the draft tube.
참고문헌 (14)
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Krishnamachar P., Fay A., 2007, “The effect of surface roughness, International Water Power and Dam Construction, www.waterpowermagazine.com.
Maruzewski P., Hasmatuchi V., Mombelli H.-P., Burggraeve D., Iosfin J., Finnegan P. and Avellan F., 2008, “Surface roughness impact on Francis turbine performances and prediction of efficiency step up,” 24th IAHR Symposium on Hydraulic Machinery and Systems, Foz do Iguassu, Brasil.
Churchill S.W., 1988, Viscous Flows, “The practical use of theory,” Butterworth Ser Chem Engng, ISBN 0-409-95185-4.
EPFL, 2006, British Columbia Hydro, “Geometry recover of Francis turbine,” technical report, Lausanne, Switzerland.
Lechner R., Menter F. R., 2008, “Treatment of rough wall on CFX-11, ANSYS technical report,” Germany.
White M., 1979, “Viscous Fluid flow,” Mac Graw-Hill.
Schlichting H., 1979, “Boundary layer,” Mac Graw Hill.
Avellan F., 2005, Cours de turbomachines hydrauliques, equations des turbomachines. Cours, EPFL.
Osterwalder J., Hippe L., 1984, “Guidelines for efficiency scaling process of hydraulic turbomachines with different technical roughnesses of low passages,” Journal Hydraulic Research, Vol. 22, No. 2, pp. 77-10.
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