Flow Field Analysis And Hydraulic Performance Optimization For Hydraulic Turbine

In this paper, the research achievements for the Francis turbine was supported by the National Nature Science Foundation of China (Grant No. 90410019), and the research findings for the Kaplan turbine were gained owing to the support of the National Nature Science Foundation of China (Grant No. 50379044). The flow field investigation and hydraulic performance optimization for the hydraulic turbine were carried out and the research results were verified by use of experimental investigations. The main research findings were as follows.Based on geometrical characteristic of through-flow components of reaction turbine and patched multi-block grid generating technique, the block topology for through-flow components of reaction turbine was achieved. The universal grid-generating program was developed on the basis of algebraic grid generation method. It could generate rapidly structured grids to describe the flow passage geometry of spiral case, Semi-spiral case, guide vanes, mixed-flow runner, axis-flow runner and draft tube of the reaction turbine.An algorithm to lengthen the inlet or outlet edge of the runner blade in the Francis turbine, and the blade redesign technical measure based on NURBS surface was put forward respectively. The relationship between blade redesign and flow field investigation in the turbine was constructed and a synthetical optimization performance technique of the turbine was brought forward according to the relationship. The synthetical optimization performance technique had been applied successfully to develop the Three Gorge turbine and the others.The whole performance of the through-flow components of reaction turbine was improved by use of the synthetical optimization performance technique based on numerical simulation.Using k-ε model numerical analysis, the numerical efficiency of thewater turbine was achieved, which accord with the test value near the design point. Whereas, the numerical efficiency of the water turbine that was away from the design point was departure from the test value.In this paper, based on CFD analysis a technical method, which is to improve pressure pulsation by means of controlling the velocity circulation distribution at runner exit, was put forward. The problem of pressure pulsation under high part load condition appeared in the turbine model test of the Three Gorge Project was solved drastically. Through performance optimization, the hydraulic performance of the turbine on the right bank of the Three Gorge Project was improved, and high efficiency and low cavitations coefficient were obtained. In addition, the pressure pulsation performance was advanced materially compare with the turbine on the left bank. This technique was applied in the turbine on the right bank of the Three Gorge Project, thus lead to the success in the international tender.The influence of flange clearance of axis-flow runner on the runner ?fficiency, leakage flow volume, main flow and the occurring position of the clearance vortex were discussed respectively.How to select a position of the guide vanes and runner interface was discussed through analyzing the influence of the selected different interface on the numerical simulation results. Based on the study of matching relation of the guide vanes and runner interface, the performance of axis-flow turbine was optimized.Based on the Reynolds-stresses model and k-e model, under the best operation condition the numerical simulation of axis-flow turbine was conducted respectively. The computational solution indicated that the Reynolds-stresses model did not take on its advantage, whereas show a shortage of long calculating time expense. The prediction value of clearance vortex, which was gained by the whole machine simulation, was closer to the test value than one that was obtained by single component simulation.According to the test result, the clearance vortex occurring was related to the blade incidence angle. The more the incidence angle is, the more the clearance vortex is. The damage of clearance vortex to the blades is the main factor. The position and size of clearance vortex varied with operation condition change. The clearance flows on flange have five cavitations forms. The five forms vary with the blade open position, one or two be likely to occur at the same time*...