One effective measure to improve the efficiency of the super low specific speed turbine in cooling tower

The hydraulic losses of hydraulic turbine are mainly distributed in the volute, stay vane, runner and draft tube. The theories and practices show that the hydraulic loss of stay vane occupies a large proportion in total in low specific speed turbine and this problem is more serious in super low specific speed turbine. The super low specific speed Francis turbine, which has been widely used to drive the fan directly in cooling tower, has low height guide vane and small guide vane outlet angle. These cause great hydraulic loss of guide vane. Based on the CFD analysis, the hydraulic loss of the stay ring with guide vanes and that of the stay ring without guide vanes have been compared. It has been found that the hydraulic losses of the former can reach to 13.7% and the hydraulic losses of the latter can be reduced to 3.41%. That is to say, without stay vane, the total efficiency of the super low specific speed turbine can be improved nearly 10%. Lastly, the design principles of super low specific speed turbine without guide vanes have been proposed.