Hydraulic turbines recently attract attention again because of their cleanness for environment. With regard to a Pelton turbine, which is the most popular impulse water turbine, scale effect has been ignored mainly due to its complicated high-speed flow with free surface. However, it is getting to be known that a negative scale effect is existing, namely, the performance of prototype is worse than that of model in case of high head. In this paper, we focus on the jet from a Pelton turbine nozzle in order to obtain a hint of the scale effect from a viewpoint of jet behavior. We carried out numerical calculations of the unsteady jet from a model nozzle for various flow rates and heads. The results show that the velocity distribution in jet depends on flow rate strongly and that higher head makes the jet diameter larger. Another calculation, which considers the entrainment of water droplets into jet, shows that the entrainment also makes the jet diameter larger. The enlargement of jet diameter may cause a lowering of efficiency.
|Title of host publication||Proceedings of the 1999 3rd ASME/JSME Joint Fluids Engineering Conference, FEDSM'99, San Francisco, California, USA, 18-23 July 1999 (CD-ROM)|
|Publisher||American Society of Mechanical Engineers|
|Number of pages||1|
|Publication status||Published - 1 Dec 1999|
- Numerical analysis
- Pelton turbine
- Scale effect