Prediction of cavitation and its mitigation techniques in hydraulic turbines - A review

Cavitation is a major problem in the hydraulic reaction turbine because it damages turbine components, affects turbine performance and increases maintenance. Hence there is a need for further research and development on the minimization of cavitation in turbines based on previous research work. Cavitation occurs due to the fall in pressure below vapour pressure of water, which may be due to inappropriate design, frequent change in operating conditions or improper setting of the turbine runner to the tailrace level. The cavitation prediction in the turbine is a challenging task and its prediction is useful in adopting appropriate techniques for its mitigation. The theoretical and computational techniques are commonly used to predict cavitation at the design stage, but the experimental techniques can be used during design as well as operating conditions. This paper presents a review of cavitation prediction techniques and performance reduction of hydraulic turbines. Cavitation is inevitable in turbines, but it can be mitigated by some techniques which avoid drastic pressure reduction in turbine components having presumable cavitation. In addition, the material damage due to cavitation can be minimized by using cavitation resistant materials and polishing surfaces. The cavitation prevention or mitigation techniques have also been discussed.