Development of a rapid method for calculating  the hydroturbine cavitation characteristics

It is noted that when calculating the cavitation indicators of a hydraulic turbine by the rapid method implemented in the GRANITE program, the influence of cavitation on the pressure distribution is taken into account only in the zone of cavitation cavities on the surface of the blade, where tensile stresses occur. The fact that the cavity extends downstream beyond the zone of tensile stresses is not taken into account. This circumstance leads to systematic errors in determining the cavitation indices of the turbine at the specified rapid procedure. In this case the calculated values of the cavitation indicators tend to be greater than the corresponding experimental values. The study presents the analysis and comparison of results of calculation and experimental research of cavitation performance of hydraulic turbines of different specific speed. We have proposed practical recommendations, which have helped to improve the accuracy of the calculation of the critical cavitation coefficient of the hydraulic turbine according to the specified rapid procedure.