Study on Cavitation Occurrence Condition and Effect of Cavitation on Cross-flow Turbine Performance

Abstract

In cross-flow turbine, cavitation tends to occur duo to large pressure differences between both sides of the blade because the chord length is short．Therefore the turbine can not apply to a high head. In this study, the critical condition of cavitation occurring were investigated by flow observation, and its effect on turbine performance was clarified by experiments. As a result，it can be clarifilied that the critical condition can be expressed approximated by the linear equation of effective head and NPSHa. In the case of high head and low NPSHa, in which air bubbles are liberated from water, and at low head, in which air bubbles are not easily ejected from the runner inside, the water vapor of cavitation and liberated bubbles formed a large gas-phase region in the runner, and efficiency is not decreased due to preventing water collision with the shaft.