Performance and internal flow of an undershot-type cross-flow water turbine

An undershot-type cross-flow water turbine does not require a casing for open channels and hence considerable simplification is attained. However, because this water turbine does not have a casing and has a free surface, it is believed that the internal flow considerably changes with the rotational speed. In this study, the performance and internal flow of the undershot-type cross-flow water turbine at a constant flow rate were investigated by an experiment and numerical analysis, and the following facts were clarified. The first-stage inlet area and the second-stage inlet and outlet areas are reduced with increase in rotational speed. Shock loss at the second- and first-stage areas is dominant in low- and high-rotational-speed regions, respectively. Moreover, shock loss has a considerable influence on the performance of this water turbine in low- and high-rotational-speed regions. ©2013 The Japan Society of Mechanical Engineers.