Influence of air supply on the performance and internal flow characteristics of a cross flow turbine

• New air supply method into the turbine is developed to improve the performance.
• There is a 3.5% efficiency improvement by the new air supply method.
• The air layer on the turbine chamber suppresses the negative torque at Region 1.

This study attempts to improve the efficiency of a given type of cross flow turbine by supplying air from air suction holes. A newly developed air supply method is adopted. CFD analysis of the cross flow turbine is carried out to investigate the performance and internal flow characteristics of the turbine in detail. The air layer prevents shock loss between water flow and axis and suppresses recirculation flow in the runner passage. Hence, it is necessary to measure the amount of air layer in the runner passage and examine its effect on the performance of the cross flow turbine. The result shows that the turbine efficiency has improved more as the newly developed air supply method is applied effectively.