Experimental Studies of Dimpled Surface Effect on the Performance of Linear Cascade under Different Incidence Angles

Abstract

In this paper, preliminary experiments were conducted to investigate the effect of dimpled surface on the performance of linear cascade. Two dimple configurations with a diameter of 1.0mm and a depth-diameter ratio of 0.2, which were located in 30%-60% and 75%-95% axial chord lengths of suction side respectively, were studied to validate their effectiveness in reducing total pressure loss. Incidence angles of -5.3°, 0°, 5.3°, 7.5°, 10° and inlet Mach number of 0.4 were used in each experiment with 1.5% Tu. Total pressure loss coefficients and blade loading force measurements were made on the dimpled blades by a mini 5-hole pressure probe and compared to the smooth blades. The experimental results show that the reduction of the total pressure loss coefficients of dimpled blades is obvious at the incidence angle of 0°, 5.3°, and 7.5°, and the change of the total pressure loss coefficients of dimpled blades is very slight at the incidence angle of -5.3°, and 10°. In addition, there exists a slight increase of loading force with dimpled blades. The comparison results also indicate that dimples on 30%-60% of suction side is more effective in loss reduction than that on 75%-95% of suction side at all incidence angles.