Control and Entropy Analysis of Tip Leakage Flow for Compressor Cascade under Different Clearance Sizes with Endwall Suction To investigate the influence of the change of tip clearance size on the control effect of the endwall suction, the effects of endwall suction on the aerodynamic performance of the axial compressor cascade were studied numerically. Three tip clearance sizes of 0.5% h, 1.0% h, and 2.0% h (h is the blade height) were mainly considered. The results show that the endwall suction scheme whose coverage range was 8xe2x80x9333% axial chord can reduce the leakage flow and improve the aerodynamic performance by directly influencing the structure of tip leakage vortex. The overall total pressure loss coefficients of the three clearance size schemes at 0xc2xb0 angle of incidence with 0.4 inlet Mach number are reduced by about 10.3%, 10.8%, and 6.0%, respectively, at the suction flow rate of 0.7%. Under the same suction flow rate, the onset position of the tip leakage vortex of the cascade with small clearance is shifted from the 15% of the axial chord length of original to the 48% of the axial chord length, which with large clearance is nearly no changed. The leakage flow rate and the distance from the leakage vortex to the suction slot are the main reasons for the different control effect of the endwall suction under different tip clearance sizes. The difference of the spanwise distribution of flow field parameters may also cause the difference of flow control effect.

Effects of the Varying Lateral Clearances on the Pressure Ripple of Internal Gear Pumps in Biped Robots  Internal gear pumps (IGPs) are commonly applied in biped robotsxe2x80x99 hydraulic actuation systems serving as the power unit. The pumpxe2x80x99s outlet pressure ripple does harm to accurate motion controls and is usually lowered by adopting an accumulator. This paper investigates the effects of the varying lateral clearances between the gear and the floating plate on the pressure ripple. It aims to provide advices on manufacturing the gears to lower the pumpxe2x80x99s outlet pressure ripple so that the accumulator could be smaller, which is of great importance to weight and space saving in biped robotsxe2x80x99 design. A mathematical model was established for evaluating the outlet pressure considering the lateral clearancesxe2x80x99 varying phenomenon. Moreover, the outlet pressure was measured by highfrequency pressure sensors for verifying the effects of the varying lateral clearances. The simulated and experimental results suggest that the outlet pressure concerning varying lateral clearances has small ripples characterized by high frequency and big ripples characterized by low frequency. Additionally, the pressure ripple, especially the big ripple, can be lowered by well manufacturing the gear pairxe2x80x99s lateral sides, ensuring the consistency of the tooth width of the gear.