An Experimental Study of Blade Tip Clearance Suction

A computational and experimental study was carried out to determine whether blade tip suction can increase compressor efficiency. Compressor flow fields contain concentrated regions of high entropy fluid near the blade surfaces. Blade suction can remove this fluid, lowering the entropy of the compressor throughflow, thereby avoiding a thermodynamic inefficiency, ultimately raising the compressor efficiency 0.25 percentage points for 1% flow suction. Blade suction also can reduce unwanted aerodynamic flow structures such as secondary flows and the tip clearance vortex. Low speed fan blade tip suction analysis using a three-dimensional viscous solver calculates a lower tip entropy and higher tip efficiency with fluid suction of only 0.2%. Implementation of blade tip suction on a high speed transonic compressor proved the possibility of blade tip suction. Results show strong effects on the upstream shock structure, including the disappearance of one shock wave entirely. Measurements downstream of the rotor indicate a change in the flow field exiting the suction blade rows, possibly due to a weaker tip vortex.