Impact of Rotational Speed on the Discharge Characteristic of Stepped Labyrinth Seals

Abstract

Current and future gas turbine engines are subject to increasing performance requirements and improved fuel efficiencies. The resultant engine cycles increase core flow temperatures requiring additional cooling flow while requiring a reduction in parasitic leakage by more than 25% to meet the performance goals. The achievement of the reduced leakage requires that seal design concepts be tested and improvements validated in engine like conditions before they are introduced into the actual engine. A previous paper [1] described a set of rotating seal designs that have been tested in various combinations of rotating and static design features for low leakage potential. This paper is a continuation of the previous effort and focuses in particular on the effect of rotational speeds on the discharge characteristic of various stepped labyrinth seal designs. Leakage reductions will be characterized in terms of CD/DD,0 (i.e. ratio of leakage rate with rotation over leakage rate without rotation) as a function of circumferential to axial through flow velocity, U/Cax. For large velocity ratios of U/Cax > 5, leakage reductions of more than 20% were observed. Experimental data are compared with literature [2].