TRANSONIC COMPRESSOR DARMSTADT OPEN TEST CASE: EXPERIMENTAL INVESTIGATION OF STATOR SECONDARY FLOWS AND HUB LEAKAGE

Abstract

Abstract Smaller core engine result in highly loaded stages with increased relative tip gaps and leakage flows, which cause a reinforced influence of secondary flow phenomena. This paper experimentally investigates the secondary flow effects in the 3D-optimized shrouded stator of the TUDa-GLR-OpenStage, representative of a transonic high-pressure compressor front stage, and its susceptibility to hub leakage flows. The impact of stator hub leakage is investigated from subsonic to nominal transonic operating conditions. Five-hole probe and time-resolved virtual multi-hole probe measurements at different operating conditions are conducted to investigate the underlying loss mechanisms. The leakage mass flow is determined using the pressure difference within the fin seal. Steady results show that the optimized 3D stator effectively suppresses the hub corner separation compared to the predecessor 2D stator, but its performance is further limited by a near-tip separation. With the increased stator hub leakage (at a leakage-to-main flow ratio of about 0.4%), the compressor isentropic efficiency generally drops (by about −0.5%) at the full operating range due to an enhanced hub corner separation effect. However, the leakage also helps alleviate the tip-corner separation when operating near stall, leading to a smaller efficiency penalty under these conditions. Unsteady results reveal the sensitivity of transient compressor performance to the passing rotor wake, but limited interaction between this phenomenon and the increased leakage is observed. These findings provide insight into the stator hub leakage-related penalties on the compressor aerodynamics efficiency.