Numerical Investigation of Compressor Tandem Aerofoils Featuring Near-Endwall Modification

A highly loaded 1.5-stage low-speed compressor stage is investigated numerically using fully turbulent and steady state RANS simulations. The tandem stator at the end of the stage is replaced by a tandem stator with a near-endwall modification. This unconventional compressor blade design is using a single profiling near both endwalls and a tandem profiling at midspan. Using this modification the positive behaviour of a tandem stator can be maintained. Locally the leading edge of the rear vane and as a result the gap flow near both endwalls will be removed by introducing a single-profile segment. This paper will describe the approach to set up a numerical model for the new geometry and will characterize the flow features and loss mechanisms of the near-endwall modification. The first comparison between the stators with and without near-endwall modification, showed a reduction of corner separation at the rear vane, caused by the removal of the low momentum gap-flow. On the other side, the near-endwall modification is creating higher losses at the connecting region between the tandem and single segment. The numerical results presented in this paper will be the starting point for further optimizations of the tandem blade with near-endwall modifications.