Design optimisation of circumferential casing groove for stall margin improvement in a transonic compressor rotor

At off-design conditions, mass flow rate reduction below the compressor stability limit will result in rotating stall. In tip sensitive high speed compressors, the passage shock, tip leakage vortex and radial separation vortex are some of the known aerodynamic phenomenon that are linked to the accumulation of aerodynamic blockage near the casing. In the current study, a blockage parameter, (\psi), is introduced to identify and quantify blockage across the blade domain. The relation between aerodynamic blockage and casing groove stall margin improvement is investigated using numerical simulation. A Random Forest surrogate model is coupled with a Multi-Objective Genetic Algorithm optimiser to determine the optimum casing groove sizing and location that improves the compressor stall margin. The optimum groove has found to improve the stall margin by 2% with negligible efficiency penalty. This is about a 30% increase in mass flow reduction of the rotor when run with a smooth casing.