Mechanism Of Coanda Effect In The High Mach Number Turbine Cascade

Coanda effect has been applied to the reserch of internal flow and gets goodresults in low Mach number compressor and turbine cascade. At supersonic workingconditions, the Coanda jet and main flow detach the Coanda surface early due to theshock wave in the flow passage and cause high losses. In high Mach numbercompressor, it has been confirmed that blowing jet both at the suction and pressuresurface obtained better fluid deflection than single jet results. Therefore, based on aturbine guide vane cascade, double jets structures were contructed and simulated inthis paper. Higher aerodynamic performances at high subsonic and supersonicworking conditions are expected.This paper conducts a two-dimensional numerical simulation usingcommercial software ANSYS CFX with high pressure turbine guide vanes as theprototype. The aerodynamic performance of the prototype cascade is analyzed first.Then a jet slot is designed at different trialing edge positions on the pressure surfac eon the basis of three kinds of circulation control cascade with a Coanda jet anddifferent curvatures of Coanda trialing edge respectively. Every circulation controlcascade was simulated at three exit conditions with the cascade exit Mach numberbeing0.6,0.85and1.1. The influence of adding the jet at pressure surface to theaerodynamic performance and flow situation of the turbine cascade was explored.The numerical results of circulation control cascade with double jets show that:when the exit Mach number is0.6, double jets cascades obtain higher exit flowangle and higher expansion ratio than the single jet cascade, but the energy losscoefficient increases. Appling double jets improves the jet attached to the wallresults; At Mach number0.85, Coanda jet attaches to the wall well enough at singlejet condition. Adding the pressure jet interferences the flow field and causesaerodynamic performance degradation. At supersonic, exit flow angles of everycirculation control cascade increases obviously when the pressure jet is added. Theshock wave occurs latter in double jets cascades than that in single jet ones.