Investigations on the Aerodynamic Performance of a Gas Turbine Exhaust Diffuser With the Modified Shell Profile

Abstract

Abstract In this paper, a shell profile design method based on diffuser flow area curve is proposed to improve the static pressure recovery coefficient of the exhaust diffuser over a range of inlet swirl angles. Based on verifying the reliability of the numerical method, the paper first explored the aerodynamic performance of the exhaust diffuser with the original structure and the modified structure by solving three-dimensional Reynolds-Averaged Navier–Stokes. Numerical results well capture the pressure distribution and flow characteristics in the exhaust diffuser. The numerical results show that the shell profile modification method effectively improves the aerodynamic performance of the exhaust diffuser. Compared with the original exhaust diffuser, the secondary vortex near the outer shell of the modified exhaust diffuser is weakened and the axial reverse pressure gradient near the strut is reduced. The static pressure recovery coefficient of the modified exhaust diffuser is significantly increased under different inlet swirl angles. Especially, under the normal working condition with a medium swirl angle (22 deg), the static pressure recovery coefficient increases by 0.034 with a relative increase of 7.6%. Under the extreme working conditions of a large swirl angle (35 deg), the static pressure recovery coefficient increases by 0.074 with a relative increase of 39%. A test rig for measuring the aerodynamic performance of the exhaust diffuser was built, and the validity of the shell profile design method is further verified through experimental measurements.