Aerothermal Investigation of Seal Teeth Cavity Leakage Flow in a Supercritical CO2 Compressor

The aerothermal performance of the seal teeth cavity leakage flow and its effect on the axial supercritical CO2 compressor are described. The seal teeth cavity flow deteriorates the performance of an axial supercritical CO2 compressor, and the effect of the shrouded stator configuration is demonstrated by comparing to a cantilevered stator configuration ( without cavities). A Three stage, 9.0 MW compressor has been designed and is planned for testing in 2023. The detailed computational fluid dynamics simulations have been performed using both Non-linear Harmonic (NLH) and mixing plane assumptions. For mixing plane calculations, different rotor/stator configuration were run and compared.For a shrouded stator configuration, the low momentum leakage flow enters the cavity downstream of the stator trailing edge due to the pressure differential, and comes out and enters in the main flow just upstream of the stator. This causes the boundary layer to change in that region which degrades the performance of the stator and the effect is seen further into the downstream rotor. Vortical flow structures are seen in between seal teeth and also at the upstream and downstream cavity connections which modifies the flow angles entering and exiting the cavity and has undesired effect in compressor performance. Shear work is also done on the leakage flow while passing through the small seal teeth gap which increases the total temperature of the cavity flow. When this flow is entrained in the main flow, total temperature is seen to rise around the hub region of the rotor inlets as well.