Unsteady Simulations of a Counter-Rotating Aspirated Compressor
An unsteady analysis of the MIT counter-rotating aspirated compressor (CRAC) has been conducted using the Numeca FINE™/Turbo 3D viscous turbulent solver with the Non-Linear Harmonic (NLH) method. All three blade rows plus the aspiration slot and plenum were included in the computational domain. Both adiabatic and isothermal solid wall boundary conditions were applied and simulations with and without aspiration were completed. Comparison of the aspirated case with data is good. When compared to the adiabatic boundary condition, the isothermal boundary condition solutions showed improvements in predicting stage performance, most notably at the endwalls. The aspiration has a significant impact on the flow field and provides a 4.2% increase in efficiency over the non-aspirated case. Although the slot and plenum had been designed to aspirate 1% of the inlet mass flow, the experiment and simulations show that it chokes at about 0.5%. Details of the aspiration flow path choking mechanism, which was previously not well understood, are presented.