Detailed Unsteady Simulation of a Counterrotating Aspirated Compressor with a Focus on the Aspiration Slot and Plenum

Robert D Knapke,Mark G Turner

doi:10.1155/2013/857616

Abstract

An unsteady analysis of the MIT counterrotating aspirated compressor (CRAC) has been conducted using the Numeca FINE/Turbo 3D viscous turbulent flow solver with the Nonlinear 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. The aspirated isothermal boundary condition solutions provide the most accurate representation of the trends produced by the experiment, particularly at the endwalls. These simulations provide significant insight into the flow physics of the aspiration flow path. Time histories and spanwise distributions of flow properties in the aspiration slot and plenum present a flow field with significant temporal and spatial variations. In addition, the results provide an understanding of the aspiration flow path choking mechanism that was previously not well understood and is consistent with experimental results. The slot and plenum had been designed to aspirate 1% of the flow path mass flow, whereas the experiment and simulations show that it chokes at about 0.5% mass flow.

Highlights

E overall goal during the design process of a gas turbine engine is to reduce speci c fuel consumption for a given level of thrust
An example of the convergence history from initialization to Nonlinear Harmonic (NLH) convergence is presented in Figure 9. e PPbb values are the main passage exit pressures, with 155 kPa being the Run 13 value. e ne grid level corresponds to the grid presented in Table 2. e oscillations of mass ow for the NLH simulations were less than 0.5% of the inlet mass ow, which was considered acceptable for convergence. e mass ow discontinuity across the NLH interface boundaries was within the mass ow variations during convergence
Unsteady simulations of the counterrotating aspirated compressor (CRAC) compressor have been conducted using the FIN urbo D viscid turbulent ow solver with the Nonlinear Harmonic method. e aspiration slot and plenum were included in the computational domain

Summary

Introduction

E overall goal during the design process of a gas turbine engine is to reduce speci c fuel consumption for a given level of thrust. For these reasons both adiabatic and isothermal solid wall boundary conditions were simulated for the aspirated case. E small increase in mass ow for the aspirated simulations, when compared to the experiment, corresponds to the low pressure ratio and 103% rotor speeds.

Results

Conclusion