Inlet/Compressor System Response to Short-Duration Acoustic Disturbances

Abstract

Recent studies have shown that computations of unsteady high-speed inlet flows produce results that strongly depend on the compressor-face boundary condition. Traditionally applied boundary conditions have no experimentalverification, which leads to uncertainty and significant risks in development programs. Experimental information is offered that can serve as a basis for constructing realistic boundary conditions. Short-duration transients were investigated in a constant-area circular inlet attached to an operating high-speed, single-stage, axial flow compressor. The transients were initiated by the generation of short-duration acoustic pulses within the inlet, using an exploding wire method. Pulse duration was typically 2 ms, with a peak amplitude of 3% of the mean inlet static pressure measured at the compressor face. Fast-response wall-mounted pressure transducers were used to detect the incident, reflected, and transmitted pulses. Data were obtained for axial compressor-face Mach numbers from 0.15 to 0.45. Frequency-domain analysis was used to extract dimensionless transfer functions that may be viewed as frequency-resolved reflection and transmission coefficients. The information is appropriate for the characterization of the compressor face for computational purposes. None of the customary boundary conditions predict the data obtained in this study, highlighting the need to revise conventional methods of imposing outflow boundary conditions.