Nonintrusive Gas-Turbine Engine-Exhaust Characterization Using Acoustic Measurements

Abstract

This paper reports exhaust measurements performed using a nonintrusive acoustic technique on a JT15D-1A turbofan research engine. Using multiple streamwise displaced microphones, the integrated exhaust velocity and static temperature were measured simultaneously in engine flows with bypass Mach numbers up to 0.48. A Kiel pressure and K-type thermocouple probe was used to assess the accuracy of the acoustic measurements. The Integrated velocity and static temperature rms errors of and 2.3 K were identified. Using probe-based measurements at a low engine power setting, two calibration constants were identified for conversion from integrated flow parameters to mass flow and thrust. Applying the calibration constants to the acoustic measurements, and 200 N rms errors in mass flow and thrust were observed. These promising results indicate that the acoustic technique may be used to characterize and monitor gas-turbine engine performance. To the authors’ knowledge, this is the first time a nonintrusive acoustic technique has been used to characterize engine flows with Mach numbers greater than 0.3.