Application of image based measurement techniques for the investigation of aeroengine performance on a commercial aircraft in ground operation

Abstract

The investigation of the flow and sound field upstream and downstream of a full scale aeroengine is aimed at providing important reference data required for reliable modeling and prediction. In this regard a wide variety of contactless and non-invasive laser optical and acoustic measurement techniques have matured in recent years to allow their application on full scale aircraft. Within a measurement campaign involving an Airbus A320 DLR research aircraft inside a sound-attenuating hangar at Hamburg Airport, four image-based measurement techniques were applied in parallel to acquire data for the engine operating at varying conditions: stereoscopic PIV of the engine intake and jet exhaust flow, high frame rate BOS of the exhaust jet in combination with acoustic array measurements, IPCT/PROPAC technique for the measurement of fan blade deformation under load and MODE measurements for nacelle position monitoring. The objective of the ground tests was to establish a combined measurement data base to locate the zones within the engine jet exhaust flow where large, turbulent fluctuations in velocity and density produce noise. Simul-taneous application of PIV, BOS and acoustic array techniques were carried out in front and behind the left aircraft jet engine, for the characterization of inlet flow disturbance due to ground vortex formation, the turbulent free jet flow field as well as engine’s core and jet noise. The installed ground test instrumentation was operated in parallel to facilitate a simultaneous acquisition of various flow field parameters using different diagnostic approaches (instantaneous velocity, sound pressure and fluctuation, density fluctuations and fan blade deformation). The diagnostics were applied non-invasively to the aircraft and aeroengine, that is, the ground test hardware neither required modifications to the aircraft airframe or engines nor had any direct connection to the aircraft which significantly eased the certification and test approval procedure. Nonetheless parts of the test equipment had to be installed within the danger (safety) area of the engines and required numerous certification and approval steps. The paper focuses on the implementation and use of the laser optical measurement techniques PIV and BOS in this challenging, full scale application.