Transducer Installation Effects on Pressure Measurements in Pressure Gain Combustion Devices

摘要

Pressure gain devices such as rotating detonation engines present an extremely harsh environment, generally precluding the use of any intrusive probe measurement. The most widely used diagnostic is the measurement of high frequency pressure which can be used to determine the pressure amplitude, number of waves and their direction and the wave structure. The preferred approach for making pressure measurements is to install the sensing element flush with the combustion chamber wall, but is almost always inhibited by the extremely high heat fluxes that can damage the sensor. Alternately, recessed cavity or infinite probe installation is seldom used for high frequency pressure measurements. While amplitude attenuation and phase distortion of the pressure signal can be introduced by these installation types, its characterization in the presence of high amplitude steep fronted pressure waves encountered in PGC devices has not been previously performed. In the current work a highly modular calibration test-bed is designed to enable characterization of pressure transducers based on their installation in the presence of steep fronted high amplitude pressure waves. Two transducer types, piezoelectric PCB® 113B26 and water-cooled piezoresistive Kulite® WCT-3121VI were used and installed in the flush, recessed cavity and infinite tube probe configuration. The recessed cavity probe showed 5-26% amplitude attenuation and almost negligible time lag compared to the flush transducer, the infinite tube pressure (ITP) transducer showed a significantly higher delay and as much as 50% reduction in measured pressure amplitude. Secondary wave features from reflections within the test article, that were captured by the flush and recessed cavity transducer were damped by the infinite probe measurement.