Thermal compensation in recessed piezoresistive probes to improve absolute pressure measurements in rotating detonation engines

Piezoresistive (PR) probes can provide absolute pressure measurements, but their practical use in rotating detonation engines (RDEs) has been hindered by the harsh thermal environment of the combustion chamber. In general, the probe must be recessed to protect it from intense thermal loading of the RDE combustor. Although probe recess safeguards the hardware, measurements are subjected to thermal drift, in addition to signal attenuation, phase shift, and resonance. In this study, four different recess probe mounts are investigated experimentally in an RDE to account for the thermal drift in PR probes. A modified Wheatstone bridge is used to measure the sensor temperature during the test, and a steady-state methodology is employed for thermal compensation. Results show that all probe mount configurations provide time-varying pressure measurements with good accuracy, although pressure attenuation is greater with a smaller port diameter. The study identified that absolute and/or time-averaged pressure measurements incur large errors in a non-isothermal probe during the RDE test. Accurate absolute pressure measurements by PR pressure probes can be obtained in RDEs, but it requires a probe mount to ensure an isothermal probe during the test.