Thermal Compensation of Piezoresistive Sensors to Facilitate Absolute Pressure Measurements in Rotating Detonation Engines

A methodology to account for thermal drift in piezoresistive (PR) pressure sensors is presented and applied to a rotating detonation engine (RDE). First, a modified Wheatstone bridge with a fifth-wire arrangement is introduced to determine the sensor temperature in real time. Second, sensor calibration is performed to account for sensor temperature effects on zero-offset voltage and sensor sensitivity. Sensor response at thermally steady and transient conditions is examined at varying initial heat flux inputs simulated by dry (air) and wet (molten salt bath) environments to demonstrate that a nonisothermal sensor can introduce significant errors. Finally, the calibrated sensor is installed in an annular RDE in a recessed probe configuration to measure the absolute wall pressure split into time-varying and steady components. Results show that the time-varying pressure measurements obtained by PR and piezoelectric probes agree spectrally, but the former detected higher pressure peaks because of its smaller sensing diameter. Thermal compensation vastly improved the accuracy of absolute pressure measurements, but further improvements are necessary to minimize thermally induced errors associated with the zero-offset voltage.