Efficacy of High-Speed Strain Gauge Measurements in Analysis of Rotating Detonation Combustors

Experimental results are presented for the use of a high-speed, piezoelectric strain sensor to assess the acoustics and detonation strength in a Rotating Detonation Combustor (RDC). Strain sensors are used as a novel, non-intrusive tool to measure acoustics and pressure values inside a RDC. Strain readings are related to chamber pressure through a hoop stress simplifications; Computed pressure traces are compared against traces from flush-mounted MHz dynamic pressure sensors. Both sensors utilize the piezoelectric effect to measure their respective properties. The pressure sensors can accurately sample up to 500 kHz while the strain gauge can sample up to 100 kHz, both greatly exceeding the Nyquist rate for the instabilities observed in the RDC used for this study. Through comparative analysis, strain sensors are evaluated as a tool to determine the detonation wave speed, measure extemporaneous acoustics, and quantify the wave strength through peak pressure. Initial findings indicate that the frequencies observed by the strain sensor very closely resemble chamber pressure fluctuations, while its use as a tool to quantify wave strength will require further study.