Time-resolved, single-ended laser absorption thermometry and H2O, CO2, and CO speciation in a H2/C2H4-fueled rotating detonation engine

Abstract Rotating detonation engines (RDEs) require novel diagnostic tools to better understand complex detonation behavior and improve performance. To this end, a single-ended laser absorption sensor for in situ, time-resolved measurements of temperature, H2O, CO2, and CO concentrations has been developed and deployed within the annulus of a hydrogen/ethylene/air-fed RDE. With a measurement rate of 44 kS/s, the sensor delivers four co-aligned, mid-infrared laser beams into the annular detonation chamber and captures the back-reflected radiation through a single optical port. A ray-tracing optimization algorithm, designed to maximize signal-to-noise ratio and beam-perturbation tolerance, was used to determine the optimal sensor optical configuration. Wavelength-modulation spectroscopy (WMS) further compensated for interference sources in the harsh detonation environment. Time-resolved and time-averaged sensor measurements of gas temperature and species at equivalence ratios of 0.74, 0.87, and 1.03 are presented.