Evaluation of pulse detonation engine modeling using laser-based temperature and OH concentration measurements

Abstract

Two novel, laser-based sensors employing ultraviolet (UV) wavelengths are developed and applied to measure time-resolved temperature and OH concentration in a pulse detonation tube. These results, along with pressure data, are employed to evaluate two computational simulations utilizing different chemistry and heat transfer models to predict pulse detonation engine (PDE) flowfields. The first sensor applies 266 and 306 nm UV laser absorption to infer temperature from 2000 to 4000 K because of broadband CO 2 absorption. These results represent the first thermometry based on line-of-sight, cw UV laser absorption by CO 2. The second sensor utilizes a single 306 nm UV laser to probe an individual OH absorption feature. Time-resolved OH concentration is inferred from the measured absorption, temperature, and pressure. These two sensors provide microsecond time-resolved measurements, over a dynamic range of temperatures and pressures (2000–4000 K and 0.5–30 atm), of two important parameters needed for evaluation of PDE computational models. The first computational model evaluated utilizes a frozen gas composition assumption; the second model incorporates finite-rate chemistry and includes losses due to heat transfer and friction. The results show that the frozen gas composition simulation can successfully predict temperature and pressure profiles, although the agreement is artificial in that inclusion of heat transfer effects would negate this agreement. The simulation including finite-rate chemistry and no heat transfer overpredicts the measured temperature and OH concentration. However, with the proper inclusion of losses due to heat transfer, the finite-rate chemistry code accurately predicts all three measured parameters. We conclude that both finite-rate chemistry and heat transfer are important for correct modeling of PDE flowfields.