Single-Cycle Unsteady Nozzle Phenomena in Pulse Detonation Engines

Abstract

10.2514/1.22415 A quasi-one-dimensional, Euler model with detailed finite-rate chemistry is used to conduct a parametric assessment of nozzle area ratio effects on the single-cycle performance of a pulse detonation engine. Using results from the parametric study, design criteria are suggested for evaluating optimal contraction and expansion nozzle area ratios. In particular, the optimal expansion area ratio is shown to be well-predicted by using isentropic theory and the time-averaged, head wall pressure as the stagnation condition. To validate the parametric analysis, three nozzle sections are fabricated and tested in a single-cycle pulse detonation engine facility. Time-resolved thrust and specific impulse (I SP ) measurements are made for each nozzle and compared to simulated results. Additionally, schlieren imaging is used to investigate the blowdown gasdynamics in each of the three nozzles. Comparisons between simulated and measured impulse data are addressed using insights gathered from the flow visualization. Resulting analysis indicates that multidimensional wave phenomena are important in nozzles with converging sections. Overprediction of I SP by the model is attributed to deficiencies in accurately capturing the plateau pressure (P 3 ), as well as the inability to model the experimentally observed deflagration-to-detonation transition process. The relative contribution of each of these effects is quantified. Experimental measurements validate trends observed in the parametric study and reveal that an appropriately optimized diverging nozzle produces the largest single-cycle Isp.