Investigation of the evolution process and propulsion performance of the longitudinal pulsed detonation in rotating detonation combustors

Abstract

An investigation of the evolution process and propulsion performance of the longitudinal pulsed detonation (LPD) is conducted by numerical method in this study. Four computational models, model A–D, of different sizes are applied. A typical “deflagration surface–fast deflagration–LPD–forward shockwave” process of evolution is found for the duration of the LPD, and the LPD is intuitively triggered by the reflected shockwaves. Low injection pressure ratios (PRs; i.e., PR = 1.1–1.3) and combustors with a low length-to-height ratio (L/H) are found to be conducive to the sustenance of the LPD. In addition, based on the knowledge of the inherent acoustic resonance frequency, the sustainable LPD frequency is estimated. When the PR increases, the LPD frequency tends to decrease in the same model. In the evolution process of fast deflagration-LPD, the wave speed increases gradually, which is in good agreement with the previous study. In the propagation process of the forward shockwave, the wave speed increases in general, which is because the pressure difference between the combustor and the outlet accelerates the wave propagation. The propulsion performance of the LPD is also investigated. As the PR increases, the specific impulse Isp of all the four models increases in general. The Isp of the LPD is relatively low compared with that of the rotating detonation mode, and when realizing industrialization of the LPD-based engines, an LPD mode with higher work efficiency needs to be explored. We hope this study of the enlightening LPD mode can provide a foundation for the ensuing application of detonation-based engines.