Particle Image Velocimetry Measurements of Unsteady Exhaust from a Linearized Continuous Detonation Combustor

Abstract

Particle image velocimetry (PIV) data were used to evaluate unsteady exhaust flows from a linearized detonation combustor in this work. The objective of this research is to better understand the unsteadiness of exhaust flows caused by combustion-supported continuous waves, which are common in continuous detonation combustors and are crucial for the design of downstream detonation engine components. During the experiments, self-excited periodic combustion waves were established in the linear combustor, displaying shuttling transverse wave mode and longitudinal pulsed wave mode with a mixture of ethylene, air and oxygen under different injection settings. A two-dimensional double-frame PIV system was used to diagnose the exhaust flows immediately downstream of the combustor outlet with a sampling rate of 1 kHz. To evaluate the impact of propagating combustion waves on exhaust flow unsteadiness, statistical investigations of instantaneous exhaust flow fields were performed. The results demonstrate that the exhaust flows of the linear detonation combustor are predominantly subsonic, with inhomogeneity mostly in the transverse direction for the shuttling transverse wave mode and in the longitudinal direction for the longitudinal pulsed wave mode. Furthermore, transient sonic flows for the longitudinal pulsed wave mode were created with the impulse of combustion wave. According to the findings, for optimal energy harvesting from continuous detonation, both the portion of transverse exhaust flow component and the exhaust flow unsteadiness should be properly addressed.