The influence of confined channel configuration on the detonation waves induced by hot jet under supersonic pulsating flow

Abstract

The detonation engine combustion chamber represents a typical confined channel, whose operational stability is significantly influenced by the coupling effects between complex inlet shock structures and combustion chamber backpressure fluctuations. Based on supersonic pulsating inflow simulating practical conditions, this work delves into detonation propagation characteristics and mechanisms through examining three confined channel configurations: rectangular channel, expanding channel, and cavity-coupled expanding channel. Numerical calculations are performed using a hybrid sixth-order weighted essentially non-oscillatory centered difference scheme and a one-step, two-species hydrogen-oxygen finite-rate chemistry model. The results reveal that, compared to the rectangular channel, the expanding channel exhibits enhanced disturbances, generating separated oblique shock waves. These shock waves reduce the detonation wave length and stability, leading to severe attenuation in later stages. In the cavity-coupled expanding combustion chamber, pressure oscillation waves advance the initiation time and increase both propagation time and distance, thereby enhancing detonation stability through intensified shock reflections and unburned gas mixing. Notably, increasing the cavity length strengthens the pressure oscillation waves and widens the subsonic channel ahead of the cavity. However, when the length-to-depth ratio exceeds 2.5, flow field instability induced by bifurcated unburned jets is identified as causing abnormal detonation wave recession. Therefore, optimizing the length-to-depth ratio to 2.0–2.5 achieves a balance between stability and structural compactness, maximizing performance benefits. The findings support optimized combustion chamber designs for detonation-based propulsion systems.