Experimental study on upstream pressure characteristics of rotating detonation engine with methane and oxygen-enriched air

Abstract

The interaction mechanism between the rotating detonation engine (RDE) and its upstream is one key issue that needs to be explored when considering its application. In this study, experimental tests with methane and 50% oxygen-enriched air are conducted to investigate the relationship between upstream pressure characteristics and the detonation wave. As a result of operational considerations, a hollow chamber and a rear ignitor are used and the initiation process is discussed. Upstream pressure characteristics are analyzed under varied injection pressures and equivalence ratios. Stable modes including single-wave and double-wave modes are recorded in most cases. Notably, two unstable modes are also captured at low injection pressure in which the detonation quenches quickly. The results highlight that significant feedback pressure pulsations synchronize with the rotation frequency of detonation waves after ignition due to the upstream oblique shock wave (UOSW). But the inherent frequency of injection should also be emphasized at elevated injection pressure. The detonation wave can also cause injection blockage, particularly at low injection pressure, leading to the bifurcation of unstable mode. Such unstable is attributed to an inadequate upstream pressure increase after ignition, which hinders the injection reconstruction. Further analysis reveals that higher injection pressures or lower equivalence ratios diminish the differential between the detonation wave and upstream pressure, and consequently, the pulsation amplitude. An increase in the detonation wave number can also reduce the pulsation amplitude, which can even be lower than 10% in a double-wave mode. The results are beneficial for integrating RDE and its upstream components.