Experimental study on effect of air injection slot width on rotating detonation of high-temperature hydrogen-rich gas

The objective of this study is to evaluate the effects of air injection slot widths on the propagation characteristics and modes of the rotating detonation wave (RDW) of high-temperature hydrogen-rich gas. The high-temperature hydrogen-rich gas obtained by pre-combustion of hydrogen and oxygen was used as fuel, and air was used as the oxidant. Experimental studies were carried out under different equivalence ratios and the slot widths of the air injection. The results reveal that there were four propagation modes in rotating detonation combustor: two-wave collision mode, mixed mode, stable single-wave mode, and unstable single-wave mode. For slot widths of 1.5 and 2 mm, the RDW exhibited relatively high average peak pressure and propagation stability; in contrast, when the slot width was 2.5 mm, the RDW propagation was unstable. Furthermore, as the slot width increases, the RDW velocity first increased and then decreased. In all cases, the highest RDW velocity was 1510 m/s when the slot width was 1.5 mm, and the equivalence ratio was 1.28. During the two-wave collision process, the collision position of the RDW would deviate. This was primarily due to the difference in the strength of the two RDWs; thus, one of the RDWs had a higher propagation velocity than the other.