Experimental investigation on ammonia/hydrogen/air continuous rotating detonation

Ammonia has garnered international attention as an ideal carbon-free fuel. However, its poor combustion characteristics limit its widespread application. Continuous rotating detonation (CRD), fueled by ammonia, offers a novel approach to ammonia utilization. In this study, ammonia–hydrogen–air CRD experiments were first conducted in a hollow chamber. Propagation characteristics and flow field structure of ammonia–hydrogen–air CRD were analyzed through pressure measurement and top-viewed optical observation. The CRD wave propagates in the single-wave mode with a velocity of 1782 m/s, which accounts for 93.2% of the corresponding theoretical Chapman–Jouguet (C–J) velocity in the selected test. The analysis of the integral of chemiluminescence intensity (ICI) conducted on high-speed images confirms the coupling structure of the CRD wave. Increasing the hydrogen mass fraction (XH2) enhances the propagation velocity and peak pressure of the CRD wave while reducing its velocity deficit, which is attributed to improved combustion characteristics and a diminished deflagration proportion. Additionally, the analysis of high-speed images and ICI of their phase-averaged images indicates that the brightness and area of the reaction zone increase initially and then decrease with increasing XH2. Notably, a transition from a sawtooth-wave mode to a single-wave mode occurs as XH2 increases from 5% to 10%. As the nozzle contraction ratio (CR) increases from 2 to 8, the peak pressure of the CRD wave decreases, and the reaction zone becomes less compact. At CR = 8, the significantly lower peak pressure causes the CRD wave to approximate a sawtooth-wave mode.