Numerical Study of Hydrogen Injection to initiate Oblique Detonation Wave

With the motivation of operating scramjet in shock induced combustion ramjet (shcramjet) or oblique detonation wave mode, the current study aims to develop strategies for non-premixed oblique detonation wave configuration using numerical simulations. The unsteady two-dimensional Reynolds Averaged Navier-Stokes with reactive multi-species equations are solved using adaptive grid refinement and robust SAGE solver on CONVERGE-CFD platform with detailed chemical kinetics. The sonic hydrogen injection cases (ϕ = 0.5) into incoming air flow at Mach 7 with pressure of 40 kPa and temperature of 300 K are simulated for 2 ms duration. The computational domain consists of finite length wedge (100 mm, θw = 26◦ as well as hydrogen injection tube upstream of wedge starting point, to obtain non-premixed
oblique detonation wave. The unsteady detonation wave patterns are obtained for angle of injection (AOI) 15◦ with injector location at (Dj=) 30 mm from wedge tip. It is found that various flow features, such as jet-shock, shear layer and hot burnt zone near the wedge wall affect the lifted detonation wave starting at the interaction point of shear layer and hot burnt zone. The detonation wave momentarily transition to deflagration flame and re-establish itself as detonation wave multiple times. The angle of injection (AOI) and injector locations are varied to obtain various patterns of unsteady non-premixed oblique detonation wave and it was found that AOIs below or close to wedge angle lead to formation of unsteady oblique detonation wave, while AOIs higher than the wedge angle lead to formation of stable stretched deflagration flame. Injection location very close to wedge starting point leads to multi-cycle detonation to deflagration transitions and deflagration to detonation transitions. The overall thermal and combustion efficiencies are also compared with equivalent premixed hydrogen-air oblique detonation wave at same wedge angle.