Effects of Fuel Concentration Gradient on Stabilization of Oblique Detonation Waves in Kerosene–Air Mixtures

Abstract

The transition structures and wave stabilization features of the wedge-induced oblique detonation wave (ODW) affect the combustion of the hypersonic air-breathing detonation engine, which is associated with the inhomogeneity of the inflow mixture. This study numerically investigates the influence of inhomogeneous kerosene–air mixtures on the stabilization of ODW for the first time, considering the inter-phase heat and mass transfers and focusing on the flow structure. The multiphase reacting flows are solved by the two-way coupling Eulerian–Lagrangian method. The inhomogeneous degree of fuel–air premixing is represented by the gradient of the liquid fuel equivalence ratio. A new pattern of transition wave structure from the shock-induced deflagration to oblique detonation is found. Under the fuel-rich condition before the shock-induced deflagration wave, a diamond-shaped wave structure is generated due to the large fuel concentration gradients. This flow structure is formed on the wedge without oscillations and is expected for a well-stabilized ODW. The initiation length of ODW is used to value the combustion performance. Its dependence on the inhomogeneous premixing degree displays a W-shaped curve. The chemical heat release influences the initiation length more obviously than the evaporative cooling in the fuel-lean conditions before the shock-induced deflagration. The ODW stabilization is enhanced by the heat released from the fuel-rich chemical reaction. Generally, the two-phase oblique detonation is determined by the competitiveness between the evaporative heat loss and chemical heat release. A uniform fuel–air mixture may not be optimal for detonation initiation based on the results of the present study.