Three-dimensional, numerical investigation of reactant injection variation in a H2/air rotating detonation engine

• Reactant mixing within a rotating detonation engine is characterized.
• Initial mixing occurs from a counter-rotating vortex pair in the injection zone.
• Optimized fuel injection distribution exists that provides the greatest mixedness.

This study characterizes the mixing performance and non-reacting injection flow field within a rotating detonation engine. Initial reactant mixing is accomplished through a counter-rotating vortex pair developing from a jet-in-a-crossflow situation. Radially injected air wraps around the fuel jet, shearing the hydrogen into the vortex structure. The three-dimensional baseline geometry produces poor hydrogen/air mixing in the injection zone due to low fuel penetration into the wide, cross-flowing air stream and low air entrainment into the vortex structure. Injection parameters, including reactant flow rate, injection area, and fuel injection distribution, are varied to assess the impact on mixing. Decreasing air injection area and fuel injection area improve fuel penetration into the air stream and the vortex mixing mechanism, enhancing the level of mixedness within the annulus. For a given air injection area, an optimized number of fuel injection holes exists that provides the greatest level of mixedness. Variations from the optimized geometry reduce the effectiveness of the vortex mixing mechanism. Staggering fuel injection holes produces a decrease in mixedness when compared to collinear fuel injection.