Numerical and experimental study of fuel pre-injection in the inlet of a high-velocity air-breathing engine

The effect of preliminary injection (pre-injection) of a gas (heated air, methane, or ethylene) ahead of the entrance of a three-dimensional inlet in a supersonic flow with Mach numbers $\mathrm{M}_\infty=2-4$, stagnation temperature $T^*=300$ K, and flow rates of the injected gas corresponding to $0$–$6\%$ of the flow rate of air through the inlet is numerically studied. The gas is injected through orifices located behind the end faces of pylons mounted upstream of the inlet entrance. The computations are performed by the ESI-FASTRAN software package, which allows one to calculate three-dimensional viscous turbulent gas flows by a time-dependent method with the use of the Reynolds-averaged Navier-Stokes equations. Experimental investigations of pre-injection are performed with the use of small-scale and large-scale inlet models at $\mathrm{M}_\infty=3-4$ and $6$. A positive effect of pre-injection on stable (without stalling) deceleration of the incident flow in the case of mass supply and on initiation of ignition and stable combustion in the combustion chamber is confirmed.