No abstract

No abstract

No abstract

The mixing flowfields of transverse walled fuel injection with and without the guidance of a fin in a Mach 2.2 flow were experimentally characterized and compared. This study evaluated the ability of fin-guided injection to enhance fuel-air mixing while reducing shock-induced stagnation pressure losses. The nonreacting gaseous injection experiments used helium as a hydrogen surrogate and simulated four mass flow rate conditions to investigate the performance of the proposed injection scheme with variable jet momentum. The analysis of schlieren visualizations demonstrated a 100-200% increase in jet penetration for the fin-guided cases over the baseline 12 diameters downstream of the injection point. Wall pressure measurements were correlated to the schlieren results which showed that the strength of the jet-induced shock in the baseline was reduced by 33-47% by using the fin. A planar-Mie scattering method used to obtain cross-sectional views of the injection flowfields revealed that the fin was not only responsible for raising the fuel jet away from the wall but also enabled its vertical spreading. The present results demonstrate that this fin geometry can enhance mixing via increased penetration and spreading, reduce the strength of jet-induced shocks, and potentially displace the reaction zone away from the combustor wall. Nomenclature A = area D = injector orifice diameter h, l, w = height, length, and width, respectively J = jet to freestream momentum ratio M = Mach number _ m = mass flow rate P = pressure Re = Reynolds number r = injector orifice radius T = temperature u = velocity x, y, z = x, y, z coordinate directions, respectively Δ = Delta δ = shock deflection angle ρ = density τ = tunnel steady-state time 0 = stagnation condition Subscripts B, F = baseline and fin guided, respectively blo = blockage, for blockage area inj = injector j = jet p = injector proximity ts = test section 1 = condition upstream of jet-induced shock 2 = condition downstream of jet-induced shock 3 = combustor inlet condition ∞ = freestream

An experimental investigation was performed to characterize liquid fuel injection into a Mach 2.1 airflow simulating a scramjet combustor flowfield. In particular, ethanol fuel penetration and dispersion characteristics were compared for a transverse injection configuration with and without a mixing enhancement fin. In previous studies involving gaseous fuel, the fin-guided injection not only improved turbulent mixing but also served to reduce the stagnation pressure loss associated with the fuel injection shock. To characterize the mixing between liquid fuel and air, laser-sheet visualization of the cross-sectional view and schlieren visualization of the side view were obtained at various time intervals. Wall pressure measurements along the axial direction were used to help interpret the visualization data. The side views of fuel injection revealed that the fuel penetration height in the near-field was two-to six-times greater with the fin-guided injection. Also, downstream evolution of the liquid-fuel cross-sectional area suggested a greater vaporization rate associated with the fin-guided injection. The present results showed a significant improvement in key injection parameters and mixing characteristics associated with fin-guided liquid-fuel injection.