Suppression of premature ignition in the pre-mixed inlet flow of a shcramjet

This thesis addresses premature ignition in the inlet of a shock-induced combustion ramjet (shcramjet). A cantilevered ramp injector maintains a buffer region between the hydrogen fuel and the boundary layer only until the final 15% of the inlet where substantial premature ignition occurs. Both gaseous nitrogen and additional hydrogen are then injected using various geometries and inflow conditions in an attempt to suppress the flame. Premature ignition is suppressed most feasibly by the injection of additional hydrogen through a backwards-facing step located just before the second inlet shock, such that the global equivalence ration of the pre-mixed flow exiting the inlet is one. The mixture is further subjected to shock-induced combustion where the combustion region required for maximum heat release is less than 20% of the inlet length. Numerical simulation predicts a fuel specific impulse of 700 seconds for this preliminary shcramjet engine.