Shock tunnel experiments on oxygen enrichment in a hydrogen fuelled scramjet

Extension of scramjet operation into the hypervelocity regime (u > 3 km/s, M > 10) is critical for their use in access-to-space systems. As flight speeds increase, the net thrust of a scramjet engine is limited by increased fuel/air mixing length requirements, as well as the decreased ratio of energy available from stoichiometric fuel/air combustion relative to the specific kinetic energy of the captured air. One possible method for addressing these issues, known as oxygen enrichment, involves the premixing of oxygen with fuel before injection. This method provides a head start for mixing and also allows the possibility of fuel combustion at greater than stoichiometric proportions. This paper describes some exploratory shock tunnel experiments involving oxygen enrichment of gaseous hydrogen fuel in a scramjet at hypervelocity conditions. These experiments were conducted in a simple rectangular duct with a central strut injector and varying levels of enrichment. The measured pressure distributions show a positive effect of enrichment and indicate how this technique could be best used to extend the performance of hypervelocity scramjets to higher flight Mach number