Analysis of transient thermal choking processes in a model scramjet engine

Shadowgraph how visualization and door static pressure measurements have be en used to examine the transient behavior of a thermally choked combusting flow. Experiments were performed to examine the effect of varying inlet Mac h number and fuel-air equivalence ratio on the nature and extent of the int eraction, In all cases a sudden increase in static pressure was measured, f ollowed by a highly turbulent region of sonic how that was seen to propagat e upstream along the duct. The nature of the dominant processes causing thi s pressure discontinuity are still not certain. Some mechanisms that may co ntribute to this phenomenon are presented. These include separation of the boundary layer in the duct, formation of a detonation, and formation of a n ear-normal shock wave by the region of thermally choked flow.