Investigation on Unstart Phenomena Induced by Heat Release in a Model Scramjet

An experimental investigation on a model scramjet is conducted in a hypersonic arc-heated wind tunnel at Mach 4.5. Unstart phenomena induced by heat release in the model is investigated by injecting ethylene in the supersonic air coming through the model duct. By Ineans of high speed schlieren flow visualization completed by image processing, a dominant frequency of 1000 was resulted for three main features in flow domain including inlet nonnal shock, Barrel shock and shear layer region. The decrement of mass flow rate due to flow spillage at the inlet lip was observed during the unstart phenomena induced by heat release. By means of image filtering andcross-correlation between certain intensity distributions of schlieren images, the phase difference between these phenomena were calculated. The main cause of unstart isrevealed to be the localized thermal checking in the region of shear layer diffusion domain which is almost synchronized with the inlet normal shock oscillation.

Keywords:

Seramjet , unstart , cross-correlation