Testing of a subscale scramjet research engine model was carried out i
n the Mach 6 Ramjet Engine Test Facility of the National Aerospace Lab
oratory, Kakuda Research Center. The engine had a sidewall compression
-type inlet. The fuel was hydrogen. With the attachment of a short str
ut on the top wall, intensive combustion with high-combustion efficien
cy was attained, and the engine-produced thrust canceled the drag. The
flame was held in the low-velocity region around the step, even after
the ignitors had been turned off. When the fuel flow rate was small,
there was a different combustion mode with weak combustion and little
thrust. The unstart condition seemed to begin around the cowl. Tangent
ial injection of fuel inhibited intensive combustion.