2001 Volume 49 Issue 574 Pages 400-406
Combustion and unstart processes of a scramjet engine in Mach 4 flight condition were investigated experimentally focusing on the changes of the engine internal flow structures under the ‘weak’ and ‘intensive’ combustion modes. Cold flow tests were carried out using a 1/5-scale model of the scramjet engine examined in the firing tests at Ramjet Engine Test Facility (RJTF). Pressure rise due to combustion was successfully simulated by a flow-plug installed in the engine nozzle section to demonstrate good agreement with the wall pressure distributions of the engine under ‘weak’ and ‘intensive combustion’ modes. Especially, upper limit of the combustor maximum pressure at which engine fell into unstart was exactly simulated. This limit value was revealed to be the separation pressure of the turbulent boundary layer in the isolator. Shadowgraph visualization demonstrated that in the intensive combustion mode large-scale boundary layer separation was formed over the isolator, backward facing step and constant area combustor.
