Numerical simulation of the unstart process of dual-mode scramjet

Dual-mode scramjet is suitable for the development direction of supersonic aircraft due to its large speed range with improved efficiency. Predicting unstart phenomenon is one of the key points in the operation process of dual-mode scramjet. Unstart process of dual-mode scramjet from a started state to an unstarted state has been investigated numerically at the free-stream Mach number of 4. Several steady cases in started states have been performed and they have been validated by comparing with the experimental results. Numerical results are in good agreement with experimental results. The location of shock train in dual-mode scramjet has been investigated by constructing the pressure diagrams during unstart process. Shock train moves upstream during unstart process as the throat area ratio decreases. There are four stages of unstart process, such as, shock train leading edge in the combustor, shock train leading edge in the isolator, separation bubble in the isolator inlet and inlet unstart. There are quite different among the transient flow fields of each stage. Prediction of unstart phenomenon has been done by applying time histories of static pressure and mass flow rate. Depending on this investigation, the alarm of unstart phenomenon can be given before it happens.