Numerical Performance Analysis of a Supersonic Combustor at Mach 8 Flight Off-Design Conditions

A numerical investigation of the performance of a supersonic combustor designed for a flight Mach 8 is presented. Numerical simulations are used to assess the characteristics and operational limits of the combustor at design and off-design conditions. The combustor design point corresponds to the cruise condition at a Mach number of 8 and an altitude of 30 km. Off-design conditions correspond to a Mach number of 8 at 28 km altitude and a Mach number of 6 at 26 km altitude. Each off-design condition was investigated at three different angles of attack: 2, 0, and -2 deg. For constant flight Mach number and altitude, the variation of the angle of attack showed significant influence on the performance of the combustor, mainly on the ignition length. Flying at a negative angle of attack resulted in intense combustion and reduced ignition length. For the Mach 6 off-design condition, a dual-operation mode (ramjet-scramjet) with regions of subsonic combustion was observed. At such condition, it was possible to extend the operation of the combustor and avoid subsonic combustion regions by varying the angle of attack to a positive value. For a constant flight Mach number and altitude, the variation of the angle of attack showed an interesting mechanism to control combustion.