Experimental and numerical investigations on flow fields and performance of dual combustion ramjet

Abstract

Dual combustion ramjet (DCR) is one of the most promising and realistic propulsion systems to realize hypersonic flight. The flow fields and the performance of the full-size DCR in Ma4/17 km and Ma6/25 km flight conditions are investigated through direct-connected experiments and numerical simulations. The pressure distributions from simulations are in agreement with that from experiments under both cold flow and hot flow conditions. Different combustion modes are revealed according to numerical results: purely subsonic flow field is established in the front part of the combustor in Mach 4 condition, and there is a thermal choked throat; only central flow is subsonic in Mach 6 condition, and the peripheral supersonic air results in a lower static temperature (less than 2000 K), which is beneficial to thermal protection of the combustor wall. The thrust increment increases with the increasing of the equivalence ratio (Φ). The thrust increment is 8.1 kN for Mach 4 when Φ = 0.9; however, further increasing the equivalence ratio causes unstart of the supersonic intake. The thrust increment is 3.15 kN for Mach 6 when Φ = 1.0. The equivalence ratio affects the combustion efficiency and the specific impulse with the same trend. The maximum combustion efficiency is 0.91 for Mach 4 and 0.89 for Mach 6. The maximum specific impulse is 13.3 kN·s/kg for Mach 4 and 7.96 kN·s/kg for Mach 6. In general, the performance is good and the DCR is worth further investigating.