Abstract: To investigate the principle and parameters of the flight Mach number Ma_flight=4-7 hydrocarbon fueled dual-combustor scramjet engine, we perform the experimental studies of both cold flow field mixing and combustion on a direct-connected combined supersonic combustor with a flame holding torch formed by a small pilot burner and a streamwise vortice generator. Let 10% inlet outlet supersonic flow again into the pilot burner, in which the air experiences the first air fuel spray mixing and a stable subsonic pilot combustion. The pre-combustion gas then mixes secondly with the major fuel injection stream to form a hot torch with rich and partly decomposed fuel. The torch effluent then passes a group of lobed mixer and emits into the supersonic main flow. This confluent flow is designed to generate a streamwise-vortices mixing and, by immersing gradually from the layer of subsonic flow into the layer of supersonic flow, to induce an efficient and stable supersonic combustion. Three pilot burners and one supersonic combustor are used in the experiment of cold air through flow, fuel injection and ignition under the conditions of combustor inlet Mach number Ma_inlet=2.5, total pressure 1.5?10⁶ Pa and 1.0?10⁶ Pa, total temperature 285 K. The experiment and calculation indicate that the main flow in the supersonic combustor keeps supersonic, though the oblique shock train slightly moves while dual-combustor is ignited. There are four kinds of vortices phenomena which enhance the mixing between subsonic and supersonic flows. The combination of a triple-shock inlet and a small volumetric-heat-intensity combustor with the lobed mixer could realize a stable torch flame as a stabilized holder of the supersonic combustion. In this combustor, the second area of flame has been found in the original cold flow region of subsonic and low-supersonic flows within the supersonic combustor, without the destruction of the supersonic flow state of the upper flow-layers.

Key words: supersonic flow, supersonic combustion, pilot burner, lobed mixer, streamwise-vortices mixing, dual-combustor ramjet