Enhancement of thermal mixing in coaxial supersonic jets

An experimental study was conducted to investigate the thermal mixing of a hot, supersonic, primary jet of combustion gases with a coflowing secondary jet of air at ambient temperature. The Mach numbers of the two jets were 1.2 and 1.7, respectively. To enhance the mixing, the core (primary) jet was admitted through a three-dimensional, radially lobed nozzle, referred to as the petal nozzle. The uniformity of stagnation temperature in the flowfield was used to characterize the extent of mixing between the jets. The effect of confinement on the mixing was also investigated. The mixing performance of the lobed nozzle and the associated loss in stagnation pressure were compared with those for a conventional conical nozzle. The study confirms the efficacy of the radially lobed nozzle in thermal and momentum mixing of supersonic jets and highlights its potential in supersonic combustion systems.