Noncircular jet dynamics in supersonic combustion

Abstract

The mixing characteristics of circular, small-aspect-ratio elliptic and rectangular jets were studied in subsonic, sonic, and supersonic flows. The experiments were carried out in both cold and hot flows using hot-wire anemometry, thermocouples, and photography. The elliptic and rectangular jets had similar features, with a slightly better mixing performance of the elliptic jet in the subsonic and supersonic flows. The elliptic and rectangular jets had a higher spreading rate relative to the circular jet, epecially at the minor axis plane. In the subsonic jet, the spreading rate was limited to the first five equivalent diameters (De) from the nozzle. In the supersonic underexpanded jet, the spreading rate was three times higher in the entire range (30£>e) measured. The minor axis plane was also characterized by high intensity of near-field pressure fluctuations. The two phenomena can be related to each other when an acoustic feedback occurs. Nomenclature & = aspect ratio D = circular nozzle diameter De = equivalent diameter E = energy of the fluctuating pressure components in the power spectrum / = frequency M = Mach number r = radial coordinate Re = Reynolds number, U0De/v R05 = half-width of the jet; r at with U= U^ /2 Rw 5 = half-width of the reacting jet; r at which