Enhancement of thermal mixing in coaxial supersonic jets

Abstract

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. Nomenclature T = stagnation temperature, °C fji = momentum flux, N/m 2 cr = standard deviation <f) = uniformity factor Subscripts av = average value um = unmixed condition 1 = properties of primary jet at nozzle exit

Mixing enhancement using chevron nozzle: studies on free jets and confined jets

“…A similar approach has been followed in several previous studies on mixing enhancement (e.g. [7,9,10]).…”

“…The triangular tab was found to be a better mixing promoter compared with the rectangular tab. Srikrishnan et al [9,10] have reported mixing enhancement studies using lobed nozzles in co-flowing supersonic jet streams. Nastase et al [11], Nastase and Meslem [12,13] and El Hassan and Meslem [14] carried out comprehensive flow visualization and PIV measurements on cross-orifice jets, daisy-shaped orifice jets and lobed jets.…”