Experimental study on mixing enhancement by petal nozzle in supersonic flow

An experimental study on mixing enhancement in supersonic flow by a radially lobed nozzle, called petal nozzle, has been conducted. The study entails the mixing of a supersonic primary stream and a coflowing sonic secondary stream in cold flow. The radial distribution of momentum flux is characterized by a mixing parameter called the degree of mixing. The loss in stagnation pressure associated with the mixing is also determined. With emphasis on momentum mixing and pressure drop, the petal nozzle and the conventional conical nozzle have been compared so as to assess the suitability of the former. The results show that using an optimum length of the mixing chamber, a compromise can be struck between the mixing enhancement and the associated increase in pressure loss. The contribution of shear area at the nozzle exit to mixing enhancement was found to be marginal. Nomenclature LID = length to diameter ratio of the mixing tube P() = stagnation pressure x — axial station along the mixing tube JJL = momentum flux, N/M2 cr = standard deviation 4> = uniformity factor Subscripts av = average value um = unmixed condition