AN EXPERIMENTAL INVESTIGATION OF THERMAL MIXING AND COMBUSTION IN SUPERSONIC FLOWS

A radially lobed nozzle (petal nozzle) is being increasingly recognise d as a potential candidate for promoting mixing in compressible flows. An experimental investigation has been conducted to study its effecti veness in improving thermal mixing and combustion in supersonic flow. A hot gas jet issuing supersonically from a lobed nozzle mixes with a cold supersonic jet in a circular mixing tube. The two jets issue coax ially. A detailed survey of the flow field inside the mixing duct reve als that nearly complete thermal mixing (as exemplified by the nearly uniform temperature distribution) could be achieved in a short distanc e when a lobed nozzle is employed. The results also indicate the prese nce of large-scale vortices in the now field downstream of the lobed n ozzle. Having thus created a held in which mixing is good, supersonic combustion was then attempted. Kerosene was introduced into the hot st ream issuing from the lobed nozzle and it burned mainly in the mixing tube, which served as a supersonic combustor. Resulting temperature an d pressure rises were measured and the supersonic combustion efficienc y was found to be of the order of 60%. The performance of a convention al conical nozzle was found to be much inferior to that of the petal n ozzle under identical conditions. Copyright (C) 1996 by The Combustion Institute