Chevron spoiler to improve the performance of lobed ejector/mixer

Abstract

Chevron spoilers located at the lobe peaks of lobed nozzles were produced to improve the performance of lobed ejector/mixers. Numerical simulations of sword alternating-lobe nozzles and nozzles with chevron spoilers with area ratios of 3.06, 2.64, and 2.25 were used to analyse the effects of chevron spoilers on the pumping ratio, mixing effectiveness, and total pressure recovery coefficient. The impingement of the primary stream on the mixing duct was observed to depress mixing in the region off the lobe peaks and decrease the pumping ratio and total pressure recovery coefficient. Chevron spoilers located at lobe peaks can increase the spacing between the lobe peaks and the mixing duct and deflect the flow direction of the primary stream off the lobe peaks, thereby suppressing impingement of the primary stream on the mixing duct. Small chevron spoilers with an α=2.5° (where α is the angle between the chevron plane and the x axis) and an area ratio of 3.06 (the ratio of the cross-sectional area of the mixing duct to the exit area of the lobed nozzle) and large chevron spoilers with an α=2.5° and an area ratio of 2.25 can improve the mixing effectiveness while improving the pumping ratio and total pressure recovery coefficient harmoniously. It was inferred that moderately sized chevron spoilers with an α=2.5° and an area ratio of 2.64 could achieve harmonious improvements in the mixing effectiveness, pumping ratio, and total pressure recovery coefficient.