Tests have been made to determine the thrusts obtainable from two groups of Laval-type convergent-divergent propelling nozzles over a range of pressure ratios up to 9 : 1 using air at sensibly ambient temperature. The nozzles of the first group were designed for pressure ratios of 4, 6, 8, 10 and 12 and had an included divergence angle of 20° whilst those of the second group were all designed for a pressure ratio of 8 and had included divergence angles of 5°, 10°, 20°, 30° and 50°.nThe superior thrust performance at high pressure ratios of the Laval-type nozzles over that of a plain convergent nozzle has been demonstrated. The effect of divergence angle on the thrust has been examined and, within the range 5° to 25°, been found to be small.
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