超音速喷嘴变工况性能分析与试验研究

Analysis and Experimental Study of the Off-design Operating Condition Performance of a Supersonic Nozzle

采用数值模拟方法对超音速喷嘴的变工况性能进行了分析,研究了不同压比下速度系数以及喷嘴内部流场的变化规律得到了,设计工况下喷嘴的速度系数(0.96)和总压恢复系数(0.87)。为进一步掌握超音速喷嘴的气动性能,进行了平面叶栅风洞试验,测量了不同压比下叶片表面马赫数分布,结合数值模拟结果,分析了叶栅通道内的流场特性。在超音速喷嘴出口截面处,由于膨胀波组等因素的影响,吸力面将产生马赫数拐点,并随着压比的减小逐渐后移;当偏离设计压比时,叶栅吸力面将出现汽流分离;通过叶栅S1流面纹影照片,观察到了叶栅槽道内的波系构成,与数值模拟结果具有较高的一致性。试验结果验证了数值计算的准确性。

Usually,supersonic nozzles are used in the Curtis stage of a marine steam turbine.Through a numerical simulation method,the authors have performed an analysis of the off-design operating condition performance of a nozzle with the law governing a change of its velocity coefficients at various pressure ratios and its internal flow field being studied and the velocity coefficient(0.96) and total pressure recovery coefficient(0.87) of the nozzle under the design operating condition being obtained.To further know well the aerodynamic performance of the nozzle under discussion,a wind tunnel test of its plane cascade was conducted.The distribution of the Mach numbers on the surface of the blade at different pressure ratios was measured and the characteristics of the flow field inside the passage of the cascade were analyzed in combination with the numerical simulation results.In the cross section at the outlet of the supersonic nozzle,a turning point of the Mach number will be produced on the suction surface due to the influence of the expansion wave group and other factors and will gradually shift backward with the pressure ratio.When the pressure ratio deviates from its design one,a steam flow separation will emerge on the suction surface of the cascade.Through a schlieren photo of the S1 stream plane of the cascade,the composition of the wave system in the flow passage of the cascade were observed and exhibited a relatively high agreement with the numerical simulation results.The test results verifies that the numerical calculation results are correct and make designers more visually learn the flow characteristics inside the supersonic nozzle.