耦合进排气壳的增压器涡轮流动干扰及激振力弱化研究

为探究船用增压器涡轮在耦合进排气壳条件下的流动特性,采用SST湍流模型和FFT方法对某增压器轴流涡轮与进排气壳耦合的流场进行非定常数值模拟,重点分析排气壳非对称流场对涡轮动叶片压力的干扰特性和扰动来源,在此基础上提出基于导叶非对称布局的激振力弱化改型方案并进行了验证。结果表明：进气壳影响静叶前缘静压沿周向的分布,排气壳流场导致的非对称背压会给动叶表面造成低频的压力波动,约为3.6%的转子通过频率,在尾缘吸力面处该低频波动幅值大于动静叶排干涉导致的高频波动幅值；排气壳内部复杂的分离流动和涡系结构是产生上述流动干扰的主要原因。4种非对称布局方案都能在几乎不影响涡轮性能的前提下分散并弱化高频波动幅值；其中Case2尾缘高频幅值减小了98.6%,低频幅值减小了52.6%,而且涡轮效率还有略微提高,为最优布局。

Flow Interference and Weakening of Excitation Force of Turbocharger Turbine Coupled with Inlet and Exhaust Casings

In order to explore the flow characteristics of a marine turbocharger turbine with coupling inlet and exhaust casings, SST turbulence model and FFT method was carried out towards the unsteady simulation accounting for flow field of turbocharger axial turbine coupling with inlet and exhaust casings. The interference characteristics of turbine rotor pressure induced by asymmetric flow field of the exhaust casing was analyzed emphatically so as its sources. A modified scheme of excitation force weakening based on asymmetric vanes was proposed and verified based on the source analysis. Results show that inlet casing affects the circumferential distribution of stator static pressure at the leading edge, while the asymmetric back pressure caused by the exhaust casing flow field lead to low frequency pressure fluctuations on the rotor blade surface, which is about 3.6% of the rotor passing frequency. On the suction surface of trailing edge, the amplitude of low frequency fluctuation is larger than that of the high frequency fluctuation caused by the stator-rotor blade row interference. The complex flow separation and vortex structure in the exhaust casing is the major contributors for the above flow interference. The four vane asymmetric layout schemes can disperse and weaken the amplitude of high frequency fluctuations on the premise of hardly affecting the turbine performance. The high-frequency amplitude of Case2 is reduced by 98.6% at trailing edge while the low-frequency amplitude is reduced by 52.6% at most, thus Case2 is the optimal layout for its slight enhancement on turbine efficiency.