As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study ...As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study analyzed the near-field unsteady flow around a pantograph using a large-eddy simulation(LES) with high-order finite difference schemes. The far-field aerodynamic noise from a pantograph was predicted using a computational fluid dynamics(CFD)/Ffowcs Williams-Hawkings(FW-H) acoustic analogy. The surface oscillating pressure data were also used in a boundary element method(BEM) acoustic analysis to predict the aerodynamic noise sources of a pantograph and the far-field sound radiation. The results indicated that the main aerodynamic noise sources of the pantograph were the panhead, base frame and knuckle. The panhead had the largest contribution to the far-field aerodynamic noise of the pantograph. The vortex shedding from the panhead generated tonal noise with the dominant peak corresponding to the vortex shedding frequency and the oscillating lift force exerted back on the fluid around the panhead.Additionally, the peak at the second harmonic frequency was associated with the oscillating drag force. The contribution of the knuckle-downstream direction to the pantograph aerodynamic noise was less than that of the knuckle-upstream direction of the pantograph, and the average sound pressure level(SPL) was 3.4 dBA. The directivity of the noise radiated exhibited a typical dipole pattern in which the noise directivity was obvious at the horizontal plane of θ=0°,the longitudinal plane of θ=120°,and the vertical plane of θ=90°.展开更多
为进一步探索高性能、低噪声的离心压缩机优化设计方法,该文选用某燃料电池车用小型高转速离心压缩机为研究对象,通过三维内流场非定常分析对其气动性能和气动噪声进行计算,仿真求得的压升曲线与试验基本一致。基于该数值模型,采用最优...为进一步探索高性能、低噪声的离心压缩机优化设计方法,该文选用某燃料电池车用小型高转速离心压缩机为研究对象,通过三维内流场非定常分析对其气动性能和气动噪声进行计算,仿真求得的压升曲线与试验基本一致。基于该数值模型,采用最优拉丁方试验设计分析了叶片进口角、叶片出口角、尾缘倾角、叶顶间隙和叶片厚度对压缩比、等熵效率和整机声功率级的影响,结果表明叶片厚度和叶顶间隙最为关键,与压缩比和等熵效率负相关,与声功率级正相关,前倾叶片较后倾叶片噪声更低。采用Kriging模型对数值计算结果进行拟合,利用多目标遗传算法对Kriging模型进行循环优化设计。优化结果表明,Kriging模型精度满足需求,优化方案在设计工况点的压缩比提高3.56%,等熵效率提高1.02%,整机声功率级下降3.79 d B,在非设计工况点的压缩比和等熵效率也有提高,综合性能得到明显改善。该研究可为高性能、低噪声离心压缩机的优化设计提供参考。展开更多
基金supported by the High-Speed Railway Basic Research Fund Key Project of China(Grant No.U1234208)the National Key Research and Development Program of China(Grant No.2016YFB1200403)+1 种基金the National Natural Science Foundation of China(Grant Nos.51475394&51605397)the Research Project of State Key Laboratory of Traction Power(Grant No.2016TPL_T02)
文摘As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study analyzed the near-field unsteady flow around a pantograph using a large-eddy simulation(LES) with high-order finite difference schemes. The far-field aerodynamic noise from a pantograph was predicted using a computational fluid dynamics(CFD)/Ffowcs Williams-Hawkings(FW-H) acoustic analogy. The surface oscillating pressure data were also used in a boundary element method(BEM) acoustic analysis to predict the aerodynamic noise sources of a pantograph and the far-field sound radiation. The results indicated that the main aerodynamic noise sources of the pantograph were the panhead, base frame and knuckle. The panhead had the largest contribution to the far-field aerodynamic noise of the pantograph. The vortex shedding from the panhead generated tonal noise with the dominant peak corresponding to the vortex shedding frequency and the oscillating lift force exerted back on the fluid around the panhead.Additionally, the peak at the second harmonic frequency was associated with the oscillating drag force. The contribution of the knuckle-downstream direction to the pantograph aerodynamic noise was less than that of the knuckle-upstream direction of the pantograph, and the average sound pressure level(SPL) was 3.4 dBA. The directivity of the noise radiated exhibited a typical dipole pattern in which the noise directivity was obvious at the horizontal plane of θ=0°,the longitudinal plane of θ=120°,and the vertical plane of θ=90°.
文摘为进一步探索高性能、低噪声的离心压缩机优化设计方法,该文选用某燃料电池车用小型高转速离心压缩机为研究对象,通过三维内流场非定常分析对其气动性能和气动噪声进行计算,仿真求得的压升曲线与试验基本一致。基于该数值模型,采用最优拉丁方试验设计分析了叶片进口角、叶片出口角、尾缘倾角、叶顶间隙和叶片厚度对压缩比、等熵效率和整机声功率级的影响,结果表明叶片厚度和叶顶间隙最为关键,与压缩比和等熵效率负相关,与声功率级正相关,前倾叶片较后倾叶片噪声更低。采用Kriging模型对数值计算结果进行拟合,利用多目标遗传算法对Kriging模型进行循环优化设计。优化结果表明,Kriging模型精度满足需求,优化方案在设计工况点的压缩比提高3.56%,等熵效率提高1.02%,整机声功率级下降3.79 d B,在非设计工况点的压缩比和等熵效率也有提高,综合性能得到明显改善。该研究可为高性能、低噪声离心压缩机的优化设计提供参考。
