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111.
It has been well known that nozzle end-clearances in a Variable Nozzle Turbine (VNT) are unfavorable for aerodynamic performance, especially at small openings, and efforts to further decrease size of the clearances are very hard due to thermal expansion. In this paper, both the different sizes of nozzle end-clearances and the various ratios of their distribution at the hub and shroud sides were modelled and investigated by performing 3D Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations with a code of transferring the aerodynamic pressure from the CFD results to the FEA calculations. It was found that increasing the size of the nozzle end-clearances divided equally at the hub and shroud sides deteriorates turbine efficiency and turbine wheel reliability, yet increases turbine flow capacity. And, when the total nozzle end-clearances remain the same, varying nozzle end-clearances’ distribution at the hub and shroud sides not only shifts operation point of a VNT turbine, but also affects the turbine wheel vibration stress. Compared with nozzle hub clearance, the shroud clearance is more sensitive to both aerodynamic performance and reliability of a VNT turbine. Consequently, a possibility is put forward to improve VNT turbine efficiency meanwhile decrease vibration stress by optimizing nozzle end-clearances’ distribution. 相似文献
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《中国航空学报》2016,(3):814-823
A computational fluid dynamics(CFD) simulation method based on 3-D Navier–Stokes equation and Arbitrary Lagrangian–Eulerian(ALE) method is presented to analyze the grooved slipper performance of piston pump.The moving domain of grooved slipper is transformed into a fixed reference domain by the ALE method,which makes it convenient to take the effects of rotate speed,body force,temperature,and oil viscosity into account.A geometric model to express the complex structure,which covers the orifice of piston and slipper,vented groove and the oil film,is constructed.Corresponding to different oil film thicknesses calculated in light of hydrostatic equilibrium theory and boundary conditions,a set of simulations is conducted in COMSOL to analyze the pump characteristics and effects of geometry(groove width and radius,orifice size) on these characteristics.Furthermore,the mechanics and hydraulics analyses are employed to validate the CFD model,and there is an excellent agreement between simulation and analytical results.The simulation results show that the sealing land radius,orifice size and groove width all dramatically affect the slipper behavior,and an optimum tradeoff among these factors is conducive to optimizing the pump design. 相似文献
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陆赵情%张美云%王志杰%吴养育%代攀 《宇航材料工艺》2006,36(6):5-8
论述了芳纶纸基复合材料的国内外研究发展状况,主要成分芳纶短切纤维和芳纶沉析纤维的结构、特点及其合成工艺,介绍了芳纶纸基复合材料在航天航空领域的应用情况,并就其开发过程中所涉及的关键技术进行了分析总结。 相似文献
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通过对大量的试验结果分析,对Lefebvre A H和Gordon A H等人提出的燃烧效率参数θ进行了改进。提出了一个综合参数Ω。并找到了冲压发动机燃烧室燃烧效率η_c与Ω之间的定量关系式。利用这个关系式可以对燃烧效率进行计算。计算与试验结果误差约为5%~10%。计算方法也适用于一般的冲压发动机燃烧室燃烧效率计算。其精度为5%~10%。 相似文献
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1.变量原理和供油量的一般计算公式 双作用叶片泵的转子径向液压力平衡,轴承负荷小,寿命高,且工作转速已可达40000~50000r/min,可实现由航空发动机直接传动,是一种有发展前途的航空发动帆燃油泵.现有的双作用叶片泵几乎都是定量泵,其供油量只能用外部回油调节,功率损失和发热量都很大。 相似文献
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