排序方式: 共有58条查询结果,搜索用时 328 毫秒
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D. Jung W. L. Wang A. Knafl T. J. Jacobs S. J. Hu D. N. Assanis 《International Journal of Automotive Technology》2008,9(1):9-15
The effects of the Abrasive Flow Machining (AFM) process on a direct injection (DI) Diesel engine fuel injector nozzle are
studied. Geometry characterization techniques were developed to measure the microscopic variations inside the nozzle before
and after the process. This paper also provides empirically-based correlations of the nozzle geometry changes due to the AFM
process. The resulting impact of the process on the engine performance and emissions are also assessed with a DI Diesel engine
test setup. This study shows that properly AFM-processed injectors can enhance engine performance and improve emissions due
to the improved quality of the nozzle characteristics. However, an extended process can also cause enlargement of the nozzle
hole as a side effect, which can adversely affect emissions. Emission measurements show the trade-off for the minimum levels
as the process proceeds. Since the enlargement of the hole during the AFM process is not avoidable and must be minimized,
strict control over the process is required. This control can be enforced by either limiting the AFM processing period, or
by properly preparing the initial hole diameter so as to accommodate the inevitable changes in the nozzle geometry. 相似文献
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This study was performed to clarify criteria for cavitation inception and the relationship between flow conditions and cavitation
flow patterns of diesel and biodiesel fuels. The goal was to analyze the effects of injection conditions and fuel properties
on cavitating flow and disintegration phenomena of flow after fuel injection. To accomplish this goal, it was utilized a test
nozzle with a cylindrical cross-sectional orifice and a flow visualization system composed of a fuel supply system and an
image acquisition system. In order to analyze the rate of flow and injection pressure of the fuel, a flow rate meter and pressure
gauge were installed at the entrance of the nozzle. A long distance microscope device equipped with a digital camera and a
high resolution ICCD camera were used to acquire flow images of diesel and biodiesel, respectively. The effects of nozzle
geometry on the cavitating flow were also investigated. Lastly, a detailed comparison of the nozzle cavitation characteristics
of both fuel types was conducted under a variety of fuel injection parameters. The results of this analysis revealed that
nozzle cavitation flow could be divided into four regimes: turbulent flow, beginning of cavitation, growth of cavitation,
and hydraulic flip. The velocity coefficient of diesel fuel was greatly altered following an increase in flow rate, although
for biodiesel, the variation of the velocity coefficient relative to the rate of flow was mostly constant. The cavitation
number decreased gradually with an increase in the Reynolds number and Weber number, and the discharge coefficient was nearly
equal to one, regardless of cavitation number. Lastly, it could not observe cavitation growth in the tapered nozzle despite
an increase in fuel injection pressure. 相似文献
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简要分析了桨后整流支架的特点及其一般设计原则,以及基于动量理论、叶素理论和理想螺旋桨理论阐述了桨后整流支架的设计方法,最后给出了一个基于该设计方法的设计实例,并将本设计方法的计算结果与试验结果进行了分析比较,进一步验证了该方法的可行性。 相似文献
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某型船用燃气轮机的进口导叶系统(Inlet Guide Vane system,IGV system)原采用气动控制系统,现参考航空发动机和重型燃气轮机的设计,改造为液压控制。为对此进行研究,基于Simscape工具箱,建立了液压控制的船用燃气轮机IGV系统模块化仿真模型。同时,利用该模型,借助模糊控制理论,对当前IGV系统中液压控制普遍使用的PID控制逻辑进行了优化。仿真结果表明:利用Simscape工具箱搭建的新型船用IGV系统仿真模型具有一定的可行性,且优化后的控制逻辑能有效提升IGV系统的运行效果。 相似文献
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互层土具有粗、细粒土交错互层的构造特点,受粗、细粒土组合一起的均匀性影响,淤泥质粘土与粉砂互层土的抗剪强度试验结果离散性较大。通过对营口某地区淤泥质粘土与粉砂互层土抗剪强度试验结果的分析,探讨选择淤泥质粘土与粉砂互层土抗剪强度试验的方法。 相似文献
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柴油机增压器喘振历来是轮机员工作中较为头疼的故障之一。文章详细介绍了一例发电柴油机增压器喘振故障的发生与排除过程,分析了增压器喘振的原因并提出了避免及预防的建议。 相似文献
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后导叶对喷水推进轴流泵性能的影响 总被引:1,自引:0,他引:1
通过三维紊流数值计算和模型试验研究后导叶对轴流泵整体性能的影响.计算和泵试验表明,基于RNG k-ε紊流模型的定常流动分析能有效预测高效区内的泵特性.叶轮和导叶之间的轴向间隙为0.1 D时,后导叶对叶轮性能几乎没有影响,后导叶主要以对叶轮出口水流的旋转动能的回收和水力损失的形式对泵的特性产生影响.通过后导叶设计工况的选择,可适应不同的应用要求,实现叶轮和后导叶优化配置的目的. 相似文献
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