Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation
Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation
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DOI：
10.1177/1350650113499555
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发表时间：
2014-01
期刊：
影响因子：
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通讯作者：
B. Littlefair;M. Cruz;R. Mills;S. Theodossiades;H. Rahnejat;R. Dwyer-Joyce;S. Howell-Smith
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文献类型：
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作者：
B. Littlefair;M. Cruz;R. Mills;S. Theodossiades;H. Rahnejat;R. Dwyer-Joyce;S. Howell-Smith
在内燃机中，活塞-气缸结合部占所有寄生摩擦损失的近 50%，其中活塞裙占这些损失的近一半。因此，部分圆周短裙柔性活塞已成为发展趋势，特别是对于高性能发动机。另一个趋势是使用轻质移动部件来减少惯性不平衡。这导致使用由较低密度材料（例如铝）制成的更短、更轻的活塞。这些较高功率密度的活塞通常在高温下运行，并且由于相对较高的热膨胀系数而经历显着的机械和热变形。因此，裙部的热机械变形在控制裙部与衬里之间的间隙方面起着重要作用，并使分析（特别是裙部变形）成为计算密集型过程。本文提出了一种预测活塞裙热机械变形的半自动方法，该方法结合了裙部变形以及活塞顶顺应性对裙部-衬套间隙的贡献。该过程基于合规矩阵的创建及其复杂的操作，显着减少了模拟运行时间。该方法与雷诺方程数值解的结合可以准确预测薄膜厚度。此外，采用超声波传感器阵列以非侵入方式直接测量接合润滑膜厚度。预测和测量显示出良好的一致性，这是迄今为止文献中尚未报道的方法。
The piston–cylinder conjunction accounts for nearly 50% of all the parasitic frictional losses in an IC engine of which the piston skirt accounts for nearly half of these losses. Consequently, part-circumferential short skirted compliant pistons have become a development trend, particularly for high-performance engines. Another trend has been the use of light weight moving parts to reduce inertial imbalance. This has led to the use of shorter lighter pistons constructed from lower density materials, such as aluminium. These higher power density pistons typically operate at elevated temperatures and undergo significant mechanical and thermal distortions due to the relatively high thermal expansion coefficients. As a result thermo-mechanical distortion of the skirt plays an important role in controlling the clearance gap between the skirt and the liner and makes the analysis, particularly skirt deformation, a computationally intensive procedure. This paper presents a semi-automatic methodology for the prediction of piston skirt thermo-mechanical deflection, which incorporates skirt deformation as well as piston crown compliant contribution to the skirt–liner clearance. This procedure is based on the creation of a compliance matrix and its intricate manipulation, significantly reducing the simulation run times. Integration of this approach with the numerical solution of Reynolds equation leads to an accurate prediction of film thickness. In addition, an array of ultrasonic sensors is used to directly measure the conjunctional lubricant film thickness in a non-invasive manner. The predictions and measurements show good conformance, an approach not hitherto reported in literature.