ISSN   1004-0595

CN  62-1224/O4

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徐海军, 张雷, 王晓聪, 杨聪楠. 环形气缸内壁油膜非均匀润滑特性及影响分析[J]. 摩擦学学报(中英文), 2024, 44(11): 1−10. doi: 10.16078/j.tribology.2023058
引用本文: 徐海军, 张雷, 王晓聪, 杨聪楠. 环形气缸内壁油膜非均匀润滑特性及影响分析[J]. 摩擦学学报(中英文), 2024, 44(11): 1−10. doi: 10.16078/j.tribology.2023058
XU Haijun, ZHANG Lei, WANG Xiaocong, YANG Congnan. Investigation on the Lubrication Performance of Non-Uniformity Oil Film in an Annular Cylinder System[J]. Tribology, 2024, 44(11): 1−10. doi: 10.16078/j.tribology.2023058
Citation: XU Haijun, ZHANG Lei, WANG Xiaocong, YANG Congnan. Investigation on the Lubrication Performance of Non-Uniformity Oil Film in an Annular Cylinder System[J]. Tribology, 2024, 44(11): 1−10. doi: 10.16078/j.tribology.2023058

环形气缸内壁油膜非均匀润滑特性及影响分析

Investigation on the Lubrication Performance of Non-Uniformity Oil Film in an Annular Cylinder System

  • 摘要: 环形串联创新布局的气缸-活塞系统提升了发动机作功频率,但活塞环存在绕转子主轴的公转运动,也造成了环形气缸内壁非均匀磨损现象. 为揭示环形气缸内壁摩擦和润滑特性,本文中针对环形气缸布局结构和活塞环绕发动机主轴定轴公转运动,利用二维平均雷诺方程和凸微体接触模型等建立了环形气缸-活塞环接触结构的动压油膜数学模型,并采用有限差分数值计算方法对数学模型进行了求解,研究了转子差速运动下润滑油黏度和活塞环张力等参数对活塞环上动压油膜厚度、最小膜厚比以及油膜压力等特性的影响. 结果表明,2组转子作差速定轴转动时,活塞环随1组转子定轴转动,其圆周上各点相对另1组转子上的环形气缸壁截面圆周上对应点的速度不一致,造成动压油膜厚度沿活塞环圆周方向不均匀,且油膜厚度不均匀性在发动机主轴转动1周的热力学不同阶段进一步扩大,最小膜厚比和油膜压力等参数呈类似演变特性. 增大润滑油黏度或减小活塞环张力可显著增加油膜厚度,改善最小膜厚比的不均匀状态,实现更好的润滑效果,但也发现其对油膜最大压力影响不大. 研究结果初步揭示了环形气缸中活塞环非均匀动压油膜形成机理和演变规律,为后续环形气缸摩擦功耗计算和减磨优化设计提供理论依据.

     

    Abstract: Thenovelannular cylinder-piston system under an annular series arrangement can increase the engine power performance, such as the work frequency per rotation, but also has leaded to uneven wear on the annular cylinder wall, due to the ring’s rotation around the rotor axis. To analyze the friction and lubrication characteristics of the annular cylinder-ring system, firstly, the lubrication mechanism was studied using a wedge effect around the annular cylinder-ring contact area, and the rotation of ring was illustrated under the annular cylinder construction. Secondly, with a consideration on the annular cylinder wall construction and ring rotation, the dynamic oil film analytical model of the annular cylinder-ring structure was established, using the two-dimensional mean Reynolds equation to describe the relationship between of oil film thickness, pressure and the motion of ring. Then the convex micro-body contact model by Greenwood was utilized to analyze the balanced forces between finite small bodies, which are on different part of the ring. Thirdly, after a spatial and time discretization of the dynamic oil film analytical model, the finite difference numerical calculation method was applied to solve the equations, using a Successive-Over-Relaxation algorithm (SOR). Before the calculation, convergence conditions of oil film thickness and pressure had been defined, and initial value of oil film thickness and boundary conditions had been confirmed. After the calculation, influences of lubricating oil viscosity and piston ring tension on dynamic pressure oil film thickness, minimum film thickness ratio and oil film pressure were evaluated. The calculation results showed that while the rotor was rotating, different point on the ring installed to a rotor-piston had different velocity relative to the annular cylinder wall fixed on another rotor, resulting in different oil film thickness circumferentially along the ring body. The unevenness of the oil film thickness became worse during different thermodynamics stages. The minimum film thickness ratio and oil film pressure presented similar evolution characteristics. By increasing the lubricating oil viscosity 4 times, the maximum value of the minimum film thickness ratio increased accordingly from 2.5 μm to 3 μm during some period of the thermodynamic process, indicating that the hybrid-lubricating state had evolved into a whole-lubricating state for the cylinder-ring structure. While considering the maximum value of the minimum oil film thickness, it enlarged over 2 times. Reducing the ring tension value to half, the maximum value of the minimum oil film ratio changes from 3.8 μm to 2.3 μm, demonstrating a thinner oil film and a worse lubricating result. However, neither the lubricating oil viscosity nor the ring tension would play an important role on the variation of the oil film pressure, it was mainly determined by the gas pressure on both sides of the ring. Conclusion could be drawn that by increasing the lubricating oil viscosity or reducing the ring tension, the annular cylinder wall would achieve a better lubrication performance, such as improving the minimum film thickness ratio and decreasing the uneven lubricating state of the annular cylinder-ring structure. The research results revealed preliminarily the formation and evolution of uneven oil film between the annular cylinder and ring, and would contribute a theoretical basis for the subsequent calculation of friction power consumption and optimization design of wear reduction of annular cylinder.

     

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