基于油膜动态特性的拖拉机湿式离合器摩擦副接合热行为研究

Thermal Behavior During Engagement of Tractor Wet Clutch Friction Pairs Based on Oil Film Dynamic Characteristics

摘要:

湿式离合器作为拖拉机传动系统的核心动力控制部件，接合过程摩擦副片间油膜的瞬态粘性流动与热流固耦合效应，直接决定传动可靠性与热稳定性。针对湿式离合器油膜动态特性对摩擦副温度演化的影响机理不明晰的问题，本文通过分析湿式离合器接合过程流体控制与生热规律，研究动网格与热边界条件约束，构建热流固耦合模型；利用Fluent仿真摩擦副接合过程，得到油液流速、压力、温度和体积分数分布，揭示摩擦副瞬态热生热与热传递机制；开展湿式离合器台架温度试验，以决定系数（R2）、均方根误差（RMSE）以及平均绝对百分比误差（MAPE）为评价指标，验证热流固耦合模型对摩擦副接合热行为表征的有效性。结果表明：接合过程摩擦副片间油液流速在离心力与剪切作用下呈径向递增，中内径区域油液占比小，承载压力大，导致润滑效果差。因此，高温区持续集中在摩擦副中内径,最高温度位于钢片从外向内75%深度处，整体温度呈径向梯度分布。试验验证热流固耦合模型温度预测性能（R2为0.971、RMSE为2.11℃、MAPE为2.23%）优于热固耦合模型（R2为0.931、RMSE为3.47℃、MAPE为3.00%），具备更高预测精度。本文揭示了油膜动态特性对热生成与热传递的调控机制，为拖拉机湿式离合器结构优化及传动系性能提升提供了理论依据与技术支撑。

Abstract:

As the core power control component of the tractor transmission system, the transient viscous flow of the oil film between friction pairs and the thermo-fluid-solid coupling effect of the wet clutch during engagement directly determine transmission reliability and thermal stability. Aiming at the unclear mechanism of how the wet clutch oil film's dynamic characteristics affect friction pair temperature evolution, the fluid control and heat generation rules during engagement were analyzed, the dynamic mesh and thermal boundary constraints were studied, and a thermo-fluid-solid coupling model was established. Fluent simulated the friction pair engagement to obtain oil velocity, pressure, temperature and volume fraction distributions, revealing the transient heat generation and transfer mechanism. Wet clutch bench temperature tests were conducted with R2, RMSE and MAPE as indicators to verify the model's effectiveness in characterizing engagement thermal behavior. Results showed that oil velocity increased radially under centrifugal and shear forces; the middle-inner diameter zone had little oil, high pressure and poor lubrication, concentrating high temperature there with the peak at 75% radial depth of the steel disc and a radial temperature gradient. Tests verified the thermo-fluid-solid coupling model (R2=0.971, RMSE was 2.11℃, MAPE was 2.23%) had higher prediction accuracy than the thermo-solid coupling model (R2=0.931, RMSE was 3.47℃, MAPE was 3.00%). The research result revealed the oil film dynamics' regulation mechanism on heat generation and transfer, providing theoretical and technical support for tractor wet clutch structural optimization and transmission performance improvement.