热气机活塞十字头摩擦学与动力学的耦合分析

Tribological and Dynamic Coupling Analysis of Piston-Crosshead in Stirling Engine

关键词:  热气机  活塞十字头  杆密封  动力学  摩擦学  耦合

Key words:  Stirling engine  Piston-crosshead  Rod sealing  Dynamics  Tribology  Coupling

摘要:

为了研究热气机活塞十字头结构摩擦学及动力学特性，在三维形貌测量的基础上进行连接副的接触分析，得到了其连接副摩擦学特性，建立了耦合摩擦学特性的热气机活塞组动力学模型。对比分析了计算结果与实测值，结果表明：热气机不同工况下其主密封摩擦功耗的计算值与试验值的误差不超过10%，验证了摩擦学计算和建模方法的正确性。当二阶运动较为柔和时，随十字头横向运动的挤压油膜在其对应推力面产生梯度均匀的压力分布，而剧烈的二阶运动造成十字头边缘与缸套碰撞产生局部高达30MPa的油膜总压。活塞十字头产生了远大于导引环、杆密封产生的侧推力，杆密封结构因属接触式密封而产生近600W的摩擦功耗，远大于十字头和导引环的摩擦功耗。因处于气膜润滑状态，导引环产生的侧推力和摩擦功耗较小，计算时可忽略不计。侧推力中的较高频率分量源于十字头与缸套间的摩擦学特性，在热气机动力学求解中应考虑摩擦学的影响，以提高其求解精度。

Abstract:

In order to study the tribological and dynamic characteristics of piston-crosshead structure in stirling engine， the contact analysis is carried out based on the three-dimensional topography measurement， and the tribological characteristics of joints are obtained. The dynamic model of the piston group coupled with the tribological characteristics is established，and comparison between the calculated and the experimental value is conducted. The results show that the error of the calculated friction power consumption of the main seal is less than 10% compared with the experimental value under different working conditions， which verifies the tribological calculation and the modeling method. When the second-order movement is moderate， the squeezed film pressure distribution of uniform gradient on the thrust surface is formed with the transverse movement of the crosshead. As the second-order movement becomes intense， the collision between the crosshead edge and the cylinder liner makes the oil film pressure reach up to 30MPa. The side thrust produced by crosshead is much greater than that of the guide ring and the rod sealing do. The rod sealing structure produces 600W power consumption due to the contact， which is far greater than that the crosshead and the guide ring produce. Due to the air film lubrication condition， the side thrust and the friction power consumption generated by the guide ring are little， which can be ignored in the calculation. The higher frequency component of the side thrust at the cross head is caused by the tribological characteristics between the crosshead and liner， and the calculation accuracy can be improved by coupling tribological characteristics in dynamic calculation of stirling engine.