高速湿式多片离合器流固耦合振动研究

Experimental results show that flow-induced vibration or flow-induced instabilities will happen between frictional plates in high speed multi-plate wet clutch if the work speed is up to a critical value. This leads to suddent increasing of drag torque and power loss. The analysis of frequency spectrum of vibration signal reveals that the flow-induced vibration of wet clutch has wide frequency spectrum, and the frequency spectrum is different with the single induced mechanism resulted in narrow frequency response such as vortex shedding and fluid-elastic instability.To solve the problem of flow-induced virbration,a dynamical and nonlinear FSI model of multi-plate wet clutch is presented, and the numerical simulation of the flow-induced vibration is also accomplished. The proposer attempt to discuss the power transportation and feedback channel of the non conservation sysytem and investigate the relationship between power input and vibration phase, then reveal the mechanism of flow-induced vibration and instability. On the basis of dynamical model and instability mechanism, the regulation of effective stiffness and fluid damping under fluid-solid interaction is researched, and vibration restain from accessional fluid dampig caused by the grooves of frictional plate under two phase flow condition is also discussed. The conclusion integrating with the proposer's earlier research will build an unified model of drag torque including full film lubrication at low speed range, aeration at middle speed range and flow-induced vibration at high speed.This unified model avail to predict drag torque, design wet clutch parameters,reduce power loss and improve efficency of high speed transmission.

试验表明，高速分离状态湿式多片离合器线速度大于某临界值时，会发生摩擦片之间的强烈碰振现象，引起带排转矩及带排功率损失的急剧上升；前期的振动频谱分析表明该现象为流固耦合诱发的宽频带流致振动和流致失稳，其诱发机理有别于单一的窄频带响应振动特性的漩涡脱落或者流弹不稳定诱发机理。本申请针对该流固耦合振动问题，拟建立湿式多片离合器非线性约束流固耦合动力学模型，并进行摩擦片的流固耦合作用数值模拟；探讨非保守振动系统的能量输送与反馈通道，研究能量输入与振动相位的关系，揭示流固耦合诱发振动及其失稳机理；研究流固耦合作用下的结构有效刚度及流体阻尼的变化规律，探讨摩擦片沟槽优化在气液两相流动状态下的附加流体阻尼对振动的抑制。项目成果结合申请人前期的研究工作，可形成湿式多片离合器低速全膜润滑、中速空化流动和高速流固耦合振动的统一带排转矩模型，用于离合器性能预测和参数设计，减小功率损失，提高传动效率。

在大于某临界转速时，高速湿式多片离合器摩擦片之间发生强烈碰振，带排转矩急剧上升，造成摩擦片热失效，其振动诱发机理尚不清楚。本项目针对高速湿式多片离合器流固耦合振动问题，建立摩擦片非线性约束流固耦合动力学模型，揭示流体诱发振动及其失稳机理，分析流固耦合作用下的流体刚度和流体阻尼，获取流固耦合振动特征及其带排转矩影响规律。.针对摩擦片流固耦合振动问题，建立了气液两相流的均相模型和摩擦片的流固耦合动力学模型，通过有限元方法数值求解零阶、润滑方程，获得了流体的9个刚度系数以及9个阻尼系数。针对高速湿式离合器振动失稳机理，建立了双自由度角向摆振稳定性分析模型，无量纲综合刚度与角向直接刚度较为接近，说明两相流体所能提供的阻尼很小，提高角向稳定性只能采取提高临界扰动频率以及提供附加阻尼的措施。与径向滑动轴承的半频涡动类似，角向摆动自振的临界频率比约为0.5，该频率特性为固有特性，并完成了试验验证。湿式离合器角向摆动自振的满足条件远低于轴向自激振动，故其碰振通常表现为角向摆振。.建立了摩擦片的碰撞接触模型，分析了角向摆振的非线性振动响应。发生碰撞后，角向摆振为等幅振动，碰撞相位角在-180°~180°之间变化，表现为摩擦片的章动。角向摆振响应基本保持周期性，流体刚度、阻尼和摩擦片转动惯量决定的谐振分量仍然起主导作用，但已经开始表现非线性特征，为非完全重合的相轨迹。建立了含碰撞摩擦的高速带排转矩模型，并进行了试验验证。.进行了槽型参数对稳定性影响规律的研究和斜线槽、螺旋槽的槽型优化，完成了T型槽、人字槽的刚度、阻尼特性分析。根据流固耦合动力学模型及稳定性分析，给出了典型槽性的角向稳定性区间。研究了收敛的油膜间隙有利于提高轴向无量纲阻尼、角向无量纲综合刚度，从而提高轴向振动稳定性以及角向摆振的稳定性。分析了附加刚度、阻尼材料提高角向稳定性的可行性。.发表了3篇SCI论文，2篇会议论文，在审论文4篇，研究成果为提高振动临界转速奠定了理论基础。