基于两相流动的车用液力缓速器动态特性预测及控制技术研究

Braking is of the utmost important to driving traffic safety, and hydraulic retarder is the mainstream auxiliary braking device to guarantee safe ride of heavy vehicles during high-speed and down-hill driving conditions. It is typical standard equipment for heavy vehicles in France and Germany presently. While design of cascade and oil fill-drain system and braking performance prediction during oil-filled process are bottleneck to research and development of domestic hydraulic retarder. This project aims to elevate dynamic braking performance of hydraulic retarder, from the point of view of mapping relation between two-phase flow mechanism in cascade and oil fill-drain system and partial oil-filled braking performance. Relationship between internal flow pattern and braking behavior under different oil-filled rate are specified. The parametric modeling of single periodic flow is achieved, thus three-dimensional integrated optimization design of cascade system is accomplished in two-phase flow and corresponding reduce-order braking model is derived. Reference to international advanced technology, the oil charging and discharging system are designed for rapid response and convenient control with the electronic control unit as the core of the control system.With the flow analysis revealing the variation of filling rate and system pressure and flow rate, fluid dynamic model of oil fill-drain system for hydraulic retarder is proposed. To meet the demand of braking performance of whole vehicle, constant speed and constant torque braking strategy are formulated and corresponding collaborative simulation model is built and tested. Cascade and oil fill-drain system design are realized on the basis of research above. The project intends to reveal braking discipline and accelerate braking response of hydraulic retarder, and lay theoretical and technical foundation for research and development for high performance hydraulic retarder.

制动对行车安全至关重要，液力缓速器是保证大客车和重型卡车等车辆在高速及下长坡等工况下安全行驶的主流辅助制动装置，在国外相应车型上得到了广泛的应用，但目前国内尚无成熟的液力缓速器产品。本项目以提高液力缓速器动态制动性能为目标，揭示其叶栅及充放油系统内部液气两相流动规律，对叶栅系统进行参数化建模，获取气液两相流动状态下叶栅参数对缓速制动特性的影响规律，建立制动性能预测降阶简化模型；提出以电控部件为控制核心，面向快速响应和便捷控制的充放油系统设计方案。通过流动分析揭示充液率与系统压差和流量的变化规律，提出控制阀静态和动态性能流场计算降阶模型；结合整车制动性能需求提出恒速/恒矩制动策略和方法，构建上述降阶协同仿真模型并进行试验验证。本项目的研究旨在揭示缓速器气液两相流体流动特性，提高缓速器制动动态响应性能，为我国自主研制高性能液力缓速器奠定理论和技术基础。

本项目以车用主流辅助制动元件液力缓速器为研究对象，为提升液力缓速器制动动态响应性能，开展其叶栅及充放油系统内部气液两相流动规律研究，以保证卡车、大客车和装甲车等重型车辆的高速及下长坡等工况的行车安全性。开展了两相流动制动特性预测方法与叶栅参数对其影响规律研究，面向快速响应的充放油系统的建模与分析，缓速制动特性降阶建模与快速响应制动策略研究，以及缓速器制动特性试验研究与验证。提出液气两相流动部分充液制动稳态和瞬态特性预测模型，以及以此为基础的双循环圆缓速器叶栅系统参数化设计优化方法；提出缓速器瞬态流场的本征正交分解降阶方法并获得其模态分布规律，从含能比例角度利用前6阶流场对原始流场重构且误差小于5%，将本征正交分解与代理模型方法相结合实现基于高含能阶次流场分布的制动转矩快速准确预测。提出面向快速响应的一种带反馈的液力缓速器充液率电液比例控制系统和集成阀系方案；构建充放液系统插装阀液动力表达式及阀系动态特性模型，获取了动态制动过程流动参数随充液率的变化规律；分别以比例电磁阀和插装阀响应时间与油压超调量为目标，选取阀芯直径和倒角等设计参数优化，在给定响应时间内油压波动幅值得到有效抑制且降幅可达49%，并进行了优化前后对比试验验证。建立考虑进出口流量的液力缓速器轮腔和充放油系统快速协同计算模型，提出PID与模糊并联控制方法实现车辆恒速和恒减速制动策略，实现制动转矩快速响应与精确控制。样机制动转矩调节误差小于5.5%，起效时间小于1.2s，较参考样机起效用时降低60%，制动转矩稳态与动态误差分别为1.2%与5.27%，验证了集成计算模型具有良好的稳态与动态预测精度。本项目通过揭示液力缓速器在不同充液率下气液两相流动特性形成机制，开展面向快速响应充放油液压系统动态特性研究，构建基于流场降阶模型理论的快速协同仿真模型，实现了车用液力缓速器充液率及其对应制动转矩的快速响应和精确控制，改善和提升了重型车辆动态制动性能和行车安全性。