二甲醚预混合燃烧系统控制阀工作特性研究

发布时间：2019-05-11 17:42

【摘要】：近年来,随着汽车工业的迅速发展,能源短缺和环境污染两大难题越发引人关注,寻找新的发动机清洁代用燃料及优化燃烧效率十分有必要。二甲醚(Dimethyl Ether,简称DME)十六烷值高、碳烟排放为零,具有作为柴油机清洁替代燃料的潜力。类似HCCI燃烧模式的二甲醚预混压燃(Premixed Charge Compression Ignition,简称PCCI)燃烧,由于其具有良好的操作性,受到学者们的高度关注。位于二甲醚发动机两燃烧室通道中的控制阀是实现二甲醚高效PCCI燃烧模式的关键,对控制阀驱动方式的设计及动态响应特性的探究显得尤为重要。首先,本文结合控制阀的工作特性,提出了电液控制系统。介绍了电液控制系统的组成结构,阐述了该系统在二甲醚PCCI燃烧模式下的具体工作过程,建立了数学模型,分析了影响控制阀动态特性的主要参数。根据二甲醚发动机实际工作需求,分析了控制阀工作过程中需要满足的动态特性要求。其次,根据电液控制系统工作原理,运用AMESim软件搭建仿真模型。揭示了系统供给压力、液压活塞直径、控制阀质量、复位弹簧刚度、供油管长度等主要因素对控制阀动态特性的影响规律及正时、升程的可变控制特性。结果表明:系统供给压力、液压活塞直径越大,控制阀最大升程及速度越大,液压活塞直径对阀门在最大升程处震荡频率影响较大;阀体质量对控制阀最大升程及速度影响不大,但对阀门在最大升程处的振幅影响较大;复位弹簧刚度越大,控制阀最大升程越小,同时关闭所需时间也越短;供油管长度对控制阀动态特性影响不大。最后,针对控制阀落座冲击问题采取阻尼孔液压制动和PID闭环控制策略进行优化设计。采用AMESim优化设计功能并借助遗传算法求得合适的PID控制参数,并运用到闭环控制仿真模型中进行仿真计算。结果表明,采用节流阀阻尼孔液压制动闭环控制策略后,控制阀的落座速度从2m/s左右下降到0.35m/s左右,能很好地满足阀门落座速度要求,从而实现对控制阀落座的柔性控制。
[Abstract]:In recent years, with the rapid development of automobile industry, energy shortage and environmental pollution have attracted more and more attention. It is necessary to find new engine clean alternative fuel and optimize combustion efficiency. Dimethyl ether (Dimethyl Ether, (DME) has the potential to be used as clean alternative fuel for diesel engine because of its high cetane number and zero soot emission. (Premixed Charge Compression Ignition, (PCCI) combustion, which is similar to HCCI combustion mode, has attracted great attention of scholars because of its good operation. The control valve located in the two combustion chamber channels of dimethyl ether engine is the key to realize the high efficiency PCCI combustion mode of dimethyl ether. It is particularly important to explore the design of the driving mode and the dynamic response characteristics of the control valve. First of all, combined with the working characteristics of the control valve, the electro-hydraulic control system is proposed in this paper. The composition and structure of the electro-hydraulic control system are introduced, the concrete working process of the system in dimethyl ether PCCI combustion mode is described, the mathematical model is established, and the main parameters affecting the dynamic characteristics of the control valve are analyzed. According to the actual working requirements of dimethyl ether engine, the dynamic characteristics of the control valve are analyzed. Secondly, according to the working principle of electro-hydraulic control system, the simulation model is built by using AMESim software. The influence of the main factors, such as supply pressure, hydraulic piston diameter, control valve quality, reset spring stiffness and supply tubing length, on the dynamic characteristics of the control valve and the variable control characteristics of timing and lift are revealed. The results show that the larger the hydraulic piston diameter is, the greater the maximum lift and speed of the control valve are, and the hydraulic piston diameter has a great influence on the vibration frequency of the valve at the maximum lift. The mass of the valve body has little effect on the maximum lift and speed of the control valve, but has a great influence on the amplitude of the valve at the maximum lift, the greater the stiffness of the reset spring, the smaller the maximum lift of the control valve, and the shorter the closing time. The length of tubing has little effect on the dynamic characteristics of control valve. Finally, the damping hole hydraulic braking and PID closed-loop control strategy are adopted to optimize the control valve seat impact problem. The appropriate PID control parameters are obtained by using AMESim optimization design function and genetic algorithm, and applied to the closed-loop control simulation model for simulation calculation. The results show that the positioning speed of the control valve decreases from about 2m/s to about 0.35m/s after adopting the closed-loop control strategy of damping hole hydraulic braking of throttle valve, which can meet the requirements of valve seating speed. So as to realize the flexible control of the control valve seat.
【学位授予单位】：武汉科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.13

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