高频机械-液压复合传动中的液压压力波动与液压迟滞现象

Fully variable valve system (FVVS) has a dramatic pressure fluctuation in the high speed and aggravates the phenomenon of hydraulic hysteresis, which lead the delay of the system response. In this paper, an integrated mechanical-hydraulic simulation calculation model was built. And the theoretical calculation was done by the finite element analysis technology of the fluid-solid coupling. In addition, some experiments were conducted by adopting the self-dependent principled prototype. The issue of the pressure fluctuation in mechanical-hydraulic transmission was researched by these means above. It was made clear that the influencing factors and the theory of the dramatic pressure fluctuation and the form of the gas-liquid two-phase flow. It was also revealed the influence rules of the pressure fluctuation with variable factors in high frequency mechanical-hydraulic transmission. Aiming at reducing the pressure fluctuation, a theory system of the new FVVS design was built by optimizing the structural parameters of the mechanical system and the fluid flow state in the hydraulic system. This theory system improved the maximum stable speed of the FVVS and promoted the all-round progress and the commercial production of this technology.

全可变液压气门系统存在高速时剧烈的液压压力波动并加剧了液压迟滞现象，导致该系统的响应速度降低。建立一体化的机械-液压仿真计算模型，通过液-固耦合有限元分析技术进行理论计算，采用自主创新研制的原理样机进行试验测量，研究这种机械-液压复合传动中的液压压力波动问题。探明机械-液压复合传动中加剧液压压力波动并形成气液两相流的影响因素和机理，揭示高频机械-液压复合传动中各种因素对液体压力波动的影响规律。以降低液体压力波动为优化目标，优化机械系统的结构参数和液压系统内的流体流动状态，建立一套全可变液压气门系统的新型设计理论体系，提高全可变液压气门系统的最高稳定转速，促进该项技术的全面进步和商品化生产。

全可变液压气门机构（Fully Hydraulic Variable Valve System, 简称FHVVS）可实现气门最大升程、气门开启持续角和配气相位三者的连续可变，对发动机的节能减排具有重大意义。由于全可变液压气门机构采用“凸轮传动＋液压传动”的复合传动方式，存在高速时剧烈的液压压力波动并加剧了液压迟滞现象，导致该系统的响应速度降低。本项目以BJ486EQ汽油机为载体，通过对FHVVS这种机械-液压复合传动的仿真计算和试验研究，探明了FHVVS系统中影响液压压力波动的主要因素和影响机理，揭示了高频机械-液压复合传动中运动件质量、液压容积和流场分布等因素对液体压力波动的影响规律。以降低液体压力波动为优化目标，优化机械系统的结构参数和液压系统内的流体流动状态，建立了一套全可变液压气门系统的新型设计理论体系。使 FHVVS系统的液压压力波动显著降低，使液压气门机构在非凸轮控制下实现平稳落座，并提高了全可变液压气门系统的最高稳定转速。.在取得理论成果的基础上，在BJ486EQ汽油机上研制了具有全可变液压气门机构FHVVS的高水平原理样机。该原理样机使FHVVS系统实现了在标定转速5000r/min下的稳定运转，并使BJ486EQ汽油机在无节气门状态下成功实现了点火运行。试验研究表明：与传统汽油机相比，搭载FHVVS系统的BJ486无节气门汽油机在中小负荷工况下的泵气损失的降低80%以上，燃油消耗率改善了6.2%-12.5%，达到了显著的节能效果