动边界条件下喷油器三维流场分析

Three-Dimensional Flow Field Analysis of Fuel Injector Under Dynamic Boundary Conditions

摘要

以某大流量喷油器为研究对象，建立喷油器内部流道数学模型，利用喷油器流动特性实验结果对模型进行了验证，获得喷油器球阀与针阀的运动规律．以此为动边界，进行喷油器内燃油流动状态三维瞬态数值模拟，分析动边界条件下阀门及阀座处的空化效应以及阀门的位移对三维流场的影响．研究表明：在喷油全过程中，空化集中分布在阀门与阀座的密封环面处、喷孔入口处等流通截面变化大、压力突变快的区域；随着阀门的运动，阀门及阀座、喷孔等处的空化程度均在不断变化，针阀下降时喷孔处空化明显强于针阀上升时，且形成了超空化现象，喷孔入口处空化面积最高达 58.9％，是针阀完全开启时的 2.63 倍；连接控制腔的节流孔处随着阀门的运动会出现600 m/s 以上的高流速以及强烈的湍流，在连接回油室与控制腔的导流孔处也会出现大面积的蒸汽体积分数略低于5%的两相变化区域，造成孔内流速不稳定、局部压力波动，影响喷射精度．

Abstract

A mathematical model of the internal flow passage of a high-flow injector was established. The model was verified using the experimental results of the flow characteristics of the injector，and the motion laws of the ball and needle valves of the injector were obtained. Taking this as the dynamic boundary，a three-dimensional(3D)transient numerical simulation of the fuel flow state inside the injector was performed to investigate the cavitation effect at the valve and valve seat under dynamic boundary conditions，as well as the influence of the valve displacement on the 3D flow field. The findings reveal that throughout the injection process，cavitation is concentrated in regions with large flow cross-sectional changes and rapid pressure fluctuations，such as the sealing ring surface between the valve and valve seat and the nozzle entrance. As the valve moves，the cavitation degrees at the valve and valve seat，nozzle，and other locations change constantly. When the needle valve descends，the cavitation at the nozzle is significantly stronger than that when it rises，inducing a supercavitation phenomenon. The cavitation area at the nozzle entrance increases to approximately 58.9%，which is 2.63 times the value when the needle valve is fully open. At the throttle hole connecting the control chamber，a high flow velocity of over 600 m/s and intense turbulence occur as the valve moves. At the diversion hole connecting the return oil and control chambers，a large area of a two-phase change region with a steam volume fraction slightly lower than 5% also appears，causing unstable flow velocity and local pressure fluctuations in the hole，thereby affecting the injection accuracy.

关键词

喷油器 / 空化现象 / 针阀运动 / 球阀运动 / 动网格

Key words

fuel injector / cavitation phenomenon / needle valve movement / ball valve movement / dynamic mesh

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基金资助

天津市科技领军企业重大创新项目(23YDLOGX00080)