柴油机喷孔内流动及射流初始破碎过程研究

doi:10.13733/j.jcam.issn.2095-5553.2024.09.024

摘要/Abstract

摘要：

为研究喷孔内燃油流动特性与近孔区射流初始破碎的过程及影响因素，搭建柴油机燃油喷射雾化的可视化试验平台，采用高速可控闪光摄影及显微成像技术，同时，基于计算流体力学（CFD）软件 OpenFOAM、大涡模拟 LES（Large Eddy Simulation）理论和 VOF（Volume of Fluid）方法，分别开展柴油机喷孔内流动及喷雾特性可视化试验和数值计算。结果表明：喷孔内燃油流动呈现空穴流动，空穴从压力室开始，逐渐向喷孔内发展。喷油压力决定近嘴区射流破碎形式，喷油压力 20 MPa时，射流呈现 Rayleigh破碎；喷油压力 40 MPa时，射流呈现第一、第二风生破碎；喷油压力 60 MPa时，射流呈现雾化破碎。射流破碎从射流“伞形”头部开始，射流头部气/液相界面处存在很大的速度和压力差，引起射流头部的首先破碎。数值模拟还展现射流初次破碎以及液滴的二次破碎过程。

关键词: 喷孔内流, 射流破碎, 空化, 可视化试验, 大涡模拟

Abstract:

In order to study the characteristics of fuel flow in the nozzle and the process and influencing factors of jet initial breakup near the nozzle，a visual test platform for the fuel injection atomization in diesel was set up，the high.speed controlled flash photography and microscopic imaging technology were adopted，and based on computational Fluid dynamics（CFD）software OpenFOAM，large eddy simulation（LES）theory and volume of fluid（VOF）method，the visual test and numerical calculation of flow and spray characteristics in nozzle of diesel engine were carried out respectively. The results show that the fuel flow in the jet hole presents a cavity flow，which starts from the pressure chamber and gradually develops into the jet hole. The jet breaking form in the near nozzle region is influenced by oil injection pressure. When the injection pressure is up to 20 MPa，the jet breaking is appeared Rayleigh breakup. With the increase of injection pressure，the jet breaking are appeared the first and second wind breakup at 40 MPa，and atomization breakup at 60 MPa. The breakup of the jet is begun at the“Umbrella”head of the jet. A large velocity and pressure difference at the gas/liquid interface of the jet head is formed，which causes the first breakup of the “Umbrella”head. The breakup of the jet and the second breakup of the droplets are also shown in numerical calculation.

Key words: nozzle inner fuel, jet breakup, cavitation, validation experimental, large eddy simulation

中图分类号:

KT421

雷发林 , 高永强 , 陈修山 , 黄雪涛 , 周士谦 , 尹迁齐 . 柴油机喷孔内流动及射流初始破碎过程研究[J]. 中国农机化学报, 2024, 45(9): 159-165.

Lei Falin, Gao Yongqiang, Chen Xiushan, Huang Xuetao, Zhou shiqian, Yin qianqi. Study on internal flow in a injector of diesel engine and near-field jet breakup at the initial stage of injection[J]. Journal of Chinese Agricultural Mechanization, 2024, 45(9): 159-165.

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