吉林大学学报(工学版) ›› 2022, Vol. 52 ›› Issue (10): 2234-2243.doi: 10.13229/j.cnki.jdxbgxb20210316

• 车辆工程·机械工程 • 上一篇    

针阀运动规律及其对喷嘴内流和喷雾特性影响

赵文伯(),李玉洁,邓俊,李理光,吴志军()   

  1. 同济大学 汽车学院,上海 201804
  • 收稿日期:2021-04-12 出版日期:2022-10-01 发布日期:2022-11-11
  • 通讯作者: 吴志军 E-mail:0713_zhaowenbo@tongji.edu.cn;zjwu@tongji.edu.cn
  • 作者简介:赵文伯(1990-),男,博士研究生.研究方向:燃料喷射与雾化.E-mail:0713_zhaowenbo@tongji.edu.cn
  • 基金资助:
    国家自然科学基金重点项目(U1832179);上海市自然科学基金项目(19ZR1460200)

Needle motion and its influence on in-nozzle flow and spray jet characteristics

Wen-bo ZHAO(),Yu-jie LI,Jun DENG,Li-guang LI,Zhi-jun WU()   

  1. School of Automotive Studies,Tongji University,Shanghai 201804,China
  • Received:2021-04-12 Online:2022-10-01 Published:2022-11-11
  • Contact: Zhi-jun WU E-mail:0713_zhaowenbo@tongji.edu.cn;zjwu@tongji.edu.cn

摘要:

基于超快X射线成像技术研究了GDI喷油器针阀动力学特性和控制电流信号对针阀运动的影响规律。通过仿真计算分析了GDI喷嘴针阀抬升过程对内流空化现象和近场喷雾射流瞬态特性的影响,研究了针阀横向振动对于孔间不均匀性的影响。实验结果表明,针阀组件达到最大限位及落座时会与铁芯和阀座碰撞产生振荡,不利于喷油量的精确控制,减小控制电流能改善喷油控制精度。模拟结果表明,针阀抬升过程中,燃油在喷孔入口上表面产生空化,导致射流喷雾偏离喷孔轴线,最大偏转角可达到5°左右。喷射过程中喷雾油束的偏转会导致喷嘴沉孔出口位置积油,在燃烧的过程中产生积碳,影响发动机的颗粒物排放。在低针阀升程时,针阀横向振动会导致孔间流速不均匀,而随着针阀升程增加,孔间不均匀度显著降低。

关键词: 动力机械工程, 针阀运动规律, 超快X射线成像, 喷嘴内流, 空化, 孔间不均匀性

Abstract:

Needle dynamic characteristics and the influence of control current on needle motion about gasoline direct injection (GDI) nozzle were researched based on ultrafast X-ray imaging technology. Transient characteristics of in-nozzle flow and near-field spray jets during needle lift process and effects of cavitation were simulated based on a standard 8-hole GDI nozzle. A real needle motion profile obtained by ultrafast X-ray imaging technology was applied to reflect the influence of needle lateral vibration on hole-to-hole non-uniformity. The experimental results show that vibration occurs when needle module collides with iron core in the opening stage and with needle seat in the closing stage, which makes it difficult to control fuel injection precisely. Reduction of control current contributes to less vibration and more precise fuel injection. The simulation results show that cavitation at the upper face of nozzle leads to hydraulic flip phenomenon, so the fuel jet deviates from nozzle axis. Such kind of jet deflection is enhanced by intense entrainment between the jet and the ambient gas, and the maximum deflection angle is up to 5°. The jet deflection will cause nozzle tip wetting at the lower boundary of the contour-bore surface, which will deteriorate the engine particle emissions performance. The study also indicates that the lateral vibration of needle results in non-uniform flow characteristics between different holes, and such non-uniformity decreases as the needle lifts higher.

Key words: power machinery and engineering, needle motion, ultrafast X-ray imaging, nozzle inflow, cavitation, hole-to-hole flow non-uniformity

中图分类号: 

  • TK411

图1

针阀运动规律实验平台"

图2

图像采集方向示意图"

表1

高速相机参数设置"

相机参数数值
帧率/(帧·s-140000
曝光时间/μs23.4
图像像素/pixel1024×512
像素尺寸/(μm·pixel-12.5

图3

互相关算法窗口设置"

图4

控制电流示意图"

表2

电流大小对实验方案的影响"

Il /ATl /msIh /ATh /ms
方案160.551.5
方案270.551.5
方案3100.551.5

表3

电流持续时间对实验方案的影响"

Il/ATl/msIh/ATh/ms
方案160.551.5
方案1h60.552.0
方案1l61.051.5

图5

针阀运动特性曲线"

图6

不同电流大小下针阀升程曲线"

图7

不同电流持续期的针阀升程曲线"

图8

Spray G几何模型"

表4

喷孔结构参数"

参 数数 值
喷油孔数量8
沉孔直径/mm0.388
沉孔长度/mm0.480
喷孔直径/mm0.165
喷孔长度/mm0.160
喷油孔轴线与喷嘴轴线夹角/(°)37

图9

网格划分示意图"

图10

实测与理论针阀升程曲线"

图11

针阀横向振动实测曲线"

图12

实测质量流量曲线[19]"

图13

压力与压差曲线"

表5

不同针阀抬升阶段定义"

阶段时间/ms
10.292~0.300
20.300~0.312
30.312~0.324
40.324~0.340

图14

阶段1喷嘴内流特性"

图15

阶段2喷嘴内流特性"

图16

阶段2中t=0.312 ms时刻速度分布图"

图17

阶段3喷嘴内流特性"

图18

阶段4喷嘴内流特性"

图19

有无针阀横向振动条件下z=0截面速度分布云图"

图20

有无针阀横向振动条件下孔6和孔2出口流速分布"

图21

有无针阀横向振动条件下孔6和孔2出口湍动能分布"

图22

孔2和孔6平均流速差"

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