柴油喷雾近场初次破碎微观特性可视化试验研究

Visual Study on Microscopic Characteristics of Diesel Spray Near-field Primary Breakup

利用电控高压共轨系统对单孔喷油器近喷孔区微观喷雾特性及表面波形成和发展过程进行了可视化研究和探索。采用激光诊断技术、显微技术与高速摄影技术结合的新方法,得到了放大12倍的近喷孔区4mm内微观喷雾场图像,以及近喷孔区表面波和丝状油滴的生成及发展过程图像。基于Matlab软件对图像进行后处理,得到了清晰的近场喷雾轮廓,在此基础上获得了表面波形态。试验结果表明:压力升高液滴分布更加均匀,初始表面波生成更靠近喷孔出口;表面波波长和振幅没有明显函数关系,但其各自增长有一定的规律性;通过背光法试验研究发现,压力较低时,出口油束边缘整齐,未发生雾化破碎。随着压力升高,油束出喷孔整齐段逐渐减小直至消失,表明喷射压力对燃油初次破碎以及液核表面波生成和发展有重要影响。

The microscopic spray characteristics and the surface wave formation and development near the injection orifice re-gion of injector were visualized by the electronically-controlled high-pressure common-rail system .With the combination of laser diagnostic technology ,microscopy and high-speed photography technology ,the 12 times magnified images of microscopic spray within 4 mm areas from the orifice and the formation and development images of surface wave and ligament were acquired . Based on the second processing of image with Matlab software ,the clear outline of near-field spray was acquired and hence the pattern of surface wave was acquired .The experimental results show that the increased pressure can make the droplet distribu-tion more homogeneous and the initial surface wave closer to the orifice .The wave length and amplitude of surface wave have no obvious functional relation ,but each of them increases regularly .It is found by using the back illumination method that the brim of exit oil beam is regular without the spray breakup at the lower pressure .With the increase of pressure ,the regular part of oil beam reduces and even disappears ,which improves that the injection pressure has a large influence on fuel primary break-up and surface wave formation and development .