Characteristics of Flash Boiling Fuel Sprays from Three Types of Injector for Spark Ignition Direct Injection (SIDI) Engines
Characteristics of Flash Boiling Fuel Sprays from Three Types of Injector for Spark Ignition Direct Injection (SIDI) Engines
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DOI：
10.1007/978-3-642-33841-0_33
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Gaoming Zhang;Min Xu;Yuyin Zhang;D. Hung
中科院分区：
文献类型：
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作者：
Gaoming Zhang;Min Xu;Yuyin Zhang;D. Hung
火花点火直喷（SIDI）汽油机采用高喷油压力来促进液体燃料在燃烧室内的雾化和汽化。然而，高燃油喷射压力通常会导致燃油喷雾穿透发动机气缸，导致壁和/或活塞湿润，从而导致发动机未燃烧碳氢化合物（UHC）和烟灰的高水平排放。近年来，人们发现燃料温度在喷雾雾化和汽化过程中起着重要的作用。特别是，当燃料的温度超过其局部沸点时，燃料过热并发生闪沸。多孔DI喷射器的闪沸喷雾实验表明，在过热条件下，喷雾会发生明显的结构转变。当出现闪沸现象时，雾化和汽化都得到了改善。同时，由于不同类型的SIDI发动机燃烧系统使用不同的喷油器配置来实现理想的混合气形成和燃烧，因此有必要将现有的闪沸喷雾知识从多孔喷油器扩展到其他类型的喷油器，并在相似的过热条件下表征它们的闪沸喷雾行为。本文在高压定容室中对多孔、旋流和外开三种SIDI喷射器的闪蒸喷雾进行了研究。主要的焦点是多孔喷油器的喷射，因为它在现代SIDI发动机中使用得最广泛。可以通过将喷油器放置在可热控制的夹具中来调节喷油器本体的温度。应用各种激光诊断来研究喷雾几何形状、流场、汽化和液滴尺寸分布。结果表明：闪蒸喷雾的特性主要受过热度（即燃油温度与沸点之差）的影响，对喷射压力的敏感性不如非闪蒸喷雾；三种喷射器的闪蒸喷雾结构与非闪蒸喷雾结构有显著差异。然而，与非闪蒸喷雾相比，喷嘴结构对闪蒸喷雾结构的影响不显著。研究表明，燃料温度可以作为控制喷雾结构、喷雾雾化和蒸发的有效参数。
Spark ignition direct injection (SIDI) gasoline engines employ high fuel injection pressure to promote the liquid fuel atomization and vaporization in the combustion chamber. However, high fuel injection pressures normally lead the fuel spray over penetrating in engine cylinder, resulting in wall and/or piston wetting which cause high level of engine unburned hydrocarbon (UHC) and soot emissions. Recently, it has been found the fuel temperature could play important roles in spray atomization and vaporization processes. Especially, when the temperature of the fuel exceeds its local boiling point, the fuel is superheated and flash boiling occurs. Experiments of flash boiling sprays from a multi-hole DI injector show that the spray would undergo significant structural transformation under the superheated conditions. Both the atomization and vaporization are improved when the phenomenon of flash boiling occurs. Meanwhile, since various types of SIDI engine combustion systems utilize different fuel injector configurations to achieve desirable mixture formation and combustion, it is necessary to extend the existing knowledge of flash boiling spray from multi-hole injector to other types of injector, and characterize their flash boiling spray behaviour under the similar superheated conditions. In this paper, flash boiling sprays from three types of SIDI injectors, namely, multi-hole, swirl and outward opening injectors are investigated at a high pressure constant volume chamber. The primary focus is the spray from a multi-hole injector as it is most widely used in modern SIDI engines. The temperature of the injector body can be regulated by placing the injector in a fixture which can be thermally controlled. Various laser diagnostics are applied to investigate the spray geometry, flow field, vaporization and droplet size distributions. The results show that the characteristics of flash boiling spray are mainly dominated by superheat degree, i.e., the difference between the fuel temperature and its boiling point, not as sensitive to the injection pressure as the non-flash boiling spray. The structures of flash boiling spray from all three types of injector differ from those of non-flash boiling spray significantly. However, the effects of injector configuration on the structure of flash boiling spray are insignificant, compared to the non-flash boiling sprays. This study reveals that using fuel temperature can be an effective parameter for controlling the spray structure, spray atomization and evaporation.