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首页> 外文期刊>International journal of engine research >In-cylinder soot imaging and emissions of stratified combustion in a spark-ignited spray-guided direct-injection gasoline engine
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In-cylinder soot imaging and emissions of stratified combustion in a spark-ignited spray-guided direct-injection gasoline engine

机译：火花点火喷雾引导直喷汽油机的缸内烟灰成像和分层燃烧排放

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摘要

The combustion in a spark-ignited spray-guided gasoline direct-injection engine operating in a stratified mode has been studied by in-cylinder imaging of the fuel, OH~*, and soot distributions. Information on the fuel distribution was obtained by laser-induced fluorescence imaging of the aromatic molecules in the gasoline. The OH~* and soot distributions were simultaneously visualized by detection of the natural emissions at 306 nm (OH~*) and around 530 nm (soot) using two intensified charge-coupled device cameras. In addition to the in-cylinder observations, engine-out soot emissions, NO_x, and HC were measured. The engine was operated at a speed of 2000 r/min and an indicated mean effective pressure of 2.5 bar, with a fully open throttle, resulting in a globally lean combustion with a fuel-air equivalence ratio of about 0.25. The gasoline was injected in single or double injections by an outward-opening piezo-actuated injector. The combustion was ignited efficiently at locally fuel-rich conditions. The soot formation and oxidation were investigated for the two injection strategies, each with three injection timings and two fixed ignition timings. The results showed that soot was efficiently formed and oxidized. From the in-cylinder measurements, it could be seen that the soot luminescence intensity quickly rose and then declined, while the combustion temperature was still increasing. Furthermore, the OH~* intensity was still increasing as the soot luminescence was declining. The soot incandescence peak intensity occurred at a crank angle degree close to 50 percent mass burned, and the OH~* intensity peak arose later, shortly before the maximum soot temperature around top dead centre (TDC). When the injection timing was retarded, with constant ignition timing with respect to injection, it was found that the total soot luminosity increased. In addition, less OH~* chemiluminescence was observed during the decrease of the soot incandescence, implying conditions less favourable for efficient soot oxidation in the later part of the combustion for retarded injections. This was confirmed by the engine-out soot emission measurements, which showed increased soot levels as the injection was retarded. It was also found that fuel impinged on the spark plug during the injections, resulting in a persistent jet flame close to the spark plug in the centre of the cylinder, which is believed to contribute to engine-out soot emissions.
机译：通过对燃料，OH〜*和烟尘分布的缸内成像，研究了以分层模式运行的火花点火式喷雾引导汽油直喷发动机中的燃烧。通过汽油中芳香族分子的激光诱导荧光成像获得有关燃料分布的信息。通过使用两个增强的电荷耦合器件相机检测306 nm（OH〜*）和530 nm（烟灰）附近的自然发射，可以同时显示OH〜*和烟灰分布。除了缸内观察之外，还测量了发动机排出的烟尘排放量，NO_x和HC。发动机以2000 r / min的速度运行，指示的平均有效压力为2.5 bar，节气门完全打开，从而导致整体稀薄燃烧，燃料/空气当量比约为0.25。汽油由向外打开的压电致动喷油器以单喷或双喷的方式喷射。在局部燃料丰富的条件下有效地点燃了燃烧。研究了两种喷射策略的烟灰形成和氧化，每种策略都有三个喷射正时和两个固定点火正时。结果表明，烟灰被有效地形成和氧化。从缸内测量可以看出，在燃烧温度仍在升高的同时，烟灰的发光强度迅速上升然后下降。此外，随着烟灰发光的下降，OH〜*强度仍在增加。烟灰白炽峰强度出现在接近燃烧的50％质量的曲柄角度上，并且OH〜*强度峰值出现在稍后，即在上死点（TDC）附近的最高烟灰温度之前。当延迟喷射正时时，相对于喷射具有恒定的点火正时，发现总的烟灰发光度增加。此外，在烟灰白炽度降低期间观察到较少的OH〜*化学发光，这意味着条件不利于在后期进行的延迟喷射燃烧的后期有效烟灰氧化。发动机熄灭的烟尘排放量测量结果证实了这一点，该测量结果表明，随着喷射延迟，烟尘水平升高。还发现，在喷射期间，燃料撞击在火花塞上，从而在气缸中心附近的火花塞附近产生持续的喷射火焰，据认为这有助于发动机排出的烟尘排放。

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