Active control of high speed compression pre-mixture with suppression effect of radical consumers on low temperature oxidation

在均质压燃发动机的压缩冲程早期，从进气歧管和水中引出具有两阶段点火的高可燃性燃料，或直接喷射不表现出低温氧化的低可燃性燃料以抑制着火。它们的定量天平被灵活地控制，以根据操作条件优化点火正时。通过喷水或喷醇，实现了超低NOx和无烟燃烧，在较宽的工作范围内不爆燃或不着火。喷水显著减少了低温氧化，抑制了高温氧化引起的装料温度升高和快速燃烧。在降低燃烧效率的同时，喷水降低了缸内气体的最高温度，从而抑制了快速燃烧。因此，需要将最高装药温度控制在一个极其有限的范围内，以保持温和燃烧和高燃烧效率之间的满意折衷。醇对低温氧化的抑制作用比其他含氧或非含氧碳氢化合物、水和氢更强。用甲醇进行的化学动力学模拟表明，在低温氧化开始之前，羟基发生了还原，这可能是醇抑制低温氧化的主要机制。低压缩比、低辛烷值燃料与直接喷甲醇相结合，可以根据工况灵活地控制低温氧化，从而扩大了工作负荷范围。甲醇在均质压燃燃烧中的着火抑制作用远强于其他辛烷值相近的燃料。

High ignitability fuel, which exhibits two-stage ignition, was induced from the intake manifold and water or a low ignitability fuel, which does not exhibit low temperature oxidation, was directly injected early in the compression stroke for ignition suppression in an HCCI engine. Their quantitative balance was flexibly controlled to optimize ignition timing according to operating condition. Ultra-low NOx and smokeless combustion without knocking or misfiring was realized over a wide operating range with water or alcohol injection. The water injection significantly reduced the low temperature oxidation, which suppressed the increase in charge temperature and the rapid combustion caused by the high temperature oxidation. Rapid combustion was suppressed by reductions in the maximum in-cylinder gas temperature due to water injection while the combustion efficiency suffered. Therefore, the maximum charge temperature needs to be controlled within an extremely limited range to maintain a satisfactory compromise between mild combustion and high combustion efficiency. Alcohols inhibit low temperature oxidation more strongly than other oxygenated or unoxygenated hydrocarbons, water, and hydrogen. Chemical kinetic modeling with methanol showed a reduction of OH radical before the onset of low temperature oxidation, and this may be the main mechanism by which alcohols inhibit low temperature oxidation. A combination of lower compression ratio and lower octane number fuel with direct methanol injection can expand the operating load range envelope as low temperature oxidation can be flexibly controlled with methanol injection according to operating condition. The ignition suppression effect of methanol in HCCI combustion is much stronger than those of other fuels with similar octane number.