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

在 HCCI 发动机中，从进气歧管和水诱导具有两级点火的高可燃性燃料或在压缩冲程早期直接喷射不表现出低温氧化的低可燃性燃料以抑制点火。它们的定量平衡被灵活控制，以根据工况优化点火正时。通过喷水或喷醇，在较宽的工作范围内实现了超低 NOx 和无烟燃烧，无爆震或失火。注水显着减少了低温氧化，从而抑制了由于高温氧化引起的进气温度升高和快速燃烧。由于注水导致缸内气体最高温度降低，从而抑制了快速燃烧，同时燃烧效率受到影响。因此，最高充气温度需要控制在极其有限的范围内，以在温和燃烧和高燃烧效率之间保持令人满意的折衷。醇比其他含氧或未含氧碳氢化合物、水和氢更能强烈地抑制低温氧化。甲醇化学动力学模型显示，在低温氧化开始之前，OH自由基减少，这可能是醇类抑制低温氧化的主要机制。较低压缩比和较低辛烷值燃料与直接甲醇喷射的组合可以扩大运行负荷范围，因为低温氧化可以根据工况通过甲醇喷射灵活控制。甲醇在HCCI燃烧中的着火抑制作用比辛烷值相近的其他燃料强得多。

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.