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An Investigation of Compressed Natural Gas Engine for Nitrogen Oxides Reduction | Science Publications

机译：压缩天然气发动机还原氮氧化物的研究科学出版物

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> Problem statement: This study describes the use of Reformer Gas (RG) to alter NOx emission in a CNG-fueled HCCI engine. Comparison with diesel, natural gas has a very high octane number (?120) and high auto-ignition temperature (?600°C). Composed mostly of methane, natural gas is the only common fuel to manifest relatively pure, single-stage combustion. Other fuels have stronger low-temperature reaction and the required entropy for main stage combustion can be obtained from the low temperature heat release as a result of compression to moderate pressure and temperature. In deviation, the methane molecule resists destruction by free radicals and produces negligible heat release at low temperature. In consequences, in CNG-fueled HCCI engines the activation energy required for auto-ignition must be obtained by extreme levels of charge heating and compression. This causes inherently to a high rate of heat release. HCCI operation with pure CNG fuel was attained but not really practical due to very high NOx production. While HCCI operation is usually described as a low NOx technique, the knocking behavior when running with pure CNG raised the peak combustion temperature to a value well above normal combustion and the critical Zeldovich NOx production threshold, giving very high indicated NOx emissions. Approach: One approach to improving these properties is to convert part of the base CNG fuel to Reformer Gas (RG). In this study, modified COMET engine was operated in HCCI mode using a mixture of CNG fuel and simulated RG (75% H2 and 25% CO) can be produced on-board from CNG using low current and non-thermal plasma boosted fuel converter. Results: This study shows that despite of having various RG mass fractions, ? was the dominant factor in reducing NOx production and increasing RG mass fraction had only a small effect on increasing NOx. This disconnect between the overall equivalence ratio and RG fraction shows that the real benefit of the RG blending was to enable lean (high) operation. Higher ? also effectively reduced maximum pressure and maximum pressure rate. Conclusion: Note that due to the low achievable power levels, the NOx emissions continue to be high and further combustion enhancements and more controlled combustion would be needed to make the CNG-fuelled HCCI engine practical.
机译： > 问题陈述：该研究描述了使用重整器气体（RG）来改变以CNG为燃料的HCCI发动机中NO x 的排放。与柴油相比，天然气具有很高的辛烷值（？120）和很高的自燃温度（？600°C）。天然气主要由甲烷组成，是唯一表现出相对纯净的单级燃烧的普通燃料。其他燃料具有更强的低温反应性，并且由于压缩到适度的压力和温度而从低温放热中可以获得主要燃烧所需的熵。与此相反，甲烷分子可抵抗自由基的破坏，并且在低温下释放的热量可忽略不计。结果，在以CNG为燃料的HCCI发动机中，必须通过极端程度的充气加热和压缩来获得自动点火所需的活化能。这固有地导致高的热释放率。 HCCI可以使用纯CNG燃料运行，但由于NO x 的产生量很高，因此并不实用。虽然HCCI操作通常被描述为低NO x 技术，但使用纯CNG运行时的爆震行为将峰值燃烧温度提高到远高于正常燃烧的值，并且临界Zeldovich NO x < / sub>生产阈值，给出很高的指示NO x 排放量。 方法：一种改善这些性能的方法是将部分基础CNG燃料转化为重整气（RG）。在这项研究中，改良的COMET发动机以HCCI模式运行，使用的是CNG燃料的混合物，并且可以在CNG上使用低电流和低压从船上生产模拟RG（75％H 2 和25％CO）的模拟RG。非热等离子体增压燃料转换器。 结果：该研究表明，尽管RG的质量分数各不相同，但？是减少NO x 产量的主要因素，而增加RG质量分数对增加NO x 的影响很小。总当量比和RG分数之间的这种脱节表明RG混合的真正好处是可以实现稀薄（高）运行。更高？还有效降低了最大压力和最大压力率。 结论：请注意，由于可达到的低功率水平，NO x 的排放量仍然很高，因此需要进一步的燃烧增强和更加可控的燃烧才能使CNG-加油的HCCI发动机实用。

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