In order to study the effect of negative valve overlap on combustion and emission characteristics of a homogeneous charge compression ignition engine fueled with natural gas and hydrogen, the test and the simulation were conducted using an engine cycle model coupling the chemical kinetic reaction mechanism under different valve timing conditions. Results show that the internal EGR formed by using negative valve overlap could heat the inlet mixtures and improve the spontaneous ignition characteristic of the engine. The residual exhaust gas could slow down the heat release rate, decrease the pressure rise rate and the maximum combustion temperature, and reduce the NO_x emission simultaneously. Among the three NVO schemes, the strategy of changing the intake valve opening timing individually can create the least power loss, and the symmetric NVO strategy which changes both the exhaust valve closing timing and the intake valve opening timing simultaneously can achieve the best heating effect of inlet mixtures and the satisfactory decrease of combustion temperature, as well as the largest reduction of NO_x emission.

中文翻译：

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负气门重叠对加氢CNG燃料HCCI发动机燃烧和排放的影响

为了研究负气门重叠对以天然气和氢气为燃料的均质充量压缩点火发动机的燃烧和排放特性的影响，采用结合了不同气门下化学动力学反应机理的发动机循环模型进行了测试和模拟。时间条件。结果表明，利用负气门重叠形成的内部EGR可以加热进气混合物，并改善发动机的自燃特性。残余废气可以减慢热释放速率，降低压力升高率和最大燃烧温度，并减少NO _X同时发射。在这三种NVO方案中，单独改变进气门打开正时的策略可以产生最小的功率损失，而同时改变排气门关闭正时和进气门打开正时的对称NVO策略可以达到最佳的加热效果。入口的混合物和燃烧温度的下降令人满意，以及NO的最大减少_X排放。