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从循环控制的角度,详细研究了LPG点燃式发动机冷起动首循环NO瞬态排放特性。实验在一台电控LPG进气道喷射单缸风冷四冲程125 cm3发动机上进行。通过高速采集系统记录发动机首循环瞬态NO排放、瞬时缸压和转速,从实验结果中分析发动机NO瞬态排放与其他参数之间的关系。研究表明:在稀燃工况下NO排放能更准确地反映着火的发生,可以作为首循环着火的判断依据;NO排放和循环缸压都随过量空气系数先增大后减小,最大缸内爆发压力发生在略浓的混合气浓度,而最大NO排放发生在较稀的混合气浓度; NO瞬态排放随循环缸压在稀燃、过渡和浓燃区呈现出不同的变化规律,首循环最佳过量空气系数应控制在过渡区域。
From the perspective of cycle control, the transient characteristics of transient NO emission during the cold start of LPG ignition engine are studied in detail. Experiments were performed on an electrically controlled LPG inlet single cylinder air-cooled four-stroke 125 cm3 engine. Through the high-speed acquisition system, the transient NO emissions, instantaneous cylinder pressure and rotational speed of the engine were recorded, and the relationship between the transient NO emission and other parameters was analyzed from the experimental results. The results show that the NO emission can reflect the occurrence of fire more accurately under the lean burning condition, which can be used as the judgment basis of the first cycle ignition. The NO emission and the circulation cylinder pressure first increase and then decrease with the excess air coefficient, The pressure of outburst occurred at a slightly rich mixture concentration, while the maximum NO emission occurred at a leaner mixture gas concentration. The transient discharge of NO with cyclic pressure showed different variation in lean burn, transition and rich combustion zone. The first cycle The best excess air ratio should be controlled in the transition area.