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在一台高压共轨重型柴油机上进行基于EGR技术的排放试验,对比研究了5个不同功率段(升功率分别为23.9、25.5、28.2、29.8和30.7kW/L)柴油机匹配单级增压和二级增压的性能与排放特性,探寻了采用EGR满足不同升功率柴油机的国-Ⅳ技术路线。试验结果表明:随功率段增加,二级增压比单级增压能显著改善中低转速全负荷时NOx与BSFC和碳烟之间的平衡关系,单级增压受EGR引入能力较弱和涡前温度较高双重限制,高功率段中低转速全负荷的NOx比排放难以降低到国-Ⅳ限值以下。ESC测试循环表明:碳烟和CO加权比排放随功率段降低而下降,但HC加权比排放随功率段降低而增加;在中小功率段(23.9、25.5和28.2kW/L),单级增压和二级增压NOx和碳烟加权比排放相当,2种增压方式都能在无后处理情况下使各项排放指标均满足国-Ⅳ排放法规,但单级增压的加权BSFC低于二级增压;随升功率增加,在高功率段(29.8和30.7kW/L),单级增压仅采用EGR技术难以实现国-Ⅳ的重型柴油机排放控制,而采用二级增压耦合EGR仍能在无后处理或简单后处理条件下使各项排放指标达到国-Ⅳ法规要求。
In a high-pressure common rail heavy-duty diesel engine based on EGR technology emission test, comparative study of five different power segments (liter power respectively 23.9,25.5,28.2,29.8 and 30.7kW / L) diesel matching single-stage supercharging and Secondary booster performance and emission characteristics, to explore the use of EGR to meet different liter power diesel engine national IV technical route. The experimental results show that with the increase of power section, the second-stage supercharging can significantly improve the balance between NOx and BSFC and soot at medium and low speed with full load, and the single-stage supercharging is weaker by the introduction of EGR Double high temperature before the eddy current limit, high-power section of low-speed full load NOx emissions is difficult to reduce the national IV limit below. The ESC test cycle showed that the emission of soot and CO decreased with the decrease of power, but the emission of HC increased with the decrease of power. In the middle and low power section (23.9, 25.5 and 28.2 kW / L) Compared with the second-stage pressurized NOx and soot, the two kinds of supercharging methods can make all the emission indexes satisfy the national-Ⅳ emission regulations without any reprocessing, but the single-stage supercharged weighted BSFC is lower than With the increase of power, it is hard to realize the national-Ⅳ heavy-duty diesel engine emission control in the high-power stage (29.8 and 30.7kW / L) Still can be no post-treatment or simple post-processing conditions so that the emission targets meet the national-Ⅳ regulatory requirements.