With an electrical low-pressure impactor (ELPI) , the particle matter number of an off-road air-cooler diesel engine, a diesel engine and LNC engine were studied on the engine test bench. The test results showed that: at the maximum power mode and maximum torque mode, the PM emissions magnitude are 10~7 cm~3,10~6 cm~(-3),10~5 cm~(-3) for the off-road engine, diesel engine, LNG engine respectively, while their size distributions were totally different. At fixed engine speed, the brake specific PM number concentration of diesel engine increased with the increase in load. The brake specific PM number concen-tration of LNC engine showed an increasing trend and then decreasing trend with the increase of load. At fixed throttle opening, the brake specific PM number concentration of diesel engine decreased with the in-crease in speed, while the brake specific PM number concentration of LNC engine showed an increasing trend and then decreasing trend with the increase of engine speed. The CMD of LNG engine was smaller than that of diesel engine.%利用电子低压冲击仪(ELPI)在发动机台架上进行了非道路风冷柴油机、柴油机及LNG发动机排放颗粒物粒径及质量分布特征研究.试验结果表明:在最大功率点和最大转矩点,非道路柴油机排放微粒浓度最高,柴油机与LNG发动机依次相差一个数量级,且粒径分布结果截然不同;在转速不变时,随着负荷的增加柴油机的比排放数量浓度降低,LNG发动机却是先降低后增加;在油门开度不变时,随着转速的增加柴油机的比排放数量浓度增加,LNG发动机随转速的增加先增加后降低.对比二者的中位直径,LNG发动机要明显小于柴油机.
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