进气节流对柴油机低负荷性能影响的试验研究

摘要

在柴油机上加装节流阀是提升小负荷工况排温、改善排放的途径之一,但会对柴油机的其他性能造成影响.本研究通过给柴油机加装节流阀,研究了进气节流对柴油机小负荷工况性能的影响.试验结果表明:进气节流对柴油机的排温和NOx排放提升明显;柴油机进气节流后缸内压力下降,缸内平均燃烧温度、机械效率升高,滞燃期延长,燃烧始点后移;中低转速小负荷工况,随着节流程度的增加,燃油消耗率和烟度增加;高转速小负荷工况,一定范围内通过进气节流可以实现燃油消耗率和烟度的降低.2 500 r/min,29 N·m工况,保持EGR阀全开,随着节流程度的增加,NOx和烟度出现同时下降趋势,当空气流量由191.4 kg/h降至140.6 kg/h时,燃油消耗率、NOx、烟度分别下降了7.9%,58.1%,27.3%,排温提升了42.5%.%Equipping diesel engine with intake throttle valve is one of the ways to raise exhaust temperature of low load conditions and improve emission,but it will affect other performances of diesel engine.In the following,the effects of intake throttling on low load performance of diesel engine were discussed.The experimental results showed that intake throttling would result in the increase of exhaust temperature and NOx emission.In addition,the in-cylinder pressure decreased,the average combustion temperature and mechanical efficiency increased,the ignition delay period extended and the combustion starting point retarded.The brake specific fuel consumption and smoke increased with the increase of throttling degree under the conditions of low load at medium and low speed,but would decrease though throttling under the conditions of low load at high speed.At speed of 2 500 r/min and torque of 29 N·m,the NOx and smoke emission of diesel engine with fully-open EGR decreased with the increase of throttling.The brake specific consumption,NOx and smoke emission decreased by 7.9%,58.1% and 27.3% respectively and the exhaust temperature increased by 42.5% when the intake mass flow decreased from 191.4 kg/h to 140.6 kg/h.