CAJ | 학술논문

为降低HCNG发动机NOx 排放，采用负阀重叠EGR策略，利用AVL‐Fire软件对 HCNG发动机不同进气门开启角（θIVO ）下的进气过程和燃烧过程进行了三维仿真计算，对比分析了采用负阀重叠前后发动机缸内EGR分布和燃烧过程。仿真结果表明：负阀重叠EGR策略下，排气门关闭角（θEVC ）固定为340°曲轴转角不变，当θIVO为380°曲轴转角时，既可避免发生回火又能保证一定的进气量及充气效率；采用负阀重叠后，在压缩冲程后期，缸内EGR率呈梯度分布（靠近火花塞位置EGR率较低），更有利于着火及火焰传播；采用负阀重叠可降低缸内最高燃烧压力及最高温度，但会减少进入气缸的新鲜工质，降低发动机功率；通过负阀重叠实现内部 EGR可降低NOx 排放，但会导致着火困难，燃烧速度变慢；提高点火能量可缩短着火落后期和燃烧持续期，加快燃烧速度。
위강저HCNG발동궤NOx 배방，채용부벌중첩EGR책략，이용AVL‐Fire연건대 HCNG발동궤불동진기문개계각（θIVO ）하적진기과정화연소과정진행료삼유방진계산，대비분석료채용부벌중첩전후발동궤항내EGR분포화연소과정。방진결과표명：부벌중첩EGR책략하，배기문관폐각（θEVC ）고정위340°곡축전각불변，당θIVO위380°곡축전각시，기가피면발생회화우능보증일정적진기량급충기효솔；채용부벌중첩후，재압축충정후기，항내EGR솔정제도분포（고근화화새위치EGR솔교저），경유리우착화급화염전파；채용부벌중첩가강저항내최고연소압력급최고온도，단회감소진입기항적신선공질，강저발동궤공솔；통과부벌중첩실현내부 EGR가강저NOx 배방，단회도치착화곤난，연소속도변만；제고점화능량가축단착화락후기화연소지속기，가쾌연소속도。
In order to reduce NOx emission of hydrogen‐enriched compressed natural gas (HCNG) engine ,3D simulation of intake and combustion process under different intake valve open (IVO) timings was conducted with AVL‐Fire software based on EGR strategy of negative valve overlap (NVO) .The simulation results show that the EGR strategy can not only avoid the backfire but also guarantee a certain intake mass flow and charging efficiency when the IVO timing is 380° and the exhaust valve closure (EVC) timing is 340° .EGR concentration shows a gradient distribution of low value near the spark plug at the late of compression stroke by using NVO ,which is beneficial to ignition and flame propagation .Moreover ,the NVO can decrease the maximum in‐cylinder pressure and temperature ,but reduces the fresh working gas with the loss of engine power .In addition , NVO can realize internal EGR with NOx reduction ,but leads to difficult ignition by slowing the combustion .Ignition delay and combustion duration shortens by improving the ignition energy ,and then the combustion accelerates .