喷射时刻对甲醇发动机燃烧及非法规排放的影响
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摘要
针对甲醇发动机低温冷起动困难,在一台由1130单缸柴油机改造的直喷火花点火甲醇发动机上,利用商用CFD模拟软件AVL-Fire耦合甲醇氧化反应机理,通过电热塞将进气温度加热到283 K,研究了喷射时刻对甲醇发动机低温(266 K)冷起动燃烧及非法规排放的影响。结果表明:推迟喷射时刻能够改善缸内燃烧,使得缸内混合气能够得到较为充分燃烧,减小未燃甲醇排放,当喷射时刻由53°BTDC推迟到49°BTDC时,未燃甲醇排放显著减少;喷射时刻由57°BTDC推迟到49°BTDC时,甲醛排放增大,但当喷射时刻继续推迟到45°BTDC时,缸内最高燃烧温度超过1 200 K,使得甲醛快速氧化,甲醛排放显著减少。
For the problem of difficult cold start of methanol engine in low temperature, the effects of injection timing on low temperature combustion after cold start and unregulated emission were studied on a direct injection spark ignition methanol engine retrofitted from an 1130 single cylinder diesel engine by heating intake temperature to 283 K from 266 K based on CFD AVL-Fire coupling chemical kinetics reaction mechanism simulation. The simulation results show that retarding the injection timing can improve the in-cylinder combustion and reduce the unburned methanol emission due to the complete combustion of in-cylinder mixture. When the injection timing retards from 53°BTDC to 49°BTDC, the unburned methanol emission reduces remarkably. In addition, the formaldehyde emission increases when injection timing retards from 57°BTDC to 49°BTDC, but when it continues to retard to 45°BTDC, the combustion temperature exceeds 1 200 K so that the formaldehyde oxidizes rapidly and its emission becomes less obviously.
For the problem of difficult cold start of methanol engine in low temperature, the effects of injection timing on low temperature combustion after cold start and unregulated emission were studied on a direct injection spark ignition methanol engine retrofitted from an 1130 single cylinder diesel engine by heating intake temperature to 283 K from 266 K based on CFD AVL-Fire coupling chemical kinetics reaction mechanism simulation. The simulation results show that retarding the injection timing can improve the in-cylinder combustion and reduce the unburned methanol emission due to the complete combustion of in-cylinder mixture. When the injection timing retards from 53°BTDC to 49°BTDC, the unburned methanol emission reduces remarkably. In addition, the formaldehyde emission increases when injection timing retards from 57°BTDC to 49°BTDC, but when it continues to retard to 45°BTDC, the combustion temperature exceeds 1 200 K so that the formaldehyde oxidizes rapidly and its emission becomes less obviously.
引文
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[2] 彭乐高,宫长明,宫宝利,等.富氧下甲醇发动机冷起动燃烧及非法规排放[J].内燃机学报,2017(5):423-428.
[3] 黄震,洪伟,姜恩伟,等.稀燃条件下甲醇汽油混合燃料颗粒物排放特性[J].车用发动机,2017(3):68-73.
[4] 温溢.乙醇汽油对车辆颗粒物排放的影响[J].车用发动机,2017(5):73-76.
[5] 张海燕,张仲荣,刘立东,等.汽油车尾气中醛酮类化合物排放特征的研究[J].汽车工程,2013,35(3):207-211.
[6] Gong C M,Peng L G,Liu F H.Modeling of the overall equivalence ratio effects on combustion process and un-regulated emissions of an SIDI methanol engine[J].Energy,2017,125:118-126.
[7] 李理光,王振锁,邓宝清,等.基于可控循环着火的电控汽油机冷起动性能研究[J].汽车工程,2004(4):417-422.
[8] Grotheer H H,Kelm S,Driverh S T,et al.Elementary reac-tions in the methanol oxidation system[J].Physical Chemistry Chemical Physics,1992,96:1360-1369.
[9] Zhen X D,Wang Y.Numerical analysis of knock during HCCI in a high compression ratio methanol engine based on LES with detailed chemical kinetics[J].Energy Conversion and Management,2015,96:188-196.
[10] Zhen X D,Wang Y.Numerical analysis on original emis-sions for a spark ignition methanol engine based on de-tailed chemical kinetics[J]. Renewable Energy,2015,81:43-51.
[11] Zhen X D,Wang Y.Study of ignition in a high compression ratio SI (spark ignition)methanol engine using LES(large eddy simulation) with detailed chemical kinetics[J].Energy,2013,59:549-558.
[12] 宫长明,王舒,刘家郡,等.环境温度对点燃式甲醇发动机冷起动性能的影响[J].吉林大学学报(工学版),2009(1):27-32.
[13] 刘方杰,刘圣华,魏衍举,等.甲醇氧化生成甲醛排放的影响因素[J].内燃机学报,2014,32(2):166-171.
[14] 甄旭东.火花点燃式甲醇发动机燃烧过程及爆震机理的研究[D].天津:天津大学,2014.
[15] Wei Y J,Liu S H,Liu F J,et al.Direct measurement of formaldehyde and methanol emissions from gasohol en-gine via pulsed discharge helium ionization detector[J].Fuel,2010,89:2179-2184.