缸内直喷天然气发动机燃烧室选型及其混合气形成机理
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摘要
利用FIRE软件建立了2.0L型直喷CNG发动机的燃烧模型,在光学样机上对CNG燃料缸内直喷的燃烧模型进行验证的基础上,仿真研究了不同燃烧室形状对缸内微观物理场的影响,探索燃烧室形状对混合气形成机理和燃烧特性以及NO生成规律的影响。结果表明:CNG燃料缸内直喷时燃烧室形状对缸内湍流特性及浓度场分布特性,特别是对火花塞附近的浓度场和湍流特性的影响很大;NO生成量不仅取决于NO的反应速率,还与反应区域的面积和反应持续时间密切相关;当燃烧室采用直口且底部适当凸起的形状时,不仅有效抑制了NO的生成,而且可以有效控制火焰传播速度,有利于稀薄燃烧。
TThe combustion model of 2.0 LCNG-DI engine was built with software FIRE,and the model was verified on an optical prototype of CNG-DI engine.The effect of the combustion chamber shape on the micro-physical fields was studied to explore the influence of chamber shape on mixture formation mechanism,combustion characteristics and NO formation mechanism.Results show that the combustion chamber shape has significant influence on the turbulence characteristic of the cylinder and on the distribution of the concentration fields especially around the spark plug.The amount of NO is closely related not only to the NO reaction rate but also to the size of the reaction area and reaction duration when the CNG fuel is injected into the cylinder directly and ion burned thin,which can be controlled by rational design of the structure of the combustion chamber.
TThe combustion model of 2.0 LCNG-DI engine was built with software FIRE,and the model was verified on an optical prototype of CNG-DI engine.The effect of the combustion chamber shape on the micro-physical fields was studied to explore the influence of chamber shape on mixture formation mechanism,combustion characteristics and NO formation mechanism.Results show that the combustion chamber shape has significant influence on the turbulence characteristic of the cylinder and on the distribution of the concentration fields especially around the spark plug.The amount of NO is closely related not only to the NO reaction rate but also to the size of the reaction area and reaction duration when the CNG fuel is injected into the cylinder directly and ion burned thin,which can be controlled by rational design of the structure of the combustion chamber.
引文
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[15]胡江涛,姚春德,耿培林等.空气和甲烷/空气氛围中喷油压力对柴油燃烧特性的影响[J].内燃机学报,2017,35(4):289-296.Hu Jiang-tao,Yao Chun-de,Geng Pei-lin,et al.Effects of injection pressure on combustion characteristics of diesel fuel in air and premixed methane/air mixture atmosphere[J].Transactions of CSICE,2017,35(4):289-296.
[16]Wang Zhong-shu,Chen Wen-jing,Wang Dan,et al.A novel combustion evaluation method based on incylinder pressure traces for diesel/natural gas dual fuel engines[J].Energy,2016(115):1130-1137.
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[2]徐连华,姜立永.汽车代用燃料综述[J].吉林大学学报:工学版,1988(4):129-134.XuLian-hua,Jiang Liyong.An overview of alternative fuels for automobiles[J].Journal of Jilin University(Engineering and Technology Edition),1988(4):129-134.
[3]Tahira M M,Alia M S,Salim M A,et al,Performance analysis of a spark ignition engine using compressed natural gas(CNG)as fuel[J].Energy Procedia,2015,68:355-362.
[4]Baratta M,Rapetto N,Spessa E.Numerical and experimental analysis of mixture formation and performance in a direct injection CNG engine[C]∥SAE Paper,2012-01-0401.
[5]Bhasker J P,Porpatham E.Effects of compression ratio and hydrogen addition on lean combustion characteristics and emission formation in a compressed natural gas fuelled spark ignition engine[J].Fuel,2017,208:260-270.
[6]韩旭东,黄佐华,陈勤学,等.天然气发动机燃烧室对性能的影响及优化[J].内燃机学报,2017,35(3):215-222.Han Xu-Dong,Huang Zuo-hua,Chen Qin-xue,et al.Influence of combustion chamber on natural gas engine performance and optimization[J].Transactions of CSICE,2017,35(3):215-222.
[7]莫海俊,魏弟清,冒晓健,等.活塞形状对点燃式天然气发动机性能的影响[J].车用发动机,2013(3):45-49.Mo Hai-jun,Wei Di-qing,Mao Xiao-jian.Effect of piston shape on SI NG engine performance[J].Vehicle Engine,2013(3):45-49.
[8]林学东,丛春梅,陈雪梅,等.浅形缩口直喷式柴油机燃烧室结构特点及其对排放特性的影响[J].吉林大学学报:工学版,2005,35(1):18-23.Lin Xue-dong,Cong Chun-mei,Chen Xue-mei,et al.The structural characteristics of the combustion chamber and its influence on the emission characteristics of the shallow-shaped and shrink-nozzled direct injection diesel engine[J].Journal of Jilin University(Engineering and Technology Edition),2005,35(1):18-23.
[9]林学东,宋涛,冯先振,等.车用柴油机低排放缩口燃烧系统的优化[J].吉林大学学报:工学版,2007,37(1):54-59.Lin Xue-dong,Song Tao,Feng Xian-zhen,et al.Optimization of low emission miniaturized combustion system for automotive diesel engines[J].Journal of Jilin University(Engineering and Technology Edition),2007,37(1):54-59.
[10]杨立平,李君,高莹,等.燃烧室形状对天然气发动机缸内流动和燃烧过程的影响[J].吉林大学学报:工学版,2007,37(6):1257-1262.Yang Li-ping,Li Jun,Gao Ying,et al.The influence of combustion chamber shape on the flow and combustion process of natural gas engine cylinder[J].Journal of Jilin University(Engineering and Technology Edition),2007,37(6):1257-1262.
[11]张纪鹏,高青,梁宝山,等.天然气喷气压力和喷气相位对天然气/柴油双燃料发动机性能的影响[J].吉林大学学报:工学版,2000,30(3):5-8.Zhang Ji-peng,Gao Qing,Liang Bao-shan,et al.Effects of gas injection pressure and phase on performance of gas/diesel dual fuel engines[J].Journal of Jilin University(Engineering and Technology Edition),2000,30(3):5-8.
[12]Imran S,Emberson D R,Diez A,et al.Natural gas fueled compression ignition engine performance and emissions maps with diesel and RME pilot fuels[J].Applied Energy,2014,124:354-365.
[13]Wu Chong-min,Deng Kang-yao,Wang Zhen.The effect of combustion chamber shape on cylinder flow and lean combustion process in a large bore sparkignition CNG engine[J].Journal of the Energy Institute,2016,89(2):240-247.
[14]张武高,周明,欧阳明高,柴油、天然气双燃料发动机的燃烧特性分析[J].内燃机学报,2000,18(3):299-304.Zhang Wu-gao,Zhou Ming,Ouyang Ming-gao.Analysis on the combustion characteristics of diesel/CNG dual fuel engine[J].Transactions of CSICE,2000,18(3):299-304.
[15]胡江涛,姚春德,耿培林等.空气和甲烷/空气氛围中喷油压力对柴油燃烧特性的影响[J].内燃机学报,2017,35(4):289-296.Hu Jiang-tao,Yao Chun-de,Geng Pei-lin,et al.Effects of injection pressure on combustion characteristics of diesel fuel in air and premixed methane/air mixture atmosphere[J].Transactions of CSICE,2017,35(4):289-296.
[16]Wang Zhong-shu,Chen Wen-jing,Wang Dan,et al.A novel combustion evaluation method based on incylinder pressure traces for diesel/natural gas dual fuel engines[J].Energy,2016(115):1130-1137.
[17]林学东,顾静静,李德刚,等.柴油机燃烧室结构对混合气形成及燃烧特性的影响[J].吉林大学学报:工学版,2014,44(6):1647-1654.Lin Xue-dong,Gu Jing-jing,Li De-gang,et al.Influence of combustor structure on mixture formation and combustion characteristics of diesel engine[J].Journal of Jilin University(Engineering and Technology Edition),2014,44(6):1647-1654.