汽车工程

汽车工程 ›› 2022, Vol. 44 ›› Issue (1): 52-57.doi: 10.19562/j.chinasae.qcgc.2022.01.007

所属专题： 发动机&排放专题2022年

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CNG发动机缸内气流条件与双点点火对火焰传播特性及热效率的影响

杨淼,林学东,李德刚(),刘迎澍   

  1. 吉林大学，汽车仿真与控制国家重点实验室，长春 　130022
  • 收稿日期:2021-08-26 修回日期:2021-10-07 出版日期:2022-01-25 发布日期:2022-01-21
  • 通讯作者: 李德刚 E-mail:ldg@jlu.edu.cn
  • 基金资助:
    吉林省发改委产业技术研究与开发资助项目(2016C038);吉林省科技发展计划资助项目(20150101032JC);吉林大学研究生创新研究计划(101832018C201)

Effect of Air Flow Conditions in Cylinder and Double-Point Ignition on Flame Propagation Characteristics and Thermal Efficiency of CNG Engine

Miao Yang,Xuedong Lin,Degang Li(),Yingshu Liu   

  1. Jilin University，State Key Laboratory of Automotive Simulation and Control，Changchun 　130022
  • Received:2021-08-26 Revised:2021-10-07 Online:2022-01-25 Published:2022-01-21
  • Contact: Degang Li E-mail:ldg@jlu.edu.cn

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摘要：

提高CNG-DI发动机的指示热效率是适应低碳化要求的重要途径。采用CFD软件AVL FIRE，对2.0 L柴油机改装的CNG-DI发动机燃烧过程和缸内流场特性进行了仿真分析。首先用CNG-DI光学发动机实验结果验证了计算模型的正确性。基于仿真模型分析了CNG燃料缸内直喷时不同燃烧室结构的湍流强度对火焰传播过程的影响，以及双点点火模式对平顶燃烧室火焰传播速度的影响。结果表明，燃烧室形状对湍流特性和浓度场分布特性有较大影响。湍流强度的增加加速了火焰的传播过程，但湍流强度过大会导致火焰表面断裂，局部燃烧不充分，使得燃烧效率下降，从而导致指示热效率下降。双点点火不仅能增大火焰前锋面积，而且能在两火焰团之间形成相互驱动效应，燃烧更加充分，从而提高指示热效率。

关键词: 火焰传播, 指示热效率, 双点点火, 驱动效应

Abstract:

Improving the indicative thermal efficiency of CNG-DI engine is an important way to meet the requirements of low carbonization. In this paper， CFD software AVL FIRE is used to simulate and analyze the combustion process and in-cylinder flow field characteristics of CNG-DI engine modified with 2.0 L diesel engine. Firstly， the correctness of the calculation model is verified by experimental results of CNG-DI optical engine. Then， based on the simulation model， the effect of turbulence intensity of different combustion chamber structures on flame propagation process in CNG direct injection and the effect of double point ignition mode on flame propagation velocity in flat top combustion chamber are analyzed. The results show that the shape of combustion chamber has great influence on turbulence characteristics and concentration field distribution characteristics. The increase of turbulence intensity accelerates the flame propagation process， but excessive turbulence intensity will lead to the fracture of flame surface and insufficient local combustion， which will reduce the combustion efficiency and thus lead to the decline of indicating thermal efficiency. Double point ignition can not only increase the flame front area， but also form mutual driving effect between the two flame masses， with more sufficient combustion， so as to improve the indicating thermal efficiency.

Key words: flame propagation, indicating thermal efficiency, double point ignition, driving effect