不同湿壁条件下喷雾碰壁燃烧过程分析
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摘要
利用定容燃烧弹试验装置,分别改变定容弹燃烧室内充气密度及喷油孔直径获得不同的湿壁条件,充气密度及喷孔直径范围分别为7.5～15.0kg/m~3及0.11～0.22mm,采用高速摄像机拍摄研究了不同湿壁条件对喷雾碰壁燃烧过程的影响。结果表明:喷雾燃烧滞燃期随充气密度的减小而增大,并且随着湿壁程度的增加而增加,滞燃期受充气密度的影响更显著。而在给定的高喷油压力高进气密度条件下,不同喷孔直径下的喷雾雾化效果都十分良好,喷雾着火主要受化学准备时间影响,滞燃期的波动不大。随着湿壁程度的加重,喷雾燃烧更晚进入高温着火阶段,后燃现象加重,燃烧持续期增长,碳烟的生成量急剧增多。
By using the wet conditions generated by changing the air change density(7.5kg/m~3 to15.0kg/m~3)and injection hole diameter(0.11 mm to 0.22mm)in a constant volume combustion chamber test device,a high-speed camera was used to study the effect of different wet wall conditions on the spray wall impingement combustion process.The ignition delay of spray combustion increases with the decrease of the air charge density and increases with the rise of wall humidity,but it is more significantly affected by the air charge density.For the given high fuel injection pressure and air intake density,spray atomization with different injection hole diameters is very good.The spray ignition is mainly influenced by the time of chemical preparation,and the fluctuation of ignition delay is not large.With the increase of humidity on the wall,the time for the spray burning to outer the high temperature ignition phase will be much later.Resulting in a serious post-combustion and increased combustion duration,which leads to a sharp increase in soot emissions.
By using the wet conditions generated by changing the air change density(7.5kg/m~3 to15.0kg/m~3)and injection hole diameter(0.11 mm to 0.22mm)in a constant volume combustion chamber test device,a high-speed camera was used to study the effect of different wet wall conditions on the spray wall impingement combustion process.The ignition delay of spray combustion increases with the decrease of the air charge density and increases with the rise of wall humidity,but it is more significantly affected by the air charge density.For the given high fuel injection pressure and air intake density,spray atomization with different injection hole diameters is very good.The spray ignition is mainly influenced by the time of chemical preparation,and the fluctuation of ignition delay is not large.With the increase of humidity on the wall,the time for the spray burning to outer the high temperature ignition phase will be much later.Resulting in a serious post-combustion and increased combustion duration,which leads to a sharp increase in soot emissions.
引文
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[3]NAOHITO K,MASAHIRO S,JIRO S,Characteristics of a diesel spray impinging on a flat wall[C/OL].SAE Paper,1989,890264.(1989-02-01)[2018-02-21].http://papers.sae.org/890264.
[4]DONALD W.Multi-dimensional modeling of heat and fuel films resulting from impinging spray[C/OL].SAE Paper,1998,980132.(1998-02-23)[2018-02-21].http://papers.sae.org/980132.
[5]邓鹏,黄荣华,张永林,等.一种预混燃烧加热式定容燃烧弹的研发[J].华中科技大学学报(自然科学版),2013,41(8):121-127.DENG P,HUANG R H,ZHANG Y L,et al.Development of a constant volume combustion bomb heated by premixed burning[J].Journal of Huazhong University of Science and Technology(Natural Science Edition),2013,41(8):121-127.
[6]MA Y J,HUANG R H,DENG P,et al.The development and application of an automatic boundary segmentation methodology to evaluate the vaporizing characteristics of diesel spray under enginelike conditions[J].Meas Sci Technol,2015,26(4):045004.
[7]BARDI M,PAYRI R,MALBEC L M.et al.Engine combustion network:comparison of spray development,vaporization,and combustion in different combustion vessels[J].Atomization and Sprays,2012,22(10):807-842.
[8]PICKETT L,LPEZ J.Jet-wall interaction effects on diesel combustion and soot formation[C/OL].SAE Paper,2005,2005-01-0921.(2005-04-11)[2018-02-21].http://papers.sae.org/2005-01-0921.
[9]GAYDON A G.The spectroscopy of flames[M].London:Chapman and Hall,1974.
[10]MUELLER C J,MARTIN G C.Effects of oxygenated compounds on combustion and soot evolution in a DI diesel engine:broadband natural luminosity imaging[C/OL].SAEPaper,2002,2002-01-1631.(2002-05-06)[2018-02-21].http://papers.sae.org/2002-01-1631.
[11]MUELLER C J,PITZ W J,PICKETT L M,et al.Effects of oxygenates on soot processes in DI diesel engines:experiments and numerical simulations[C/OL].SAE Paper,2003,2003-01-1791.(2003-05-19)[2018-02-21].http://papers.sae.org/2003-01-1791.