进气加湿对船用柴油机燃烧和排放的影响  

Effects of Intake Air Humidification on Combustion and Emissions in a Marine Diesel Engine

作　　者：张志刚 赵昌普[1] 王耀辉[1] 孙雅坤 郑尊清[1] 

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《燃烧科学与技术》2017年第5期436-442,共7页Journal of Combustion Science and Technology

基　　金：国家高技术研究发展计划(863计划)资助项目(2012AA111705);国家自然科学基金资助项目(50676067)

摘　　要：运用CFD数值模拟软件AVL Fire建立了船用柴油机燃烧过程模型,研究不同相对湿度的进气成分对船用柴油机燃烧和排放特性的影响,并着重研究对NO_x和碳烟排放的影响规律和作用机理.结果表明:随着进气加湿率的增加,缸内压力和燃烧温度均有降低;当加湿率达到100%,时,峰值压力相比进气为干空气时下降0.67,MPa,最高燃烧温度下降220,K;滞燃期和燃烧持续期延长,预混燃烧比例增多;燃烧重心CA50向后偏移,燃烧定容度和热效率下降.NO_x排放不断减少,燃烧火焰温度的降低和水蒸气对富氧区的稀释是NO_x排放下降的主要原因;碳烟排放随着加湿率的增加不断恶化,进气加湿虽然可以促进油气混合、抑制碳烟生成,OH基团加速碳烟前驱物的氧化,但加湿后氧气质量分数的减少和燃烧温度的降低导致碳烟后期氧化能力严重减弱.The combustion and emission characteristics of marine diesel engine with varied relative humidity of intake air were investigated by using multi-dimensional CFD model.The combustion model was established by AVL Fire code.The influence rules and function mechanisms of intake air humidification on NOx and soot were especially investigated.Results show that,as the intake air humidification rate increases,both of combustion pressure and temperature decrease.When the humidification rates reach one hundred percent,compared with the condition of dry air,the peak pressure decreases by 0.67,MPa,the peak flame temperature is reduced by 220,K,the ignition delay and combustion duration become longer,and the proportion of premixed combustion increases.Simultaneously,the center of heat release curve postpones,and the combustion thermal efficiency declines.Due to the decrease of flame temperature and dilution of oxygen-rich area,NOx emissions are kept decreasing.Intake air humidification suppresses soot formation by improving the mixture of fuel-air and accelerates the soot oxidation with OH groups,while the reduction of oxygen mass fraction and the decrease of flame temperature weaken the soot oxidation ability.As a result,the soot emissions continuously deteriorate with increasing humidification rates.

关 键 词：船用柴油机 进气加湿 数值模拟 燃烧 排放 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]