冯浩，林思聪，陈泓，李钰怀，吴翔，杜家坤.稀燃及废气再循环提高增压汽油机热效率的对比研究[J].内燃机工程,2020,41(1):36-41.
稀燃及废气再循环提高增压汽油机热效率的对比研究
A Comparison of Using Lean Burn and Exhaust Gas Recirculation to Improve Thermal Efficiency of a Turbocharged Gasoline Engine
DOI：10.13949/j.cnki.nrjgc.2020.01.005
关键词:热效率  稀燃  废气再循环  能量平衡
Key Words:thermal efficiency  lean burn  exhaust gas recirculation  energy balance
基金项目:国家重点研发计划项目（2017YFB0103300）
作者单位
冯浩，林思聪，陈泓，李钰怀，吴翔，杜家坤 广州汽车集团股份有限公司汽车工程研究院，广州 511434 
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摘要:在一台直列4缸增压直喷汽油机上针对万有特性最低油耗工况点，进行了稀薄燃烧与废气再循环（exhaust gas recirculation, EGR）提高发动机热效率的对比试验研究。试验结果表明：稀薄燃烧及EGR均能有效降低发动机燃油消耗率，稀释率分别为33%和19%时，采用稀燃和EGR时的最高有效热效率绝对值分别增加2.8%和1.7%，其中稀燃的有效热效率达到了39.9%，稀燃实现更高热效率主要归因于较低的传热损失和未燃损失。从燃烧角度来看，稀燃及EGR稀释都延长了燃烧滞燃期及持续期，但同样稀释率下稀燃的滞燃期更短，稀燃更高的稀释极限实现了更低的传热损失；但EGR抑制爆震,提前燃烧相位，使采用EGR时的排气能量损失低于稀燃。从排放角度来看，稀燃及EGR在高稀释率下均显著降低NOx 排放，而受益于高氧气浓度，相同稀释率下稀燃的HC及CO排放均低于采用EGR时，从而使稀燃的未燃损失更低。
Abstract:An inline 4-cylinder turbocharged direct-injection gasoline engine was used to compare the thermal efficiency of the engine with lean burn and exhaust gas recirculation(EGR), and the comparative test was carried out at the lowest fuel consumption point of the universal characteristic curves. The experimental results show that both lean burn and EGR can effectively reduce engine fuel consumption. When the dilution rates of lean burn and EGR are 33% and 19%, their maximum brake thermal efficiencies can increase by 2.8% and 1.7%, respectively, and the brake thermal efficiency with lean burn is even up to 39.9%. The main reason for higher thermal efficiency of using lean burn is the reduction of heat transfer loss and unburned fuel loss. From the view of combustion, the dilution effect of lean burn and EGR extends the ignition delay and combustion duration. At the same dilution rate, the ignition delay with lean burn is shorter than with EGR, and the higher dilution rate of lean burn results in less heat transfer loss. However, use of EGR helps to suppress the occurrences of knock and to advance combustion phase, which makes the exhaust energy loss lower than with lean burn. As to exhaust emissions, both lean burn and EGR can obviously reduce NOx emission at high dilution rate. At the same dilution rate, HC and CO emissions with lean burn are lower than with EGR because of rich oxygen concentration, which results in a much lower unburned loss of lean burn.
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