不同喷射策略低温预混合燃烧模式排放试验
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摘要
基于一台4缸增压柴油机,研究了不同喷射参数分别在单次喷射预混合燃烧(PPC)和预喷模式PPC下对发动机排放生成的影响,其中重点关注了颗粒物的排放特性.结果表明:单次喷射形成早期喷射PPC后可以显著降低颗粒物的数量、质量以及几何平均直径(GMD),但是当喷射正时过于提前,颗粒物数量又会上升到与常规模式相当.总体上,预喷可以显著地降低碳烟排放,但是当预喷正时提前到某一特定值时,如果继续提前预喷角,颗粒物质量、数量以及GMD将基本不变.提高预喷燃油比例,形成更高比例的预混合燃烧,颗粒物数量和质量可以同时下降,颗粒物GMD先增加后降低.单次喷射早喷PPC模式下NOx排放较高,相比之下采用预喷的方式却可以在降低碳烟排放的同时很好地控制NOx排放.早喷PPC模式下由于压缩阶段负功增加导致燃油消耗率急剧升高,而预喷模式下燃油消耗率随预喷正时的提前以及预喷燃油比的增加略有升高.
A 4-cylinder turbocharged diesel engine was modified to run partially-premixed low temperature combustion mode.The influence of injection strategy on the emission characteristics,especially particles,was studied on the engine under the conditions of single-injection and pilot-injection respectively.The results show that the earlyinjection PPC formed by the single injection can reduce the quantity, quality and GMD of particles obviously.However,when the injection timing is too early,the quantity of particles will rise as those of normal mode.On the other hand,the pilot injection can reduce soot emission dramatically.However,if the timing of the pilot injection is advanced to a certain value,the quantity,quality and GMD of particles are almost unchanged. Furthermore,increasing the proportion of pilot injection fuel can form a higher proportion of premixed combustion.As a result,the quantity and quality of particles decrease,while GMD increases first and then decreases.The NOx emission is higher in the early-injection PPC mode under the single injection strategy.By contrast,the split strategy can control PM and NOx emissions simultaneously.In the early-injection PPC mode the fuel consumption rate increases sharply,and the fuel consumption rate increases slightly with the advance of pilot injection timing and the pilot injection fuel ratio.
A 4-cylinder turbocharged diesel engine was modified to run partially-premixed low temperature combustion mode.The influence of injection strategy on the emission characteristics,especially particles,was studied on the engine under the conditions of single-injection and pilot-injection respectively.The results show that the earlyinjection PPC formed by the single injection can reduce the quantity, quality and GMD of particles obviously.However,when the injection timing is too early,the quantity of particles will rise as those of normal mode.On the other hand,the pilot injection can reduce soot emission dramatically.However,if the timing of the pilot injection is advanced to a certain value,the quantity,quality and GMD of particles are almost unchanged. Furthermore,increasing the proportion of pilot injection fuel can form a higher proportion of premixed combustion.As a result,the quantity and quality of particles decrease,while GMD increases first and then decreases.The NOx emission is higher in the early-injection PPC mode under the single injection strategy.By contrast,the split strategy can control PM and NOx emissions simultaneously.In the early-injection PPC mode the fuel consumption rate increases sharply,and the fuel consumption rate increases slightly with the advance of pilot injection timing and the pilot injection fuel ratio.
引文
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[2]Je?ek I,Katra?nik T,Westerdahl D,et al.Black carbon,particle number concentration and nitrogen oxide emission factors of random in-use vehicles measured with the on-road chasing method[J].Atmos Chem Phys,2015,15(19):11011-11026.
[3]Kittelson D B,Arnold M,Watts W F.Review of diesel particulate matter sampling methods:Final report[M].Minnesota:University of Minnesota,1999:1-10.
[4]Krestinin A V.Detailed modeling of soot formation in hydrocarbon pyrolysis[J].Combustion and Flame,2000,121(3):513-524.
[5]Liu B,Cheng X,Qiu L,et al.Numerical simulation and experimental research on PPC combustion and emissions characteristics of diesel engine[C]//SAE 2015World Congress&Exhibition Conference,Detroit,MI,USA,2015,2015-01-0401.
[6]Yin L,Ingesson G,Shamun S,et al.Sensitivity analysis of partially premixed combustion(PPC)for control purposes[C]//SAE Paper.Detroit,MI,USA,2015,2015-01-0884.
[7]Hanson R,Splitter D,Reitz R.Operating a heavy-duty direct-injection compression-ignition engine with gasoline for low emissions[C]//SAE Paper.Detroit,MI,USA,2009,2009-01-1442.
[8]刘贝,成晓北,董世军,等.柴油机部分预混合燃烧与排放特性的模拟与试验[J].内燃机学报,2014,32(6):496-504.
[9]Johansson B.Partially premixed combustion,PPC,for high fuel efficiency engine operation[C]//SAE Powertrain and Fluids Conference,San Antonio,2009.
[10]Borgqvist P,Tunestal P,Johansson B.Gasoline partially premixed combustion in a light duty engine at low load and idle operating conditions[C]//SAE Paper.Detroit,MI,USA,2012,2012-01-0687.
[11]Hanson R M,Kokjohn S L,Splitter D A,et al.An experimental investigation of fuel reactivity controlled PCCI combustion in a heavy-duty engine[J].SAE International Journal of Engines,2010,3(1):700-716.
[12]刘贝,成晓北,董世军,等.预喷对重载柴油机燃烧与排放影响的试验[J].内燃机学报,2015,33(3):201-209.