柴油机低温燃烧燃烧及排放特性的试验研究
摘要
低温燃烧是目前柴油机研究的热点课题,表现出了满足严格排放法规的潜力,燃烧控制的优化是实现高效清洁燃烧的关键。本文较系统研究了EGR率、燃油喷射参数、燃烧相位、含氧燃料对柴油机低温燃烧燃烧特性和排放特性的影响,并对不同EGR率条件下柴油机主要有害排放物的重要组分进行了研究。
本文首先研究了喷油参数、EGR率、燃烧相位和含氧燃料等对低温燃烧燃烧和排放特性的影响。结果表明,提高喷油压力是改善燃烧和降低排放的有效措施之一,尤其对改善高EGR情况下的性能和排放有利;采用EGR可以有效降低NOx排放,soot随EGR率的增大先升高后降低,但过大的EGR率会造成THC和CO排放的急剧升高,经济性恶化;燃烧相位控制的研究表明,控制适当的燃烧相位可以在实现低NO_x排放的条件下保持较好经济性,但早的燃烧相位容易造成压力升高率过高,需要在燃烧控制优化中加以重视。高EGR率条件下采用后喷改善soot、CO和THC的效果不明显,因而需要对低温燃烧过程后喷的作用机理深入研究;通过加入适当比例的含氧燃料对高EGR率(低NOx排放)下的soot排放改善作用显著,这从燃料特性的角度为实现高效、清洁低温燃烧提供了一个参考依据。
在此基础上,研究了不同EGR率下柴油机有害排放物中的NOx组分、THC中CH_4成分以及PM组分的变化规律。研究结果表明,NO_2和N2O在NOx中的比例都随着EGR率的增加先增大后减小,在EGR率为55%左右时达到峰值,远高于低EGR的情况;THC中的CH_4也随EGR率增大而增多(EGR率60%时占15%以上)。在一定的EGR率范围内,提高喷油压力可降低THC排放和其中CH4成分。对颗粒物的测试结果表明,EGR率的变化对颗粒物粒径和粒数分布具有重要影响。
Low temperature combustion is a hot research topic of diesel combustion process, which has the potential to meet stringent emission legislation, and combustion control optimization is the key point to realize high efficiency clean combustion. Firstly, this paper systemically investigated the effects of EGR rate, injection parameters, combustion phase and oxygenated additive on the combustion and emission characteristics of diesel low temperature combustion; then further test was conducted to investigate the effects of EGR rate on the main components of diesel pollutant emissions.
At first, experimental study was conducted to investigate the effects of injection parameters, EGR rate, combustion phase and oxygenated additive on combustion and emissions of diesel low temperature combustion. Test results showed that, it is an effective measure to improve the combustion process and reduce emissions by increasing injection pressure, especially under massive EGR rate conditions; NOx can be effectively reduced by applying EGR, soot firstly increases than decreases with increased EGR rate, however, over high EGR rate results in dramatically increase of THC and CO emissions, as well as deteriorated fuel economy; Much lower NOx emission can be achieved by optimized combustion phase control while still maintaining good fuel economy, however, early combustion phase leads to much higher pressure rise rate, therefore it needs to be carefully calibrated during the combustion control optimization process; There are not too much effects of post injection on soot, CO and THC under high EGR rate conditions, thus further investigation is still needed to be carried out which concerning on the mechanism of post injection under low temperature combustion; Soot reduction can be obtained by blending oxygenated additive into diesel fuel, especially under massive EGR rage conditions. This could provide a reference to realize high efficiency, clean low temperature combustion from the perspective of fuel characteristics. Then test was carried out to study the effects of EGR rate on the variations of NOx component, CH_4 component in THC and PM component in diesel pollutant emissions. Results showed that, the proportions of both NO2 and N2O first increase than decrease with the increase of EGR rate, and reach their peak values when EGR rate is around 55%, both are much higher than low EGR rate conditions; The CH_4 component in THC emission also increases with increased EGR rate (can be more than 15% if EGR rate reaches up to 60%). In certain EGR rate range, both THC emission and CH4 component in THC can be reduced by increasing injection pressure. The PM test result showed that EGR rate poses a very important role on the particle diameter and number.
本文首先研究了喷油参数、EGR率、燃烧相位和含氧燃料等对低温燃烧燃烧和排放特性的影响。结果表明,提高喷油压力是改善燃烧和降低排放的有效措施之一,尤其对改善高EGR情况下的性能和排放有利;采用EGR可以有效降低NOx排放,soot随EGR率的增大先升高后降低,但过大的EGR率会造成THC和CO排放的急剧升高,经济性恶化;燃烧相位控制的研究表明,控制适当的燃烧相位可以在实现低NO_x排放的条件下保持较好经济性,但早的燃烧相位容易造成压力升高率过高,需要在燃烧控制优化中加以重视。高EGR率条件下采用后喷改善soot、CO和THC的效果不明显,因而需要对低温燃烧过程后喷的作用机理深入研究;通过加入适当比例的含氧燃料对高EGR率(低NOx排放)下的soot排放改善作用显著,这从燃料特性的角度为实现高效、清洁低温燃烧提供了一个参考依据。
在此基础上,研究了不同EGR率下柴油机有害排放物中的NOx组分、THC中CH_4成分以及PM组分的变化规律。研究结果表明,NO_2和N2O在NOx中的比例都随着EGR率的增加先增大后减小,在EGR率为55%左右时达到峰值,远高于低EGR的情况;THC中的CH_4也随EGR率增大而增多(EGR率60%时占15%以上)。在一定的EGR率范围内,提高喷油压力可降低THC排放和其中CH4成分。对颗粒物的测试结果表明,EGR率的变化对颗粒物粒径和粒数分布具有重要影响。
Low temperature combustion is a hot research topic of diesel combustion process, which has the potential to meet stringent emission legislation, and combustion control optimization is the key point to realize high efficiency clean combustion. Firstly, this paper systemically investigated the effects of EGR rate, injection parameters, combustion phase and oxygenated additive on the combustion and emission characteristics of diesel low temperature combustion; then further test was conducted to investigate the effects of EGR rate on the main components of diesel pollutant emissions.
At first, experimental study was conducted to investigate the effects of injection parameters, EGR rate, combustion phase and oxygenated additive on combustion and emissions of diesel low temperature combustion. Test results showed that, it is an effective measure to improve the combustion process and reduce emissions by increasing injection pressure, especially under massive EGR rate conditions; NOx can be effectively reduced by applying EGR, soot firstly increases than decreases with increased EGR rate, however, over high EGR rate results in dramatically increase of THC and CO emissions, as well as deteriorated fuel economy; Much lower NOx emission can be achieved by optimized combustion phase control while still maintaining good fuel economy, however, early combustion phase leads to much higher pressure rise rate, therefore it needs to be carefully calibrated during the combustion control optimization process; There are not too much effects of post injection on soot, CO and THC under high EGR rate conditions, thus further investigation is still needed to be carried out which concerning on the mechanism of post injection under low temperature combustion; Soot reduction can be obtained by blending oxygenated additive into diesel fuel, especially under massive EGR rage conditions. This could provide a reference to realize high efficiency, clean low temperature combustion from the perspective of fuel characteristics. Then test was carried out to study the effects of EGR rate on the variations of NOx component, CH_4 component in THC and PM component in diesel pollutant emissions. Results showed that, the proportions of both NO2 and N2O first increase than decrease with the increase of EGR rate, and reach their peak values when EGR rate is around 55%, both are much higher than low EGR rate conditions; The CH_4 component in THC emission also increases with increased EGR rate (can be more than 15% if EGR rate reaches up to 60%). In certain EGR rate range, both THC emission and CH4 component in THC can be reduced by increasing injection pressure. The PM test result showed that EGR rate poses a very important role on the particle diameter and number.
引文
[1] http://www.stats.gov.cn/tjgb/ndtjgb/qgndtjgb/t20100225_402622945.htm
[2]王建昕,傅立新,黎维彬.汽车排气污染治理及催化转化器[J],北京:化学工业出版社,2000,1—2l.
[3]黄镇平,沈捷.降低直喷式柴油机NOx排放的实验研究[J],柴油机,1999(3), 26—31.
[4]延吉生.我国能源资源状况利用现状与发展战略[J].金属矿山,2003(8).
[5] Heywood J B.Internal combustion engine fundamentals,New York: McGraw-Hill Book Company,1998.
[6]周龙保,刘巽俊,高宗英.内燃机学[M],机械工业出版社,2005.1
[7]陈文淼,王建昕,帅石金等.硫对柴油机排放性能影响研究.中国内燃机学会燃烧节能净化分会2007年学术年会论文汇编[c],20070810.
[8]李约上,内燃机排放与净化[M].大连:大连理工大学出版社,1990.
[9] Ciajolo, A., d’Anna, A., Barbella, R., Tregrossi, A and Violi, A.,“The Effect of Temperature on SootInception in Premixed Ethylene Flames”, Twenty-Sixth Symposium (International) on Combustion, The Combustion Institute[J], 1996.
[10]王忠俊等,进气道喷水降低NOx排放研究[J],武汉理工大学学报,2004.2(4)
[11]何学良,詹永厚,李毓松,内燃机燃料[M],北京:中国石化出版社,1999.
[12] Helmantel A.Reduction of NO Emissions From a Light DutyDI Diesel Engine in Medium Load Conditions with High EGRRates[J],SAE paper 2008-01-0643
[13] N.Ladommatos,S.M Abdelhalim,H.zhao The Dilution , Chemical,and Thermal Effects ofExhaust Gas Recirculation on Diesel EngineEmissions-Part 1:Effect of Reducing Inlet ChargeOxygen[J].SAE Paper 961165.
[14] S. L. Plee, T. Ahmad, and J. P. Myers, "FlameTemperature Correlation for the Effects of ExhaustGas Recirculation on Diesel Particulate and NOx Emissions"[J], SAE Paper 811195, 1981.
[15]王忠,排气再循环对柴油机工作过程参数,性能和排放的影响[J]内燃机学报,2002年,第20卷第5期.
[16]于超,肖建华,王建昕等.EGR率对燃用生物柴油的重型柴油机排放特性影响.汽车工程,2008,30(10):871—874.
[17]宁智,张广龙.柴油机微粒排放的机外后处理技术及其发展趋势[J]车用发动机,1995(4):1—4.
[18] Mingfa Yao and Zhaolei Zheng,A Numerical Investigation on Effects of Charge Stratification on HCCI Combustion.SAE Technical Paper[J],2007-01-4075
[19] L. M. Pickett and D. L. Siebers,“Non-sooting, low flame temperature mixing-controlled DI dieselcombustion”[J], SAE Paper 2004-01-1399, 2004.
[20]王大兴等.均质上K燃式(HCCI)燃烧的研究[J].内燃机工程,2002,23(40):77—81.
[21] Walter, B., and Gatellier, B.,“Development of theHigh Power NADITM Concept Using Dual ModeDiesel Combustion to Achieve Zero NOx and Particulate Emissions”[J], SAE paper 2002-01-1744,2002.
[22] Ranzi,E,Sogaro,A,Gaffuri,P A wide range modeling study of methane oxidation Combustion Science and Technology [J],(1994)279-325.
[23]苏万华,赵华,王建昕等著.均质压燃低温燃烧发动机理论与技术[M],北京:科学出版社,2010.
[24]Heywood, J.B.,“Internal Combustion Enginefundamentals”[M], 1988, Singapore, McGraw-Hill inc.
[25] S.Yoshikawa,Rytunosuke Furusawav.Optimizing Spray Behavior to Improve EnginePerformance and to Reduce Exhaust Emissions in a Small DI Diesel Engine[J].SAE 890463.98(3):861～867.
[26]杨帅,应启戛,姚喜贵等,供油提前角与EGR技术对柴油机排放影响的试验研究[J]汽车技术,2005年,第8期.
[27] Zheng, J., Miller, D., Cernansky, N., Liu, D., Zhao,X., and Zhang, M.,”Some Observations on theEffects of EGR, Oxygen Concentration, and EngineSpeed on the Homogenous Charge Combustion ofn-heptane”[J], SAE paper 2004-01-1905, 2004
[28]王平,司建明,王彦伟等.关于废气再循环(EGR)技术[J]内燃机与动力装置,2006年,第4期.
[29]朱昌吉,刘忠长,许允等.废气再循环对车用柴油机性能与排放的影响[J]汽车工程,2004年,第26卷第2期
[30]Ogawa H., Shimizu H., Kido S. and Miyamoto N.,“Characteristics of Diesel Combustion in Low Oxygen Mixtures with Ultra-High EGR at High load”, [J]SAE Paper 2006-01-1147, 2006.
[31]Dickey D W,Ryan III T W.NOx Control in Heavy-Duty Diesel Engines-Whatis the Limit?,SAE 980174,1998.
[32]Kitamura T,Ito‘T,Senda J and Fujimoto H,Mechanism of smokeless diesel combustion with oxygenated fuels based on the dependence of the equivalence ratio and temperature on soot particle formation,International Journal of Engine Research[J],2002,V01.3(4):223-247.
[33]小川英之,首藤登志夫,吉田拓弥.采用后喷射改善柴油机的燃烧过程[J],国外内燃机,2009(01).
[34]金华玉,张楠,刘忠长等,基于柴油机后喷的分区燃烧的数值模拟[C],中国内燃机学会燃烧、节能、净化分会2008年学术年会论文集.
[35]曾庆平,袁晓东,郭和军,何建宏,柴油机清洁含氧燃料及其发展[J],内燃机与动力装置,2007(2).
[36]刘炜,王嘉松,乔信起,王真,肖进,黄震.直喷柴油机含氧燃料微粒排放的试验研究[C],中国内燃机学会燃烧净化节能分会2007年学术年会论文集,2007.
[2]王建昕,傅立新,黎维彬.汽车排气污染治理及催化转化器[J],北京:化学工业出版社,2000,1—2l.
[3]黄镇平,沈捷.降低直喷式柴油机NOx排放的实验研究[J],柴油机,1999(3), 26—31.
[4]延吉生.我国能源资源状况利用现状与发展战略[J].金属矿山,2003(8).
[5] Heywood J B.Internal combustion engine fundamentals,New York: McGraw-Hill Book Company,1998.
[6]周龙保,刘巽俊,高宗英.内燃机学[M],机械工业出版社,2005.1
[7]陈文淼,王建昕,帅石金等.硫对柴油机排放性能影响研究.中国内燃机学会燃烧节能净化分会2007年学术年会论文汇编[c],20070810.
[8]李约上,内燃机排放与净化[M].大连:大连理工大学出版社,1990.
[9] Ciajolo, A., d’Anna, A., Barbella, R., Tregrossi, A and Violi, A.,“The Effect of Temperature on SootInception in Premixed Ethylene Flames”, Twenty-Sixth Symposium (International) on Combustion, The Combustion Institute[J], 1996.
[10]王忠俊等,进气道喷水降低NOx排放研究[J],武汉理工大学学报,2004.2(4)
[11]何学良,詹永厚,李毓松,内燃机燃料[M],北京:中国石化出版社,1999.
[12] Helmantel A.Reduction of NO Emissions From a Light DutyDI Diesel Engine in Medium Load Conditions with High EGRRates[J],SAE paper 2008-01-0643
[13] N.Ladommatos,S.M Abdelhalim,H.zhao The Dilution , Chemical,and Thermal Effects ofExhaust Gas Recirculation on Diesel EngineEmissions-Part 1:Effect of Reducing Inlet ChargeOxygen[J].SAE Paper 961165.
[14] S. L. Plee, T. Ahmad, and J. P. Myers, "FlameTemperature Correlation for the Effects of ExhaustGas Recirculation on Diesel Particulate and NOx Emissions"[J], SAE Paper 811195, 1981.
[15]王忠,排气再循环对柴油机工作过程参数,性能和排放的影响[J]内燃机学报,2002年,第20卷第5期.
[16]于超,肖建华,王建昕等.EGR率对燃用生物柴油的重型柴油机排放特性影响.汽车工程,2008,30(10):871—874.
[17]宁智,张广龙.柴油机微粒排放的机外后处理技术及其发展趋势[J]车用发动机,1995(4):1—4.
[18] Mingfa Yao and Zhaolei Zheng,A Numerical Investigation on Effects of Charge Stratification on HCCI Combustion.SAE Technical Paper[J],2007-01-4075
[19] L. M. Pickett and D. L. Siebers,“Non-sooting, low flame temperature mixing-controlled DI dieselcombustion”[J], SAE Paper 2004-01-1399, 2004.
[20]王大兴等.均质上K燃式(HCCI)燃烧的研究[J].内燃机工程,2002,23(40):77—81.
[21] Walter, B., and Gatellier, B.,“Development of theHigh Power NADITM Concept Using Dual ModeDiesel Combustion to Achieve Zero NOx and Particulate Emissions”[J], SAE paper 2002-01-1744,2002.
[22] Ranzi,E,Sogaro,A,Gaffuri,P A wide range modeling study of methane oxidation Combustion Science and Technology [J],(1994)279-325.
[23]苏万华,赵华,王建昕等著.均质压燃低温燃烧发动机理论与技术[M],北京:科学出版社,2010.
[24]Heywood, J.B.,“Internal Combustion Enginefundamentals”[M], 1988, Singapore, McGraw-Hill inc.
[25] S.Yoshikawa,Rytunosuke Furusawav.Optimizing Spray Behavior to Improve EnginePerformance and to Reduce Exhaust Emissions in a Small DI Diesel Engine[J].SAE 890463.98(3):861～867.
[26]杨帅,应启戛,姚喜贵等,供油提前角与EGR技术对柴油机排放影响的试验研究[J]汽车技术,2005年,第8期.
[27] Zheng, J., Miller, D., Cernansky, N., Liu, D., Zhao,X., and Zhang, M.,”Some Observations on theEffects of EGR, Oxygen Concentration, and EngineSpeed on the Homogenous Charge Combustion ofn-heptane”[J], SAE paper 2004-01-1905, 2004
[28]王平,司建明,王彦伟等.关于废气再循环(EGR)技术[J]内燃机与动力装置,2006年,第4期.
[29]朱昌吉,刘忠长,许允等.废气再循环对车用柴油机性能与排放的影响[J]汽车工程,2004年,第26卷第2期
[30]Ogawa H., Shimizu H., Kido S. and Miyamoto N.,“Characteristics of Diesel Combustion in Low Oxygen Mixtures with Ultra-High EGR at High load”, [J]SAE Paper 2006-01-1147, 2006.
[31]Dickey D W,Ryan III T W.NOx Control in Heavy-Duty Diesel Engines-Whatis the Limit?,SAE 980174,1998.
[32]Kitamura T,Ito‘T,Senda J and Fujimoto H,Mechanism of smokeless diesel combustion with oxygenated fuels based on the dependence of the equivalence ratio and temperature on soot particle formation,International Journal of Engine Research[J],2002,V01.3(4):223-247.
[33]小川英之,首藤登志夫,吉田拓弥.采用后喷射改善柴油机的燃烧过程[J],国外内燃机,2009(01).
[34]金华玉,张楠,刘忠长等,基于柴油机后喷的分区燃烧的数值模拟[C],中国内燃机学会燃烧、节能、净化分会2008年学术年会论文集.
[35]曾庆平,袁晓东,郭和军,何建宏,柴油机清洁含氧燃料及其发展[J],内燃机与动力装置,2007(2).
[36]刘炜,王嘉松,乔信起,王真,肖进,黄震.直喷柴油机含氧燃料微粒排放的试验研究[C],中国内燃机学会燃烧净化节能分会2007年学术年会论文集,2007.