为提高柴油机性能、降低排放和油耗,分析高、低压废气再循环(exhaust gas recirculation,EGR)系统的优缺点,对装配高/低压EGR系统的某2.0 L柴油机进行台架及整车试验,研究高/低压EGR系统对柴油机性能的影响。结果表明:同时匹配高/低压EG...为提高柴油机性能、降低排放和油耗,分析高、低压废气再循环(exhaust gas recirculation,EGR)系统的优缺点,对装配高/低压EGR系统的某2.0 L柴油机进行台架及整车试验,研究高/低压EGR系统对柴油机性能的影响。结果表明:同时匹配高/低压EGR系统并合理分配其应用可有效降低柴油机油耗及排放,相比仅匹配高压EGR系统的柴油机,高/低压EGR联合应用的柴油机油耗降低3.1%,NO_(x)排放降低3.0%,颗粒物排放降低22.2%;低压EGR可减少流经进气歧管的废气量,改善进气歧管结焦问题;在低温环境下应用EGR系统时进气系统存在结冰风险,需基于环境温度修正关闭高/低压EGR系统,避免出现因结冰导致的发动机损坏。展开更多
针对一台共轨重型柴油机,从提升废气再循环(exhaust gas recycling,EGR)循环能力的角度研究了基于二级增压系统的高压EGR(HP-EGR)、低压EGR(LP-EGR)及基于LP-EGR的高、低级涡轮间废气能量分配对柴油机燃烧过程、性能和排放的影响规律。...针对一台共轨重型柴油机,从提升废气再循环(exhaust gas recycling,EGR)循环能力的角度研究了基于二级增压系统的高压EGR(HP-EGR)、低压EGR(LP-EGR)及基于LP-EGR的高、低级涡轮间废气能量分配对柴油机燃烧过程、性能和排放的影响规律。研究结果表明:与HP-EGR相比,LP-EGR受转速和负荷的影响减小,能够显著提升EGR的循环能力,使柴油机在更宽广的EGR率区域内运行,并将氮氧化物(NOx)降至更低水平;采用HPEGR时,涡前压力随EGR率增加呈线性下降,但LP-EGR的涡前压力与进气压力变化较小,同时在低速中、高负荷时获得较高的空燃比,并显著改善NOx排放与有效燃油消耗率(brake specific fuel consumption,BSFC)和NOx与碳烟排放的平衡关系;在中、高转速高负荷时,HPEGR进/排气压差随EGR率增加逐渐下降并更加低于LP-EGR,NOx-BSFC的平衡关系显著改善;而LP-EGR通过适当增大废气旁通阀开度能有效降低BSFC,同时对NOx-碳烟的平衡关系影响较小,但低转速高负荷时应采用关闭旁通阀的控制策略。展开更多
An experimental study was performed to compare the effects of high-and low-pressure exhaust gas recirculation loops(HP and LP EGR loops)on thermal efficiency and emissions of a diesel engine.Tests were conducted on a ...An experimental study was performed to compare the effects of high-and low-pressure exhaust gas recirculation loops(HP and LP EGR loops)on thermal efficiency and emissions of a diesel engine.Tests were conducted on a 12-L six-cylinder turbocharged diesel engine under various operating conditions.We found that at a low speed of 1100 r/min,1 MPa BMEP,the LP EGR loop could achieve higher brake thermal efficiency and lower emissions than the HP EGR.This is because the lower enthalpy available at the turbine inlet of the HP EGR loop increased the fuel/oxygen equivalence ratio.For the HP EGR,the gross indicated thermal efficiency was reduced by 1%,but pumping losses were only reduced by 0.5%,compared to the LP EGR loop.At a higher speed of 1600 r/min,1 MPa BMEP,the HP EGR loop attained a higher brake thermal efficiency and lower emissions because of the relatively sufficient flow through the turbocharger.For the HP EGR loop,the gross indicated thermal efficiency was only reduced by 0.5%and pumping losses were reduced by 1.5%,compared to the LP EGR loop.Lower fuel consumption and a longer ignition delay made the distribution of fuel/oxygen equivalence ratio more homogeneous,leading to lower emissions.Our data also showed that at the high speed of 1600 r/min,0.55 MPa BMEP,the brake thermal efficiency of the HP EGR loop first increased,then decreased as the EGR rate increased.Therefore,under all conditions,a reasonable match of both EGR loops could achieve a good balance between fuel consumption and emissions of NOx and soot.展开更多
文摘为提高柴油机性能、降低排放和油耗,分析高、低压废气再循环(exhaust gas recirculation,EGR)系统的优缺点,对装配高/低压EGR系统的某2.0 L柴油机进行台架及整车试验,研究高/低压EGR系统对柴油机性能的影响。结果表明:同时匹配高/低压EGR系统并合理分配其应用可有效降低柴油机油耗及排放,相比仅匹配高压EGR系统的柴油机,高/低压EGR联合应用的柴油机油耗降低3.1%,NO_(x)排放降低3.0%,颗粒物排放降低22.2%;低压EGR可减少流经进气歧管的废气量,改善进气歧管结焦问题;在低温环境下应用EGR系统时进气系统存在结冰风险,需基于环境温度修正关闭高/低压EGR系统,避免出现因结冰导致的发动机损坏。
文摘针对一台共轨重型柴油机,从提升废气再循环(exhaust gas recycling,EGR)循环能力的角度研究了基于二级增压系统的高压EGR(HP-EGR)、低压EGR(LP-EGR)及基于LP-EGR的高、低级涡轮间废气能量分配对柴油机燃烧过程、性能和排放的影响规律。研究结果表明:与HP-EGR相比,LP-EGR受转速和负荷的影响减小,能够显著提升EGR的循环能力,使柴油机在更宽广的EGR率区域内运行,并将氮氧化物(NOx)降至更低水平;采用HPEGR时,涡前压力随EGR率增加呈线性下降,但LP-EGR的涡前压力与进气压力变化较小,同时在低速中、高负荷时获得较高的空燃比,并显著改善NOx排放与有效燃油消耗率(brake specific fuel consumption,BSFC)和NOx与碳烟排放的平衡关系;在中、高转速高负荷时,HPEGR进/排气压差随EGR率增加逐渐下降并更加低于LP-EGR,NOx-BSFC的平衡关系显著改善;而LP-EGR通过适当增大废气旁通阀开度能有效降低BSFC,同时对NOx-碳烟的平衡关系影响较小,但低转速高负荷时应采用关闭旁通阀的控制策略。
基金supported by the National High Technology Research and Development Program of China("863" Program)(Grant No.2012AA111714)
文摘An experimental study was performed to compare the effects of high-and low-pressure exhaust gas recirculation loops(HP and LP EGR loops)on thermal efficiency and emissions of a diesel engine.Tests were conducted on a 12-L six-cylinder turbocharged diesel engine under various operating conditions.We found that at a low speed of 1100 r/min,1 MPa BMEP,the LP EGR loop could achieve higher brake thermal efficiency and lower emissions than the HP EGR.This is because the lower enthalpy available at the turbine inlet of the HP EGR loop increased the fuel/oxygen equivalence ratio.For the HP EGR,the gross indicated thermal efficiency was reduced by 1%,but pumping losses were only reduced by 0.5%,compared to the LP EGR loop.At a higher speed of 1600 r/min,1 MPa BMEP,the HP EGR loop attained a higher brake thermal efficiency and lower emissions because of the relatively sufficient flow through the turbocharger.For the HP EGR loop,the gross indicated thermal efficiency was only reduced by 0.5%and pumping losses were reduced by 1.5%,compared to the LP EGR loop.Lower fuel consumption and a longer ignition delay made the distribution of fuel/oxygen equivalence ratio more homogeneous,leading to lower emissions.Our data also showed that at the high speed of 1600 r/min,0.55 MPa BMEP,the brake thermal efficiency of the HP EGR loop first increased,then decreased as the EGR rate increased.Therefore,under all conditions,a reasonable match of both EGR loops could achieve a good balance between fuel consumption and emissions of NOx and soot.
