实现国V排放的重型柴油机燃烧系统优化研究  

The optimization study of diesel engine combustion system to meet the China Stage V emissions standard

作　　者：官维[1] 莫春兰[1] 赵刚东 黄冠衍 郑尊清[2] 

机构地区：[1]广西大学机械工程学院,广西南宁530004 [2]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《广西大学学报（自然科学版）》2015年第5期1135-1145,共11页Journal of Guangxi University（Natural Science Edition）

基　　金：国家重点基础研究发展计划(973计划)资助项目(2013CB228402);广西制造系统与先进制造技术重点实验室项目(13-051-09S06)

摘　　要：为了满足今后更为苛刻的国V排放法规,本文在一台无后处理满足国Ⅳ排放的重型柴油机上进行了燃烧系统优化试验,结果表明在大多数工况点,低压级压气机有效流通面积减小的两级增压方案2TC2与柴油机的联合运行点向着压比和相似流量增大的方向移动,能明显提高进气压力和空燃比,有效改善了氮氧化物(NOx)与燃油消耗率(BSFC)以及NOx与碳烟(Soot)的权衡(trade-off)关系。通过优化设计燃烧室结构参数(缩口直径、凹坑深度),缩口下移1 mm的燃烧室SF4能增强缸内气流运动,促进了燃油与空气的混合,实现了同时改善NOx-Soot和NOx-BSFC的trade-off关系并维持缸内最大燃烧压力至合理水平。随着主喷时刻的推迟,燃烧相位推迟,Soot比排放降低,但燃油经济性变差,并且主喷时刻过多推迟会使Soot比排放升高;在高转速工况,提高喷油压力能同时改善油耗和排放,而在低转速大负荷,呈现出与高转速工况相反的变化趋势,Soot和BSFC随着喷油压力提高同时上升;采用适当的主后喷间隔能达到改善排放的效果。试验结果表明,NOx加权排放为1.311 g/(k W·h),Soot加权排放为0.011 g/(k W·h),均满足国V排放标准,且加权油耗为211.6 g/(k W·h)。所优化的燃烧系统具有在降低对后处理系统要求的情况下满足国Ⅴ排放标准的能力。Optimization of a China Stage V diesel engine combustion system were carried out on a heavy-duty diesel engine, which has met the China Ⅳ emission standards under the condition of without the after-treatment device in order to meet the much more stringent emission regulations. Test results showed that, in most operation conditions, the joint operating point between diesel en- gine and the supercharger （2TC2） where the flow area of low pressure compressor is smaller, moving in the direction of high pressure ratio and equivalent flow, can obviously increase intake pressure and air-fuel ratio, and effectively improve the trade-off relationships of NOx-Soot and NOx-BSFC （Brake Specific Fuel Combustion）. Combustion chamber （SF4） where reentrant down 1 mm based on the original combustion chamber （ SF1 ）, can enhance airflow motion in cylinder, and increase the mixing uniformity and the mixing rate of fuel and gas. BSFC and Soot can be decreased and keep the maximum in-cylinder pressure in the reasonable range at the same time. With retarded injection timing, the combustion phase delay, Soot emissions decrease, and BSFC increase. The Soot emis- sions rise, however, when the injection timing delayed too much. Increasing the pressure of injec- tion can reduce Soot and BSFC simultaneously at the high speed conditions. However, Soot and BSFC is increase with the increasing of the injection pressure at low speed and high load conditions. By using proper interval between main and post, injection can improve emissions. The test results showed that NOx and Soot emission are 1. 799 g/（kW · h）and 0. 015 g/（kW · h） respectively, which both under the limit value of the China Stage Ⅴ emission regulations. Meanwhile, BSFC can be reach 211.6 g/（kW · h）. The optimized combustion chamber has the ability to meet the China Stage Ⅴ emissions standard while reducing the requirement of exhaust after-treatment devices.

关 键 词：柴油机 废气再循环(EGR) 两级增压 燃烧室 喷油策略 排放 

分 类 号：TK427[动力工程及工程热物理—动力机械及工程]