摘要
为探索轻型车用柴油机在中小负荷率工况下实现超低排放的预混合低温燃烧策略,以某四缸轻型车用柴油机为样机,在中小负荷率工况下,进行了喷射正时、废气再循环率(exhaust gas recirculation,EGR)、进气温度、喷射压力、预喷射等不同控制参数对柴油机预混合低温燃烧影响的试验研究。证明适时早喷射可延长预混合期实现预混合燃烧,改善柴油机碳烟排放;采用高比例EGR技术降低进气氧浓度能有效控制预混合燃烧温度,可有效降低NOx排放,同时可推迟由早喷射造成的过早的燃烧相位;在适时早喷射结合高比例EGR的基础上,协同优化喷射压力、进气温度与预喷射参数改善NOx和碳烟排放Trade-off关系,以实现超低排放的预混合低温燃烧;通过预混合低温燃烧路径优化后,10%、25%和50%负荷率工况NOx排放与原机相比分别降低97.8%、80.7%和62.1%,碳烟排放分别降低76%、93.9%和47.1%。3个负荷率工况下优化后的有效燃油消耗率比优化前略有上升。研究结果为轻型柴油机预混合低温燃烧过程的优化及污染物排放控制技术提供了理论基础。
The combustion process of diesel engines has a significant effect on the power, economy, and emission performance of a vehicle. As internal combustion engines tend to be highly effective, energy-saving, and environmentally friendly, all the scholars of the world in this area concentrate on creatively developing the combustion theories and techniques for the oncoming generation of engines in order to break through the emission limits of conventional diesel engines. Aiming at the difficulties of forming the homogeneous charge and organizing the combustion progress for the compact structure of light-duty vehicle diesel engines, the research in this paper was based upon advanced injection combined with high proportion cooling EGR to achieve the low-temperature premixed combustion. Taking advantage of a pressure information acquisition and performance bench test, the effects of fuel injection strategies and intake system parameters on the low-temperature premixed combustion process and pollutants emissions were studied systematically, which explores the effective ways for forming the homogeneous charge and controlling the low-temperature combustion progress so that the theoretical principle of low-temperature premixed combustion techniques for engineering application was built. Based on an in-cylinder pressure information acquisition and performance bench test, the effects of combustion control parameters such as injection timing, injection pressure, intake oxygen concentration, intake temperature, and pilot-injection on a low-temperature premixed combustion process and emission performance were studied. This revealed that taking the advanced injection strategy can prolong the ignition delay period, and improving the fuel-air mixture is the key to reducing the soot emission. Diminishing the intake oxygen concentration can control the temperature of premixed combustion effectively, restrain the production of the NOx emission, and put the ignition phase of a premixed combustion which is too early off, which is beneficial to improving the combustion efficiency and enhancing the fuel economy. Increasing the fuel injection pressure makes the NOx and soot emissions reduced in the low-temperature combustion mode when the load ratios are 10% and 25%, while it brings about the increment of the NOx emission and the decrement of the fuel efficiency in a moderate duty. In the low-temperature combustion mode, the combustion efficiency can be dramatically improved by decreasing the intake temperature and putting off the ignition phase, the in-cylinder temperature can be decreased, and the production of NOx is restrained at the same time. The soot emission can be reduced by raising the intake temperature appropriately when the load ratio is 10%, while intake cooling plays an important role in cutting the soot emission down at the load ratios of 25%and 50%.Multi-injection strategy is an effective method to extend the operating scope of low-temperature combustion and ameliorate the trade-off relationship between the NOx and soot emissions. Pilot injection can reduce the main injection amount, and shorten the ignition delay period of the main injection fuel. As a result, the exothermic phase advances and the peak value of the heat release rate descend so that the soot is successfully restrained. What’s more, different injection parameters have different effects on the soot emission. Compared with the original engine, the NOx emissions decreased by 97.8%, 80.7%and 62.1%respectively when the load rates were 10%, 25%, and 50%, and the soot emissions decreased by 76%, 93.9%, and 47.1%, while the brake specific fuel consumptions increased slightly.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2014年第15期83-92,共10页
Transactions of the Chinese Society of Agricultural Engineering
基金
江苏省科技支撑计划(BE2013042)
常州市科技支撑计划(CE20120095)
江苏大学高级专业人才科研启动基金项目(13JDG075)
江苏省优势学科建设项目
关键词
柴油机
优化
燃烧
预混合低温燃烧
早喷射
废气再循环
diesel engines
optimization
combustion
low-temperature premixed combustion
early injection
exhaust gas recirculation
作者简介
尹必峰（1975-），男，副教授，博士，研究方向为发动机排放控制。镇江江苏大学汽车与交通工程学院，212013。Email：ybf@ujs．edu．cn
