摘要
为探究均质引燃技术对柴油机整机排放特性的影响,该文在某六缸柴油机上,实现了均质引燃模式的多缸运行。试验以转速1 438 r/min、平均指示压力0.7 MPa的工况为代表,通过分析该工况下汽油比例与废气再循环EGR(exhaust gas recirculation)率对多缸均质引燃的影响,确立了汽油比例与EGR率优化的基本原则,并以此为依据完成整机ESC(European steady state cycle)测试。汽油比例及EGR率的分析指出:汽油比例高达90%时燃烧相位仍可有效控制;增大汽油比例可以带来NOx与炭烟(Soot)排放同时降低的显著效应,但汽油比例过大会导致最大压升率陡增;随EGR率增大,作为燃油主体的汽油均质混合气燃烧改善,适量EGR的引入可以优化缸内燃烧;随EGR率增大,NOx排放减少而Soot基本不变,可使用大比例EGR以进一步降低NOx排放。ESC测试结果最终表明:在仅借助柴油氧化催化转化器DOC(diesel oxidation catalyst)的情况下,NOx、一氧化碳CO(carbon monoxide)与总碳氢THC(total hydrocarbon)加权排放低至1.89、0.90、0.12 g/(k W·h),分别满足国Ⅴ标准2.00、1.50、0.46 g/(k W·h)的限值,由各点不透光烟度与加权系数乘积之和计算的Soot加权值也处于0.034 m^(-1)的极低水平。多缸均质引燃对降低柴油机整机排放成效显著,具备稳态测试全面达到国Ⅴ排放标准的潜力。
Homogeneous charge induced ignition （HCII） is an effective way to reduce NOx emission and soot emission simultaneously while keeping high thermal efficiency. However, the former research about it was limited to single cylinder engine which was original or modified by multi-cylinder engine. Usually, separate intake system, exhaust system and fuel supply system would be set up for the test cylinder, while fuel supply to the other cylinders was cut off. Thus, there was only the test cylinder working normally for the experimental engine. Besides, a fuel-free air compressor, as an external equipment not belonging to the engine body, was used to replace turbocharger. Therefore, the experimental condition of intake-exhaust, EGR （exhaust gas recirculation） - turbocharger coupling effect and mechanical loss was quite different from which engines actually worked in. To study the real emission performance of HCII, a six-cylinder turbocharged diesel engine was modified to achieve MHCII （multi-cylinder homogeneous charge induced ignition, which means all cylinders operate in HCII mode simultaneously） in this paper. The experimental engine incorporated an extra gasoline injection system, and the technology of intake port MFI （multi-point fuel injection） was used, while diesel injection kept the original high pressure common rail system without any change. Furthermore, a dual-fuel ECU （electronic control unit） that could be adjusted flexibly was equipped to control both of the fuels. The whole research in this paper included 2 aspects. Firstly, the influence of gasoline ratio and EGR ratio on MHCII was studied in a typical engine working condition, i.e. rotating speed of 1 438 r/min and IMEP （indicated mean effective pressure） of 0.7 MPa. Based on it, the basic principles of optimizing these 2 parameters were established. Secondly, DOC （diesel oxidation catalyst） device was matched to the experimental engine and the ESC （European steady state cycle） test was conducted under the guidance of those
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2017年第19期108-114,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(51576116)
关键词
柴油机
排放控制
试验
均质引燃
多缸运行
ESC测试
diesel engines
emission control
experiments
homogeneous charge induced ignition
multi-cylinder operation
ESC test
