【作者】 张翔宇；

【导师】 郑尊清；

【作者基本信息】 天津大学 ， 动力机械及工程， 2010， 硕士

【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CH₄成分以及PM组分的变化规律。研究结果表明,NO₂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CH₄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。更多还原

【Abstract】 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, CH₄ 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 CH₄ 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.更多还原