摘要
为了探索小型非道路柴油机采用内部废气再循环技术改善其排放性能的有效途径,该文提出了一种在进气凸轮上增加预进气凸轮实现柴油机内部废气再循环(internal exhaust gas recirculation,IEGR)的方案。通过拍摄柴油机燃烧过程中的火焰图片、测试缸内压力、计算燃烧放热率、火焰温度场、碳烟浓度分布场以及有害污染物的排放测试,对比分析了实施内部废气再循环前后,小型非道路柴油机燃烧过程及排放性能的变化趋势。结果表明:1 760 r/min、50%负荷工况下,引入IEGR后由燃烧放热引起的第二压力峰值由5.49下降到5.43 MP,燃烧放热始点推迟了0.5℃A,瞬时放热率峰值由85.7下降到82.4 J/deg;缸内燃烧火焰平均温度降低,高温强辐射区域面积占有率峰值由30下降到10‰以内,而表征碳烟浓度的KL因子平均值的峰值由原机的40.5上升到67.4,且高浓度区域的比例显著增加。1 760 r/min转速,引入IEGR后各负荷工况下的NOx排放均有所降低,而碳烟排放则呈现增加的趋势;结合供油提前角的协同优化,可以实现部分负荷工况下有效燃油消耗率、NOx及碳烟排放的同时降低,具有以实现整机性能优化的潜力。该研究工作为内部废弃再循环技术在小型非道路柴油机上的应用提供了参考。
With the sustained development of economy and technology, small non-road diesel engines are extensively applied in industrial and agricultural production. The single-cylinder engines, in particular, plays a crucial role in modern agriculture, working as the main power source for small-to medium-sized tractors and mini-farming machinery etc. Due to current situation of fuel issue in China and structure limitation of single-cylinder diesel engine, a new method is presented to improve combustion and emission performance using internal exhaust gas recirculation （IEGR） in terms of engine internal purification, that is, by adding advance intake profile to intake cam shaft. As for the small-sized non-road diesel engine, an optical engine equipped with the AVL Visio scope consisting of a charge coupled device （CCD） camera Pixel-Fly VGA, an endoscope, illumination device and the AVL-Thermo Vision software was used in order to capture combustion images. In addition, the AVL-Thermo Vision software was applied in the measurement of temperature and soot distribution of diffusion flame. The resolution and frequency of CCD camera were 640 × 480 pixel and 10 Hz respectively. By means of images collecting and processing for combustion process, together with pressure collecting and emission performance testing, the influences of IEGR on the diesel engine’s combustion process and emission performance were analyzed. The results showed that under the conditions of 1 760 r/min and 50% load rate, in-cylinder pressure peak decreased from 5.49 to 5.43 MPa, the start of heat release was delayed by 0.5 °CA and the maximum instantaneous heat release rate was reduced from 85.7 to 82.4 J/deg when IEGR was introduced. Furthermore, the average temperature of combustion flame was reduced, centering between 1 900 and 2 100 K. The area of high-temperature intense radiation was reduced, in which the area percent of temperature higher than 2 200 K dropped from around 30 ‰ to below 10 ‰. That was beneficial to controlling NOx emissions. The average value for KL factor was obviously higher than that for the original engine within the entire range of combustion, the peak of which rose from 40.5 to 67.4. At the speed of 1 760 r/min, the NOx emissions decreased within the entire range of load rate, especially under 50% load rate （by 19.6 %） when IEGR was introduced. Yet, the soot emissions increased as the load rate was increased and the growing rate became even larger at higher load rate. The soot emissions rose by 49.33% when full load rate was achieved. Another countermeasure, i.e. the fuel supply advance angle, was adjusted to collaboratively optimize engine performance. NOx and soot emissions could be improved simultaneously. When the fuel supply advance angle was extended longer from 8 to 12 °CA, for example, NOx emissions rose up but was still improved in relation to that produced from the original engine, while soot emissions were decreased substantially thus better than that of the original in the load range from small to medium. Also, brake specific fuel consumption could get to a relatively low level at partial load rate. Therefore, it is validated that this method has the potential to improve engine performance comprehensively and the present work can provide theoretical basis for the application of IEGR on small-sized non-road diesel engine.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第10期37-42,共6页
Transactions of the Chinese Society of Agricultural Engineering
基金
江苏省科技支撑计划(BE2013042)
江苏省优势学科建设项目(PAPD)
中国博士后科学基金面上项目(2014M560400)
江苏大学高级专业人才科研启动基金项目(13JDG075)
关键词
柴油机
燃烧
排放控制
内部废气再循环
可视化
diesel engines
combustion
emission control
internal exhaust gas recirculation
visualization
