小型涡流室柴油机供油与燃烧系统协同匹配

Matching of fuel injection and combustion systems for small swirl chamber diesel engine

小型涡流室柴油机的供油与燃烧系统优化是满足不断加严排放法规的基础。该文以某170F涡流室柴油机为研究对象,运用模拟计算与试验结合的方法,对其供油及燃烧系统开展研究。借助工程软件构建了供油系统仿真模型,通过设计长型短结构喷油器、优化供油系统参数,来提高喷油压力和优化喷油特性;利用FIRE软件对燃烧过程进行模拟,找出了喷油油线在涡流室内位置及燃烧室容积比的最佳范围。柴油机优化后整机初次试验气体比排放低于国家第三阶段排放限值,CO和HC+NOX分别较原机下降了72.8%和21.3%(八工况循环),标定工况烟度由原机4.5下降到1.2 BSU,有效燃油消耗率较原机下降了约16.1%。该研究工作为小型涡流室柴油机性能提高和节能减排提供了参考。

The huge annual output of single-cylinder diesel engines is a major feature of Chinese internal combustion engine industry. In China the amount of these engines with bore diameter below 80 mm accounts for 35% of domestic production. Most of these diesel engines adopt the swirl chamber combustion system. However, with the development of direct-injection process, many problems for these engines occur, such as large smoke emissions at full load, poor performance under low speed and high idle speed, and there are few basic researches on them. Therefore, the research of low-emission high-performance swirl chamber diesel engines contains certain academic significance and practical value. The 170 F swirl chamber diesel engine was used as the research prototype, and with the method of experiment and numerical simulation, the fuel injection and combustion systems were analyzed. By the design of new injector, the establishment of simulation model of injection system and the optimization of the injection parameters, the maximum fuel pressure under the rated conditions increased from 18.54 to 25.28 MPa, the initial injection rate reduced and the shape of injection rate was optimized. By the simulation of combustion with the software FIRE, the deviate distance from the injection oil line to the center of the swirl chamber and the best volume ratio were determined. The results showed that when the deviate distance from the injection oil line to the center of the swirl chamber was at 0.33-0.38 R（R is the radius of the swirl chamber）, and the volume ratio was in the range of 0.47-0.50, the mixing and combustion performance would be better. This study showed that in order to achieve the targets of low emissions and high performance, the injection parameters and performances of the swirl chamber diesel engine should be designed and optimized according to its displacement just similar with the direct-injection diesel engine. The test results of 170 F swirl chamber diesel engine showed that the brake specific fuel consumption（BSFC） of the original engine under the rated condition（2.6 k W, 3 000 r/min） was 327.3 g/（k W·h） and the smoke was 4.5 BSU. When the long-size short-structure nozzle was used and the fuel injection system was optimized, the BSFC and the smoke decreased to 282.2 g/（k W·h） and 2.0 BSU respectively. After the parameters of the combustion system were matched, the BSFC and the smoke dropped to 274.7 g/（k W·h） and 1.2 BSU respectively. The experimental results showed that the specific emissions of the optimized diesel were lower than the emission standards in Phase Ⅲ in China. Compared with results of the original engine, the CO and HC＋NOX emissions decreased by 70.3% and 20.9% respectively under the 5 conditions. Moreover, the CO and HC＋NOX emissions decreased by 72.8% and 21.3% respectively under the 8 conditions. The BSFC decreased by 16% and the diesel smoke was reduced from 4.5 to 1.2 BSU under the rated condition. The research provides a technology route of energy-saving and emission-reduction for swirl chamber diesel engines.