柴油机伞帘喷雾燃烧系统的试验研究

在四气门单缸柴油机上研究了伞帘喷雾(UCS)燃烧系统性能．结合喷油过程测试结果和缸内空气运动数值模拟结果，综合分析了试验结果．结果表明，与原机相比，UCS系统的燃油经济性明显提高，烟度、最高燃烧压力、排气温度和NOx排放明显降低．这归因于喷雾碰壁引起的喷雾体积和空气卷吸量增加及燃油的二次雾化．但在中低负荷工况，由于壁面温度低，其CO和HC排放量明显高于原机．它在上止点后着火；着火时，准伞形喷雾和帘状喷雾的扩展范围已很大．

Experimental Study on Umbrella-Curtain Spray Combustion System for Diesel Engine

The umbrella-curtain spray(UCS) combustion system was developed to improve the mixture formation and combustion by adopting spray impingement and reentrant combustion chamber. The nozzle and combustion chamber cooperated to produce a quasi-umbrella spray in the central region and several curtain-sprays in the peripheral region. In this way, not only is the promoting effect on fuel/air mixing by spray impingement made full use of, but also the wetting wall is greatly reduced. The performance of this combustion system was investigated on a single-cylinder four-valve diesel engine. Experimental results were comprehensively analyzed by associating them with the measured results of the corresponding injection process and the numerical simulation results of the corresponding in-cylinder air motion. The results show that the fuel economy is markedly improved, and that simultaneously the smoke intensity, maximum combustion pressure, exhaust temperature and NO_x emission are evidently reduced. This is attributed to the resultant increase in spray volume and secondary fuel atomization from spray impingement. But under low load, the HC and CO emissions with UCS combustion system are higher than that with base conventional combustion system. In the former, the mixture ignites after TDC, when the quasi-umbrella spray and curtain-sprays have extended greatly.