柴油掺烧甲醇预混合燃烧和排放特性

Characteristics of combustion and emissions of the diesel/methanol premixed compound combustion

在一台六缸柴油机上搭建了进气喷射甲醇掺烧系统,对不同替代率下的柴油掺烧甲醇工况燃烧和排放特性进行了试验研究。试验结果表明:掺烧甲醇改变了发动机的燃烧特性。随甲醇替代率的上升,预混合燃烧比例逐渐增大,扩散燃烧比例则减小。掺烧甲醇后,缩短了整体工况的燃烧持续期,使放热更加集中,改善了燃烧等容度。掺烧甲醇还会从散热系统回收一部分热量,共同作用下使热效率得到大幅提高。但大比例掺烧甲醇也会对NOx及CO排放带来恶化,并生成甲醇与甲醛等非常规排放物。同时掺烧甲醇还会延长滞燃期,因此需要调整柴油的主喷正时以保证发动机运转稳定。

An inlet injection system of methanol was built in a six cylinder diesel engine to investigate the combustion and emission characteristics at different substitution rates under the condition of diesel/methanol compound. The test results show that the combustion characteristics of the engine has changed with the methanol compound combustion. With the methanol replacement rate increases, the premixed combustion ratio increases and the diffusion combustion ratio decreases. With the methanol compound combustion, the overall combustion duration shortened, heat is more focused and improve the combustion content. The methanol compound combustion can also recover a part of heat from the cooling system, together with the joint effect of the heat efficiency is greatly improved. However, the high methanol replacement rate will bring the deterioration of the NOx and CO emissions with the methanol and formaldehyde emissions. The methanol compound combustion will also delay the cylinder starts burning time, it is have to adjust the main injection timing to ensure the stable operation of the engine.