Experimental Investigation On Combustion And Emission Of Low-temperature Premixed Combustion Of Biomass Fuels

In recent years, biomass fuels, which are clean and renewable, have attracted more and more attention. Biodiesel is similar with diesel in most properties, and can be applied to modern diesel engines. Research showed biodiesel can not only decrease engine out pollution but also relieve the energy crisis. At the same time, PPCI(partially premixed compression ignition), as a new combustion mode, can decrease NOX and soot simultaneously. And low-temperature premixed combustion is the main characteristic of PPCI. In this paper, low-temperature premixed combustion of biomass fuels is investigated on a turbo-charged diesel engine with common rail injection system. The combustion and emission characteristics are researched.The research of effects of injection timing, injection pressure and fuel property on combustion and emission of low-temperature premixed combustion was carried out with single injection strategy. And the difference between conventional combustion and low-temperature premixed combustion was compared. In low load, low-temperature premixed combustion can be realized by early injection and late injection. Compared to conventional combustion, the ignition delay was longer; and the peak heat release rate was higher. Both early and late injection can decrease soot, but NO increased in early injection while decreased in late injection. NO of BD(biodiesel from insect) was higher than that of SME(soybean methyl ester), while soot was lower. Higher injection pressure improved premixed combustion, and soot was decreased while NO increased. In middle load, diffusion combustion took the leading role, and low-temperature premixed combustion was not realized.The effect of pose injection was also investigated. Different main-post interval and post injection mass were employed. The results showed that post injection can decrease soot with NO nearly stable. And post injection mass was more influential than main-post interval.In the end, the mass-size distribution of engine out particulate was investigated with DLPI. A proper dilution ratio and sampling time were determined in the test. And the results showed that early injection and late injection can both decrease the total mass of particulate, but had little effect on the mass-size distribution. While post injection decreased total mass and had effect on the distribution at the same time.