Study on the combustion and emission of coal-to-liquid/dimethyl carbonate blends under different injection strategies

Abstract

Coal-to-liquid (CTL) is a kind of clean fuel made by chemically processing coal, with a low sulfur content and low aromatic hydrocarbon content. Under the energy structure of China, where coal is abundant and oil is scarce, CTL technology can effectively alleviate the problem of oil shortage. However, the high cetane number of CTL results in lower premixed combustion, which causes increased particulate matter (PM) emissions. Dimethyl carbonate (DMC) shows the potential to reduce the reactivity of CTL with its low cetane number and high oxygen content. This study explores the impact of blending DMC with CTL on combustion and emissions through engine bench tests. The results show that the blending of DMC with CTL enhanced the engine’s brake thermal efficiency (BTE), reduced the pressure rise rate (PRR), and decreased both the total number of particles and their size. DMC blending combined with pilot injection (PI) strategies was able to reduce soot emissions, but excessive pilot-main interval (PMI) resulted in increased CO emissions. Increasing the pilot injection rate (PIR) was effective in reducing the PRR and CO emissions while increasing the BTE, but NOx emissions increased.