Research progress on the spray, combustion and emission of polyoxymethylene dimethyl ethers as a diesel blend fuel: A review

Polyoxymethylene dimethyl ethers (PODEn) is a promising blend fuel for diesel, with high cetane number, volatility and molecular oxygen content. It has abundant feedstocks and mature technology for synthesis process. PODE3 and PODE4 are the most optimal components, and in practice 70.9% PODE3-5 can be acquired from dimethoxymethane and trioxane by using the alkanesulfonic acid-functionalized ionic liquids as the catalyst. Blending PODEn in diesel improves the spray and atomization quality, verified by the increase of spray cone angle in non-evaporation conditions and the decrease of spray mean diameter. PODEn addition increases the blue combustion flame, decreases the yellow flame, increases the combustion temperature and reduces the KL factor. The chemical kinetic mechanism of PODE3 indicates that PODEn can generate active OH radicals at both low and high temperature environment, which is favorable for accelerating the combustion speed, promoting the heat release, increasing the diffusion combustion intensity and thereby increasing the combustion efficiency. Engines fueled with diesel PODEn blend fuels can remarkably improve the combustion process, increase the brake thermal efficiency (BTE), and reduce the PM, HC and CO emissions, while increase the NOx emissions. Besides, the PM distribution moved to smaller particle size and the mean diameter also decrease. Further, the nano structure of PM proves that it can be easier oxidized. Through comprehensive analysis on fuel property, BTE and engine combustion and emission, it is suggested that the mixing volume ratio of PODEn should be no more than 20%.

Automated summary

Polyoxymethylene dimethyl ethers (PODEn) is a promising blend fuel for diesel, which improves combustion efficiency, increases thermal efficiency, and reduces emissions.