Effects of DME Fumigation on HSDI Engine Fuelled with Ethanol

摘要

A new method for using ethanol in diesel engine was developed to achieve high thermal efficiency and drastically low NOx emissions. In the study, ethanol was injected directly into engine cylinder around top dead center and was ignited by DME homogenous charge compression ignition combustion. A modified diesel engine was used to carry out the test and the combustion and regulated emission characteristics at different DME ratio (DME %) were evaluated. The results show that the overall heat release process and ignition timing depends significantly on DME %. At small DME %, the combustion displays a peculiar two-stage heat release. The first stage is associated with DME low temperature kinetic reaction, while the second stage is mainly ethanol premixed combustion, and its shape is an approximative isosceles triangle. Moreover, adoption of small DME retards the ethanol combustion phase and decrease ROHR and PRR but increase cycle-to-cycle variation. With optimal DME% NOx emissions are remarkably lower than those of base engine as BMEP is less than 0.27MPa. The effective thermal efficiency is comparable to that of diesel engine.