Effects of EGR Dilution on Combustion and Emission Performance of a Compression Ignition Engine Fueled with Dimethyl Carbonate and 2-Ethylhexyl Nitrate Additive

摘要

The combination dimethyl carbonate (DMC)/diesel-blended fuels and the exhaust gas recirculation (EGR) can decrease nitrogen oxide (NOX) and soot emissions simultaneously emitted from the compression ignition engine. Nevertheless, the low cetane number of DMC/diesel mixtures at low loads results in a delayed combustion phase. The combustion phase has a significant influence on the engine emissions and combustion performance. Therefore, 2-ethylhexyl nitrate (EHN) must be added as cetane improver to fuel blends to ensure that the DMC/diesel mixtures have suitable combustion performance. In this paper, a four-cylinder diesel engine was used to investigate combustion and emissions performance. The five test fuels included diesel (D100) and a mixture of 20% DMC with 80% diesel (DMC20). In addition, EHN was added to DMC20 at ratios of 0.5%, 1%, and 2%. The results showed that the DMC20 increased the maximum heat release rate (MHRR), ignition delay (ID), and maximum pressure rise rate (MPRR) and reduced the soot emissions, nucleation, and accumulation mode particles. However, the brake-specific fuel consumption (BSFC) increased, and the brake thermal efficiency (BTE) decreased. Furthermore, when using the EGR, the NOX emission significantly decreased. When adding EHN to DMC20, the ID was shortened, the combustion phase advanced, and the MPRR decreased. The BTE first decreased and then increased with increasing EHN proportion. In general, use of the EGR coupled with DMC and EHN simultaneously decreased the NOX-soot emissions, and use of 0.5% and 1% EHN in combination with 20-30% EGR led to better engine emissions and combustion performance.