Dimethyl carbonate (DMC)/diesel blended fuels are receiving increasing attention due to the advantages of DMC (oxygen content 53.3%) that improved the fuel-rich zone of diesel engines. However, the low cetane number (CN) of DMC/diesel dual-fuel at low loads resulted in a delayed combustion progress. Since the combustion phase had a significant effect on thermal efficiency, exergetic efficiency, energetic and exergetic losses; 2-ethylhexyl nitrate (EHN) was added to the mixed fuel as a CN improver, so that the combustion phase closed to that of diesel to ensure proper combustion characteristics of the DMC/diesel dual-fuel. In this study, a four-cylinder turbocharged diesel engine was used to study performance and emissions. Based on experiments, combustion characteristics including energy balance and exergy balance were focused, in which the EHN was added to the DMC/diesel mixture at different concentrations. 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 a ratio of 0.5%, 1%, and 2%. The results showed that EHN could shorten the ignition delay time of DMC and reduced maximum pressure rise rate (MPRR). The use of EHN improved brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC), under the same load, using 0.5% and 2% EHN, BTE increased by 0.2% and 1%, relative to DMC20, respectively. The study found that the energy efficiency and exergy efficiency were higher after adding EHN, which made up for the burning problem of DMC. Moreover, the irreversible loss reduced, and the available work and available energy increased. Thermodynamic analysis showed that DMC had better combustion performance than diesel after adding 2% EHN. In this study, the method of EHN/DMC/diesel blended fuel combining with 25% EGR was proposed and confirmed that the trade-off relationships of NOX and soot have been improved noteworthy.

» Author: Mingzhang Pan, Weiwei Qian, Rong Huang, Chengzheng Tong, Haozhong Huang, Leilei Xu, Bin Hao

» Publication Date: 01/11/2019

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