| The use of coal-based oxygenated blended fuel in diesel engine can simutanuously solve the problems of engergy shortage and environmental pollution in China.F-T fuel is obtained from indirect liquefaction of coal with high cetane number,low sulfur content and aromatic hydrocarbon content.Polymethoxy dimethy ether(PODE)is a coal-based oxygenated fuel with higher oxygen content and good mutual solubility.The combustion and emission characteristics of diesel engine can be further improved when fueled with PODE/F-T coal-based oxygenated blended fuel.The fuel used in this paper were pure diesel,F-T fuel,and PODE/F-T coal-based oxygenated blended fuel with PODE volume ratio of 10%,20%and 30%,respectively,which was marked as FTP10,FTP20 and FTP30 sequentially,while the mutual solubility stability and thermal properties of the blended fuel were tested.The evaporation and oxidation characteristics of PODE/F-T coal-based oxygenated blended fuel were studied by the thermogravimetric analyzer.The results show that,with the increase of PODE mixing ratio,the activation energy of the blended fuel was reduced and the evaporation and oxidation characteristics were improved.The combustion and emission characteristics of diesel,F-T fuel,FTP10,FTP20and FTP30 were compared and analyzed through the bench test.The results show that,under the rated working conditon,compared with diesel,the maximum cylinder pressure,the rate of pressure rise and the peak value of heat release of F-T fuel were decreased significantly.The specific fuel consumption was decreased by 3.2%and the thermal efficiency was increased by 1.4%.The volume fraction of HC,CO,NO_x and exhaust smoke were decreased by 15.2%,33.7%,36.8%and 8.1%,respectively.Compared with F-T fuel,with the increase of PODE mixing ratio,the maximum cylinder pressure and the rate of pressure rise were increased continuously,while the peak value of heat release rate was increased continuously,the specific fuel consumption were increased by 5.9%,12.8%and 23.2%,respectively,the thermal efficiency were increased by 2.4%,4.6%and 3.9%,respectively,CO were decreased by 5.3%,7.9%and 14.3%,respectively,HC were decreased by 7.6%,12.2%and17.7%,respectively,exhaust smoke were decreased by 21.5%,31.6%and 46.3%,respectively,and NO_x were increased by 3.8%,6.5%and 10.5%,respectively.The proportion of SOF and Soot in particulate matter for diesel engine after burning various fuels were studied through the thermogravimetric test,and the oxidation characteristic of Soot in the particulate matter was also analyzed.The results showed that,compared with diesel,the proportion of SOF in particulate matter of F-T fuel was increased by 12%,the proportion of Soot was decreased by 1.2%,the peak weight loss rate of SOF and Soot were increased by 9.9%and 3.9%,respectively,the initial and final weight loss temperature of the particulate matter were decreaesd by 7.1%and 2.3%,respectively,the initial combustion temperature and peak weight loss temperature of SOF were decreased by 7.3%and 3.7%,respectively,and the initial combustion temperature and peak weight loss temperature of Soot were decreased by 1.4%and 2.6%,respectively.Compared with F-T fuel,the proportion of SOF in FTP10,FTP20 and FTP30 particulate matter were increased by 4.7%,13.6%and 24.3%,the proportion of Soot were decreased by 1.5%,2.6%and 4.2%,the peak weight loss rate of SOF were increased by 6.4%,11.5%and 17.5%,respectively,and the peak weight loss rate of Soot were increased by 7.4%,13.5%and 18.8%,respectively.With the increase of PODE mixing ratio,the TG and DTG curves were shifted to the low temperature region gradually.In additon,the initial and final weight loss temperature of the particulate matter were decreased by 10.9%and 5.2%on average,the initial combustion temperature and peak weight loss rate temperature of SOF were decreased by 11.8%and 7.7%on average,and the initial combustion temperature and peak weight loss temperature of Soot were decreased by 5.9%and3.2%on average,the particulate matter were more susceptible to oxidative combustion reaction,which is beneficial to the regeneration of the diesel particulate filter.The combustion chamber model of diesel engine was established based on the simulation software AVL-FIRE,and the temperature field and concentration field distribution in the combustion chambers of diesel,F-T fuel,FTP10,FTP20 and FTP30 were analyzed.The results show that,compared with diesel,the highest average temperature of F-T fuel in the combustion chamber was decreased by 4.5%,the final oxygen mass fraction was decreased by 4.3%,the maximum NO production was decreased by 28.6%,and the maximum Soot production was decreased by 18.8%.Compared with F-T fuel,with the increase of PODE mixing ratio,the highest average temperature in the combustion chamber were increased by 2.9%,3.7%and 4.3%,respectively,and the distribution range of high temperature region was expanded continuously,the region of low oxygen concentration was increased first and then decreased,the final oxygen mass fraction were decreased by 10.7%,13.7%and 16.7%,respectively,the NO was generated in advance,and the maxium production were increased by 8%,22.2%and 29.3%,respectively,while the production and high concentration region of Soot were decreased continuously,the maximum production of Soot were decreased by 26.9%,38.2%and 52.5%,respectively. |
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