| In face of the continuous energy shortage and strict emission regulations,energy saving and emission reduction in the internal combustion engine industry has become particularly important.The blending of clean oxygenated fuels such as ethanol and n-butanol with diesel fuel has become an effective way to cope with energy scarcity and environmental pollution,and has attracted a great deal of attention from academia.Studies have showed that ethanol and butanol blends have great potential to effectively improve the performance,combustion efficiency and emission levels of diesel engines.In this paper,the effects of this fuel blends are investigated in depth by numerical simulation and experimental validation.In this study,a three-dimensional model of a diesel cylinder was developed using AVL-Fire commercial simulation software.Its operating parameters were also determined and the best spray,combustion and emission models were selected to achieve the best simulation results.The established engine simulation model was coupled with a chemical reaction mechanism containing 81 species and 377 reactions for simulation operations.To determine the accuracy of the developed model,the simulation results were verified by experimental data.After the model has been verified for accuracy,the combustion of diesel fuel blended with ethanol and n-butanol was simulated to analyze the effects of each fuel blend ratio on diesel engine performance,combustion and emission characteristics.In this work,the combustion of diesel-ethanol dual fuel was first simulated and calculated.The results showed that the thermal efficiency of the diesel engine increased by 2.24%,4.33%and 6.37%when the percentage of ethanol in the fuel blends was increased to 10%,20%and 30%,respectively.However,fuel consumption increased by 1.56%,3.49%and 5.74%,and power decreased by 1.58%,3.46% and 5.54%,respectively.In addition,CO emissions were reduced by 34.69%,47.60%and56.58%,and soot emissions were reduced by 7.83%,15.24%and 22.52%,respectively.Simulation results for diesel/ethanol/n-butanol ternary blends showed that diesel/ethanol/n-butanol blends resulted in lower diesel engine power and increased fuel consumption,but improved thermal efficiency.In addition,the fuel blends reduced CO and soot emissions.At 100%load,the diesel engine thermal efficiency was increased by 2.72%,2.69%,4.52%,4.49%,5.565%and 5.53%when the diesel engine was burning blends of E5N13,E10N5,E10N18,E15N10,E15N28and E20N10,respectively.However,fuel consumption increased by 2.79%to 5.84%and power decreased by 2.76%to 5.59%.At 50%load,the blended fuel reduced NO_xemissions by 8.39%to 21.81%,CO emissions by 12.1%to 22.91%,and soot emissions by 26.71%to 48.59%compared to diesel.Finally,the effect of injection timing on diesel engines burning different proportional fuel blends was investigated and multi-objective optimization of each parameter was carried out by response surface method using Design-Expert software.The results showed that properly advanced injection timing provided better combustion performance and fuel economy for the diesel engine,and significantly reduced CO and soot emissions,with a slight increase in NO_x emissions.The multi-objective optimization results showed that the diesel engine achieved a better match when the injection timing was 12.43°CA BTDC and the diesel blend ratio was 88.49%. |
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