| Biodiesel and ethanol are green,renewable energy sources with high oxygen content,if blended with biodiesel or ethanol in diesel can not only effectively improve the combustion characteristics of diesel engines,but also reduce pollutant emissions and dependence on fossil fuels to achieve the purpose of sustainable development of mankind.In this paper,through the combination of experiments and numerical simulations,the ethanol/biodiesel blended fuel for diesel engine combustion is studied,and the main research work and innovation points are as follows:Firstly,based on the geometric parameters of diesel engine cylinders,CAD software and AVL-FIRE software were used to draw and establish cylinder geometric models and three-dimensional simulation models respectively.Secondly,the Chemkin code coupling AVL-FIRE is used to simulate the spray combustion process of different proportions of biodiesel/diesel blended fuel and pure biodiesel under different loads,and the simulation results are verified by experiments.Then,the combustion and emission characteristics of diesel engines,biodiesel and biodiesel/diesel blended fuels were explored.The results show that with the increase of the proportion of biodiesel,the fuel consumption of the diesel engine increases,the heat release rate decreases,CO and Soot emissions are significantly reduced,but NO emission increase.Secondly,in order to improve the applicability of biodiesel,a one-dimensional model of diesel engine and a three-dimensional diesel engine cylinder simulation model are first constructed,and the model is verified by experiments.The boundary conditions of the one-dimensional model were coupled with the three-dimensional cylinder model to explore the effects of ethanol/biodiesel with different ethanol blending ratios on the combustion and emission characteristics of diesel engines.The results show that the 20%ethanol blending improves the combustion characteristics of the fuel blend and reduces pollutant emissions.Then,the effects of different injection advance angle,EGR rate and boundary conditions on the combustion and emission characteristics of ethanol/biodiesel blended diesel engines with 20% ethanol blending ratio were explored.The results show that early fuel injection is beneficial to improve the combustion characteristics of the blended fuel,but it will increase the emission of pollutants in the cylinder.Increasing the EGR rate will lead to a decrease in cylinder pressure and temperature in the cylinder,and a decrease in the emission of pollutants in the cylinder.Increasing the intake pressure and lowering the intake air temperature helps to improve the combustion and emission characteristics of the fuel blend.Finally,the response surface design method is used to optimize the diesel engine performance of ethanol/biodiesel blended fuel.Firstly,29 sets of experiments were designed for different injection advance angles,EGR rate,intake pressure and intake air temperature by using the response surface design method,and the quadratic regression equations based on NO and Soot generation were obtained,the interaction affecting NO and Soot generation was explored,and the optimal solution generated by NO and Soot was obtained.Secondly,the results are verified by simulation.The results show that the response surface design within a reasonable error range can optimize the emission characteristics of ethanol/biodiesel blended fuel.Then,according to the optimization results,when the intake pressure,intake air temperature,fuel injection advance angle,EGR rate are 0.175 MPa,406.145 K,-9.274 °CA BTDC,19.993%,the NO and Soot in the cylinder are the lowest,141.114 ppm and 433.12 ppm,respectively. |
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