| The gasoline direct injection engine ejects fuel into cylinder directly,which makes engine control to the load can reach the effect just like the quality regulation of the diesel engine,meanwhile,fuel evaporation atomization helps to reduce cylinder temperature,which can improve impulse coefficient effectively and make gasoline engine can achieve a higher compression ratio.Although the most direct injection machine still mix fuel and air with stoichiometric ratio now,power and economical performance are still advantages than the traditional port fuel injection engine.But gasoline direct injection engine has a certain disadvantage,due to the short formation time of the mixture,there is a local rich or weak situation,which makes the particulate emissions greatly increased.Emission regulations are gradually to be strict,the permission for manuscripts of Europe VI and State VI both limit the particulate emissions of gasoline engines.In order to enable the gasoline direct injection engine to continue to be used under the strict emission regulations,new technologies must be adopted to control its particulate emissions.The research mainly focuses on the aftertreatment device of gasoline engine——Gasoline Particulate Filter?GPF?.The unique structure of the interior of GPF and the use of porous media make the particles in the engine exhaust can be effectively removed.The role of DPF in large-scale use process have been able to prove effectively,but its effect on gasoline engine still need to be tested.Therefore,this study build a engine bench,which is used to collect relevant data as the boundary conditions to the model;this study also establish the mathematical model of GPF in order to study its operating characteristics and to optimize its structure.The results show that:1.After the bench test of engine with the existing GPF,the comparison of the original exhaust with the GPF test results can be seen,gasoline engine has many nuclear particles and gasoline engine particle size distribution is in bimodal pattern.GPF has obvious filtering effect on the nuclear particles and the accumulation of particulate matter.2.In the GPF simulation model,the particle regeneration module is added to calculate,the results indicate that GPF can effectively capture the gasoline engine particles.In the long run,the pressure drop is maintained at about 10kPa,it can ensure the engine on the back pressure requirements.After the installation of the GPF engine power has declined,fuel consumption has increased,but not obvious.3.The air flow rates are set to 0.01kg/s,0.02kg/s and 0.03kg/s,quality of particles and air mass ratio are 2×10-4,2×10-5 and 2×10-6.The results show that the filtration efficiency of GPF decrease with the increase of exhaust gas flow rate;GPF filtration has a higher efficiency in the higher proportion of particles.4.The GPF structure is selected and calculated,and the wall thicknesses are set to 4mils,8 mils and 12 mils,respectively,and the number of holes is 220,350 and 480.It is found that the wall thickness has a great influence on the performance of the collector.With the increase of the wall thickness,the efficiency of the collector is improved;but the hole mesh number has less influence on the capture efficiency of GPF,the filtration efficiency basically unchanged.Furthermore,the temperature of GPF inlet was changed to calculation.Because of the decrease of exhaust temperature through exhaust gas system,the inlet temperature could reflect the influence of position.The results show that:temperature has little influence for particulate accumulation,but for regeneration. |
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