Structure Design And Research On Performance Characteristics Of Air Assisted Fuel Injection

The engine direct injection technology can effectively improve the engine power, fueleconomy and emission, however the high pressure injector as a key part for the applicationof gasoline direct injection(GDI) technology could easily cause the fuel wetting wall whichwould lead to bad combustion process. In order to eliminate the phenomenon of fuel wettingwall in the case of high pressure injection, based on the principle of air assisted atomizationof fuel,this paper designed the air assisted injector in the low pressure fuel injection system,It can achieve good fuel atomization in lower working pressure and give full play to theadvantages of GDI technology.First of all, this paper studied the composition of air assisted injector system, theory ofair atomization of fuel, and get the structure scheme of the air assisted injector according tothe design principles and requirements of the injector, this structure scheme mainly includesthe fuel supply part, the air supply part and the mixed gas injection part, then the feasibility ofthe scheme was analyzed.Secondly, according to the structure scheme of the air assisted injector established, thispaper analyses the characteristics and working principle of the structure, get the structureparameters of the air assisted injector, carried on the theoretical analysis and the numericalcalculation on its performance, checked performance index, established the three-dimensionalmodel and get the relevant geometry parameters of air assisted injector by CATIA software.Finally, this paper established the physical model and mathematical model of the airassisted injector, and built the air assisted injector numerical simulation model to complete thecalculation of working performance by AVL-HYDSIM software platform. The simulationresults show that the working performance of injector are in agreement with theoreticalcalculations and meet the design requirements. this paper also analysised the characteristicsof air assisted injector and get effects of the key parameters on the characteristics of the injector. Then the minimum pressure difference between the air supply pressure and fuelsupply pressure is optimized, and obtained the minimum value. The structure parameters ofthe air assisted injector were also optimized, getting the valve seat surface stress of the airassisted injector reduced，the closing time of the needle valve shorten and the quality of fuelatomization improved.Based on the GDI engine, this paper finished the structure design of the air assistedinjector, analyzed the working characteristics, optimized the pressure difference between theair and the fuel supply pressure and adjusted the other parameters. The calculated data andsimulation results show that the injector designed meet the design requirements.