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The paper discusses the analysis of gasoline atomization generated by piezoelectric fuel injectors operating in a high pressure direct injection system. The methodology and tests results of the influence of the fuel injection pressure and combustion chamber back pressure on the changes of the fuel spray geometrical parameters during the injection and on the values characterizing the injection quality have been presented in the paper. It was stated that the growth in the back pressure by 50% results in a decrease in the linear spray penetration by 15% and a change in the injection pressure by 25% reduces the spray penetration by 1.6-4%. Similar relations are found for the fuel spray area and are even stronger for the spray penetration velocity.

The paper presents experimental and model research related to the fuel spray - wall interaction in terms of pressure and air back-pressure variability. Using a constant volume chamber the authors performed a qualitative and quantitative analysis of the fuel spray reaching the piston. The experimental research was supported with a model research using the FIRE 2010 software by AVL. On this basis the fuel concentration and its distribution in individual areas of the combustion chamber were determined (in the piston combustion chamber). A greater impact of the injection pressure (rather than the back-pressure) on the fuel spray distribution in the combustion chamber was observed and on the fuel spray interaction with the chamber walls in the piston. In such a case the problems of the contact of a liquid fuel with the cylinder walls and/or the combustion chamber walls is becoming increasingly important in terms of the fuel film formation and HC emission intensification.