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The paper discusses the analysis of ethanol (E85) fuel atomization generated by piezoelectric fuel injectors operating in a high-pressure gasoline direct injection system. The methodology and tests results of the influence of the fuel (E85) 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. The tests were performed for one value of the air backpressure (1.5 MPa; as in modern supercharged DI engines) at the injection pressures of 5 and 20 MPa. The following comparative indexes were analyzed: linear and radial spray penetration during the injection and the velocity of the spray propagation. The investigation consisted in a visual recording of the process of fuel (ethanol E85) injection realized into a high pressure chamber.

In the paper the results of a comparative analysis of the changes in the fuel spray shape, penetration and its angle in the piezoelectric injection have been discussed. The results of the observation of the fuel (bio-diesel) spray with the use of high-speed camera (100 μs frame frequency) have been presented. The tests were performed for a multi hole piezoinjector and each time the whole fuel spray was observed and analyzed. The injector was placed in a closed chamber with an adjustable backpressure in the range of 0-4.5 MPa. At this stage of the research the authors investigated the influence of the chamber backpressure on the fuel spray shape, atomization and spray front displacement. Moreover, the parameterization and digital processing (including automation) of the obtained images have been presented, too. The influence of the pressure and the timing of the injection on the variable-in-time spray parameters have been shown.

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.