Abstract
The paper presents the results of a comparative analysis of the changes in the injection spray shape and penetration and its vertex angle during the injection through piezoelectric and electromagnetic fuel injectors. The results of the observation of the fuel spray with the use of high speed camera (100 us frame frequency) have been presented. Moreover, the parameterization and digital processing (including its automation) of the obtained image have too been presented. The influence of the pressure and the timing of the injection on the variable-in-time spray parameters have been shown. A mathematical model describing these relations has been proposed.
The here presented Hiroyasu and Dent models are fit for larger diameters of the injector holes (above 0.2 mm in diameter); this is also confirmed in other investigations. As far as the fuel spray penetration is concerned the models show smaller penetration values than it results from the experiments.
The speed of propagation of the fuel spray front is higher for the piezoelectric injector; its maximum value reaches approximately 190 m/s for the injection pressure of 50 MPa and approximately 220 m/s for the injection pressure of 100 MPa; in both cases the values are lower than those obtained in the calculations.
Including the backpressure in the test stand investigations leads to a better convergence of the empirical models and the experimental values.
Keywords: fuel injection, injection spray indexes, fuel spray parameters, injectors, optical investigations