The influence of petrol injection parameters on the structure of geometry of fuel spray injected from outward-opening injectors

The paper deals with the issue of determining the geometry of fuel spray generated by the outward-opening type of injectors. The design of the outward-opening type injector is the reason for the initial fuel flow taking a circular shape (an empty cone). With increasing pressure of the injected fuel this geometry changes into a square one. The aim of the research was to determine the conditions of these changes and to propose how to define the geometry in the form of an indicator z (accepting positive values - for circular geometry, and negative values - for square geometry) as well as to generalize the equation zeq making it possible to determine the indicator of the fuel spray geometric structure changes. The defined indicator z shows that fuel injection pressure exceeding 15 MPa plays an important role in changing the geometric structure of the fuel spray. The back pressure of the medium into which the fuel is injected does not affect the determined value of the indicator. Additionally, an indicator of variation of radial penetration of the fuel spray CoV(Sr) and the indicator of linear to radial fuel spray penetration Sl/Sr-av were determined, which only under certain conditions can replace the z indicator.