Abstract
Comparative experimental studies of fuel sprays evolution dynamics in a constant volume chamber were carried out with a view to reduce the uneven distribution of diesel fuel in the combustion chamber when the Common Rail injector is inclined. The fuel sprays was captured by a high-speed camera with simultaneous recording of control pulses of camera and injector on an oscilloscope. Two eight-hole diesel injectors were investigated: One injector with identical orifice diameter (nozzle 1) and another injector with four orifices of the same diameter as orifices of nozzle 1 and four orifices of enlarged diameters (nozzle 2). Both injectors were tested at rail pressure from 100 to 165 MPa and injector control pulse width of 1.5 ms. The dynamics of changes in the spray penetration length and spray cone angle were determined. It was found that sprays develop differently in nozzle 1 fuel. The difference in the length of fuel sprays is 10–15 mm. As for nozzle 2, the fuel sprays develop more evenly: The difference in length is no more than 3–5 mm. The difference of the measured fuel spray cone angles for nozzle 1 is 0.5°–1.5°, and for nozzle 2 is 3.0°–4.0°. It is concluded that the differential increase in the diameters of nozzle orifices, the axes of which are maximally deviated from the injector axis, makes it possible to reduce the uneven distribution of fuel in the combustion chamber and improve the combustion process and the diesel performance as a whole.
Highlights
In modern diesel engines, the centrally-mounted fuel injector is often arranged inclined from the axis of the piston bowl, bypassing the valve cover, which facilitates its removal and installation.During injection, the fuel sprays form a “tent” shape and are dispersed symmetrically relative to the cylinder axis (Figure 1)
For the nozzle 1, the sprays from holes 4 and 5 have the greatest length. The axes of these spray holes are inclined from the axis of the nozzle by an angle of
While the shortest fuel sprays lie in holes 1 and 8, the axes of which are inclined from the greatest length
Summary
The centrally-mounted fuel injector is often arranged inclined from the axis of the piston bowl, bypassing the valve cover, which facilitates its removal and installation.During injection, the fuel sprays form a “tent” shape and are dispersed symmetrically relative to the cylinder axis (Figure 1). The nozzle orifices of injector are made at different angles from the injector axis. The fuel flows out from different orifices under different conditions. The alignment of the fuel–air mixture is provided by its swirl or displacement of the combustion chamber axis in piston. In high power diesel engines with a cylinder diameter larger than 150 mm, an open combustion chamber of the Hesselman type is often used. In this case, the mixture formation is performed without air swirl, and the fuel is distributed unevenly over the combustion chamber. On one side of the combustion chamber where the mixture is richer than that on the other (opposite), combustion runs at higher temperatures and more toxic substances (soot and nitrogen oxides) are formed
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