Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle

Penetration and spreading angle comparison in SF6 and N2 atmospheres at ρamb=7.6kg/m3 in the same test rig. [Display omitted] •Three ECN nominal identical injectors show differences in spray penetration.•The injector opening causes differences in the instantaneous spray penetration.•The gas composition affect spray penetration rate and spreading angle.•Increasing the temperature (at constant density) has no effect on spray penetration.•An analysis with gas jet theory has been performed to reproduce the results obtained. In this work, three Engine Combustion Network (ECN) single-hole nozzles with the same nominal characteristics have been tested under a wide range of conditions measuring spray penetration and spreading angle. n-Dodecane has been injected in non-evaporative conditions at different injection pressures ranging from 50 to 150MPa and several levels of ambient densities from 7.6 to 22.8kg/m3. Nitrogen and Sulphur Hexafluoride (SF6) atmospheres have been explored and, in the first case, a temperature sweep from 300 to 550K at constant gas density has been executed. Mie scattering has been used as the optical technique by employing a fast camera, whereas image processing has been performed through a home-built Matlab code. Differences in spray penetration related to spray orifice diameter, spreading angle and start of injection transient have been found for the three injectors. Significant differences have been obtained when changing the ambient gas, whereas ambient temperature hardly affects the spray characteristics up to 400K. However, a reduction in penetration has been observed beyond this point, mainly due to the sensitivity limitation of the technique as fuel evaporation becomes important. The different behavior observed when injecting in different gases could be explained due to the incomplete momentum transfer between spray droplets and entrained gas, together with the fact that there is an important change in speed of sound for the different gases, which affects the initial stage of the injection.