Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 1 – Hydraulic performance

Abstract

Nozzle hydraulic performance has a significant impact on diesel spray development and combustion characteristics. Thus, it is important to understand the links between the nozzle geometry, the internal flow features and the spray formation. In this paper, a detailed analysis of the impact of the nozzle orifices inclination angle on its hydraulic performance is performed. For this purpose, three different nozzles with included angles of 90, 140 and 155 degrees are evaluated. Instantaneous injection rate and momentum flux are measured on a set of injector operating conditions (mainly injection pressure and discharge pressure). The results show that higher inclination angles lead to smaller mass 2 flow and momentum flux at steady-state conditions, due to the higher losses at the orifice inlet. These losses are translated in lower both area and velocity coefficients. Nevertheless, the impact of this parameter is limited thanks to the counteracting effect of the hydrogrinding process, which produces larger rounding radii at the orifice inlet as the included angle increases. Based on the experimental results, correlations of the discharge coefficient as a function of the Reynolds number are obtained and evaluated.

Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 2 – Spray characteristics

“…to 200 MPa (the same ones already seen for the hydraulic tests presented in [46]) at an ambient density of 50 kg/m 3 . The energizing time for these tests has been fixed at 1.5 ms for all the cases.…”

“…Regarding the other two nozzles, spray penetration is very similar for both of them, although the trend of reducing spray penetration when increasing the included angle is still appreciable. The relatively low differences between the nozzles is likely due to the effect of the inclination angle on the inlet rounding radii produced during the hydrogrinding process, as already discussed in [46]. The maximum spray penetration observed in the images is related to the arrival of the spray tip to the end of the visualization window.…”

“…. In order to facilitate the analysis, the spray penetration has been plotted together with the spray momentum data reported in [46]. As it can be seen, in both cases the spray penetration is faster for nozzle N1, which has the highest spray momentum.…”

“…This effect could be particularly important if cavitation took place in the orifices. Nevertheless, considering that no cavitation was observed during the previous hydraulic characterization of the nozzles [46], the expected impact is minor.…”

Discharge coefficient of high viscosity liquids through nozzles

“…A review of the literature revealed that test fluids for most studies were air, diesel fuel, water and glycerol (for high viscosity which is still relatively low) and focus was on angle orientations, entrance shape, cavitation number, design of nozzle; and for more recent studies, number of holes on the nozzletermed multi-hole nozzles (Zhong et al, 2014;Sun et al, 2015;Desantes et al, 2016;Zhou et al, 2016;Salvador et al, 2017). Some studies considered the length and diameter of the nozzles as separate factors.…”