Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 4.2: Effect of location on transmission at 50 bar injection pressure 
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4.1 Spray Features 
95 
Figure 4.3: Effect of location on transmission at 110 bar injection pressure 
It is noteworthy that two extra readings were made at 50 bar injection pressure 
compared to 110 bar. This is due to fuel quantities in the measurement location being 
below the Malvern system cut-off threshold of minimum 5 % laser obstruction. 
Appendix A displays a typical injection at 50 bar and 110 bar. No difference in the 
spray cone angle could be noted up to an axial distance of around 25 mm but with 
increasing axial distance from the nozzle it is thought the lower momentum carried by 
the fuel with 50 bar injection pressure caused an increase in radial movement of fuel 
droplets due to aerodynamic drag compared to 110 bar injection pressure. This meant 
that at 110 bar at locations x = -30 mm and x = -35 mm, spray density was too low to 
be reliably measured. 
Figures 4.4 and 4.5 display the effect of location on measured SMD for 50 bar 
and 110 bar, respectively. It can be seen that initially large droplets are present 
followed by small droplets for short period of time. Before reaching a plateau value 
for the duration of measurement, a short period of increased droplet sizes occurs. It is 
evident that this feature diminishes as measurement is taken at a further off axis 
position. This is likely to be due to the fact that the measurements were taken on the 
fringe of the spray jet, if not completely outside the spray focus area where only small 
quantities of fuel are present and aerodynamic force effects on the fuel droplets are 
greatly increased. As a result, lower droplet velocities are experienced and greatly 
reduced temporal variation of droplet size is observed. 
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