Effect of Gasoline Fuel Additives on Combustion and Engine Performance

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5.1 Gasoline Spray Investigations with Additives 
120 
 
Figure 5.2: SMD for gasoline with DRB additive at minimum transmission 
A non-fuel additive lauric diethanolamide, a commercially available viscosity 
modifier, was further investigated for possible effects on droplet size. It was hoped 
that the additive would be more shear resistant than the drag reducing agents and 
changes in SMD measurements would be noted. The results are displayed in Figure 
5.3. Treat rate was taken as the maximum used in test fuels (CI-I). At the tested 1,000 
ppm treat rate no change to droplet size was noted. It can be noted, however, that
Figure 5.3: SMD for gasoline with 1,000 ppm lauric diethanolamide at minimum 
transmission 
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5.1 Gasoline Spray Investigations with Additives 
121 
industrially, lauric diethanolamide treat rates of more than two orders of magnitude 
higher are employed [238, 239] but due to reduced proximity to fuel additive quantities 
employed commercially, no further study was carried out. 
In general, the pressure effects from the high pressure injection system seemed 
to overpower any additive effects that might have been present. Representative SMD 
results of gasoline sprays with additives from different functional groups can be seen 
in Figures 5.4 – 5.8. It should be added that for typical PFI fuel metering systems,