Effect of Gasoline Fuel Additives on Combustion and Engine Performance

5.4
 
Conclusion 
This chapter has presented the results of an investigation into the effects of fuel 
additives on the physical properties of base gasoline fuel. Fundamental gasoline spray 
formation characteristics were investigated for 17 fuel additives from 6 functional 
groups in two different additive concentrations through the use of a Malvern laser 
diffraction system. Additionally, a non-fuel bound viscosity modifying additive was 
investigated. The study, based on the measured SMD values, indicated that effects 
from fuel additives are too small to be quantified under the chosen conditions by the 
selected methods. 
Surface tension and viscosity measurements of base gasoline fuel with the 
higher concentration of additive revealed that the fuel additives, in quantities used in 
the industry, are unlikely to affect their physical properties. Only exceptions to this 
were the drag reducing agents that are meant to increase fuels viscosity to reduce 
turbulent flows in pipe lines. However, their effectiveness is greatly reduced during 
high pressure injection events where the fuels lost more than 45 % of their viscosity 
as a result of probable shear degradation. Furthermore, due to their purpose in the 
distribution systems and their tendency to break up in turbulent flows, likelihood of 
the drag reducing agents making their way into the vehicle fuel systems in the tested 
concentrations is practically non-existent.
Additional investigations with single component fuels and their binary 
mixtures were carried out to confirm the extent to which fuel blend components affect 
the mixture properties. As initially anticipated, the mixture properties were affected 

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5.4 Conclusion 
137 
proportionately to their constituent components. On this basis, it is clear that even at 
maximum quantities (CI-I 10X, 10g/L of fuel), the proportion of additive in the fuel 
mixture remains too low to affect their physical properties.
The findings agree with the study carried out by Patel [113], who found that at 
ambient environmental conditions DCA and CI additives did not have an effect on 
high pressure diesel sprays. The present study added several new additives to gasoline 
fuel but again found the additives to not alter the spray characteristics from the base 
fuel. Therefore, the only effects seen from the additives under high pressure GDI 
environments are expected to occur within their functional areas.

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