Effect of Gasoline Fuel Additives on Combustion and Engine Performance

3.3
 
Summary 
Chapter 3 has presented the experimental equipment used for the 
characterisation of the effects of fuel additives on gasoline DI sprays and combustion. 
Figure 3.15 displays the overall work split schematics and methods and equipment 
used for each type of analysis.
The physical properties of fuels were tested through measuring changes in 
surface tension and viscosity and their effects on fuel sprays through droplet size 
analysis. Chemical kinetics were evaluated through combustion analysis. Heat release 
and emissions analysis were primary methods of study in the combustion vessel and 
also in the single cylinder engine. Additionally, combustion vessel tests with vaporised 
gasoline allowed for high speed imaging to be used for flame speed analysis. 

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3.3 Summary 
91 
Figure 3.15: Project schematics for measurement focus and associated hardware 

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92 
 
Chapter 4 
4
 
Base Fuel Characterisation 
This chapter explains the base gasoline fuel spray and combustion 
characteristics. The aim of the work was to establish conditions under which it was 
possible to successfully study the effects of fuel additives on fuel spray formation and 
combustion characteristics. First, the spray features are discussed and the experimental 
methodology for droplet size analysis for the subsequent additive investigations is 
presented. Thereafter, methods used in combustion investigations are explained. This 
includes combustion vessel experiments under ambient, heated and pre-combustion 
conditions as well as some selected engine testing.
4.1
 
Spray Features 
In order to determine conditions under which additive effects on fuel 
atomisation could successfully be assessed, base fuel characterisation under several 
different conditions was carried out. This included a study into the effect of fuel 
injection pressure and measurement location on droplet size where measurement 
location was defined as the spatial position of the laser beam within the spray plume 
in the x-z plane, as shown in Figure 4.1. For all experiments, injection period was kept 
at 2 ms. This time was found to be sufficient to allow for spray development and, as 

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4.1 Spray Features 
93