Effect of Gasoline Fuel Additives on Combustion and Engine Performance

 
 
 
Chapter 6 
6
 
Effect of Fuel Additives on 
Gasoline Combustion 
In this chapter, the effects of fuel additives on gasoline combustion 
characteristics are discussed. Initially, the results from gasoline vapour combustion 
are presented. The chapter concludes with the outcomes from the experiments in the 
single cylinder research engine.
6.1
 
Experimental Additives 
Additives employed in the combustion investigations can be seen in Table 6.1. 
Although additives from all functional groups could in theory affect combustion, it 
was thought their main influence would come through changes to atomisation 
characteristics. Chapter 5 analysed the effects of additives on the physical properties 
of the base fuel and found the viscosity and surface tension not to be affected to an 
extent where changes in atomisation characteristics could be identified. As such, only 
CI additives were investigated. The additives in question were named as CI-A, CI-I 
and CI-Additional. CI-A was a commercially available diesel ignition improver 2-
EHN. Its main aim is to provide chain-branching and carrying radicals at low 

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6.2 Gasoline Vapour Combustion 
139 
Additive Group 
Additive 
Treat Rate (1X),
mg/L 
Increase in Cetane/
Octane Number at 1X 
Combustion 
Improvers 
CI-A 
250 
2-3 CN 
CI-I 
1000 
0.2-0.4 RON 
CI-Additional 
7000 
1.5-2.5 RON 
Table 6.1: Additives used in combustion investigations. CI-A is a cetane improver, CI-I and 
CI-Additional are octane improvers 
temperatures to shorten diesel ignition delay. In gasoline, it was likely to cause 
knocking behaviour, although as shown by Colucci et al. [11], in low concentrations 
benefits in the form of reduced misfires and cyclic variation could be observed. CI-I 
was an organic anti-knock additive and CI-Additional a ferrocene antiknock with 
potassium spark aider. Although CI-Additional has very good anti-knocking 
properties, it is often also used in power generation and naval applications where it is 
used as an anti-soot agent [254]. Due to high treat rate of CI-Additional (resulting from 
high base dilution), CI-Additional was only tested at 1X levels while CI-A and CI-I 
were additionally analysed at 10X.