Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Table 5.1: Additives and treat rates as used in droplet sizing experiments 

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5.1 Gasoline Spray Investigations with Additives 
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composition of the additives. However, it is known that all additives were of ashless 
type, meaning no metals were present in the chemical composition and that friction 
modifier FM-O was a chemically reactive acidic compound while FM-A and FM-N 
worked on the physical absorption principle. Combustion improver CI-I is known to 
be an organic anti-knock compound. 
The additive composition in fuel mixture is called the treat rate. In present 
study, the fuels were treated with commercially employed quantities of additive (1X) 
and at ten times the amount (10X). It can be seen that the treat rates for the anti-static 
additive and drag reducing agents are low compared to other type of additives. Highest 
treat rates used were for combustion improvers. All experimental work on additives 
included a base fuel comparison to additive bearing fuel at 1X and 10X treat rates.
5.1.2
 
Experimental Protocol 
Experiments were carried out on base gasoline fuel without an additive which 
was compared against an additive bearing base fuel with a selection of additives. 
Experimental protocol followed for the additive tests was the same as described in 
Section 4.1. SMD measurements were taken at instants of minimum and 50 % 
transmission (end of spray) values for injection pressures of 50-110 bar in 10 bar 
intervals. 50 repeat injections were carried out per condition. 
Base fuel tests were carried out between each additive. This allowed for 
detection of any drift in SMD values that could occur but also enabled calculation of 
overall test-to-test variation. Base test after an additive was used as the base before the 
next additive. Overall, nineteen base tests were carried out, the standard deviation of 
which was used to represent repeatability of the measurements. Any additive results 
that lied outside the standard deviation were considered to be significant.
Each new fuel was injected into the combustion chamber for at least 50 times 
to clear the injector nozzle of any residue from precious fuels, should there still be any 
present. Cleaning of the whole fuel system was carried out between each fuel/additive 
in an ultrasonic bath.