Effect of Gasoline Fuel Additives on Combustion and Engine Performance

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6.4 Experimental Error Assessment for Combustion 
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Figure 6.36: Time of peak pressure CI-Additional 
6.4
 
Experimental Error Assessment for Combustion
Similarly to droplet sizing experiments, standard deviation around the 
measured mean value for a specific characteristic was used to identify any significant 
additive effects. Gasoline vapour combustion study was carried out on a 5 event 
average. Initial base fuel analysis showed that mixture preparation to within 1.3 % of 
measured fuel equivalence ratio could be achieved, while the peak pressure variability 
was within 2 % of the mean value over the same number of combustion event. This 
variability was shown to be larger at the final results analysis stage, where peak 
pressure variability throughout the base fuel tests was seen to be 4.8 %. Similar 
variability values were found for initial temperature and pressure conditions. Peak 
HRR was seen to exhibit a standard deviation of 16.3 % while flame speed 
measurements had a variability of 11.3 %. It can be seen from Sectimeant the additive bearing fuel characteristics were within these variability limits and 
as such no effect from the additives beyond the experimental error could be identified. 
The variability in emissions characteristics was 16.4 % for CO, 20.6 % for NO
x
and 
3.2 % for CO
2
. The maximum reduction in the CO emissions from the additive study 
was 37.7 % which was found to be the only measured parameter from the gasoline 
vapour combustion experiments to exhibit characteristics beyond experimental 
variability.
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