Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 4.20: Time series of sample gasoline vapour combustion with initial pressure of 0.7 
bar. Left to right, image processing procedure: raw image; background corrected image; 
binarised image for area based radius calculation; binarised image for circumference based 
radius calculation 

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4.2 Combustion Investigations 
111 
Figure 4.21: Radius change in time for area and circumference based calculation methods. 
Time points t
1-6
 correspond to those shown in Figure 4.20 
Initial base fuel characterisation was carried out under ambient initial pressure 
conditions. Although this was suitable for pressure/heat release rate and flame 
propagation speed analysis, it was found that emissions analysis suffered due to the 
output from mainly the oxygen sensor being flow dependent. It can be observed from 
Figure 4.22 that after a combustion event the pressure dropped very quickly to pre 
combustion levels. This meant that without opening air inlet to the combustion vessel, 
Figure 4.22: Sample pressure and heat release rate traces for gasoline vapour combustion in 
combustion vessel at raised initial pressure and φ = 0.8 
0
10
20
30
40
50
60
70
0
10
20
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70
Ra
diu
s,
 m
m
Time, ms
Circumference based
Area based
-400
-200
0
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1,000
1,200
1,400
0
1
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7
8
9
0
100
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800
H
RR,