Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 6.5: Relationship between CO emissions and calculated flame speed 
0
100
200
300
400
500
600
700
800
900
1,000
100
110
120
130
140
150
160
170
180
CO
, 
pp
m
Burning Velocity, cm/s
CI-A Base
CI-A 1X
CI-A 10X
CI-I Base
CI-I 1X
CI-I 10X
CI-Additional Base
CI-Additional 1X

---

6.2 Gasoline Vapour Combustion 
143 
CO emissions could also have been reduced by improved reaction rate 
throughout the combustion event which could also explain the increase in burning rate. 
Reduced timescales needed to achieve complete oxidation of hydrocarbons would 
allow for more of the CO to be turned into CO
2
. Although an increase in heat release 
rate would subsequently be expected, as seen in Figure 6.6, the peak heat release rate 
experienced for CI-A 1X was not the highest result recorded. Moreover, it is evident 
that CO emissions in the current study where independent of heat release rate. This 
can be explained by the study of Aradi and Roos [62] , who found that 2-EHN only 
survives at temperatures up to 625 K, which is much lower than the expected flame 
temperatures for the current investigations. Furthermore, Higgins et al. [10] showed 
that high-temperature chemistry of combustion remained unaffected by the additive, 
suggesting reduced flame quenching near the vessel walls to be the more probable 
cause for CO reduction. 
Figure 6.6: Relationship between CO emissions and peak heat release rate 
With decreasing CO levels, a reduction in unburnt hydrocarbon emissions 
would also be expected. However, since unburnt hydrocarbon content in the emissions 
was not measured and at 10X concentration the CI-A additive effect seemed to 
disappear, it is not possible to confirm the theory.
Addition of CI-Additional to the base fuel also produced notable results. 
Lowest burning velocity and peak heat release rate as well as the longest time taken 
to peak heat release rate and peak pressure were observed. Reductions in flame speeds 
0
100
200
300
400
500
600
700
800
900
1,000
1,000
1,050
1,100
1,150
1,200
1,250
1,300
1,350
1,400