|dc.description.abstract||A comprehensive second law analysis of combustion for a range of conditions and fuels
was completed. Constant pressure, constant volume and constant temperature combustion
processes were examined. The parameters studied were reactant temperature, reactant
pressure, equivalence ratio and the fuels themselves. In addition, the contribution and relative
significance of the various components (thermo-mechanical, reactive and diffusion) to the
mixture availability was examined. Also, the effect of reactant mixture dissociation was
incorporated into the combustion analysis.
It was found that for similar initial conditions, constant pressure combustion and constant
volume combustion exhibited similar trends. For constant temperature combustion, the trend is
significantly different from the constant pressure and constant volume combustion, with almost
the entire reactant availability being destroyed due to combustion at lower temperatures.
Amongst the parameters examined, reactant mixture temperature had the most
significant effect on the fraction of availability destroyed during combustion. The percentage
availability destroyed reduced from 25 to 30% at 300 K to about 5% at 6000 K for constant
pressure and constant volume combustion processes.
The effect of the reactant mixture pressure on the fraction of availability destroyed was
more modest. The values for the percentage availability destroyed for pressures ranging from 50
kPa to 5000 kPa were found to lie within a range of 5%.
The effect of equivalence ratio on the fraction of reactant mixture availability destroyed
was also documented. In general, it was found that the destruction of availability decreased with
increasing equivalence ratios. This value, however, accounts for the availability due to fuel like
species in the product mixture. Therefore, for practical applications, combustion of the
stoichiometric mixture would be preferred over the rich equivalence ratios.
It was found that the fraction of reactant availability destroyed increased with increasing
complexity of the fuel??s molecular structure.
In addition, it was shown that the diffusion availability terms is small and may be
neglected, while the reactive availability and thermo-mechanical availability are more significant.||en