Previous work conducted by the authors showed that for a stoichiometric inlet fuel-oxidizer ratio at 1 atm and 1200 K, an optimal range of exergetic efficiency exists for H2 combustion when singlet oxygen composes 0–20% of the oxidizer; with the maximum occurring at approximately 10%. Additionally, in the optimal range, 60% of the total exergy destruction occurs before ignition. These results provide encouraging evidence that it is possible to improve the exergetic efficiency of combustion inherently and thereby reduce fuel usage for a desired energy transfer. The focus of this study is to determine if the exergetic efficiency of combustion can be further optimized by varying other combustion parameters in addition to the inlet concentration of singlet oxygen.
The chemical kinetics simulation was accomplished by developing an adiabatic plug flow reactor model in CHEMKIN-PRO® and employing the Moscow State University H2-O2 mechanism. The ranges of parameters considered were: equivalence ratio 0.7–1.3, inlet temperature 1100–1300 K, inlet concentration of singlet oxygen 0–20%, and diluent type (Ar, N2, no dilution). Pressure was held fixed at 1 atm. The calculated quantities were: exergetic efficiency, exergy destruction before ignition, molar conversion of H2, exit temperature, ignition temperature, and ignition distance.
Results of the study show that over the optimum range the maximum exergetic efficiency occurs for an equivalence ratio of 1.3, with no dilution at 1300 K. Furthermore, the data show that for 20% inlet singlet oxygen there is significant variability in exergy destruction before ignition, ignition temperature, and ignition distance. Understanding how varying traditional combustion parameters impacts the enhancing effect that singlet oxygen has on the exergetic efficiency of H2 combustion provides a framework for directing future research efforts for hydrocarbon combustion under a broader range of operating conditions of practical engineering interest.