Abstract
The behavior of the pollutants NO and CO at elevated combustor pressure are of special importance due to the continuing trend toward developing engines operating at higher pressure ratios to yield higher thermal efficiency. An experiment was performed to examine the NO and CO emissions for a swirl convergent-divergent nozzle at elevated pressure. The NO and CO correlations were obtained. Meanwhile, the flame length, exhaust gas oxygen concentration, exit temperature and global flame residence time were also determined to analyze the NO and CO emission characteristics. The results showed that, with the increase in combustor pressure P, flame length decreased proportionally to P−0.49; exit O2 volume fraction increased and exit temperature was reduced. The global flame residence time decreased proportionally to P−0.43. As pressure increased, The NO and Emission Index of NO (EINO) levels decreased proportionally to P−0.53 and P−0.6 respectively, which is mainly attributed to the influence of global flame residence time; the NO and EINO increased almost proportionally with the increase in global flame residence time. The EINO scaling EINO (ρue/d) was proportional to Fr0.42, which indicated that compared with pure fuel, the fuel diluted with primary air can cause a decrease in the exponent of the Fr power function. At higher pressure, the CO and Emission Index of CO (EICO) decreased proportionally to P−0.35 and P−0.4, respectively, due to the increased unburned methane and high pressure which accelerated chemical reaction kinetics to promote the conversion of CO to CO2.
Highlights
Pollutant emissions from the combustion of fossil fuels have become great public concern due to their harmful effects on human health and the environment [1]
P−0.53 and P−0.6 respectively, which is mainly attributed to the influence of global flame residence time; the NO and Emission Index of NO (EINO) increased almost proportionally with the increase in global flame residence time
The CO and Emission Index of CO (EICO) decreased proportionally to P−0.35 and P−0.4, respectively, due to the increased unburned methane and high pressure which accelerated chemical reaction kinetics to promote the conversion of CO to CO2
Summary
Pollutant emissions from the combustion of fossil fuels have become great public concern due to their harmful effects on human health and the environment [1]. The principal pollutants generated by gas turbines are NO and CO, and both emissions have drawn considerable academic interest, in their formation mechanisms and influencing factors. Concerning CO, it arises mainly from incomplete combustion of the fuel, due to inadequate reaction rates in the flame zone caused by very low equivalence ratio and/or insufficient residence time. The factors influencing both NO and CO emissions, e.g., equivalence ratio, flow velocity, fuel property, variable geometry, ambient air temperature have been investigated widely, as mentioned in [3]
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