Oxygen enrichment and its temperature effects on the diffusion flame characteristics of propane- syngas mixture

Abstract

The present work aims to highlight the role of combustion in the energy transition process, emphasizing the role of alternative fuels and combustion technologies in emissions control and efficiency improvements from this perspective, the emissions and heat release characteristics of the opposed jet diffusion flame of the alternative fuel mixture propane / syngas were simulated under the conditions of the combustion technologies oxygen enhanced combustion and preheated air combustion. Various parameters were analyzed, including the fuel mixture composition, where equimolar syngas enrichment was applied from 30% to 60% per volume, oxygen enrichment was applied from 21% to 30%, air preheating was applied at each oxygen enrichment level from 300 ºC to 500 ºC, the fuel injection temperature was maintained at 300 K. Both fuel and oxidizer injection velocities were equal and varied through the flammability limits as a function of the strain rate, with the pressure held constant at 1 atm. The coupled chemical kinetics mechanism USC Mech II-Gri 2.11 N-sub mechanism was used. Results showed that syngas enrichment elevated flame temperature, extended flammability limits, increased the heat release rate, reduced the CO/CO2 emissions, and raised NO emissions via the thermal route, though the prompt path remained the dominant NO production pathway. Additionally, oxygen enrichment increases the CO/CO2 emissions, the heat release rate, and the flame temperature significantly, leading to a substantial rise in NO emissions via the thermal route, which became the dominant NO production pathway. Furthermore, when air preheating is applied, a notable increase in flame temperature is observed, resulting in higher CO emissions due to CO2 dissociation. Consequently, CO2 emissions decreased while NO emissions slightly increased via the thermal pathway, becoming the dominant NO production pathway in syngas rich flames. However, the heat release rate decreased.