Emission and Heat Release Characterization of Propane/Syngas Mixture Diffusion Flame Under Oxygen-Enhanced Combustion and Preheated-Air Combustion Conditions

ABSTRACT

In this study, the emission and heat release characterization of propane/syngas opposed jet diffusion flame under oxygen-enhanced and preheated-air combustion conditions was conducted. The impacts of different operating conditions were examined, namely, the fuel mixture composition, where the propane mole fraction was varied from 0.3 to 0.7, while syngas was assumed as an equimolar mixture of hydrogen and carbon monoxide. The oxidizer was assumed to be an enriched air where the oxygen mole fraction was varied from 0.21 to 0.3. The oxidizer injection temperature was varied from 300 K to 500 K; in contrast, the fuel injection temperature was kept constant and equal to 300 K. The injection velocity of both fuel and the oxidizer is equal and varied from ignition to extinction in terms of strain rate. Finally, the pressure is constant and equal to 1 atm. The combustion chemical kinetics mechanism USC II for H2/CO/C1-C4 coupled with the Gri 2.11 N-sub mechanism was adopted. It is found that increasing syngas mole fraction in the fuel mixture enhances flame temperature, extends the flammability limits, promotes heat release rate, reduces CO/CO₂ emission, and increases NO emissions through the thermal route nevertheless, the prompt route remained the dominant NO production route. Moreover, it was noted that under the oxygen-enhanced combustion condition, CO/CO₂ emission increases, the heat release rate experiences an increase, and the flame temperature is significantly enhanced hence a considerable increase in NO emission through the thermal route, which evolves to be the dominant NO production route. Furthermore, it was remarked that under the preheated-air combustion condition, the flame temperature experiences a considerable increase; consequently, the CO emission increases due to CO₂ disposition thus, its reduction, and the NO emission slightly increases through the thermal route, which becomes the dominant NO production route in the syngas-rich mixture, in contrast, the heat release rate decreases.

KEYWORDS:

• Preheated combustion
• enhanced syngas
• extinction limits
• NO production routes
• oxygen-enriched combustion

Disclosure statement

No potential conflict of interest was reported by the author(s).