Experimental Study on the Effect of Swirling Flow and Oxidizer Type on the Stability, Light Emission, and Pollutant Emissions of Non-Premixed Propane Flames

This experimental study examines the effects of swirling oxidizer flow and oxidizer type (air vs. oxygen) on non-premixed propane flames in a vane-type swirl burner. Using swirler angles of 30°, 45°, and 60°, we investigated flame stability limits, light emission via a Lux meter, temperature distribution, and pollutant emissions (CO, CxHy, NOx) at varied oxidizer flow rates. Increasing the swirl angle enhances air flame stability, expanding the stable operating range against lift-off. Oxygen flames exhibited exceptional stability, with no instabilities observed within the tested range. Light emission, measured by a Lux meter, correlated positively with temperature and was significantly higher with oxygen, reflecting higher temperatures and altered luminous species. Swirl improved mixing, reducing CO and CxHy emissions with air, but oxygen combustion increased NOx due to elevated temperatures and potential nitrogen ingress. Higher swirl angles mitigated NOx in oxygen cases. These findings underscore the critical role of swirl and oxidizer type in optimizing flame stability, efficiency, and emissions in combustion systems.