Flame fluctuations in Oxy-CO2-methane mixtures in swirl assisted distributed combustion

Ahmed E.E. Khalil and Ashwani K. Gupta

Applied Energy, 2017, vol. 204, issue C, 303-317

Abstract: Swirl assisted oxy-methane combustion investigated here has focused on the impact of carbon dioxide dilution. Carbon dioxide dilution is essential as it lowers the flame adiabatic temperature and flame speed of oxy-fuel combustion leading to a more stable operation. However, carbon dioxide dilution may result in flame fluctuations, under fuel lean conditions. Experiments using a swirl burner examined the flame fluctuations with different amounts of CO2 dilution, with the goal to achieve stable oxy-CO2-methane combustion via colorless distributed combustion (CDC). This novel CDC technique has shown significant performance gains in gaseous fuel-air flames on emission reduction, enhanced thermal field uniformity, noise reduction, and improved flame stability. Results have shown that for oxy-CO2-fuel combustion, most of the heat release fluctuations had frequencies below 60Hz. The results obtained revealed that increase in CO2 dilution increased the magnitude of flame fluctuation till a maximum of 28% O2 concentration in the oxidizer. Further increase in dilution gases and reduction in O2 concentration led to a more stable flame, along with more favorable conditions for colorless distributed combustion. Data analysis of flame images revealed the source of oscillations under different conditions. At maximum fluctuations with 28% O2, the flame oscillated between two modes leading to unstable operation and large fluctuation in the heat release signal. Decrease in oxygen concentration to below 27%, promoted a more stable flame behavior, occupying a larger flame volume, which is characteristic of distributed combustion. Further reduction in O2 led to flame blow off at around 21% O2. This work outlines the importance CO2 dilution in oxy-fuel flames for achieving stable distributed combustion and mitigate the increased oscillations normally encountered in higher oxygen concentration flames.

Keywords: Oxy-fuel combustion; Flame stability; Heat release fluctuations; Flame visible signature; Colorless distributed combustion; Gas turbine combustion (search for similar items in EconPapers)
Date: 2017
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Citations: View citations in EconPapers (13)

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DOI: 10.1016/j.apenergy.2017.07.037

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