The current paper describes the effects
of oxygen enrichment on
flame stability and pollutant emissions for turbulent non-premixed
swirling flames. The study is motivated by CO2 capture
applications further to the increase of the CO2 concentration
by the O2 addition. The burner configuration consists of
two concentric tubes with a swirl placed in the annular part for air
or oxygen–air. The exhaust gas compositions are measured using
gas analyzers. OH chemiluminescence experiments are conducted to investigate
the stability of flames. The measurements were performed for oxygen
concentrations ranging from 21 to 30% by volume, with swirl numbers
of 0.8 and 1.4 and global equivalence ratios of 0.8, 0.9 and 1. Results
show that oxygen enrichment enhances combustion efficiency and flame
stability. The increase of the oxygen concentration in air leads to
a decrease of lift-off heights and fluctuations of the flame base.
Increasing the swirl number significantly improves the flame stability.
Experiments demonstrated that the CO2 emissions linearly
increase with an increasing O2 content in the oxidant.
The CO emissions are shown to decay exponentially, whereas the NO
x
emissions, mainly produced through the thermal
pathway, increased exponentially with oxygen addition.
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