Experimental Study of Oxygen Enrichment Effects on Turbulent Non-premixed Swirling Flames

Abstract

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.

A numerical investigation of structure and emissions of oxygen-enriched syngas flame in counter-flow configuration

“…This behavior clearly demonstrates that oxygen enrichment enhances the stability of the syngas flame. These findings are in good agreement with the results of Yepes and Amell AA [13] and Merlo et al [41].…”

“…lean syngas composition). This feature can be profitably exploited in industry to improve CO 2 capture in the flue gas [41].…”

Introductory Chapter: Swirling Flows and Flames

“…Boushaki et al [13] and Nazim et al [41] reported the effect of the swirl number on the NOx and CO emissions. They found that in the case of a swirl number of 1.4, the EICO rate is slightly lower than in the case of a swirl number of 0.8.…”

Simulação numérica de um escoamento turbulento não-reativo no interior de uma caldeira ciclônica industrial usando LES e URANS

“…Concerning swirling effects, some studies pointed out that swirling flows can reduce pollutant emissions, particularly of nitrogen oxides, by improving mixing of reactants and, therefore, decreasing flame temperature (SCHMITTEL et al, 2000;SOLERO;SCRIBANO, 2004;BURGUETTE;COSTA, 2006;COZZI;COGHE, 2012;MERLO et al, 2013;BOUSHAKI et al, 2017).…”

“…From Boushaki et al (2017) and Merlo et al (2013), it was noted that swirl intensity might tend to enhance the mixing and to increase the residence time inside the reaction zone, which promotes the CO conversion to CO 2 . It is also said that increasing the swirl number tends to reduce the NO x formation in particular for oxygen rate up to 27%, which can be an effect of the flame temperature reduction by the swirl.…”