Radiation effects of CO2 and H2O dilution on laminar flame speeds of syngas flames under elevated pressures

Abstract

The abundant CO2 and H2O in circulating flue gases both chemically affect the combustion characteristics significantly. Meanwhile, the intense radiation effects induced by CO2 and H2O also strongly coupled with chemical reactions by preheat unburned fuels. Thus, the comparison and analysis of dilution effect and interaction mechanism with CO2 and H2O blending is of great significance, especially when considering radiation reabsorption. In this study, laminar flame speeds of premixed syngas flames considering radiation reabsorption were simulated under elevated pressures. It found that radiation reabsorption effect induced by CO2 and H2O dilution both greatly increased the flame speed of syngas flames. Because of the discrepancy in dominant influence mechanisms of radiation reabsorption, different relative enhancements of flame speed as a function of pressure were observed. Moreover, the co-dilution of CO2 and H2O further improved the radiation reabsorption effect by means of the coupling inhibition of OH radical's consumption pathway.