Study on laminar burning velocity of syngas-air premixed flames in various mixing conditions

Abstract

The laminar burning velocity of syngas-air premixed flames was measured with various equivalence ratios from 0.5 to 5.0 and a mole fraction of H2 from 0.05 to 0.75. The laminar burning velocity was experimentally determined using a Bunsen flame according to the cone angle and surface area methods. A premixed code with a USC-II detailed reaction mechanism was used for the numerical calculations to predict the laminar burning velocity and to examine the relationship between the burning velocity enhancement and the hydrogen- related reactions. The results indicate that an appropriate method for the measurement of laminar burning velocity is necessary in the H2/CO/air syngas premixed flame. In addition, the burning velocity linearly increased with the increase of the H2 mole fraction in the syngas mixture, although the burning velocity of H2 was 10 times larger than that of CO. This result is attributed to the rapid production of H-radicals at the early stage of combustion. Furthermore, the predicted mole fractions of H and OH radicals increased with the increase of H2 mole fraction for a lean syngas mixture. However, the mole fraction of OH radicals, an indicator of heat release rate, decreased for rich syngas mixture, resulting in a reduction of the laminar burning velocity, even with an increase of the H2 mole fraction.