Numerical study on laminar flame speed of natural gas-carbon monoxide-air mixtures

Laminar flame speeds of natural gas-carbon monoxide-air mixtures are calculated by CHEMKIN II with GRI Mech-3.0 over a large range of fuel compositions, equivalence ratios, and initial temperatures. The calculated results of natural gas are compared with previous experimental results that show a good agreement. The calculated laminar flame speeds of natural gas-carbon monoxide-air mixtures show a nonmonotonic increasing trend with volumetric fraction of carbon monoxide and an increasing trend with the increase of initial temperature of mixtures. The maximum laminar flame speed of certain fuel blend reaches its biggest value when there is 92% volumetric fraction of carbon monoxide in fuel at different initial temperatures. Five stoichiometric natural gas-carbon monoxide-air mixtures are selected to study the detailed chemical structure of natural gas-carbon monoxide-air mixtures. The results show that at stoichiometric condition, the fuel blend with 80% volumetric fraction of carbon monoxide has the biggest laminar flame speed, and the C normalized total production rate of methane with 80% volumetric fraction of carbon monoxide is the largest of the five stoichiometric mixtures. © 2010 Higher Education Press and Springer-Verlag Berlin Heidelberg.