Laminar flame speed and markstein length characterisation of steelworks gas blends

An outwardly propagating spherical flame configuration has been used to characterise the combustion of different blended steelworks gas compositions, under atmospheric ambient conditions. A nonlinear extrapolative technique was used to obtain values of laminar burning speed and Markstein length for combustion with air and change in equivalence ratio. Peak burning speed was shown to reach almost 1 m s−1 for the combustion of coke oven gas under marginally rich conditions, and the influence of flame stretch on burning speed also shown to increase with equivalence ratio. The molar fraction of coke oven gas (COG) was then blended in the range 0-15% with four blast furnace gas mixtures (BFG) containing 1-7% H2 fractions, representative of the inherent compositional fluctuation experienced in production. Profiles for change in burning speed resulting from this addition of COG are presented, and the dampening extent of fluctuation resulting from the H2 variation has been quantified. Results are also presented for the relative change in gross calorific value and corresponding Wobbe index of the variable blended gases across the tested limits. Modelled results were generated using the PREMIX coded CHEMKIN-PRO, and the performance of specified chemical reaction mechanisms evaluated relative to the experimental data.