Turbulent Consumption Speed Scaling of H₂/CO Blends

This paper describes measurements and analysis of global turbulent consumption speeds, S_T,GC, of hydrogen/carbon monoxide (H₂/CO) mixtures. The turbulent flame properties of such mixtures are of fundamental interest because of their strong stretch sensitivity and of practical interest since they are the primary constituents of syngas fuels. Data are analyzed at mean flow velocities and turbulence intensities of 4 < U₀ < 50 m/s and 1 < $u′rms$/S_L,0 < 100, respectively, for H₂/CO blends ranging from 30–90% H₂ by volume. Data from two sets of experiments are reported. In the first, fuel blends ranging from 30–90% H₂ and mixture equivalence ratio, Φ, were adjusted at each fuel composition to have nominally the same un-stretched laminar flame speed, S_L,0. In the second set, equivalence ratios were varied at constant H₂ levels. The data clearly corroborate results from other studies that show significant sensitivity of S_T,GC to fuel composition. For example, at a fixed $u′rms$⁠, S_T,GC of a 90% H₂ case (at Φ = 0.48) is a factor of three times larger than the baseline Φ = 0.9, CH₄/air mixture that has the same S_L,0 value. We also describe physics-based correlations of these data, using leading points concepts and detailed kinetic calculations of their stretch sensitivities. These results are used to develop an inequality for negative Markstein length flames that bounds the turbulent flame speed data and show that the data can be collapsed using the maximum stretched laminar flame speed, S_L,max, rather than S_L,0.