OCR Text |
Show can be obtained, where Cg=2.86, Cd=2.0, k and s are the kinetic energy of turbulence and its dissipation rate, respectively, and LI, is the turbulent diffusion coefficient (eddy viscosity). Alternately, an empirical relation between the variance and the m e a n value of temperature can be used, v*=Sdv(-v), (11) where So is an empirical parameter (termed as the turbulent intensity parameter). The AL model uses Eq. (10) in the results presented below. EXPERIMENTAL DATA Reference [1] reports results obtained from firing different momentum, pipe-in-pipe oxy-fuel burners in two operating conditions. Thus, three different natural gas-oxygen burners are fired at a rate of 1 M W in a water-cooled furnace, and at 0.8 M W in a refractory-lined furnace. Table 1 presents the natural gas and oxygen velocities for each case investigated. The first letter in the "IFRF Flames" column represents the burner momentum. Thus, A is a high-momentum burner, B is a medium-momentum, and C is a low-momentum burner. The burners are fired in two different conditions, specified by the second letter in Table 1. Thus, case C refers to a water-cooled furnace, characterised by low furnace temperatures (TWaii=400°C), while case R refers to a refractory-lined furnace, characterised by hot furnace temperatures (Twaii,maxz 1600°C). Reference [1] reports extensive experimental results, including specie and temperature measurements, both in the flame and in the flue gases. Table 2 presents the flue gas temperature, as well as N O concentration at the outlet. The results in Table 2 suggest that momentum plays an important role in the 10 |