Craya-Curtet parameter

Craya and Curtet [4] have used averaged integrated values of Navier-Stokes equation as well as the continuity equation to predict the confined jet behavior. The dimensionless Craya-Curtet parameter m is given by ... 

While this parameter varies between unity and infinity, experience has shown that for short and intense flames encountered in cement kilns, the recirculation is such that the Craya-Curtet parameter M > 2.0. Flames with M between 1 and 2 are characterized as long flames with the intensity suitable for processes such as rotary limestone calcination kilns. For flames with M < 1.0, the entrainment is such that the flame tends to be long and lazy. The Craya-Curtet parameter. 

We have already discussed under practical stoichiometry how the air requirements can be estimated based on the fuel composition (ultimate analysis). The primary and secondary air requirements for combustion of pulverized coal or coke are best estimated by mass and heat balance at the mill. In Appendix 6A we show a calculation taken from Musto (1997) for the primary and secondary air required for coal pulverizer with 4.5 metric ton per hour (10,0(X)lb/hr) coal feed rate at initial moisture of 15 percent which is required to be ground and dried to 2 percent with a 200 HP mill. In order to estimate the actual primary and secondary air, one has to make some estimation of the evaporation rate, the amount of gas entering the coal mill, and the bleed air required so that the quantity of air that should be vented from the hood off-take can be properly estimated. It shows that for a take-off gas temperature of 315°C (600° F) and vent gas temperature of 76°C (170°F) and allowing ambient air infiltration of 10 percent at 15°C (60°F) the primary air will be about 22 percent of stoichiometric air and 21 percent of total air. The remaining air (about 79 percent) will be the secondary air. With this information we can size a burner using a burner pipe diameter based on a Craya-Curtet parameter of choice bearing in mind the conditions that ensure the desired jet recirculation patterns described in Chapter 3. 

When the jet is considered as a point source, at its origin the relationship between Thring-Newby [5] and Craya-Curtet [4] parameters are written ... 

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