Burning of metals in nearly pure oxygen

The extent of this impurity effect is surprising and is worthy of examination. Consideration of Eq. (6.111) readily shows [23] for heterogeneous oxidation that there is no apparent gas-phase reaction. This equation is now written in the form 

One can see that ks is a form of a Damkohler number [ks/(DJrs) which indicates the ratio of the kinetic rate to the diffusion rate. 

Knowing Yoy and k,., one can iteratively determine m0 from Eq. (9.37) and knowing m0 one can determine the metal burning rate from mf = imQ. The surface oxidizer concentration is given by 

The next consideration is how small amounts of inert affect the burning rate. Thus, Eq. (9.37) is considered in the limit YaVj — 1. In this limit, as can be noted from Eq. (9.37), m0 ks. Thus rewriting Eq. (9.37) as 

Two observations can be made regarding Eq. (9.40). First, differentiating Eq. (9.40) with respect to the oxygen mass fraction, one obtains 

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