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jhapk November 27, 2009 11:59

Flamelet Modelling

I have been trying to simulate a 2D axisymmetric laminar coflow diffusion flame using the flamelet concept. The fuel is 65 % CH4 + 35 % N2 by volume and oxidizer is air. I am generating a Flamelet library using counterflow flame solutions for different strain rates by Cantera. I have the following questions:

Notation used:
Z = mixture fraction
X = scalar dissipation
1) Cantera gives me solutions for X rates varying from 0.15 to 18.0. But in my 2D flow domain, I get X values as high as 500. What should I do when my X > 18.0? I have tried using a coldflow solution for all values of X> 18.0 but I am getting non-physical states in my 2D flame in cells where X<18.0 and X>18.0 are next to each other

Coldflow solution:
\phi = Z*\phi_fuel_feed + (1-Z)*\phi_oxidizer_feed
\phi is any physical quantity and \phi_fuel_feed is the value of \phi in fuel feed and \phi_oxidizer_feed is the value in oxidizer feed.

2) Most of the literature I have read give a mapping function to convert strain rate into charactersitic scalar dissipation rate value for a particular counterflow solution using an inverse error function. Why can't I simply calculate scalar dissipation using X = 2*D_z* (dz/dx)(dz/dx) for the 1D counterflow flame?

Any insights will be very helpful.

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