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HW7 - CHE 633-Combustion Priciples Assignment 7 Due...

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Unformatted text preview: CHE 633--Combustion Priciples Assignment 7 Due Wednesday, March 7, 2012 Problem 1: Derive equation 7.55 in Turns starting from the energy equation given at the end of page 4 of Class 19 notes. Neglect viscous heating, potential energy, and assume steady state. You will need to use the mass conservation equation, and the species conservation equation, and remember how we define species mass flux in terms of the mass average velocity and the diffusion flux. This is all 1-D. Also, recall h=u-P/. Problem 2: List at least 5 of the key assumptions that go into Turns Eq. (7.81). Problem 3: This is a thinking problem. The mixture fraction can be used to express a species composition like CO2 in a steady laminar flame using the equation: This term balances reaction and diffusion (diffusion in the mixture fraction coordinate, where acts like a diffusion coefficient. (a) Sketch the profile of a species like CO2 versus (1) for a nominal st, and (2) for st=0.5. (You have already created profiles like this before). For CO2 it looks like a tent. (b) Based on the shape of these profiles and the equation, which of the two cases would you expect to have a higher when blowout occurs? Turbulence intensity is directly related to so the case with the higher at blowout will be more resistent to blowout and can handle higher mixing rates (actually, is a mixing rate). Higher mixing rates give higher combustion rates give smaller required combustion volumes. (c) Based on the above equation, if the right-hand side is fixed, then if increases, what happens to the shape of the term it multiplies? Sketch the Yi profile qualitatively versus as changes. Problem 4: Turns 8.1 Problem 5: Turns 8.6 Problem 6: Turns 8.9 Problem 7: Turns 8.15 ...
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