Problem Set #1: Conservation Equations & Control Volumes

Project III
Premixed Flames
OBJECTIVE: Use the Chemkin and Gaseq software to study premixed
methane/hydrogen-air combustion waves.
Determine and discuss the flame structure for a methane-air flame at
300K, 1 atm.
Examine the flame “structure” and discuss the accuracy of the two zone
structure assumed in the flame speed derivation in class. Also, discuss
the other assumptions made in the class derivation in light of the
computed results.
Determine the dependence of the flame speed, flame thickness, and
ratio of reaction zone to preheat zone thickness upon H2/CH4 ratio
ranging from pure H2 to pure CH4. Fix the same adiabatic flame
temperature as in (1); i.e., you will need to run each case at a different
stoichiometry to fix flame temperature. Analyze the results and suggest
the mechanism(s) and key physics controlling these results.
Using the GasEQ software, determine the corresponding C-J
detonation wave speed for the same parameter set. Discuss the results
and compare and contrast the dependence of the wave pressure ratio
upon the varied parameter.
Extra Credit (up to +10 pts):
1) It is often of interest to obtain some quantitative assessment of the rate of heat
release at a certain point in a flow field. However, the rate of heat release is
difficult to measure directly. Based on the above results, is it possible to
estimate (quantitatively) the rate of heat release by measuring the concentrations
of certain radicals (e.g., can the rate of heat release be related to the CH
concentration)? If so, which radicals serve as the best markers of heat release?
You will need to use the Chemkin software package for these calculations. PREMIX
models a one-dimensional premixed flame. The Chemkin software is available in the AE
Computer Lab (Knight 3rd floor). Every on-campus student in class has an account on
these networked computers; instructions for logging in are posted on the computer
room door. The room is unlocked during the day. Your buzz card should give you
access to the building and the computer room at other times. Please note that you only
have write access to your own folder. So you will need to set your working directory to
some subfolder of your own user folder.