Exam2SolnPCME525SP2011

Exam2SolnPCME525SP2011 - M E 525 E xam #2 7 April 2011 Name...

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------------------------- -------- 20 ME 525 Exam #2 7 April 2011 Name 1. The diagrams below pertain to premixed detonations and premixed flames. (a) (10 points) In the diagram below, the ZND structure of a detonation wave is plotted. The three unlabeled curves are the normalized density ~,pressure P , and temperature PI ~ T Label the three curves correctly and justify (briefly) your answers. Hint: If you T; have trouble with this solve problem #3 and then come back to this problem. - - - *"*- . ... - - - - 10 ~ I I 1 I J.------. I I I ~----------~ t I _____________ I ,~_~ I'" ...... I I 1...,. .. __ ~ " I I I 1 l' 1" 2 Comment: P = pRT therefore pressure increases is largest across normal shock, temperature must increase as reactions occur. Also plot is consistent with results of problem #3. In the reference frame attached to the detonation wave, indicate whether the Mach numbers at locations 1, 1', 1", and 2 are equal to 1, less than 1, or greater than 1.
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M 2 =1 1': after normal shock 1'-1 ": induction zone 1 "-2: reaction zone 2: postflame region
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(b) (6 points) In the diagram below, the results of a numerical calculation of the structure of a premixed CH4/air flame (low-speed deflagration) with an equivalence ratio of 1.0 are plotted as a function of axial distance from the burner surface. The three unlabeled curves are the mole fractions of CO, C02, and CH4, all multiplied by 10. Label the three curves correctly and justify (briefly) your answers. 2500 1.0 T 80.8 • . ..-4 '0 ~0.6 <1.) ..... -I ~O.4 0.2. ..-_ °o~~~~~~--~--~--~~O 0.5 1.5 2.0 2.5 3.0 Axial distance (mm) CH4 is fuel species, decreases to zero, CO is intermediate species in hydrocarbon combustion, postflame [C02] will be greater than [CO] for stoich··~lbustion.
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(c) (4 points) In the diagram below, the results ofa numerical calculation ofthe structure of a premixed CH,Jair flame (low-speed deflagration) with an equivalence ratio of 1.0 are plotted as a function ofaxial distance from the burner surface. The two unlabeled curves are the mole fractions of CH and NO. One curve is multiplied by 10 6 and one is multiplied by 10 4 LabeWh. .e curves and justify (briefly) your answers. (£fv 2500 2000~ ~ 1500 ~ e GJ 1000 ~ ~ 500 0 CD is radical species present only in flame zone, NO is produced in flame zone by prompt mechanism and in postflame zone by Zeldovich mechanism. \ 5 E:Jx 10 6 4 3 2 o r...-. ___. ........... _________ -.a. .._---'-. ..... 3.0 o 0.5 1.0 1.5 2.0 2.5 Axial distance (mm) + I J
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ME 525 Exam #2 7 April 2011 Name ___________ 2. (40 points) The table below lists flame properties calculated using the CHEMKIN PREMIX code for a burner-stabilized H2-air flame. The flame temperature (K) and the mole fractions of H2, 02, H20, and N2 are listed as a function of distance z (in cm) from the burner surface.
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Exam2SolnPCME525SP2011 - M E 525 E xam #2 7 April 2011 Name...

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