OldExam2SolnSP2008

# OldExam2SolnSP2008 - SDldJo~ L ej M E 525 E xam#2 April 8...

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SDldJo·~ Lej , ME 525 Exam #2 April 8, 2008 Prof. Lucht ME 156 7:00-8:30 p.m. EXAM INSTRUCTIONS Write your name on each work sheet. At the end ofthe exam be sure to tum in all your work pages, and staple any extra work sheets to the work sheets provided. This exam is closed book and closed notes. When working the problem, list all assun1ptions, and begin with the basic equations. Problem #1 /30 Problem #2 /30 Problem #3 /30 Problem #4 /10 Total /100

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--- ME 525 Exam #2 9 Apr 2007 1. (30 points) A detonation wave propagates in a tllbe closed at one end. The initial reactants are a mixture of H 2 and 02. The molar ratios for the reactant mixture are 8 kmols of H 2 to 1 knl01 of 02. The reactant pressure is PI = 1 bar and temperature T} = 298 K. The measured temperature of the product gases is T 2 = 2650 K. Assume complete combustion and negligible dissociation. (a) Calculate the velocity UI (m/sec) of the unburned gases with respect to the detonation wave front, the velocity U2 (m/sec) of the burned gases with respect to the detonation wave front, the final density P2 (kg/m 3 ), and the final pressure P 2 (bars) ofthe burned gases. (b) Check your answers to determine how well the momentum conservation and mass conservation equations are satisfied (it will be close but not perfect). _------------:_=-- z:~ -=====:'-"'''.--''--.:. ...-:-:. .:-. ----.--- .. _--------~~~-.,!KM-- _IC,. .,. .---_-_---. . --- --------, tA 7- ~ L2 -;:::. J ¥ 'L ~2-_T L ~ ~(L. + Z. !I-z- () 6 1-1 L 1- o f- 1- 0 s-o f<- ' C PI /-\ Z-O - ~Lt,c;Lf 1I- I-I( 1\ l~ /.r -::: -+ t S) ~ 1 q ILjI~o I

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00 \ ! F~ . I , i.___-- fL ~ , PL~· P\ + fl ltt I'L -::: 207'6 Y ! () (;, ~ P L -r- f2-U;;-~ _ £,'15K(06 Jim'?
ME 525 Exam #2 9 Apr 2007 2. (30 points) The table below lists flame properties calculated using the CHEMKIN PREMIX code for a bllmer-stabilized H2-air flame. The flame temperature (K) and the mole fractions of H2, 02, H 2 0, and N 2 are listed as a function of distance z (in cm) from the burner surface. The mole fractions of all other species in the flame gases total less than 1% and can be neglected in calculating MW mix The pressure of 1 atm is uniform throughout the flowfield. Assume that the multi-component diffusion coefficient !i>i,mix for a species i in the mixture is approximately equal to the binary diffusion coefficient for species i and N2, !i>i,N2. Use the Chapnlan-Enskog formula and the Lennard-Jones parameters, both given in the equation sheets, to calculate tIle binary diffusion coefficients. The atomic hydrogen (H) mole fraction profile and the polynomial fit to the data are shown in the plot on the next page. (a)

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OldExam2SolnSP2008 - SDldJo~ L ej M E 525 E xam#2 April 8...

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