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mech6120-final-rev

# mech6120-final-rev - MECH 6120 Combustion Final Exam Review...

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MECH 6120: Combustion Final Exam Review Questions The test will be in a multiple choice/short answer format. You may bring four pages (front and back) of notes in your own handwriting; otherwise the exam is closed book. Note that this contradicts what I said in class on Thursday. I will provide selected formulas and property data for use in the questions. 1 Thermochemistry 1. Be able to determine, by balancing the reaction, the stoichiometric coefficient a in C x H y O z + a O 2 -→ products 2. Given a lower heating value for the fuel, a specific heat of the product mixture, and the temperatures of the reactants and the products, be able to determine the heat transfer (per kg of fuel or per kg of reactants) from the system. 3. Methane is burned with air at 1 atm and an equivalence ratio of Φ. The equivalence ratio must be set so that the dew point temperature of the products is T dp = 50 C. Given that the saturation pressure of water at 50 C is 12.34 kPa, find the required equivalence ratio. 4. What are the three basic contributions (or parts) to enthalpy? How do we establish a ‘chemical reference state’? 5. Nitric oxide (NO) is in chemical equilibrium with N 2 and O 2 . If the temperature of the system is fixed, and the pressure of the system is doubled, how will the equilibrium mole fraction of the NO change? 6. Repeat the above question, except now with NO 2 in equilibrium with molecular oxygen and nitrogen. 2 Kinetics and Chain Mechanisms 1. Describe the key differences between an overall (or global) reaction and an elementary reaction. 2. Unimolecular, bimolecular, trimolecular reactions: what are they, how do their reaction rates depend on pressure? 3. Consider the following chain for dry CO oxidation: CO + O 2 k 1 -→ CO 2 + O O + O 2 + M k 2 -→ O 3 + M O 3 + CO k 3 -→ CO 2 + O + O O 3 + CO + M k 4 -→ CO 2 + O 2 + M (a) Using the law of mass action, derive equations for the rate of change of CO, O, and O 3 concentra- tion.

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mech6120-final-rev - MECH 6120 Combustion Final Exam Review...

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