Transcript ME 475/675 Introduction to Combustion

ME 475/675 Introduction to
Combustion
Lecture 9
Announcements
• Midterm 1
• September 29, 2014 (two weeks from today)
• HW 3 Ch 2 (57), Due now
• HW 4 Due Monday, September 22, 2014
• Ch 2 (33, 35, 47, 50, 54, 63)
• I’m rethinking the Example/Homework assignments…
Computer Programs Provided by Book Publisher
• Described in Appendix F
• For “complex” reactions (11 product species)
• Fuel: CNHMOLNK
• Oxidizer: Air
• Download from web: www.mhhe.com/turns3e
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student edition
Computer codes
Access to TPEquil, HFFlame, UVFlame
Extract All
• TPEQUIL (TP Equilibrium)
• Use to find
• Equilibrium composition and mixture properties
• Required input
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Fuel CNHMOLNK
Temperature
Pressure
Equivalence ratio (with air)
• to determine initial number of moles of each atom
HPFLAME (HP Flame)
• Use to find
• Adiabatic flame temperature for constant pressure
• Required Input
• Fuel, equivalence ratio, enthalpy of reactants HR, pressure
• For constant pressure: HP = HR
• Find TAd
• In our examples we assume ideal combustion so we knew the product
composition
• But this program calculates the more realistic equilibrium composition of the
products from a (complex) equilibrium calculation (multiple equilibrium
reactions)
• But this requires TProd = TAd, which we are trying to find!
• Requires program (not humans) to iterate
Example 2.8, Page 54
• A recuperator (heat exchanger) is employed in a natural-gas-fired
heat-treating furnace. The furnace operates at atmospheric pressure
with an equivalence ratio of 0.9. The fuel gas enters the burner at
298 K, and the air is preheated.
• (a) Determine the effect of air preheat on the adiabatic temperature of the
flame zone for a range of inlet air temperatures from 298 to 1000 K.
• (b) What fuel savings results from preheating the air from 298 to 600 K?
Assume that the temperature of the flue gases at the furnace exit, prior to
entering the recuperator, is 1700 K, both with and without air preheat.