1 / 6

MAE 5310: COMBUSTION FUNDAMENTALS

MAE 5310: COMBUSTION FUNDAMENTALS. Adiabatic Combustion Equilibrium Examples September 19, 2012 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk. ADIABATIC COMBUSTION EQUILIBRIUM. Previously we have considered:

bradley-mcpherson
Télécharger la présentation

MAE 5310: COMBUSTION FUNDAMENTALS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MAE 5310: COMBUSTION FUNDAMENTALS Adiabatic Combustion Equilibrium Examples September 19, 2012 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk

  2. ADIABATIC COMBUSTION EQUILIBRIUM • Previously we have considered: • Known Stoichiometry + 1st Law (Energy Balance) → Adiabatic Flame Temperature • Problems 1-4 • Known P and T + 2nd Law (Equilibrium Relations) → Stoichiometry • Problems 5-9 • Now we can combine these: • 1st Law (Energy Balance) + 2nd Law (Equilibrium Relations) → Adiabatic Flame Temperature + Stoichiometry • Problems 10-14 • Solution Scheme • Guess a T=Tguess • Do equilibrium calculation to solve for species concentrations at Tguess • Plug into 1st Law • We want F(Tguess)=0 • If F(Tguess) > 0, then initial guess was too high • If F(Tguess) < 0, then initial guess was too low • Increment Tguess

  3. PRACTICAL APPLICATION: RECUPERATION • A recuperator is a heat exchanger in which energy from a steady flow of hot combustion products, called flue gases, is transferred to the air supplied to the combustion process

  4. SOME COMMON TYPES OF RECUPERATORShttp://www.hardtech.es/hgg_tt_hrt.0.html Tubes cage radiation recuperator Tubes cage radiation recuperator working at 1,200ºC Double shell radiation recuperator Installation consisting of a tubes cage recuperator and a double shell one, series-connected

  5. EXAMPLE: RECUPERATION (TURNS) A recuperator, as shown in figure, is employed in a natural-gas-fired heating-treating furnace. The furnace operates at atmospheric pressure with an equivalence ratio of 0.9. The fuel gas enters the burner at 298 K, while the air is pre-heated. • Determine the effect of air preheat on the adiabatic flame temperature of the flame zone for a range of inlet air temperatures from 298 K to 1,000 K. • What fuel savings result from preheating the air from 298 K to 600 K? Assume that temperature of flue gases at furnace exit, prior to entering recuperator, is 1700 K, both with and without preheat. Radiant-tube burner with coupled Recuperator for indirect firing. Note that All flue gases pass through the recuperator Source: Turns, An Introduction to Combustion

  6. NASA CEA PRACTICE PROBLEM Consider combustion of a methane-air mixture at 10 atm (both fuel and air are at 10 atm). • Plot mole fractions, ci, for the species CO2, CO, H2O, H2, OH, O2, N2, NO vs. temperature for f=1 for a temperature range from 1000 to 2500 K. • Calculate Tflame and mole fractions as a function of f for adiabatic combustion. Plot these results vs. f and discuss at what value the peak flame temperature occurs. Comment on this value in light of the discussion found in Chapter 1, Part 2 of Glassman. • Compare Tflame from part (2) to what would be obtained assuming complete oxidation (burning in only oxygen) and what would be obtained assuming complete combustion (burning in air).

More Related