Loading presentation...

Present Remotely

Send the link below via email or IM

Copy

Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.

DeleteCancel

Make your likes visible on Facebook?

Connect your Facebook account to Prezi and let your likes appear on your timeline.
You can change this under Settings & Account at any time.

No, thanks

COMBUSTION

No description
by

Feyza Kazanç

on 4 November 2014

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of COMBUSTION

Fuel+Air Products
COMBUSTION

ME 405, ENERGY CONVERSION SYSTEMS
FALL 2015, FEYZA KAZANÇ

Stoichiometric Oxygen
Chemical formula of a fuel
Oxygen requirements for the combustion
- Stoichiometric
- Fuel Lean
- Fuel Rich
COMBUSTION and Thermochemistry
Heating Value
- HHV (Higher Heating Value)
- LHV (Lower Heating Value)
Adiabatic Combustion Temperature
Chemical formula of a fuel:
CvHwSxOyNz
Element/Atoms Molar Mass (kg/kmol)
Carbon (C) 12.0112
Hydrogen (H) 1.0080
Nitrogen (N) 14.0067
Oxygen (O) 15.9994
Sulfur (S) 32.0460
1 mol of a compound corresponds to 6.022*10^23 molecules
What are the stoichiometric numbers of v, w, x, y, and z???
What is the molecular weight of the compound???
Minimum Oxygen needed???
k=v+w/4+z+x-y/2
if more than a stoich. quantity of oxidizer supplied
Fuel Lean
if less than a stoich. quantity of oxidizer supplied
Fuel Rich
stoichiometric air-fuel ratio:
(A/F)stoic=(mair/mfuel)stoic

=(4.76a/1)*(MWair/MWfuel)
where CxHy + a(O2+3.76N2)
xCO2+(y/2)H2O+3.76aN2
Equivalance ratio:
Equivalance ratio:
phi=((A/F)stoic)/(A/F)
phi=1 ...stoichiometric
phi<1 ...fuel lean
phi>1 ...fuel rich
CvHwSxOyNz
Absolute Enthalpy and Enthalpy of Formation
Absolute enthalpy
@T
Enthalpy formation
@Tref, P
Sensible enthalpy change
from Tref to T
Tref = 25 C
Pref = 1 atm
Enthalpy of Combustion
First Law Energy Balance - Control Volume
exiting combustion
products
incoming fuel and
air streams
Reactants
(Stoichiometric fuel-air mixture at standard state conditions)
Products
(complete combustion at standard state condition)
q (control volume)
enthalpy of combustion (reaction) --> q = h products - h reactants
Heating Value (Heat of the combustion)
Higher Heating Value (HHV): heat of combustion calculated assuming that all of the water in the products has condensed to liquid
Lower Heating Value (LHV): corresponds to the case where none of the water assumed to condense
example:
if liquid-->HHV
if vapor-->LHV
enthalpy of combustion:
Heating Value (Heat of combustion) is numerically equal to enthalpy of combustion, but with opposite sign
Adiabatic temperature of the combustion
Enthalpy of Combustion
T = 25 C
P = 1 atm
2 adiabatic flame temperatures;
1- Constant pressure adiabatic flame temperature
2- Constant volume adiabatic flame temperature
Figure: Illustration of constant-pressure adiabatic flame temperature on h-T coordinates
Assumptions:
Calculation with the assumptions
Computational results with the software
Chemical Equilibrium
Ideal Combustion
: CO2, H2O, O2, and N2
Dissociation
: H2, OH, CO, H, O, N, NO
Second Law Consideration is needed!!!
const. mass
const. volume
adiabatic reaction
T and P increases until equil. reached
CO+1/2 O2=CO2
İf T is high enough CO2 dissociate
Flue gas recirculation
Example:
Figure: Illustration of chemical equilibrium for a fixed mass isolated system
constant u, v, m
No heat and work interaction
second law
the condition for equilibrium
Gibbs function
second law
For a mixture of ideal gases, gibbs function for the ith species
equilibrium condition
Solution:
in the case of no FGR
Full transcript