For instance given a mole fraction of CH4 to be 0.4 and that of oxygen to be 0.6. How is the equivalence ratio determined.
Moreover too, in a combustion experiment, how is the equivalence ratio determined at different flow rates.
Thanks
Dear Evan,
Equivalence ratio (phi) is defined as actual fuel and oxidizer ratio [(F/A)ac] divided by stoichiometric fuel and oxidizer ratio [(F/A)st].
phi = (F/A)ac/(F/A)st
For CH4/O2 case
CH4 + 2O2 ---------> CO2 + 2H2O
(F/A)st = 1/2
(F/A)ac = 0.4/0.6 =2/3
so phi = (2/3)/(1/2) = 4/3 (rich mixture)
To answer your second question. Individual compound flowrate divided by total flowrate at same pressure are equivalent to mole fractions.
ϕ=fuel-to-oxidizerratio(fuel-to-oxidizerratio)st=mfuel/mox(mfuel/mox)st=nfuel/nox(nfuel/nox)st
Hi Evans Quaye
Do you want to measure or to calculate the equivalence ratio at different flow rates?
Hello Nazaruddin Sinaga
The flow meters are set in sccm units for both the fuel and oxidizer. How is the the equivalence ratio calculated from the flow meters
Evans Quaye
There is two kind of equivalence ratio (ER), i.e. Air to Fuel ER (AFR-ER) and Fuel to Air ER (FAR-ER). So, AFR-ER = 1/FAR-ER.
AFR-ER = (air mass/fuel mass)real/(air mass/fuel mass)stoichio
Please mention that it is a ratio of mass or ratio of mass rate. If you got volume rate from your measurement, please change it to be in mg/s or gr/l. ...
Nazaruddin Sinaga do they serve the-same purpose?
Moreover, concerning my earlier question how do you determine the equivalence ratio from flow rates?
Just change the flow rates to mass rates (by multiplying with the density), and do what I said above.
AF=(1/max(C3H8.Mass Fraction,0.0000001))
ER= stoichiometric AF/actual AF
Syed Mughees Ali I was trying to calculate phi are you sure about your answer?
you have a mole ratio with mole fraction ratio which is different.
I think you need to convert the mole fraction to moles and then use the ratio as you suggested.
Dear mohammad sadik Rizvi
Kindly calculate it using the number of moles and let me know the answer. I also suggest to write an equivalence ratio in terms of mole fraction and cross-check with your previous answer. I have 100 % sure that you will get the same answer. Mole fraction is just a way to normalize the number of moles of substance present in the mixture.
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