If CH4 undergoes combustion with stoichiometric quantity of air, the AFR will be (a) 16.23

If CH4 undergoes combustion with stoichiometric quantity of air, the AFR will be

(a) 16.23, (b) 14.5, (c) 9.52, (d) 13.11

Determine AFR on the molar basis.

Solution:  The reaction involved in the combustion of methane is

CH₄ + 2O₂ à CO₂ +2H₂O

Here 1volume of methane needs 2 volume of O2

We know that in air there is 21% oxygen, which means

21m³ of oxygen is present in 100m³ of air

So 2m³ of oxygen present in (100/21)*2=9.52

AFR = mass of air/mass of fuel=9.52/1=9.52