Three experiments are carried out where the combustion of CH 4 (the fuel) is bei
ID: 900603 • Letter: T
Question
Three experiments are carried out where the combustion of CH4 (the fuel) is being carried out with the theoretical amount of oxygen (in the oxidizer). But the composition of the oxidizer (in % volume) varies as:
Experiment 1: 21% O2: 79% N2
Experiment 2: 21% O2: 79% Ar
Experiment 3: 21% O2: 79% CO2
Note that N2, Ar and CO2 are inerts in the oxidizer and do not participate in the reaction.
a.) How does an inert species influence the flame temperature?
b.) Will the flame temperatures be the same in all three cases? Which experiment will have the lowest and which the highest flame temperature? Why?
Explanation / Answer
Ar and CO2 are heavier than N2.
a) The use of a heavier inert gas in the air mixture will act as a blanket for the flame and would prevent combustion. The flame temperature would thus go down when N2 is replaced with Ar or CO2 in experiment 2 and 3. In order to fully combust the gases under such conditions a much higher flame temperature would thus be needed for the same amount of combustible material (fuel).
b) The flame temperature in experiment 2 and experiment 3 will be much higher then the flame temperature in experiment 1. The lowest temperature would be for experiment 1 with N2 as the inert gas in a gas mixture. N2 does not interfere in the combustion and is much lighter then air which helps combustion process.