[arvindpj]

In a furnace, if I burn 30000 BTU/hr of Natural Gas with heating value of 1000 BTU/ft3. I get a certain excess air value. We know the stoic A/F ratio for NAT/Air combustion is 10.9:1.

In the same furnace, If I was to burn 30000 BTU/hr of 100 % Methane Gas with heating value of 8000 BTU/ft3. What would be the excess air? Here too we know the stoic A/F ratio of 9.52:1

Will the air excess be the same? Is there a procedure to estimate the air excess of Methane gas based on the measurements of NAT gas?

[arvindpj]

My intention is to simulate in Fluent with 100 % CH4 to mimic the combustion of Natural Gas which is 85% CH4.

The heating values of the two fuels are different and their air-fuel ratio are different as well.

If I burn equivalent mass with same energy content (say 30000 BTU/hr):

Will they require same oxidizer (air) amount. or will the computed air excess be the same?

or

Will the exhaust products mole fractions be the same?