THE COMBUSTION PROCESS
In order to operate a heat engine we need a hot source together with a cold sink. The most common way of doing this is by the combustion of a fuel. (Nuclear fission/fusion & solar are alternatives )
Solid:- Coal, wood - consists mainly of C, H, & O impurities
Liquid:- Large hydrocarbon molecules of varying boiling points mainly C & H : Petrol, Diesel, Fuel oil etc;
Gas:- Small hydrocarbon molecules - methane, ethane, propane, butane, etc; plus a range of manufactured gases ; eg H2 , Acetylene etc..
Usually air ( the oxygen in the air )
Where air is unavailable the oxidant has to be carried as well as the fuel - space vehicles, rockets etc;
SOLIDS :- pulverising to powder or small lumps
LIQUIDS :- spray nozzles, atomisers, vaporisers, carburettors, 'burners'.
GASES :- mixing valves, chambers, burners; usually need precautions to avoid explosion and flash back .
Simply mixing methane and air will not cause it to burn. The molecules need to reach a certain threshold energy level
before the combustion process will proceed. This may be provided initially by another flame, a spark or hot surface. The combustion process itself ( if sustained ) then continues the ignition process.
The chemical dissociation of the fuel and it's recombination with oxygen. Energy and Mass are conserved.
Other products may also be formed :-