basic combustion.htm
There's more to a Tune-up than a quick "Once-Over"...
Understanding Basic Combustion
Useful Information on Combustion Efficient Fuel Use
A Definition:
Combustion is the rapid oxidation of a fuel resulting in the release of usable heat and the production of a visible flame
The Combustion Equation:
Natural Gas With Air:
CH4 + 2O2 + 8N2 ----------->
CO2 + 2H2O + 8N2 + 1000 BTU Heat
Examples of Combustion
Perfect Combustion Provides:
The hottest flame
Minimum exhaust volume
Perfect Combustion
Characteristics:
- All fuel combusted
- Blue near burner tile
- Forms a yellow conical flame shape
- Produces the highest flame temperature
- Provides the minimum exhaust volume
Lean Combustion
Characteristics:
- Flue products oxidizing (Free O2)
- Pale blue color
- Forms a more conical flame
- All fuel combusted
- Flame temperature drops (Heating excess air)
Incomplete Combustion
Characteristics:
- Air starved or fuel rich
- Carbon Monoxide and H2 formed
- Reducing atmosphere
- Flame color is predominantly yellow color
- The flame is less defined
- Flame temperature drops
Optimum Energy Utilization Occurs When Perfect Combustion Ratios Are Maintained
When A Furnace Tune-Up Is Done Right The Technician will have taken time to:
- Verify proper mix and directed air/fuel supply
- Confirm that you have stable combustion
- Check to make sure that the system is venting all the by-products of the exhaust flue gases
A Definition of Combustion Terms
Excess Air Definition:
Air remaining after the fuel has been combusted-or-Air supplied in addition to the quantity needed for stoichiometric combustion
Primary & Secondary Air:
Primary Air --
-
Air mixed with the fuel prior to ignition
Secondary Air --
-
Air supplied to the flame after it is ignited
Secondary Air Effects --
- Imprecise air/fuel ratio control
- Exhaust volume increases
- Fuel rate rises
- Less available heat