F1, F2 Flashcards
3 basic requirements of combustion
Fuel heat oxygen
What percentage of oxygen
20
3 possible sources of the initial heat required for combustion
Pilot flame
Spark igniter
Hot surface igniter (glow coil)
Write the formula for the chemical reaction in the combustion of methane and air
Ch4+ 2o2 -> co2+ 2h2o+ heat
When we completey burn a hydrocarbon fuel such as nat gas or propane the products of combustion are
C02
H2o
N2
Heat
Which type of combustion has been created if carbon monoxide is found in products of combustion
Incomplete
Describe perfect combustion
Theoretical volume of air that must be mixed with fuel gas to achieve perfect combustion. 10 cuft of air for every 1000 btu of gas, (theoretical)
Describe complete combustion
Supplying air in excess of perfect combustion to ensure all atoms of carbon and hydrogen are united with enough oxygen atoms to produce complete combustion
Describe incomplete combustion
Not enough oxygen is available to burn the fuel gas completely. CO is produced
Name a product of incomplete combustion which is toxic and has a penetrating odour
Aldehydes
Explain primary air and give the number of cuft to mix w 1 cuft n gas
Combustion air mixed with the fuel gas before ignition 1/3 of a 10:1 ratio 1 cuft ch4 requires 3.33 cu fr primary air
Secondary air and number of cuft to mix w 1 cuft ch4
Combustion air supplied around the flames, ocupies 6.66 cuft for every 1 cuft of ch4
Excess air
Air required in addition to theoretical combustion air to ensure complete combustion occupies aprox 50% of theoretical combustion air
Why must excess air be kept to a minimum
It absorbs heat and carries it off to the venting system causes appliance to be less efficient
Purpose of dilution air
The room air entering the venting system at a draft control device it cools hot vent gases and controls the draft influence on the combustion chamber
