Stoichiometry of Gasoline
STOICHIOMETRY OF GASOLINE.
AN INTRODUCTION
The internal combustion engines burn fuel to create kinetic energy. The burning of fuel is basically the reaction of fuel with oxygen in the air to form water and Carbon dioxide as the major end product . The amount of oxygen present in the cylinder is the limiting factor for the amount of fuel that can be burnt that is to say it determines the level of burning in our combustion engine. If there’s too much fuel present, not all fuel will be burnt and un-burnt fuel will be pushed out through the exhaust valve.
When building an engine, it is therefore very important to know the air-fuel ratio at which exactly all the available oxygen is used to burn the fuel completely or at least to the best possible value. This ratio is called the stoichiometric air-fuel ratio.
Theoretically, this ratio exist only for a stoichiometric mixture, which is an ideal mixture. In practice this mixture has never been formed for any machine so far. However, air-fuel ratios close to it can be achieved by modifying engine design and making use of proper admixtures and catalysts to keep a check on the pressure and temperature of the fuel.
The fuel combustion take place at very high temperature and pressure thus the process has to be well regulated to avoid an explosion. Also a way of releasing this excess pressure has to be included.
Calculating the Ratio
The chemical formula for gasoline is given by
C8H18
During combustion with oxygen we get the balanced equation as follows,
2C8H18 + 25O2 ~~~ 16CO2 + 18H2O
With C = 12.01
And H = 1.008
And 0 = 16
Molecular mass of gasoline is given by ,
2*12.01*8 = 192.16 + 2*18*1.01 = 228.52
Molecular mass of oxygen is given by, 25*16*2 = 800
Stoichiometric ratio = 800/228.52 = 3.5018 of oxygen
But in air we take oxygen as 23.2% of the composition.
Therefore in air we get (100* 3.5018)/23.2
Air- fuel ratio = 15.08/1 (stoichiometric)
The ratio above is for ideal situation
AN INTRODUCTION
The internal combustion engines burn fuel to create kinetic energy. The burning of fuel is basically the reaction of fuel with oxygen in the air to form water and Carbon dioxide as the major end product . The amount of oxygen present in the cylinder is the limiting factor for the amount of fuel that can be burnt that is to say it determines the level of burning in our combustion engine. If there’s too much fuel present, not all fuel will be burnt and un-burnt fuel will be pushed out through the exhaust valve.
When building an engine, it is therefore very important to know the air-fuel ratio at which exactly all the available oxygen is used to burn the fuel completely or at least to the best possible value. This ratio is called the stoichiometric air-fuel ratio.
Theoretically, this ratio exist only for a stoichiometric mixture, which is an ideal mixture. In practice this mixture has never been formed for any machine so far. However, air-fuel ratios close to it can be achieved by modifying engine design and making use of proper admixtures and catalysts to keep a check on the pressure and temperature of the fuel.
The fuel combustion take place at very high temperature and pressure thus the process has to be well regulated to avoid an explosion. Also a way of releasing this excess pressure has to be included.
Calculating the Ratio
The chemical formula for gasoline is given by
C8H18
During combustion with oxygen we get the balanced equation as follows,
2C8H18 + 25O2 ~~~ 16CO2 + 18H2O
With C = 12.01
And H = 1.008
And 0 = 16
Molecular mass of gasoline is given by ,
2*12.01*8 = 192.16 + 2*18*1.01 = 228.52
Molecular mass of oxygen is given by, 25*16*2 = 800
Stoichiometric ratio = 800/228.52 = 3.5018 of oxygen
But in air we take oxygen as 23.2% of the composition.
Therefore in air we get (100* 3.5018)/23.2
Air- fuel ratio = 15.08/1 (stoichiometric)
The ratio above is for ideal situation