An engine operates on isooctane A dry gas analysis of the en

An engine operates on isooctane. A dry gas analysis of the engine exhaust gives the following volumetric percentages:

An engine operates on isooctane. A dry gas analysis of the engine exhaust gives the following volumetric percentages. CO2 = 11.96% O2 = 3.74% CO = 0% Find the equivalence ratio. Neatly

Solution

Formula of Isooctane is C8H18 .

Combustion is given by the equation

2C8H18 + 25O2 => 16CO2 + 18H2O

Equivalence Ratio is Given By

= =

Also

=

So First Calculating

Fuel to Oxidizer Ratio of the problem based on MASS

If there is one mole of isooctane then

As per the given dry gas analysis

Moles of CO2 = 0.1196

Moles of O2 = 0.0374

Moles of CO = 0

2C8H18 + 25O2 => 16CO2 + 18H2O

Equation shows that Moles of Oxygen required to burn 2 moles of isooctane = 25 moles.

0.0374 moles of oxygen as given in the dry analysis can burn = 25/2* 0.0374 = 0.4675 moles of isooctane

=>    = = 44.531

Fuel to Oxidizer Ratio of the problem based on Moles

= 0.4675/0.0374 =12.5

Then Equivalence Ratio is   = 44.531/ 12.5 = 3.56248