Question

The combustion in a gasoline engine may be approximated by a constant volume heat addition process. There exists the air-fuel mixture in the cylinder before the combustion and the combustion gases after it, and both may be approximated as air, an ideal gas. In a gasoline engine, the cylinder conditions are 0.95 MPa and 425◦C before the combustion and 1700◦C after it. Determine the pressure at the end of the combustion process

Answer 1

the pressure at the end of the combustion is 2.68 MPa

Solution:

As per the question:

Initial Pressure, P = 0.95\ MPa

Temperature before combustion,
`T = 425^(\circ)C` = 273 + 425 = 698 K

Temperature after combustion,
`T' = 1700^(\circ)C` = 1973 K

Now,

To calculate the pressure at the end of combustion, P':

By using the Pressure-Temperature relation from Gay- Lussac's law:

`(P)/(T) = (P')/(T')`

`P' = (P)/(T)* T'`

`P' = (0.95* 10^(6))/(698)* 1973 = 2.68* 10^(6)\ Pa = 2.68\ MPa`