An engine operating under the ideal Otto cycle takes air in

An engine operating under the ideal Otto cycle takes air in at 25 degree C and 95 kPa, then compresses it. The combustion adds 850 kJ/kg to the air, after which the temperature is 1900 K. Sketch the P-v diagram for this process. What is the compression ratio of this engine? What is the maximum pressure? What is the thermal efficiency? What is the mean effective pressure?

Solution

compression ratio of the engine is V₁ /V₂

from the given data.

p1 = 95kpa ,

t1 =25+273

=298

t2 = 1900

P1 /p2 = (t1 /t2)

therefore p2 = 605.86 kpa

therefore compression ratio = p2/p1

= 6.3

(b) the maximum pressure is at p2 = 605.86 kpa