The Otto cycle, a similar cycle to the Carnot cycle, can be used to describe an internal combustion engine and consists of 4 steps: i. reversible adiabatic compression from A to B ii. reversible constant-volume pressure increase from B to C due to the combustion of fuel iii. reversible adiabatic expansion from C to D iv. reversible constant-volume pressure decrease back to state A. a) Sketch the four steps of the Otto cycle on pressure and volume axes. Be sure to show the direction of change.
The Otto cycle, a similar cycle to the Carnot cycle, can be used to describe an internal combustion engine and consists of 4 steps:
i. reversible adiabatic compression from A to B
ii. reversible constant-volume pressure increase from B to C due to the combustion of fuel
iii. reversible adiabatic expansion from C to D
iv. reversible constant-volume pressure decrease back to state A.
a) Sketch the four steps of the Otto cycle on pressure and volume axes. Be sure to show the direction of change.
b) An engine is operating in the Otto cycle and that Cv = 5/2R for the air-fuel mixture initially at 298 K (temperature of the cold reservoir). What is the maximum theoretical efficiency of this engine if the mixture is compressed by a factor of 7.5 in the adiabatic compression step? Recall that efficiency, ε = 1 – Tcold/Thot.
c) How would this efficiency change if the compression ratio could be increased to 25? Is this likely to be a practical possibility?
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