Question: Problem 1 : Atkinson Cycle ( 4 6 points ) The ideal Atkinson cycle is a model for the combustion cycle used in hybrid -
Problem : Atkinson Cycle points
The ideal Atkinson cycle is a model for the combustion cycle used in hybridelectric vehicles. The ideal Atkinson cycle consists of four processes:
: Adiabatic and isentropic compression.
: Constant volume heat addition.
: Adiabatic and isentropic expansion back to the initial pressure.
: Constant pressure heat rejection.
For this problem, at the beginning of the cycle, the air is at a pressure of kPa and a temperature of K The compression ratio is and the air temperature at the end of the heat addition process replacement for combustion is K
For this problem, carry out a cold air standard analysis of the Atkinson cycle. Consequently, you may assume that the ratio of specific heat is constants is independent of temperature and equal to
To receive credit, you may not use thermofluids to solve this problem.
a Sketch the cycle in coordinates and sketch the corresponding Otto cycle with the same compression ratio. Indicate flows of work andor heat for each process in the Atkinson cycle. points
b Populate a scorecard of the pressure kPa temperature and specific volume at each state in the cycle. points
c In an Otto cycle, the "expansion ratio" is the same as the compression ratio. What is the expansion ratio for the Atkinson cycle? points
d Express the cycle efficiency analytically in terms only of the temperature at each state and the ratio of the specific heats points
e Calculate the cycle efficiency. How does this compare to a reversible cycle operating between the highest and lowest temperatures in the Atkinson cycle? points
f How does the cycle efficiency compare to a cold air standard Otto cycle with the same compression ratio? How could you have anticipated this result from the diagrams of the two cycles? points
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