Thermodynamics filled in class notes_Part_27

Thermodynamics filled in class notes_Part_27 - 2.8. DIESEL...

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Unformatted text preview: 2.8. DIESEL 61 P v T s 1 2 3 4 isobar isochore 1 2 3 4 isentrope isentrope Figure 2.17: P − v and T − s diagrams for the Diesel cycle. The thermal efficiency is found as follows: η = w net q H , (2.400) = q H − q L q H , (2.401) = 1 − q L q H , (2.402) = 1 − u 4 − u 1 h 3 − h 2 , (2.403) = 1 − c v ( T 4 − T 1 ) c P ( T 3 − T 2 ) , (2.404) = 1 − 1 k T 1 T 2 T 4 T 1 − 1 T 3 T 2 − 1 . (2.405) All else being equal, the Otto cycle will have higher efficiency than the Diesel cycle. However, the Diesel can operate at higher compression ratios because detonation is not as serious a problem in the compression ignition engine as it is in the spark ignition. Example 2.10 (adopted from BS, Ex. 12.8 pp. 501-502). An air standard Diesel cycle has a compression ratio of 20, and the heat transferred to the working fluid has 1800 kJ/kg . Take air to be an ideal gas with variable specific heat. At the beginning of the compression process, P 1 = 0 . 1 MPa , and T 1 = 15 ◦ C .....
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This note was uploaded on 11/26/2011 for the course EGN 3381 taught by Professor Park-sou during the Fall '11 term at FSU.

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Thermodynamics filled in class notes_Part_27 - 2.8. DIESEL...

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