Thermodynamics filled in class notes_Part_26

# Thermodynamics filled in class notes_Part_26 - 59 2.7. OTTO...

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Unformatted text preview: 59 2.7. OTTO One uses the isentropic relations for state 4: T3 T4 V4 V3 k −1 = T4 T3 V3 V4 k −1 = = T3 V2 V1 k −1 T4 = T3 V1 V2 1−k T4 = (3600 ◦ R)(8)1−1.4 , (2.381) = ◦ (2.382) , (2.377) , (2.378) , (2.379) , (2.380) 1566.99 R. For the pressure at state 4, use the ideal gas law: P4 V4 T4 = P4 = = P3 V3 , T3 V3 T4 P3 , V4 T3 V2 T4 P3 , V1 T3 (2.383) (2.384) (2.385) = (53.3333 atm) = 1 8 2.90184 atm. 1566.99 ◦ R , 3600 ◦ R (2.386) (2.387) The thermal eﬃciency is η 1 , k rv −1 1 = 1 − 1.4−1 , 8 = 0.564725. = 1− (2.388) (2.389) (2.390) CC BY-NC-ND. 18 November 2011, J. M. Powers. 60 CHAPTER 2. CYCLE ANALYSIS Now get the mean eﬀective pressure Pmef f . Wnet = Pmef f = = = = Pmef f (Vmax − Vmin ), Wnet , Vmax − Vmin m(u3 − u4 ) + m(u1 − u2 ) , V1 − V2 cv T 3 − T 4 + T 1 − T 2 m , V1 1 − V2 V1 P1 V1 cv T3 − T4 + T1 − T2 , RT1 V1 1 − V2 V (2.391) (2.392) (2.393) (2.394) (2.395) 1 = P1 cv T3 − T4 + T1 − T2 , V T1 R 1 − V2 (2.396) 1 = P1 1 T3 − T4 + T1 − T2 , V T1 k − 1 1 − V2 (2.397) 1 = (2.398) = 2.8 1 atm 1 3600 ◦ R − 1566.99 ◦ R + 540 ◦ R − 1240.59 ◦ R , ◦ R 1.4 − 1 540 1− 1 8 7.04981 atm. (2.399) Diesel The air standard Diesel cycle approximates the behavior of a Diesel engine. It is modeled as a ﬁxed mass system. Here the compression is done before injection, so there is no danger of premature ignition due to detonation. No spark plugs are used. Diagrams for P − v and T − s for the Diesel cycle are shown in Figure 2.17. One can outline the Diesel cycle as follows: • 1 → 2: isentropic compression in the compression stroke, • 2 → 3: isobaric heating in the combustion stroke, • 3 → 4: isentropic expansion in power stroke, and • 4 → 1: isochoric rejection of heat to the surroundings. CC BY-NC-ND. 18 November 2011, J. M. Powers. ...
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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_26 - 59 2.7. OTTO...

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