about gas power cycle

1. SYNERGY INSTITUTE OF
ENGINEERING & TECHNOLOGY ,DNKL.
Name-ANSHUMAN
SINGH
Subject: Gas Power
Cycle
Topic : Gas Power Cycle
Teacher : Mr. N.R.SAHOO
Branch : Mechanical
Semester : 7th

2. Gas power cycle

3. CARNOT CYCLE
The Carnot gas cycle could be achieved in a
cylinder-piston apparatus (a reciprocating engine)
as shown in Fig. 1.
The Carnot cycle on the p-v diagram is as shown
in Fig. 1-a, in which processes 1-2 and 3-4 are
isothermal while processes 2-3 and 4-1 are
isentropic.
Fig. 1.

4. CONTINUE…

5. CONTINUE… Process 3-4
(Reversible Isothermal
Compression) :-
Q2 = W3-4 =
p3V3ln(V3/V4)
 Process 4-1
(Reversible Adiabatic
Compression):-
W3-4 = (p4V4 – p1V1)
ᵧ - 1
= - mCv (T1-T2)
 Process 1-2
(Reversible
Isothermal
Expansion) :-
Q1 = W1-2 =
p1V1ln(V2/V1)
 Process 2-3
(Reversible
Adiabatic
Expansion):-
W2-3 = (p2V2 – p3V3)
ᵧ - 1
= mCv (T1-T2)

6. CONTINUE…
So,
W = work done by the system – work done on
system
= mRT1 ln(V2/V1) – mRt2 ln(V3/V4)
= Q1 – Q2.
ηth = net work output
heat output
= W/Q
= T1 – T2 = 1 – (T2/T1)
T1

7. OTTO CYCLE
It is also called as constant volume cycle
because heat is supplied and rejected at constant
volume.
Nicholas-A-otto, a german engineer developed
the first cycle which is first successful engine
working on this cycle. So it is called as otto cycle.
This cycle consists of the two reversible adiabatic
& two reversible isochoric process.

8. CONTINUE…

9. CONTINUE…
The air-standard Otto cycle is the ideal cycle that
approximates the spark-ignition combustion
engine.
 Process Description
 1-2 Isentropic compression
 2-3 Constant volume heat addition
 3-4 Isentropic expansion
 4-1 Constant volume heat rejection
The P-v and T-s diagrams are shown in fig.(2)

10. THERMAL EFFICIENCY OF THE
OTTO CYCLE
 Now to find Qin and Qout.
 Thus, for constant specific heats,

11. The thermal efficiency becomes

12. Recall processes 1-2 and 3-4 are isentropic, so
Since V3 = V2 and V4 = V1, we see that

13. N since process 1-2 is isentropic,
 The Otto cycle efficiency becomes
Here,

14. DIESEL CYCLE
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The air-standard Diesel cycle is the ideal cycle
that approximates the Diesel combustion engine
 Process Description
 1-2 Isentropic compression
 2-3 Constant pressure heat addition
 3-4 Isentropic expansion
 4-1 Constant volume heat rejection
The P-v and T-s diagrams are as shown in
above figure.

15. 15

16. 16
Thermal efficiency of the Diesel cycle
Now to find Qin and Qout.
Apply the first law closed system to process 2-3,
P = constant.

17. 17

18. The thermal efficiency becomes
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19. Brayton Cycle
19
The Brayton cycle is the air-standard ideal cycle
approximation for the gas-turbine engine. This
cycle differs from the Otto and Diesel cycles in
that the processes making the cycle occur in
open systems or control volumes. Therefore, an
open system, steady-flow analysis is used to
determine the heat transfer and work for the
cycle.
We assume the working fluid is air and the
specific heats are constant and will consider the
cold-air-standard cycle.

20. Schematic diagram of brayton
cycle
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21. Continue…
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 The T-s and P-v diagrams are shown in
below figure.

22. 22

23. Thermal efficiency of brayton
cycle
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24. REFERENCES
• Text book of engineering thermodynamics
by p k nag
• Google.com
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25. Any Queries ???
THANK YOU…!!!
&
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