1) The Brayton cycle describes the ideal thermodynamic cycle of a gas turbine engine. It involves constant pressure heat addition and isentropic expansion/compression processes. 2) The key processes are: isentropic compression in the compressor, constant pressure heat addition in the combustor, isentropic expansion in the turbine, and constant pressure heat rejection to the atmosphere. 3) The thermal efficiency of the Brayton cycle depends on the temperature ratios between the different states and can be expressed in terms of the pressure ratio across the compressor and turbine. Higher pressure ratios lead to higher efficiencies.

1. L.D.ENGINEERING
SUBJECT:- ENGINEERING THERMODYNAMIC
TOPIC NAME:- BRAYTON CYCLE
BRNCH:- MECHANICAL B
BATCH:- 3
STUDENT NAME ENROL NO
PATEL DIPESSH 140283119018
NANE HIMANSHU 140283119015
BHAVSAR DHVANIL 140283119002

2. Brayton Cycle
•A gas turbine is a rotary power unit used for producing large
quantities of power in a self contained and compact unit.
•The gas turbine power plant are suitable for aircraft, marine,
military and transport application due to its smaller size and low
weight power ratio.
•These plants are free from vibration, perfect in balance, simple in
installation, operation and maintenance. These are highly reliable
•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.
•We assume the working fluid is air and the specific heats are
constant and will consider the cold-air-standard cycle.

3. The closed cycle gas-turbine engine
The open cycle gas turbine

4. Process involved in a cycle :
1.Isentropic compression (1-2) :- surrounding air is compressed
isentropically pv^γ = c in the compressor from pressure p1 to p2
work of compression Wc
2.Constant pressure heat addition (2-3:)- heat is added in
combustor at constant pressure and constant temp is raised from T2
to T3 there fore pressure P3= p2
3.Isentropic expansion (3-4):-hot gases at p2, T3 expand in gas
turbine isentropically up to atmospheric pressure P1 , work
developed by turbine wt
4.Constant pressure heat rejection (4-1) :- heat is rejected by
exaust gases at constant pressure to the atmosphere.

5. The T-s and P-v diagrams
are

6. Thermal efficiency of the brayton cycle
ηth Brayton
out
in
out
in
p
p
Q
Q
q
q
C T T
C T T
,


( )
( )
= − = −
= −
−
−
1 1
1
4 1
3 2
ηth Brayton
T T
T T
T T T
T T T
,
( )
( )
( / )
( / )
= −
−
−
= −
−
−
1
1
1
1
4 1
3 2
1 4 1
2 3 2

7. •The steady flow energy equation can be used for cycle analysis
with changes in K.E and P.E negligible
S.F.E.E can be written as
Q-Wsf = m (∆h+ ∆ K.E + ∆ P.E)
But ∆ K.E = 0 ∆ P.E = 0 and h=Cp.T
S.F.E.E. reduce to Q-Wsf = m ∆h
1.compresser work
•Process (1-2) is irreversible adiabatic process Q1-2 = 0 and work
is nagative.
0-(-Wc) = m (h2-h1) = m Cp (T2-T1)
Wc = m Cp (T2-T1)

8. Heat addition process:-
Wsf = 0 therefore Q2-3 = m (h3-h2) = m Cp (T3-T2)
Turbine work:- process (3-4) is reversible adiabatic ,
hence Q=0
0-Wt = m (h4-h3)
Wt = m (h3- h4) = m Cp (T3-T4)
Shaft work Ws = turbine work (Wt) – compressor work (Wc)
= m Cp (T3-T4) - m Cp (T2-T1)
Air standard efficiency of cycle

9. Air standard efficiency of cycle:-
ռ = m Cp (T3-T4) - m Cp (T2-T1)
m Cp (T3-T2)
ռ= 1- (T4-T1)
(T3-T2)
(d) Efficiency in terms of pressure ratio
Let, pressure ratio Rp = P2 = P3
P1 P4
ηth Brayton
T T
T T
T T T
T T T
,
( )
( )
( / )
( / )
= −
−
−
= −
−
−
1
1
1
1
4 1
3 2
1 4 1
2 3 2

10. T2 _ P2 ^(γ – 1)/γ And T3 _ P3 ^(γ – 1)/γ
T1 P1 T4 P4
= (Rp) ^(γ – 1)/γ
T2 = T1 (Rp) ^(γ – 1)/γ and
T3 = T4 (Rp) ^(γ – 1)/γ
so we get ,
ռ = 1 - (T4-T1)
T4 (Rp) ^(γ – 1)/γ T1 (Rp) ^(γ – 1)/γ

11. ռ = 1- 1/ (Rp) ^(γ – 1)/γ
Which is the efficiency of brayton cycle in
term of pressure ratio