Brayton Cycle

Guided by;Prof. Sankalp Kulkarni

G.H Patel College of Engineering and Technology

By: 150110119126 ( Sharvil )150110119127 ( Vishvak )150110119128 ( Festus )( 2C19 )Mechanical Engineering

• In a gas turbine plant, working on the Brayton cycle with a re-generator of 75% effectiveness, the air at inlet to the compressor is at 0.1 MPa, 30°C, the pressure ratio is 6, and the maximum cycle temperature is 900°C. If the turbine and compressor have each an efficiency of 80%, find the percentage increase in the cycle efficiency due to regeneration.

Solution: p₁ = 0.1 MPa T₁ = 303 K T₃ = 1173 K rp = 6, ƞT = ƞC = 0.8

T

s

2s 2

6

3

44s

51

P = c

Without a regenerator = () = = (6) = 1.668 = 303*1.668 = 505 K = = 705 K T₂ - T₁ = = = 252 K T₃ - T₄ = ƞT (T₃ - ) = 0.8 (1173 – 705) = 375 K

WT = h₃ - h₄ = cp (T₃ - T₄) = 1.005 * 375 = 376.88 Wc = h₂ - h₁ = cp (T₂ - T₁) = 1.005 * 252 = 253.26

T₂ = 252 + 303 = 555 K Q₂ = h₃ - h₂ = cp (T₃ - T₂) = 1.005 (1173 – 555) = 621.09

ƞT = = = 0.199 or 19.9%

(Ƴ−1) /Ƴ (0.4 )/1.4

With regenerator T₄ = T₃ - 375 = 1173 – 375 = 798 K

Regenerator effectiveness = = 0.75T₆ - 555 = 0.75 (798 – 555) T₆ = 737.7 K Q₁ = h₃ - h₆ = cp (T₃ - T₆) = 1.005(1173- 737.3) = 437.88

Wnet remains the same. = = = 0.2837 or 28.37%

Percentage increase due to regeneration = = 0.4256 or 42.56%

• In an ideal Brayton cycle, air form the atmosphere at 1 atm, 300K is compressed to 6 atm and the maximum cycle temperature is limited to 1100 Kby using a large air-fuel ratio. If the heat supply is 100 MW, find (a) the thermal efficiency of the cycle, (b) work ratio, (c) power output, (d) exergy flow rate of the exhaust gas leaving the turbine.

Solution:the cycle efficiency,

ƞcycle = 1 - = 1 - = 0.401 or 40.1 %

= (rp ) = 1.67T₂ = 501 K = 1.67, T₄ = = 658.7 K

(Ƴ−1) /Ƴ

(Ƴ−1) /Ƴ ()

WC = 1.005 ( 501 – 300 ) = 202 WT = 1.005 ( 1100 – 658.7 ) = 443.5 - Work ratio = = 0.545- Power output = 100 * 0.401 = 40.1 MW- Q₁ = ṁ CP (T₃ - T₂) = 100000 kW- ṁ = 166.1 - Exergy flow rate of the exhaust gas stream

= ṁ CP T₀( -1 - ln ) = 166.1 * 1.005 * 300 ( -1 - ln )= 20.53 MW

Thank You