5. Thermal Efficiency
• The thermal efficiency of an engine is the
efficiency of the conversion of the heat energy
released by the fuel into kinetic energy in the
jet stream.
6. Overall Efficiency
• The overall Efficiency compares the work done
on the aircraft to the energy given by the fuel.
7. Arrangement of Engine
T1=288 K
P1=101kPa
m=100kg/s
T3=1112 K
Compressor
=10
Combustor
Turbine
=10
Exhaust
Combustor
Turbine Entry Temperature
1112°K
Compressor compression ratio
= Turbine expansion ratio.
10
Specific Heat Capacity of Air at
constant Pressure (Cp)
Ratio of Specific Heat
Capacities for air ( )
Universal Gas Constant (R)
1 kJ/kg °K
1.4
287 kJ/kg °K
Inlet Air Temperature
288°K
Outside air pressure
101 kPa
Mass flow of air
100kg/s
Calorific value of fuel is
43,000 kJ/kg
12. Useful Work
T1=288 K
P1=101kPa
m=100kg/s
T3=1112 K
P3=1010kPa
T2=556 K
P2=1010kPa
Compressor
=10
T4=576 K
P4=101kA
Combustor
Turbine
=10
26,800kJ
Combustor
Exhaust
Subtract the Work done by the compressor (WC)from the work done on the turbine (WT)
to determine the useful work done by the engine on the aircraft.
Useful Work = WT – WC.
Useful Work = (53,600-26,800)=26,800 kJ
16. Part 2
T1=288 K
P1=101kPa
m=100kg/s
T3=1112 K
P3=1010kPa
T2’=556 K
P2=1010kPa
Compressor
=10
T4’=576 K
P4=101kA
Combustor
Turbine
=10
Combustor
Q
Repeat the analysis but with the compressor and turbine
efficiencies at 85%.
Exhaust
21. Turbine
T1=288 K
P1=101kPa
m=100kg/s
T3=1112 K
P3=1010kPa
T2’=556 K
T2=603 K
P2=1010kPa
Compressor
=10
T4’=576 K
T4 = 656 K
P4=101kA
Combustor
Turbine
=10
14,100kJ
Combustor
Exhaust
Q
Subtract the Work done by the compressor (WC)from the work done on the
turbine (WT) to determine the useful work done by the engine on the aircraft.
Useful Work = WT – WC.
Useful Work = (45,600-31,500)=14,100 kJ
25. T1=288 K
P1=101kPa
m=100kg/s
Part 3 T3=1112 K
P3=1010kPa
T2’=556 K
T2=603 K
P2=1010kPa
Compressor
=10
Combustor
Turbine
=10
T4’=576 K
T4 = ? K
P4=?kA
14,100kJ
Combustor
Q=50900kJ
Therefore the work
done by the turbine is
also 31,500kJ
26. T1=288 K
P1=101kPa
m=100kg/s
Part 3 T3=1112 K
P3=1010kPa
T2’=556 K
T2=603 K
P2=1010kPa
Compressor
=10
Combustor
Combustor
Q=50900kJ
Turbine
=10
T4’=576 K
T4 = 797 K
P4=?kA
Nozzle
27. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=?kA
Nozzle
28. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kPa
Nozzle
29. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
P5
30. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
As P5 is > P1 the nozzle is choked.
31. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
32. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
33. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
T5=664K
34. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
T5=664K
35. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
T5=664K
36. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kA
Nozzle
Combustor
P5=129kPa
T5=664K
Calculate the Specific Fuel Consumption of the engine.
The burning of the fuel heats the air from T2 to T3
Heat Energy required is: Q=m.cp(T3- T2 )
Q = 100 (1)(1112-603) = 50871kJ
37. T1=288 K
P1=101kPa
m=100kg/s
Part 3
T3=1112 K
T2’=556 K
P3=1010kPa
T2=603 K
P2=1010kPa Q=50900kJ
Compressor
=10
Combustor
Turbine
=10
T4’=741 K
T4 = 797 K
P4=244kPa
Nozzle
Combustor
P5=129kPa
T5=664K
39. T1=288 K
P1=101kPa
m=100kg/s
Afterburner
T3=1112 K
P3=1010kPa
T2’=556 K
T2=603 K
P2=1010kPa
Compressor
=10
Combustor
T4’=576 K
T4 = 797 K
P4=244kPa
Turbine
=10
T5 = ? K
P5=?
Afterburner
Combustor
Q=50900kJ
The exhaust gas is reheated to 2000K. the calculations are the
same as that the dry turbojet, but now the nozzle inlet
temperature is 2000K.
Nozzle
42. m=100kg/s
T2’=556 K
T2=603 K
P2=1010kPa
Compressor
=10
T3=1112 K
P3=1010kPa
Q=50900kJ
Combustor
T4’=576 K
T4 = 797 K
P4=244kPa
Turbine
=10
Combustor
At the throat of the nozzle, the air is travelling at the
speed of sound. Determine the velocity of the jet.
T5 = 1667 K
P5=129kPa
Afterburner
Nozzle
T1=288 K
P1=101kPa
Afterburner