Perform appropriate gas turbine engine analysis (data is given). Use the followi
ID: 2323034 • Letter: P
Question
Perform appropriate gas turbine engine analysis (data is given).
Use the following data to analyse the GT100s gas turbine. Source (with references including this assignment brief) any appropriate equations you needed for your analysis.
Speed
1000’s of rev/min
T1
oC
T2
oC
T3
oC
T4
oC
P1
mbar
gauge
P2
bar
gauge
P3
bar
gauge
P4
mbar
gauge
Nozzle 100%
85
22
109
524
474
22.9
0.84
0.72
53
100
22
136
570
498
34.6
1.26
1.1
87
Nozzle 85%
85
22
107
528
451
22.9
0.85
0.73
60
100
22
139
585
498
34.6
1.25
1.1
100
Speed
1000’s of
rev/min
Mass flow rate
gram / s
Air flow rate kg / s
T2i
oK
?i
%
Power to drive
compressor
W
Nozzle 100%
85
2.14
0.26
100
2.95
0.33
Nozzle 85%
85
2.21
0.27
100
2.94
0.33
cp = 1005 J/kgK
Atmospheric pressure from barometer: patmos= 1.013 bar
Guidance
Isentropic efficiency of a centrifugal air compressor (GT100S gas turbine)
Centrifugal compressor
Axial compressor fitted to a gas turbine
Theory: In reversible work transfer processes, the system passes from its initial to final state through a series of equilibrium states in which the properties are equal throughout the system at any given instant. There is no heat transfer (Q = 0) and it is assumed that there is no friction. A process in which there is no heat transfer is known as an adiabatic process. A reversible adiabatic process without friction is known as an ISENTROPIC PROCESS. This is the IDEAL WORK TRANSFER PROCESS.
Real processes are never reversible, and the compression processes of centrifugal compressors in particular, involve considerable turbulence and fluid friction. This means that during an actual irreversible compression process, frictional heating of the air produces a temperature rise that is greater than that which would have been produced if the process had been carried out reversibly without friction and turbulence.
The temperature at the end of a reversible adiabatic process, i.e. an ISENTROPIC process, may be calculated for IDEAL GASES from the equation:
T2i/ T1= (p2/ p1)(?– 1)/ ? where ? = 1.4 for air.
? The temperature at the end of an isentropic compression process = T2i = T1(p2 / p1)(? – 1)/ ?
The SFEE is: Q – W = ?PE + ?KE + ?H where ?H = mcp(T2 – T1) for a perfect gas.
But Q = 0 for an adiabatic process and ?PE and ?KE can be assumed negligible in this case, hence:
The REAL WORK required to compress the air = Wreal = mcp(T2 – T1) / kg
where T2 = the temperature of the air at the end of the actual compression process,
And the IDEAL WORK required to compress the air = Wisen = mcp(T2i – T1) / kg
where T2i = the temperature of the air at the end of the ideal ISENTROPIC compression process.
Note that T2 > T2i due to the frictional heating of the air in the actual compression process.
Then the isentropic efficiency ?i = Wisen / Wreal = (T2i – T1) / (T2 – T1)
Absolute pressure (p) = gauge pressure (pg) + atmospheric pressure.
Note that p = pg + patmos
Temperature at the end of an isentropic compression process = T2i = T1(p2 / p1)( ? – 1)/?
The isentropic efficiency ?i = Wisen / Wreal = (T2i – T1) / (T2 – T1)
Actual Power required to drive compressor = m(dash)cp(T2 – T1)
For the task you are recommended to examine how the isentropic efficiency and compressor power change with rev/min, and then draw key conclusions.
Speed
1000’s of rev/min
T1
oC
T2
oC
T3
oC
T4
oC
P1
mbar
gauge
P2
bar
gauge
P3
bar
gauge
P4
mbar
gauge
Nozzle 100%
85
22
109
524
474
22.9
0.84
0.72
53
100
22
136
570
498
34.6
1.26
1.1
87
Nozzle 85%
85
22
107
528
451
22.9
0.85
0.73
60
100
22
139
585
498
34.6
1.25
1.1
100
Explanation / Answer
i) What material properties should an engineer focus on to cope with the high rotational speed and high blade loading?
ii) What is the expression for the "flow coefficient"?
iii) What is the expression for "stage loading coefficient"?
iv) Given a turbine row with constant axial velocity of 150m/s at 5000 rpm on a mean radius of 0.7m and an absolute flow an absolute flow angle at exit from the stator of 70°. The turbine operates with axial leaving flow and is a repeating stage. Calculate the flow coefficient and the stage loading coefficient.
Analyse your results and comment.
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