Gas Turbine Jet Engine
Objectives
This lab experiment was aimed at doing a start-up and power-down of Gas Turbine and data
logging and become familiar with engine and its controls.
Introduction
A pure turbojet, CM-14 represents a jet engine. In this engine combustion causes expansion of
gas capable of producing useful work and thus cause jet propulsion. It consists of a centrifugal
flow compressor, axial flow power turbine, and annular combustor. The CM-14 engine is a
model of gas generator core common in turbofan, turboshaft and turboprop gas turbine engines
that are commonly used in marine and aircraft propulsion as well as in industrial and stationary
power generation. The following figure shows a model gas turbine.
Figure 1: Gas turbine.
This gas turbine is made up of 4 sections and which are:
o Inlet part
o Compression part
o Combustion part
o Turbine and exhaust part
The turbine part is responsible for creating needed power output to run propeller. It also serves to
generate power for driving all other parts of the turbine and compressor. For it to produce power,
this gas turbine has to expand gas at high pressure, velocity and temperature and transforms gas
energy to mechanical energy available at the power shaft. The compressor is used to provide a
certain amount of air. It works by creating air to the engine and where it is squeezed to generate
high-pressure air needed in the turbine. Compressor works using mechanical power from turbine
that converts gaseous energy in form of temperature and pressure. Gas turbine encounters
frictional losses which makes it hard for the compressor to provide all air required by turbine. As
such, the turbine does not provide all the power required by compressor. Therefore, it means
energy has to be added to the air so as to supplement the deficit.
The combustion part is where energy is produced. This happens when fuel is burned and fuel
chemical energy transformed into gaseous energy at high temperature and air velocity. The
gaseous energy is then transformed into mechanical energy and used to drive output shaft and
compressor. Basically, the gas turbine consists of 4 cycles which are air intake, air compression,
combustion and expansion and exhaust. The figure below shows cycles of a closed gas turbine
on a T-S diagram.
Figure 1: Closed gas-turbine T-S diagram
From the gas turbine cycles stages 1 and 2 illustrates air compression in the compressor. Some
work is done here and it is given by 𝑤12 = −( ℎ2 − ℎ1 ) = −𝐶𝑝 (𝑇1 − 𝑇2 )
After being compressed the air goes from stage 2 to 3 where undergoes heat addition at constant
pressure. Heat is added and it can be calculated by using the equation 𝑤23 = ( ℎ3 − ℎ2 ) =
𝐶𝑝 (𝑇3 − 𝑇2 )
From stage 3 to 4 air from combustion is compressed in the turbine. The work done by turbine
can be calculated by 𝑤𝑛𝑒𝑡 = 𝐶𝑝 ( 𝑇3 − ℎ4 ) − 𝐶𝑝 (𝑇2 − 𝑇1 )
Heat input for this cycle is given by 𝑄𝑖𝑛 = 𝐶𝑝 (𝑇3 − 𝑇2 )
1
As such, efficiency can be computed by ɳ = 1 − (𝑟 )
ɣ−1
ɣ
Gas turbine performance is depended on shaft horse power the engine produces at certain
conditions. Most of jet engines have power ratings at 29.92 inches of mercury and 59oF. The
specific fuel consumption at a certain condition defines the engine efficiency. The efficiency is
determined by amount of air mass flow rate via the engine, operating temperatures, compressor
pressure ratio, and individual component efficiencies.
SAFETY PRECAUTION
Safety was maintained by following instructions given by the manufacturer and also using
common sense when handling high temperature and pressure. In addition, a distance of 10m was
maintained on both sides when starting the experiment.
Apparatus

Electronic console

Engine module

User PC with Armfield
Before startup
Prior to starting the experiment fuel was prepared and filled in a container as recommended by
Armfield. Fuel ratio was 22.5% meaning 225ml of Aeroshell (Turbine 500) in 1000 ml of
kerosene.
PROCEDURE
The Electronic console master switch was turned on. Armfield software was loaded onto the
user PC and view diagram screen was selected. This displayed mimic diagram of the engine
with readings from sensors superimposed. The screen showed readings for the engine
parameters that is thrust, shaft speed, temperatures and pressure. The diagram on the screen of
PC look like the one shown below.
Before engine was started and recorded results zero buttons were clicked on all the sensor edit
fields given with this function. This helped to compensate with residual errors in sensors.
Observation
Table 1:
S.N0
Throttle
Position
T1
T2
T3
T4
T5
P0
P1
P2
P3
P4
P5
T
n
l
[%]
1
27.00
29
52
654
611
622
101.30
-1.84
41.02
31.01
33.20
7.34
24
47988
0.38
2
32.00
28
55
615
511
520
101.30
-1.17
23.93
17.58
18.55
3.67
9
37441
0.17
3
34.00
27
54
604
503
504
101.30
-1.25
24.66
18.31
19.04
3.79
12
38203
0.17
4
24.00
27
82
540
504
501
101.30
-5.12
89.60
70.80
70.56
15.55
48
67910
0.34
5
30.00
27
97
506
481
483
101.30
-6.80
107.42
93.26
93.51
21.45
64
75469
0.39
6
37.00
27
111
501
470
473
101.30
-8.20
128.66
113.53
111.82
25.55
70
80859
0.43
7
42.00
27
124
500
470
472
101.30
-9.84
152.34
131.35
129.15
28.59
91
85371
0.47
Corresponding Data
Table 2
Air
Mas
s
Flow
Rate
Cp
1
Cp
2
Cp
3
Cp
4
Cp
5
S1
S2
S3
S4
S5
H1
H2
H3
H4
H5
0.32
1.0
0
1.0
1
1.1
3
1.1
2
1.1
2
0.0
0
3.9
8
6.6
4
6.6
3
6.6
6
306.6
9
329.6
9
967.7
9
920.3
0
932.5
2
0.26
1.0
0
1.0
1
1.1
2
1.0
9
1.1
0
0.0
0
4.0
8
6.6
0
6.4
4
6.4
7
305.9
3
333.1
0
924.6
2
809.5
6
819.5
3
0.26
1.0
0
1.0
1
1.1
2
1.0
9
1.0
9
0.0
0
4.0
6
6.5
8
6.4
2
6.4
4
305.4
3
332.1
3
912.0
3
801.1
0
801.6
0
0.53
1.0
0
1.0
1
1.1
0
1.0
9
1.0
9
0.0
0
4.3
8
6.3
6
6.4
0
6.4
3
305.4
3
359.9
5
841.5
9
802.0
9
798.6
1
0.62
1.0
0
1.0
1
1.0
9
1.0
9
1.0
9
0.0
0
4.5
2
6.2
5
6.3
3
6.3
9
305.1
8
375.3
3
803.3
7
776.8
0
779.2
7
0.68
1.0
0
1.0
1
1.0
9
1.0
8
1.0
9
0.0
0
4.6
4
6.2
2
6.3
0
6.3
7
304.9
3
390.0
2
798.8
9
764.9
4
767.9
0
0.74
1.0
0
1.0
1
1.0
9
1.0
8
1.0
9
0.0
0
4.7
2
6.1
9
6.2
9
6.3
7
304.6
8
402.3
5
797.7
7
764.9
4
766.9
1
[kg/
s]
Nomenclature
T1 Inlet Temperature [°C]
Cp1 Specific Heat at inlet [KJ/Kg K]
T2 Compressor Temperature [°C]
Cp2 Specific Heat in compressor [KJ/Kg K]
T3 Combustor Temperature [°C]
Cp3 Specific Heat at combustor [KJ/Kg K]
T4 Turbine Temperature [°C]
Cp4 Specific Heat at Turbine [KJ/Kg K]
T5 Exhaust Temperature [°C]
Cp5 Specific Heat at Exhaust [KJ/Kg K]
P0 Ambient Pressure [kPa]
S1 Entropy at inlet [KJ/Kg K]
P1 Inlet Pressure [kPa]
S1 Entropy in compressor [KJ/Kg K]
P2 Compressor Pressure [kPa]
S1 Entropy at combustor [KJ/Kg K]
P3 Combustor Pressure [kPa]
S1 Entropy at Turbine [KJ/Kg K]
P4 Exhaust Pressure [kPa]
S1 Entropy at Exhaust [KJ/Kg K]
P5 Inlet Pressure [kPa]
H1 Enthalpy at inlet [KJ/Kg K]
T Thrust [N]
H2 Enthalpy in compressor [KJ/Kg K]
n
H3 Enthalpy at combustor [KJ/Kg K]
Speed [RPM]
l Fuel Flow [l/min]
Air mass flow rate [Kg/ sec]
H4 Enthalpy at Turbine [KJ/Kg K]
H5 Enthalpy at Exhaust [KJ/Kg K]
Discussion
From data obtained it was seen that when percentage position of throttle increased pressure and
temperature in the compressor, turbine and combustor increased. This happened because
increasing throttle position percentage led to more fuel and air entering the gas turbine thus
combustion increased and then there was higher temperature and pressure. Likewise, propeller
speed increased with increase of throttle position. More air flow results in increased combustion
and then more air-fuel mixture is converted to heat energy meaning more power is produced and
thus higher speed. This was so because more energy is produced when air-fuel mixture is burnt
and converted to mechanical power. As such, output shaft of the turbine and propeller rotate are
very high speed.
It can also be seen that increasing flow rate of air in the turbine leads to increased entropy.
However, the enthalpy decreases gradually in the turbine, combustor, and exhaust as the air flow
rate is increased. Conversely, compressor enthalpy increased when air flow rate increased.
CONCLUSION
From this lab experiment the gas turbine jet engine start-up, power down processes and data
logging were performed. In addition, its enhanced familiarity with gas turbine parts and working
principle and its control. Certain gas turbine parameters such as percentage throttle position and
air mass flow rate on the engine performance were analyzed. From this experiment it was learnt
that increasing the air-fuel mixture results to increased combustion rate and thus more heat
energy which is converted to mechanical energy that is used to drive turbine shaft and propeller
and enhance jet propulsion.
References
1. Moran, M.J., Shapiro, H.N., Boelter, D. D., & Bailey, M. B. (2010). Fundamentals of
engineering thermodynamics. John Wiley & sons.
2. Lab guideline manual.
3. Yunus A Cengel, Michael A. Boles. Thermodynamics an engineering approach. 5th
edition.