Experiment Instructions
ET 796
Gas Turbine Jet Engine
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
ET 796
GAS TURBINE JET ENGINE
Experiment Instructions
Last modification by: Dipl.-Ing. J.Boxhammer
This manual must be kept by the unit.
Before operating the unit:
- Read this manual.
- All participants must be instructed on
handling of the unit and, where appropriate,
on the necessary safety precautions.
Version 0.1
Subject to technical alterations
i
ET 796
ii
GAS TURBINE JET ENGINE
ET 796
GAS TURBINE JET ENGINE
Table of Contents
1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Structure of safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
2.3 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Ambient conditions for the operating and storage location . . . . . . . . 12
3
Description of the device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Design of the trainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Device design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3 Process schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 Components of the trainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4.1
3.4.2
3.4.3
3.4.4
Gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Starting and ignition system . . . . . . . . . . . . . . . . . . . . . . . . .
Control elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
22
23
24
3.5 Measurement data acquisition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.5.1
3.5.2
Program installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Program operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.6 Setting up the gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.6.1
3.6.2
Checking the gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.7 Operating the gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.7.1
3.7.2
3.7.2.1
3.7.2.2
3.7.2.3
3.7.2.4
Preparations for start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bleeding the fuel lines with the kerosene start system . . . . .
Switch ECU to 6V kerosene start mode. . . . . . . . . . . . . . . .
Bleeding the fuel supply to the engine: . . . . . . . . . . . . . . . . .
Bleeding the fuel supply to the kerosene start system: . . . .
Testing and adjusting the fuel pump power . . . . . . . . . . . . .
32
33
33
34
35
37
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ET 796
GAS TURBINE JET ENGINE
3.7.3
3.7.4
3.7.5
Starting the gas turbine up . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Operating the gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Shutting down the gas turbine . . . . . . . . . . . . . . . . . . . . . . . 42
3.8 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.8.1
3.8.2
Glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Servicing the gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.9 Faults and troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.10 Decommissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4
Basic principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.1 The open gas turbine cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
5
4.1.1
4.1.2
4.1.3
Representation in the heat diagram . . . . . . . . . . . . . . . . . . . 49
Thermal efficiency (ideal) . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Specific work capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.1.4
Representation in the p-v diagram . . . . . . . . . . . . . . . . . . . . 52
4.1.5
Gas turbine jet engine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.1 Recording measurements and their subsequent evaluation . . . . . . . 55
5.1.1
5.1.2
5.1.3
5.1.4
5.1.4.1
5.1.4.2
5.1.4.3
5.1.4.4
6
Preparation for the experiment . . . . . . . . . . . . . . . . . . . . . . .
Conducting the experiment. . . . . . . . . . . . . . . . . . . . . . . . . .
Measured values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analysis of the experiment . . . . . . . . . . . . . . . . . . . . . . . . . .
Air mass flow and fuel mass flow . . . . . . . . . . . . . . . . . . . . .
Other characteristics of the gas turbine . . . . . . . . . . . . . . . .
Representation of the measured data in diagrams. . . . . . . .
Determining the fuel-air ratio . . . . . . . . . . . . . . . . . . . . . . . .
55
56
56
57
57
59
61
66
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.2 List of abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.3 List of formula symbols and units . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.4 List of symbols in the process schematic . . . . . . . . . . . . . . . . . . . . . 73
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ET 796
GAS TURBINE JET ENGINE
6.5 List of identification letters used in the process schematic . . . . . . . . 74
6.6 Tables and graphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
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6.7 Worksheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
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ET 796
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GAS TURBINE JET ENGINE
ET 796
1
GAS TURBINE JET ENGINE
Introduction
The ET 796 trainer is used to demonstrate and
study the function and behaviour of a gas turbine
in the model scale. Gas turbine plants are used to
generate mechanical and electrical energy:
– Driving generators in power plants
– Driving compressors and pumps in oil and gas
extraction
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Fig. 1.1
J85-GE-17A turbojet engine
from General Electric
– Propulsion of ships, locomotives and heavy
vehicles
– For aircraft propulsion with propeller and jet
engines
Gas turbines are always used where high concentration of power, low weight and quick startup are
required. Unlike piston engines, being turbomachines they allow high material throughputs with
small dimensions. This means lightweight yet
powerful drives can be constructed.
Fig. 1.2
JetCat gas turbine
Since the moving parts of a gas turbine only perform a rotary movement, with good balance it is
possible to achieve virtually vibration-free running. The loud noise emissions caused by the
high gas velocities and by contact with the atmosphere are a drawback.
Compared to steam turbines, gas turbines operate at higher temperatures but at lower pressures.
The high temperatures, especially in the area of
the gas turbine, require special heat-resistant
materials.
The gas turbine used in the trainer is a singleshaft gas turbine. All components required for
operation of the system are compactly combined
in a mobile rack.
1 Introduction
1
ET 796
GAS TURBINE JET ENGINE
The system has a simple construction and is
designed specifically for educational purposes.
The operation and display of all important process
parameters is summarised on a control panel.
The PC-based measurement data acquisition
with evaluation software allows online logging of
all relevant process variables and their graphical
representation.
Besides purely demonstrating the turbine's operational behaviour, it is also possible to undertake
qualitative studies such as determining the thrust
and other characteristics of the gas turbine.
Learning objectives / exercises
• Operating behaviour of a jet engine including
starting procedure
• Determining the specific thrust
• Determining the specific fuel consumption
• Determining the fuel-air ratio
2
1 Introduction
ET 796
GAS TURBINE JET ENGINE
2
Safety
2.1
Intended use
The unit is to be used only for teaching purposes.
2.2
Structure of safety instructions
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The signal words DANGER, WARNING or
CAUTION indicate the probability and potential
severity of injury.
An additional symbol indicates the nature of the
hazard or a required action.
Signal word
DANGER
Indicates a situation which, if not avoided, will result in
death or serious injury.
WARNING
Indicates a situation which, if not avoided, may result in
death or serious injury.
CAUTION
Indicates a situation which, if not avoided, may result in
minor or moderately serious injury.
NOTICE
2 Safety
Explanation
Indicates a situation which may result in damage to
equipment, or provides instructions on operation of
the equipment.
3
ET 796
GAS TURBINE JET ENGINE
Symbol
Explanation
Electrical voltage
Hazard area (general)
Hot surface
Wear ear defenders
No naked light
No smoking
Oxidizing
Flammable
Toxic
Notice
4
2 Safety
ET 796
2.3
GAS TURBINE JET ENGINE
Safety instructions
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The following instructions must be observed to
ensure safe and reliable operation of the device.
All persons concerned with the device, especially
students, must be familiarised with the safety
instructions.
The attached operating instructions for the model
gas turbine must be carefully observed. Gas turbines are delicate and sensitive machines even in
the model scale. Incorrect use or careless maintenance can quickly destroy the gas turbine. Therefore the operating instructions should be studied
carefully before the initial commissioning.
If any doubts arise, check with the manufacturer.
No liability can be accepted for damages resulting
from incorrect use.
WARNING
Electrical connections are exposed when the
control cabinet is open.
Risk of electrical shock.
• Before opening the control cabinet: Pull the
plug out.
• All work must be performed by trained electricians only.
• Protect the control cabinet from moisture.
2 Safety
5
ET 796
GAS TURBINE JET ENGINE
WARNING
The gas turbine housing, exhaust stack and
any of the gas turbine's exhaust ducts
become very hot during operation.
Risk of burns.
• Do not touch any parts
• Leave parts to cool down
WARNING
Exhaust jet is very hot (200...300°C).
Risk of burns.
• The area of the exhaust jet must be free of persons.
• Cordon off outlet area when operating as a jet
engine without exhaust gas outlet routing.
WARNING
Noise emissions > 130dB(A).
Risk of hearing damage.
• Wear suitable ear defenders.
6
2 Safety
ET 796
GAS TURBINE JET ENGINE
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WARNING
It should always be ensured that nobody is
present in the gas turbine's operating plane
when the turbine is operating.
Danger area.
• Either stand in front of or behind the gas turbine, but not to the side of it.
• Comply with the following minimum safety distances for a gas turbine model.
In front of the gas turbine: 1.0 m
To the side of the gas turbine: 12.0 m
Behind the gas turbine: 10.0 m
WARNING
Strong blow out force at the fan outlet. Loose
objects sucked in can be ejected at high speed.
• Before switching on: Ensure that there are no
loose items present in or behind the device.
WARNING
In the event of a jet fuel leakage, do not use an
open flame and avoid sparks.
Risk of fire.
• Do not switch any electrical consumers on or
off.
• Check the system for leaking fuel lines before
use.
• Wipe up spilled jet fuel. Note that cloths soaked
in jet fuel are a risk of spontaneous combustion
(ventilate well).
2 Safety
7
ET 796
GAS TURBINE JET ENGINE
WARNING
Do not allow any combustible materials to
come into contact with the hot exhaust pipe or
to get into the exhaust jet.
Risk of fire.
• A wide zone around the outlet area must be
kept free of combustible or heat-sensitive
materials.
• Minimum distance to combustible materials in
the direction of the exhaust gas stream: 4 m
WARNING
In the event of fuel leaks in the gas turbine, jet
fuel can ignite on the hot turbine housing.
Risk of fire.
• System must not be operated if fuel is leaking.
WARNING
Exhaust gases contain odourless carbon
dioxide and carbon monoxide. There is a risk
of suffocation or poisoning.
Carbon dioxide can suffocate and carbon monoxide can poison.
• Never operate the gas turbine without an
exhaust pipe.
• The exhaust pipe must lead outside under all
circumstances.
• Ensure adequate ventilation.
8
2 Safety
ET 796
GAS TURBINE JET ENGINE
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WARNING
Smoking or open flames when handling combustible fuels can lead to explosion or deflagration.
Possibility of severe injuries.
• No open flame
• No smoking
• Erect warning sign
• Comply with relevant statutory provisions when
transporting and storing fuels (kerosene, petroleum, etc.).
WARNING
Fire hazard due to overheating of the gas turbine.
The strong suction effect at the air inlet can cause
loose objects such as paper, cleaning cloths or
parts of clothing to be caught up by the air flow to
the air inlet opening during operation. This can
clog the intake screen and cause overheating and
fire in the gas turbine.
• Only operate the gas turbine with the safety
guard mounted.
• Do not store loose items where they can be
sucked in by the gas turbine.
• Do not operate the gas turbine unattended.
2 Safety
9
ET 796
GAS TURBINE JET ENGINE
WARNING
When handling fuel, drops of fuel could get
into the eyes.
Risk of injury to the eyes.
• Wear safety goggles
If fuel gets into the eyes:
• Rinse eyes immediately
• Seek immediate medical attention
NOTICE
Gas turbine must not draw in foreign bodies or
dust.
Dust is deposited in the turbine bearings and
destroys them. The intake area must be kept free
of loose objects.
NOTICE
A suitable fire extinguisher must be kept near the
unit during operation.
NOTICE
The system may not be operated unattended.
NOTICE
Only operate gas turbine with a mixture of turbine
oil and pure kerosene or petroleum. Unsuitable
fuel may cause overheating or residue formation.
10
2 Safety
ET 796
GAS TURBINE JET ENGINE
NOTICE
Fuel must be mixed with turbine oil to lubricate the
turbine bearings.
Only use suitable synthetic oils as specified in the
appendix.
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NOTICE
The gas turbine must be overhauled every 50
operating hours. This work must be carried out by
the gas turbine manufacturer JET-CAT.
NOTICE
If critical operating conditions (overspeed, excess
temperature, leaks, etc.) occur, always switch the
operating mode switch to "off" before doing anything else.
NOTICE
The system is not suitable for outdoor use. The
system must be operated in dry, dust-free and
well ventilated rooms. In particular, good ventilation must be ensured, since the system requires
over 800m3/h of air.
NOTICE
The gas turbine is designed to be electrically insulated on the thrust measuring table. There is a
potential of +12V at the gas turbine housing. It is
important to ensure that no electrically conductive
connection between the gas turbine and table is
established.
2 Safety
11
ET 796
2.4
GAS TURBINE JET ENGINE
Ambient conditions for the operating and storage location
• Enclosed space
• Free from dirt and humidity
• Level and fixed surface
12
2 Safety
ET 796
3
GAS TURBINE JET ENGINE
Description of the device
Electronic
Control
Unit
AUX channel
Throttle
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Throttle trim
Jet-tronic
remote GSU
Air
inlet
Exhaust gas outlet
1
2
3
4
5
6
7
8
9
10
11
12
Fig. 3.1
Compressor
Combustion chamber
Turbine
Jet nozzle
Thrust force sensor
Starter motor
Fuel tank
Fuel pump
Fuel filter
Fuel solenoid valve for start
Fuel solenoid valve
Operating unit
13
14
15
Electronic control unit
GSU
Glow plug
X1
P1
F1
F2
S1
T1
T2
T3
Thrust
Combustion chamber pressure
Air volumetric flow rate
Fuel consumption
Speed
Compressor temperature
Combustion chamber temperature
Gas turbine outlet temperature
View of the information panel
3 Description of the device
13
ET 796
GAS TURBINE JET ENGINE
The trainer includes a complete gas turbine system with the following sub-systems:
– Model gas turbine consisting of compressor
(1), combustion chamber (2), turbine (3) and jet
nozzle (4) with means for thrust measurement
(5).
– Fuel system consisting of fuel tank (7), fuel
pump (8), fuel filter (9), fuel solenoid valve (11)
and electronic control unit (13).
– Starter and ignition system with starter motor
(6), fuel solenoid valve for start (10) and glow
plug (15).
– Measurement and control instrumentation
with temperature, flow rate, speed and pressure measuring points and associated displays. This also includes safety elements such
as temperature and speed limiters.
3.1
Design of the trainer
All parts of the system are arranged on a table
frame. The fuel tank, pump with filter, solenoid
valve for start and the fuel solenoid valve for fuel
supply are located below the table top. The power
supply, the measurement data acquisition with
displays and the gas turbine control system are all
located in the control cabinet.
14
3 Description of the device
ET 796
3.2
GAS TURBINE JET ENGINE
Device design
17
16
15
14
13 12
11
10
9
8
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18
7
6
19
5
4
20
3
2
1
Fig. 3.2
1
2
3
4
5
6
7
8
9
10
Front view
Fuel tank
GSU (Ground Support Unit)
Operating unit
USB connector for the PC
Connection for the operating unit
Connection for the GSU
Emergency off switch
Main switch
Air volumetric flow rate F1
Turbine speed S1
3 Description of the device
11
12
13
14
15
16
17
18
19
20
Gas turbine outlet temperature T3
Combustion chamber pressure P1
Combustion chamber temperature T2
Fuel consumption F2
Compressor temperature T1
Thrust X1
Mixing tube
Gas turbine
Air inlet with safety guard and starter motor
Thrust force sensor
15
ET 796
GAS TURBINE JET ENGINE
3.3
Process schematic
12 Operating unit
14
Jet-tronic remote GSU
(Ground Support Unit)
AUX channel
Throttle
Throttle trim
13
ECU/
Electronic Control Unit
(in control cabinet)
10
7
Fuel tank
8
9
11
Fuel pump
2
Combustion chamber
Compressor
6
Starter motor
1
Turbine
3
Exhaust gas
outlet
4
Jet nozzle
Air inlet
Fig. 3.3
16
Process schematic for the gas turbine (see page 13 for part numbers)
3 Description of the device
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ET 796
GAS TURBINE JET ENGINE
3.4
Components of the trainer
3.4.1
Gas turbine
4a
Fig. 3.4
Gas turbine P80-SE
The model gas turbine forms the core of the
system. It consists of an axial turbine with directcoupled radial compressor and an annular combustion chamber. The turbine and compressor
form a compact unit with the bearing housing
positioned between them. This gas turbine was
originally used to power model aeroplanes. The
air drawn in is accelerated into the light metal diffuser housing (2) by the rapidly rotating impeller
3 Description of the device
17
ET 796
GAS TURBINE JET ENGINE
(1) (35000...115000 min-1). Here, the velocity of
the air is converted into pressure.
Fig. 3.5
Section model of a JetCat gas turbine
10
9
8
6
12
Fig. 3.6
18
5
4
11
7
12
3
2
1
14
15
13
Model gas turbine
3 Description of the device
ET 796
7
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Fig. 3.7
GAS TURBINE JET ENGINE
A portion of the air is branched off at the entrance
to the combustion chamber (3) and fed to the
flame tube (4) at the end. The liquid fuel enters the
evaporator pipes (5) from the rear. Here the fuel is
evaporated and mixed with the primary air and
combusted in the front part of the combustion
chamber. The secondary air cools the flame tube
from the outside. This is fed to the flame tube
through holes (6) in order to cool the extremely
hot combustion gases (about 2000°C) to the perTurbine glow plug with fuel line missible inlet temperature of 600...800°C.
(white) and electrical connection (red)
Connection for combustion
chamber pressure
measurement
14b
14a
14a
Turbine and compressor impeller are mounted
overhung on a shared shaft (11). The shaft is
guided in ball bearings (12) in the bearing housing. The bearings are cooled by the compressor
air and lubricated by a mist of fuel and turbine oil.
The electronics (13) for the starter motor (15),
temperature monitoring and speed measurement
(14, 14a, 14b) are housed under the front hood.
14b
Connection for
main fuel line
Fig. 3.8
A glow plug (7) fed by start fuel is used for ignition
at startup. From the combustion chamber, the
combustion gases flow into the turbine guide
vanes (8) and are accelerated to enter into the
axial impeller (9). In the impeller, the gases emit
some of their energy to the impeller in order to
drive the compressor. The gases are partially
expanded and cooled. They leave the jet nozzle at
about 600°C.
Connection for pressure measurement
at the intake nozzle
Intake nozzle with measurement
holes for measuring the speed
3 Description of the device
19
ET 796
GAS TURBINE JET ENGINE
The exhaust jet draws in additional secondary air
through the injector effect. This mixes with the
exhaust jet in the mixing tube (Fig. 3.10-9) and
decreases the outlet temperature.
The entire gas turbine with the thrust table (Fig.
3.10-3) is mobile (Fig. 3.10-5), so that the thrust of
the gas turbine can be measured via a force sensor (Fig. 3.9, Fig. 3.10-6).
Fig. 3.9
The quantity of drawn-in air is measured directly
at the air inlet using the intake nozzle below the air
Thrust table with force sensor
inlet (7).
9
8
1
1
2
3
4
5
Temperature sensor T3
Limit screw for the thrust table
Movable thrust table
Safety limit switch
Roller for storage
Fig. 3.10
20
2
7
3
6
7
8
9
4
5
6
Force sensor
Air inlet into the gas turbine
Gas turbine
Mixing tube as exhaust pipe
Gas turbine with mixing tube and force measuring device
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
5
1
Fig. 3.11
3
2
6
Gas turbine on the movably mounted thrust table
1Force sensor
2Safety limit switch
3Hose coupling for venting the main fuel line
4a - (see Fig. 3.4) Hose coupling for bleeding the start fuel line
5Combustion chamber pressure measuring line
6Inlet nozzle measuring line for measuring the intake air
3 Description of the device
21
ET 796
3.4.2
GAS TURBINE JET ENGINE
Fuel system
Kerosene or petroleum are used as fuel. Some
turbine oil is mixed into the fuel to lubricate the turbine bearing (ratio of 1:20). The turbine has a low
pressure system with an evaporator. An electric
fuel pump pumps the fuel into the turbine's evaporator tubes. The speed of the pump and thus the
amount of fuel is controlled and monitored by the
electronic control unit (ECU).
Fig. 3.12
A fuel solenoid valve prevents the flow of fuel in
an emergency. When starting up the gas turbine,
combustion is initiated via a separate start fuel
Fuel tank - fuel solenoid valve line and a glow plug.
and pump are located under
the table
4
1
2
3
Fig. 3.13
22
3
View under the table, under
the cover
1 - Fuel pump
2 - Fuel filter
3 - Fuel valves (start
and main valve)
4 - Combustion chamber
pressure sensor P1
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
3.4.3
Starting and ignition system
2
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
1
Fig. 3.14
DC motor (1) in the
disengaged state (2)
3 Description of the device
The automatic starting system consists of a powerful DC motor. This drives the compressor impeller via an automatic cone clutch. At a certain minimum speed of approximately 3000min-1, the
glow plug is turned on and the start fuel supplied
via a solenoid valve. The start fuel evaporates at
the glow plug and ignites. After successful ignition, the electric motor accelerates the turbine. At
a certain speed of approximately 5000min-1, the
main fuel supply is switched on and the start fuel
supply switched off. Once the sustaining speed
has been reached, the starter motor is automatically disengaged. The entire startup process is
monitored by speed and turbine temperature and
controlled electronically.
23
ET 796
3.4.4
GAS TURBINE JET ENGINE
Control elements
All indicators and connectors, as well as the main
switch and emergency stop switch are located on
the control cabinet. The USB connector, the connector for the operating unit and the connector for
the "Jet-tronic remote GSU" (Ground Support
Unit) display and programming unit are all located
in the lower part.
Fig. 3.15
24
Displays and controls on the control cabinet
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
The gas turbine is operated via the gas turbine's
operating unit. This houses the electronic control
unit's status indicators (1) and the controls
required for operation. The Throttle slider is used
to set the gas turbine's power output. The gas turbine can be turned off using the Throttle Trim
switch. The gas turbine is switched on and off
using the AUX Channel switch.
1
Fig. 3.16
3 Description of the device
The gas turbine's operating unit
25
ET 796
GAS TURBINE JET ENGINE
Connecting the (Jet-tronic) display and programming unit provides additional useful information
about the status of the gas turbine via the "Jettronic remote GSU" display. Connecting the Jettronic is not essential for operation of the gas turbine.
Fig. 3.17
26
Jet-tronic remote GSU (Ground Support Unit)
Fig. 3.18
Jet-tronic GSU from 01/09/2014
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
3.5
Measurement data acquisition
3.5.1
Program installation
Required for installation:
• A ready-to-use PC with USB port (for minimum
requirements see Chapter 6.1).
• G.U.N.T. CD-ROM
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
All components required to install and operate
the program are included on the CD-ROM provided by GUNT.
Installation procedure
NOTICE
The trainer must not be connected to the PC's
USB port while the program is being installed. The
trainer may only be connected after the software
has been successfully installed.
• Start the PC.
• Insert the G.U.N.T. CD-ROM.
• In the "Installer" folder, launch the "Setup.exe"
installation program.
• Follow the installation procedure on screen.
• Installation will run automatically after starting
it. The following program components are
installed onto the PC:
– Program for PC-based data acquisition.
– Driver routines for the "LabJack®" USB converter.
3 Description of the device
27
ET 796
GAS TURBINE JET ENGINE
• When the installation program has finished:
Restart the PC.
3.5.2
Program operation
• Select the program and run it via:
Start / Programs / G.U.N.T. / ET 796
• When you start the software for the first time
after installation you are prompted to select the
desired language for the program operation.
The language may be changed at any time in
the "Language" menu.
• Various pull-down menus are available for
other functions.
Fig. 3.19
Language selection
• For detailed instructions on use of the program
refer to its Help function. You can get to the
help function via the "?" pull-down menu and
selecting "Help".
Saved measurement data can be imported into a
spreadsheet program (e.g. Microsoft Excel) for
further processing.
28
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
3.6
Setting up the gas turbine
3.6.1
Checking the gas turbine
Before the gas turbine is operated for the first
time, it must be checked for transport damage and
misalignment.
If training or initial commissioning was also
ordered through G.U.N.T., then this check is carried out by G.U.N.T. employees.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
– Check all screws for tightness.
– Check all hoses for tightness.
– Check all cables for chafe points and tightness.
The power cable and hoses directly to the gas turbine are particularly important. Loose parts can
be sucked in during operation and cause severe
damage to the gas turbine.
– Check the ease of movement of the turbine
rotor. The rotor must rotate freely without
resistance and freely spin down after being
blown with compressed air.
If the rotor gives the impression of being stiff, this
could be caused by a foreign body in the compressor.
3 Description of the device
29
ET 796
3.6.2
GAS TURBINE JET ENGINE
Installation
Due to the high requirement for fresh air (approx.
800m3/h) the gas turbine may only be operated in
large, well-ventilated spaces. Lead the exhaust
gases directly to the outside or connect an
exhaust line. Avoid having an exhaust line longer
than 3 m due to high pressure losses. The
exhaust line should be sized so that no back pressure can occur. Operation in spaces with large
openings to the outside is recommended, so that
the exhaust gas can be blown into the open.
– A compressed air connection to blow through
the gas turbine is advisable.
– Due to the high sound level of the gas turbine
(>130 dB(A)) special sound insulation measures may be required.
– Secure the model from rolling away by engaging the roller brakes.
– To ensure access for maintenance and
servicing, there should be clearance of at least
1m around the trainer.
– If an exhaust line is used, this should have a
diameter of at least Ø300mm. The exhaust line
must be heat-resistant. Exhaust gases have a
temperature of up to 300°C. If there is a risk of
contact, the exhaust line must be protected by
safety guards accordingly. If heat radiation is
not desired, the exhaust line must be insulated
to be heat resistant. The exhaust line must not
be allowed to come into contact with combustible material. Do not use plastic brackets and
seals.
– It is also possible to work without an exhaust
line in open, well-ventilated halls with high ceil-
30
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
ings. In this case, it is essential that there are
no combustible materials in the region of the
exhaust jet.
– A licensed and certified fire extinguisher must
be placed near to the gas turbine.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
– Connect the electrical power supply. Plug the
USB cable provided for computer-based measurement data acquisition in to the ET 796
device and connect to the PC. See installation
instructions relating to the installation of hardware and software.
3 Description of the device
31
ET 796
GAS TURBINE JET ENGINE
3.7
Operating the gas turbine
3.7.1
Preparations for start
The following tasks must be performed before
starting the gas turbine:
– Check fuel level. If topping up the fuel level,
make sure the appropriate turbine oil is added
(see Page 69).
– Only use the highest purity kerosene or petroleum as fuel. Using poor quality fuel leads to
deposits forming in the turbine's evaporator
system, which in turn lead to malfunctions in
the combustion chamber.
– Only use fully synthetic oil as lubricant (see
Page 69)
– Connect the "Jet-tronic remote GSU" (Ground
Support Unit) on the control cabinet to the ECU
(Electronic Control Unit).
– Connect the operating unit on the control cabinet and adjust as follows:
• Throttle: down
• Throttle trim: Off
• AUX Channel: Off
– Switch on the main switch.
– Bleed the fuel line. For trouble-free operation,
make sure that there is no air in the fuel line
(see Chapter 3.7.2, Page 33).
– Check the operation of the indicators.
– The gas turbine is now ready for operation.
32
3 Description of the device
ET 796
3.7.2
GAS TURBINE JET ENGINE
Bleeding the fuel lines with the kerosene start system
Before the first start and whenever the kerosene
lines are empty or contain air bubbles (e.g. fuel
tank empty during operation), the system must be
bled.
3.7.2.1
Switch ECU to 6V kerosene start mode.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
(Already set by default)
– Switch off the main switch.
– If not already done, connect the "Jet-tronic
remote GSU" to the ECU on the lower left of the
control cabinet.
– Simultaneously press and hold the "Ignition" or
"Spool" and "Min/Max" on the "Jet-tronic
remote GSU".
– Switch on the main switch. (Keep the buttons
pressed!)
– After a short time, the Jet-tronic remote GSU
display shows:
Kerosene (6V- N)
Start activated
– Release the buttons; the ECU is now programmed for a kerosene start.
3 Description of the device
33
ET 796
3.7.2.2
1
Fig. 3.20
GAS TURBINE JET ENGINE
Bleeding the fuel supply to the engine:
2
Fuel line
hose coupling
1 - Hose
2 - Blue ring
3 - Connector
3
1. First remove the 4 mm main fuel line (Fig. 3.11,
Page 21, no. 3) from the gas turbine and lead
to a collecting tank. If this isn't done, the following procedure will flood the gas turbine with fuel
(-> risk of hot start).
Loosen the fuel lines:
Hold the blue ring on the hose coupling and pull
the hose.
2. Fill the fuel tank.
3. Connect the "Jet-tronic remote GSU" on the
control cabinet (ECU) and open the "Pump
TestVolt" parameter in the "Test Functions"
menu. (Press "Menu Select" and hold and then
scroll with the +/- buttons until "Test Functions"
is displayed. Now release the "Menu Select"
button. Now "Purge Fuel System" appears in
the display. Otherwise scroll through the Test
Functions menu with the + button until the display appears.
4. Now press the "Change Value" button to start
the pump (the pump power can be increased or
reduced with the +/- keys while holding the
"Change Value" button). Keep supplying fuel
until all air bubbles are pumped out of the pipe
system and fuel is coming out without any bubbles.
5. Reconnect the fuel line to the gas turbine. The
main fuel system has now been bled.
Connect the fuel lines:
Simply insert the hose into the hose coupling
and check it is firmly inserted by tugging slightly
on the hose.
34
3 Description of the device
ET 796
3.7.2.3
GAS TURBINE JET ENGINE
Bleeding the fuel supply to the kerosene start system:
1. First, bleed the fuel supply to the engine (see
Chapter 3.7.2.2, Page 34). The fuel tank must
be filled.
2. Disconnect glow plug connector. Failure to do
so will damage the seals due to the heat.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
3. Disconnect the start fuel line at the connector
(see Fig. 3.4, Page 17, no. 4a) before the kerosene igniter (-> transition between fuel hose
and Teflon hose) and drain into a collecting
tank. If this isn't done, the following procedure
will flood the gas turbine with fuel.
4. Connect the "Jet-tronic remote GSU" on the
control cabinet (ECU is in the control cabinet)
and open the "BurnerValve Test" parameter in
the "Test Functions" menu. (Press "Menu
Select" and hold and then scroll with the +/buttons until "Test Functions" is displayed.
Now release the "Menu Select" button. Then
use the "+" button to scroll through the Test
Functions menu until "BurnerValve Test" is displayed).
5. Now press the "Change Value" button to start
the pump with low power and to supply fuel to
the kerosene igniter (the pump runs at low
power, the kerosene igniter valve is pulsed, the
main fuel valve remains closed). Now supply
fuel until all air bubbles are pumped out of the
kerosene igniter's hose system and fuel is coming out without any bubbles.
6. Use the connector to re-establish the fuel connection to the kerosene igniter. Briefly supply a
3 Description of the device
35
ET 796
GAS TURBINE JET ENGINE
bit of fuel until the Teflon hose is also filled and
kerosene is present right at the kerosene
igniter. The fuel supply to the kerosene start
system has now been bled.
36
3 Description of the device
ET 796
3.7.2.4
GAS TURBINE JET ENGINE
Testing and adjusting the fuel pump power
When adjusting the amount of fuel, check and
adjust the hose line to the gas turbine's fuel supply, not the fuel supply to the kerosene start system.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
1. First remove the 4 mm main fuel line (Fig. 3.11,
Page 21, no. 3) from the gas turbine and lead
to a collecting tank. If this isn't done, the
following procedure will flood the gas turbine
with fuel.
2. The fuel tank should be full.
3. Connect the "Jet-tronic remote GSU" to the
control cabinet (ECU).
4. Press and hold the "Change Value" button.
Now turn on the trainer at the main switch and
release the "Change Value" button after 2 - 3
seconds. Now "Pump start volt." should appear
in the GSU display.
5. Now press the "Change Value" button. The
pump should run (solenoid valve for fuel supply
also opens) and the current pump start-up voltage should be shown in the bottom line of the
GSU display. The fuel should drip rapidly from
the hose or pour out slightly. If the fuel is not
running out of the hose as described, fuel
pump start-up voltage must be corrected.
6. Now adjust the fuel pump start-up voltage
using the +/- buttons until the fuel runs out of
the fuel line as described under point 5. Check
the set value from time to time by pressing the
"Change Value" button. After successfully
adjusting the value, save it with the "Manual" or
3 Description of the device
37
ET 796
GAS TURBINE JET ENGINE
"Set" button. The ECU stores the value and
returns to the RUN menu.
7. Reconnect the fuel line to the gas turbine.
38
3 Description of the device
ET 796
3.7.3
GAS TURBINE JET ENGINE
Starting the gas turbine up
Gas turbines are started up in a fixed start-up procedure. This is typical of all gas turbines. Differences are only due to varying degrees of automation. In the following outline, the sequence is
shown schematically over time.
Max. temperature
n1
T3
Min. temperature
Full load
Accelerate
Idling speed
Starter
Self-sustaining
speed achieved
On
Time
Turbine outlet temperature T3
Idle
Self-sustaining speed
Turbine speed n1
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Full load speed
Off
Starting fuel
Fuel
On
Off
On
Off
Fig. 3.21
Start-up procedure of a gas turbine
3 Description of the device
39
ET 796
GAS TURBINE JET ENGINE
It is useful to carefully read through and memorise
the description of the start-up procedure before
conducting the experiments.
In the experiments, the speed and temperature
curves are tracked on the gas turbine's "Jet-tronic
remote GSU" display and programming unit (see
JetCat gas turbine instructions).
The names of the controls refer to Chapter 3.4.4.
– To reset the gas turbine's control electronics,
switch off ET 796 at the main switch.
– Check carefully whether there is still unburned
fuel in the gas turbine. Unburned fuel can lead
to overheating and destruction of the gas turbine as a result of uncontrolled combustion.
If there is still fuel in the gas turbine, lift the
thrust table at the front so that the fuel can run
out of the back. Then blow the gas turbine dry
with compressed air and carefully wipe up with
a cloth.
– Switch AUX channel to "off".
– Switch Throttle Trim to "on".
Fig. 3.22
Fold the gas turbine to remove
remaining fuel
– Set Throttle to idle (min).
– Switch on ET 796 at the main switch.
– Switch AUX channel to "run". The three LEDs
flash in sequence.
– Start the automatic start-up process by moving
the throttle to full throttle (max).
40
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
Gas turbine automatic start process
– The starter motor brings the turbine to the starting speed (yellow LED is on).
– Starting fuel is added via the glow plug, so that
the gas turbine ignites. Ignition can be detected
by an increase in temperature and speed.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
– Main fuel valve opens (red LED on) and turbine
is ramped up to approximately 50 000min-1.
The temperature rises sharply.
– After a short time at 50 000min-1, the turbine is
automatically slowed to the idle speed of
35 000min-1. The throttle must be returned to
neutral. The green LED indicates readiness for
operation.
– The thrust of the gas turbine can now be
adjusted via the throttle.
3.7.4
Operating the gas turbine
NOTICE
The gas turbine may not be operated unattended.
From time to time, the indicators for speeds and
turbine outlet temperature must be checked.
• Speed and turbine outlet temperature are automatically monitored by the electronic control
unit.
The idle speed is 35 000min-1. The full load
speed should not exceed 120 000min-1.
3 Description of the device
41
ET 796
3.7.5
GAS TURBINE JET ENGINE
Shutting down the gas turbine
The gas turbine is shut down via the gas turbine's
AUX channel.
– Regular shutdown via the "Auto off" position.
The turbine runs at 50 000...60 000min -1 for a
short period. Then the fuel pump is shut off, the
combustion chamber extinguished and the turbine stops. To cool the turbine bearing, the
starter motor continues to run until a temperature of less than 100°C is reached. The green
LED flashes during this time.
– In an emergency, the gas turbine can also be
switched off via the AUX channel "Off" position.
– After cooling down the gas turbine, move AUX
channel to "Off".
For more information, see the instruction manual
from the gas turbine manufacturer.
42
3 Description of the device
ET 796
GAS TURBINE JET ENGINE
3.8
Maintenance
3.8.1
Glow plug
If there are problems starting up, check the glow
plug for damage, short circuit or dirt. A burnt-out
glow plug is detected and displayed by the electronic control unit. Replacing or loosening the
glow plug:
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
5
4
Fig. 3.23
3
2
1
Glow plug connector
1 - plug
2 - rubber connector
3 - spring
4 - cable
5 - fuel line
– Hold rubber connector and gently pull on the
cable to retract the spring in the rubber plug.
Then remove the rubber connector from the
glow plug.
– Disconnect the fuel line and unscrew the glow
plug by hand.
– Screw in the new glow plug and tighten by
hand.
NOTICE
Do not use a spanner. The thread of the glow plug
socket may be damaged.
– Replace fuel line and rubber connector.
3 Description of the device
43
ET 796
3.8.2
GAS TURBINE JET ENGINE
Servicing the gas turbine
The manufacturer recommends servicing the gas
turbine after 50 hours of operation. The turbine
bearings are replaced during this service.
Manufacturer of gas turbine model:
JetCat P80
Ing.Büro CAT M.Zipperer GmbH
Etzenberg 16
D-79129 Staufen, Germany
Tel.: +49 (0)7636-78030
Fax.: +49 (0)7636-7208
Website: www.cat-ing.de
44
3 Description of the device
ET 796
3.9
GAS TURBINE JET ENGINE
Faults and troubleshooting
This section describes any problems that may
occur with the system and their causes.
Gas turbine specific faults and the meaning of the
error messages can be found in the gas turbine
manufacturer's manual.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
NOTICE
Unburned fuel may still be in the gas turbine after
an interrupted start-up. This may combust in an
uncontrolled manner when the system is restarted
and damage the turbine due to overheating.
• Therefore when restarting after an interrupted
start, it must be ensured that there is no
unburned fuel in the gas turbine. Lift the thrust
table and gas turbine at the front so that the fuel
can run out of the back. The gas turbine should
then be blown with compressed air to remove
the remaining fuel.
• Carefully wipe up the fuel with a cloth.
3 Description of the device
45
ET 796
GAS TURBINE JET ENGINE
Gas turbine fails to start
No reaction with the AUX channel in the "Run" – Main switch not turned on
position
– No mains voltage
No ignition
– Conductive connection between gas turbine and
table
– Start fuel valve defective
– Start fuel line not connected to glow plug
– Glow plug defective
Ignition occurs, but start-up is interrupted at low speed
Flames at start-up
– Pump injecting too much fuel
– No fuel
Start-up interrupted at medium speed
(10 000...20 000 min-1).
Strong smoke emission
The starter motor does not reach its speed
– Clutch slipping => clean with alcohol
Operating malfunctions
Gas turbine stops
– No fuel
– AUX channel to Off or
Auto off
– Main switch off
– Throttle trim to off
– No mains voltage
3.10
Decommissioning
– Remove any fuel remaining in the gas turbine
by lifting the gas turbine up.
– Switch off the power supply at the main switch.
46
3 Description of the device
ET 796
4
GAS TURBINE JET ENGINE
Basic principles
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
The basic principles set out in the following make
no claim to completeness. For further theoretical
explanations, refer to the specialist literature.
Fig. 4.1
Engine from General Electric J85-GE-17A turbojet
Inlet
Compressor
Air inlet
Combustion chamber
Cold section
Fig. 4.2
Combustion
Exhaust outlet
Turbine
Warm section
Principle of a jet engine
4 Basic principles
47
ET 796
4.1
GAS TURBINE JET ENGINE
The open gas turbine cycle
The gas turbine trainer operates according to the
open thermodynamic cycle, in which the working
fluid is taken from the environment and fed back
to it again. In this case, the working fluid of air is
subjected to the following changes of state:
Fuel
2
– Adiabatic compression of the cold air with a
compressor (1) from ambient pressure p1 to
the pressure p2 and the associated temperature increase from T1 to T2.
3
1
Air
Fig. 4.3
4
Exhaust gas
Simple, open gas turbine
– Isobaric heating of the air from T2 to T3 by supplying heat. Heat input is achieved by burning
fuel with oxygen in the combustion chamber
(2).
– Adiabatic expansion of the hot air in a turbine
(3) from the pressure p2 to p1. The temperature
decreases from T3 to T4.
In a closed thermodynamic cycle, the working
medium would have to be re-cooled to the inlet
temperature T1. Even in an open cycle, the residual heat is dissipated to the environment.
The mechanical power extracted with the turbine
is used in part to drive the compressor and in part
to be available as useful power. Thus for example,
it is possible to operate a generator (4).
48
4 Basic principles
ET 796
4.1.1
GAS TURBINE JET ENGINE
Representation in the heat diagram
Representing the cycle in the heat chart, known
as a T-s diagram, is useful in order to be able to
better assess the conditions in the thermodynamic cycle. Here the temperature of the working
fluid is plotted over the specific entropy.
p2
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
T
Heat input
qin
3
Expansion
p1
2
Useful work
W
4
Compression
1
a
Heat output
qout
b
s
Fig. 4.4
T-s diagram of the gas turbine process
The heat quantities can be represented in the T-s
diagram as areas. The useful work results from
the difference of the input quantity of heat area
a,2,3,b and output quantity of heat area 4,b,a,1.
Using the T-s diagram, it is possible to examine
questions about the thermal efficiency and the
working capacity of the process. Both temperature conditions and the pressure ratio  = p 2  p 1
play a role here.
4 Basic principles
49
ET 796
4.1.2
GAS TURBINE JET ENGINE
Thermal efficiency (ideal)
The efficiency results from the ratio of the input
heat and mechanical work. Assuming a constant
heat capacity of the working fluid, for the thermal
efficiency we get:
T
1  th = 1 – -----1- = 1 – -----------(4.1)

– 1T2
-----------

With a mean value of  = 1 ,4 for air and diatomic
gases we get:
1
 th = 1 – -------------0,285

(4.2)
We can see that the efficiency only depends on
the compression ratio  . The highest temperature
in the process, the turbine inlet temperature T3,
has no effect on the thermal efficiency.
50
4 Basic principles
ET 796
4.1.3
GAS TURBINE JET ENGINE
Specific work capacity
For the specific work capacity the following relationship applies:
1  – c  T    0 ,285 – 1 
w eff = c p  T 3   1 – -------------p
1

0 ,285

(4.3)
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
We can see that, besides the compression ratio,
the intake and turbine inlet temperature also play
a role. The intake temperature is generally determined by the ambient conditions. The turbine inlet
temperature T3 should be chosen as high as possible. In practice it is limited by the temperature
resistance of the turbine blades. Consequently
the compression ratio is also a decisive factor.
The power output of the system is given by multiplication by the mass flow pushed through.
·
P eff = m  w eff
(4.4)
The relationships depicted here apply for a singleshaft system. They provide guidance for understanding the operating behaviour. For example,
the compression ratio is quadratically dependent
on the speed. At high speeds this yields a significantly higher system efficiency.
4 Basic principles
51
ET 796
4.1.4
GAS TURBINE JET ENGINE
Representation in the p-v diagram
The thermodynamic cycle can also be represented in the p-v diagram. This makes the compression and expansion process clearly visible.
Heat input qin
p
2
p2
3
Expansion
Compression
Useful work
W
1
p1
4
Heat output qout
v
Fig. 4.5
p-v diagram of the gas turbine process
The mechanical work can also be represented as
an enclosed area. In contrast to the T-s diagram,
in this case the areas represent mechanical work.
We can see that the specific volume of the gas
increases between 2 and 3 due to the input of
heat, thus decreasing the density. The turbine's
surplus useful power results from the fact that it
can process a larger volume at the same differential pressure as the compressor.
52
4 Basic principles
ET 796
GAS TURBINE JET ENGINE
4.1.5
Gas turbine jet engine
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
1
2
Fig. 4.6
Jet engine
In aircraft engines, above a certain airspeed it is
cheaper to use the exhaust jet directly for generating thrust. The simplest jet propulsion consists
of a single-shaft gas turbine (1) in an open thermodynamic cycle. The turbine's exhaust gases
are only partly used and still contain energy. They
are accelerated in a jet nozzle (2) and generate
the necessary momentum to propel the aircraft.
With an optimum nozzle configuration, the
exhaust gases are expanded to ambient pressure.
Using the principle of linear momentum, the thrust
can easily be calculated from the pushed through
mass flow and the velocities at inlet (c1) and outlet
(c2):
·
Ft = m   c2 – c1 
(4.5)
In doing so it should be noted that the thrust is a
vector quantity and only velocity components in
the direction of the thrust make a contribution.
4 Basic principles
53
ET 796
54
GAS TURBINE JET ENGINE
4 Basic principles
ET 796
5
GAS TURBINE JET ENGINE
Experiments
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
The selection of experiments makes no claims of
completeness but is intended to be used as a
stimulus for your own experiments.
The results shown are intended as a guide only.
Depending on the construction of the individual
components, experimental skills and environmental conditions, deviations may occur in the experiments. Nevertheless, the laws can be clearly
demonstrated.
5.1
Recording measurements and their subsequent evaluation
The measurements should only be taken while
the gas turbine is in the steady state. The following measured values are examples and are subject to large variations, which are also dependent
on the ambient conditions.
The measurement data can be recorded manually
or via computer-based measurement data acquisition. Five measurements were taken while
idling, at partial load and at full load.
5.1.1
Preparation for the experiment
– Prepare trainer for start-up.
(See
Chapter 3.5,
Chapter 3.6
Chapter 3.7)
5 Experiments
and
55
ET 796
5.1.2
GAS TURBINE JET ENGINE
Conducting the experiment
– Run the turbine in the five operating points of
idling, 20% partial load, 40% partial load, 60%
partial load and full load.
– Record the measured values either with or
without a PC
5.1.3
Measured values
Gas turbine experiment
Date:
10/04/2014
Ambient temperature Tamb in °C:
10
Air pressure pamb in mbar:
1020
Rel. humidity
65

in %:
Experiment no.:
1
2
3
4
5
Compressor outlet T1 in °C
22
40
63
78
101
Combustion chamber T2 in °C
980
938
931
956
1058
Turbine outlet T3 in °C
621
582
571
576
598
Combustion chamber pressure p in
bar (rel.)
0,08
0,32
0,63
0,90
1,36
Air throughput dV air/dt in L/s
·
Air mass flow rate m a in kg/s
11,6
49,0
96,7
150,5
231,7
0,015
0,061
0,121
0,188
0,290
Fuel consumption dV fuel/dt in L/h
·
Fuel mass flow m f in kg/s
6,2
10,9
15,4
19,1
25,1
Turbine speed n in min-1
35100
67000
87400
102200
119700
Thrust Ft in N
5,1
20,3
40,4
60,7
97,9
Notes
Idle
20% partial load
40% partial load
60% partial load
Full load
1 ,38  10
–3
2 ,42  10
–3
3 ,42  10
–3
4 ,24  10
–3
5 ,58  10
–3
Tab. 5.1
56
5 Experiments
ET 796
GAS TURBINE JET ENGINE
5.1.4
Analysis of the experiment
5.1.4.1
Air mass flow and fuel mass flow
·
The air mass flow m a in kg/s is calculated as follows:
 0 T 0  p amb
·
m a = -------------  -----------------------  Anzeige
(5.1)
1000 p 0  T amb
with the reference values under standard conditions:
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
Density at 20°C  0 = 1 ,199 kg  m
3
Temperature at 20°C in K T 0 = 293 K
Pressure at p 0 = 1 ,013 bar
under the experimental conditions:
Temperature at 10°C in K T amb = 283 K
Pressure at pamb = 1,020 bar
Summary of above formula
p amb
·
m a = 0 ,347  -------------  Anzeige
T amb
(5.2)
Here
Tamb is the ambient temperature in K,
pamb the ambient pressure in bar and
"Anzeige" (display) is the measured air volume
flow in L/s.
Based on the full load case we get:
1 ,020
·
m a = 0 ,347  ---------------  231 ,7 = 0 ,290 kg/s
283
5 Experiments
57
ET 796
GAS TURBINE JET ENGINE
·
The fuel mass flow m f is calculated at a display of
fuel consumption dV fuel/dt in L/h and a desired
·
fuel mass flow m f in kg/s as follows:
f
·
m f = -------------  Anzeige
3600
(5.3)
where  f in kg/dm³ is the density of the fuel at
15°C
Based on the full load case we get:
with a density of, for example,  f = 0 ,8 kg/dm
3
0,8 kg
L
–3
·
m f = ------------- ----------3-  25 ,1 --- = 5 ,58  10 kg/s
h
3600 dm
58
5 Experiments
ET 796
5.1.4.2
GAS TURBINE JET ENGINE
Other characteristics of the gas turbine
Calculation based on full load operation.
Specific thrust:
Ft
·
·
·
·
f t = -----· - where m = m a + m f  m a
ma
(5.4)
97 ,9 N
Ns
f t = ---------------------- = 338 ----------kg
kg
0 ,290 -----s
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Specific fuel consumption:
·
mf
b s = -----Ft
(5.5)
– 3 kg
5 ,58  10 -----s
– 5 kg
b s = ----------------------------------- = 5 ,70  10 ----------97 ,9 N
Ns
kg
b s = 0 ,205 -----------Nh
Thrust/weight ratio:
F
f G = -----t
G
(5.6)
G : Weight in kg
97 ,9N
N
f G = ------------------ = 7 ,20 -----13 ,6k g
kg
Output thermal power:
·
·
Qf = mf  Hi
(5.7)
·
kJ
– 3 kg
Q f = 5 ,58  10 ------  42580 ------ = 237 ,6kW
s
kg
Hi : Calorific value 42580 kJ/kg (formerly Hu)
5 Experiments
59
ET 796
GAS TURBINE JET ENGINE
Thermal efficiency (ideal):
1
1
- = 1 – ------------- th = 1 – -----------
–
1
0
,285
-----------


(5.8)
where  = 1,4
p (abs.) where  compression ratio  = ----------------------------p amb (abs.)
where pamb: Pressure before compression
p : Pressure after compression
1
- = 0 ,214
 th = 1 – ---------------------0 ,285
2 ,33
60
5 Experiments
ET 796
5.1.4.3
GAS TURBINE JET ENGINE
Representation of the measured data in diagrams
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The measured data can be displayed online and
saved with the PC-based measurement data
acquisition. Then the recorded measured values
can be processed with the Measurements Graph
part of the program. The *.dat files with the stored
measurement data are used as the basis of the
data.
Fig. 5.1
Gas turbine system diagram
The following measured values are contained in
the *.dat file: It is possible to process the data
using a text editor. The data can also be imported
and processed using a spreadsheet program
such as Excel.
1
Time
t in h:min:sec
2
Compressor outlet temp.
T1 in °C
3
Combustion chamber temp. T2 in °C
4
Turbine outlet temp.
T3 in °C
5
Turbine speed
n in min-1
4
Fuel consumption
dV_fuel/dt in L/h
5
Combustion chamber
pressure
p in bar (rel.)
6
Thrust
Ft in N
7
Air consumption
dV air/dt in L/s
The following figures show some measurement
results that have been recorded with the PCbased measurement data acquisition.
5 Experiments
61
ET 796
GAS TURBINE JET ENGINE
The following figure shows recorded measurement data in the "Measurements Graph" window.
The thrust of the gas turbine is shown as a function of the speed. The thrust increases disproportionately with the speed. There is almost no thrust
at idle speed. The measurements shown were
taken at intervals of 2s. The plotted charts were
measured at a P80 gas turbine with less thrust
and do not match the currently recorded measured values of Chapter 5.1.3. Nevertheless, the
laws can clearly be seen.
Fig. 5.2
62
Thrust of the gas turbine from start-up to 120 000 revolutions
5 Experiments
ET 796
GAS TURBINE JET ENGINE
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
The following figure shows the relationship
between fuel consumption and thrust.
Fig. 5.3
Fuel consumption as a function of thrust
5 Experiments
63
ET 796
GAS TURBINE JET ENGINE
The following figure illustrates the relationship
between air demand and thrust. The temperatures are also shown.
Fig. 5.4
64
Temperatures and the gas turbine's air demand as a function of thrust
T1 Compressor temp. in °C
T2 Combustion chamber temp. in °C
T3 Turbine outlet temp. in °C
dV_air/dt Air volumetric flow rate in L/s
5 Experiments
ET 796
GAS TURBINE JET ENGINE
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
The last diagram shows the combustion chamber
pressure over the speed. This results in a quadratic dependency.
Fig. 5.5
Combustion chamber pressure of the gas turbine from start-up to 120,000 revolutions
5 Experiments
65
ET 796
5.1.4.4
GAS TURBINE JET ENGINE
Determining the fuel-air ratio
The fuel-air ratio is determined from the quotients
of the actual amount of air taken in to the amount
of air required for stoichiometric combustion of the
fuel. The amount of air required for combustion of
kerosene is:
kg air
L min = 14 ,2 -------------kg fuel
It follows for the fuel-air ratio at full load:
kg
·
0,290 -----m
1
s
a
 = -----------  -----= 3 ,66
· - = --------------------------------------------------L min m
– 3 kg
f
14 ,2  5 ,58  10 -----s
(5.9)
The fuel-air ratio  of the combustion chamber is
nearer to the stabilised flame in gas turbines
 = 1. The secondary air increases the values up
to about 5, so that the temperature in the combustion chamber remains below 1600°C and below
1400°C when entering the turbine.
66
5 Experiments
ET 796
GAS TURBINE JET ENGINE
6
Appendix
6.1
Technical data
Dimensions
Length x Width x Height
Weight
1230 x 800 x 1330 mm
112 kg
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Power supply
Voltage
Frequency
Phases
Rated input (power)
Alternatives optional, see rating plate
Fuel
230 V
50 Hz
1
400 W
Mixture of kerosene (Jet-A, Jet A-1) or
petroleum with turbine oil
Density at 15°C
0,775...0,84 kg/m3
Exhaust stack
Volume at 1m distance (full load):
Pipe Ø 300 mm
approx. 130 dB(A)
Type
Gas turbine, open cycle
Gas turbine P80-SE
Design:
Radial compressor and axial turbine
Annular combustion chamber
Speed range:
35 000...120 000 (max.) min-1
Max. pressure ratio:
approx. 2,2
Max. fuel consumption:
approx. 0,4 L/min
Ignition and starting system
Special glow plug with starting fuel
Electric starter
6 Appendix
1,2 V
67
ET 796
GAS TURBINE JET ENGINE
WARNING
Smoking or open flames when handling combustible fuels can lead to explosion or deflagration.
Possibility of severe injuries.
• No open flame
• No smoking
• Erect warning sign
• Comply with relevant statutory provisions when
transporting and storing fuels (kerosene, petroleum, etc.).
Either kerosene (Jet-A1) or petroleum can be
used as fuel, to which is added approx. 5% oil,
special turbine oil (e.g. AeroShell 500 or Exxon
Turbine Oil).
Rule of thumb: 1 litre of oil to 20 litres of fuel
NOTICE
To prevent static charging of the fuel system during operation, an antistatic additive (from Jetcat,
product no. 61198- 00) can be added to the fuel.
NOTICE
Fully-synthetic two-stroke oils are not suitable and
should not be used.
68
6 Appendix
ET 796
GAS TURBINE JET ENGINE
Lubrication system
Oil-mist lubrication with oil-fuel mixture mixing
ratio 1:20.
Example for filling the fuel tank: 4,75L petroleum
and 0,25L turbine oil.
Recommended oil types:
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
AeroShell Turbine Oil 500/560 with the specification MIL-PRF 23699 Grade HTS or Mobil Jet 1.
Conditionally suitable:
Exxon Turbine Oil is suitable only for kerosene.
Not recommended:
Castrol TTS is not suitable, since it is not miscible
with the fuels.
Safety devices
Shutdown at
– Overtemperature at the turbine inlet
– Overspeed in the turbine
Instrumentation
Thermocouples and digital displays for measuring
the following temperatures:
6 Appendix
– Compressor outlet
0...1200°C
– Combustion chamber
0...1200°C
– Turbine outlet
0...1200°C
69
ET 796
GAS TURBINE JET ENGINE
Pressure sensors and digital display
– Combustion chamber pressure: 0... 2 bar
Mass flows
– Air inlet measuring nozzle with square root
extracting
pressure sensor and digital display:
0...500 L/s
– Fuel from the fuel pump
Control:
0...25 L/h
– Turbine digital revolution counter:
0...199999 min-1
Measurement data acquisition
Programme environment:
LabVIEW Runtime
System requirements:
PC with Pentium IV, 1GHz processor
Minimum 1024MB RAM
Minimum 1GB free
hard disk space
1 CD-ROM drive
1 USB port
Graphic card resolution
min. 1024 x 768 pixels, True Color
Windows Vista / Windows 7 / Windows 8
70
6 Appendix
ET 796
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
6.2
6.3
6 Appendix
GAS TURBINE JET ENGINE
List of abbreviations
Abbreviation
Meaning
ECU
Electronic Control Unit
GSU
Ground Support Unit
dV_fuel/dt
Fuel consumption
dV_air/dt
Air flow
·
Va
·
VF
List of formula symbols and units
Formula symbol Mathematical/physical value
Unit
bs
Specific fuel consumption
kg   N  s 
cp
Specific thermal capacity
kg   kg  K 
dV_fuel/dt
Fuel consumption
L/h
dV_air/dt
Air flow
L/s
ft
Specific thrust
N  s  kg
fG
Thrust/weight ratio
N/kg
F
Force
N
G
Weight
kg
Hi
Calorific value (i: inferior)
kJ/kg
Lmin
·
m
·
ma
·
mf
Stoichiometrically required amount of air
kga/kgf
Mass flow
kg/s
Air mass flow
kg/s
Fuel mass flow
kg/s, g/s
n
Speed
min-1
p
Pressure
bar
p0
Pressure at standard conditions
mbar, bar, Pa
pamb
Ambient pressure (atmospheric pressure)
mbar, bar, Pa
p
Pressure after compression
mbar, bar, Pa
qin
Specific heat input
J/kg
71
ET 796
72
GAS TURBINE JET ENGINE
Formula symbol Mathematical/physical value
Unit
qout
·
Qf
Specific heat output
J/kg
Output thermal power
W, kW
s
Specific entropy
J   kg  K 
Ft
Thrust
N
t
Time
h:m:s
T0
Temperature under standard conditions
°C, K
Tamb
Ambient temperature
°C, K
T1
Compressor temperature
°C, K
T2
Combustion chamber temperature
°C, K
T3
Turbine outlet temperature
°C, K
v
Specific volume
m3/kg
w
Specific useful work
J/kg
weff
Specific work capacity
J/kg
 th
Thermal efficiency
%

Isentropic exponent
-

Fuel-air ratio
-

Pressure ratio
-
0
Density under standard conditions
kg/dm3

Relative humidity
% RH
Index
Explanation
a
Air
amb
Ambient
eff
Effective
in
fed in
out
emitted
t
Thrust
theo
theoretical
6 Appendix
ET 796
6.4
GAS TURBINE JET ENGINE
List of symbols in the process schematic
Symbol
Description
Fuel pump
Fuel tank
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
Filter
Motor
Fuel valve
Combustion chamber
Compressor
Turbine
Measuring nozzle
6 Appendix
73
ET 796
6.5
GAS TURBINE JET ENGINE
List of identification letters used in the process schematic
Identification
letter
Description
Equipment and machinery
B
Container, tank, hopper, silo
M
Electric motor
P
Pump
V
Compressor, vacuum pump, fan
Fittings
V
Tab. 6.1
Identification
letter
Identification letters for equipment, machinery, fittings and pipes
Measurand or other input variable,
actuator
as first letter
as supplementary
letter
Processing
as subsequent letter
(sequence I, R, C)
X
Force
P
Pressure
F
Flow rate, flow capacity
S
Velocity, speed, frequency
Circuit, flow control,
logic control
T
Temperature
Measuring transducer
function
Tab. 6.2
74
Valve, general
Ratio
Identification letter for measurement points
6 Appendix
ET 796
6.6
GAS TURBINE JET ENGINE
Tables and graphs
Unit
mm3
cm3
L
m3
1mm3
1
0,001
0,000001
0,000000001
1cm3
1.000
1
0,001
0,000001
1L
1.000.000
1.000
1
0,001
1m3
1.000.000.000
1.000.000
1.000
1
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 08/2014
Tab. 6.3
Conversion table for units of volume
Unit
L/s
L/min
L/h
m3/min
m3/h
1L/s
1
60
3600
0,06
3,6
1L/min
0,01667
1
60
0,001
0,06
1L/h
0,000278
0,01667
1
0,00001667
0,001
1m3/min
16,667
1000
0,0006
1
60
1m3/h
0,278
16,667
1000
0,01667
1
Tab. 6.4
Conversion table for units of volume flow
Unit
mbar
Pa
hPa
kPa
mm WC *
1bar
1
1.000
100.000
1.000
100
10.000
1mbar
0,001
1
100
1
0,1
10
1Pa
0,00001
0,01
1
0,01
0,001
0,1
1hPa
0,001
1
100
1
0,1
10
1kPa
0,01
10
1.000
10
1
100
1 mm WC *
0,0001
0,1
10
0,1
0,01
1
Tab. 6.5
6 Appendix
bar
Conversion table for units of pressure
* rounded figures
75
ET 796
6.7
GAS TURBINE JET ENGINE
Worksheets
Gas turbine experiment
Date:
Ambient temperature Tamb °C:
Air pressure pamb in mbar:
Rel. humidity
Experiment no.:
1
2

in %:
3
4
5
Compressor outlet T1 in °C
Combustion chamber T2 in °C
Turbine outlet T3 in °C
Combustion chamber pressure p in
bar
Air throughput dV_air/dt in L/s
· in kg/s
Air mass flow m
a
Fuel consumption dV_fuel/dt in L/h
· in g/s
Fuel mass flow m
f
Turbine speed n in min-1
Thrust Ft in N
Notes
Tab. 6.6
76
6 Appendix