Fundamentals eJAMF Module 15.11 Gas Turbine Engine/Fuel System ATA 73
EASA Part-66
A EJAMF M15.11 A E
Issue: 21.10.2008 Author: SwD For Training Purposes Only LTT 2006
Training Manual
For training purposes and internal use only. by Lufthansa Technical Training (LTT).
Copyright
LTT is the owner of all rights to training documents and training software. Any use outside the training measures, especially reproduction and/or copying of training documents and software − also extracts there of − in any format all (photocopying, using electronic systems or with the aid of other methods) is prohibited. Passing on training material and training software to third parties for the purpose of reproduction and/or copying is prohibited without the express written consent of LTT. LTT. Copyright endorsements, trademarks or brands may not be removed. A tape or video recording of training courses or similar services is only permissible with the written consent of LTT. LTT. In other respects, legal requirements, especially under copyright and criminal law, apply. Lufthansa Technical Training Dept HAM US Lufthansa Base Hamburg Weg beim Jäger 193 22335 Hamburg Germany Tel: el: +49 (0) (0)40 5070 5070 252 2520 Fax: Fax: +49 +49 (0)4 (0)40 0 5070 5070 4746 4746 E-Mail:
[email protected] [email protected] LH.DE www.Lufthansa-Techn www.Lufthansa-Technical-Training.com ical-Training.com Revision Identification:
The date given in the column ”Issue” on the face of this cover is binding for the complete Training Manual. Manual. Dates and author’s ID, which may be given at the base of the individual pages, are for information about the latest revision of that page(s) only.
Training Manual
For training purposes and internal use only. by Lufthansa Technical Training (LTT).
Copyright
LTT is the owner of all rights to training documents and training software. Any use outside the training measures, especially reproduction and/or copying of training documents and software − also extracts there of − in any format all (photocopying, using electronic systems or with the aid of other methods) is prohibited. Passing on training material and training software to third parties for the purpose of reproduction and/or copying is prohibited without the express written consent of LTT. LTT. Copyright endorsements, trademarks or brands may not be removed. A tape or video recording of training courses or similar services is only permissible with the written consent of LTT. LTT. In other respects, legal requirements, especially under copyright and criminal law, apply. Lufthansa Technical Training Dept HAM US Lufthansa Base Hamburg Weg beim Jäger 193 22335 Hamburg Germany Tel: el: +49 (0) (0)40 5070 5070 252 2520 Fax: Fax: +49 +49 (0)4 (0)40 0 5070 5070 4746 4746 E-Mail:
[email protected] [email protected] LH.DE www.Lufthansa-Techn www.Lufthansa-Technical-Training.com ical-Training.com Revision Identification:
The date given in the column ”Issue” on the face of this cover is binding for the complete Training Manual. Manual. Dates and author’s ID, which may be given at the base of the individual pages, are for information about the latest revision of that page(s) only.
g n i n i a r T l a c i n h c e T a s n a h t f u L
L N O S E S O P R U P G N I N I A R T R O F
M15 GAS TURBINE ENGINE
eJAMF Gas Turbine Engine
MODULE 15
M15.11 FUEL SYSTEM
g n i n i a r T l a c i n h c e T a s n a h t f u L
M15.11 FUEL SYSTEMS (ATA 73) ENGINE FUEL DISTRIBUTION
MODULE 15
ENGINE FUEL DISTRIBUTION INTRODUCTION On an aircraft we distinguish between the primary fuel system, which stores the fuel and the secondary fuel system, which is on the engine. Here we will only talk about the secondary fuel system. One purpose of this system is to supply the fuel to the combustion chamber, and the other main purpose is to control the quantity of fuel necessary for all operating conditions of the engine. The engine fuel system can be split into 2 subsystems: the fuel distribution subsystem and the fuel control subsystem. The engine fuel distribution subsystem has 3 main tasks: First it has to safely supply the fuel from the aircraft fuel system to the combustion chamber. The second task is to pressurize the fuel sufficiently so that it can be vaporized in the combustion chamber. The third task of the distribution system is to heat the fuel. This makes sure that fuel flow to the fuel nozzles is not blocked by ice build−up.
! Y L N O S E S O P R U P G N I N I A R T R O F
eJAMF Gas Turbine Engine
g n i n i a r T l a c i n h c e T a s n a h t f u L
M15.11 FUEL SYSTEMS (ATA 73) ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 1
Fuel Distribution System Purpose
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
MODULE 15 DISTRIBUTION LAYOUT Here you can see a simplified engine fuel distribution system. This system usually starts directly behind the low pressure fuel shut-off valve. This valve feeds the fuel into the main fuel supply line, which runs from the wing to the engine accessory gearbox where you can find the next component of this system. This is the low pressure fuel pump. The low pressure fuel pump increases the fuel pressure that comes from the tank boost pumps. The fuel from the low pressure pump then enters the oil cooler. This component has a dual function. The cold fuel cools the oil of the engine lubrication system and by this process the fuel is heated to a temperature above the freezing point of water. This prevents ice particles coming from the fuel tanks and blocking the fuel filter. So this is the reason why the fuel filter is located downstream of the oil cooler. It is needed to protect the following components in the engine fuel system. The next component behind the fuel filter is the high pressure fuel pump. This pump increases the fuel pressure to the high level needed for proper fuel vaporization in the combustion chamber. It is always equipped with a pressure relief valve, which protects the components in the high pressure fuel system against overpressure. The fuel from the high pressure fuel pump then enters the fuel control unit. The fuel control unit meters the fuel that is needed for combustion. It is also responsible for supply and shut-off of fuel to the fuel nozzles at the combustion chamber.
! Y L N O S E S O P R U P G N I N I A R T R O F
eJAMF Gas Turbine Engine
The fuel control unit needs some of the high pressure fuel as servo pressure to operate the internal control mechanisms. To be sure that this servo fuel is absolutely free of ice, some engines have an additional servo fuel heater.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
Fuel Nozzles
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 2
Fuel Distribution System
g n i n i a r T l a c i n h c e T a s n a h t f u L
! Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15 Distribution Layout cont. When the fuel leaves the fuel control unit, it has to pass through the fuel flow transmitter. The fuel flow transmitter measures the actual fuel flow and transmits signals to the cockpit for the fuel flow and fuel used indication. Note, that all the components of the fuel distribution system, from the LP fuel pump to the fuel flow transmitter, are in the area of the accessory gearbox at the engine. From the fuel flow transmitter the fuel is then routed to the fuel manifold, which distributes the fuel to the individual fuel nozzles on the combustion chamber.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
Fuel Nozzles
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 3
Fuel Distribution System
g n i n i a r T l a c i n h c e T a s n a h t f u L
! Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15 Distribution Layout cont. Some engines have the oil cooler downstream of the high pressure pump, as shown in this example. This arrangement has the advantage that it requires less external fuel lines, because the low pressure pump and the high pressure pump are usually in one housing, but the danger of fuel leaks in the oil cooler is much higher than in a low pressure system.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 4
Oil Cooler in High Pressure System
g n i n i a r T l a c i n h c e T a s n a h t f u L
! Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15 DISTRIBUTION OPERATION When the fuel boost pumps in the tanks are on and the LP fuel shut-off valve is open, the fuel flows from the tank to the low pressure stage of the engine fuel pump. This low pressure fuel pump increases the fuel pressure from the tanks up to approximately 175 psi and supplies the fuel across the oil cooler and fuel filter to the high pressure stage of the fuel pump. The pressure increase by the low pressure fuel pump is necessary so that the high pressure stage does not have to draw the fuel from the tank by suction. The low pressure fuel pump is needed to prevent cavitation at the inlet of the high pressure fuel pump. At maximum engine speed the high pressure fuel pump increases the fuel pressure to approx. 900 psi. At this pump an overpressure relief valve is needed to prevent damage to the following fuel system components. The overpressure relief valve usually opens when, at a malfunction, the pressure reaches approx. 1250 psi. At this point it releases some fuel back to the inlet port of the high pressure fuel pump. Fuel from the high pressure fuel pump then flows to the metering section of the fuel control unit. Note, that the pump always supplies more fuel than is needed for combustion. The metering section lets only the metered fuel pass to the fuel nozzles. The fuel that is not needed returns to the fuel pump by the bypass return line.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
Fuel Nozzles
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 5
Distribution System Operation
g n i n i a r T l a c i n h c e T a s n a h t f u L
! Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15 Distribution operation cont. On some engines you find that this bypass fuel is used to cool the IDG oil cooler, as shown in this example. When the bypass fuel passes through the IDG oil cooler, it takes the heat from the IDG oil. In low engine power conditions the hot bypass return fuel heats up the fuel from the low pressure pump too much, so that the engine oil can not be cooled sufficiently. In this situation the bypass return fuel is fed back to the fuel tank by the fuel recirculation system. Some cold fuel from the low pressure stage is added to the hot bypass fuel so that the fuel that enters the tank is not too hot.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS ENGINE FUEL DISTRIBUTION
eJAMF Gas Turbine Engine
MODULE 15
Fuel Nozzles
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 6
Fuel Recirculation
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
MODULE 15
HYDROMECHANICAL FUEL CONTROLS INTRODUCTION The fuel control unit of an engine is usually mounted to the engine fuel pump on the accessory gearbox. On most turbofan engines the fuel control unit is a hydromechanical component. In a hydromechanical fuel control unit all the control functions are done by fluid pressures and mechanical components. The engine manufacturers use many different names for their fuel control units to point out special tasks and capabilities of these components. You can find names like main engine control (MEC) or fuel flow regulator, but to avoid confusion the name fuel control unit is used throughout this lesson.
! Y L N O S E S O P R U P G N I N I A R T R O F
eJAMF Gas Turbine Engine
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 7
Fuel Control Units
g n i n i a r T l a c i n h c e T a s n a h t f u L
! Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
eJAMF Gas Turbine Engine
MODULE 15 Introduction cont. There are 2 different types of fuel control units: speed governed fuel control units, which you usually find on older engine types, or constant thrust fuel control units used on more modern turbofan engines. Speed governed fuel control units mainly use the N2 demand signal and the N2 speed feedback signal for steady state fuel metering. Constant thrust fuel control units use similar signals like the speed governed fuel control units, and they additionally use thrust feedback signals like N1 speed, ambient pressure, and temperature signals.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 8
Types of Fuel Control Units
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
MODULE 15 Introduction cont. You can see that this fuel control unit has many pipes and push-pull cables connected to it. Some of them are needed to transmit the throttle demand signal, the temperature signal, the pressure signal, and the speed feedback signals for fuel metering, and others are needed to control the engine compressor. The thrust lever signal is usually a mechanical deflection of a small power lever at the fuel control unit. This is either done by a rack and pinion transmission or by rods and levers. The N2 speed feedback signal is usually transmitted via a mechanical driveshaft from the main fuel pump. Some fuel control units even get N1 speed feedback signals. This signal is a fuel pressure signal which comes from a hydromechanical N1 speed sensor. The temperature signals like CIT or fan inlet temperature come from hydromechanical temperature sensors. These temperature sensors convert the air temperatures to fuel pressure signals. The fuel control unit receives pressure signals like CDP or ambient pressure via air sense lines. Pressure sensors in the fuel control unit convert the pressure signals into mechanical signals. So in summary hydromechanical fuel control units use hydraulic, mechanical, and pneumatic signals for their operation.
! Y L N O S E S O P R U P G N I N I A R T R O F
eJAMF Gas Turbine Engine
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 9
Signals for the Fuel Control Unit
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
MODULE 15 FUEL CONTROL UNIT ORGANIZATION To help you to understand the operation of a fuel control unit we can split it into 2 major sections: the fuel metering section, and the computing section. The computing section can be further split into a governing section, and a limiting section. These 3 main sections of course are not individual chambers inside the housing of the fuel control unit. They represent the main tasks of a fuel control unit. These are: fuel metering, power control, and engine protection. The metering section makes sure that the necessary fuel gets to the fuel nozzles and all the fuel, that is not needed for combustion, returns to the fuel pump. The governing section makes sure that the selected power is controlled. The limiting section of the fuel control unit monitors the governing section and makes sure that the engine always operates within safe limits.
! Y L N O S E S O P R U P G N I N I A R T R O F
eJAMF Gas Turbine Engine
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS HYDROMECHANICAL FUEL CONTROLS
eJAMF Gas Turbine Engine
MODULE 15
! Y L N O S E S O P R U P G N I N I A R T R O F
Figure 10
Fuel Control Unit Organization
g n i n i a r T l a c i n h c e T a s n a h t f u L
Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS FADEC SYSTEM
eJAMF Gas Turbine Engine
MODULE 15
FADEC SYSTEM INTRODUCTION The term FADEC is an abbreviation for ’Full Authority Digital Engine Control’. As the name indicates, in a FADEC system a digital computer has full authority over the engine control functions. The digital computer is the heart of the FADEC system. It is usually named the electronic control unit (ECU) or on other engines it is named the electronic engine control (EEC). To avoid confusion, we use the term ECU throughout this segment. The second main component of the FADEC system is the fuel metering unit (FMU). This component is also named the hydromechanical unit, or HMU on other engines. To avoid confusion, we use the term FMU throughout this segment. The terms FMU and HMU do not have a letter “C”. This indicates that the FMU cannot control. It only receives orders from the ECU to move the fuel metering valve. Engines with a FADEC system do not have a hydromechanical fuel control unit installed. You usually find the electronic control unit on the fan stator case of the engine. The fuel metering unit is at the same location as the fuel control unit on older engines. To operate correctly the electronic control unit needs the demand signal from the thrust lever in the cockpit. It also needs to know the engine speeds and all important air temperatures and air pressures in the engine, and it certainly needs electrical power supply for its operation. This power supply either comes from the aircraft, or it can also come from a small permanent magnet alternator on the engine accessory gearbox. The ECU also needs a feedback signal about the opening condition of the fuel metering valve.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS FADEC SYSTEM
eJAMF Gas Turbine Engine
MODULE 15
Y L N O S E S O P R U P G N I N I A R T R O F
Figure 11
ECU & FMU Location
g n i n i a r T l a c i n h c e T a s n a h t f u L
Y L N O S E S O P R U P G N I N I A R T R O F
FUEL SYSTEMS FADEC SYSTEM
eJAMF Gas Turbine Engine
MODULE 15 Introduction cont. The ECU can fulfil many tasks in addition to fuel metering and engine limit protection. It performs full power management and gives optimum thrust control for all operating conditions. It also controls other engine subsystems like the compressor stall protection system, the turbine and compressor clearance control system, the thrust reverser system, the engine starting system, and the engine indication system. With all the data that the ECU receives, it permanently monitors the engine operation and the important system components and gives fault messages to the centralized aircraft maintenance computer to indicate faulty components. On some aircraft there are so-called engine interface units installed. These EIUs transmit the data between the FADEC system and the aircraft. They also control the power supply from the aircraft to the ECU. A typical FADEC system has an electronic control unit, a fuel metering unit, many electrical sensors on the engine and many control possibilities for other engine sub systems. The FADEC system is a centralized computer with all necessary sensors which controls the engine and all its important sub systems.
g n i n i a r T l a c i n h c e T a s n a h t f u L
FUEL SYSTEMS FADEC SYSTEM
eJAMF Gas Turbine Engine
MODULE 15
Y L N O S E S O P R U P G N I N I A R T R O F
Figure 12
FADEC System
EJAMF M15.11 A E
TABLE OF CONTENTS
M15.11 FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . .
1
ENGINE FUEL DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DISTRIBUTION LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . DISTRIBUTION OPERATION . . . . . . . . . . . . . . . . . . . . . .
2 2 4 10
HYDROMECHANICAL FUEL CONTROLS . . . . . . . . . . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FUEL CONTROL UNIT ORGANIZATION . . . . . . . . . . . .
14 14 20
FADEC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22 22
TABLE OF CONTENTS
EJAMF M15.11 A E
TABLE OF FIGURES Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure
1 2 3 4 5 6 7 8 9 10 11 12
Fuel Distribution System Purpose . . . . . . . . . . . . . . . . . . . . . . . . Fuel Distribution System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Distribution System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oil Cooler in High Pressure System . . . . . . . . . . . . . . . . . . . . . . Distribution System Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Recirculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Control Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Fuel Control Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Signals for the Fuel Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Control Unit Organization . . . . . . . . . . . . . . . . . . . . . . . . . ECU & FMU Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FADEC System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 5 7 9 11 13 15 17 19 21 23 25
TABLE OF FIGURES
TABLE OF FIGURES
