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Turbine Fuel System
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Mohd Ashraf Mohd Ismail
Laboratory Experiment 8
Name : Mohammed Ashraf Bin Mohammed Ismail
Student No: N0806406
Contact No: 98225529
Date Submitted:
Lab. : Turbine Fuel System
Course Instructor: Mr Roger Chua
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Table of Contents
ABSTRACT .................................................................................................................. 3
INTRODUCTION ......................................................................................................... 4
OBJECTIVES................................................................................................................ 5
EXPIREMENT PROCEDURE ..................................................................................... 6
DISCUSSION OF RESULT.......................................................................................... 7
Aircraft Fuel Systems ................................................................................................ 7 Engine Fuel Systems.................................................................................................. 9 Fuel Inerting............................................................................................................. 11
REFERENCE .............................................................................................................. 12
APPENDIX.................................................................................................................. 13
Introduction to Aerospace Engineering Lab 8
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Abstract
This lab work is concerned with the fuel systems that are commonly found on most
turbine engine system.
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Introduction
The airplane fuel system store and distributes fuel for use by engines and the auxiliary
power units. The system must have a means of safely holding the fuel, allowing
filling and draining of the tanks, preventing unwanted pressure buildups, protect from
contamination and assure a steady supply of fuel to the engines. Many portions of the
fuel system are operated automatically by a fuel management system that monitors
fuel quantities, fuel distribution in the tanks and component status. Fuel system can be
displayed on the Engine Indicating and Crew Alerting System (EICAS) by selecting
the fuel synoptic. The fuel system can signal fuel system flight conditions and/or
faults to the flight crew through EICAS and can record flight condition and faults in
the Central Maintenance Computer Systems (CMCS) for aid in maintenance.
The Fuel system is composed of four major subsystems:
• Storage – The storage subsystem consists of fuel tank ventilation systems, and
means to transfer fuel from tank to tank within the airplane.
• Distribution- The distribution subsystem consists of components (fuel pumps,
boots pumps, fuel filters) and tubing necessary to deliver fuel to the engine
and auxiliary power unit.
• Jettison – The Jettison subsystem consists of the components and fuel tubing
necessary to jettison (dump) fuel overboard through nozzles on the wingtips.
• Indicating – The Indicating subsystem contains components to provide fuel
quantity indication by electronics or mechanical means. Quantity
measurements determined by the indicating subsystem are used to
automatically control fuel feed, transfer, refueling, and jettison operations.
Indicating subsystem also contains components for indicating low fuel
pressure in the fuel feed and jettison subsystem pumps.
All these capabilities must be carried out without compromising the safety of
the aircraft or it’s occupants.
Introduction to Aerospace Engineering Lab 8
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Objectives
From the experiment we were able to :
I. To familiarize students with the functions of a typical turbine aircraft fuel system.
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Experimental Procedure
Procedure:
1. Turn master switch to the "on" position. 2. Fill wing tank by turning the "refill" switch to the "on" position. 3. Turn refill switch off when fuel quantity reaches the top of the fuel tank window. 4. Turn Transfer pump switch to the "on" position. Note the fuel transferring from the wing tank to the main tank. The fuel will continue to fill the main tank until the level reaches the high level switch of the fuel level transmitter. 5. Turn boost pump to the "on" position. 6. Open the firewall shutoff valve by moving the switch to the "open" position. Note the indicated fuel pressure. 7. Move the power lever to the increase position. Notice the fuel flow gauge increase and the fuel flowing into the "Turbine Engine Combustion Area". 8. The fuel is now flowing from the Main tank to the Combustion area and then draining into the holding tank. Allow the fuel to continue flowing, noting the fuel level of the main tank. When the level reaches the refill mark, the transfer pump will automatically cut on and refill the main tank. 9. With the transfer pump switch in the “ON” position, the transfer pump is in on automatic mode, refilling the main tank when needed. If the wing tank is allowed to run dry with the transfer switch on, after approximately 30 -‐ 40 seconds the "no transfer light" should illuminate and the transfer pump will shut down. 10. Refill the wing tank from the holding tank as needed. This system is a closed loop and the fluid from the "Combustion Area" drains back into the holding tank, and then can be pumped into the wing tank by the refill pump. SHUT DOWN PROCEDURE 1. Transfer all fuel to the holding tank located at the rear of the trainer. This is accomplished by operating the trainer and moving all of the fuel out of the wing and main fuel tanks to the combustion chamber. The fuel will gravity drain from the "Turbine Engine Combustion
1) Area" back into the holding tank.
2) Make sure all switches on the front panel are in the "down/off' position
3) . Disconnect AC power cord.
(NOTE: Storing fuel in the wing or main tank for an extended period of time will cause staining and discoloration of the clear tank walls)
Introduction to Aerospace Engineering Lab 8
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Discussion of Result
REPORT (1) Draw a schematic diagram of an aircraft (any aircraft type) fuel system. Explain the function of the various components used in the system.
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The schematic diagram previous page is from the aircraft Boeing 777-200/300 The fuel is distributed in 4 main tanks, two outboard reserve tank and a center-wing tank. A fuel vent systems provides positive venting to the atmosphere of all fuel tanks, fuel cells, thereby preventing excessive internal or external pressure. The engine fuel-feed systems consists of fuel lines, pumps and valves which distribute the fuel to the engines. This system includes all the tanks are interconnected by a fuel manifold such that fuel from any of the tanks can be delivered to any the engines Main fuel pumps deliver a continuous supply of fuel at the proper pressure during operation of the aircraft engine. Engine-driven fuel pumps must be able to deliver the maximum flow needed at high pressure to obtain satisfactory nozzle spray and accurate fuel regulation. The fuel-feed line from each tank is pressurisied by boost pumps. The distribution of fuel to the engines is controlled by electric motor driven slide valve in the fuel lines. Fuel Filters All gas turbine engines have several fuel filters at various points along the system. It is common practice to install at least one filter before the fuel pump and one on the high-pressure side of the pump. In most cases the filter will incorporate a relief valve set to open at a specified pressure differential to provide a bypass for fuel when filter contamination becomes excessive. Pressurizing and Drain (Dump) Valves The pressurizing and drain valve prevents flow to the fuel nozzles until sufficient pressure is reached in the main fuel control. Once pressure is attained, the servo assemblies compute the fuel-flow schedules. It also drains the fuel manifold at engine shutdown to prevent post-shutdown fires Fuel Shutoff Valves The engine fuel shutoff valve is installed in the main fuel supply line or tank outlet to the engine. It is controlled from the pilot's compartment. A fuel shutoff valve is usually installed between the fuel control unit and the fuel nozzles. When the throttle is placed in the closed position, this ensures positive shutoff of fuel to the engine. Fuel Heater
Fuel heater operates as a heat exchanger to warm the fuel. The heater can use engine bleed air, an air-to-liquid exchanger, or an engine lubricating oil, a liquid-to-liquid exchanger, as a source of heat. Fuel deicing systems are designed to be used intermittently
Introduction to Aerospace Engineering Lab 8
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(2) Draw a schematic diagram of an engine (any engine type) fuel system. Explain the function of the various components used in the system.
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Introduction to Aerospace Engineering Lab 8
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The main fuel systems is composed of several components, mounted in the airframe and on the engine. The common airframe components are the fuel tanks, fuel boot pump, fuel shutoff valve and the low-pressure fuel filter. The engine mounted components are main fuel pump, fuel filter, main engine control, fuel /oil heat exchanger, flow divider and fuel nozzles. The fuel system is can be divided into Low- and high pressure systems. The low pressure systems must supply the fuel to the engine at a suitable pressure, constant rate of flow and temperature to ensure satisfactory engine performance.
The fuel pump receives fuel from the Aircraft and pressurises it sufficiently.
Fuel Oil Heat Exchanger (FOHE) transfers the heat from the engine oil to the fuel to prevent ice formation in the fuel. Heat is transferred from the oil to the fuel in the core of the FOHE. It then proceeds to the IDG fuel/oil heat exchanger to warm the fuel further.
LP Fuel Filter removes contaminants from the fuel before passing the fuel flow meter.
Metering of fuel to the engine and basic engine control computations are performed in the hydromechanical control unit .The electrical and hydromechanical control units compute the fuel quantity to satisfy power requirements of the engine. from electrical inputs received from the following:
• EEC
• Overspeed Protection System (OPS)
• Cockpit engine master switch
Fuel Flow meter provides a signal of fuel flow to the EEC for onward transmission to the cockpit for display. It also provide information for calculation of fuel usage. The fuel flow metering system controls fuel flow to the engine
After the fuel control meter the fuel, the fuel then flow through the fuel flow transmitter before entering the engine oil cooler. The engine oil cooler use the fuel entering the engine to cool the oil and warms the fuel.
After exiting the oil cooler, fuel pass through the pressurizing and dump valve and into the fuel manifold where the high pressure fuel is brought to the fuel spray nozzles (FSNs). It is an assembly of flexible hoses at equal distances around the combustion outer case. The manifold distributes the fuel to the 20 FSNs that provide the necessary atomisation of fuel into the combustion chamber and is ignite and burn efficiently.
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3) As a result of the TWA 800 crash, what is the current FAA rule on fuel tank inerting? Explain the operation of a system in use for fuel tank inerting.
Significant emphasis has been placed on fuel tank safety since the TWA flight 800
accident in July 1996. NTSB determined that the "probable cause of the TWA flight
800 accident was an explosion of the center wing fuel tank (CWT), resulting from
ignition of the flammable fuel/air mixture in the tank.
Fuel tank inerting is the process of replacing potentially flammable gas space above
the fuel tank (ullage) with a non-flammable atmosphere. 2 main types of fuel inerting
1) Fuel scrubbing - Air, and particularly oxygen, readily dissolves in fuel. When a
commercial transport airplane takes off after fueling, the resulting change in altitude
causes a decrease in atmospheric pressure in the fuel tank. This decrease in pressure
allows for some of the air to escape solution and enter the ullage space of the fuel
tank. Fuel scrubbing is a process by which most of the oxygen dissolved in the fuel is
displaced with nitrogen. Fuel and nitrogen are combined through a series of nozzles in
a large container with the resulting combination having a very small amount of
oxygen in solution.
2) Ullage washing - Is a process that requires displacing the air in the fuel tank empty
space, also known as ullage, with nitrogen gas or nitrogen enriched air (NEA). Ullage
washing would be accomplished by providing the nitrogen or NEA to a supply line
that feeds a simple fuel tank gas supply manifold.
Under much contention this working group published a final report (2001 ARAC
Report) which recommended that no rule making actions be taken at this time and
stated that additional research and development was needed
Introduction to Aerospace Engineering Lab 8
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Reference
1) Fuel Tank Protection. Federal Aviation Administration
<http://www.fire.tc.faa.gov/systems/fueltank/intro.stm.> 6th October
2008.
2) Micheael J. Kroes, Willism A. Watkins, Frank Delp. “Aircraft
Maintenance & Repair”. Sixth Edition. Macmillan/McGrraw-
HillSchool Publishing Company, 1993.
3) Micheael J. Kroes, Thomas W. Wild, “Aircraft Powerplant” Seventh
Edition Macmillan/McGrraw-HillSchool Publishing Company, 1994.
4)
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Appendix
Right Side (From Front View)
Introduction to Aerospace Engineering Lab 8
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Fuel Tank Protection Significant emphasis has been placed on fuel tank safety since the TWA flight 800 accident in July 1996. After the accident, the NTSB determined that the "probable cause of the TWA flight 800 accident was an explosion of the center wing fuel tank (CWT), resulting from ignition of the flammable fuel/air mixture in the tank (NTSB Report). The NTSB further concluded that contributing factors to the accident were that the design and certification of the aircraft required only the preclusion of all potential ignition sources in order to prevent a fuel tank explosion. Following the accident, the Federal Aviation Administration (FAA) has issued numerous Airworthiness Directives and has enacted a comprehensive regulation to correct potential ignition sources (SFAR 88) in fuel tanks as well as conducting research into methods that could eliminate or significantly reduce the exposure of transport airplanes to flammable vapors. The latter has been in response to a new FAA policy that strives to eliminate or reduce the presence or consequences of flammable fuel tank vapors. This has included fuel tank inerting, which is commonly used by the military. Fuel tank inerting is the process of replacing potentially flammable gas space above the fuel tank (ullage) with a non-flammable atmosphere. However, the systems weight, resource requirements, and relatively low dispatch reliability have indicated that military fuel tank inerting systems would not be practical for application to transport airplanes. A fuel tank inerting working group was formed by the Aviation Rulemaking Advisory Committee (ARAC) in response to a task assigned by the FAA to evaluate a proposed rule that would require a reduction in flammability of some or all commercial transport fuel tanks. A previous ARAC working group (1998 ARAC Report) has stated that a potentially cost-effective method of fuel tank flammability reduction was ground-based inerting (GBI). The new working group was charged with examining fuel tank inerting methods to reduce or eliminate the flammability of all or some fuel tanks in the commercial transport fleet while developing regulatory text as well as determining the cost and benefit of the proposed rule change. Under much contention this working group published a final report (2001 ARAC Report) which recommended that no rule making actions be taken at this time and stated that additional reserach and development was needed. Since the inception of the 2001 ARAC WG the FAA has performed extensive research into the lower oxygen concentration (LOC) required to render a fuel tank ullage inert as well as the equipment and methods needed to develop a fuel tank inerting system. The Fuel Tank Protection Task has two research areas working closely together in an attempt to find practical solutions to this problem. The Fuel Flammability Research examines and defines the effects of various parameters on the flammable vapors existing within a fuel tank ullage, while the Fuel Tank Inerting Research is aimed at the validation of inerting requirements and the design of an economical and practical method of rendering inert the CWT of a commercial transport airplane. Fuel Tank Inerting The FAA has focused research to support two primary methods of fuel tank protection, both involving fuel tank inerting. Ground-based fuel tank inerting would involve some combination of fuel scrubbing and ullage washing with Nitrogen Enriched Air (NEA) while the airplane is on the
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ground. On-board fuel tank inerting would involve ullage washing during some or all aircraft operations with a system that generates NEA on the aircraft with the APU and/or engine bleed air. FAA research has evaluated Hollow Fiber Membrane (HFM) gas separation technology. HFM technology could be used to develop on-board inerting systems that are much lighter with greatly improved dispatch reliability than current military aircraft systems. Thus there is an interest in ground-based fuel tank inerting, with either airport supplied or on-board generated NEA, and also in an on-board inert gas generating system (OBIGGS) with the capability of providing NEA, as required throughout the ground/flight profile. OBIGGS also has the potential to improve commercial transport airplane fire safety as NEA generated on-board the aircraft could be used in an emergency for fire suppression in other parts of the aircraft. Ullage Washing and Fuel Scrubbing Ullage Washing Ullage washing is a process that requires displacing the air in the fuel tank empty space, also known as ullage, with nitrogen gas or nitrogen enriched air (NEA). NEA is a term used to describe low purity nitrogen (90-98% pure), generally generated via a gas separation process. Ullage washing would be accomplished by providing the nitrogen or NEA to a supply line that feeds a simple fuel tank gas supply manifold. Fuel Scrubbing Air, and particularly oxygen, readily dissolves in fuel. When a commercial transport airplane takes off after fueling, the resulting change in altitude causes a decrease in atmospheric pressure in the fuel tank. This decrease in pressure allows for some of the air to escape solution and enter the ullage space of the fuel tank. Since oxygen dissolves more readily than nitrogen, this can increase the oxygen concentration of the fuel tank ullage above ambient, although the total amount of gas evolving from the fuel is small. This can have a profound effect on the fuel tank oxygen concentration for both inert fuel tanks as well as fuel tanks with ambient air in the ullage space. Fuel scrubbing is a process by which most of the oxygen dissolved in the fuel is displaced with nitrogen. Fuel and nitrogen are combined through a series of nozzles in a large container with the resulting combination having a very small amount of oxygen in solution. The military has used fuel scrubbing to allow for fuel tank inerting systems to operate more effectively and to increase survivability to ballistic impact in combat.