APU
Transport Aircraft
Features APU
APIC APS3200 APU for Airbus 318/319/320/321
The main objective aircraft APU is to provide energy to start the main engines. Turbine engines have large rotors heavy to be accelerated a high rotational speed to ensure sufficient air compression for self-sustaining operation. This process takes much more time and requires much more energy from a reciprocating engine. Small turbine engines are usually started by an electric motor, while large turbine engines that are usually started by a turbine engine air. Whether the starter is electric, pneumatic or hydraulic, however, the amount of energy required is much greater than what could be achieved by a storage device (battery or air tank) a size and weights.
An APU solves this problem by turning on the device in two stages. First, the APU is started by an electric motor or hydraulic, with power supplied by a battery, accumulator or external power source (power unit on the ground). After the APU accelerates to full speed, it can provide an amount far more important to start the main engines of the aircraft, either turning an electric generator or hydraulic pump, or by supplying compressed air to the air turbine starter motor.
GEA also several auxiliary functions. electric and pneumatic systems are used to operate the heating, cooling and ventilation systems before main engine start. That allows the cabin to be comfortable while passengers board without the expense, noise and danger of running one of the main engines of the aircraft. The power supply is also used for power control systems upstream. Groups auxiliary power units are also connected to a hydraulic pump, allowing flight crews to maintain and operate the flight controls and equipment power, without running the main engines. This same function is also used as a backup in case of flight engine failure or malfunction of the hydraulic pump.
History
An engine-piston gasoline APU was first used on the Pemberton-Billing PB31 Nighthawk aircraft Scout 1916. The Boeing 727 in 1963 was the first aircraft gas turbine equipped with an APU, allowing it to operate at small regional airports, independent facilities ground. Although APUs have been installed in many locations on various military and commercial aircraft, they are usually mounted on the rear modern jet aircraft. The APU exhaust can be seen on more modern aircraft like a small pipe exiting at the tail of the aircraft.
Recent designs have started to explore the use of the Wankel engine in this role. The Wankel offers power-weight ratios that are above conventional piston engines and better fuel economy than a turbine engine.
APU mounted ETOPS (Extended-range Twin-engine Operations) aircraft are a critical safety device, as they supply power backup and compressed air instead of engine death no generator or main engine. While some APUs may not be started while the aircraft is in flight, ETOPS GEA-compliant must be started flying at altitudes up to the service ceiling of aircraft. Recent applications have specified start to 43,000 feet (13,000 m) from a complete cold-soak condition. If the APU or its electrical generator is not available, the aircraft can not be released for ETOPS flight and is forced to take a longer route non-ETOPS.
In the event of a failure of the APU air unit startup (ASU) and a ground power unit (GPU) are needed for starting the main engines on the ground and to provide an aircraft electrical power before starting the main engine.
Sections of the APU
APU A typical gas turbine transport aircraft business has three main sections:
power section
compressor load and
Gearbox Section
The power section is the part of engine gas generator and produces all the power of the tree of the APU. The load compressor is generally a compressor mounted on the shaft which provides tires for airplanes, even if some APU bleed air extracted from the power section of the compressor. There Both devices operated: the inlet guide vanes that regulate air compressor and the load control valve that runaway maintains stable operation or surge of free turbine engine. The third section of the engine is the gearbox. The transfer of power to the box tree main engine generator cooled oil for electricity. In the gearbox, the power is also transferred to engine accessories such as fuel control, the module lubrication and cooling. In addition, it is also a starter connected by train gear to perform the function from the UPA. Some use a combination APU starter / generator of the APU start and power generation to reduce complexity.
Some APUs use a electronic control box (ECB) which aims to control the auxiliary power. He also serves as an interface between the subsystems of an APU and aircraft.
With 787 is the all electric aircraft, the APU provides power for the aircraft. The absence of a pneumatic system simplifies design, but the demand to hundreds of kilowatts (kW) of electricity requires heavier generators and unique requirements of the system.
Onboard solid oxide fuel cell (SOFC) APU are being investigated.
Manufacturers
Three major companies competing in the market aircraft APU: Goodrich Corporation, a United Technologies Corporation (through its subsidiary Pratt & Whitney Canada and Hamilton Sundstrand), and Honeywell International Inc.
Military aircraft
The small military aircraft such as fighters and attack aircraft, auxiliary function systems food that are different from those used in transport aircraft. The functions of engine start and provide power and water are divided between two units, the fuel of the starting and emergency power unit.
Jet fuel starter
A fuel mode, or JFS, is a small turbine designed to power the coil of the main engine RPM to its self-accelerating. Unlike auxiliary power devices used in transport aircraft, the JFS provides power through an output shaft connected to a box main engine, rather than bleed air.
Unlike the APUs in transport aircraft, which are open by electric power, a JFS is blown to start an engine with a hydraulic fluid from a hydraulic accumulator (A type of reservoir fluid pressure). The advantages of this system on an electrically started APU are increased reliability and independence ground support. The batteries can go dead if the device is not used for a long period of time, while a hydraulic accumulator will charge indefinitely. From an airplane with a request JFS no external equipment or personnel on the ground, and requires only a small amount of energy battery to operate the controls JFS and electric valves in the hydraulic system. Once the main engine starting, the battery is recharged JFS almost instantly by the pump driven by hydraulic motor, while a battery would take a lot longer to load. Where the main engine does not start and the hydraulic accumulator is discharged, the battery can be recharged by a hand pump on board the aircraft.
All inputs of fuel use a section of free power turbine, but the method of connecting to the engine depends on the design of aircraft. In single-engine airplane such as the A-7 Corsair II and F-16 Fighting Falcon, the power section JFS is still connected to the main engine of the engine accessory gearbox. In contrast, the twin-engine F-15 Eagle has a single JFS, and JFS the power section is connected to a central box that can be hired for a motor at a time.
emergency power unit
Emergency water and electrical power is provided by another type of gas turbine engine. Unlike for most gas turbines, a unit of emergency power has no compression of gas lighters, and uses a combination of hydrazine and water, rather than kerosene. When the mixture of water and hydrazine is released and passes through a catalyst iridium, it ignites, creating hot gas in the turbine expansion. The power created is transmitted through a box speed to drive an electrical generator and hydraulic pump.
Hydrazine is contained in a sealed battery, nitrogen charged. When the system is armed, the hydrazine is released when the engine generators go off-line, or if all the hydraulic pump motor fail.
Spacecraft
APUs are even more critical for flight operations of the Space Shuttle. Unlike the auxiliary power planes, they provide the hydraulic pressure, not electricity. The space shuttle has three redundant auxiliary power units, powered by fuel hydrazine. They work at the chair lift, and on return and landing. During the rise in tension, provide GEA Energy gimballing hydraulic motors shuttle and control surfaces. During the landing, they power the control surfaces and brakes. Landing can be accomplished with a single APU. The STS-9, two of APUs Columbia caught fire, but the flight still landed successfully.
Armor
APU also mounted on tanks to provide power to shutdown without high fuel consumption and high infrared signature caused by turning the main engine. Both the M1 Abrams and the Leopard 2 variants, such as Spanish and Danish versions carry the APU in the rear section of the hull law. The British Centurion tank uses an Austin A-Series inline-4 that its auxiliary power.
Utility Vehicles
APU diesel truck
The APU The most common for a commercial vehicle is a small diesel engine with its own cooling system, heating system, generator alternator system or with or without UPS, and the air conditioning compressor, installed in a housing and mounted on the chassis frame of a tractor-trailer. Other models to fully integrate the auxiliary cooling, heating, and electrical components in the chassis of the truck. These units are used for climate control and electric power for sleeper cab of the truck and engine block heater during downtime on the road.
A car or a refrigerated trailer or semi-frozen food package can be equipped with an APU independent fuel tank to maintain a temperature low during transport, without requiring a source of transportation energy supplied from outside.
In the U.S., Federal Ministry of transport regulations require 10 hours of rest for 11 hours of driving. During these periods, drivers often idle their engines to provide heat, light and power of various items of comfort. Although diesel engines are very efficient when idling, it is still financially and environmentally costly to idle like this, from a fuel standpoint and engine wear. The APU is designed to eliminate these idle long. Since the generator engine is a fraction of movement of the main engine, it uses a fraction of the fuel, some models can operate for eight hours on a gallon (4 liters) of diesel. The generator also supplies the main engine block heater and fuel system, so that the main engine can be started easily just before departure if the APU is allowed to run for a period in advance. An APU can save up to 20 gallons (Cat 600-10 hours downtime @ 2 gallons per hour while idling) (76 liters) of fuel per day, and can extend the useful life of the main engine for about 100,000 miles (160,000 kilometers), reducing non-productive time of the execution. [Citation needed]
Some APUs can also use the vehicle to the ground connection for external power their heating and cooling functions, eliminating and fuel consumption during rest periods altogether. Many truck stops provide electrical connections to the ground in their parking lots.
Some APUs can also use PV solar and wind power as an option for electricity generation is stored in batteries for later use. Unlike other APU APU renewables use the sun and wind power instead of a fuel to generate power to run air conditioning and heating and other accessories for semi trucks. APUs hybrids are able to replace APU fuel.
On some older diesel engines, an APU was used instead of an electric motor to start the main engine. They were mainly used on large pieces of construction equipment.
As an alternative to diesel units, auxiliary power using a system of auxiliary battery or hydrogen fuel cells as an energy source have also been designed. Freightliner showed a demonstration model of a fuel cell APU, running on a liquid hydrogen tank mounted on the truck, on one of their Class century S / T tractors.
Other forms of transport
Where the removal of exhaust gas or noise is particularly important (as yachts, motor homes), fuel cells and photovoltaic modules are used as auxiliary power for electricity generation.
APU currently the most common units for trucks on the road are, Wabaso, Proheat and spar.
Ski APU also use a mechanical, if the main disk (usually electric) should fail or lose power, allowing the elevator to continue functioning. They can be either gas, diesel or propane, and are connected to the main shaft or transmission by chains or belts.
See also
Wikimedia Commons has media related to: auxiliary power units (aircraft)
Start system air
Coffman starter – a similar system that uses an explosive cartridge to supply the gas pressure.
References
Pats ^ APU
^ High power density diesel rotary engine .. and auxiliary power.
^ 2004 – Fuel cell SOFC APU
^ TRU Fuel Cells
References
"Armored auxiliary power" for the design of a modern gas turbine APU
'Space Shuttle Orbiter APU "
Sound of an APU inside a Boeing 737 cabin "
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