- Transport aircraft History Sections Power section Load compressor section Gearbox section Manufacturers
- Spacecraft
- Armor
- Commercial vehicles Fuel cells
- See also
- Notes
- References
- External links
{{Distinguish|AMD Accelerated Processing Unit}}{{See also|Uninterruptible power supply}}An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115 V alternating current (AC) at 400 Hz (rather than 50/60 Hz in mains supply), to run the electrical systems of the aircraft; others can produce 28 V direct current (DC).[1] APUs can provide power through single- or three-phase systems. Transport aircraftHistoryDuring World War I, the British Coastal class blimps, one of several types of airship operated by the Royal Navy, carried a {{convert|1.75|hp|kW}} ABC auxiliary engine. These powered a generator for the craft's radio transmitter and, in an emergency, could power an auxiliary air blower.{{refn|group=Note|A continuous supply of pressurized air was needed to keep the airship's Ballonets inflated, and so maintain the structure of the gasbag. In normal flight, this was collected from the propeller slipstream by air scoop}}[2] One of the first military fixed-wing aircraft to use an APU was the British, World War 1, Supermarine Nighthawk, an anti-Zeppelin Night fighter.[3] During World War II, a number of large American military aircraft were fitted with APUs. These were typically known as putt–putts, even in official training documents. The putt-putt on the B-29 Superfortress bomber was fitted in the unpressurised section at the rear of the aircraft. Various models of four-stroke, Flat-twin or V-twin engines were used. The {{convert|7|hp|kW}} engine drove a P2, DC generator, rated 28.5 Volts and 200 Amps (several of the same P2 generators, driven by the main engines, were the B-29's DC power source in flight). The putt-putt provided power for starting the main engines and was used after take-off to a height of {{convert|10000|ft}}. The putt-putt was restarted when the B-29 was descending to land.[4] Some models of the B-24 Liberator had a putt–putt fitted at the front of the aircraft, inside the nose-wheel compartment.[5] Some models of the Douglas C-47 Skytrain transport aircraft carried a putt-putt under the cockpit floor.[6] The first German jet engines built during the Second World War used a mechanical APU starting system designed by the German engineer Norbert Riedel. It consisted of a {{convert|10|hp|kW}} two-stroke flat engine, which for the Junkers Jumo 004 design was hidden in the intake diverter, essentially functioning as a pioneering example of an auxiliary power unit for starting a jet engine. A hole in the extreme nose of the diverter contained a manual pull-handle which started the piston engine, which in turn rotated the compressor. Two spark plug access ports existed in the Jumo 004's intake diverter to service the Riedel unit's cylinders in situ, for maintenance purposes. Two small "premix" tanks for the Riedel's petrol/oil fuel were fitted in the annular intake. The engine was considered an extreme short stroke (bore / stroke: 70 mm / 35 mm = 2:1) design so it could fit within the intake diverter of jet engines like the Jumo 004. For reduction it had an integrated planetary gear. It was produced by Victoria in Nuremberg and served as a mechanical APU-style starter for all three German jet engine designs to have made it to at least the prototype stage before May 1945: the Junkers Jumo 004, the BMW 003 (which uniquely appears to use an electric starter for the Riedel APU),[7] and the prototypes (19 built) of the more advanced Heinkel HeS 011 engine, which mounted it just above the intake passage in the sheetmetal of the engine nacelle nose.[8] The Boeing 727 in 1963 was the first jetliner to feature a gas turbine APU, allowing it to operate at smaller airports, independent from ground facilities. The APU can be identified on many modern airliners by an exhaust pipe at the aircraft's tail.[9] SectionsA typical gas turbine APU for commercial transport aircraft comprises three main sections: Power sectionThe power section is the gas generator portion of the engine and produces all the shaft power for the APU.[10] Load compressor sectionThe load compressor is generally a shaft-mounted compressor that provides pneumatic power for the aircraft, though some APUs extract bleed air from the power section compressor. There are two actuated devices: the inlet guide vanes that regulate airflow to the load compressor and the surge control valve that maintains stable or surge-free operation of the turbo machine.[11] Gearbox sectionThe gearbox transfers power from the main shaft of the engine to an oil-cooled generator for electrical power. Within the gearbox, power is also transferred to engine accessories such as the fuel control unit, the lubrication module, and cooling fan. In addition, there is also a starter motor connected through the gear train to perform the starting function of the APU. Some APU designs use a combination starter/generator for APU starting and electrical power generation to reduce complexity. On the Boeing 787 more-electric aircraft, the APU delivers only electricity to the aircraft. The absence of a pneumatic system simplifies the design, but high demand for electricity requires heavier generators.[12][13] Onboard solid oxide fuel cell (SOFC) APUs are being researched.[14] ManufacturersOn June 4, 2018, Boeing and Safran announced their 50-50 partnership to design, build and service APUs after regulatory and antitrust clearance in the second-half of 2018.[15] Boeing produced several hundred T50/T60 small turboshafts and their derivatives in the early 1960s.Safran produces helicopters and business jets APUs but stopped the large APUs since Labinal exited the APIC joint venture with Sundstrand in 1996.[This could threaten the dominance of Honeywell and United Technologies.][{{cite news |url= https://www.flightglobal.com/news/articles/boeing-and-safran-partner-to-disrupt-apu-market-449184/ |title= Boeing and Safran partner to disrupt APU market |date= June 4, 2018 |author= Stephen Trimble |work= Flightglobal}}]
17. ^-->P&WC claims the remaining 35% with the A380, B787 and B747-8.[{{cite news |url= https://www.flightglobal.com/news/articles/analysis-how-will-boeing-safran-venture-shake-up-ap-449234/ |title= How will Boeing-Safran venture shake up APUs? |date= June 5, 2018 |author= Stephen Trimble |work= Flightglobal}}]
18. ^-->The 2017 market for production was worth $800 million: $700m civil and $100m military, while the MRO market was worth $2,400 million, spread equally between civil and military.[{{cite news |url= http://aviationweek.com/commercial-aviation/opinion-why-boeing-diving-apu-production |title= Opinion: Why Is Boeing Diving Into APU Production? |date= Jun 27, 2018 |author= Kevin Michaels |work= Aviation Week & Space Technology}}]
19. ^{{cite web | url = http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/hyd | title = Hydraulic System | website = spaceflight.nasa.gov | publisher = NASA | access-date = 8 February 2016}}
20. ^{{cite web | url = http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-2.html | title = Space Shuttle Mission Archives STS-2 | website = www.nasa.gov | publisher = NASA | access-date = 18 February 2016}}
21. ^{{cite web | url = http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-3.html | title = Space Shuttle Mission Archives STS-3 | website = www.nasa.gov | publisher = NASA | access-date = 18 February 2016}}
22. ^{{cite interview | title = Jack R. Lousma Edited Oral History Transcript | url=http://www.jsc.nasa.gov/history/oral_histories/LousmaJR/LousmaJR_3-15-10.htm | date=15 March 2010 | accessdate=18 February 2016 | last=Lousma | first=Jack R. | subjectlink=Jack R. Lousma | interviewer=Ross-Nazzal, Jennifer | work=NASA Johnson Space Center Oral History Project}}
23. ^{{cite web | url = http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-9.html | title = Space Shuttle Mission Archives STS-9 | website = www.nasa.gov | publisher = NASA | access-date = 18 February 2016}}
24. ^{{cite web |url=https://iremember.ru/en/memoirs/tankers/dmitriy-loza/ |title=IRemember.ru WW II Memoirs |last=Loza |first=Dimitri |date=September 21, 2010 |website=iremember.ru/en |publisher=IRemember |access-date=June 13, 2017 |quote=Still one great plus of the Sherman was in the charging of its batteries. On our T-34 it was necessary to run the engine, all 500 horsepower of it, in order to charge batteries. In the crew compartment of the Sherman was an auxiliary gasoline engine, small like a motorcycle's one. Start it up and it charged the batteries. This was a big deal to us!}}
25. ^{{Cite web|url=http://www.ooida.com/EducationTools/Info/weight-exemptions.asp|title=Vehicle weight exemptions for APUs|last=|first=|date=|website=|access-date=}}
26. ^{{cite book|last1=Orlemann|first1=Eric|title=Caterpillar Chronicle : History of the Greatest Earthmovers|isbn=9781610605779|pages=35}}
27. ^{{cite web|title=Willard v. Caterpillar, Inc. (1995)|url=http://law.justia.com/cases/california/court-of-appeal/4th/40/892.html|website=Justia Law|accessdate=13 December 2016}}
28. ^{{cite news|first=Christie-Joy |last=Broderick |author2=Timothy Lipman |author3=Mohammad Farshchi |author4=Nicholas Lutsey |author5=Harry Dwyer |author6=Daniel Sperling |author7=William Gouse |author8=Bruce Harris |author9=Foy King |title=Evaluation of Fuel Cell auxiliary Power Units for Heavy-Duty Diesel Trucks |year=2002 |publisher=Elsevier Sciences Ltd. |url=http://www.uctc.net/papers/587.pdf |work=Transportation Research Part D |pages=303–315 |accessdate=2011-09-27 |deadurl=yes |archiveurl=https://web.archive.org/web/20120403131809/http://www.uctc.net/papers/587.pdf |archivedate=2012-04-03 }}
29. ^1 {{cite journal | title = Delphi truck fuel-cell APU to hit road in 2012 | journal = Vehicle Electrification | date = 2010-05-12 | first = Paul | last = Weissler| id = | url = http://ev.sae.org/article/8222 | accessdate = 2011-09-27 | quote = and Delphi says it will have a 5-kW APU on the market in 2012. }}
30. ^{{cite news | first = Mike | last = Jacobs | title = Solid Oxide Fuel Cell Successfully Powers Truck Cab and Sleeper in DOE-Sponsored Test | date = 2009-03-19 | publisher = National Energy Technology Laboratory | url = http://www.netl.doe.gov/publications/press/2009/09017-Fuel_Cell_Powers_Commercial_Trucks.html | work = NETL: News Release | accessdate = 2011-09-27}}
References{{reflist}}External links{{commons category|Auxiliary power units}}- "Space Shuttle Orbiter APU"
- "Sound of an APU from inside a Boeing 737 cabin"
- The Riedel Starter Motor In: Messerschmitt Me 262B in Detail; The airframe, engines and canopy
{{Aircraft components}}{{Aircraft piston engine components}}{{Aircraft gas turbine engine components}} 4 : Starting systems|Electrical generators|Aircraft components|Aircraft auxiliary power units |