The General Electric J73 turbojet was developed by General Electric from the earlier J47 engine. Its original USAF designation was J47-21, but with innovative features including variable inlet guide vanes, double-shell (inner and outer) combustor case, and 50% greater airflow was redesignated J73. Its only operational use was in the North American F-86H .
19-510: An engine, uprated from the J47, was required for the F-86H. The mass flow was increased by relocating accessories from the centre of the compressor inlet to the underside of the engine. This allowed a reduction in blade hub diameter, which together with an increase in tip diameter, gave a bigger area for air to enter the compressor. The area through the combustion chambers also had to be increased. This
38-463: Is taken for a low-pressure tapping, or from the LP compressor of a two-shaft engine). One important use for bleed air is for cross-starting of other engines in a multi-engine aircraft. Some of the accessories that may be driven include: Additional facilities are provided for a centrifugal oil breather, to separate the drive lubricating oil from the overboard breather air vent. Also access for hand-turning
57-470: Is the clutch "throw out" bearing, sometimes called the clutch release bearing . Fluid-film thrust bearings were invented by Albert Kingsbury , who discovered the principle in the course of bearing and lubrication investigations commencing in 1888 while a student. His first experimental bearing was tested in 1904. He filed for a patent in 1907, and it was granted in 1910. The first Kingsbury bearing in hydroelectric service, one of its major applications,
76-543: The Avco Lycoming company, who were making drive gearboxes for the Westinghouse J40 engine. In some engines, bleed air is also tapped to provide power for accessories, as well as a mechanical shaft drive. Bleed air is particularly useful when a source of compressed air is specifically needed, either to pressurise cabin air , or as a supply of cooling air to other components (to avoid excess heat, this
95-452: The World 1953 Related development Comparable engines Related lists Accessory drive The accessory drive is a gearbox that forms part of a gas turbine engine. Although not part of the engine's core, it drives the accessories – such as generators, pumps for fuel and lubrication oil, air compressors, hydraulic pumps and engine starters – that are otherwise essential for
114-483: The bearing between the pads and a rotating disk, which support the applied thrust and eliminate metal-on-metal contact. Kingsbury and Michell's invention was notably applied to the thrust block in ships. The small size (one-tenth the size of old bearing designs), low friction and long life of Kingsbury and Michell's invention made possible the development of more powerful engines and propellers. They were used extensively in ships built during World War I , and have become
133-404: The engine, during ground maintenance. Thrust bearing A thrust bearing is a particular type of rotary bearing . Like other bearings they permanently rotate between parts, but they are designed to support a predominantly axial load. Thrust bearings come in several varieties. Thrust bearings are commonly used in automotive, marine, and aerospace applications. They are also used in
152-411: The hollow fairing that encloses it. If it is not possible to arrange a single straight path for the driveshaft, it may be arranged in two sections and linked by an intermediate gearbox. This is most commonly required for high-bypass turbofans with large diameter fans. The packaging of an engine within its nacelle is a complicated task. The accessory drive is usually arranged as a curved casing, so that
171-399: The internal gearbox is complicated by the heat and small space available in which to connect the driveshaft. It is usually placed between the compressor outlet and the combustor . In turboprops or designs with centrifugal compressors, it may be placed ahead of the compressor. For two-shaft designs, an accessory drive will be taken from the high-pressure shaft, i.e. the outer and shorter of
190-399: The low-pressure shaft, which may influence the distribution of accessories. To allow for thermal expansion, the drive from the main shaft may be taken by one of three means: To make the best use of the limited space for the driveshaft and internal gearbox, the driveshaft runs at high speed, thus allowing it to be of small diameter. This reduces the disruption to the airflow and the size of
209-429: The main and tail rotor blade grips of RC (radio controlled) helicopters. Thrust bearings are used in cars because the forward gears in modern car gearboxes use helical gears which, while aiding in smoothness and noise reduction, cause axial forces that need to be dealt with. Thrust bearings are also used with radio antenna masts to reduce the load on an antenna rotator . One kind of thrust bearing in an automobile
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#1732773349579228-416: The operation of the engine or the aircraft on which it is mounted. Accessory drives on large engines handle between 400–500 hp. Power for the accessory drive is taken from the central shaft linking the turbine and compressor sections of the engine. This requires an internal gearbox that couples the drive to a radial driveshaft or towershaft that drives an external gearbox . The design of
247-446: The spacing between accessories. Helical gears are sometimes used for the high-torque drives, typically the starter, as these give smoother running. However helical gears also generate an end-thrust, which then requires a more complicated thrust bearing to support them. The complexity of an accessory drive and its gears is so great that they were used as a theme by the anthropomorphic illustrator Boris Artzybasheff in advertising for
266-500: The standard bearing used on turbine shafts in ships and power plants worldwide. (See also Michell/Kingsbury tilting-pad fluid bearings ) Today thrust bearings continue to play an essential role in rotating equipment like expanders, pumps, and gas or steam turbines or compressors. In addition to the traditional babbitt bearings which were used since the early 20th century, new materials for the thrust pads have come into use. For example Bronze and Copper-Chromium are commonly used to improve
285-422: The two concentric shafts. This shaft comes up to speed more quickly when the engine is started. The drive and accessory gearboxes may also be split in two, one driven from each engine shaft, so as to distribute their loads. The engine-critical systems, including the starter drive, are arranged on the high-pressure shaft, with aircraft systems on the low-pressure shaft. The high-pressure shaft also rotates faster than
304-463: The various accessories are mounted close to the engine. The casing is a pair of light alloy castings. Separate machined mounting pads are provided for each accessory. The drive within the casing is provided by a train of spur gears . Accessories are arranged on both sides of the driveshaft entry, in reducing order of their speed. The gears are usually plain spur gears, running in roller bearings . Idler gears are commonly used between them, to increase
323-406: Was done by replacing the multiple individual chambers with a single annular casing with individual flame tubes or cans known as cannular . The pressure ratio was increased and variable inlet guide vanes fitted to prevent low-RPM problems (rotating stall/blade flutter) with the higher design pressure ratio . A 2-stage turbine was required. A low boost (10% at take-off) afterburner was fitted. It
342-493: Was installed at the Holtwood Generating Station in 1912. It remains in full use today. Thrust bearings were independently invented by Australian engineer George Michell (pronounced Mitchell) who patented his invention in 1905. Fluid thrust bearings contain a number of sector-shaped pads, arranged in a circle around the shaft, and which are free to pivot. These create wedge-shaped regions of oil inside
361-588: Was known as a tailpipe augmentation (TPA) system. Four J73 engines were converted to produce thrust using nuclear energy instead of jet fuel. Testing was done in 1957 at the Atomic Energy Commission's National Reactor testing station. The engines were modified to pass the compressor air through a heat exchanger, in which heat was transferred from a nuclear reactor, before entering the compressor turbine at 1,400 degrees F. Data from Flight 9 April 1954 : Aero Engines 1954, Aircraft engines of
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