General Electric CJ805

Last updated
CJ805
General Electric CJ805-21 at Flugausstellung Hermeskeil, pic1 (cropped).jpg
A CJ805-21 turbojet on display at Flugausstellung Hermeskeil
Type Turbojet (CJ805)
Turbofan (CJ805-23)
National origin United States
Manufacturer General Electric Aircraft Engines
Major applicationsCJ805: Convair 880
CJ805-23: Convair 990 Coronado
Developed from General Electric J79

The General Electric CJ805 is a jet engine which was developed by General Electric Aircraft Engines in the late 1950s. It was a civilian version of the J79 and differed only in detail. [1] It was developed in two versions. The basic CJ805-3 was a turbojet and powered the Convair 880 airliner, and the CJ805-23 (military designation TF35) a turbofan derivative which powered the Convair 990 Coronado variant of the 880.

Contents

Design and development

Impetus

Turbojet engines consist of a compressor at the front, a burner area, and then a turbine that powers the compressor. In order to reach worthwhile compression ratios, compressors consist of multiple "stages", each further compressing the air leaving the previous one.

One common problem with early jet engines was the phenomenon of "surging" or compressor stall. Stalls could occur when the approaching airflow was not in-line with the aircraft inlet to the compressor or when the throttle was advanced too quickly.

When engines had to be designed with pressure ratios greater than about 5, [2] to meet demands for reduced fuel consumption, a new stalling phenomenon came to light, rotating stall. It occurred at low compressor speeds and caused blades in the first stage to break. This troublesome speed area is known as "off-design" and required the invention of special devices to make the compressor work. The compressor worked well near its maximum speed, known as "design", with a fixed area convergence from entry to exit to go with the design values of compression/density and with fixed blade angles set to give low pressure losses. At low speeds the much lower compression didn't squeeze the air enough to get through the now too-small exit. The velocity triangle combined the now too-slow entry air with the blade speed and gave a stalling angle. [3]

One common solution used on early engines, and widely used today, [4] was to give the air extra escape holes to speed up the entry air, i.e. the use of "bleed air" which is allowed to escape from openings near the middle of the compressor stages and vented overboard. The bleed valves close as the engine RPM increases towards operational speeds.

Another solution was the use of variable inlet vanes. The angle of incidence of the vanes at the front of the engine is changed to partially block the inlet area, which reduces the compression, and also angle the air onto the compressor blades to prevent stalling. This has the advantage of being more efficient than allowing valuable compressed air to escape, although fuel consumption at low speeds is relatively unimportant.

Further increases in pressure ratio, demanded by government procurement agencies and commercial airlines for long-range aircraft, caused a bigger mismatch of flow areas/density changes and blade angles. Two approaches were followed: slowing the blade speeds at the front of the compressor by splitting it into two separately rotating parts (spools) or making stators variable on the first few stages as well as the inlet vanes. A disadvantage is significant mechanical complexity as each stator blade has to be independently rotated to the desired angles. Two spools need more bearings and turned out to be heavier.

Bleed valves, two or three spools and variable stators are all used together on modern engines to cope with rotating stall during starts and at low speeds and to allow surge-free fast accelerations.

Rolls-Royce considered the variable stator idea in the 1940s, but abandoned it [5] until using it in the 1980s on the V2500 engine. [6] They began development of two-spool designs, a concept that was also selected by Pratt & Whitney. The variable stator path was only selected by GE after a year-long design study competition comparing two spools and several stages of variable stators with objectives of efficient performance at cruise Mach 0.9 and at Mach 2, increased thrust, reduced fuel consumption and weight. [7] The J79 emerged as a powerful, lightweight design 2,000 lb lighter than its 2-shaft competitor for the B-58, the J57 engine, [8] and GE began considering it as the basis for a high-power engine for commercial use. [9]

CJ805 program

A Douglas RB-66A test aircraft powered by two GE CJ805-3 engines, on the ramp at Edwards AFB RB-66A (52-2828) with CJ805 test engines.JPG
A Douglas RB-66A test aircraft powered by two GE CJ805-3 engines, on the ramp at Edwards AFB

In 1952, Chapman Walker's design team at GE built a one-off prototype of a jet engine designed specifically for transatlantic airliners. It used a single-stage fan powered by the same turbine shaft as the main engine compressor, as opposed to the Pratt & Whitney designs that were using a separate power shaft to run the fan. The GE design proved to be difficult to start and operate and was not developed further. [5]

In 1955 Jack Parker took over GE's Aircraft Gas Turbine division. He hired Dixon Speas to begin interviewing executives at airlines to try to get a sense of the future market. Parker asked Speas to interview not the CEOs, but executives that might be the CEO by the time GE was ready to enter the civilian jet engine market. Parker, Speas and Neil Burgess, who ran the J79 program, spent a month meeting with American Airlines, Delta, United, KLM, Swissair and SAS. The meetings demonstrated that those airlines that were flying propeller aircraft across the Atlantic were all looking to replace them with jets. [10]

CJ805-3

Around the same time, Convair was canvassing US carriers and found demand for a smaller jet aircraft for medium-range domestic routes. They began development of what would become the 880, and approached Burgess to see if GE could develop a version of the J79 for this role. Burgess responded by quickly sketching a version of the J79 with the afterburner removed and replaced by a thrust reverser, giving them an estimated unit price of $125,000 per engine. [5]

The 880's primary sales feature over the competing Douglas DC-8 and Boeing 707 was a higher cruise speed. This demanded more engine power from a lighter design, which naturally led to a design like the J79. To gain experience with the engine in a civil setting, GE equipped a Douglas RB-66 with the new engine and flew simulated civil aviation routes out of Edwards Air Force Base. [11]

As development progressed, the 707 began to enter service, and noise complaints became a serious issue. There was already a lawsuit, by residents around Newark airport, concerning the noise from existing propeller-driven aircraft such as the Lockheed Super Constellation, Boeing Stratocruiser and Douglas DC-7C. [12] One way to reduce this problem is to mix cold air into the jet exhaust, which was accomplished on early engines with the addition of scalloped nozzles. [lower-alpha 1] This solution was also adopted for the CJ805.

CJ805-23

Cutaway of a CJ805-23, the turbofan version of the engine, with fan at the rear General Electric CJ-805.jpg
Cutaway of a CJ805-23, the turbofan version of the engine, with fan at the rear
The turbofan CJ805-23 powered the Convair 990 airliners General Electric CJ-805-23 mounted to Convair 990.jpg
The turbofan CJ805-23 powered the Convair 990 airliners

Several airlines asked Convair for a larger version of the 880 with potential transatlantic range. Such a design would be larger to hold more seating, as well as having to carry more fuel. To power it, a more powerful engine would be needed. By this time, the Rolls-Royce Conway was entering service, and the Pratt & Whitney JT3D was following close behind. These designs both had twin-spool compressors, as opposed to using variable stators, and the lower speed of the front, low-pressure, spool made it easy to power a fan. [14]

The problems RR and P&W had addressed with the two-spool system had been solved on the J79 with the variable stators, so in relative terms, the single compressor rotational speed was much faster than the low-pressure stage of these other engines. This meant it was not suitable for direct connection to a fan stage. Instead, GE solved this problem with the addition of a completely separate fan system at the rear of the engine, powered by a new turbine stage. The system was essentially a bolt-on extension to the existing design and had almost no effect on the operation of the original engine. [15]

Each turbine blade was an integral part of a "blucket", the outboard section of which was a fan rotor blade. [16] Running freely on a stub shaft, a series of buckets, mounted on a disc, made up the aft rotor assembly. The efflux from the turbojet expanded through the (inner) turbine annulus, thus providing power directly to the fan blades located in the outer annulus. A full-length cowl, an annular exhaust system and a bucket thrust-reverser were fitted for the Convair 990. [17]

The unique feature of the CJ805-23 was the transonic single stage fan. [18] NACA had done significant research on multistage transonic compressors during the 1950s. Using this data, GE decided to design and test a high-pressure ratio single stage transonic fan. Much to their amazement the unit more than met the design target, including that of high efficiency. A modified version of this research unit was subsequently incorporated into the CJ805-23 aft fan. With no experience of transonic fan design and little time available, Pratt & Whitney had to resort to using 2 fan stages to produce a similar pressure ratio for their JT-3D turbofan. Although not an overhung design, the CJ805-23 transonic fan did not require any inlet guide vanes. There was, however, a series of structural vanes to help support the fan casing. [19]

Production ends

With additional changes, fuselage stretches, and the addition of anti-shock bodies, the new airliner emerged as the Convair 990. However, by this time the project had suffered several delays, allowing new versions of the DC-8 and 707 to lock up major sales. In the end, Convair sold only 102 880s and 990s in total, losing $600 million on the program. [20]

There was only one other customer for the 805-23. In 1961, Sud Aviation approached GE to pitch them on the idea of adapting the Rolls-Royce Avon powered Caravelle to the 805-23, producing a flying technology showcase for both companies. [21] For this role they introduced a new version with a relatively short fan cowl and thrust reverser, compared to the full-length cowling on the 990. [22] Rolls-Royce quickly built and tested an aft-fan demonstrator Avon to compete with the greater thrust and lower specific fuel consumption of the CJ805-23. In the end, the Caravelle was instead re-engined with the P&W JT8D turbofan. [23]

The CJ805 program was not a commercial success, and GE lost approximately $80 million on the program with only a few hundred engines produced in total. [21] In service, the design proved fragile, but these problems led to the programs ultimate success for the company. [24]

During the time they were talking to airline CEOs, in 1956 the company hired the former head of American Airlines' maintenance department, John Montgomery, to run the production lines. Montgomery gathered comments from the industry on the state of the engine market, and found that many were complaining about the unreliability of the large piston engines then being used, notably the Wright R-3350. Wright management refused to put more money into the program to improve the engine, leading to a serious backlash from the customers. [25]

Montgomery hired Walter Van Duyan away from Wright to set up GE's service department, and they provided excellent service in spite of the engine's problems. GE quickly gained a reputation for standing behind their products that endures to this day. [25]

The work on the 805 also had several spin-off products. Among them was another aft-fan design, the General Electric CF700 used in the Dassault Falcon 20 business jet, which was developed from the General Electric J85 in the same way as the J79 was adapted to the 805. [26] Their fan technology was also used in the XV-5 Vertifan. [27]

Variants and applications

Rear view of a CJ805-3 turbojet equipped with a scalloped nozzle hush kit Convair 880 Lisa Marie Graceland Memphis TN 2013-04-01 028.jpg
Rear view of a CJ805-3 turbojet equipped with a scalloped nozzle hush kit
CJ805-1
CJ805-2
CJ805-3
Convair 880 [28]
CJ805-3A
Convair 880-22 : Revised variable inlet guide vane and stator control. [28]
CJ805-3B
Convair 880-22M : Increased thrust. [28]
CJ805-11
CJ805-13
CJ805-21
[29]
CJ805-23
Flight testing in a Douglas RB-66: Aft-fan variant with a direct drive fan attached to a free-running LP turbine. [28]
CJ805-23A
[28]
CJ805-23B
Convair 990 Coronado [28]
CJ805-23C
Intended for the proposed Sud Aviation Caravelle 10A. Only a single airframe, intended as a prototype for the US market, was equipped with the CJ805. [28]
TF35
Military version of the CJ805-23 turbofan.

Specifications (CJ805-3B)

Data from FAA Type Certificate Data Sheet, E-306

General characteristics

Components

Performance

Specifications (CJ805-23B)

Data from

General characteristics

  • Type: Aft-fan unmixed turbofan
  • Length: 139 in (3,531 mm)
  • Diameter: 53 in (1,346 mm)
  • Dry weight: 3,730 lb (1,692 kg)

Components

Performance

See also

Related development

Related lists

Notes

  1. Which has re-appeared in modern form on the Boeing 787. [13]

Related Research Articles

<span class="mw-page-title-main">Turbofan</span> Airbreathing jet engine designed to provide thrust by driving a fan

A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a combination of the preceding generation engine technology of the turbojet, and a reference to the additional fan stage added. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust.

<span class="mw-page-title-main">Turbojet</span> Airbreathing jet engine which is typically used in aircraft

The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and a turbine. The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.

<span class="mw-page-title-main">General Electric TF39</span> Turbofan aircraft engine

The General Electric TF39 is a high-bypass turbofan engine that was developed to power the Lockheed C-5 Galaxy. The TF39 was the first high-power, high-bypass jet engine developed. The TF39 was further developed into the CF6 series of engines, and formed the basis of the LM2500 and LM6000 marine and industrial gas turbine. On September 7, 2017, the last active C-5A powered with TF39 engines made its final flight to Davis-Monthan Air Force Base for retirement. The TF39 was effectively retired, and all remaining active C-5 Galaxys are now powered by F138 engines.

<span class="mw-page-title-main">Pratt & Whitney J57</span> Turbojet engine

The Pratt & Whitney J57 is an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 was the first 10,000 lbf (45 kN) thrust class engine in the United States. It was also the first two-spool turbojet to run, a few months before the similar Bristol Olympus in the UK.

<span class="mw-page-title-main">Lyulka AL-21</span>

The Lyulka AL-21 is an axial flow turbojet engine created by the Soviet Design Bureau named for its chief designer Arkhip Lyulka.

<span class="mw-page-title-main">General Electric J79</span> Axial flow turbojet engine

The General Electric J79 is an axial-flow turbojet engine built for use in a variety of fighter and bomber aircraft and a supersonic cruise missile. The J79 was produced by General Electric Aircraft Engines in the United States, and under license by several other companies worldwide. Among its major uses was the Lockheed F-104 Starfighter, Convair B-58 Hustler, McDonnell Douglas F-4 Phantom II, North American A-5 Vigilante and IAI Kfir.

A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, or gas generator, from a jet engine.

A compressor map is a chart which shows the performance of a turbomachinery compressor. This type of compressor is used in gas turbine engines, for supercharging reciprocating engines and for industrial processes, where it is known as a dynamic compressor. A map is created from compressor rig test results or predicted by a special computer program. Alternatively the map of a similar compressor can be suitably scaled. This article is an overview of compressor maps and their different applications and also has detailed explanations of maps for a fan and intermediate and high-pressure compressors from a three-shaft aero-engine as specific examples.

A jet engine performs by converting fuel into thrust. How well it performs is an indication of what proportion of its fuel goes to waste. It transfers heat from burning fuel to air passing through the engine. In doing so it produces thrust work when propelling a vehicle but a lot of the fuel is wasted and only appears as heat. Propulsion engineers aim to minimize the degradation of fuel energy into unusable thermal energy. Increased emphasis on performance improvements for commercial airliners came in the 1970s from the rising cost of fuel.

<span class="mw-page-title-main">Rolls-Royce RB401</span> 1970s British turbofan aircraft engine

The Rolls-Royce RB.401 was a British two-spool business jet engine which Rolls-Royce started to develop in the mid-1970s as a replacement for the Viper. RB.401-06 prototype engines were already being manufactured when a decision to develop the higher thrust RB.401-07 was taken.

<span class="mw-page-title-main">General Electric YF120</span> American fighter variable-cycle turbofan engine

The General Electric YF120, internally designated as GE37, was a variable cycle afterburning turbofan engine designed by General Electric Aircraft Engines in the late 1980s and early 1990s for the United States Air Force's Advanced Tactical Fighter (ATF) program. It was designed to produce maximum thrust in the 35,000 lbf (156 kN) class. Prototype engines were installed in the two competing technology demonstrator aircraft, the Lockheed YF-22 and Northrop YF-23.

<span class="mw-page-title-main">Variable cycle engine</span> Aircraft propulsion system efficient at a range of speeds higher and lower than sounds

A variable cycle engine (VCE), also referred to as adaptive cycle engine (ACE), is an aircraft jet engine that is designed to operate efficiently under mixed flight conditions, such as subsonic, transonic and supersonic.

<span class="mw-page-title-main">General Electric YJ93</span> Turbojet engine

The General Electric YJ93 turbojet engine was designed as the powerplant for both the North American XB-70 Valkyrie bomber and the North American XF-108 Rapier interceptor. The YJ93 was a single-shaft axial-flow turbojet with a variable-stator compressor and a fully variable convergent/divergent exhaust nozzle. The maximum sea-level thrust was 28,800 lbf (128 kN).

<span class="mw-page-title-main">Components of jet engines</span> Brief description of components needed for jet engines

This article briefly describes the components and systems found in jet engines.

<span class="mw-page-title-main">General Electric CF700</span> Turbofan aircraft engine

The General Electric CF700 is an aft-fan turbofan development of the CJ610 turbojet. The fan blades are an extension of the low-pressure turbine blades.

<span class="mw-page-title-main">General Electric J73</span> 1950s American turbojet engine

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 combustor case, and 50% greater airflow was redesignated J73. Its only operational use was in the North American F-86H.

An airbreathing jet engine is a jet engine in which the exhaust gas which supplies jet propulsion is atmospheric air, which is taken in, compressed, heated, and expanded back to atmospheric pressure through a propelling nozzle. Compression may be provided by a gas turbine, as in the original turbojet and newer turbofan, or arise solely from the ram pressure of the vehicle's velocity, as with the ramjet and pulsejet.

The Daimler-Benz DB 007 was an early German jet engine design stemming from design work carried out by Karl Leist from 1939. This was a complex design featuring contra-rotating stages and a bypass fan, making it one of the earliest turbofan designs to be produced. The end result of the design work was built as the DB 007 and began testing on a test-bed on 27 May 1943. Due to the expected low performance, complexity and the good results achieved by much simpler designs, work was halted on the DB 007 in May 1944 by order of the RLM.

<span class="mw-page-title-main">General Electric Affinity</span> Supersonic aircraft engine design

The General Electric Affinity was a turbofan developed by GE Aviation for supersonic transports. Conceived in May 2017 to power the Aerion AS2 supersonic business jet, initial design was completed in 2018 and detailed design in 2020 for the first prototype production. GE Aviation discontinued development of the engine in May 2021. Its high-pressure core is derived from the CFM56, matched to a new twin fan low-pressure section for a reduced bypass ratio better suited to supersonic flight.

<span class="mw-page-title-main">Boom Symphony</span> Supersonic turbofan engine design

The Boom Symphony is a medium-bypass turbofan engine under development by Boom Technology for use on its Overture supersonic airliner. The engine is designed to produce 35,000 pounds of thrust at takeoff, sustain Overture supercruise at Mach 1.7, and burn sustainable aviation fuel exclusively.

References

Citations

  1. "Aero Engines 1960". Flight International. 18 March 1960. pp. 381–382.
  2. "Effect of Inlet-Guide-Vane Angle on Blade Vibration and Rotating Stall of 13-Stage Axial-Flow Compressor in Turbojet Engine". 22 May 1956.
  3. Compressor Stall Problems In Gs-Turbine-Type Aircraft Engines, Benser and Finger, Paper presented at the SAE National Aeronautic meeting, New York, April 12, 1956, Volume 65, 1957 p. 188, 190/191
  4. Jet Propulsion, Nicholas Cumpsty1997, Cambridge University Press, ISBN   0-521-59674-2, p.123
  5. 1 2 3 Garvin 1998, p. 16.
  6. "Archived copy". Archived from the original on 2015-05-07. Retrieved 2019-04-23.{{cite web}}: CS1 maint: archived copy as title (link)
  7. seven decades of progress - A Heritage Of Aircraft Turbine Technology, General Electric 1979, Aero Publisher Inc., ISBN   0-8168-8355-6, p.87
  8. seven decades of progress - A Heritage Of Aircraft Turbine Technology, General Electric 1979, Aero Publisher Inc., ISBN   0-8168-8355-6, p.89
  9. Garvin 1998, p. 12.
  10. Garvin 1998, p. 15.
  11. Garvin 1998, pp. 20–21.
  12. Beranek, Leo (January 2007). "The Noisy Dawn of the Jet Age" (PDF). Sound and Vibration.
  13. "NASA Helps Create a More Silent Night". NASA. 13 December 2010.
  14. Garvin 1998, pp. 16–17.
  15. Garvin 1998, pp. 16–18.
  16. "Fig7". Flight International. 30 October 1959. p. 457.
  17. "Fig8". Flight International. 30 October 1959. p. 457.
  18. Galison, P.; Roland, A. (7 March 2013). "The Turbofan Emerges: GE's CJ805-23 Aft Fan Engine". Atmospheric Flight in the Twentieth Century. ISBN   9789401143790.
  19. "3D sectional view of CJ805-23" . Retrieved 2016-02-18.
  20. Garvin 1998, p. 18.
  21. 1 2 Garvin 1998, pp. 19.
  22. Archer, Robert (8 June 1961). "Caravelle a la General Electric". Flight International. pp. 797–798.
  23. Rolls-Royce Aero Engines" Bill Guuston, Patrick Stephens Ltd. 1989, ISBN   1-85260-037-3, p.142
  24. Garvin 1998, p. 21.
  25. 1 2 Garvin 1998, p. 22.
  26. Garvin 1998, p. 23.
  27. "The Power to Fly" Brian Rowe, Pen & Sword Aviation 2005, ISBN   1 84415 200 6, p.25
  28. 1 2 3 4 5 6 7 Bridgman 1955, pp. 62–63.
  29. Bridgman 1955, p. 60.

Bibliography

  • Bridgman, Leonard (1955). Jane's all the World's Aircraft 1955–56. Jane's all the World's Aircraft Publishing Co. Ltd.
  • Garvin, Robert (1998). Starting Something Big The Commercial Emergence of GE Aircraft Engines. AIAA. ISBN   1-56347-289-9.
  • Gunston, Bill (2006). World Encyclopedia of Aero Engines, 5th Edition. Phoenix Mill, Gloucestershire, England, UK: Sutton Publishing Limited. ISBN   0-7509-4479-X.
  • Neumann, Gerhard (June 1984). Herman the German. William Morrow & Co. p. 269. ISBN   0-688-01682-0. The former enemy alien and Air Corps G.I. whose inventive skills and maverick management techniques made jet engine history