A J35 with exhaust duct removed, exposing the power turbine.
The General Electric/Allison J35 was the United States Air Force's first axial-flow (straight-through airflow) compressor jet engine. Originally developed by General Electric (GE company designation TG-180) in parallel with the Whittle-based centrifugal-flowJ33, the J35 was a fairly simple turbojet, consisting of an eleven-stage axial-flow compressor and a single-stage turbine. With the afterburner, which most models carried, it produced a thrust of 7,400 lbf (33 kN).
Like the J33, the design of the J35 originated at General Electric, but major production was by the Allison Engine Company.
Design and development
While developing the T31 axial turboprop in 1943 General Electric realized that they had the resources to design an axial flowturbojet at the same time as their centrifugal-flowJ33 engine. They recognized the axial would have more potential for the future and went ahead with the TG-180 engine.[1] GE axial compressor designs were developed from the NACA 8-stage compressor.[2]
Sectioned J35 at the National Naval Aviation Museum, Pensacola, FL. The 11-stage compressor is painted blue (the stators have been removed), the combustors are red, the turbine is unpainted. The teardrop-shaped openings along the outer edge of the turbine are the air channels used to cool the blades.Cutaway of J35 combustor domeCutaway of J35 fuel atomizer
The engine had its starter and accessories (fuel control, fuel pump, oil pumps, hydraulic pump, RPM generator)[3] mounted in the center of the compressor inlet. This accessory layout, as used on centrifugal engines, restricted the area available for compressor inlet air. It was carried over to the J47 but revised (relocated to an external gearbox) on the J73 when a 50% increase in airflow was required.[4] It also had an inlet debris guard which was common on early jet engines.
GE developed a variable afterburner for the engine, although electronic control linked with engine controls had to wait until the J47.[5] Marrett describes one of the potential consequences of manual control of the engine and afterburner on a turbine engine: if the afterburner lit but the pilot failed to ensure the nozzle opened, the RPM governor could overfuel the engine until the turbine failed.[6]
Operational history
The General Electric J35 first flew in the Republic XP-84 Thunderjet in 1946. Late in 1947, complete responsibility for the development and production of the engine was transferred to the Allison Division of the General Motors Corporation and some J35s were also built by GM's Chevrolet division. More than 14,000 J35s had been built by the time production ended in 1955.
^"AERO ENGINES 1956". Flight and Aircraft Engineer. 69 (2468): 567–597. 11 May 1956. Retrieved 16 March 2019.
^"Aero Engines 1957". Flight and Aircraft Engineer. 72 (2531): 111–143. 26 July 1957. Retrieved 16 March 2019.
^General Electric Company (1979). Seven Decades of Progress: A Heritage of Aircraft Turbine Technology (1st ed.). Fallbrook: Aero Publishers Inc. p. 76. ISBN0-8168-8355-6.
^Marrett, George J. (2006). Testing death : Hughes Aircraft test pilots and Cold War weaponry (1st ed.). Naval Institute Press. p. 21. ISBN978-1-59114-512-7.
^Wilkinson, Paul H. (1953). Aircraft Engines of the World 1953 (11th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 60–62.
^Wilkinson, Paul H. (1950). Aircraft Engines of the World 1950 (11th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 48–49.
^Bridgman, Leonard (1955). Jane's all the World's Aircraft 1955–56. London: Jane's all the World's Aircraft Publishing Co. Ltd.
^Wilkinson, Paul H. (1957). Aircraft engines of the World 1957 (15th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 70–71.
Further reading
Wikimedia Commons has media related to Allison J35.
Kay, Anthony L. (2007). Turbojet History and Development 1930–1960 Volume 2:USSR, USA, Japan, France, Canada, Sweden, Switzerland, Italy and Hungary (1st ed.). Ramsbury: The Crowood Press. ISBN978-1861269393.
