General Electric YJ93

YB-58 at Edwards AFB with GE J93 engine pod

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).^[1]

Design and development

The YJ93 started life as the General Electric J79-X275, an enlarged version of the General Electric J79 turbojet with "275" meaning Mach 2.75, the engine's target operating speed.^[2] This design evolved into the X279 when Mach 3 cruise became a requirement, and ultimately became the YJ93.^[3]

The engine used a special high-temperature JP-6 fuel. The six YJ93 engines in the XB-70 Valkyrie were capable of producing a thrust to weight ratio of 5:1 allowing for a speed of 2,000 mph (3,200 km/h) (approximately Mach 3) at an altitude of 70,000 feet (21,000 m).^[4] The first engine went on test in September 1958 and featured advanced technology achievements such as electrolytically drilling longitudinal air cooling holes in the turbine blades.^[2]

The XF-108 interceptor was cancelled outright, and the B-70 project was re-oriented to a research project only.^[5]

Variants

J93-GE-1: 24,800 lbf (110 kN) thrust with afterburner.^[6]
J93-GE-3: Production variant produced in small numbers for the North American XB-70 Valkyrie program.
J93-GE-3R: Variant with thrust reverser, 27,200 lbf (121 kN) thrust with afterburner.^[7]
J93-GE-3AR: Variant intended for the North American XF-108 Rapier.

Applications

Specifications (J93-GE-3)

Data from Aircraft engines of the World 1966/77,^[8] Military Turbojet/Turbofan Specifications,^[9] North American XB-70A Valkyrie^[1]

General characteristics

Type: Turbojet with afterburner
Length: 237 in (6,000 mm)
Diameter: 52.5 in (1,330 mm)
Dry weight: 5,000 lb (2,300 kg)

Components

Compressor: 11-stage axial
Combustors: Annular with 36 dual fuel nozzles
Turbine: Two-stage axial
Fuel type: Special high-temperature JP-6 Fuel to MIL-F-25656
Oil system: Return oil spray system at 60 psi (410 kPa)

Performance

Maximum thrust: 22,000 lbf (98 kN) dry; 30,000 lbf (130 kN) with afterburner
Air mass flow: 275 lb/s (125 kg/s)
Turbine inlet temperature: 1,149 °C (2,100 °F; 1,422 K)
Specific fuel consumption: 0.700 lb/(lbf⋅h) (19.8 g/(kN⋅s)) dry; 1.800 lb/(lbf⋅h) (51.0 g/(kN⋅s)) wet
Thrust-to-weight ratio: 6

References

Wikimedia Commons has media related to General Electric YJ93.

^ a b Jenkins, Dennis R.; Landis, Tony (2002). North American XB-70A Valkyrie. North Branch [USA]: Specialty Press Publishers and Wholesalers. ISBN 1-58007-056-6.
^ a b Eight Decades of Progress : A Heritage of Aircraft Turbine Technology. GE Aircraft Engines. 1990. p. 117. LCCN 90082948.
^ Jenkins, Dennis R. and Tony R. Landis. Valkyrie: North American's Mach 3 Superbomber. North Branch, Minnesota: Specialty Press, 2005. ISBN 1-58007-072-8.
^ National Museum of the USAF Retrieved: December 21, 2016
^ NB-58A Testbed for General Electric J93 Archived 2008-07-24 at the Wayback Machine
^ "Characteristics Summary: F-108A" (PDF). US Air Force. 2 May 1958. Retrieved 15 December 2018.
^ "Characteristics Summary: F-108A" (PDF). US Air Force. 15 December 1958. Retrieved 15 December 2018.
^ Wilkinson, Paul H. (1966). Aircraft engines of the World 1966/77 (21st ed.). London: Sir Isaac Pitman & Sons Ltd. p. 83.
^ "Military Turbojet/Turbofan Specifications". www.jet-engine.net. Archived from the original on 2 October 2011. Retrieved 31 December 2017.