Monday, September 20, 2010

Pratt & Whitney F135

The Pratt & Whitney F135 is an afterburning axial-flow turbofan engine which was developed for the F-35 Lightning II fighter aircraft. The F135 is a two-shaft engine which consisted of an axial three-stage low-pressure compressor and a six-stage high pressure compressor. The hot section features an annular combustor with a single-stage high-pressure turbine unit and a two-stage low-pressure turbine. The afterburner features a variable converging-diverging nozzle.

While the conventional and carrier aviation engines, the F135-PW-100 and F135-PW-400, have a maximum (wet) thrust of approximately 43,000 lbf (191 kN) and a dry thrust of approximately 28,000 lbf (125 kN), STOVL variant, F135-PW-600, delivers the same 43,000 lbf (191 kN) of wet thrust as the other types in its conventional configuration. In STOVL configuration, the engine produces 18,000 lbf (80.1 kN) of lift thrust. The STOVL variant engages a clutch to extract around 35,000 shp (26,000 kW) from the LP turbine to turn the forward lift fans, while switching power cycle from mixed (turbofan) to unmixed (turboshaft). Power is transferred forward through shaft to a bevel gearbox, to drive two vertically mounted contra-rotating fans.

The uppermost fan is fitted with variable inlet guide vanes and the fan discharges efflux (low-velocity unheated air) through a nozzle on the underside of the aircraft. This cool air from the lift fan has the added benefit of preventing hot exhaust gases from the core section from being reingested into the engine while hovering. Finally, bypass duct air is sent to a pair of roll post nozzles and the core stream discharges downwards via a thrust vectoring nozzle at the rear of the engine.

Specifications for the Pratt & Whitney F135-PW-100

Type: Afterburning Turbofan engine
Length: 220 in (5.59 m)
Diameter: 51 in (1.29 m)
Dry weight: classified / unpublished
Compressor: Axial 3 stage low-pressure compressor, 6 stage high-pressure compressor
Combustors: Short, annular combustor
Turbine: Single stage high pressure turbine, two stage low pressure turbine
Maximum thrust: 43,000 lbf (191.35 kN) max, 28,000 lbf (124.6 kN) intermediate
Specific fuel consumption: 0.886 lb/(hr*lbf) or 25 g/kNs (w/o afterburner)

Pratt & Whitney F135 Engine