Design
The F135 is a two-shaft engine featuring a three-stage fan (low pressure) and a six-stage high pressure (HP) compressor. The hot section features an annular combustor with a single-stage HP turbine unit and a two-stage LP turbine. The afterburner features a variable converging-diverging nozzle.
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). The major difference between the -100 and -400 models is the use of salt-corrosion resistant materials.
The 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. Combined with thrust from the LiftFan (20,000 lbf/89.0 kN) and two roll posts (1,950 lbf/8.67 kN each), the Rolls-Royce LiftSystem produces a total of 41,900 lbf (186 kN) of thrust, almost the same vertical lifting force for slow speed flight as the same engine produces at maximum afterburner, without the extreme fuel use or exhaust heat as wet 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. Measured by lift thrust in full vertical lift mode, the engine operates as 43% turbojet, 48% turboshaft, and 9% turbofan.
Improving engine reliability and ease of maintenance is a major objective of the F135. The engine has fewer parts than similar engines which should help improve reliability. All line-replaceable components (LRCs) can be removed and replaced with a set of six common hand tools. Additionally, the F135's health management system is designed to provide real time data to maintainers on the ground, allowing them to troubleshoot problems and prepare replacement parts before the aircraft returns to base. According to Pratt & Whitney, this data may help drastically reduce troubleshooting and replacement time, as much as 94% over legacy engines.
The F-35 with F135/F136 engines are not designed to supercruise, but the F-35 can achieve a limited supercruise of Mach 1.2 for 150 miles.
In August 2010, Pratt & Whitney revealed that the F135 was able to generate in excess of 50,000 lb of thrust.
Because the F135 is designed for a fifth generation jet fighter, it is the second afterburning jet engine to use special "low-observable coatings".
Read more about this topic: Pratt & Whitney F135
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