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Rolls Royce AE1107C Liberty
The Rolls Royce AE1107C Liberty is the front runner in modern turbine technology and development for aviation turboshaft engines. It has an unprecedented power to weight ratio, incredible fuel efficiency, and fantastic reliability. The AE1107C utilizes common core technology to take advantage of economies of scale and shared R&D, lessons learned, and operating hours. Common core means that the AE1107C shares its core with two other engines in the same power class. The same identical gas producer core can be found in the medium bypass AE 3007 turbofan engine, as well as the AE 2100 turboprop engine, which itself was a development of the single shaft Allison T56 turboprop engine that has amassed countless hours on numerous military transports and commuter aircraft. In turboshaft form, the twin shaft AE1107C, formerly known as the Allison T406, produces a takeoff rating of 6,150 shaft horsepower with as much as 6,980 horsepower available for short periods of time in an emergency. The AE1107C is most widely known for its role in the Bell-Boeing V22 Osprey Tiltrotor aircraft, whose two turboshafts reside in nacelles that can be rotated through 90 degrees to convert from vertical takeoff mode into horizontal wingborne flight. The AE1107C is also slated to be the replacement for the General Electric T64 and Lycoming T55 turboshafts in heavy lift helicopter applications such as the Boeing CH-47 Chinook and the three engine Sikorsky CH-53 Super Stallion.
As can be expected from an engine that is derived from a large scale turbofan, the AE1107C is a completely axial flow engine. That means that the compressor and turbines are completely axial, the combustor is a through flow design, and the exhaust exits through an axial diffuser. Air enters through the axial flow engine inlet before being drawn up by the immense, ultra-efficient, 14 stage axial compressor. 14 stages of axial compression provide a pressure ratio of 16.7:1, before feeding that compressed air through a diffuser and to the annular, through flow combustor. The compressor features variable geometry stator vanes on the first 6 compressor stages; the variable stators can finely tune the airflow under a wide range of engine conditions, allowing for surge free operation and rapid acceleration and deceleration. The combustor is of annular design, with effusion cooling to allow for higher combustion temperatures. In effusion cooling, thousands of tiny holes are drilled into the combustor liner wall at an angle to the incoming airflow. As the compressor discharge air flows through these tiny holes, they carry away surface heat while providing an insulating layer of air to protect the metal. Hot gas from the burner exits through a cooled axial nozzle before feeding the two stage cooled compressor turbine, which drives the compressor and the accessory gearbox through a bevel gear and jackshaft arrangement. The remaining gas energy drives the uncooled two stage power turbine at a rated speed of 15,000 rpm, which drives a shaft that runs through the center of the gas producer shaft to provide a high speed, cold end power takeoff at the front of the engine. A torque tube carries the power away from the compressor face, and supports the output flange. This flange is connected to an airframe mounted rotor transmission to drive the helicopter rotor or prop rotors on the V22 Osprey. The exhaust is then allowed to escape to atmosphere through an axial diffuser, producing a very small amount of thrust as well. Accessories driven off include the usual high and low pressure fuel pumps, oil scavenge and pressure pumps, and an AC generator. Fuel control is via a dual FADEC control, the oil system is fully self contained to allow operation when the engine is in the vertical, and starting is via a pneumatic air turbine starter.
A highly efficient compressor with a high pressure ratio and a very high turbine inlet temperature allow the Rolls Royce AE1107C to be the absolute state of the art in helicopter turboshaft technology, with an unprecedented power to weight ratio and extremely low specific fuel consumption.
Rolls Royce AE1107C-Liberty Free Shaft Gas Turbine Engine
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