Pratt & Whitney PW4000 Engine
Pratt & Whitney PW4000 is a commonly used jet engine, with 2500 units that have been built since it was first introduced in 1984. These jet engines have been powering many widebody aircraft such as Airbus A300, A330, Boeing 747-400, 767, and 777. The Pratt & Whitney PW4000-112 is a variant of the Pratt & Whitney PW4000 jet engines specifically powering Boeing 777s. The “112” at the end stands for the diameter of the fan in an engine which is 112 inches. The thrust capacity of this Engine ranges from 74000 lb-ft to 98000 lb-ft. According to the thrust capacity, the PW4000-112 engine is subdivided into the following categories,
Where the last two digits indicate the thrust level. For example, the PW4074 engine can produce 74000 lb-ft of thrust and the PW4098 engine can produce 98000 lb-ft of thrust. According to the power output, these engines are used in Boeing 777-200, 200ER and300 aircraft.
Working of Pratt & Whitney PW4000-112 Engine.
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| Section view of Pratt & Whitney PW4000 Engine |
Similar to other turbofan jet engines, the Pratt & Whitney PW4000-112 engine works on the basis of an open cycle gas turbine. The thrust required to create the motion of the aircraft is based on Newton’s 3rd law of motion. First, as the engine starts, the air enters and is exhausted by a fan creating most of the thrust. Some air enters the low-pressure compressor, where it is compressed before reaching the high-pressure compressor. The HP compressor will compress the air furthermore before reaching the combustor. The compressed air then enters into the combustor where it mixes with fuel. The air-fuel mixture is ignited to start the combustion process. Which causes expansion of the mixture as the temperature rises. The airflow continues to expand after combustion and enters the high-pressure turbine, forcing the blades to rotate the HP turbine. The HP turbine is connected to the HP compressor via a hollow outer shaft. The shaft drives the rotation of HP compressor blades. The expanding exhaust gases then enter the low-pressure turbine. Where the exhaust gas forces the turbine blades to rotate the LP turbine. The LP turbine drives the LP compressor and the fan via an inner shaft. After that, the exhaust gas leaves the LP turbine forming a jet and enhancing the thrust. And the flow of air continues throughout the process.
