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The Rolls-Royce Conway, the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine. Civilian turbofan engines of the 1960s, such as the Pratt & Whitney JT8D and the Rolls-Royce Spey, had bypass ratios closer to 1 and were similar to their military equivalents.
Turboprop, turboshaft and turbofan engines have additional turbine stages to drive a propeller, bypass fan or helicopter rotor. In a free turbine the turbine driving the compressor rotates independently of that which powers the propeller or helicopter rotor. Cooling air, bled from the compressor, may be used to cool the turbine blades, vanes ...
In 1959, important orders for the engine were the Boeing 707-120B and Boeing 720B when American Airlines ordered one 707 powered by JT3D turbofans and KLM ordered a JT3D-powered Douglas DC-8. Earlier 707s and DC-8s had been powered by the JT3C and JT4A turbojets, and the improved efficiency of the turbofan soon attracted the airlines. A JT3D ...
The CFM56 is a high-bypass turbofan engine (most of the air accelerated by the fan bypasses the core of the engine and is exhausted out of the fan case) with several variants having bypass ratios ranging from 5:1 to 6:1, generating 18,500 to 34,000 lbf (80 kN to 150 kN) of thrust. The variants share a common design, and differ only in details.
The geared turbofan is a type of turbofan aircraft engine with a planetary gearbox between the low pressure compressor / turbine and the fan, enabling each to spin at its optimum speed. The benefit of the design is lower fuel consumption and much quieter operation.
XF9-1 on a test run. The XF9-1 is a twin-spool axial-flow afterburning turbofan with a dual redundant FADEC, consisting of a 3-stage fan, a 6-stage high-pressure compressor, an annular type combustor, a single-stage high-pressure turbine, a single-stage low-pressure turbine, an afterburner, and a convergent-divergent nozzle.
The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. [1] A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.
An animation of a turbofan engine.This is a 2-spool, high-bypass turbofan typical of those found on modern passenger aeroplanes. Turbofan engines provide good thrust at speeds at up to approximately Mach 1.6, at higher speeds turbojet engines are more effective whilst turboprop engines are more effective at low speeds.