Design and Development
The JT15D is rare among modern turbofans in that it uses a centrifugal compressor as its main high-pressure system. This was a common feature of early jet engines, but was quickly replaced by axial compressors in most roles due to its large frontal size. In the turbofan role most of the jet thrust is generated by the cold air blown past the engine, and the internal "jet" portion is quite small. In this role the high single-stage compression of the centrifugal design has advantages, and the main reason most small turbofans don't use them is that they are often developments of previous turbojet designs.
In the JT15D the fan blows about 70% of the air into the bypass duct, producing most of the overall thrust. On JT15D-4 models and above there is a small "booster" axial stage just behind the fan which is running at the same speed as the fan and directing the remaining 30% of the airflow into the engine core. This air is further compressed by the centrifugal stage, and burned in a reverse-flow annular combustor. The hot gases flow through a "high-pressure" turbine that drives the centrifugal stage, and then two more turbines driving the fan and booster.
Read more about this topic: Pratt & Whitney Canada JT15D
Famous quotes containing the words design and/or development:
“Nowadays the host does not admit you to his hearth, but has got the mason to build one for yourself somewhere in his alley, and hospitality is the art of keeping you at the greatest distance. There is as much secrecy about the cooking as if he had a design to poison you.”
—Henry David Thoreau (1817–1862)
“Such condition of suspended judgment indeed, in its more genial development and under felicitous culture, is but the expectation, the receptivity, of the faithful scholar, determined not to foreclose what is still a question—the “philosophic temper,” in short, for which a survival of query will be still the salt of truth, even in the most absolutely ascertained knowledge.”
—Walter Pater (1839–1894)