Core stream

In a turbofan engine, the core flow , also known as the primary flow , is the portion of the air mass flow sucked in by the engine that is directed into the core engine . There it is used in the so-called thermodynamic cycle process, among other things, for combustion with the fuel . The remaining portion of the sucked in air mass flow is diverted around the core engine and referred to as bypass flow , secondary flow or secondary flow . The ratio between secondary and primary flow is referred to as the bypass or bypass ratio .

The core flow makes up only a small part in modern, civil engines, while the bypass flow can make up eight to nine times the volume, but with the Pratt & Whitney PW1000G it is twelve times as much. With these high bypass ratios, the sheath flow develops most of the propulsive force; then the core engine is often referred to as a (hot) gas generator, since its main task is to deliver a high-energy (hot, fast high-pressure) gas flow for the turbine stages of the fan .

The core flow passes through a multi-stage low and high pressure compressor, the combustion chamber, a multi-stage high and low pressure turbine and finally a nozzle. At the nozzle, the core and sheath flow combine again to form the thrust jet.

Although the real purpose of the core stream usually is generating a hot gas to the turbine stages of the fans is for combustion in the combustion chamber is actually only about ¹ / ₅ of the core stream used; the remaining ⁴ / ₅ are used for cooling the combustion chamber wall and the turbine shovels used.

Individual evidence

1. ↑ ^{a b} Willy JG Bräunling: aircraft engines . Basics, aero-thermodynamics, ideal and real cycle processes, thermal turbo machines, components, emissions and systems. 4th edition. Springer, Berlin 2015, ISBN 978-3-642-34539-5 .