What is spool in jet engine?

Question

I recently heard someone saying "Oh that aircraft got a twin spool engine". What does spool mean?? Thnx in advance...

Answer 1

Singles spool engines have 1 shaft, on which is installed a compressor on forward portion of the shaft, and a turbine in the aft portion of the shaft - A twin spool engine has 2 shafts, which rotate independently - Each shaft has again, a compressor in the forward portion and turbine in the aft portion of the shaft - There is an "inner shaft" and an "outer shaft" -



Note that generally, the spools are sometimes referred to as low pressure spool (or the RPM is expressed as N1 RPM) and the high pressure spool (where the RPM expressed as N2 RPM) - Thereby also the names "low pressure compressor" (or turbine) and "high pressure compressor" (or turbine) -



On two spool engines, the engine accessories are driven by the high pressure spool (or N2 spool) - The starter of the engine will activate rotation of N2 shaft (or spool) -



There are engines with 3 spools - the RR RB-211 is one of these -



You will sometimes hear pilots use the wording "the engine is spooled" - means that the engine has sufficient RPM to accelerate very fast (bleed valves are closed) - An "unspooled engine" takes a lot of time to accelerate in RPM (bleed valves are open) -



To keep a JT9D engine spooled (the 747 engine) - takes minimum 80% N1 RPM -

.

Answer 2

Most modern jets use twin spool engines. Rolls Royce uses three spool engines.



The compressor and turbine are linked by a shaft. In a twin spool engine there is an outer and an inner shaft, the last stage of the turbine drives the fan and sometimes the front few compressor stages, the rest of the turbine stages are linked to the rest of the compressor. Using more than one shaft allows the compressor and the fan to run at radically different speeds, you can't run the compressor and turbine efficiently at the relatively low speed the compressor needs. Another approach is to gear the fan down from the turbine speed.

Answer 3

Spool Meaning

Answer 4

Spool Definition

Answer 5

A spool is the shaft upon which the various power turbine and compressor sections rotate. A two spool engine employs concentric shafts The low pressure compressor and turbine rotate on one shaft, and the high pressure turbine and compressor rotate on the other spool. http://en.wikipedia.org/wiki/File:Turbofan_operation.svg



Try learning how to use an internet search engine.

Answer 6

Okay ill give you the simple answer these others are bit over the top. A spool is simply a turbine/compressor combination linked together. Air is sucked in to engine compressed by compressor then combusted and flows through turbine which in turn spins the compressor.