What is aircraft engine spool?
“Spool” is engineering shorthand for the combination of an engine compressor and high-pressure turbine that drives it using a connecting drive shaft. Each compressor segment is driven by its corresponding turbine using two separate drive shafts, with one inside the other.
Why do they spool twin engines?
A Two-Spool Engine The reason for doing this is that the low-pressure stages are larger in diameter, so they have higher tip speed for a given rotational speed. At the same time, the temperature is lower, and so too is the speed of sound. So, to keep the flow subsonic, they are designed to rotate at a slower speed.
How many spools does a turbojet engine have?
two spools
The hot gas generator employs two spools, like the turbojet shown in figure 10.1(a), and a third spool that is independent of the other two contains the fan and its own turbines. Fans of more than one stage have also been used, as have aft-mounted fans.
What is a multi spool engine?
A multi-spool gas turbine engine comprises a low pressure (LP) spool and a high pressure (HP) spool. The LP spool and the HP spool are independently rotatable about an axis. The LP pressure spool has an LP compressor and an LP turbine. The HP spool has an HP turbine and an HP compressor.
What is engine spool down?
rundown time The time taken by a turbine in a gas turbine engine to come to a complete halt after the engine has been switched off. It is one of the indicators of the state of health of an aircraft engine. Also called spool-down time.
What is a twin spool jet engine?
Well, the twin spool jet engines or low. A single spool jet engine is what is known as a turbojet engine. They have a single compressor rotor drum and its associated turbine. A two spool engine is what we call a low bypass ratio engine where you have two compressor stages.
Why do pilots speed up when landing?
Q: Why do pilots throttle up when landing? A: As a jet descends toward the runway, the pilot increases the power to maintain a specific descent rate (usually around 700 feet per minute). Jet engines (U.S. certified) can require up to eight seconds to accelerate from idle to maximum thrust.
What is a spool up?
(aviation, of a turbine engine) To increase in rotational speed, producing an increase in thrust. The large rotational inertia of the heavy compressor and turbine rotors makes the engine slow to spool up from idle.
What is spool in mechanical?
A spool is an assembly of pipe and associated components that can be pre-fabricated in the workshop for future installation and then shipped to site for assembling. A pipe spool drawing acts as a guide to plumbers to understand what they are encountering.