THE HISTORY OF AXIAL COMPRESSORS
What is an Axial compressor and how does it work?
Just the same as a turbo compressor, this type of machine uses the dynamics of moving air to produce compression.
Most homes will have a simple axial compressor, in the shape of a cooling fan. This fan will comprise of a few blades mounted on to a hub and this hub rotates causing air to be sucked in at one side and blown out of the other. The pressure created by the fan will be fairly small, after all it has been designed to move large volumes of air rather than blow up a car tyre.
The industrial axial compressor uses the same principle but refines the components to increase efficiency and to produce a greater pressure. For a start the fan assembly will have a lot more blades and these will have been designed and machined to cut the air within the hub or casing. After all, we don't want any spillage off the tips of the blades, we want all of the air to pass in at one end and out of the other. For this reason the case is a snug fit with just enough clearance to cope with expansion due to heat and strain.
The hub carrying the fan blades is called the rotor and the case in which the rotor is housed is called the stator. The second difference to a domestic fan is the series of static blades fixed inside the stator that have been designed to catch the air just after it leaves the rotor assembly. This ring of static blades is a diffuser and not only does it catch the air, it slows it down. This turns the kinetic energy due to the high velocities into static pressure.
The air is still moving forward, despite having passed through the diffuser and it enters another rotor assembly contained within a second stator. The design of the second rotor is different to the first, because the inlet pressure is higher and the physical volume occupied by the air is different. The air picks up velocity as it passes through the assembly before it is discharged into another diffuser.
A multi-stage axial compressor will comprise of numerous rotors and diffusers, each reducing in diameter as the air becomes more and more compressed.
Where did the axial compressor come from?
The age of steam produce most of the innovations needed to push forward the development of the early axial compressors. The with the introduction of the jet engine, vast sums of money was injected by aircraft manufacturers to produce a more efficient and quieter engine. This impacted heavily upon the compressor designers and spilled over into general engineering.
Why use an axial compressor?
The largest volume users are aircraft and aero-engine manufacturers. The unique properties allow this type of design to be easily incorporated into a 'through-flow' engine such as is used on todays modern aircraft