On a axial flow turbo fan or turbo jet engine what comes first the rotor or the stator?

Question

I've been let to understand that one stage consists of a row of rotors and stators. But I'm not sure which comes first? Does the front fan blades make the first part of the stage (rotor) with a stator section behind? And so on.. Or on a fan engine with a booster the first stage is the stator and then rotor (after the fan blades). Secondly do all engines have inlet guide vanes? I'm assuming not or we would physically see them in front of the the big fan engines or do they appear later on.. Maybe in the HP section?

Hope this makes sense and any images with an explanation would be appreciated.

Thanks

Answer 1

There are two aspects to consider here:

• The aerodynamic principle:

  The simple aerodynamic principle requires a compressor stage to have first a rotor followed by a stator.

• The constructive aspects:

  Constructive aspects to be considered are:

  a) Pre-rotation of air before the rotor: in order to reduce the relative speed of the airflow on the rotor blades (to avoid the shock waves of supersonic airflow) a set of stators can be placed in front of the rotor; this will rotate the air towards the direction of rotation, reducing by this the relative speed of the airflow on the rotor blades; even in such cases a stator stage is required after the rotor.

  b) Bearing location: some designs put the bearing behind the rotor, other designs put the bearing in front of the rotor; in such case the bearing before the rotor needs to be supported by a system of vanes.

Consequently, many smaller diameter (or high speed military design) engines will take advantage of a) and b) above and have a stator in front of the first stage compressor.

To answer the same questions on turbines, there the aerodynamic principle requires to have first a set of stators and then a rotor.

Answer 2

Rotor, then stator, in as many subsequent pairs as the engine is designed to contain.

Source: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node92.html

Answer 3

In an axial compressor, the air is compressed by grabbing it with a moving blade and squeezing it against a fixed surface. This is a very simplified representation, of course, but it gets the idea across.

For this reason, the rotor goes first, the stator follows.

Inlet guide vanes are only present in some engines. They do not replace a stator, only make the rotor more efficient, but add their own drag.