# How to determine the direction of rotation of components inside a gas turbine engine using the blade profile?

I am new to Gas turbine Engines. As of now,I am trying to understand the gas turbine engine DGEN 380 by the manufacturer Price Induction. So I have identified the components such as Intake fan,Planetary gearbox, Centrifugal Compressor,HP and LP turbine. However,I am not sure of identifying the correct direction of rotation for each of these rotating components based on blade profile. So if someone could explain it in a simple way,I shall be thankful.

https://minijets.org/fr/300-500/price-induction-dgen-380-390/

• I'm not sure about the other parts, but the intake fan runs clockwise when looking into it from the front. Commented Sep 10, 2018 at 17:28
• Possible duplicate of How does the fan in the jet engine suck in air while the engine is stationary? Commented Sep 10, 2018 at 17:39
• @ Ron Beyer I agree, and the turbine wheel seems to turn counterclockwise, also seen from the front of the unit. That's probably because of the planetary gearbox... Commented Sep 10, 2018 at 17:44
• @RonBeyer can you tell me how the direction is related to the blade profile for the intake fan? Commented Sep 10, 2018 at 19:39
• Take a look at the fan, and imagine it spinning. It has to grab air and force it backwards, so the "scoop" part grabs the air and pushes it in. It works the same way a desk fan or computer fan does, get one of those and spin it to see what direction the air moves. Commented Sep 10, 2018 at 19:42

If you know the direction of gas flow, you can determine the direction of rotation of axial flow components (like the fan and turbine in the example) by the angle of attack of the blades. Think of it intuitively--if you were to blow air through the engine in the same direction it flows during operation, which way would the blades windmill? The direction of windmilling is the same as the direction of powered operation, as long as the airflow is in the same direction.

Because their angle of attack, of the blades of the fan would deflect air flowing into the engine counterclockwise when viewed from the front, meaning the fan rotates clockwise when viewed from the front (or counterclockwise from the rear looking forward, which is the conventional way of expressing rotation).

For this particular engine, all other turbomechanical components rotate in the opposite direction as the fan, indicating that the low pressure shaft is connected to the fan using a gearbox that reverses the rotation direction.

This is the low pressure turbine and shaft:

The compressor rotates in the same direction as the high and low pressure turbines, and is attached directly to the high pressure turbine shaft with no gearbox. The high pressure turbine is axial flow and looks like a smaller version of the low pressure turbine, but the compressor is not an axial flow component, which makes the analysis slightly different.

Unlike in axial flow components, in radial flow components like this compressor (a synonym for a radial flow compressor is a centrifugal compressor), the airflow enters and exits in a different direction. The direction of flow also differs between energy-absorbing (turbine) and energy-dissipating (compressor) components. Gas enters radial flow turbines at the edge and flows inward, exiting at the center. In radial flow compressors, gas enters at the center and exits at the edge. You can determine the direction of rotation by imagining the forces the air would exert as it changes direction, similar to the windmilling axial flow components: