# Fluid Machinery (Gas Turbines and Compressors)

1. Oct 19, 2007

### CHeema

Dear All!!

I am in need of the follwing few questions regarding Gas Turbines and Compressors. It will be very nice and helpful if you people reply....an earliest reply will be appriciated

why the flow channel in turbomachines usually does not have parallel hub and casing walls

how the static pressure changes qualitatively between in- and outlet in an axial action and reaction turbine.

Sketch a qualitative pressure distribution over an airfoil.

why compressor blades feature little curvature and are comparatively thin whereas turbine blades are highly curved and tend to be thicker.

why it is more difficult to diffuse (i.e. decelerate) than to accelerate flow.

how the cross section area changes for a parallel wall annular flow channel upon change in flow angle.

Explain why the flow channel in turbomachines usually does not have parallel hub and casing walls and how you as designer would determine its shape.

I know these are alot of questions but i am in real need of these...

Regards

Cheema

2. Oct 19, 2007

### Staff: Mentor

Sounds like homework...

3. Oct 19, 2007

### CHeema

hmmm!!! not homework but some questions asked by the teacher....:)

4. Oct 22, 2007

### minger

how the static pressure changes qualitatively between in- and outlet in an axial action and reaction turbine.

Action and Reaction Turbines/Pumps are by definition how the static pressure changes, and in what regards it changes to. By definition, every turbine has a certain action and reaction coefficient, so a reaction turbine is a turbine with a high reacion (duh, haha). Anyways, just look up what the definitions are and it will tell you how the pressure changes.

Sketch a qualitative pressure distribution over an airfoil.

For this, just follow a fluid particle on its trip over and under the airfoil. Where you think the particle is slowing down, you will have an favorable pressure gradient, or the pressure will be increasing. Where the particle speeds up, there is an unfavorable pressure gradient, the pressure is decreasing. hint: at the leading edge where a particle abruptly stops, there will probably be pretty high pressure.