How Does Axial Flow Affect Flow Rate and Head in Turbomachinery?

[ahmedbadr]

iam confused so much about some concepts of turbomachinery.
according to the classification of rotodynamics devices there are 3 types radial flow,axial flow and mixed flow and axial flow gives higher flow rate compared to radial flow and lower head.

so my question is what is meant that axial flow gives higher flow rate and lower head ?

cant we convert kinetic energy(flow rate) to pressure (head) and vise verse so the point is how much the power input to the device so we can convert this power to to flow rate or head regardless the type of rotodynamic(axial or radial) i.e the diection of flow

another question does the design of impeller or propeller has to do something about that?

finally i hope if you can get m,e a source (website or books)that clearify this point and clarify the the design of impellers and animations .

 

[ahmedbadr]

no one answers?

 

[Q_Goest]

cant we convert kinetic energy(flow rate) to pressure (head) and vise verse so the point is how much the power input to the device so we can convert this power to to flow rate or head regardless the type of rotodynamic(axial or radial) i.e the diection of flow

Yes, this is all perfectly correct. The type of compressor doesn't really have anything to do with how much the pressure is raised or how much flow can be developed. Flow and pressure are independant of the method used to compress a gas.

iam confused so much about some concepts of turbomachinery.
according to the classification of rotodynamics devices there are 3 types radial flow,axial flow and mixed flow and axial flow gives higher flow rate compared to radial flow and lower head.

so my question is what is meant that axial flow gives higher flow rate and lower head ?

When it is said that an axial flow compressor produces a higher flow rate and less pressure (ie: head), it is only meant that there are typical niches that are more suitable for specific types of compression equipment. A reciprocating compressor could do just as much flow as an axial flow compressor, but we wouldn't use a recip in a jet engine. We'd use an axial compressor because there are inherent advantages to one type over another. All the statement is really saying is that "typically" an axial flow compressor will be used to produce flow rates that are higher than radial flow centrifugal compressors or that centrifugal compressors are typically used to provide more pressure than axial compressors. For that matter, reciprocating compressors are typically used when higher pressure and less flow is required. The statement is merely a generalization on the type of compressor used for an application.

 

[tyroman]

You ask for "source (website or books)that clearify this point"...

have you looked at;
http://books.google.com/books?id=Euo81Pjuj-YC&dq="head+capacity"+compressor&source=gbs_navlinks_s

books by;
Meherwan P. Boyce
Klaus H. Lüdtke
Royce N. Brown
Paul C. Hanlon

 

[ahmedbadr]

turbomachinery

i want to know the effect of changing the rotational speed and the mass flow rate on the pressure ration of axial compressor and centrifugal compressor and the effect of the same two parameters on the gas turbine ??
it would be better if anyone can tell abt website that can i get these information from

 

[Turbodog]

In general you can think of the affinity laws for a rough estimation of changes in operating conditions of compressors. i.e. flow is proportional to shaft speed, and head is proportional to the square of shaft speed. Really, you would need to consult the OEM of the compressor of performance curves at whatever operation point you have in mind.
Usually you can get predicted discharge pressure, temperature, and efficiency versus flow at one or more speeds.
Normally gas turbines have a relatively small speed range otherwise the efficiency suffers.

 

[Turbodog]

Impeller design has everything to do with compressor properties. The blade tip width, blade angle relative to tangent, impeller diameter, diffuser width, return channel shape, impeller inducer shape, impeller diameter all affect the amount of head, flow, and efficiency a centrifugal stage can achieve. Similarly, an axial's properties are affected by rotating blade shape, stationary blade shape, and angle.

 

[berkeman]

(merged 2 threads with the same title and author)

 

[jack action]

i want to know the effect of changing the rotational speed and the mass flow rate on the pressure ration of axial compressor and centrifugal compressor and the effect of the same two parameters on the gas turbine ??
it would be better if anyone can tell abt website that can i get these information from

I don't know your knowledge level about this, but it's a relatively difficult machine to simplify. http://books.google.com/books?id=s4...urbomachinery&hl=fr&cd=1#v=onepage&q&f=false", you can access part of a book that explain the velocity diagrams and the energy transfer.