Semiopen impeller design

[einstein1977]

I have semi open impeller to design, but i don't know how to calculate hydraulic flow losses. Need help. It's semiopen impeller with radial flow blade

 

[insideman]

per4haps I can help. More details please.

 

[einstein1977]

What kind of details do you need? You mean flow rate, total head or pump dimensions( impeller diameter, blade angle, ...)?

 

[insideman]

What I need: total head, flow rate, material being pumped, RPM restrictions, if any.

 

[einstein1977]

H=175[feet]=53,34[m]
Q=335 US GPM=0.0211 m^3/s
n=2900 min^-1
ns=0.403
eff=73%
it is water pump

 

[insideman]

You gave me what it needs to do. Good! efficiency only 73%????
We can do better than that!

I'll be back at you in about 24 hours.

 

[Artisi]

If you have to design a pump impeller -- why have you chosen a semi-open impeller if the pumped product is water.
It also raises a good question, why are you trying to re-invent the wheel?


Naresuan University
Phitsanulok
Thailand

 

[vanstoja]

Is 73% efficiency a target value or is the efficiency of an impeller you are trying to replace? The Worthington efficiency versus specific speed curves show for your 1103 (RPM-GPM-ft.) specific speed show a typical(?) efficiency betwwen 71 and 74%. This can probably be bettered by using computational fluid dynamics (CFD) analysis design methods but whatever method is used specific loss values such as leakage, fluid friction, etc. are quite difficult to calculate accurately and require inputs such as seal clearances, surface finish and for semi-open impellers blade tip clearances all of which have recommended values depending on impeller size. You need a good centrifugal pump design book to even get started.

 

[einstein1977]

This pump characteristic are from pump catalog. I have performance curves and i took this values from it. This is my "final work for the university degree" and this is first time that i have to design pump with semi open impeller. I read some books but i didn't find anything about-how to design semiopen impeller-hydraulic losses. I have this calculations only for pumps with closed impeller. Can you tell me which book(books) are good start for semiopen impeller design?
I sad that, this is pump for water beacuse simplicity of the calculations-i think that is easier to do with water than any other fluid.

 

[vanstoja]

I don't know of any pump design books that cover semi-open impeller design. This is a relatively recent design innovation for pumps though it has been long used in centrifugal compressors whose literature addresses blade tip leakage losses rather extensively. The only difference between shouded and unshrouded impeller loss mechanisms should be blade tip versus wear ring seal losses so the centrifugal compressor tip leakage design criteria might be useable for pumps. For recent pump design practices see the ASME Journal of Fluid Mechanics where most of the recent articles employ CFD design methods.

 

[insideman]

A day late-

Expected efficiency = .88
Power required = 16.84 hp
Beta 2 = beta 1= 35 degrees (Log spiral vane)
Number of vanes = 14
D2 = 8.046" b2 = .278" cm2 = 15.28 fps
D1 = 2.240" B1 = .998" cm1 = 19.87 fps
Eye = 1.75" diameter Cm eye = 44.69fps
Psi =.543 Phi =.150 Solidity = 2.58
Alpha2 = 15.45 degrees No other work on volute was done.

We do not know the details of the various losses.