Centrifugal Pump by Ulf_vom_Mond

Last crawled date: 3 years, 4 months ago

Summary
Please read the description carefully. Not because it is relevant or helpful, but because i think its funny and interesting.
There already exist a lot of centrifugal pump designs on Thingiverse, so just go ahead and download this one: https://www.thingiverse.com/thing:4839
Still here? Ok, so i designed another one because the existing models didn't satisfy me. I also made another design myself previously, but i was still not happy.
The reason is that i dont know how all the pumps are designed.
Why do some pumps have straight blades, some two dimensional curved blades and some even three dimensional curved blades?
Why are some pumps thick and have a small diameter while others are thin with a large diameter?
Why do some pumps rotate forward and some backward? (Towards outer/inner edge of the blades)
How is the shape of the curved blades determined? Are they just drawn how they look good? How do i know the blades dont only look good for me, but for the water?
How much blades should the impeller have?
How i answered these questions can be found in How to design a centrifugal pump
The next thing bothering me was how to compare the different pump designs. Every design just named centrifugal pump (like mine) doesnt help much.
After some research i found two numbers to rate pumps:
The head they produce. Its just the height the pump can push water upwards.
The flowrate, thats the amount of water they can move per amount of time.
My experiments have established the following experience:
The first thing i found out is that the head of my pump is definitely larger than the border of my sink. The second thing i found out is that if i raised the end of the tube above 1.4 m above my pump, water still flows and shortly after that the cap comes off the pump case. On another attempt i got to 2 m head (which equals 0.2 bars of pressure) until the flow stopped without the pump breaking.
The flowrate wasn't as wet to measure and resulted in 7.5 litres per minute at a head of 0 m.
Another effect occured when operating the pump which may be taken into account: It was strong enough to drive my parents crazy. (Not yet, but it will when they wake up the next morning)
EDIT: yes it did!!!
Maybe the pump could be even better if it was tight. More about that in Print settings and Post-Printing.
The first piece of useful information: All tests were conducted with a little 12 V DC motor which consumes 0.6 W on idle.
Print Settings
Printer brand:
Creality
Printer:
CR-10
Rafts:
No
Supports:
Yes
Resolution:
0,2 mm
Infill:
15 %
Filament_brand:
Conrad Electronics
Filament_color:
black
Filament_material:
PLA
Notes:
Supports are only needed under the outlet of the case part. I think the material doesnt matter, just be careful about the water temperature. You may want to increase flow rate, shell line count and top/bottom layer count in order to make the pump more tight.
Post-Printing and Assembly
The pump case has a 6.7 mm hole at the bottom. Most little DC motors have a little edge which fits there perfectly. The impeller itself supports a 2 mm motor shaft, however, you have to file one side of the shaft flat to make it fit. It has to be filed until it measures 1.7 mm from the flat side to the opposing point of the round side. This is to ensure that the shaft isnt slipping in the impeller and it works pretty good. See this image for reference:

When your motor shaft fits, just put the parts together in the most obvious way. If you do something wrong there, i cant help you, too.
Then you should seal everything up water tight.
You can either do this the proper way and use silicone, which is made for this purpose and definitely water proof.
Or you can do it like me and use a hotglue. With a hotglue i dont mean a drop or a little or some hotglue, i mean something like a lot or much or a whole stick of hotglue. Your hotglue gun shouldnt make pfft it should make BLAAAAAARGHHHH while applying the glue. If you arent sure whether you used not enough or to less hotglue, you should add more.
These images tell you more about a hotglue:

(Yes, the tube adapter broke of in the second image. Be careful when removing the tube)
The tube adapters are designed for aquarium tubes with 12 mm inner diameter and 16 mm outer diameter. If the tubes dont fit, heat them up in a bowl of boiling water to make them soft and then push them over the adapters.
How to design a centrifugal pump
I used Fusion 360. You can access the design here: https://a360.co/3ixGKq7
About my used tolerances:
Everything that should fit tight together has a gap of 0.15 mm like the cap and the case.
The spinny thingy and the not so spinny thingy have a gap of radially 0.5 mm and axially 0.8 mm.
This part is really important to me as it was hard to find any solid information on the internet.
The things i found and used while designing are the following:
Centrifugal pump impeller vane profile
This article describes a conventional impeller blade design method in the Section 5.3 CONSTRUCTION OF VANE PROFILE. Thats the method i used and its called circular arc method.
A Review of Different Blade Design Methods for Radial Flow Centrifugal Pump
Here, further blade design methods are discussed which also may be helpful.
The Theory and Design of a Centrifugal Pump
Thats a bachelor thesis from 1911 which handles all the theory, but misses any practical advice on "how to do this" or "how to do that" but its quite interesting to read. Simply the fact that it was written on a typewriter made me curious.
Pump Handbook by Igor J. Karassik
This document probably contains every piece of information for every pump type on nearly 1800 pages (Why is this allowed to be called a handbook? I am happy that its digital because i could never even lift it). Its really interesting and has a lot of useful, detailed information. If you dont find your seeked knowledge there, it doesnt exist yet.
DESIGN AND ANALYSIS OF CENTRIFUGAL PUMP IMPELLER USING ANSYS FLUENT
Ajith MS made a good job simulating and comparing the different impeller blade design methods here. Its a nice addition if the 1800 pages werent enough for you.
Investigation of a centrifugal pump impeller vane profile using CFD
Another paper which researches the fluid dynamics of different impellers with simulation.
After reading a lot about pumps, this is how my sketch looks in Fusion 360:
I also included the impeller profile as a .svg and a .dxf file if you want to have a closer look.
Different pump sizes
If you need a different height, diameter, motor shaft, tube size or something else feel free to ask and i will upload your requested size. Thats not hard for me, so dont hesitate.