Cavitation test

[DreamThinkBuild]

Hi All,

Had a weekend project of testing cavitation. Drew up the design based on different sources on the net. Mainly 45 degree angled holes leading to a cone shape end. Took 1 hour and 30 minutes to print, so gave me time to cook up a can of beans and have them for lunch.

This test was also to see if cavitation could be accomplished with plastic (LOL). I ran it off a drill with two speed settings 1000rpm and 3600rpm, tried both clockwise and counterclockwise. The wheel distance to the bean can was .5 mm using just tap water. I could've put oil but the ABS would probably melt.

In this design I didn't notice any minute heating (digital thermometer) with just one printed ring, most show more than one ring, I ran it until the drill motor got hot <5 minutes. Did learn that ABS plastic is pretty strong even when getting banged around at 3600 rpm (safety glasses and Kevlar butcher gloves were worn for protection).

If this doesn't pan out I'll stick some thin cylinder magnets in it and see if I can turn it into a magnet/pulse motor.

Attached is a picture of the wireframe to show the internal structure  and the printed part connected to drill.

[gotoluc]

Thank you DreamThinkBuild for taking the time to post your results even though they're not so positive. This will be helpful to others!

Luc

[wings]

test

http://www.fieldlines.com/index.php?topic=129151.0

important: rotor diameter - rotational speed - operating pressure

some suggestions in the patent

US 5188090

note pressure OUT less than pressure IN (important for cavitation)

RPM   5000   3460
rps   300000   207600
HP   5   7.5
watt   3676   5515
       
Rotor Diameter (inch)   7.3   10
Rotor Diameter (mm)   185   254
     
Tangential Speed (m/sec)   48.5   46.0
     
Pipe Diameter (inc)   0.5   0.75
Pressure IN "pounds"   75   65
Pressure IN (kgf/cm^2)   5.3   4.6
Pressure IN (Bar)   5.2   4.5
     
Pressure OUT "pounds"   60   50
Pressure OUT (kgf/cm^2)   4.2   3.5
Pressure OUT (Bar)   4.1   3.4
     
Temperature (F°)   300   300
Temperature (C°)   149   149

[DreamThinkBuild]

Hi Wings,

Thank you for that insightful information.

I see that you need a fair amount of pressure and wider diameter on that design. I wonder how much ABS plastic can take in pressure. I didn't have any real pressure as it was open ended. Might be able to use it as a friction(not cavitating) water heater but it would need more mass, using mineral oil instead of water.

This is one of the patents that I went off of.

US6910448: Apparatus and method for heating fluids
http://www.google.com/patents/US6910448

[wings]

Hi Wings,

Thank you for that insightful information.

I see that you need a fair amount of pressure and wider diameter on that design. I wonder how much ABS plastic can take in pressure. I didn't have any real pressure as it was open ended. Might be able to use it as a friction(not cavitating) water heater but it would need more mass, using mineral oil instead of water.

This is one of the patents that I went off of.

US6910448: Apparatus and method for heating fluids
http://www.google.com/patents/US6910448

40-70 PSI is typical house water pressure

IMO
- lower pressure is ok for cavitation but you have to introduce some variable restrictions in the INlet and OUTlet in order to test the best differential pressure

- cavitation bubbles starts when local pressure is below liquid vapor pressure and this is function of static and dynamic pressure (i.e. speed related - function of rotor diameter and rotational speed RPM) cavitation is the implosion of the vapor bubbles it happen when the sigma value is below 1.5

- ABS or plastic is good for short test


- use water no oil except you want to obtain biodiesel - http://hydrodynamics.com/   


- youtube
http://www.youtube.com/watch?v=UBxpn6odtcA&feature=player_embedded

- some useful formula for cavitation here:
http://www.calculatoredge.com/mech/cavitationno.htm

- some information on cavitation
http://web.mit.edu/hml/ncfmf/16CAV.pdf
http://www.flowserve.com/files/Files/Literature/ProductLiterature/FlowControl/Flowserve/FCENBR0068-00.pdf