×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Calculating tip speed?

Calculating tip speed?

Calculating tip speed?

(OP)
Can somone assist me with information on how to calculate the tip speed of a vacuum pump?  I'm trying to determine the slowest speed that I can operate the vacuum pump without the liquid ring collasping?  The actual capacity is not important.

Thanks!

RE: Calculating tip speed?

I don't know what is tip speed. But to check the minimum speed you can equate centrifugal force on liquid ring to it's weight. This is what is done with Centrifuges also.

If m is the mass of the fluid inside the pump then

mg = mV2/ro

Where g = acc. due to gravity
V = Speed of liquid ring (consider it equal to that of pump speed, ideally at no slip condition)
ro = Outer radius of the ring (so that you will get maximum minimum speed) For more accuracy you can do with (ro+ri)/2

If you know the volume of water and outer radius, it is easy to calculate inner radius by concentric cylinder volume formulae.


So V = (rg)1/2

But I fear this speed is for zero discharge.

Note: This is just a simple idea and I bear no responsibility.

Cheers!

RE: Calculating tip speed?

assuming that you mean tip of impeller/rotor then it should be easy:

You need to know the rotor diameter and the rpm.

Then tip speed=PI*diam*rpm/60)

Use preferred unit for speed in your "diam". Eg use meters and you get m/s

Best Regards

Morten

RE: Calculating tip speed?

Dear acfm,

A tip speed of min. 15 m/s is required to obtain a  stable liquid ring  (when using water or similar density, with atmospheric discharge pressure and for 50–100mbarA suction pressure).

Smaller liquid ring vacuum pumps are designed to be direct driven with tip speeds of 20-22m/s for cast iron and 22-25m/s for stainless steel.

Suction capacity V is (approx.) proportional to rotating speed : V1=V0.(n1/n0) while the  power absorbed P will be (approx.) P1=P0.(n1/n0)1,4

hope it helps,
Pierre
www.vacuum-guide.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper - Strategies to Secure Connected Cars with Firewalls
White-hat hackers have demonstrated gaining remote access to dashboard functions and transmissions of connected vehicles. That makes a firewall a vital component of a multilayered approach to vehicle security as well as overall vehicle safety and reliability. Learn strategies to secure with firewalls. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - What is Generative Design and Why Do You Need It?
Engineers are being asked to produce more sophisticated designs under a perfect storm of complexity, cost, and change management pressures. Generative design empowers automotive design teams to navigate this storm by employing automation, data re-use and synchronization, and framing design in the context of a full vehicle platform. Download Now
eBook - Simulation-Driven Design with SOLIDWORKS
Simulation-driven design can reduce the time and cost of product development. In this engineering.com eBook, we’ll explore how SOLIDWORKS users can access simulation-driven design through the SOLIDWORKS Simulation suite of analysis tools. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close