Questions About Specific Speed

Specific_speed

Specific Speed: Is defined as

nš = n × Q½

H¾

where: n is revolutions per minute, Q is capacity in gallons per minute, and H is head in feet.

The physical meaning of specific speed is: revolutions per minute to produce 1 gpm at 1-ft head with an impeller similar to the one under consideration but reduced in size.

The physical meaning of specific speed has no practical value and number is used as a 'type' number. The specfic speed as a type number is constant for all similar pumps and does not change with the speed for the same pump.

In the study of pump performance and classification of all important design constants, specific speed is a criterion of similarity for centrifugal pumps in the manner that Reynolds number is a criterion for pipe flow. When used as a type number, specific speed is calculated for the best efficiency point.

For further answer to your question, you may refer to 'Centrifugal and Axial Flow Pumps'- Theory, Design, and Application, By A.J. Stepanoff's book, Published by John Wiley & Sons, Inc.

sir, Thankyou for information , still iam in confusion i need for Hydro Turbines , type Francis turbine, Kaplan turbine, pelton wheel turbine, the question asked in the interiew please explane me in detail .

Guest:

When I used the following key words in Google:

turbine

specific

speed

I discovered http://en.wikipedia.org/wiki/Turbine (try it!)

I think there were several more links as well, but I did not check them out.

Google is an information source that tells you what is available on the internet about various subjects. It can be contacted by typing http://www.google.com into the address line on your internet browser page, and then pressing the "enter" button on your keyboard. You will then be presented with good links bearing directly on the subject keywords you used; sometimes millions of informative links!

I use it for all kinds of information on almost every subject. Google is called a "search engine", because it does the searching for you based upon the keywords you enter.

Another really great search engine that I often use is called Ask Jeeves. You can actually ask it your question, such as "What is meant by the term 'specific speed' when it is used for turbines?" Ask Jeeves is programmed to find an answer to your question if it can, by searching the internet.

The address for Ask Jeeves is http://www.ask.com.

It's a good idea to keep both addresses for these 'search engines' in your 'Bookmarks' or 'Favourites' tabs so you can find them easily whenever you need to use them.

There are really a lot of good search engines, and everybody has favourites they have chosen based upon their past experience with them. If you want to see how many, try using the keywords

search

engines

in Google, or ask the question "How many search engines are there?" in Ask Jeeves.

Good luck with your searches. This can seem like a complicated affair if you have not tried it before, but it is actually quite simple. If you're like me, you'll end up using 'search engines' all the time!

Mark