Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 63 users online :: 6 registered, 0 hidden and 57 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Compression ratio

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
Sponsored 
  • Author
    Message

Compression ratio

Unread postAuthor: sputnick » Mon Dec 29, 2008 2:02 pm

There is a question that I have been wondering for a while, and that is, What is the compression ratio of air at 100 psi VS air at just normal atmospheric pressure? as in, one liter of 100 psi is the equivalent of how many liters of uncompressed air?

This is all I need to know to measure how much wasted air is being blown out the barrel of my many inefficient airguns, and any help would be appreciated :P
  • 0

User avatar
sputnick
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 498
Joined: Sun Dec 14, 2008 3:53 pm
Location: Ontario Canada
Reputation: 0

Unread postAuthor: skyjive » Mon Dec 29, 2008 2:10 pm

If you compress a given amount of air to double the pressure, it will occupy half the volume. Atmospheric pressure is 14.7 psi, so 1 liter of air at 100 psi is equal to 100/14.7=6.8 liters at atmospheric pressure.
  • 0

User avatar
skyjive
Master Sergeant
Master Sergeant
 
Posts: 163
Joined: Mon May 26, 2008 3:52 pm
Reputation: 0

Unread postAuthor: sputnick » Mon Dec 29, 2008 2:13 pm

So you mean to say, that 6.8 litres of just regular pressure air compressed to 100 psi would be 1 liter? are you sure of this?
  • 0

User avatar
sputnick
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 498
Joined: Sun Dec 14, 2008 3:53 pm
Location: Ontario Canada
Reputation: 0

Unread postAuthor: Hotwired » Mon Dec 29, 2008 2:15 pm

A standard atmosphere (atm) is 14.696psi.

100/atm = 6.805

So thats 6.805 litres of air in a 1 litre chamber if pressurised to 100psi.


If you want to be unreasonably accurate then find out your local atmospheric pressure and recalculate.


Blarg. Beaten to the post.
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2599
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: sputnick » Mon Dec 29, 2008 2:17 pm

Thanks for the reassurance, so then a ratio of 7 to 1 is all I really need, since none of my devices are that precise
  • 0

User avatar
sputnick
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 498
Joined: Sun Dec 14, 2008 3:53 pm
Location: Ontario Canada
Reputation: 0

Unread postAuthor: POLAND_SPUD » Mon Dec 29, 2008 2:38 pm

I know it's kind of offtopic but it good to be able to use different units.. both imperial and metric... answering this quesiton is very easy if you can switch to atm instead of PSI...

1L of air at 2 atm equals 2L of air at 1 atm

seems simple doesn't it ?

the same thing aplies to measuring lenght and weight
US, UK and commonwealth countries use imperial units not becasue they are better but becasue of tradition... personally I preffer to use PSI though - somehow it's easier for me to imagine how much is 700 psi than 50 bar/atm...
  • 0

Children are the future

unless we stop them now
User avatar
POLAND_SPUD
Chief of Staff
Chief of Staff
 
Posts: 5405
Joined: Sat Oct 13, 2007 4:43 pm
Country: Israel (il)
Reputation: 10

Unread postAuthor: btrettel » Mon Dec 29, 2008 2:43 pm

The ratios people have posted are accurate for constant temperature, which may or may not be a reasonable assumption (GGDT will show if it is). If the air temperature changes things'll get a little more complicated. You should look at air mass, not volume, if you want to know how much you are wasting. The ideal gas law will give you a good idea of how much air mass you are using if you know the temperatures. I don't use the version of the number of moles. Scroll down a bit to see the version with the total mass of the gas and use that.
  • 0


btrettel
Major
Major
 
Posts: 380
Joined: Sun Feb 03, 2008 4:40 pm
Location: Maryland
Reputation: 0

Sponsored

Sponsor
 


Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'