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 67 users online :: 4 registered, 0 hidden and 63 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Twitches Science Project V.2. "SNCA"

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
Sponsored 
  • Author
    Message

Unread postAuthor: noname » Thu Jul 26, 2007 10:52 am

God damn! All of you saying he didn't break the sound barrier: he knows already, and he acknowledged it himself! Read his frickin' posts!

I believe the gases could easily break the sound barrier; even in my soda can mortar, if I can gets stuck, then it makes a huge (sonic) boom, because the gas is forced out of a tiny crack and flow rate is accelerated.
  • 0

User avatar
noname
Lieutenant General
Lieutenant General
 
Posts: 2699
Joined: Mon Apr 10, 2006 9:19 pm
Location: Bay Area, CA
Country: United States (us)
Reputation: 9

Unread postAuthor: jimmy101 » Thu Jul 26, 2007 2:16 pm

jackssmirkingrevenge wrote:30-40 psi is 15-25 psi more than the atmosphere, with that sort of impetus given the right conditions there's no reason why gasses shouldn't accelerate past the speed of sound.

I doubt this is true.

As the speed of the gases goes up the drag with the pipe goes up as well. Pretty soon you'll reach the point where the drag completely offsets the force due to the pressure gradient.

My cheapo shop compressor puts out 120 PSIG (135 PSIA), using a blow gun the air sure as heck isn't going supersonic.

Of course, if "given the right conditions" means you put the gas in a cylinder than carry it supersonically in an F-22, well then yes, "given the right conditions" you can get it going supersonic.

But it'll never happen with just air flowing through a pipe at tens of PSI.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: jimmy101 » Thu Jul 26, 2007 2:29 pm

noname wrote:God damn! All of you saying he didn't break the sound barrier: he knows already, and he acknowledged it himself! Read his frickin' posts!
Yes, but then he fell back to basically "the gases" were supersonic (something was supersonic because of "the sound" it made). Fact is nothing was supersonic, not the ball, not the gases not the sound. It was just a big ass bang.

noname wrote:I believe the gases could easily break the sound barrier; even in my soda can mortar, if I can gets stuck, then it makes a huge (sonic) boom, because the gas is forced out of a tiny crack and flow rate is accelerated.


I really doubt the gases break the sound barrier. Not enough mass for gas to have significant momentum (or kinetic energy) and any piddly little drag force will quickly decelerate gases moving near 1100 FPS. Even venting out a crack in your mortar the gases will not be going supersonic, too much drag, not enough momentum. (The venturi affect quits working long before the gases reach the speed of sound for the conditions in the nozzle.)

A big ass bang is not the same as a sonic boom. A .45 caliber pistol makes a big ass bang but does not fire a supersonic round.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: wannabie » Thu Jul 26, 2007 5:03 pm

jackssmirkingrevenge wrote:DDT? Isn't that a pesticide :?


yeah i think it is....:(

I ment that thing that happens to hybrids...were you loose your face...and it goes boom....and yeah that stuff...

or cant that happen in normal combustions.... im really confused...
  • 0

User avatar
wannabie
Captain
Captain
 
Posts: 304
Joined: Sun Apr 15, 2007 11:44 pm
Location: Australia
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jul 27, 2007 5:27 am

Of course, if "given the right conditions" means you put the gas in a cylinder than carry it supersonically in an F-22, well then yes, "given the right conditions" you can get it going supersonic.


That's exactly what I meant :)

Couldn't the friction caused by the increasing drag heat up the gas and raise the pressure, in a long enough barrel?

I'm talking out of my arse here, all I'm seeing at the moment is my bed and all knowledge of thermodynamics has disappeared down the toilet along with my breakfast :?
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Modderxtrordanare » Fri Jul 27, 2007 10:29 am

wannabie wrote:
jackssmirkingrevenge wrote:DDT? Isn't that a pesticide :?


yeah i think it is....:(

I ment that thing that happens to hybrids...were you loose your face...and it goes boom....and yeah that stuff...

or cant that happen in normal combustions.... im really confused...


DDT stands for Deflagration to Detonation Transition.
You also described it pretty well, with the whole losing your face bit. It only seems to happen in hybrids, and as a saftey margin, any hybrid at a 4x mix or above is prone to having DDT occur inside of the ignition chamber, and therefore are remotly fired. (When hiding behind a brick wall :lol: )


(Or Dichlorodipentyltrichloroethane [the pesticide])
  • 0

Spudding since '05. Proud waster of plumbing and plumbing accessories.

-Wiki
-How-To: Modding a Sprinkler Valve
User avatar
Modderxtrordanare
Donating Member
Donating Member
 
Posts: 686
Joined: Mon Nov 20, 2006 1:22 pm
Location: Texas
Reputation: 0

Previous

Return to Combustion Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot]

Reputation System ©'