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 60 users online :: 6 registered, 0 hidden and 54 guests


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

Registered users: Bing [Bot], csitas, 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

Advantage of multiple ignition points?

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

Advantage of multiple ignition points?

Unread postAuthor: Mr. Sir » Sat Oct 30, 2010 4:05 am

After searching through old topics, it seems that there is no definitive answer regarding the possible performance increase of multiple spark gaps vs. one well placed gap. The reason I am wondering is because I am thinking of building a cannon with several (6?) evenly spaced ignition points down the length of the chamber (4"x18"). The cannon is also going to have an onboard propane/mapp meter, mixing fan, and stun gun circuit. Given the mixture is stoichiometric throughout the whole chamber, the excessive spark gaps will cause the flame to propagate at six different places, allowing for quicker combustion and more power. This is just my guess. Let me know what you guys think.

Also I am new to the forum. I lurked for the last week just reading through all this great information. I hope to learn much more and contribute to this awesome community. Thank you for your time.
  • 0


Mr. Sir
Private
Private
 
Posts: 2
Joined: Fri Oct 29, 2010 9:59 pm
Reputation: 0

Unread postAuthor: ilovefire » Sat Oct 30, 2010 4:41 am

welcome to spudfiles :)
yes you will get better performance with more spark gaps the quicker combustion will result in the projectile building up more speed in the given barrel length then a slower combustion would, will like to see how it works out for you and good luck
  • 0

User avatar
ilovefire
Colonel
Colonel
 
Posts: 511
Joined: Sat May 22, 2010 6:48 am
Reputation: 0

Unread postAuthor: POLAND_SPUD » Sat Oct 30, 2010 5:12 am

But does this mean that multiple spark gaps are not that important on small volume combustions?
  • 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: ilovefire » Sat Oct 30, 2010 5:24 am

POLAND_SPUD wrote:But does this mean that multiple spark gaps are not that important on small volume combustions?


on a small volume combustion you will also have a smaller barrel so to get it to reasonable speeds, the more spark gaps the better on whatever volume chamber
  • 0

User avatar
ilovefire
Colonel
Colonel
 
Posts: 511
Joined: Sat May 22, 2010 6:48 am
Reputation: 0

Unread postAuthor: spudamine » Sat Oct 30, 2010 11:16 am

After searching through old topics, it seems that there is no definitive answer regarding the possible performance increase of multiple spark gaps vs. one well placed gap.

Try downloading HGDT and having a play, It allows you to model multiple spark gaps.
http://thehalls-in-bfe.com/HGDT/
  • 0

Last edited by spudamine on Sat Oct 30, 2010 12:16 pm, edited 1 time in total.
User avatar
spudamine
Sergeant Major
Sergeant Major
 
Posts: 184
Joined: Sun Nov 23, 2008 2:47 pm
Reputation: 0

Unread postAuthor: Fnord » Sat Oct 30, 2010 12:08 pm

Jimmy did a study of this some time ago. It's about the most technical any of us have gotten.
Here:
http://www.spudfiles.com/forums/studies-with-a-closed-chamber-t12807.html
  • 0

Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: Mr. Sir » Sun Oct 31, 2010 12:07 am

Thanks for the info. I went ahead and built my chamber tonight. I threaded in five automotive spark plugs down the length of it. I know that the spark is way off center using plugs, but they look cool. It's not nearly the most efficient ignition setup but I want my cannon to be aesthetically pleasing. Hopefully the amount of sparks will make up for the fact that they are not centered.[/img]
  • 0


Mr. Sir
Private
Private
 
Posts: 2
Joined: Fri Oct 29, 2010 9:59 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Pete Zaria » Thu Nov 04, 2010 12:39 am

I believe the primary reason for multiple ignition points is to create multiple flame fronts inside the chamber during ignition, which theoretically deceases the time required to achieve peak pressure and helps to ensure complete combustion. However, I'd bet that the difference is only a few percentage points.

I used a long, thin piece of circuit board blank that runs the length of the chamber with small gaps etched (with a file) every few inches that create spark gaps.

Like a simplified version of this: http://www.burntlatke.com/strip.html

Ah, found some pics:
Image

Image

Peace,
Pete Zaria.
  • 0

User avatar
Pete Zaria
Moderator
Moderator
 
Posts: 978
Joined: Fri Mar 31, 2006 6:04 pm
Location: Near Seattle, WA
Reputation: 0

Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'