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 58 users online :: 4 registered, 0 hidden and 54 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Gasoline for combustion fuel?

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

Gasoline for combustion fuel?

Unread postAuthor: kjjohn » Thu Nov 26, 2009 1:38 am

How powerful would gasoline be if used as a combustion cannon fuel? Also, how would you vaporize it prior to injection into the chamber? Could it compare to the power of MAPP?
  • 0

User avatar
kjjohn
1st Lieutenant
1st Lieutenant
 
Posts: 270
Joined: Sat Jul 11, 2009 3:54 pm
Reputation: 0

Re: Gasoline for combustion fuel?

Unread postAuthor: jackssmirkingrevenge » Thu Nov 26, 2009 1:50 am

kjjohn wrote:How powerful would gasoline be if used as a combustion cannon fuel? Also, how would you vaporize it prior to injection into the chamber? Could it compare to the power of MAPP?


[youtube]http://www.youtube.com/watch?v=fkrsNiO_FJw[/youtube]

That should pretty much answer your questions ;)

To illustrate the power of petrol, have a looks about 3 minutes into this video, comparing a teaspon of petrol to a teaspoon of black powder:

[youtube]http://www.youtube.com/watch?v=DO7R7hneQDc[/youtube]
  • 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: starman » Thu Nov 26, 2009 2:20 am

It's been done a few times. Here's a link to RCMAN's gasoline cannons.

The key is finding a way to consistently carburet or vaporize the gasoline. However, for all the trouble you won't be getting any more energetic shots than you would if you were using the much easier, safer, cheaper and ready to use propane or MAPP.
  • 0

User avatar
starman
Donating Moderator
Donating Moderator
 
Posts: 3041
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC
Reputation: 0

Unread postAuthor: MrCrowley » Thu Nov 26, 2009 4:06 pm

With that blackpower/gasoline test, to be fair the powder wasn't even packed, it would pretty much be like flash powder going off.
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: rp181 » Thu Nov 26, 2009 4:31 pm

people have had success with spray bottles.
  • 0

User avatar
rp181
Brigadier General
Brigadier General
 
Posts: 1090
Joined: Thu Dec 13, 2007 8:47 pm
Reputation: 0

Unread postAuthor: CpTn_lAw » Thu Nov 26, 2009 5:12 pm

Conditions were not the same for gasoline fumes and BP. To deflagrate, black powder must be compressed, so, had it been a small packed container, that would have been fair. I don't know where i read it, but IIRC, 1 teaspoon of black powder stands for approx. 80 grains, 15 grains of powder give 270 cubic centimeters of gas when combusted, so 80 grains ==> 1440 cubic centimeters of gas.
If it's compressed, the pressure increase if much more fast, giving more acceleration; So, the comparison between gasoline and BP isn't accurate.

Still, BP has 3MJ/kg potential energy, where petrol has 46 MJ/kg....
  • 0

"J'mets mes pieds où j'veux, et c'est souvent dans la gueule."
User avatar
CpTn_lAw
Brigadier General
Brigadier General
 
Posts: 987
Joined: Sun Sep 11, 2005 9:10 am
Location: France
Reputation: 0

Unread postAuthor: jimmy101 » Sat Nov 28, 2009 5:30 pm

CpTn_lAw wrote:Still, BP has 3MJ/kg potential energy, where petrol has 46 MJ/kg....

Mostly because the BP has to provide it's own oxidizer. Petrol does not.

In a constant sized chamber, filled with the maximum amount of fuel, the BP will release a heck of a lot more energy than will petrol. The chamber can be completely filled with BP, but can only have a few percent of the chamber volume in petrol.
  • 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

Sponsored

Sponsor
 


Unread postAuthor: D_Hall » Sun Nov 29, 2009 1:37 pm

CpTn_lAw wrote:To deflagrate, black powder must be compressed,

Not the case. Black powder's burn rate is largely unaffected by ambient pressure (ie, confinement). That's what makes it so ideal for use in pyrotechnics (it will go like a bat out of hell even without confinement). For a counter point, nitrocellulose's burn rate is highly dependent upon ambient pressure. That's part of what makes it so safe for use in firearms (because a loose NC charge doesn't burn worth a damn it makes NC storage facilities much safer places than BP storage facilities).

At the office, we deal with all sorts of exotic explosives on a daily basis...and yet we still consider BP to be the most dangerous thing we handle largely due to it's unconfined ignition/burn characteristics.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1759
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: Willdebeers » Sun Nov 29, 2009 2:13 pm

CpTn_lAw wrote:Conditions were not the same for gasoline fumes and BP. To deflagrate, black powder must be compressed, so, had it been a small packed container, that would have been fair. I don't know where i read it, but IIRC, 1 teaspoon of black powder stands for approx. 80 grains, 15 grains of powder give 270 cubic centimeters of gas when combusted, so 80 grains ==> 1440 cubic centimeters of gas.
If it's compressed, the pressure increase if much more fast, giving more acceleration; So, the comparison between gasoline and BP isn't accurate.

Still, BP has 3MJ/kg potential energy, where petrol has 46 MJ/kg....


E=MC2 says that you can get a huge amount of energy from a small amount of mass. You have enough "potential energy" in your body to blow up half the world, if you could harness it. Perfect for birthday parties, or just making a really good point.
  • 0

Image
User avatar
Willdebeers
2nd Lieutenant
2nd Lieutenant
 
Posts: 214
Joined: Tue Feb 03, 2009 1:18 pm
Reputation: 0

Unread postAuthor: psycix » Sun Nov 29, 2009 2:40 pm

E=MC2 says that you can get a huge amount of energy from a small amount of mass.

Yeah only when going nuclear, where a small piece of the matter is transformed into energy. And when converting ALL the mass into energy you're talking antimatter...

Of course cptn_law is talking about chemical potential energy.
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: SpudBlaster15 » Sun Nov 29, 2009 3:57 pm

D_Hall wrote:Not the case. Black powder's burn rate is largely unaffected by ambient pressure (ie, confinement). That's what makes it so ideal for use in pyrotechnics (it will go like a bat out of hell even without confinement)


How exactly do you explain quickmatch then? Standard blackmatch made by soaking a cotton string in BP slurry will burn quite slowly, but if you add confinement (Thus pressurizing the reaction), the burn rate of the fuse increases by a factor of several tens.

Confinement significantly increases the burn rate of most pyrotechnic compositions. However, I suspect it has more to do with a pressure differential in the casing forcing the flame front through the composition at a greater rate than a simple rise in ambient pressure.

Also, LOL at the guy who used E=mc<sup>2</sup> in an attempt to explain chemical potential energy.
  • 0

User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Unread postAuthor: jrrdw » Sun Nov 29, 2009 5:26 pm

I see this thread going out of topic and not really getting back on topic. If PCGUY, any other moderator wants to open it back up so be it.
  • 0

When life gives you lemons...throw them back they suck!
User avatar
jrrdw
Donating Moderator
Donating Moderator
 
Posts: 6538
Joined: Wed Nov 16, 2005 5:11 pm
Location: Maryland
Country: United States (us)
Reputation: 25

Unread postAuthor: sgort87 » Sun Nov 29, 2009 7:09 pm

Ehhh, ain't hurtin nobody. I find it amusing.
  • 0

<a href="http://www.launchpotatoes.com"><img src="http://www.launchpotatoes.com/images/uploads/logo2.PNG"></a>
http://www.LaunchPotatoes.com
User avatar
sgort87
Donating Member
Donating Member
 
Posts: 1038
Joined: Sun Sep 18, 2005 10:32 am
Location: Lockport, Illinois
Country: United States (us)
Reputation: 1

Unread postAuthor: D_Hall » Sun Nov 29, 2009 8:19 pm

SpudBlaster15 wrote:How exactly do you explain quickmatch then? Standard blackmatch made by soaking a cotton string in BP slurry will burn quite slowly, but if you add confinement (Thus pressurizing the reaction), the burn rate of the fuse increases by a factor of several tens.


Right off the bat, I see nothing to indicate a bulk burn rate increase. What I see is nothing more than a surface burn increase due to redirection of flame on the exterior of the string. In other words, the post-combustion gas expansion rate is faster than the bulk material burn rate. If one redirects that gas expansion to a new chunk of propellant (ie, further along the string), then one sees a "burn rate" that is really nothing more than a device to measure the gas expansion rate.

This is NOT the same thing as burn rates going up due to honest to gawd confinement. The simple paper tube shown in your link hardly qualifies as "confinement." Hell, most spud guns aren't capable of demonstrating the effects of honest to gawd confinement (hint: Those who study these things generally use pressures measured in thousands of psi.)

Confinement significantly increases the burn rate of most pyrotechnic compositions. However, I suspect it has more to do with a pressure differential in the casing forcing the flame front through the composition at a greater rate than a simple rise in ambient pressure.

D'oh! There I go typing before I've fully digested everything you've said. You even appear to agree with me. You're seeing a surface flame propogation effect, NOT a bulk burn rate effect.

Since you're more or less with me at this point....

I don't know numbers off the top of my head but I'll say this:

Burn rate of propellants is typically quantified something like....

Rate = A * P^x

Where...
A = a constant.
P = absolute pressure.
x = what's known as the burn rate coefficient.

The burn rate coefficient is the dominant driver where propellant behavior characterization at high AND low pressures is concerned. For black powder, the burn rate is very nearly zero. In other words, BP at 0 psi burns at roughly the same rate as BP at 10,000 psi. Good rocket propellants have a coefficient on the order of 0.8. That means that yes, they burn one HELL of a lot faster at 10,000 psi than they do at 0 psi. Guns? Sorry, off the top of my head I don't know, but I wouldn't be surprised to see coefficients on the order of 1.5.

Note that I am NOT talking about flame propogation effects from one chunk of powder to another. I'm talking about bulk single-piece combustion properties.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1759
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: SpudBlaster15 » Mon Nov 30, 2009 2:49 am

D_Hall wrote:Note that I am NOT talking about flame propogation effects from one chunk of powder to another. I'm talking about bulk single-piece combustion properties.


That's what threw me off in the first place. I assumed you were suggesting that confinement has no effect on the burn rate of a loosely packed quantity of powdered/granulated pyrotechnic composition such as black powder. I think we can agree that simply increasing ambient pressure will have little effect on the burn rate of such materials, and that a single big chunk of pressed composition will be relatively unaffected by a casing of any strength.
  • 0

Last edited by SpudBlaster15 on Mon Nov 30, 2009 5:21 am, edited 1 time in total.
People should not be afraid of their governments. Governments should be afraid of their people.
User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Next

Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'