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| khepera1997 |
 Posted: 02/17/2010 21:56 PM Post subject: Stoichiometric's (A.K.A. Fuel/Air Ratio) |
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Private
Joined: 17 Feb 2010
Posts: 2
11.44 Spud Bux
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I am in the Process of Building a Spud Gun and iv Got Every Thing Down But The Stoichiometric's. (A.K.A. Fuel/Air Ratio)
Number One:I Can Calculate the Stoichiometric's But When i Do i Have the Answers in Volume i Need Some Thing in P.S.I. i Mean How do i use Volume as an Answers Ane way.
Number Tow:What Do People Mean by 1x 2x 3x ext. |
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| McCoytheGreater |
| Posted: 02/17/2010 22:50 PM Post subject: |
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Sergeant Major
Joined: 15 Dec 2009
Posts: 193
32.17 Spud Bux
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Check out the spudwiki.
Burnt Latke has helpful calculators.
The Hybrid Cannon Discussion board has all the answers on 1x 2x and 3x. |
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| Insomniac |
| Posted: 02/17/2010 22:56 PM Post subject: |
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Major General
Joined: 18 Dec 2006
Posts: 1265
1623.41 Spud Bux
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Well, firstly you need to work out the volume of the meter pipe is, and then you need to figure out what pressure you will need in that volume to give the correct voume of gas at atmospheric pressure. I've never done this so I don't know the math off the top of my head, but I doubt it's too tricky. It'll probably be easy to find in either the Wiki or the Burnt Latke site.
By 1x, 2x, 3x people are reffering to the 'mix' used in hybrid guns. Hybrid guns pre-pressurize their fuel/air mixture prior to firing to increase the total energy that can be obtained from a given chamber size. The number simply refers to the pre-ignition pressure in BAR. So a 1x mix is 1 times atmospheric pressure (about 14.7 psi), and this is the pressure at which a regular combustion operates (it would show 0psi on a normal pressure guage as these usually measure the difference between normal atmospheric pressure and what they're connected to, and as normal atmospheric pressure is 14.7psi then there is no difference).
A 2x mix has a pre-ignition pressure of 2 BAR etc. Some hybrids go all the way up into and beyond the 200x, or 200 BAR range. |
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| MrCrowley |
| Posted: 02/18/2010 2:41 AM Post subject: |
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Kaleun
Joined: 23 Jun 2006
Posts: 8999
9195.37 Spud Bux
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To be honest, I would recommend you do more research if you don't understand what is meant by 1x, 2x and 3x, let alone how to calculate the required fuel pressure. Good thing about hybrids is that they don't work unless you know what you're doing, the bad thing is that if someone tells you how they work and you are unaware of the dangers involved you could cause some serious damage/harm.
Apart from that, check the hybrid discussion sections, the Spudwiki and even the showcase sections. |
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| rcman50166 |
| Posted: 02/18/2010 7:40 AM Post subject: |
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The ME Student Spudder
Joined: 19 Jan 2008
Posts: 694
625.25 Spud Bux
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| Well as long as this thread is here. Could anyone tell me the stoichiometric ratio for iso-octane? It's chemical composition is C8H18. Would that make the ratio 11.5 to one? |
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| jimmy101 |
| Posted: 02/18/2010 14:16 PM Post subject: |
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Lieutenant General
Joined: 28 Mar 2007
Posts: 2866
11974.95 Spud Bux
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| rcman50166 wrote: | | Well as long as this thread is here. Could anyone tell me the stoichiometric ratio for iso-octane? It's chemical composition is C8H18. Would that make the ratio 11.5 to one? |
2 C8H18 + 25 O2 = 16 CO2 + 18 H2O
So for each 25 volumes of O2 you need 2 volumes of C8H18.
Air is about 20% O2 so you need (0.2)(2/25) = 0.016, which is 1.6% by volume. That's additive. I believe for displacive it would be 1.57% |
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| rcman50166 |
| Posted: 02/18/2010 14:55 PM Post subject: |
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The ME Student Spudder
Joined: 19 Jan 2008
Posts: 694
625.25 Spud Bux
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| So on an O2 sensor, I would be looking for a number ideally around 12.5? I just want to be sure. I'm going to be fine tuning an engine and need that number. |
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