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| Necrosis |
 Posted: 03/22/2008 20:19 PM Post subject: Gasoline stochiometric mixture. |
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2nd Lieutenant
Joined: 03 Jul 2007
Posts: 201
107.30 Spud Bux
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What is the perfect mix of air and gasoline in percentage of gasoline for the given volume?
I found that a ratio of 14:1 was best or something.. but this does not ring a bell.
14 parts of air for 1 part of gasoline?
I don't know..
I'm probably going to build a hybrid sometime this week, wish me luck. 
And thanks in advanced! |
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| LikimysCrotchus5 |
| Posted: 03/22/2008 20:25 PM Post subject: |
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Brigadier General
Joined: 04 Sep 2007
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Lets see if i can be jimmy. (I know stoichiometry too, let me just find the formula for gasoline or whatever you call it.)
Well i found out that its common chemical formula is C8H18. So my stoichiometry will be based on that.
combustion is: 2C8H18 + 25O2 = 16CO2 + 18H2O.
So gasoline to oxygen ratio is 2:25 or .08.
Now since 20.95% of the earth's atmosphere is oxygen, you need to multiply that by gasoline/oxygen ratio, .2095*.08 = .01676 or 1.676%
So that percentage should be the amount of gasoline in the chamber, correct me if im wrong jimmy.
EDIT: But yea gasoline is a bunch of hydrocarbons, what i found out from 5 min of research, so this ratio may not be right because your gas may not be C8H18.
Last edited by LikimysCrotchus5 on 03/22/2008 20:48 PM; edited 2 times in total |
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| DYI |
| Posted: 03/22/2008 20:28 PM Post subject: |
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Rear Brigadier
Joined: 07 Jul 2007
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| Gasoline is composed of a LOT of different hydrocarbons. Doing stoichiometry for it is a whole different beast compared to things like air/propane. Considering how widely used gasoline combustion is, you should be able to find numbers somewhere. |
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| markfh11q |
| Posted: 03/22/2008 20:56 PM Post subject: |
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Donating Member
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| The stoichiometric ratio commonly quoted is 14.7% gasoline to air (mass). At least, that's the base mixture used for engines before optimization. |
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| jimmy101 |
| Posted: 03/23/2008 12:17 PM Post subject: |
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Major General
Joined: 28 Mar 2007
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LikimysCrotchus5 hit it dead on. The stoichimotric ratio for gasoline in air is about ~1.7 mole percent. If the gasoline is vaporized then the mole percent is the same as the volume percent. I suspect that if you convert markfh11q 14.7 wht. percent into mole percent you'll get ~1.7.
Gasoline is a mixture of a bunch of stuff but the vast majority has the same, or nearly the same, chemical formula (but not chemical structure) as octane. You can go through the calc's with hexane, heptane, octane, iso-octane, nanane (sp?) and you'll find they are all very similar so it really doesn't matter too much. Other things introduce much larger errors than the uncertainty in the exact chemical composition.
The tricky part is measuring the correct amount of a liquid fuel since the volume of the liquid is so much less than the volume of the gas. According to my "liquid fuels" page a 100in3 chamber takes 0.184mL of gasoline for a stoichiometric mix with air. (Notice how I mix english and metric units to keep folks on their toes  ) That is something in the vicinity of 2 drops liquid gasoline for the 100ci chamber.
Since it is very difficult to measure 2 drops with any kind of accuracy, especially since the high vapor pressure of the gas makes it piddle out of an eyedropper, the exact stoichiometry is the least of your worries. |
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| LikimysCrotchus5 |
| Posted: 03/23/2008 12:23 PM Post subject: |
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Brigadier General
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| jimmy101 wrote: | | LikimysCrotchus5 hit it dead on |
thank you, so i know i was right.
I guess chem class really was useful. I though i might give you a break ne way, you do way to many calculations a day  . |
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| Necrosis |
| Posted: 03/23/2008 15:13 PM Post subject: |
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2nd Lieutenant
Joined: 03 Jul 2007
Posts: 201
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My mom uses really tiny syringes for her reuma, I figured i'd use those.. but.. that's a really tiny amount.
I might just use a buthane lighter and stuff now, thanks a lot! |
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