Given 1 cubic inch of atmosphere and gasoline at the ideal mixuture, how much will it expand when burned? Or to put it another way, how many cubic inches would 1 cid expand to when burned, to achieve an equilibrium with the atmospheric pressure or 0 psi at sea level? If needed, assume a compression ratio of 10.00:1.
After the initial burn, what would the pressure be, before any expansion of the combustion chamber is allowed? If it's different, what is max combustion chamber pressure?
Say you have your 14.6/1 ratio fuel mixture in a cylinder, basically a b0m-b, but one that is strong enough to contain the energy from the perfect fuel mixture, at atmospheric pressure. Ignite it, the fuel uses up the oxygen and converts to heat, increases the pressure and everything eventually cools back down to ambient temp. I'm thinking there'll be a slight vacuum because the volume/mass of fuel and oxygen that was expended and has been taken out of the cylinder.
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If the mixture in the chamber is not compressed before ignition, then yes. However, if you compress the mixture first, you're putting energy into it and the temp will be higher than ambient. Ignite it and the temp is MUCH higher than ambient so it should occupy a much larger than original volume.
So if you took 10 ci and compressed it to 1 ci, ignite it and the temp goes to 1000 degrees F (pulling numbers from my sphinxter) and say ambient was 100 degrees F. Allowing the volume of the cylinder to change to allow the gas to expand as far as it could, what would the max volume of the cylinder be? I guess there would be some residual higer temperature when the cylinder is at max volume, because if the gas cooled completely back to 100 degrees, the volume should be the original 10 ci. But at max volume it seems the pressure internal to the cylinder should be back to atmospheric, just at a higher temp than ambient.
On edit, Furball, I reread your post and no, I don't think there would be a residual vacuum in your example. If your container does not change shape then upon ignition, the temperature and pressure rise, then as the temperature bleeds off, the pressure will drop until temp = ambient. Then the pressure inside the container should be the same as it was before ignition. Because nothing left the container. The chemical composition changed but all the atoms that were in there to begin with are still there. Unless H20 and CO2 occupy less space than HC and O2 (I'm simplifying here in the last sentence).
Last edited by 76supercab2; 11-28-2006 at 05:25 PM.
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