What compounds are involved in the combustion process in our engines (standard combustion, no nitrous or any additive). The chemical equations would be nice if anyone knows what they are. Even an educated guess would work.

here they are:

Perfect Combustion of gasoline is as follows:

Gasoline (hydrocarbons) + Oxygen —> Carbon Dioxide + H2O (water)

Typical/Incomplete Combustion:

Gasoline and Air (nitrogen and oxygen) —> Unburned Hydrocarbons + Nitrogen Oxides + Carbon Monoxide + Carbon Dioxide + H2O (water)

However, perfect combustion is not possible in internal combustion engines, due to many factors, including the fact that pure oxygen is not used in combustion; air from the atmosphere is used instead. Air contains a mixture of several different gas, the main two being oxygen (21% of air) and nitrogen (78% of air). Nitrogen and oxygen are both reactive when burned and as a result, nitrogen containing compounds are produced and emitted by internal combustion engines, so therefore the equation for typical combustion shows what actually occurs in an internal combustion engine. the incomplete part refers to the fact that all the hydrocarbons are not burned (refer the engine is running lean or not)

hope that helps

you should get some pretty in depth replys to this one but I will give it a shot.

IDEALY (meaning complete combustion with no nitrogen compounds produced) the equation is something like:

C8H16 (octane) + O2 = H20 + CO2

this is actually really far from what happens in reality though and Im not even sure that the chemical formula I gave for octane is correct.

there are actually lots of things that happen during combustion and if you want a full explination you can do an internet search (good Idea anyway) or just email me.

And don't overlook the radicals or trace elements in both gasoline and atmospheric air - Chlorine, zinc, sulfur, fluorine, bromine, iron, methane. propane, benzine, helium, argon, etc. These all change the chemical conversion process we call "combustion" and therefore the byproduct gasses.

This is another primary reason that oxygenated fuels are being mandated across the country, and another of the main reasons that ethanol is the agent of choice in this effort. Most of these chemicals can be found in all gasoline, and eliminating the use of 10% of gasoline through the substitution by ethanol would immediately eliminate 10% of these byproducts. Further elimination would be due to the oxygenation provided by the ethanol, chemically changing the byproduct gasses.

Ethanol (C2H5OH) is somewhat self-oxidizing in combustion, and changes the formula of byproduct gasses a bit. The molecular mass of ethyl alcohol is 46.06 amu, while the typical molecular mass of a gasoline molecule is closer to 100.0 amu, making it less apt to form regular cohesive droplets when vaporized. Gasoline is a Newtonian fluid which has properties which inhibit uniform vapor droplet formation. Additionally, this Newtonian nature of gasoline creates its wetting tendencies when gasoline contacts a porous metal surface. Alcohol molecules mixed with the gasoline tend to depress the adsorption of droplets by porous metal due to their larger molecular size.

The higher evaporation point as a result of the ethanol also helps prevent the gasoline from the fractional distillation that normally occurs when it is sprayed into a heated air space. This distillation separates the gasoline into its sub-component parts of heptane, isobutane, benzine, and iso octane (plus some traces of other components) before the combustion process begins, resulting in uneven flame kernel travel and random generation of various byproducts. The ethanol blended into the gasoline helps maintain larger and regular sized droplets which maintain integrity through the ignition phase and into the combustion process, so that the fuel is actually burned more slowly but completely as one charge rather than several divergent charges of various molecular blends. Through this process, the carbon and hydrogen atoms that are stripped from the molecules by the oxygen atoms are done in a more controlled manner, resulting in a more predictable array of byproducts.

But perhaps more important to us, while the addition of ethanol (with it's lower combustion temperature) will reduce the number of BTUs or joules of heat energy produced in the combustion process, the molarity of byproduct gasses is more regular and larger than the molarity of gasoline molecules in air alone. What this means is that even though less pressure is developed due to thermal expansion of gasses, the volume of gasses at STP with ethanol blended fuel is actually higher, creating more effective pressure in the closed space (cylinder).

For any who have studied chemistry for any length of time, this will probably make a little more sense, but you'll already understand that the greater part of the energy produced in a gasoline engine is from the creation of more liters of gasses from the HC/O² combustion than from heat. Some of the energy is due to thermal expansion of these gasses (Boyle), but not the majority of the energy. Ethyl alcohol blends will burn cooler, sacrificing some of the thermal energy, but create more liters of byproduct gasses in terms of molarity and volume at STP. So the slightly slower and cooler burning ethanol blends can actually make more effective cylinder pressure if the blends are controlled well.

This is the primary reason that aircraft have used water-alcohol blends as a power-boosting agent, producing up to 40% more power than on gasoline alone. This practice has been in effect since WWII, and continues on higher altitude piston aircraft engines today. Most general aviation aircraft do not use this method, but then most general aviation aircraft are not equipped to reach altitudes over 11,000 ft.

that vader is one smart *****..........

Vader,

Is this all you do, or do you do some neurosurgery on the side, or maybe some rocket scientology just for fun? No really, are you a technician or an engineer or something?

84,

Did we at least get you pointed in the right direction?

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Hey!? They don't just give these Intergalactic Overlord jobs to chimps, you know....

When you're as old as a sequoia, you pick up a few things. The trick is trying to remember them all.