Questions and Answers

Ideas For Alternative Fuels Q. Mr. Ciulla, My name is Adam. I am not very knowledgeable about cars. However, I recently read some interesting articles about common household products with combustive properties when extracted into fine dust. I am interested in seeing if a car engine could be built that accepts some of these products instead of gasoline.

Fuel injection turns the gas into a fine vapor so I assume it can do it for other products as well. Would you happen to know anyone I could talk to about some of my ideas? This is purely on the hypothetical stage as of now.

Flour can be very explosive when in a dust form. Apparently corn towers can explode if there is a spark present. Why can't an engine be built that uses a fuel injector to spray the flour into dust and use the combustion from a spark plug to power a piston?

Also, pure oxygen is explosive as well. And, as I also read, the problem with hydrogen fuel cells is the problem of efficiency in obtaining hydrogen atoms from H₂0. What if a car was built with a hydrogen fuel cell and an internal combustion engine that uses pure oxygen as a fuel source? It would double the efficiency in creating fuel for hydrogen cars as both the Hydrogen and oxygen would be used as a fuel source?

If a hybrid car can have an electric motor and a 4 cylinder engine, why can't it have two modified motors? Or why can't cars run on pure oxygen anyways for that matter? It seems to me that a combustible engine can run on anything that explodes, and we just happen to pick a fuel that has a limited supply and is controlled by other countries.

Thanks,
Adam

A. First thing I want to do is clear up a very common misconception, oxygen is not flammable. Oxygen takes part in combustion and in corrosion but does not itself burn. Think about it, if oxygen itself burns the first spark ever created would have fried the whole planet. So that answers a great deal of your question.

The second misconception is that fuel in the cylinder explodes. It does not explode, it is burned. An explosion is uncontrollable while the burn can be controlled and managed.

While it is true that an internal combustion engine can burn many other compounds, gasoline is the BEST compound for combustion. Gasoline became the preferred automobile fuel because it releases a great deal of energy when burned, it mixed readily with air in a carburetor, and it initially was cheap due to a large supply. Costs have now increased greatly except where subsidized.

It also has something that just about no other fuel has; octane. Octane is any of several isomeric liquid alkanes C₈H₁₈. A gasoline's octane number indicates its ability to resist knocking, premature combustion, and can be altered by changing the proportions of certain components.

Hydrogen is being researched and tested as an alternate fuel source. The only emission of hydrogen combustion is water, which can be broken down into oxygen and hydrogen and burnt again. The biggest drawback to using hydrogen as a fuel is it's storage. Hydrogen just can't be compressed into a tank like oxygen. It needs a stone like base inside the tank to store it, much like acetylene.

This makes the storage tanks very heavy and to carry enough hydrogen to get a decent vehicle range would make the vehicle impossibly heavy, not to mention the room the storage tanks require. Refueling stations is another problem that needs to be worked out.

Many states now require that ethanol be added to gasoline to extend existing fuel supplies. A 10% blend of gasoline and ethanol can be used by any engine, except diesels of course, without having to modify the engine or do the engine any damage. With modifications an 85% blend of ethanol can be used. Read Ethanol As A Fuel for more information on this.

So while an engine can burn many things, and until something better is developed, gasoline is the only compound that gives the most bang for the buck.

I sent this to my friend John who is a Chemist. This is what he sent back.

Hi Vince;

I suppose it might be possible to construct an engine that would run on a combustible solid such as Adam envisions. One problem would be fuel handling. Liquids are easy to pump and move around. Solids are more difficult.

What he is really asking about is an alternative fuel. As you know, there are lots of ideas to use alcohols and bio sourced oils, such as soy bean oil, as fuels. What one has to look at is energy density. How much energy is available from a pound or gallon of a material when it is completely burned.

This is basic chemistry and it is possible to write the equations to convert an organic molecule completely into carbon dioxide and water. One can then calculate the energy available in many cases. In some cases, the basic data to do the calculation may not be easily available but one could come up with estimates other ways.

With respect to oxygen, there is a basic misunderstanding of combustion on Adam's part. Oxygen is not a fuel. It reacts with other materials that are fuels to provide energy. Oxygen is only explosive when it comes into contact with some other material that is a fuel.

For this reason, for example, one has to be certain that oxygen gas cylinder regulators are degreased. If they have any oil internally, from cutting fluids or other lubricants, one can get an explosion in the regulator. Pure oxygen is very reactive.

Fuel cells are simply a different form of "combustion". The reaction in the fuel cell is essentially the same as the reaction in an internal combustion engine. Only the fuels are different. And in the fuel cell the rate of the reaction is slower so it is not what we call an explosion. In both engines a fuel reacts with oxygen.

In a fuel cell, since the fuel is hydrogen, only water is formed. In an internal combustion engine, carbon dioxide and water are formed. (In theoretically ideal combustion - as you know, in the real world, combustion is much more complex and we form nitrogen oxides from the nitrogen in the air and fuel, sulfur oxides from the sulfur in the fuel, and carbon monoxide from incomplete combustion.)

Hope this helps a little bit.

Best Regards,
John