RappyPilot

Was reading an article on methanol …

Came across this sentence “A glow plug being able to ignite the methanol vapor through a catalytic reaction”

What catalytic reaction?

Isn’t a catalytic reaction just where rate of a chemical reaction is either increased or decreased by means of a catalyst typically being a chemical substance?

Is it just a case of the piston compressing the air/fuel mixture (Thus increasing temperature of the combustion chamber including the glow plug filament) to a point where this increase in temperature reaches a critical state for the methanol thus igniting the fuel/air mixture?

ggraham500

My Feedback: (4)

A catalytic reaction is a chemical reaction where a catalyst is used typically to speed up a reaction between two or more chemicals. A catalyst is not consumed by the reaction itself. An interesting chemical phenomena is the ability of platinum to glow in the presence of methanol. Platinum is the coiled metal in your glow plug.

The oxygen content of nitromethane ("nitro") enables it to burn with much less atmospheric oxygen in comparison to hydrocarbons such as gasoline. Even moderate amounts of nitro tend to increase the power created by the engine (as the limiting factor is often the air intake), making the engine easier to tune or adjust for the proper air/fuel ratio.

That help?

Gary Graham
(I teach chemistry and physics)

jbdismukes

My Feedback: (2)

Hey, Teach, thanks for clearing that up. Even an old codger like me can understand it now.

Class of '57

RappyPilot

Ok, so the platinum helps the glowplug wire glow as opposed to just the heat generated by combustion.

Cool. Thanks for that. It all makes sence now

downunder

I might add that the catalytic reaction only begins when the mixture has been compressed to a certain level. Effectively this packs more methanol molecules against the platinum. This combination of compression and coil temperature is what initiates the catalytic reaction and therefore the ignition point. Increase/decrease either the compression or coil heat and you advance/retard the ignition.

gkamysz

My Feedback: (19)

http://www2.uni-siegen.de/~pci/versu.../methanol.html

Compression is not necessary, but it is part of the equation in our engines.

RappyPilot

Now that is awsome Very interesting indeed.

Jezmo

I agree with RappyPilot and I am not trying to be argumentative here Gary but you can drop platinum into a container of methanol and it won't glow at all. The initial glow (heat) comes from the electrical current of the glow driver. (Catalytic converters on cars also contain platinum and enhance the reaction between the unburned hydrocarbons and oxygen. They must also reach a certain temperature before the reaction takes place just like our little glow plugs.) The reaction between the methanol and the oxygen in the air (also to include the oxy being released by the nitromethane) is what creates the heat that keeps the platinum coil hot after we remove the glow driver. As RappyPilot stated and as I understand it a catalytic agent (in our case platinum in the plug) simply enhances (speeds up) the chemical reaction between two or more elements (in our case methanol, a hydrocarbon, and the oxygen in the air) and allows that reaction to occur more efficiently, sometimes by very great amounts. Again, as I understand it, the glow of the platinum in the coil is from the heat of the reaction going on around it; the platinum is just facilitating that reaction.

If I am off in my understanding I welcome the input of those chemical engineers and others educated in such matters. A day that I don't learn something new is a day that I have wasted.

ggraham500

My Feedback: (4)

You are not being argumentative. A lively discussion is always interesting.

After initially using a glow driver (or other heat source) to heat up the platinum to glow temp, the glow reaction will sustain in the presence of methanol (or ethanol). The methanol becomes "fuel" when it is mixed with oxygen. The nitro essentially adds more oxygen to the reaction because the oxygen content of nitro enables it to burn with much less atmospheric oxygen in comparison to hydrocarbons such as gasoline. I agree that the platinum is acting as the catalyst although the platinum is finally consumed probably due to a physical breakdown rather than a chemical reaction.

Here again are great photos per link above from gkamysz.
http://www2.uni-siegen.de/~pci/versu.../methanol.html

dakotanut

That was awesome. I now understand it a lot better. Thanks a lot. Now I know why and how it works in our little motors. Excellent thread.