Fuel combustion by heating

[Ciro Pabón]

Does anybody knows if you can start combustion of fuel inside the combustion chamber by heating it instead of using a spark? If this is possible, what temperature do you have to reach? Have this been tried before in a four-stroke engine?

Finally, I'd appreciate any links on the stochiometry of combustion and the explanations at the microscopic level on what is the chemical mechanism behind fuel combustion, specially about how it starts and how it propagates.

[joseff]

Do glow plugs count? I have it in my R/C car running on methanol.

[DaveKillens]

Compression ignition? aka diesel.

[Carlos]

Ciro I have noted your interest in combustion and megaphone design. I would recommend Scientific Design of Exhaust and Intake Systems by Philip Smith I believe you were looking for a programme concerning a megaphone design programme, if memory serves, this book has some simple "paper and pencil" solutions to megaphone design. Bentley Publishing once released a book that contained a picture of a Harry Westlake (?) designed combustion chamber constructed of clear (perspex?)
plastic under operation. Also the late Gordon Jennings wrote some very good articles for Cycle World in the 1970's on these subjects. One concrete observation, my brother , while port and polishing intake tracts on 4 strokes made sure to never polish to a shine because the fuel mixture would start to devolve into larger droplets which lowered HP output. A pleasure to meet you Ciro ,,, and of course everyone else,to be sure.

[Carlos]

Ciro, Flame Imagining Studies of Combustion Completion in a SI Four Stroke Engine By Stephen C Bates at http://www.tvu.com/PCombCompleteweb.htm

[Carlos]

http://www.erc.wisc.edu/modeling/multi_ ... lgrade.pdf

[Ciro Pabón]

Carlos:

Thanks a lot for the links, "mano". I am reading them today. It is not a megaphone: is something more on the "stratosphere".

Actually, I am doing some research on a couple of ideas about how to improve the (already developed) idea of using a laser to ignite the fuel, but I am working on them. I'll keep you informed of my advances, if you wish, as I am still looking for "partners" in development... but I am not sure about the feasibility, yet. This is the reason that Dave's and joseff's suggestions (good as always) are of no use (for me).

I used to build R/C aircrafts, too, joseff... You would laugh if you could see what I am doing with my old .50 engine... it is my "testbed" for the idea right now. It hasn't worked yet (and I am afraid I have succedeed in ruining it and burning my workbench a couple of times since yesterday morning, when I had "the bright moment"). I can burn the mixture with a borrowed friend's homemade laser, but I have not been able to make it detonate. The engine is completely covered in soot... all we have developed a nice "gas burner" but the damn thing won't explode. Besides, the quartz windows we had made keep cracking with the thermal expansion and they get soot everywhere, too.

Perhaps somebody has some experience on laser "spark plugs"? And maybe somebody knows why are not used in F1 (allegedly, they allow you to use a leaner mix)? Or in any car I know, by the way? I know only the Yag (Ytrium-argon) and solid state versions. I am working with a very fragile (and less than potent) green mercury-vapor laser with a 60's design... I have to get a solution soon or my wife will kill me (if I don't kill myself first).

[Saribro]

And maybe somebody knows why are not used in F1 (allegedly, they allow you to use a leaner mix)?

5.8.1 Ignition is only permitted by means of a single ignition coil and single spark plug per cylinder. The use of plasma, laser or other high frequency ignition techniques is forbidden.

So, no dice on the lasers.

[Carlos]

Ciro--- The first article seems to suggest that the flame propogation
front is least efficent bordering the cylinder walls of an engine--- a basic
problem of a single source of ignition--- using a number of lazer diodes in
an array around the outside diameter of the cylinderhead may solve this.
Perhaps locate the diodes remote from the engine and just use silica
filiment optics and lens inside the cylinder head---but then I only had this thought as I read your post---one could strive for fuel efficency or power---I think I once read that there is a limit to fuel to air mixture that
will ignite---23/1? Very good speaking with you. Thank you for your welcome.

[Carlos]

I have oversimplified factors affecting 4 stroke combustion, there are many variables---engine timing, intake tract volume and velocity , cam
slope and lift, combustion chamber shape, intake and exhaust plumbing,
including ignition efficency , swirl and vortex gereration , and another 20 or more factors, and of course, the lean limit of air/fuel ratio is well beyond
23/1---but their is a limit. Ciro ---do those little pictures in the first article look like radar maps of weather coming in from the East? A multiple array of laser diodes projecting beams att different angles could solve the problems of localized charge stagnation---why lasers could not only be located in the head but on the cylinder walls--- diode pumped solid state lasers do suffer some problems of durablity and power. These will be overcome. Already diode lasers are used for mico-machining. They are becoming less expense---with their computer control modules you have options of multiple "firing", modulation of output---a dozen different variables. Ciro--- we have both read Nicco's The Prince many times--- it is a patent that pays. At one time you could have patented the sandwich---the man that patented the spray nozzle on a spray paint can is wealthy beyond imagination--- currently the large game console makers are in court with someone who patented the idea of sensors in a hand-game controller, did they ever produce a functional unit?---Please excuse me if have followed a different path, as Robert Frost would say---I am not sure of the form of the thread path I have strayed. The basis of combustion is of course organic chemistry perhaps "carbon chemistry" is a better term.
Thank you all for your indulge in my flights of fantasy

[joseff]

Hardcore! We have Ciro's long-lost twin brother on the forum!

Welcome, Carlos.

[Ciro Pabón]

It takes one to recognize one, joseff, my bro.

Actually, Carlos's ideas are right on the money. For example:

Laser Focus World: Yag laser multiplexing by fiber optics to guide light to each cilynder

National Energy Technology Laboratory: Leaner mix on NGV engine with lasers

Weekend Pundit: Solid state lasers for ignition

[Carlos]

Joseff---Thank you for the kind welcome. Ciro---Thank you for the links.

[ACRO]

Does anybody knows if you can start combustion of fuel inside the combustion chamber by heating it instead of using a spark? If this is possible, what temperature do you have to reach? Have this been tried before in a four-stroke engine?

Finally, I'd appreciate any links on the stochiometry of combustion and the explanations at the microscopic level on what is the chemical mechanism behind fuel combustion, specially about how it starts and how it propagates.

i think its not really managable in the petrol engine process where a mixture of fuel and air is sucked and then commonly compressed. a self ignition is in this case uncontrollable. when the engine is relativly cold and at low rpm the mixture would ignite very late or even not ignite, when the engine is hot and at high rpm the mixture may ignite early, much before TDC. the spark controls the point od the ignition, in the diesel engine, everybody knows, only air is sucked and compressed and shortly before tdc fuel at high pressure is injected anbd ignites nearly immedietaly. of course also the current compression is much to low for any self ingnition

so at the diesel the time point of fuel injection gives also the time point of ingnition, like in the petrol the spark.

[flynfrog]

as far as heat igniting a mixture top fuel cars no longer need spark plugs (they melt off) after the 60ft line they fuel is igniting off the heat of the exaust valves