Describing combustion

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Fahlin Racing
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Re: Describing combustion

Post by Fahlin Racing » Wed Nov 17, 2010 7:52 pm

Could anyone help me out in the realm of comprehending burn patterns on pistons etc. Sure I have seen many pictures on Speedtalk, but the one thing I would like some guidance is with the veiwing of the results on the piston crown & chamber itself. The first thing that should be known is the type of head used as far as induction and in-cylinder flow is concerned, but, also the combustion chamber that encompasses our burn-cycle.

I am ready to take notes from who is willing to teach how to read and comprehend burn patterns to further improve the burn-cycle. I greatly appreciate everything I have learned from others previously.

Thanks,
Jim
Jim "Iron Giant" Fahlin ~ A high performance car is like a guitar, you have to tune it to achieve your best operation and pull ahead of the competition.

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David Redszus
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Re: Describing combustion

Post by David Redszus » Mon Dec 06, 2010 11:16 pm

What seems like a very simple question is, in reality, a bag of snakes.
Your question is very difficult to answer properly and is always open to various opinions, most of them wrong, including this one. Probably.

Flame fronts are very erratic and often do not trace the same pattern with measurable repeatability. The flame front will pursue the hotest part of the combustion zone.

The flame front will go out when it runs out of fuel or the temperature drops as when in contact with a metal component.

A charge with proper fuel ratio and properly mixed will produce virtually no color on combustion surfaces. The dark deposits are due to liquid fuel (mostly unevaporated droplets) that have been heated to a state of partial combustion. It is a process called coking.

Combustion is a three dimensional process to which a fourth dimension called time is added. The critical combustion process occurs within the flame fireball and not at the wall surfaces. We do not know at which point in the combustion cycle, which lasts for only about one milisecond, the flame front comes in contact with chamber or piston surfaces.

The combustion phenomena cannot be correctly measured with pressure traces nor photographed optically. New combustion visualization methods are being developed using CFD techniques; these are high end, computer calculation time hungry and very costly.

For a better insight into the aspects of the combustion process, I would recommend visiting the web site of The Combustion Institute. They represent the current state of the art thinking regarding the nature of the combustion process.

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Re: Describing combustion

Post by Fahlin Racing » Sat Dec 11, 2010 6:38 am

Thanks David. Could there be a thread on Speedtalk with some burn pattern analyzing that you might have seen? Anyone have any input as well?
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Re: Describing combustion

Post by SWR » Sat Dec 11, 2010 6:53 am

Fahlin Racing wrote:Thanks David. Could there be a thread on Speedtalk with some burn pattern analyzing that you might have seen? Anyone have any input as well?
The Singh grooves thread had quite a bit of that..
-Bjørn

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