Burn pattern opinions

[automotivebreath]

What causes some areas of the combustion chamber to coat with carbon while other areas remain clean?

 

[patprimmer]

Flame travel, mixture distribution, surface temperature

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[ivymike]

what he said.

 

[automotivebreath]

Flame travel, mixture distribution, surface temperature

So the flame travel stops because conditions are unfavorable for combustion, low temperatures and/or poor air/fuel mixture. Therefore modifications that enhance mixture quality should extend flame travel and accomplish complete burn.

Would the additional heat in the end gas zone promote detonation?

 

[patprimmer]

Additional heat could promote detonation.

Also, liquid fuel particles are much heavier than air, and I would expect, tend to flow straight out from the valve whereas the air turns the corner easier, so I would expect richer.

Soot collects on some areas, but burns off others, so it can be no soot on cold surfaces, or less soot on hot surfaces, depending on mixture, power output and running conditions.

There is more to it I am sure, but I do not have time to elaborate my thoughts right now.





Regards

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[automotivebreath]

Patprimmer,
Thanks, I would love to here more when time permits

 

[franzh]

Understand that the incoming air and fuel is more akin to a fluid with air and fuel stratification, rather than a totally homogenous mixture. What is desired is seldom fully reached. Placing the fuel injector directly at the intake valve leads to this division, relying on ultrafine spray patterns to obtain a reasonably good air-fuel mixture. The rest of the mixture enhancement is up to the piston shape, the combustion chamber shape and the heat of the chamber to enhance combustion.

The piston dome is an integral portion of the combustion chamber and the movement of the piston causes a focusing effect of the air-fuel mixture.

Cylinder wall wetting also contributes to hot and cold sections of the combustion chamber, along with carbon deposits and other mechanical factors.

Franz

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[automotivebreath]

The two examples both show areas wet with fuel, one obviously a better design than the other. My desire is to understand the effects of eliminating the wet areas in the chamber and when doing so will end gas be exposed to higher temperatures eliminating quench areas and leading to elevated end gas detonation.

 

[womble]

I've just been looking at an SAE paper(#950680) on combustion chamber deposits. According to the paper, brown and lighter areas are the coldest (and thinnest deposits), black areas are hot and black "caked" areas (looking like a dry river bed) are the hottest (and thickest deposits) areas in the chamber. The clean areas could be areas that are the coolest, too cool perhaps for deposits to form.