Schlieren combustion

[hotrod]

Using the frame counter the entire combustion event is over at about 475/10000 seconds. That is a duration of .000475 seconds.

If we assume that the major portion of combustion runs from 30 deg BTDC to 90 deg ATDC that would be 1/3 of a crank rotation. 3 x .000475 equals roughly 1100 rpm so this would be similar to idle speed combustion.

Larry



found a math error corrected it equivalent rpm is more like a fast idle.

[automotivebreath]

You make a good point, it looks like every effort was made to reduce
turbulence in favor of a slower more organized combustion event.

[jerminator96]

Originally Posted by hotrod

Although I am interested in what is going on at the piston crown boundary layer in that video the other thing that caught my eye is how the flame kernel shoots to the top of the cylinder at over 70 mph by my calculations and them blooms out against the cylinder head with combustion then moving down back into the main combustion chamber volume from the top rather than from the center. I am curious if that flame kernal motion is driven by boyancy effects (rising like a hot air balloon) or by general mixture motion as the fuel air mix column is compressed by the piston. If the first case it would have interesting effects depending on engine layout with the flame kernal moving towards the high side of the combustion chamber. In a V8 and a flat opposed that means combustion would move down across the piston face from the intake side where on an inline vertical engine it would do as pictured above.

Hey Larry,

Your comment here got me thinking about an odd engine design that I saw one time.



It's one of the late 60's Ferrari 312 motors. As you can see the exhaust is on the "inside" of the heads. So whether you are right or wrong in your thinking, maybe Ferrari (at least at one time) had the same idea?

Jeremy

[hotrod]

I can think of several reasons for that other wise. It could have been done to aid streamlining (aerodynamics) and cut weight with less complex headers and easier maint on the engine. If it was in a typical single seater that would put the headers right behind the drivers head where they would fill that dead space easily.

Just goes to show that the conventional is not necessarily the only way.

Since everyone did not copy it I would presume it did not yield a lot of benefit.

Larry

[jerminator96]

Originally Posted by hotrod

I can think of several reasons for that other wise. It could have been done to aid streamlining (aerodynmics) and cut weight with less complex headers and easier maint on the engine. If it was in a typical single seater that would put the headers right behind the drivers head where they would fill that dead space easily.

Just goes to show that the conventional is not necessarily the only way.

Since everyone did not copy it I would presume it did not yield a lot of benefit.

Larry

I never even considered the possible aerodynamic gains, that's good thinking. Whether it worked or not, it sure made those cars sound awesome.