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How fast a fuel burns

Trick question ?-----But on a 2 stroke running at 5000 RPM there is not much time.----like 10 milliseconds or less.
 
Trick question I guess.-----Or how long does it take for bullet to leave the barrel of a gun ?----How long does it take for a fission bomb to produce it's power ?
 
Lets talk about outboards that in general run around 600RPM at idle to 4-5000RPM at fun speeds. For most of us I would imagine. Starting at the low end, Idle. And I'm targeting this at 2 Stroke owners, as this is where the issues most lay.
 
Ava Joy said:
Lets talk about outboards that in general run around 600RPM at idle to 4-5000RPM at fun speeds. For most of us I would imagine. Starting at the low end, Idle. And I'm targeting this at 2 Stroke owners, as this is where the issues most lay.
Click to expand...
Fuel, mixed with oxygen, burns at a constant rate and produces pressure as the gasses expand. The optimum mix of fuel to oxygen ratio for petroleum is 14.7 parts oxygen to 1 part fuel and is known as the stocimetric ratio. So this is kinda a fixed variable. Add more fuel/oxygen and the rate of burn will change. The other variable is ignition timing.
So. Suck, Squeeze, Bang, Blow is basically it. The difference between 2 stroke and 4 stroke is mechanical. The secret is understanding those secrets. How each mechanical mechanism treats suck, squeeze, bang blow - their tansition from idle to pick up and on to power flow with air, fuel and ignition is quite different.
Every engine is designed on it's BMEP. How far down a pistons power stroke the full burn of fuel produces the maximum push on the piston. Timing is the most variable.
Cheers
 
Engine runs at say 6000 RPM.------So turns 100 times / second.------Fuel must burn during 1/20th of a turn.----Easy math I think.
 
Ava Joy said:
Fuel, mixed with oxygen, burns at a constant rate and produces pressure as the gasses expand. The optimum mix of fuel to oxygen ratio for petroleum is 14.7 parts oxygen to 1 part fuel and is known as the stocimetric ratio. So this is kinda a fixed variable. Add more fuel/oxygen and the rate of burn will change. The other variable is ignition timing.
So. Suck, Squeeze, Bang, Blow is basically it. The difference between 2 stroke and 4 stroke is mechanical. The secret is understanding those secrets. How each mechanical mechanism treats suck, squeeze, bang blow - their tansition from idle to pick up and on to power flow with air, fuel and ignition is quite different.
Every engine is designed on it's BMEP. How far down a pistons power stroke the full burn of fuel produces the maximum push on the piston. Timing is the most variable.
Cheers
Click to expand...
2 strokes also have port timing another variable I think.
 
Well ---2 stroke or 4 stroke at 6000 RPM.---The fuel must burn and expand the air during about 1/20th of a turn.-----Ports have nothing to do with time required for the fuel to burn.----BMEP= brake mean effective pressure.
 
There are other variables that affect the flame front, even shape of the piston.
Decades ago, we had a module on combustion engineering.
Though it was within jet engines, some was with piston power plants.
There were some interesting high speed films showing the flame front & flame propagation. With jet engines, (basically glorified blow torches), the most critical aspect was to keep a continuous smooth flame. Anything that disrupted the burn would result in rollback or compressor stall. Sometimes it would self recover, with a lot of banging, flames out the back, & other passenger frightening issues. Other times, flameout, requiring shutdown. As long as the hot section, & the bypass fans showed rotation & oil pressure, a relight could be attempted.
 
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