[Gasification] combustion math question (help needed)

[David G. LeVine]

At 12:04 PM 11/19/2007, you wrote:
>   For me is necessary to increase not only compression ratio nor 
> rpm because power is addition of every cycle . We have less power 
> every time and risk of overheat is lower then we need to increase 
> number of rotations. If you use 3.000 rpm can link direct to shaft 
> an AC generator 50 cycles with better damping factor. What is 
> this?. When you connect some motor appears short circuit current 
> because motor is starting. In 60 cycles 3.600 rpm. With water pumps 
> high velocity increases efficiency.

Benjamin,

Either I am misunderstanding a question, or my information is 
bad.  Higher RPMs increase HP output only to a point.  Let's assume a 
1 meter diameter cylinder and a 50 M/S flame propagation rate at full 
compression.  Since the flame will propagate .5 Meters from the time 
the plug fires until the charge is used up, it will take .5/50 or 
0.01 second.  Now, at 100 RPM this means that the flame front can't 
propagate the full cylinder before the exhaust valve opens and vents 
the still burning charge.  At 10 RPM, the charge only takes 1/10 of a 
revolution and, with a 5% advance, will completely use the charge 
before the exhaust valve opens.  At 1,000 RPM, most of the charge 
will be wasted.

Admittedly smaller engines and better mixtures may work a lot 
differently, but the principle remains.  BHP increases up to a 
certain RPM, then drops off quickly.  Look at the HP/RPM curves for 
most modern gasoline engines to see this.


David G. LeVine
Nashua, NH  03060