Mixture and Ignition ...

[Matthew L Franklin]

On Mon, 20 Mar 1995, Jim Conforti wrote:
> I've got a question, maybe you can answer for me ..
> 
> Generically .. (as in overall)
> 
> Does a richer mixture burn faster or slower than a leaner mixture ...
> 
> I *think* that (up to a certain point) that a richer mixture burns
> slower, but produces more power ...

There is a fuel/air ratio for optimum flame speed.  Too lean, it slows; 
too rich it slows.  I was guessing it was around 10 to 20% rich.  That is 
pretty close to max power for liquid fueled spark ignition engines.

> (Yes, I need to read Heywood ... I know!)
You certainly don't have to read the whole book.  :-)  Even in an I.C. 
engine class we cover 20% of what's in there if we're lucky.  See pages 
402 to 403, particularly Figure 9-25 at the bottom of page 403.  Keep in 
mind that the figure is for a laminar flame, and which is not exact for 
the turbulent flame typical in an engine, but it is a clue and a start 
and not a bad guess for guessing the effect of changing parameters.  A 
combustion chemist will probably want to correct what I'm saying here.  I 
only know enough to be dangerous.

Later,
Matt