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Re: The Freau Number



Original poster: Greg Leyh <lod@xxxxxxxxxxx>

Hi All,

The 1.7 is a somewhat elastic value, and surely will depend upon the coil family. However, the most important feature of the Freau equation IMO is the SQRT function, indicating that the average energy density of the secondary volume can decrease as the coil gets larger. One possible exception to the Freau equation? The case of a single coil vs. two identical single coils, phased 180deg and placed 2x apart... 2x increase in point-to-point arc length is obtained for 2x total system power.

On the notation F for a possible Freau number, I should point out that F is already taken by a very important parameter in coil work. You might consider a less ambiguous notation, as Avogadro did for his number, Na.
Nf seems like the logical notation.


-GL


Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

With all this modeling stuff going on, we seem to need to solidify a constant...

John Freau has this equation:

        spark length (inches) = 1.7*sqrt input power (wallplug watts)

That "1.7" seems to be a pretty important number given all this DRSSTC and streamer energy rise time stuff... But that number changes depending on coil type and apparently Streamer Energy Rise Time (SERT) ;-)

I would suggest the constant "F" as this:

        Spark length (meters) = F x SQRT(bang energy x BPS)

"F" would stand for "Freau" so John will be eternally famous!! I would suggest going to meters just to keep things "scientific". BPS would be assumed to be the optimal optimal number, but it should be in there since many have 50Hz power and the DRSSTC can have any BPS it wants...

The units of "F" would be "meters / SQRT (bang power(watts))"

John used "wallplug" watts but that is not quite fair for those that are running lights and fans ;-)) Bang energy is the energy on the primary cap at firing for a conventional coil or the input energy for a DRSSTC. ScanTesla makes that easy to find now...

Obviously, we would want to make our coils with as high of "Freau number" as possible... "Freau" is fairly unique so it would not get confused with anything else...

Comments, observations, thoughts, suggestions....??

Cheers,

Terry