[SEL] RE: Hot bulb/hot tube

Rob Skinner rskinner at rustyiron.com
Fri Dec 30 08:01:36 PST 2005


> Also - Does the description "Hot bulb" or "Hot tube" 
> mean the same thing or are they different animals.

Hi Jerry,
They are both methods of "surface ignition," whereby the
fuel/air charge is ignited by contact with a surface of
sufficient temperature to initiate combustion. 

The specific details are a grey area, as each manufacturer
injected their own nuances into the designs.  Generally, the
differences are well defined, but perhaps someone will
supply examples of engines that defy categorization.

In a hot tube engine, the fuel/air mixture does not come
into contact with the hot surface before the point of
ignition.  As the mixture is compressed, it is compressed
into the hollow tube that is closed at one end.  When the
mixture reaches critical temperature, it ignites, the flame
travels up the tube, and BANG.

"Hot bulb" seems to be a nouveau term that was not used by
the classical engine developers.  "Vaporizer" was used by
the old-timers and it is a more descriptive term.  The
vaporizer serves the dual purpose of aiding the vaporization
of fuel AND the ignition of the fuel.  

Neither of these terms should be confused with what is now
called a "semi-Diesel" -- an engine with compression lower
than that of a Diesel which requires pre-heating of the head
to supplement the heat of compression to initiate
combustion.

=-=-=-=-=-=
Rob Skinner
La Habra, California
mailto:rskinner at rustyiron.com
http://www.rustyiron.com 








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