Fuel Injector Valve Phasing...

Timothy Coste tlcoste at mtu.edu
Sun Feb 11 19:12:05 GMT 1996


In response to Dave Williams comments on injector spray...

   All of my work with injectors is based on other research here
where they use stroboscopes for visual measurements of things like
spray cone angle and such.  The droplet sizing is measured with a
Malvern Particle Droplet Sizer which uses diffraction of a lser
(oops, laser) beam to measure droplet size.  The number given is
the Sauter Mean Diameter.  I'd have to look the formula up for you
if you wanted to know how it's computed.  The machine also gives
percent of droplets below certain diameters.  i.e.- 10% below 10
microns, 30 below 20 microns, and so on.  The starting dribble is
called sac volume.  And sac volume is why I really wish someone
would explain GM's central port fuel injection to me, cause it seems
it would have sac volumes (dribbles) equal to the full spray if
I understand it correctly.

   And yes, our injectors really give sprays where MOST of the
fuel is in small droplets.  Even with these injectors, the
sensors that I am developing and testing to measure wall wetting
still "see" the walls being wetted, even under warm engine 
conditions.  I'll let you know (maybe in an SAE paper?? :) )
the relationshop I find between wall wetting and engine performance
sometime soon (I hope).  Now, production injectors...man, those
things stink!  I hope my numbers bear this out. ;)  Oh, one
side note...our testing is done using Stoddard fluid in place
of actual gasoline (the droplet sizing testing that is...I run
the engine on gas!).  THis is an out-dated dry cleaning fluid
with properties very close to gasoline, but much less volatile.
The silly university seems to have a problem with us spraying
gas around willy nilly.  Stodgy old farts. :)

   Tim Coste
   tlcoste at mtu.edu



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