atomization enhancement

[Jennifer and Brock Fraser]

>     I find that number hard to believe if my conversion figure is
> correct 1 bar = 14.5 PSI (rounded).  26100 PSI........  You won't
> catch me working around one of those systems... a leak could easily be
> fatal!     It that the system on Caterpillar I've heard about where a
> cracked line can cut put out a fuel stream that will cut steel.
>     The Ford "Powerstroke" I've been told is a single rail system
> which has an oil pressure driven injector which is computer triggered.
> An extra oil pump supplies pressure to the injectors which use the oil
> pressure to create high injection pressures.  I've never worked on the
> power stroke..... only the old 6.9 & 7.2 engines which used an
> ordinary rotary pump.  New injectors for the Powerstroke are $500.00
> each according to the local Ford people.... I suppose $4k for a set of
> injectors isn't so bad if you can afford a $40K pickup.

Ahhh...  It's a special day when the efi hot-rod discussion group starts
talking about Diesel combustion and fuel systems.

You CAN believe your ears here, folks.  Common rail (this is what it's
usually called, rather than "single rail") fuel systems can go as high as
1800 BAR (yes, that's around 26,500 psi!).  An analogy was drawn by somebody
else to the typical gasoline fuel injection system on most automobiles, and
yes, it's the same idea.

The extremely high pressures are commonly generated by a piston pump running
at engine speed.  And, as you guessed, the lines and rail have to be very
beefy material.  These injectors aren't cheap.  Imagine an injector
(typically 4-8 holes) that can withstand that pressure, and still react
quicker than an automotive fuel injector.

I've often wondered what would happen if you tried to squirt gasoline at
these pressures.  I'm not enough of a chemistry type to know how gasoline
reacts at extremely high pressures.

Even the lowest pressure Diesel systems used today have roughly 600 BAR
operating pressures.

Other designs you may have seen are "unit injectors" or "unit pumps".  Unit
injectors are either hydraulically assisted and electronically actuated
(HEUI) or they are cam assisted and electronically actuated (EUI).  Either
way, the fuel is pressurized right at the injector as opposed to the common
rail that has a supply pump that is commonly gear driven off the gear drive.
Unit pumps are individual pumps, one for each cylinder, that are cam driven.
It's much like EUI, but the pump is seperate from the injector and connected
by a line.

I'm sure that's more than you wanted to know about modern Diesel fuel
systems.  Now somebody try to postulate what would happen if you used one of
these with gasoline...

I'm a high-speed gas engine fan (at heart), but some days I can't help but
smile when I see 850 lb-ft of torque at 1300 RPM out of 6.4L on 30 pounds of
boost.  Heck, 280HP at 2300RPM is no slouch, either.

-Brock