On Mon, 09 Jan 2017 12:27:25 -0800, wrote:

Greetings Clare,
I just thought a few minutes ago how a fuel injector might be a good
way to apply Minimum Quantity Lubrication to cutting tools. I figure
you or someone else here must know what the minimum amount of fuel is
that can be delivered from a typical gasoline engine fuel injector.

In another life I designed and build electronic fuel injection
computers and installed them in a wide variety hotrods. I also built
a fuel injector flow bench in which I could measure the flow and take
high speed movies of the injector opening and closing. Unfortunately
I lost most of my research in a fire. I can recall a few details from
memory. This is from the mid-80s to early 90s.

There are two basic types of port injectors, the pintle valve and the
disc valve. I understand that some small engines are now using piezo
valves but that was after my time.

In the pintle valve, the solenoid lifts a conventional valve stem off
a conical seat. The stem typically (but not always) extends outside
the injector to help shape the spray. The spray pattern is atomized
in a similar way a garden hose nozzle breaks up the stream.

This type of injector was used on Ford, Chrysler and most jap cars and
was aimed at wetting the back side of the intake valve before the
valve starts opening.

The disc valve uses the electromagnet to lift a disc off an opening to
the outside world. The stream is sharp and solid. Only GM used that
type of injector. It was aimed to shoot into the intake as the intake
valve starts opening. The advantage is that the injector is fast. The
disadvantages are that there is no flow modulation possible and the
flow capacity has to be large for a given engine relative to the
pintle.

Both injectors take about a millisecond to open and another to close.
with the pintle injector, flow starts as soon as the pintle lifts off
its seat. So one can modulate the flow below 1 ms by using a
peak-hold driving circuitry and by turning off the current before the
injector is fully open. Peak-hold hits the injector with a few
hundred microseconds of high voltage (45 volts in my design) and then
is sustained with a constant current with a compliance voltage of 10
volts.

My flow bench was equipped with an accelerometer so I could see the
pintle start moving and see it hit the stops. This modulation
technique allowed me to achieve a larger turn-down ratio than possible
with a simple constant voltage drive.

The SAE standard for measuring the performance of fuel injectors
specifies hexane as the test fluid. Way too volatile for me so I
settled on mineral spirits (basically naphtha.)

Most engines used a differential pressure across the injector of about
45 lbs. The pressure regulator is referenced back to the intake
pressure so that the differential is always the same.

I found that increasing the pressure slows opening but has little
effect on closing. I tested up to 100 psi differential pressure and
found that this slowing followed a nice clean curve.

If I was assigned your task, I'd first settle on a lube. I dilute it
to about the viscosity of ATF or a bit thinner. I'd use a peak/hold
driver and try to avoid having to generate very brief pulses.

In general, the flow rate scales with the cylinder size so you can
pick an injector accordingly. Much better to use a smaller injector
with a longer open period than a large injector and brief pulses.

The only other, one I can't answer, is fluid compatibility. All the
internal parts are wetted by the fluid. Most should be water
resistant because gasoline is frequently wet but that's something
you'd have to test.

I once built a water injection system for a turbocharged engine that
used the large injector from a Mazda RX6 rotary. Each rotor has a
small injector for cruising and idle and a big honking one for power
operation. About 80 pounds/hr on mineral spirits if I recall.

The fluid was a 50:50 mix of methanol and water. Methanol is
corrosive to all light metals but this injector survived just fine. I
think that internally it's all plastic and stainless steel.

End of brain dump.

Feel free to ask questions. They may jog loose some more memories.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address