Paul,
I have been thinking about this since the beginning of this time to climb project.
I can't seem to find a reason that it wouldn't work.
The idea is to start the engine using gasoline in port fuel injection configuration
and then once boost is passing 20-30psi to switch over to twin direct diesel
injectors. This would be a constant speed application with that speed being the
highest bsfc point. Boost could be maintained at 40 to 100 psi. Timing is controlled
by the injection and detonation is not part of the equation any longer.
I'm not sure if the housings can handle this type of chamber pressures. Then again
people are pushing them to extreme hp.
Once running on diesel the throttle plates would remain wide open with output and rpm
strictly controlled by the amount of fuel injected. Super lean cruise compared with
gasoline. Heavy load the A/F is similar but diesel is still lighter than gasoline
with more BTUs by volume.
Does anyone have a solid reason this would not work?
Cheers,
Kurt Emerson
The reason the diesel is not popular for aircraft use is the fuel savings
advantages decrease at high power levels and the diesel engine generally weighs more.
Engine weight is extremely important in aircraft.
Paul Lamar
There is a youtube video of a guy experimenting with, I think it was JetA, and
various gasoline engines. It turns out that they all ran with JetA using the spark
plug to ignite the diesel.
One of those was a model Wankel. I say model because it was being used to show the
burn and I think for some model airplane/drone. They wanted to get it to 30K RPM (I
think they meant they wanted the rotor to get to that speed not the eccentric).
It actually ran, and one could see the flame of combustion.
So it would appear that a Wankel can be set up to run using spark plugs. Not sure if
boosted if it would go to "compression ignition".
The idea that you have proposed is one that we used on farm tractors. We would start
them on gasoline and once the engine came up to a certain temperature, we would
change over to kerosene, much more torque for pulling plows.
Paul would have to tell us how well one could make this work with the RE. My concern
would be an air start if one did not have gasoline to get it running at altitude if
one were to run a tank dry and have to switch and re-start. I ran a Cherokee-6 dry on
a tip tank and immediately switch to a tank with fuel (I was anticipating the tip
tank's time to going dry). I lost 300' while waiting for it to get fuel back into the
injectors. And that was trading airspeed for altitude.... This why I am concerned
about re-starting at altitude.
Regards,
Steve Thompson
IMHO it would take a lot of R&D.
Paul Lamar
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