Thoughts on GDI in aircraft engines.

Howdy,

Gasoline Direct Injection (GDI) has been integrated into quite a few
automotive engines over the past few years. After reading an article
about it, and googling for the availability of GDI fuel injectors I
started thinking this might be a cool direction to go in for those
persons interested in engine design, particularly the HCI Radial
guys.

One engine I've always thought was elegant was the 29 packard aero-
diesel because it did away with the second valve per cylinder. If they
had had forced induction in those days the old packard radial might
have been a keeper rather than an oddity.

It occurs to me that GDI recreates the possibility of a uni-valve
layout. If there is no fuel in the intake manifold, there is less
reason to seperate the intake and exhaust gasses. With a big venturi
on the intake side, there may not even be a need for forced
induction.

One problem that would certainly have to be overcome in this
arrangment, is that air metering in the manifold is not preportional
to fuel metering. Some exhaust gases may be recycled during normal
operation, particularly during decelaration. If the manifold is 'T'
shaped rather than 'L' shaped, the inlet pressure does not accurately
reflect the volume of air going into the cylinder.

So you'd have to base your fuel flow on something other than manifold
pressure. Probably a combination of a known throttle map (in the form
of a cam or wedge) and a barometric lifter of some sort.

Anyway. If I was going to build a new gas aviation engine, I would be
inclined to look at a radial GDI with 1 valve per cylinder, 1 throttle
body per cylinder, a relatively low pressure centrifugal supercharging
setup on a planetary gear around the prop shaft.

The fuel system would be similar to the bosch piston pump injection
system that was used on the Packard, and many engines since. So you'd
still have 2 cams, except one is for the valves, and the other
actuates the injection pulse. How to handle mixture control still
baffles me. But this is just shooting the breeze. Anyway... Comments
welcomed.

Thanks!

le mardi 21 juin 2011 17:46, s'est penché sur son écritoire numérique:

Gasoline Direct Injection (GDI) has been integrated into quite a few
automotive engines over the past few years. After reading an article
about it, and googling for the availability of GDI fuel injectors I
started thinking this might be a cool direction to go in for those
persons interested in engine design, particularly the HCI Radial
guys.

Forget GDI on an aircraft engine, it is a good thing only when you use
the engine a very low charge with EGR (exhaust gas recirculation) system.
The GDI engines are not better than standard engines at full charge.
For an airplane we kneed light engines and best fuel use at full power.
It may be achieve with mechanical injection.
The best I know is the IO320 in the homebuilt power range, it is
better than most of automotive conversion.

--
http://www.youtube.com/watch?v=1ODCf7J8L0o
Philippe Vessaire Ò¿Ó¬

On Jun 22, 2:30Â*am, Philippe wrote:
le mardi 21 juin 2011 17:46, s'est pench sur son critoire num rique:

Gasoline Direct Injection (GDI) has been integrated into quite a few
automotive engines over the past few years. Â*After reading an article
about it, and googling for the availability of GDI fuel injectors I
started thinking this might be a cool direction to go in for those
persons interested in engine design, particularly the HCI Radial
guys.

Forget GDI on an aircraft engine, it is a good thing only when you use
the engine a very low charge with EGR (exhaust gas recirculation) system.
The GDI engines are not better than standard engines at full charge.
For an airplane we kneed light engines and best fuel use at full power.
It may be achieve with mechanical injection.
The best I know is the IO320 in the homebuilt Â*power range, it is
better than most of automotive conversion.

--http://www.youtube.com/watch?v=1ODCf7J8L0o
Â* Â* Philippe Vessaire Â*Ò¿Ó¬

Can you site a source?

From what I've read thermal efficiency has been increased by designing
the injection pattern and the top of the piston in order to keep the
combustion away from the cylinder walls. I've seen nothing that
suggests this negatively effects performance at wide open throttle.

It occurs to me that with a fixed injection map, mixture can be
controlled with the throttle body. Rather than reducing fuel, you add
air instead to lean the mixture. So there is potential for a fully
mechanical system.

Thanks

le lundi 27 juin 2011 21:33, s'est penché sur son écritoire numérique:



I've seen nothing that
suggests this negatively effects performance at wide open throttle.

No negative effect but no gain...


It occurs to me that with a fixed injection map, mixture can be
controlled with the throttle body. Rather than reducing fuel, you add
air instead to lean the mixture. So there is potential for a fully
mechanical system.
This way is only made to reduce NOx production for lower charges.
EGR don't work for high power output when full cubic inches are needed.


--
http://www.youtube.com/watch?v=1ODCf7J8L0o
Philippe Vessaire Ò¿Ó¬