Turns out the Mercury Outboard uses direct air injection.
I did not know that. The compressor is upper right.
Paul Lamar
Paul,
I believe I mentioned that.
The fuel Injector sits atop the air injector ( piggy back style) with
compressor located remotely.
George ( down under)
Paul,
Stirring thoughts in the night:
Please confirm I have this right. The purpose of the direct air injection
is for fuel delivery assistance into a highly pressurized environment,
right?
So if I read some of the research papers correctly, the challenge with
direct injection is in obtaining a homogeneous fuel/air mix in a relatively
short amount of time.
Still pretty rough technology. Squirt in some liquid hydrocarbons, try not
to bounce it off of the walls of the moving rotor, and then light it off.
Shouldn't the science of aerodynamics apply to the nature of mixing liquids
in the rotary combustion chamber? I would think the texture of the rotor
depression face could enhance the combustion by having a large surface area
(sputtered coated titanium ?) and perhaps also act like micro vortex
generators to mix things up a little.
Perhaps the delivery of fuel into the area of the spark plugs warrants a
rethink on what constitutes the compression chamber of the rotary engine.
For example: have a depression on the housing side as well. That way a
shallower rotor depression as well as the housing depression could be
texture optimize for mixing and heat retaining characteristics and the
combustion event triggered when the two depressions line up. Multiple corona
discharges bridging the gap between the two depression would be another item
on my wish list.
Then the fuel and combustion event could be localized and obtain the similar
advantages of a piston engine. Ah but words are cheap neh?
Back to grinding and sanding FRP.
Doug in Japan
Yes... probably in the Mercury outboard. I am not sure exactly what
is going on there. Perhaps the high pressure air injection mixes the fuel
and air better. I think that is a problem with direct gasoline
injection. The fuel does not get a chance to mix with the air
thoroughly before some of it burns.
In my design the air injection has another function. It is
to purge the trailing portion of the combustion chamber of air
fuel mixture and replace it with pure air thereby promoting
stratified charge with good (the same) air fuel mixing. The difference
is the air and fuel can mix back in the intake runners and in
the compression chamber. No expensive 20,000 psi fuel injectors
required.
I don't think a depression in the side walls would work. You
would have a sealing problem as the side seals traveled over
the depression.
Paul Lamar
Paul
Yes your idea does have merit. Predominately moving the squish area down
into the burn area. You will need several Hp. to drive the compressor
though.
The merit may not be better BSFC but a cleaner burn, ergo less pollutants.
One question. How can the injected air be at only 150 psi if direct fuel
injection needs 20K psi to function?
About the housing.
A small cylindrical (cannon like) depression with housing surface area no
larger than the exhaust P port would seal just fine of course. Mount the
spark plug within this cannon and decrease the rotor depression volume
accordingly to achieve the same compression ratio. The small cannon chamber
technique is used by Gami, and to some extent by Mazda direct inject to
create a pre burn stable area around the spark plug which then fires a large
multi prong flame into the main chamber. Better burn is claimed. Perhaps
the rotor depression shape could then be optimized to direct the explosive
force further out near the rotor face increasing the torque.
Doug in Japan
Because 20K psi is what it takes to get well atomized fuel.
Current diesel engine fuel injectors are in the 20K psi + ball park.
Just before the spark plug fires the pressure is about 150 psi
in the combustion chamber due to the 10:1 compression ratio
assuming a VE of 100%.
I think that is called a pre chamber. A company called
Pats built a rotary like that. So far I think it bombed for some
strange reason. Also as I recall CW did some experimentation
with pre chambers.
Mazda also did extensive experimentation for the optimum
shape of the rotor depression. The RX8 is yet another different shape.
Paul Lamar
Doug, Here is some work Mazda did early on.
Paul Lamar
Something like this Millar cycle engine is probably what Mazda will
go with on the 16B direct injection engine. It has the tremendous
advantage of cutting the pumping losses at part throttle operation
typical of passenger cars. The V6 Millennium got 3 mpg better fuel
burn in the EPA city cycle than the regular Mazda V6. The rotary is
in dire need of a better city cycle MPG number. Unfortunately it
won't do us much good in the aircraft engine mode.
Paul Lamar
Here is a somewhat easier to read version of that last scan.
BTW this is from the new book published by Mazda with
the title "RX8" edited by my old friend John Dinkel (we are both old) who
happens to be a lurker on here so I better give the book a plug :)
Paul Lamar
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