Crickets? (several days of quiet on the list. I was beginning to think I missed out on a fly-in.)
From you example ......
Could I assume that if my port opening (which is 2” x .78” on the primaries) consisted of a inside perimeter of 4.89” and an area of 1.43 square inches and I used a tube with an internal diameter of 1.55 inches (for a total area of 1.9 square inches) and then changed the shape of the tube to mate with the port dimensions, that the reduction of area from 1.9 s.i. to 1.42 s.i would in effect achieve the tapered effect you referred to below?
From: Lehanover@aol.com
Sent: Monday, August 26, 2013 10:35 AM
To: Rotary motors in aircraft
Crickets?
Intake systems are typically designed to have the
highest possible flow velocity right at the valve pocket or, in our case, the
port opening. So, the ideal runner would be a long tube of smoothly reducing
diameter right to the port opening. The manifold gasket in
my
250 HP Daryl Drummond 12-A bridgeport is the stock
gasket. The runners inside the irons are nearly stock.
Cleaned up well on the outsides of turns, and
a proper shape for open and closing timing. The higher the velocity the
smoother the runner needs to be. A change in velocity is a loss of energy. A
change to higher, or a change to lower, all the same, a loss of energy. The
higher the velocity the greater the effect of any disparity in the surface.
Except where you want the flow to stay attached. For example around the inside
of a bend, or even a 180 degree bend. Those runners are very complex. Note the
ports on any late model Chevy head. Ports shaped like the letter "D"
with the flat back of the "D" being the short radius of the turn. You can play
with this stuff on a flow bench and a pile of childs modeling clay. You can even
find flow going backwards along the short radius while flow along the outside of
the turn going twice what the average velocity is. So, in some systems the short
side in round and "D" shaped ports and runners, you may see tiny holes drilled
or bits of metal stood up with a triangular chisel into the flow like vortex
generators. This to hold boundary layer tight against the inner wall and keep
the outside wall flow at a more constant velocity. Air and fuel air mixtures
have mass, and tend to comply with the rules of centrifugal force. It tends to
flow only along the outside of turns with no regard for what we want or what
makes us happy.
You can make profiles of the runner shape at stations
along it's length. Use 1/8" squares on poster board and a long dowel glued
through the center to start with. Have one former for the start shape and one
for the end shape. Like the port opening at the manifold face on the iron. Now
even if you have "D" shapes in your runners, you can maintain the cross
sectional
area. Or, you can just forget all of this and use a
tube of constant diameter and the engine
will run fine. Crickets?
Lynn E. Hanover
In a message dated 8/26/2013 10:21:29 A.M. Eastern Daylight Time,
echristley@att.net writes:
Tom, I located my primaries in the stock position
on the block. I have my controller using the primaries exclusively at
idle. My working theory is to first get the fuel into the combustion
chamber, and then to have it as close to completely evaporated as
possible. Having the primaries squirting almost directly into the
chamber insures that the miniscule amount of idle fuel actually ends up in the
chamber.
Once I hit 2k RPM, the secondaries start progressively sharing
the load, until they're delivering half the fuel at 4k. The secondaries
are located further back in the runners. By the time the engine is
running this fast, the air is moving much faster in the runners than at idle,
so locating them further back gives the fuel more time to evaporate.
I
have the engine running smoothly from idle to 5400 while doing static
run-ups.
On 08/23/2013 05:45 PM, Thomas Mann wrote:
Hey Chris ..... appreciate it.
You don’t happen to know what size tubes you have (Primary &
Secondary)?
I think I’m getting close to formulating a plan. I’ve gotten some input
from John and Bonzai Racing but the Fly Rotary list has been little help.
Mostly just crickets there.
Thanks again.
T Mann
Sent from my ASUS TF600T using Windows 8
50% Brighter than any
iPad
From: Chris
Barber
Sent: Friday, August 23, 2013 4:34
PM
To: Rotary motors in aircraft
I took some shots of my engine last night. I will try to
post them on the canard aviation site.
Chris
Sent from my
iPhone 5
On Aug 23, 2013, at 7:56, "Thomas Mann" <thomasmann51@gmail.com>
wrote:
> I wonder why nobody sets up the second set of injectors
the same way the primaries are setup (i.e. shoot through the iron into the
intake port. )
> That would sure simplify things and pretty much match
up the fuel delivery method.
>
> Is there a
logical/rational reason this isn't configured in this manner?
>
......or .... has someone already done this?
>
> T
Mann
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