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I have given some thought to the idea you
mentioned. I am not certain what the results would be. Here are some
thoughts on the topic.
The two primary tubes would create intake pulses
every 60 deg rotary (or 180 deg e shaft) revolution. Same for the
secondaries. The primary and secondary of the same rotor would be near
simultaneous in sucking air. So those two pulses I would think tend to
reinforce each other. Now the pulse theory states that when a FAW
pulse hits an "Open" (relative speaking) it reflects an opposite wave back down
the tube. So if a "negative" pulse hits the TB opening, then it would
reflect a positive wave (helping to push the air toward the intake).
However that wave could be opposing the following set of pulses which it
could interfere with. So would have to do some calculations to see how
long the manifold would need to be at some rpm (high I presume) such that the
positive reflected wave would reach the intake port area in time to
help shove more air in - before running into the next pair of
pulses in the tube.
No! No! no more manifolds (at least not this
summer {:>)) Well, maybe a few calculations.
Lets see - at 6000 rpm the rotation period of the
rotor is 60/2000 = .03 sec = 30 millsec. 6 pulses created(one for each of
the 3 faces *2) during each revolution so we have 30/6 = 5 millisec
between each pulse sets. If you assume sea level speed of sound approx
1100 ft/sec, then for a pulse to be generated by the intake opening, travel to
the TB and back to the next set of intake port openings would be approx .005*
1100 = 5.5 ft. or 1/2 of that for length of runner (trip one way and trip back)
= 2.5 ft or apprx 29". But that was at 6000 rpm and 1100 fps.
For 7000 rpm 60/3500 = .017 sec. .017/6
= .00286 sec or 2.86 millsec. .00286 *1100 = 3.14 ft or 1/2 of that
would be 1.5 ft or 18" for a runner length, at least if my math is
correct. This is only an approximation but should give you an idea of
lengths.
Ed
----- Original Message -----
Sent: Sunday, May 08, 2005 1:07 PM
Subject: [FlyRotary] Re: 4-port intake
measurements
When I combined my
primary and secondary on one of my intake designs I used a 1.75" dia tube,
so sounds like your dimensions closely agree. I currently have a 1
1/2 and 1 1/4 for the secondary and primary respectively. So that gives
me a total of 2.99 sq inch runner area per rotor. So approx .45 sq inches more
per rotor than you currently have, so I would say your current design could be
restrictive.
Thanks
Ed, That's pretty much my conclusion too. While it's certainly
making good power, it could clearly be better, so it's probably
worth the hassle of making another intake.
I'm not
sure if we ever cleared up this business about whether you need a single
TB big to allow for both rotors, or just one at a time. That was at
the heart of the Ellison debate. Interestingly, if you add the
sizes of the ports on both rotors, it comes to an equivalent tube of
about 63mm ID, which is right in line with the recent discussion of TB
sizes.
Here's
another wacky idea for your entertainment- I'm familiar with
the scavenging concept used in exhaust systems. For one bank
of a V-8, you start with 4 pipes, then combine them to two bigger
pipes, and finally one even bigger pipe. The thought is
that active flow from one pipe is creating a suction on the others to
help pull out exhaust of a cylinder that's almost done with it's exhaust
cycle.
Will this
work in reverse? It almost seems like it would to me. What
would happen if you start with two primaries, and two secondaries, then
combine them to make two larger pipes (one for each rotor), then combine again
for a single larger pipe with a TB on the end of
it?
Cheers,
Rusty (more
power Scotty)
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