X-Mozilla-Keys:
Ken Powell wrote:
Help!
I don't understand the theory behind this. Do you size the turbo for
a max boost (say 6 lbs) at sea level? Does this mean that you cannot
overboost the engine? What kind of boost will you get at 15,000 ft
(does the boost drop with air density)? How much boost is 'safe' for
a rotary if running an intercooler? What is the recommended timing?
Is a timing retard device necessary? Do you have to run a richer
mixture at cruise to promote cooling? What else do I not know?
I can't answer a lot of these questions myself.
I could not begin to to do the subject justice.
Jeff is your best bet as his work airplane has gone to
65,000 feet and he is the chief engineer.
Paul Yaw has recently completed a 255 HP 13B.
http://personal.riverusers.com/~yawpower/
Here is a couple of references; TURBOCHARGERS by Hugh Macinnes
HP Books and Maximum Boost by Corky Bell Robert Bently.
Also try this web site.
http://www.turboneticsinc.com/
I personally am going to try for the maximum boost I can get at sea
level with a TO-4 turbo charger at 6200 e-shaft RPM and then limit
the throttle opening to about 230 HP or so for longetivity.
I will monitor things like turbo RPM, intake manifold temperature
and turbine inlet temperature to insure the engine does not;
A:detonate
B: the turbo does not overspeed or
C: the turbine wheel does not melt.
I obviously do not know enough much about turbos, but I want to learn.
I have been following Jeff's posts and like the idea, but need to
understand what is going on. Maybe more people will be interested if
the subject is understood better.
Ken Powell
Here is an old message on the subject.
tom mayer wrote:
David,
My wastegate was probably off some Rayjay system. I just don't know. I
found it in an aircraft wrecking yard in Artesia, NM. The proprietor did
not know anything about it. It was the correct diameter tube, so we used
it. But it looks like all the old Rayjays.
The metal to metal seal was singularly imperfect, at least you could see
lots of daylight with the wastegate closed before it was welded in place.
That did not seem to matter much, at least on this installation. I am a
terrific coward and have not found what the critical altitude is. I
established a set of parameters, mostly by talking to Van Carpenter, who
used to own Turbo Flite in Pagosa Springs, Co. (He's sold out, and the new
owners are in Oklahoma.) He had STCs for turbo retrofits to angle head
IO-360s in retractable Cardinals, maybe other planes. Van told me what
turbo to get--Airesearch 465292-9002--it's what goes on the IO-520 in the
turbo Ag-Wagon and on the carburated 0-540 in turbo retractable C-182s--and
where to get it, from Main Turbo, ask for Gary, 800-847-8815. I have no
idea if Gary would be of any help with a turbo rotary project, but he surely
knows the aircraft turbo business and his prices were more than reasonable,
for the airplane world.
On the Cardinals Van used 28.5 inches as MP redline at 2700 rpm. 25
inches and 2500 max cruise. Back off an inch of MP for each 1000 feet above
16,000.
I run much more conservatively than that. Take off at 2700 with
wastegate wide open. When safely airborne, rpms to 2500 and mp to 23
inches, hold that to altitude, then cruise at 21.5 inches and 2300 rpm,
which in std conditions should be about 130 hp.
EGTs peak at 1375 to 1400. I run 100 rich.
The manual wastegate used to be really twitchy above 12,000. I had a
new wastegate fabricated by Don Carter, a machinest, and I changed the
linkeage. Now setting power during long climbs and in high alt cruise is
much less demanding. The new wastegate also fits much better than the old,
stock one, but getting power was never a problem. The new one is made out
of a 1/8" piece of 321 stainless.
One big problem, which the turbo rotary of my dreams will not
have, was keeping the jugs warm on long descents. I tried all sorts of cowl
flap arrangements, and none were satisfactory. I ended up building simple
adjustable ramps to close off part of each inlet, and that ended the
overcooling hassles. I tried a bunch of different cowl flaps, and if anyone
is interested I can explain what the problems were. But, in my experience,
the Russians are light years ahead of Cessna on airflow control.
An auto wastegate control would be nice, but all the aircraft systems I
looked at cost an arm and a leg and an unmentionable, and were too bulky to
fit in my limited cowl space. Jeff Nielson at planB@IX.netcom.com has an
idea I'd like to pursue--use a MP sensor, a chip and a RC model servo to
control MP. Jeff has an RV-6 he flies 99.9% with his lap top.
Hope this is what you were interested in.
Tom Mayer
--
The Aircraft Rotary Engine Newsletter. Powered by Linux.
http://home.earthlink.net/~rotaryeng/ http://www.linux.org