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David, I suspect there will undoubtedly be a bit of
lag before the heat of the coolant/oil inside the engine transferred to the
outside of the aluminum housings - so I suspect the CHT temp would lag (just
don't know how much). But, one would assume after a bit of engine
operation they would stabilize at some temperature as they reach steady state
condition.
However, I have doubts about the
usefulness of a CHT for the rotary engine (or any liquid cooled engine).
Here is my rational.
1. Air cooled aircraft engines transfer the heat
directly from the combustion chamber to the cylinder walls and fins of the
cylinder. So the CHT gives you a pretty direct indication of how things
are going. One the other hand, the rotary (and any liquid cooled engine)
has the coolant inside the engine transferring heat away. So, In
contrast to the air cooled engine, relatively little heat is being transferred
to the outside walls in the liquid cooled engine. Didn't say None, just a
small amount compared to what you are getting rid of through your
coolant.
2. So, I am not certain what a CHT reading will
tell you that the coolant temp won't tell you sooner. In the air cooled
aircraft engine, they of course do not have this option.
3. The CHT for the rotary could perhaps provide some
useful information if it was mounted close to the sparkplug location as this is
reportedly the hottest part of the chamber. But, on the other hand, its
sort of is- what- it -is and I don't how you would affect temperature in that
area much except by keeping your coolant flow cooler. So once again, it
sort of boils (no pun intended) down to your coolant temps.
On the other hand, I certainly don't see any possible harm
it would do to instrument it with CHTs.
Be interested in the results.
So keep us informed, David
Best Regards
Ed
Sent: Sunday, August 19, 2012 11:02 AM
Subject: [FlyRotary] Re: EM2 CHT ?
Sounds like a
plan to me Ed, should have time Sun. to do. David
From: "Ed Anderson" < eanderson@carolina.rr.com> To:
"Rotary motors in aircraft" < flyrotary@lancaironline.net> Sent:
Saturday, August 18, 2012 6:54:35 AM Subject: [FlyRotary] Re: EM2
CHT ?
I think I would run the engine at operational rpms
(>5000) and watch the coolant/oil temperatures - when they got to my maximum
limit, I would check the CHT reading and perhaps add 50 degrees for the limit
(to start with). If I got a lot of false alarms at that margin I would try
another 50 deg. Just a WAG.
Ed
Sent: Friday, August 17, 2012 10:20 PM
Subject: [FlyRotary] EM2 CHT ?
What are we using for high temp numbers from the CHT sensors on the 13B
rotary, I have the under the spark plug style sensors bolted to each rotor
housing in some factory threaded holes just above the spark plugs, not really
the hottest spot but the holes were already in place so I KISSed it & moved
on, now I need to set my high temp warning limit & do not know what to
use. Possibly do an eng. run with upper cowl off & check
bolt/sensor temp with a lazer temp gun at about 4000 RPM & go another
50 deg. higher? Ideas? David R. Cook RV6A Rotary
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