Paul, I also have some skepticism on the claims made by coating firms. That said, I can say that
the jet hot process does decrease radiated heat noticibly. I used a ir thermometer and saw a
difference of 10-15 degrees f inside a racing motorcycle fairing. The concern I have is specific
to the rotary. Jet-hot and several others list a max temp for some coatings. I believe the binder
is what breaks down. I don't know what the failure mode is. The temperature reduction I saw isn't
that great, but the exhaust didn't corrode which is almost worth the price of admission. We were
using mild steel tubing tig welded. The dyno showed about 1 hp increase after coating. Also a plus
but the difference is less than the dyno margin of error. I was satisfied with the Jet-hot
process. Some of the claims do seem over-the top though.
Bill Jepson
P.S. to Paul, I see that you look to be correct about the Williams jets. Did you see that eclipse
says they don't produce claimed thrust, they have gone to another manufacturer.
WRJ
Well the other manufacturer will also have a few problems too. As I understand it the problem
is one of scale. As you make a turbine or compressor smaller in dia. The clearance
gap becomes a larger part of the total loss. The efficiency and thrust goes down.
Here is a little trick that Mazda used on late RX7 turbo chargers.
A big problem is finding enough storage volume in a small jet to carry the necessary
fuel for a reasonable range. This of course is related to the efficiency
of the turbo fan engine used.
I think a turbo three or four rotor engine would work great in a 300 to 400 MPH
airplane and not burn near as much fuel. Range would be excellent.
BTW I was thinking a sequential turbo four rotor engine would solve a lot of high altitude
operation problems in helicopters. It is possible to get a intermittent combustion
engine up to real high altitudes with the proper turbo charger set up.
Our man Jeff Spitzer got a Rotax 914 up to 57,000 feet in a Predator.
Paul Lamar
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