Alan, thanks for the invaluable information. Any information from your and
Everett's work is welcomed. I talked with Everett a couple of times on the
phone. Sorry I never got to meet him in person.
I just received my Flowmaster Hushmaster Muffler yesterday. It's the same
that Tracy is currently using. It's made out of 304 stainless, and appears
to
have a cone of perforated metal at the inlet
and outlet. If it's not quiet enough, I'll construct a "Swiss" muffler to
stick on the end of that. A Swiss muffler is described in Tony Bingelis's
book "Firewall Forward".The exhaust system one
area on the rotary that deserves the best design possible, so your
experience
is most welcome here.
Brian Trubee
I suspect the reason turbo charged engines have lower BSFC is because of
the intercooler. The intercooler represents a loss of over all heat.
It takes HP to compress the air despite the fact most of it is coming
from the waste heat in the exhaust. There is some back pressure associated
with turbo chargers. Part of the energy stored in the compressed
air is in the form of heat. If you throw that away in an intercooler
you are losing some energy from the gallon of gas. The answer is to extract
as much energy out of the exhaust as possible in the form of turbo
compounding.
Here is a heat balance chart for a RR Merlin aircraft engine. 2.5% is needed
to
operate the supercharger.
Paul Lamar
Paul
Thanks for your thoughts on turbo charging and energy loss through the
intercooler. I'm not sure I follow you however. The intercooler losses heat
from a net energy gained through turbo charging. In any case I heard today
my turbocharging book by Hugh Mc'G. is in the mail from the states. I'll
read it and learn.
What exhaust system would be the best for mounting the turbine for the turbo
compound on the Renesis?
A design with little restriction and drag on the gas velocities I suppose.
I was thinking a Jerry's spin design with a cockpit heating pipe through the
middle and possible baffles to direct the exhaust gases to the outlet on the
top pipe middle. I was thinking 3" or 4"ID inconel with a 1 1/4 through
pipe. The three individual exhaust pipes come straight out and are shaped
and welded to the fit the main pipe contour on top. Exhaust gases come
straight out entering at a tangent and spin 180 degrees down and around the
central heater pipe and up towards the central outlet. Inconel pipe is heat
shielded outside. Turbine has cool water jacket.
Your thoughts?
Thanks
Doug in Japan
Well yes it does but don't forget BSFC is related to power out.
Power is up but so is fuel consumption even more. BSFC is the ratio.
I am not sure I follow you on the exhaust system. What type of turbo
compound system are you proposing?
Paul Lamar
Paul
Now its my turn. Jeeezzzzzz. I thought I described it to you before:)
Yea I know ...Get Rhino. Soon..soon
This is the same concept as I mentioned to you months ago and your comment
was "interesting... very interesting". I think you got busy with the
planetary gear approach, Paxton ball superchargers as well as encountering
high gear line speed velocities. No planetary gear or C.V.T. in this
concept. Only one power turbine with a attached gear box with two PTOs.
Gears are helical and arranged on four parallel shafts. This is including
the turbine power shaft. Think about the little gear boxes in auto push
toys or clocks. Big gear and little gear on same shaft to make for compact
step down gearing and in our case, if the gear handedness on the shared
shaft is reversed, to cancel out some of the thrusting action inherent in
helical gears. Each PTO output has its own soft magnetic connect or or if
you prefer electrical activated clutch like they use on new go karts. The
two PTO outputs descriptions are as follows.
1. Compressor PTO: with an attached 3Kw generator. Output ratio 1:2 up.
Power turbine shaft sun gear is about 40mm in dia. Secondary
compressor/generator shaft gear is about 2Omm in diameter. If max turbine
speed is 50K that means the compressor/gen. will be driven at 100K. However
even with a small compressor it may be to much boost so the generator will
be activated from the manifold pressure sensor and 'clamp' the amperage on
and off rapidly to keep rpms and hence boost at the required level. Backup
safety system is a pressure release valve before the intercooler. My company
has thousands of wind generators in the field in extremely windy mountain
tops using this control system. It took years to perfect.
2. Compound PTO goes through a step down sequence of four gears on two
shafts. I found these gears in the KHK catalog we were looking through for
the planetary concept. Data looks good for module 2 for first stage and 2.5
gear size for second stage. First stage gear of 100mm dia. contacts the
other side of the turbine power shaft 40 mm dia. sun gear. Line speeds
should be acceptable in this 2.5:1 step down for first stage. Second stage
can have a 50 mm gear sharing the first stage shaft and meshes with a125 mm
dia. gear on the four shaft to create another 2.5:1 step down ratio. Total
step down ratio is 5:1. At max turbine speed this is 10K. Further step down
to bring the compound rpms to within 1000 rpm above max e-shaft speeds can
be accomplished with pulley ratios.
Depending on how the gear box is laid out the compound output shaft may
clear the power turbine housing allowing the compressor to be on the front
(tractor) side. Connection between compound PTO and engine block mounted
bracket, clutch and pulley can be a carbon fiber drive shaft. Other end of
the belt connects to the water main e shaft pulley. In the real world
the turbo compound might only be used in the 45 - 55% range for best fuel
burn at 8,000 ft. In critical climb modes?... the heck with economy. Boost
to the limit and put the remaining two hp back to the starter motor. So for
PR purposes we marginally have a hybrid motor with turbocompounding
abilities.
Basically an either/or system.
Total turbine failure will require and exhaust by pass. Direct connect (in
bell housing) starter/generator will still provide the power to charge the
battery and run the engine.
Doug in Japan
OK?
Doug in Japan
OK parallel shaft gear box I think. That will work I guess. Gears have a limitation
in that the pitch diameter to the depth of the gear needs to be in
a certain limited ratio range. Since the turbine gear must of necessity be small in diameter
to keep the pitch line velocity low that also means it must not be too deep,
or putting it another way, not too wide. What happens with wide teeth is the
pinion gear twist slightly unloading the far end of the tooth. Max line contact
compressive stress then occurs close to the torque input end of the gear. The rest
of the gear width goes along for the ride so to speak.
This is I suspect is why most turbo prop engines and APU's use planetaries with three
large planet gears and one tiny pinion. Line contact length is three times the length of a
simple pinion and bull gear arrangement such as you describe for a narrow pinion gear.
Not to say it won't work. It might.
I hope you get Rhino soon too :)
Paul Lamar
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