Bill,
I just can't seem to visualise in my mind, what you are saying -
a flat
plate restricting the exhaust flow, seems counter productive?
A small drawing would help!
George (down under)
George I'll do a drawing. The way to think about it is this,
think of the standard round canister with one flat slice on the
primeter.
Very little restriction but it forces the flow to be turbulent. The cool
tube concept could still be used.
Bill Jepson
Ok George, Here's the muffler drawing I promised.
I hope all will now become clear!
Bill Jepson
Bill,
Are you still out there buddy? I thought of using your design and mounting
the turbo for the turbo compound system in the center of the area that you
show as being flat except I will keep it round. I think for turbo
applications it would be better to keep the air smooth and so place some
curved baffles within the pipe to direct the gases around and towards the
center.
I like the idea of grabbing some cabin heat from this design or at least in
the testing phase to be able to lower the TIT and record the power losses.
If the turbo compound is disengaged when taxing then it would be nice to
have something to quiet the system down as well. Depending on the turbo
used I would still keep the down pipe perhaps exiting closer to the turbo
flange and install a waste gate in it. Still thinking about it. RAJAY
turbos have a great reputation in aircraft use and have the operating range
we are looking for. I don't know the internal design or if the exhaust path
is axially divided as mentioned on page 19 and 20 of Huge MacInness' book
TURBOCHARGERS for good torque at lower speeds. RAJAY aircraft turbine
housings are made with high $$$$$$ 25-30% nickel content are usually
because
of the high heat load encountered.
No, Paul I haven't sold the 2nd gen turbo yet:) I know what you are going
to say and it may be wise to start testing with that one first. I wish it
was bigger and slower though as I think the standard unit will be rapidly
toasted operating it in the 80K range. Perhaps we can change to a higher
A/R
housing?
Cheers
DougFir
Doug,
I am certainly still here! The set up I drew for George was for a
muffler used on a normally aspirated engine. This arrangement would be
bulky to use as a manifold for a turbo. I would be glad to work with you
if you need a custom layout. The jpeg you posted is a variant of the
muffler used on the Jabaru which is very quiet.
Bill Jepson
Bill
That's good. I was afraid you were banished to never never land when Paul
purged all of the AOL heretics:) My needs are to provide a lighter weight
manifold, a source of capturing heat for the cabin, a method of mounting the
turbo up high enough to connect to the turbo compound traction drive, and my
desire to have a low resistance muffler.
Perhaps wisdom dictates to use a very short header or manifold for the
turbo. The standard one is HEAVY and Racing Beats and others look like tree
trunks, making it difficult to make a heater muff. I like Paul's via Russia
idea of the rectangular pipes coming straight out the p-port. Perhaps the
tank can be a lot smaller in diameter and jacketed with another layer of
stainless.
It sure would be nice to be able to cut the sound while retaining the heat
and not restricting gas flow or pressure. A preliminary expansion chamber
and a turbo should make for a VERY quiet engine.
Generally with turbochargers a muffler is not needed but my engine will be
turbo normalized or actually supercharger normalized and turbo-compounded.
At sea level without boost the waste gate will be wide open and hence LOUD.
Putting a muffler downstream from the turbo is space and weight and HP
consuming. Space is not the problem. I will have to make a custom engine
cowling because the standard one is oversized for this engine. I am trying
to keep weight down to improve the CG characteristics though.
Putting it another manner, I literally weighed up all the "wish I coulds"
and it seems most logical to make the design multi functional. A very short
exhaust pipe (ALA Paul's advice) right out the side of the cowling is then
possible.
Below is a picture of how Tom Parks did his turbo. No spin that I know of
but more of a log manifold. Nice Inconel set up. Note how the waste gate
connects.
For the spin muffler, heater combi I have no idea however of dimensions of
the inner pipe, baffles and surrounding chamber and thickness of said parts.
I would appreciate your advice. I have stainless 316 and TIG welder in hand
waiting to mock up a prototype. Assume a four bolt pattern exhaust port.
Final design after testing would be in Inconel where appropriate.
Thanks
DougFir
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.
