> Truck engine manufacturers are jumping on the TC band wagon.
> Pratt & Whitney Canada are trying to patent the turbo compound
> rotary so I would not be a bit surprised if they were not building
> some hardware to try it. At least I hope so.
>
> I find it interesting that Pratt & Whitney US and Pratt & Whitney
Canada
> is allied with Rocketdyne.
>
>
http://utc.com/
>
> Rocketdyne was rumored to be working on the TC rotary here in SoCal.
>
> Paul Lamar ...No rotor no motor.
>
>
>
> Paul,
>
> Was messing around with e-shaft direct-drive turbocompound concepts..
>
> Roughly what's the diameter of the flywheel on a 13b? At 6000rpm
an 18
> inch wheel has a tip speed around 325mph and a 24 inch wheel has
a tip
> speed around 450mph.
>
>
> Also, does anyone have some calcs for determining average flow
velocity
> based on volume and pipe diameter? Need to figure out what diameter
> direct drive wheel would be required to interface well with the
exhaust
> flow.
>
> Maybe a 2:1 planetary reduction - the tc turbine 2x the e-shaft speed
> would make the interface between the exhaust and the turbine more
> efficient.
>
> I wonder if a turbo compound could drive through a small automotive
> torque converter - ideally with an electric lockup. They seem pretty
> robust and there are lots of different versions out there.
>
>
http://en.wikipedia.org/wiki/Torque_converter
>
> It occurs to me that the rotary engine might have a big advantage
when
> considering a direct drive (or close ratio) turbo compound - high
> continuous RPM. This can make the size of the wheel smaller and yet
> still have the tip speed close to the flow speed of the exhaust.
> There's no way a direct drive would work on a big diesel.. Aircraft
> operations have it easier too - essentially one continuous RPM
whereas
> road going applications require quite a bit of dynamic range.
Even for
> a tractor-trailer engine which is mostly continuous operation.
>
>
> Matt-
>
> The ring gear is about 12 inches in diameter.
>
> Well you can start with the volume and speed of air going in as a
start
> and knowing air temp of the exhaust you can figure the volume
> and speed of the air coming out. Assume the pipes are the same size.
> Then
> you add heat which increases the volume and speed coming out.
>
> V1 x T1 = V2 x T2 Temperature must be in Rankin. V is volume.
>
> Pressure is constant.
>
> T1 is 100 F or 560 Rankin
>
> (V1 x T1)/T2 = V2
>
> T2 is 1700 F or 2160 Rankin
>
> Speed of the air going in is V1/Area = Speed in.
> Speed coming out is V2/Area = Speed out.
>
> I suspect the mass flow is the same as matter can nether
> be created nor destroyed except by fission.
>
> A 13B pumps as much air as a 2.6 liter piston engine which is about
> 230 CFM at 6000 RPM and a VE of 80%
> At a VE of 100% it would be about 275 CFM.
> With a p-port the VE is 120% so it would pump about 330 CFM.
> See the attached chart.
>
> Assume it is two 2 inch intake pipes so area would be 6.28 square
inches
> or .0436 square feet. Speed going in would then be 7,568 feet per
minute
> or 126 feet per second or 185 MPH going in.
>
> Coming out it would be 2160/560 x 126 FPS or 486 FPS.
>
> A turbine generates max HP when the blade velocity is half the
> flow velocity. That is because the turbine torque is max at zero
RPM and
> zero at max flow velocity when the flow and the blade are both going
> the same speed. HP is the product of torque times RPM. See the
attached
> chart.
>
> So size the turbine so the blades are going 243 FPS or 165 MPH.
>
> I'll leave the turbine diameter as an exercise for the student :)
>
> You can speed up the air coming out by necking the output pipe
area down
> (at the expense of slight back pressure) and slow the air down by
> diverging
> the pipe area. Also you can use a variable nozzle like modern turbo
> chargers
> to tailor the best turbine HP to the e-shaft RPM and the turbine
> diameter.
>
> Check my arithmetic and physics. I could be wrong.
>
> Paul Lamar ...No rotor no motor.
>
> Paul,
>
> In the gas law Volume is inversely proportional to the temperature.
>
> PV=nRT
>
> or
>
> (P1 x V1) / T1 = (P2 x V2) / T2
>
> with a constant pressure
>
> V1 / T1 = V2 / T2 or (V1 x T2) / T1 = V2
>
> Joel
> I had (V1 x T1)/T2 = V2 My mistake.
>
> I should have known that is what happens when you skip steps :)
>
> Thanks for catching that Joel
>
>
> Paul Lamar ...No rotor no motor.
Paul,
Mass flow out is higher because of the products of combustion.
You are adding fuel in the engine.
Bill Schertz
Thanks Bill.
True but it is 14 pounds of air to one pound of fuel.
When fully leaned it could be 18 pounds of air to one pound of fuel.
I did not consider that significant when determining the rough diameter
of the turbine.
--
Paul Lamar ...No rotor no motor.
I guess you could boil it down to three main variables- exhaust
diameter,(speed of exhaust flow versus cross-section of flow area),
Turbine speed/diameter, and whether or not the turbine ought to be geared.
I would think that in the interests of simplicity and probably weight, a
direct drive turbine would be desirable.
Well, it would be great if someone had the resources to test various
turbine sizes and exhaust diameters for a rotary running at a standard
RPM, say 6500. Anyone know of a multi-millionare who's looking to
bankroll some TC research?
Brian Trubee
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