> 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.
Thanks for all of the input.
I am guessing that this experiment will require a few iterations of
design to make it work effectively. The trick is to figure out how to
do the iterations cheaply...
Along those lines, I think it might make sense to build the first TC's
driving a simple/cheap dyno instead of direct driving the e-shaft. If
everything is working well we might expect to get as much as 50hp from
the TC from a p-port 13b? I've got a buddy that worked for a locomotive
manufacturer. We'll have to talk about how expensive a 50hp alternator
would be..
Matt-
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