Mark Wrathall wrote:
Paul wrote: It is much simpler to do it with a wankel as the engine is
already
rotating at turbine like speeds so no need for gearing between
engine and turbine, unlike the elaborate gearing that is required using
a big old low RPM piston engine. Furthermore there are no exhaust
valves to break up and destroy the turbine on the way out.
The Achilles heel of the R-3350 TC.
Paul, I really don't see this working in this form. With the low mass flow
of an intermittant combustion engine (compared to a gas turbine) you would
have two choices:
1: porting the exhust on the turbine through a single nozzle covering a
fraction of the turbines circumference, or
2: feeding the whole circumference via a scroll.
1.With the exhaust ported onto the turbine at one point, you will have major
durablity issues with the blades due to the 1 per rev thermal shock coupled
to the one per rev mechanical flexing they will see. If you only drive the
turbine wheel through a single nozzle covering a small arc, you also have
aero drag over the rest of the circumference, and large leakage losses. The
disk will be very heavy.
2. You would really need a scroll (given the diameter, probably feeding on
rotor in each side of the scroll( to even out the temp and pressure). For
this the scale here is way off. For the mass flow coming out of a 13B, your
blades length would be miniscule at that radius. Turbine efficiency would be
crap. The disk would still be pretty heavy. Will a scroll even work at that
scale?
What is the mass flow out of a 200hp 13B? What is the diameter of the
flywheel. With that I can do the turbine equations to put some numbers on
this.
My guess on the mass flow is the weight of air and fuel burned:
10 pounds an hour for fuel and at 12:1 mixture ratio 120 pounds an hour
for air. Does that sound about right. Please run 130 pounds an hour
through your program and see what comes out.
Opps! That should be ten GALLONS an hour. So that is 60 pounds
per hour for fuel and 720 pounds for air for a total of 780
pounds per hour mass airflow. That is more like it.
Paul Lamar
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