1700 feet per second. Area of the scroll at a radius of 3.5 inches is
about 2.8 square inches. A/R = .8. Two, 2 inch exhaust pipes would have
an area
of 6.28 square inches total. The gas velocity in the scroll would then
be about 2.2 times the exit velocity from the 2 inch exhaust port.
According to Scientific Design of Exhaust and Intake Systems exhaust gas
velocity
is on the order of 200 to 300 feet per second from a typical four cycle
piston engine.
So exhaust gas velocity in the turbo scroll would then be 450 to 670
feet per second.
Obviously the exhaust gas velocity in the rotary is two
or three times that number or one would get no torque out of the
turbine.
Not in the ball park.
Another possibility is I am off on the diameter of the turbine wheel.
Lets see, a T3 wheel can be 2.319 or 2.559 inches in diameter. Using the
2.559
number that would bring the tip velocity down to 1470 feet per second.
Still not in the ball park.
Vance this is right down your alley. What say you? Where am I going
wrong?
Is the exducer diameter the controlling factor?
How do I figure the exhaust gas velocity knowing the cubic feet of air
per minute going into the engine? (P1 x V1)/T1 = (P2 x V2)/T2 ?
Paul Lamar
If I do (P1 x V1)/T1 = (P2 x V2)/T2 and assume 300 CFM in and 100 F in
with 1600 F out with two 2 inch pipes in and out I get 1800 feet per
second
out which is in the ball park. I can see how that could be 200 HP coming
out of the exhaust pipe.
Wow that exhaust gas is really moving in rotary engines. About
supersonic at those temps. No wonder it eats steel exhaust systems for
lunch.
Check my arithmetic.
Paul Lamar
Volume ratio 300cfm X (1600+460)/(100+460)=1104cfm/60=18.4cfs
2 2in pipes= .0436sq ft vel = 432fps scroll area 2.8 .019sg ft vel 968fps
spouting horsepower about 9 theo jet stream power
Vance
Wow!!! That's more like it Vance. Now that 130,000 RPM makes sense.
Is there a way of calculating the torque on the turbine?
I see I forgot to adjust the velocity for the scroll area.
Thanks a bunch.
Paul Lamar
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