12 b

The air is flowing over the rotor face  from left to right or
maybe from right to left.

The question is: where is the center of pressure?

That will change the lever arm length applying  torque to
the e-shaft.

On a wing the pressure is reduced as the airflows over the wing?

What is the real value of the pressure on the face of the rotor.

In a piston engine there is no doubt that the center of pressure
is in the center of the piston because no airflow crosses the top
of the piston.

IMHO until someone figures out how to survey and measure and
record the instantaneous pressures on the face of rotor in a
grid pattern I don't think we will know the answers

Paul Lamar


Apples and oranges is it not  ?

   The wing is operating in free air whereas the rotor chamber, the side plates, the ports and the moving rotor itself all interact and probably far faster than the thick, ooey, gooey air could return to a free state after being disturbed.

   John Rogi

   I don't agree. That is the only difference in a Wankel and a piston.
   If fact the air velocity (squish flow) over the top of the curved rotor is important
   relative to a point on the surface of the rotor. At low RPM's the air velocity is highest
   where the BSFC is the worst. At high RPM's the surface of the rotor is probably moving
   as fast as the air.  That is where the BSFC is the best.

   Paul Lamar


   "On a wing the pressure is reduced as the air  flows over the wing?"


"At high RPM's the surface of the rotor is probably moving as fast as the air."

So isn't the rotor stalled ?
At the point of a stall the center of pressure shifts aft but if the relative airflow is so low is there a center of pressure aerodynamically speaking ?

John Rogi

No it is not "stalled" It is now zero velocity relative to the surface of the rotor. Stall is well defined
for wings but in this case it does not apply.

Air has mass. Air has inertia.  Air has adhesion. The air molecules adjacent to
the rotor housing surface is not moving relative to the rotor housing. They are
adhered.  The air molecules adjacent to the rotor surface is not moving relative
to the rotor surface. They are also adhered. However the mass of the air between
the two surfaces is being affected by their relative motion due to the
adhesion between air molecules.

Just like the bottom of your car at speed the air pressure is chaotic and complex.
The car is the rotor surface and the road is the rotor housing surface.
This is a fair analogy with the rotary combustion chamber.

As your car speeds up and slows down the situation changes.

However I know for a fact that the center of pressure under the car moves forward at high
speeds causing lift on the nose. I became famous for knowing that :-). I wrote Tech papers and
magazine articles about it in the late 60's and early 70's.

Aerodynamics & The Group Seven Racing Car by Paul Lamar
Presented at the AIAA Symposium on The Aerodynamics
of Sports & Competition Automobiles
(Research I did while at Chaparral Cars.)
April 20 1968

http://www.rotaryeng.net/new-art-list.html

The situation is different in a rotary as there is no new air coming in at the leading edge
of the rotor.

We need to find out where that center of pressure is at all RPM's. It is quite obvious that
the torque generated per pound of fuel burned is changing as a function of RPM.

The piston engine does not do that. The only difference between a piston engine combustion
chamber and a rotary combustion is this air flow/pressure phenomena. Why does the rotary not generate
the same amount of torque for the same amount of fuel burned at low RPM. It is quite obvious there
is something different going on due to the moving combustion chamber. That is all it can be.

Paul Lamar


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