Powersport Aviation

[Rotary10-RV]

Originally Posted by cjensen

Hey Bill,

Those were the numbers I was referring to, but it seems like dragging names into threads can cause problems. Anyway, thanks for posting that. You are right about the high RPM contentness in the rotary.

What a lot of people don't realize (but many do) is that the rotary turning 6000 rpm is the rpm at the eccentric shaft. The rotors are only turning 2000 rpm. The e-shaft is a solid piece of balanced metal turing a very small radius. This has probably been posted here before, but I can't remember.

The Mistral is another outstanding package, and I am hot on that one too! There PSRU is the perfect solution, being able to use a hydraulic C/S prop. Pricey though, even more so than Powersport. Does anyone know if there FWF package comes with an engine mount?

Chad, I went back to this post to mention that several people have been working on taking power off the rotor for a built in 3:1 RPM reduction!
Bill Jepson

[mlw450802]

Originally Posted by Rotary10-RV

Chad, I went back to this post to mention that several people have been working on taking power off the rotor for a built in 3:1 RPM reduction!
Bill Jepson

I really enjoy mechanism design and love to see "new" components.
This connection to the rotor will be impressive to me for sure!
The rotor orbits at the E shaft rotational speed and rotates at one third the E shaft speed.
The rotor rotationally accelerates and decelerates significantly on its path around the housing and I believe obtaining a connection to it that will result in a smooth rotational output for a propeller will be an interesting study.
-mike

[Rotary10-RV]

Originally Posted by mlw450802

I really enjoy mechanism design and love to see "new" components.
This connection to the rotor will be impressive to me for sure!
The rotor orbits at the E shaft rotational speed and rotates at one third the E shaft speed.
The rotor rotationally accelerates and decelerates significantly on its path around the housing and I believe obtaining a connection to it that will result in a smooth rotational output for a propeller will be an interesting study.
-mike

Mike the rotor doesn't accellerate and decellerate, it orbits a perfectly circular ORBIT. The rotor rotates and orbits which causes the variable area for the otto-cycle. The only accelleration and decelleration is with the overall engine speed. It is really amazing and hard to wrap your head around. Felix had several 5 chamber designs and one similar to the current one in which the chamber spun and e-shaft was fixed like a old radial! I believe that it was an NSU engineer that helped Wankel "finish" the rotary into the configuration we have today.
Bill Jepson

[mlw450802]

Originally Posted by Rotary10-RV

Mike the rotor doesn't accellerate and decellerate, it orbits a perfectly circular ORBIT. The rotor rotates and orbits which causes the variable area for the otto-cycle. The only accelleration and decelleration is with the overall engine speed. It is really amazing and hard to wrap your head around. Felix had several 5 chamber designs and one similar to the current one in which the chamber spun and e-shaft was fixed like a old radial! I believe that it was an NSU engineer that helped Wankel "finish" the rotary into the configuration we have today.
Bill Jepson

I think maybe I have a reference frame issue here. The rotor certainly orbits in a circular path and if your reference is from the center of that orbit, its velocity is constant and therefore its acceleration is zero. But, if your reference is the housing, then certainly there is an acceleration component.

Use an automobile tire as an easy to understand example of my confusion. From the axle or spindle reference frame, there is no acceleration of the tire at constant vehicle speed but, from the road's perspective, the tire stops at the contact patch and then accelerates to twice vehicle speed at the top and back to zero again as it completes one revolution.

I go back to my earlier post, it will be interesting to me to see a mechanism that can take the wankel rotor's rotational velocity for power output while somehow ignoring its orbiting velocity (and accelerations from my reference frame)

Not a naysayer, just an interested bystander.

[cobra]

Rotary10-
I actually agree with you on this. My assumptions were based on looking at the motor's volumetric flow- that a certain amount of fuel/air physically flows thru the engine at a given speed, defined mostly by the "pistons" displacement, the number of times it refills (rpm), and the fuel/air mixture which were assumed to be constants for comparison sake (not in the real world where mechanical systems are imperfect).

Looking back in retrospect, I realise that I overlooked two things. 1.) while it is true that the rotary fires on each rotation of the rotor, it only fires on every third rotation of the crankshaft, and crankshaft rotation is what is normally measured. Therefore the correct formula should use the factor rpm/3, not "rpm" alone for the rotary.

2.) I failed to consder the pressure driving the fuel/air mix into the intake manifold- basically assumed everything happens at ambient pressure/temp with no restrictions to flow. That is incorrect as you indicated, except at full throttle.

I agree with your assessment the the engine is most efficient at the torque peak- the technical term (I believe) is the maximum abdiabatic efficiency point, where the combustion chamber pressure peaks and the engine uses the every bit of air that it can muster. With turbocharging, the rpm range at that point where we have to tune most carefully, because it is the point where detonation control is the most critical, and I believe, where the heat generation peaks as well.

I dont know about the lean burn part of your comment, but it makes sense to me. The large surface area of the piston/combustion chamber should be less prone to detonation; heat generaton and (related) detonation is really what determines how lean you can run safely.

[rv6ejguy]

Originally Posted by cobra

I agree with your assessment the the engine is most efficient at the torque peak- the technical term (I believe) is the maximum abdiabatic efficiency point, where the combustion chamber pressure peaks and the engine uses the every bit of air that it can muster. With turbocharging, the rpm range at that point where we have to tune most carefully, because it is the point where detonation control is the most critical, and I believe, where the heat generation peaks as well.

I dont know about the lean burn part of your comment, but it makes sense to me. The large surface area of the piston/combustion chamber should be less prone to detonation; heat generaton and (related) detonation is really what determines how lean you can run safely.

Torque peak actually occurs at peak volumetric efficiency and peak chamber pressure. On either side of this rpm, VE and CP are lower. Max heat generation is at peak hp rpm where the maximum amount of heat is being liberated per unit time. Detonation is most likely to happen at or near peak torque however this is dependent on ignition advance to a large degree. The Wankel does have better anti-detonation qualities than most piston engines due to it's high surface to volume ratio chamber but it can certainly still detonate. John Slade's turbo 13B has demonstrated operation up to 46 inches MAP on 87 octane auto gas which is quite impressive.

Recent testing has revealed than the mixture strength has far less to do with detonation tendecies than previously thought or commonly believed. In cruise conditions, the lean limit is usually defined by mixture distribution between chambers, mixture homogeny, spark energy available and mixture turbulence. Engines which have these items optimised are capable of running LOP smoothly and efficiently.

[gmcjetpilot]

All this info is good, and may be technically and theoretically correct, how fast the rotor turns, the speed of the combustion flame front or the angle of the dangle, and it means nothing, the proof is in the number's (real world performance, side-by-side against a Lycoming powered RV).

Right now the only reasonable side-by-side numbers is from the RVator. And the only big negative was the fuel burn. Now bring in a representative, Real World Solution 13B or other new rotary engine company (all I think use Mazda cores) to flight test against a Lycoming.

When someone says I burned X on a X-C flight, that is great info, but with out a long list of supporting data to back up the MPG it means nothing. My 150HP Lyc RV-4 from Seattle To Phoenix was doing 265 MPH at 6.5 GAL an hour! (pause, wait) and could have made it direct (1100 sm) with no stops (wait, pause). True, but missing some info. I was at 12,500' and had a 70kt tail wind. I also would have burned 28 gal with 32 gals tanks (31 usable), so technically it would have been possible (but not wise). I passed my normal fuel stop (Redding/Red Bluff, Ca) and landed in Bishop CA in 3 hours (about 724sm). Obviously with out the fact I had 70kts of tail wind the data is not usable. (If I would have had larger tanks by 8 gals I would have went non-stop direct to PHX.) True story, not many times you get tail winds like this.

BTW, a Lycoming can also run LEAN of peak (if fuel injected).

Cheers George

[Rotary10-RV]

BTW, a Lycoming can also run LEAN of peak (if fuel injected).

Cheers George[/quote]

George, What we were making a point about is that the rotary can run lean of peak more safely than a piston engine. Any piston engine, Lycs included. The Piper Turbo Meridian was using lean of peak operation to show good fuel numbers and they are now facing a class action suit for failure to make TBO. I am not getting on Piper's case here as I believe most pilots are not well trained on LOP operation. That is I believe LOP failures are pilot induced most of the time. Rotaries are less prone to problem and have proven pretty bulletproof LOP in NA operation. Turbo is also good LOP with the need to preform normal detonation prevention measures like retard at high boost, like any ICE.
Bill Jepson

[mlw450802]

Originally Posted by cobra

...Looking back in retrospect, I realise that I overlooked two things. 1.) while it is true that the rotary fires on each rotation of the rotor, it only fires on every third rotation of the crankshaft, and crankshaft rotation is what is normally measured. Therefore the correct formula should use the factor rpm/3, not "rpm" alone for the rotary.

Here I may be showing my ignorance again on this engine but it looks to me like there are three combustion events per rotor revolution (one for each of the three faces) and therefor one combustion event per crank revolution per rotor.
On the 13B that means two combustion events per crankshaft revolution, one every 180 degrees of crank (e shaft) rotation.

-Mike

[cjensen]

i agree with the LOP operation bill. we deal a lot of malibu/mirages (meridian is the turboprop ), and we see a whole bunch of the mirages not making times because of poor LOP procedures. i have time in both malibu's and mirages, and i still need instruction on how to operate them properly. i just don't feel comfortable running LOP if i'm not absolutely certain that i'm doing it correctly. there's been some printed material circulated recently that states that LOP operation of the TSIO-540 is not recommended anymore. too many people looking for lawsuits, i guess.

anyway, the rotary is superb at LOP operations.

what was this thread about??...the rotary, Powersport...oh yeah.

this has been a great discussion.