shainiac

So, I've spent some time in SolidWorks modeling a rotor housing, rotor and e-shaft as accurately as I can (I only have a 0-1" mic and a pair of cheap digi calipers). I have a working model that has a 'similar' geometry to what it should look like. The rotor housing was tough. I was having the trouble getting the trochoid shape, but ended up using two cemicircles and replicating the curve in between.

Here is my question:

I am using the MFR peripheral port timing for intake as an example.

IO 86° BTDC

IC 75° ABDC



What I'm confused about is the fact that I cant make out how the intake is open. Maybe my model is off enough that I can't see the subtleties of how it opens. It's pretty obvious to see how the intake closes, as the apex seal passes over where the port would be.



Ive attached pictures to help clarify.

The first is Intake opening, second is closing.

Lynn E. Hanover

The rotary takes 1080 degrees to complete a cycle. That would be rotor face “A” at TDC then a full revolution and back at TDC again. During this cycle rotor face “B” and rotor face “C” will have been to that same TDC and have fired as well. So you have 3 crank rotations to get one rotor revolution.



Further confusion is produced by the 2 sets of TDC and BDC. Maximum chamber volume at both

the top and bottom of the engine are BDCs. Minimum chamber volume on the left and right sides of the engine are both TDCs.



In this picture the rotor is at BDC on the intake stroke. Note that the massive bridge port that will close

at 85 degrees after BDC.



Note also that timing events are called out from the nearest TDC or BDC. This is to keep the numbers small.



In the periphery port engine the intake port is valved by the apex seal rather than the side of the rotor.

In the side port engine then the intake flow stops for a bit when the port is covered by the rotor. Similar to a piston engine.



Not so in the periphery port engine. The port never actually closes. The apex seal crossing the port just directs intake flow into the closing intake chamber or into the overlap with the exhaust port. So, it is more turbine like than Otto cycle like. The same situation for the exhaust port but reduced a bit by the ports shorter open period. However, the overlap period is substantial.



As you can see in the picture, to close the intake port at 85 degrees, the rotor would have to be at a noticeable angle. About this same angle should be in the second drawing, in the opposite direction to show closing.



Lynn E. Hanover

shainiac

Hrm, I have the drawing constrained to have the rotor rotate about the e-shaft a a 1:3 ratio, so I believe it is oriented correctly, but I am still a bit confused about TDC and BDC. Are you saying there is a TDC and BDC for intake and exhaust, and that they are different? I assumed it was relative to the crank.



I didn't do a very good job explaining it, the leading edge of the "arm" I drew off of the e-shaft is there to rotate the assembly and give a reference for measuring the angle. The "blocks" (2 at the top and 2 at the bottom) serve as what I thought was TDC and BDC. Each set shares an side oriented on the y-axis, at 90* and 270*. Their shape is arbitrary, it just mattered that they have one face on the axis to find a reference to the crank.



What I assumed to be correct was that when the front rotor lobe was up and at 90*, that was TDC. I guess I should have thought about it as a piston engine, TDC having minimum volume and BDC having maximum volume.



Maybe I am going about this wrong and should have asked this in the first place. Is TDC/BDC referenced from the rotor or the e-shaft. Also, where is TDC and BDC located(intake and exhaust if that's relative)



I apologize for the rambling. The fact that I chose to start this project during finals week was a bad idea, but I can't get it out of my head



-Alex

shainiac

So, I think I wrapped my head around some of this.I'll try to explain and attach pictures to go with my reasoning.

If the e-shaft lobe is at 9 o'clock, The intake is at TDC. Minimum volume.

If the e-shaft lobe is at 6 o'clock, The intake is at BDC, Maximum volume.

If the e-shaft lobe is at 3 o'clock, The exhaust is at TDC, Minimum volume.

If the e-shaft lobe is at 12 o'clock, The exhaust is at BDC, Maximum volume.

Each cycle takes 270* of crank rotation.

1080* of crank rotation for 360* of rotor rotation.

1080/270=4, 4 stroke. Make since?



Here are picutes of TDC and BDC of both the intake and exhaust cycles.

Also attached, opening and closing pictures for the MFR Peripheral Port, IO 86° BTDC IC 75° ABDC

I measured the distance between the opening and closing points of the PP. 43mm. Sounds reasonable.

If anyone's interested, I can try modeling side ports.



-Alex

Lynn E. Hanover

Sort of.............Perhaps we should follow a rotor face around the cycle. And add the ports and the spark plugs. I tried to change one of your drawings in the MS paint that came in MS-7 and it sucks real bad. Much older versions work great.



Here we go. By the time rotor face "A" is at TDC in overlap, (Left in the drawing)the intake port has been open for some time

and is connected to the fully open exhaust port for some number of degrees. The intake cycle starts then well before TDC overlap when the upper apex seal in the drawing exposes the slightest amount of the intake port. The compression of the new charge starts only when the bottom apex seal in the TDC picture completely closes off the top of the intake port well after BDC intake cycle.



This is always at the top of the engine. The rotor then compresses the mixture on around toward TDC on the plugs side. Well before TDC there the plugs fire. Either leading first then trailing or together in racers (no Split). Also in highly boosted engines (no Split). This is BTDC (ignition advance) as much as

44 degrees down to as much as 10 degrees after TDC for highly boosted engines. The object here is to get

maximum cylinder pressure at about 50 degrees after TDC. Or 18 to 20 degrees in a piston engine.



So, the power stroke has been started well before TDC, but pressure generated there subtracts from output as does the work lost in the compression cycle. Only pressure available after TDC can be converted to work.



So the power stroke begins at TDC (In front of the plugs)and is over before BDC just as in the piston engine. BDC in the exhaust stroke is always on the bottom of the engine. With no valve to slow the escape of exhaust gasses, they exit above the speed of sound. With a well designed header and collector

this velocity can be maintained right to the muffler. The speeed drops to subsonic in the muffler dropping imense energy in the form of sound and heat. This is why the rotary responds well to turbo charging. (much excess energy left in the exhaust flow). One product of this flow velocity is that most of the gasses are gone before the exhaust port is fully open, and this creates a partial vacuum during the overlap period (Both sides of TDC overlap) and this helps maintain high intake flow velocity.



I think that if you draw in the ports and the plugs the picture could be much improved. The engine is an Otto cycle (4 stroke) just like a 4 stroke piston engine.



Because there are no valves, the intake runner length and diameter, and exhaust header diameter and length as well as collector design become critical. It tunes just like a 2 stroke dirt bike engine.



Maximum practical HP is 400 HP per rotor for under one minute.



Any question, anytime.



Lynn E. Hanover

shainiac

I was having a bit of trouble finding a bit of trouble finding specifics on the locations of the spark plugs relative to TDC. I measured a S5 rotor housing and saw that the trailing plug hole was rougly 1.25" above intake TDC and the leading roughly 1" below TDC. Included is a picture of a housing with the correct ports and my guestimate of the plug locations.



Also, I drew out a few different port openings and saw something interesting. The later the intake closes, the heighth of the port goes up almost exponentially. The adding an extra 5* of intake closing and moving the opening time 6* LATER (so effectively having only 1* LESS duration), the final port was nearly 3/8 of an inch taller! This is because of the curvature of the top half of the rotor housing. Knowing this know, the actual size of the port can be a bit deceiving. A monstrously tall port can have a similar duration with fairly similar port timing to a relatively small port that is slightly lower in the housing.



Here are some screen shots.

The first port:

IO 86° BTDC

IC 75° ABDC

Duration: 341*

Port height: 1.675



Second port:

IO 80° BTDC

IC 80° ABDC

Duration: 340*

Port height: 2.031



As you can see, the second port has LESS duration, but is significantly larger in size!



NOTE: I pasted the wrong durations in the picture. The correct durations are posted above.

shainiac

This was a pain in the ***, but I was able to loft the port shape into what would be a 2" OD tube. I also did the same for the exhaust port shape and the dimensions of the stock exhaust sleeve. This was kind of awkward to do since the ports would have to be hand blended, but you get the picture. The rotor is at BDC.

shainiac

I was able to get a copy of SAE 900032 and I thought I'd post it for those interested.

Unfortunately they are separate jpegs.

Here are pages 1-6

shainiac

7-12

Liborek

I´ve been looking for this paper for long time, excelent work, much appreciated that you posted it!