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Sleeve Valves vs. Opposed Pistons


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#51 fredric21

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Posted 28 October 2015 - 13:52

Manolis.  You claim that there is no force acting on the bearings of your rotary valve.  Although I misunderstood the layout of the valve initially and assumed side to side forces, (which was an error on my part), I see instead a variable axial force when gas pressure acts upon the exposed faces of the assembly within the combustion chamber.   There is simply no way of avoiding gas pressures acting upon any movable device within a combustion chamber, as there is always some part of the device exposed.



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#52 gruntguru

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Posted 29 October 2015 - 00:26

The entire rotary valve is external to the combustion chamber - except for the two vertical windows which each apply an opposing axial force to the valve.



#53 manolis

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Posted 29 October 2015 - 05:48

Hello Fredric21

You write:
"I see instead a variable axial force when gas pressure acts upon the exposed faces of the assembly within the combustion chamber."


Along with Gruntgugu’s explanation (thanks Gruntguru), you can also think about the side forces based on the geometrical "symmetry".


Take the normal to the rotation axis of the rotary valve, plane P, that bisects both, the rotary valve and the cavity / chamber.

The two chamber ports (windows) are symmetrical about the plane P.

The pressure forces acting, through the chamber ports, onto the exposed areas of the two oppositely arranged fronts of the PatRoVa rotary valve cancel each other.

It is a matter of symmetry: the two directions along the rotation axis of the rotary valve (the one towards the timing sprocket, the other at the opposite direction)

PatRoVa_Prot_Ster1.jpg

are equivalent (there is no dominant axial direction).

Can you say which is the direction (the one towards the timing sprocket or the opposite) of the unbalanced axial force?

(The photo is stereoscopic; there are instructions on how to see stereoscopically at http://www.pattakon....Stereoscopy.htm )



Regarding the combustion chamber shape, the substantially central location of the spark plug (very close to the greater part of the compressed gas)

PatRoVa_cavity.gif

is another characteristic of the PatRoVa relative to other rotary valve arrangements wherein the rotary valve cannot help displacing the spark plug aside, near the cylinder wall.

Take a look at the shape of the combustion chamber of a giant marine low-speed 2-stroke (the most fuel efficient engines today):

MANs35.gif

Think of the height reduction (one of the worst issues of these engines) if the exhaust poppet valve is replaced by a PatRoVa 2-stroke rotary valve.
Think also the easiness (i.e. power requirement) for the driving of such a “zero total force” rotary valve, for instance by a small electric motor electronically controlled.



Let me put here a couple of interesting “problems” for discussion.

Suppose that the rotary valve and the cavity on the cylinder head are both made of steel or of spheroidal graphite iron.

1. Take 1ton (2,200lb) force acting on each oppositely arranged front through the big diameter (say of 10cm2 section area) and short (say 25.4mm / 1’’) hub /shaft.
For simplicity forget the bending loads.
The tension load causes an extension of the hub (i.e. an increase of the distance between the two oppositely acting fronts) of about 0.001mm (one micron).

2. Take 100 degrees Celsius (180 F) temperature difference between the PatRoVa rotary valve and the part of the cylinder head between the two oppositely arranged fronts (i.e. the cavity).
Such a temperature difference causes a 0.03mm change in the distance between the two oppositely arranged fronts (i.e. 0.015mm per side).

Thanks
Manolis Pattakos

Edited by manolis, 29 October 2015 - 06:07.


#54 bigleagueslider

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Posted 30 October 2015 - 03:43

Manolis.  You claim that there is no force acting on the bearings of your rotary valve.  Although I misunderstood the layout of the valve initially and assumed side to side forces, (which was an error on my part), I see instead a variable axial force when gas pressure acts upon the exposed faces of the assembly within the combustion chamber.   There is simply no way of avoiding gas pressures acting upon any movable device within a combustion chamber, as there is always some part of the device exposed.

I would agree. When either of the ports are open, there will be some amount of net axial force resulting from gas pressures.

 

I also don't see how the valve as described can provide an effective gas seal under all operating conditions. To function reliably and provide the necessary durability that a modern recip engine requires, some form of gas seal is necessary. And these gas seals would add a significant amount of friction loss. If you consider the gas pressure force acting on all the engine's valve seals at any given instant, the radius about the valve axis the pressure force is applied, the sliding coefficient of friction at each seal contact, and the rotational speed of the valves, there is a serious amount of friction involved. The nice thing about conventional cam/spring actuated poppet valves is that there is no friction loss created when the valves are closed, and they provide a very effective gas seal when seated.



#55 gruntguru

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Posted 30 October 2015 - 05:19

Both ports open simultaneously - forces are balanced.



#56 manolis

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Posted 30 October 2015 - 11:20

Hello BigLeagueSlider.

The following animation explains the full symmetry of the PatRoVa rotary valve:

PatRoVa_4viewpoints.gif

The labels on the cover help in understanding which side you see.

The rotary valve rotates in steps of 18 degrees (20 steps / slides in total).

The big opening on the cover is wherein the intake manifold ends.

The two big circular openings on the cover sides are wherein the roller bearings, that support the rotary valv,e are mounted in.

The small oval hole on the cover is for the spark plug.

The two “kidney shaped” windows at the sides of the cover are wherein the exhaust manifold ends.

As you see at left and right, both "exhaust ports" open simultanuously and close simultanuously ("open" with the meaning that the chamber, through the chamber ports, starts communicating with the exhaust manifold)

Similarly, both "intake ports" open simultanuously and close simultanuously.


The following animation shows “from around” the same cylinder head exploded:

PatRoVa_explode_around.gif

The two ports (chamber ports) at the sides of the red cylinderhead are both for the exhaust and for the intake. First they align with the exhaust ports of the blue rotary valve and then with the intake ports of the blue rotary valve.



Regarding the sealing:

Quote from http://ralphwatson.s...net/rotary.html

“With great, but what turned out to be misguided enthusiasm, I built a model engine based on the Aspin design, which incorporated a cone type valve the same diameter as the cylinder bore, rotating in the cylinder head. The combustion chamber was contained within the rotary valve, which rotated to line up in turn with the spark plug, exhaust port and inlet port.

Full combustion pressure was applied to the valve, forcing it into the taper of its conical seat with the object of ensuring a good seal, but this arrangement could result in the valve seizing in the head due to lack of clearance and lubrication. In order to counter this, the Aspin design incorporated a roller thrust bearing on the valve stem.

I used the same arrangement but could not attain an adjustment whereby the bearing took the load and a satisfactory seal was achieved. When adjusted so that load was on the bearing, the seal leaked and the engine had poor compression and would not run. With load on the cone the valve would seize. After suffering much frustration with broken drive shafts and stripped gears, the engine was eventually run for short periods with load on the cone, thanks to a copious supply of castor oil. This was supplied under pressure to the valve face, by means of a hand pump. My goal of fitting the engine into a model hydroplane came to naught and George Bolt and company remained unopposed at the model pond.

However I was able to test the engine running against a brake and it recorded 1/8 h.p. at 8,000 r.p.m., which was a disappointment when related to the figures quoted in the article which had inspired my efforts.

Many years later the story came out that the Aspin engine was tested by the motorcycle manufacturers Velocette, who found that it produced only half the horsepower claimed, the suggestion being that the original testing had been carried out with a wrongly calibrated tachometer.”

End of quote.


Think the difference between the Aspin rotary valve and the PatRoVa rotary valve.

In the Aspin engine the gas pressure in the cylinder causes the same load onto the Aspin rotary valve and on the piston crown.
Think: are there materials and bearings capable to keep the same tiny clearance (say 0.001’’ / 0.0254mm) between the rotary valve and its "basis" with and without gas pressure in the cylinder?

In the PatRoVa rotary valve, with and without gas pressure into the cylinder, the total force is zero allowing the same tiny clearance to be maintained at all conditions. And without contact the friction is eliminated.

Think also of the piston rings of the conventional engines and the gaps at their ends. Do the piston rings achieve perfect sealing? No. But their leakage (blow-by) is small and gets smaller at higher revs.

Thanks
Manolis Pattakos

Edited by manolis, 30 October 2015 - 12:33.


#57 Lee Nicolle

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Posted 30 October 2015 - 11:33

I would agree. When either of the ports are open, there will be some amount of net axial force resulting from gas pressures.

 

I also don't see how the valve as described can provide an effective gas seal under all operating conditions. To function reliably and provide the necessary durability that a modern recip engine requires, some form of gas seal is necessary. And these gas seals would add a significant amount of friction loss. If you consider the gas pressure force acting on all the engine's valve seals at any given instant, the radius about the valve axis the pressure force is applied, the sliding coefficient of friction at each seal contact, and the rotational speed of the valves, there is a serious amount of friction involved. The nice thing about conventional cam/spring actuated poppet valves is that there is no friction loss created when the valves are closed, and they provide a very effective gas seal when seated.

The bane of that style of engine forever. Which I feel will never be resolved too any long term satisfaction. How many years have Mazda persisted with the rotary, and it still is not great. For a valve seal friction and combustables [fuel] residue will always be a problem.

I agree a poppet valve will always be a restriction BUT it is simple and the valve on the seat effectively seals itself, usually for about 300000km. Sometimes 3 even 4 times that.

Though compressing those valve springs still requires quite a deal of energy. And cam people, engine designers are still in a quest to improve this. Though in the quest for smaller and lighter and fuel efficiency they are still too a degree chasing their tail. They will probably come to the conclusion that small is not best, larger is more efficient. Both in physical size and capacity.

Especially as the cars them selves are getting bigger, fatter and far heavier with all the whistles and bells and safety equipment desired/ required these days. Kind of self defeating really.



#58 manolis

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Posted 31 October 2015 - 10:07

Hello

In the last two animations of the PatRoVa (post #56), the colors have been changed.
The exhaust passageways in the rotary valve are yellow, the intake passageways in the rotary valve are green.
See the overlap through the bottom of the combustion chamber / cavity (yellow and green are both open).


Hello Lee Nicolle.

Despite its problems, the Bishop rotary valve (supported by Illmor, which were supported by Mercedes) achieved on the dyno 10% more power than the F1 poppet valve engines.
The response from F1 was to change the rules allowing only engines having two intake poppet valves and two exhaust poppet valves per cylinder!


Wankel:

According Mazda (Tokyo Motor Show 2015) the Wankel Rotary (RX-Vision SkyActive-R) will be back in mass production in 2017 (it will be combined with an electric motor and batteries):

mazda-rx-vision-concept.jpg

The Wankel Rotary cannot help burning lubricant. Very bad for the emissions, bad for the running cost.

Without contact between the oppositely arranged fronts and their respective chamber lips, the PatRoVa rotary valve needs not lubrication in the cylinder head (Coates / CSRV explains at http://www.coateseng...srv-system.html how important this is).


PatRoVa rotary valve:

Have you read the rough calculations of the effect of the pressure forces and of the temperature differences on the clearance of the PatRoVa rotary valve at the end of the post #53?

The absence of pressure forces on the bearings of the PatRoVa rotary valve (zero total force characteristic) together with its more than stiff hub/shaft connecting the two disks (a 1ton force causes an extension of only 1 micron) and together with the small distance (about 1’’, 25.4mm) between the oppositely arranged fronts (that keeps the thermal expansion small) put it in a new / different class of rotary valves.

Do you know another rotary valve having all these characteristics?

Just think the reduction on the ownership cost, on the maintenance cost, on the external dimensions and on the complication if the desmodromic cylinder heads of the Ducati Panigale are replaced by PatRoVa cylinder heads:

PatRoVa_Panigale.jpg

Also think the new rev limit and the increase in power such a modification could bring.

Thanks
Manolis Pattakos

#59 fredric21

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Posted 07 November 2015 - 12:30

I can't see the achievement of a successful seal between all vertical faces being possible.  In order to reduce gas leakage a minimal gap must be maintained. Any distortion of any of the faces will introduce leakage and/or extra frictional forces between static and dynamic interfaces.   Distortions are bound to be introduced by differential heat fluxes, pressure differentials, combustion deposits, wear, etc.



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#60 manolis

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Posted 08 November 2015 - 05:59

Hello Fredric21.

You write:
"I can't see the achievement of a successful seal between all vertical faces being possible. In order to reduce gas leakage a minimal gap must be maintained. Any distortion of any of the faces will introduce leakage and/or extra frictional forces between static and dynamic interfaces. Distortions are bound to be introduced by differential heat fluxes, pressure differentials, combustion deposits, wear, etc."


You are right: "In order to reduce gas leakage a minimal gap must be maintained."

The question turns to: "Can the PatRoVa rotary valve maintain the required minimal gap?"


Quote from http://www.pattakon....akonPatRoVa.htm

"Sealing

Considering the flat fronts and the flat lips as parts of spheres (or cylinders) of infinite diameter, the skilled-in-the-art knows how the state-of-the-art "spherical / cylindrical rotary valve sealing technology" is applicable in the case of the PatRoVa rotary valve.

A more ambitious idea is to exploit the inherent characteristics of the PatRoVa rotary valve and seal the combustion chamber without using conventional sealing means.

For the sealing between the pair of flat-fronts and their respective chamber-port-lips only the one of the three dimensions is significant: that one along the rotation axis of the rotary valve (i.e. the distance between the two disks and the width of the combustion chamber); the displacement of the rotary valve along the other two dimensions does not affect the sealing. And because the heavy forces applied on the flat fronts balance one another "internally", such a displacement is easy to be realized and to be controlled (Variable Valve Actuation).
In comparison, the slightest displacement, at any direction, of a spherical rotary valve changes significantly the sealing quality.

The sealing is tolerant to deformations of the cylinder head because, as before, only the one of the three dimensions really matters; significant deformations of the chamber along the other two dimensions do not affect the sealing.
Between its chamber ports the chamber (i.e. the cavity into the cylinder head) is like an open ring (a thin open ring); if the diameter of the ring is for some reason increased (due to the high pressure into the chamber, for instance, or due to the temperature etc) it makes no harm to the sealing. The pressure in the chamber cannot essentially affect the dimension of the "ring" along the rotation axis of the rotary valve.
Besides, the lower part of the chamber is "enclosed" and is strongly supported by the lower end of the cylinder head (which is stiff as being the roof of the cylinder).

With the distance between the chamber-port-lips being small, proportionally small is the effect on the sealing quality of the temperature difference between the rotary valve and the chamber walls."

End of quote.


Besides the previous, this drawing:

PatRoVa_comp.gif

combined with the following two photos:

PatRoVa_photo11F.jpg

open_end_wrench.jpg

explains how difficult is to maintain the required minimal gap in the state-of-the-art rotary valves and how easy, in comparison, is to maintain the required minimal gap with the PatRoVa rotary valve architecture.


A reasonable "solution" is the introduction of sealing means between the rotary valve and the cylinder port.
To cure the side effects of such a "solution" (friction, wear, lubrication, reliability etc) proved in practice more difficult than the original problem.


Quote from the post #53:

"Suppose that the rotary valve and the cavity on the cylinder head are both made of steel or of spheroidal graphite iron.

1. Take 1ton (2,200lb) force acting on each oppositely arranged front through the big diameter (say of 10cm2 section area) and short (say 25.4mm / 1’’) hub /shaft.
For simplicity forget the bending loads.
The tension load causes an extension of the hub (i.e. an increase of the distance between the two oppositely acting fronts) of about 0.001mm (one micron).

2. Take 100 degrees Celsius (180 F) temperature difference between the PatRoVa rotary valve and the part of the cylinder head between the two oppositely arranged fronts (i.e. the cavity).
Such a temperature difference causes a 0.03mm change in the distance between the two oppositely arranged fronts (i.e. 0.015mm per side)."

End of quote


As you see, the architecture of the PatRoVa rotary valve is anything but vulnerable "to distortions introduced by differential heat fluxes and pressure differentials".

To further reduce the distortion introduced by differential heat fluxes, a future option is to use INVAR, or other low coefficient of thermal expansion alloy, for the rotary valve and the cavity.


In the racing version (stereoscopic view):

PatRoVa_racing_STE.gif

besides the maximized port areas and the "conventional shape" of the combustion chamber, you can also have inlet manifolds at both sides of the cylinder head cover (at the "front" and the "back" sides of the engine):

PatRoVa_racing_symmetry.gif

allowing thinner disks at the ends of the stiff hub/shaft to be used, and further reducing the contact of the hot exhaust gas with the PatRoVa rotary valve.

In comparison think the path (or better the labyrinth) the exhaust gas follows in a spherical rotary valve, think also the inner walls of the spherical rotary valve the hot exhaust gas comes in contact.

Reasonable question: How close to "spherical" a spherical rotary valve remains at operation?

Even if the sealing quality is not as good as in the following more conventional PatRoVa rotary valve cylinder head, isn’t the breathing efficiency (flow capacity) of the previous racing version top?

PatRoVa_glass_STE.gif

Thanks
Manolis Pattakos