Rotary Valve - The Technical Forum

Posted 06 March 2014 - 09:28

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regarding the sealing, the following were added to the


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 cancel each other "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 between the spherical rotary valve and the port it controls.

The sealing of a disk rotary valve having flat fronts is tolerant to deformations of the cylinder head because, as before, only the one of the three dimensions really matters: that one along the rotation axis of the disk rotary valve; 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; 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) the effect on the sealing is insignificant. The pressure in the chamber cannot essentially affect the width of the ring, i.e. it cannot affect the dimension of the "ring" along the rotation axis of the rotary valve.

The lower part of the chamber is "enclosed" and is strongly supported by the lower end of the cylinder head. With the dimension of the ring shaped chamber (or cavity) among the chamber ports being small along the rotation axis of the disk rotary valve, proportionally small is the effect of the temperature difference between the rotary valve and the chamber walls on the sealing.

The limit of the width of the combustion chamber (i.e. of the width of the cavity into the cylinder head) is set by the diameter of the spark plug (or of the injector). For instance, with a distance of 15mm between the two disks, the expected thermal deformation is six times smaller as compared to the case wherein the two ports were arranged at the sides of an 80mm bore cylinder.



The smaller the distance between the two disks, the less the thermal expansion and the less the stressing expansion, and the less the bending flexing (the major causes affecting the clearance between the flat-fronts and the chamber-port-lips).


Kelpiecross,

the rhythm the valve opens depends on the shape/geometry of the chamber ports and on the shape/geometry of the intake ports. For instance, a trapezoidal form of the valve opening versus the crankshaft angle is easy.
The absence of the "valve stem obstacle" allows more free breathing.
From another viewpoint, if you want a specific valve-area vs crankangle, you can achieve it by selecting the proper shape for the intake, exhaust and chamber ports.
The overlap is substantially different than in a conventional four-valve engine because in the second the intake valves are almost in touch with the exhaust valves. In the PatRoVA, during the overlap the openning area and the closing area are at opposite sides of the combustion chamber (scavenging?)

Thanks
Manolis Pattakos

Gruntguru,regarding the sealing, the following were added to the http://www.pattakon.com web site: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 cancel each other "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 between the spherical rotary valve and the port it controls.The sealing of a disk rotary valve having flat fronts is tolerant to deformations of the cylinder head because, as before, only the one of the three dimensions really matters: that one along the rotation axis of the disk rotary valve; 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; 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) the effect on the sealing is insignificant. The pressure in the chamber cannot essentially affect the width of the ring, i.e. it cannot affect the dimension of the "ring" along the rotation axis of the rotary valve.The lower part of the chamber is "enclosed" and is strongly supported by the lower end of the cylinder head. With the dimension of the ring shaped chamber (or cavity) among the chamber ports being small along the rotation axis of the disk rotary valve, proportionally small is the effect of the temperature difference between the rotary valve and the chamber walls on the sealing.The limit of the width of the combustion chamber (i.e. of the width of the cavity into the cylinder head) is set by the diameter of the spark plug (or of the injector). For instance, with a distance of 15mm between the two disks, the expected thermal deformation is six times smaller as compared to the case wherein the two ports were arranged at the sides of an 80mm bore cylinder.The smaller the distance between the two disks, the less the thermal expansion and the less the stressing expansion, and the less the bending flexing (the major causes affecting the clearance between the flat-fronts and the chamber-port-lips).Kelpiecross,the rhythm the valve opens depends on the shape/geometry of the chamber ports and on the shape/geometry of the intake ports. For instance, a trapezoidal form of the valve opening versus the crankshaft angle is easy.The absence of the "valve stem obstacle" allows more free breathing.From another viewpoint, if you want a specific valve-area vs crankangle, you can achieve it by selecting the proper shape for the intake, exhaust and chamber ports.The overlap is substantially different than in a conventional four-valve engine because in the second the intake valves are almost in touch with the exhaust valves. In the PatRoVA, during the overlap the openning area and the closing area are at opposite sides of the combustion chamber (scavenging?)ThanksManolis Pattakos

Additional reading:
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