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Potential Benefits
of using
The Double Acting / Uniport Valve (Patent #
5,782,215)
With
this proposed design only one port is needed for each cylinder; since
both intake and exhaust gas pass through the same port. This will allow
the designer to change the geometry of the cylinder head to improve
engine performance. Below, I have come up with three changes and
various benefits for each.
First, the Uniport Design allows one
to have more total port area than current practice allows. This is true
for two reasons. First of all the port is used twice and second of all
a single port can fit over the cylinder more efficiently than two or
more can. The extra port area should help long stroke engines improve
volumetric efficiency and decrease pumping losses by aiding flow in
both the intake and exhaust cycles.
The second advantage of
having only a single port is the ability to put it in the center of the
cylinder. I will list some effects this may have on the system and
their apparent benefits to an engine's performance.
2-1) Ports
will no longer be shrouded by the cylinder walls. Reducing this problem
should improve the flow for the intake and exhaust cycles. Again
improving volumetric efficiency and reducing pumping losses.
2-2)
In a four valve head the incoming air from the two different ports
obstructs each other. But with the uniport valve where all the incoming
air comes from the same port this doesn't happen, which allows for a
more efficient filling of the cylinder. Thus this also helps improve
the volumetric efficiency of the engine.
2-3) The port being in
the center will reduce the distance the exhaust gas must travel before
exiting the cylinder especially towards the end of the exhaust cycle.
Normally the pressure builds opposite the exhaust valves increasing
pumping losses, this problem is now reduced. Another effect might be a
reduction in the amount of residual gas.
2-4) Another effect of
being away from the cylinder walls should be less heating of the
incoming air. This should keep the density of the charge higher thus
improving volumetric efficiency. Also this should reduce operating
engine temperatures which would help reduce heat losses.
2-5)
Assuming the burn area is designed around where the ports are then the
burn area is more centralized also. With more of the fuel burning in
the center of the cylinder, less heat is transferred to the cylinder
walls reducing both oil evaporation and heat losses. A better thermal
efficiency should be realized due to this.
2-6) The port being
in the center should help induce tumble action. Once combustion starts
this action should help ignite unburned fuel by mixing it with the
burning gases. The net effect should be better combustion efficiency.
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2-1) The
brown area shows where shrouding occurs on present designs
2-2)
The purple arrows represents predominate flow patterns during the
intake cycles. In the two and four valve systems one can see how flow
can hinder itself.
3-1) The red arrows represent air movement over the squish area during
the latter end of the compression cycle.
The
third advantage is that there is only one poppet valve exposed in the
combustion chamber. So even though one has maintained or increased port
area, exposed valve area would be reduced. For the benefits listed
below, I am assuming a clearance volume to be shaped like a hemisphere.
3-1)
Having less cylinder face area taken by valves allows more low
clearance area, or squish area, which with the action of the piston
helps fuel and air mix before and during combustion. This should also
improve combustion efficiency.
3-2) The clearance volume can be
made smaller since only one valve need be included in it. Thus the
compression ratio can be increased without lengthening the stroke or
cutting notches in piston faces. This may be more important to diesel
engine designers. In any event a higher compression ratio should
increase thermal efficiency.
3-3) The surface shaping the burn
area should be simpler and smaller. With less surface area and fewer
points and edges to lose heat to, heat losses would be reduced
improving the thermal efficiency of the engine.
3-4) Since one
needs only to include one port in the burn area it should be easier to
find the optimum location for the injector or have more room to place a
second fuel-injector into the cylinder. This or these modification
should improve fuel mixing which would reduce burn time. A reduction in
NOx formation and a small improvement in combustion efficiency should
then result.
Or in the case of a gasoline engine, there will be
more room to put a second spark plug into the cylinder. This should
reduce the combustion time which should also reduce the NOx formation.
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Isometric
View of Burn Area
Two Valve
System ------------ Four Valve System ------------ Uniport Valve System
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2-5) The
above sketches should also show that the Uniport Valve system allows
for a more compact burn area than present designs.
3-3)
In the above skethes the surface of the burn area is colored green.
Intersecting surfaces that form edges are colored red. You can see that
the Uniport Valve design has fewer surfaces that might absorb heat than
the other two designs.
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