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.

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.

Isometric View of Burn Area

Two Valve System ------------ Four Valve System ------------ Uniport Valve System

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.