Steam Engine Design/Rotating Valve
Main > Energy > Steam Engine
See also Electric Valves for Steam Engine
Gregor's Proposal
What about a totally linear steam engine? Linear alternator, and hydrodynamic bearings using water (tap off of the condensate return pump maybe) for the linear bearings. Easier to make a large expansion ratio in a single stage than with crankshafts. Mounted vertically to avoid the static axial load on the piston rod.
Electric valves: Suppose you take a ball valve. Make it so it can rotate continuously. Now attach a small brush-less motor or stepper motor. Make the hole through the ball very small and likewise with the input/output holes so that during a full rotation, only a very small fraction of the time is the valve "open". Have it rotate at the same frequency as the cycle frequency of a steam engine. Thus the valve opens and closes at just the right frequency. But it opens and closes non-abruptly and the full-open has a limited open area. Although that is similar to a bump valve. It also does not have to be a ball. Suppose it was a cylinder and rot with a slot in it instead, could be easier to make. A roller bearing with a slot in it might make a good valve bit thing. It can be made longer to make the full-open position have less constriction without affecting the open-time. Thus higher abruptness could be achieved... What about the steam trapped in the slot? probably not a problem?
Problems: the actuator has to be kept below the curie point of the material used, probably not hard. Come to think of it, the water would condense in any non-heated-by-the sun parts, an this could be taken advantage of a s a handy lubricant.
But the whole point is to be able to change the open time as a fraction of cycle time which requires that the outlet valve area be changed somehow. That could be added in some way, but might end up more complex than a similar variable-bump valve thing (but if the wear issues are too hard to solve with bump valves maybe it would be useful).
The key thing is the recognition that the timing stroke-to-stroke does not really change and therefore some sort of continuously rotating actuator can be used without the inertia being a problem.
Drawing
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