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Combined Piston/Valve

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PaulR:
Would a combined piston/valve like that in the attached image work or have I forgotten something fundamental?

The (long) piston has longitudinal passages with short connections to the circumference to admit and expel air. Air enters via the passage about halfway up the cylinder and is exhausted as the other passage begins to be exposed towards the top of the stroke. It seems like the engine would get a short blast of air and time to get much of the exhaust out.

Jasonb:
My gut feeling says the short inlet burst may not be long enough. Also the inlet will start to open as the piston is still trying to go down

PaulR:

--- Quote from: Jasonb on October 04, 2025, 03:29:34 PM ---...Also the inlet will start to open as the piston is still trying to go down

--- End quote ---
Oops yes hadn't realised that. Can't think of an obvious way to fix that so probably a non-starter then.

Kim:

--- Quote from: PaulR on October 04, 2025, 03:48:51 PM ---
--- Quote from: Jasonb on October 04, 2025, 03:29:34 PM ---...Also the inlet will start to open as the piston is still trying to go down

--- End quote ---
Oops yes hadn't realised that. Can't think of an obvious way to fix that so probably a non-starter then.

--- End quote ---
But how is that really any different from your uniflow engine?  :thinking:  Doesn't the inlet open on that as the piston is still going up?  And it worked...

Kim

PaulR:

--- Quote from: Kim on October 04, 2025, 04:27:49 PM ---
--- Quote from: PaulR on October 04, 2025, 03:48:51 PM ---
--- Quote from: Jasonb on October 04, 2025, 03:29:34 PM ---...Also the inlet will start to open as the piston is still trying to go down

--- End quote ---
Oops yes hadn't realised that. Can't think of an obvious way to fix that so probably a non-starter then.

--- End quote ---
But how is that really any different from your uniflow engine?  :thinking:  Doesn't the inlet open on that as the piston is still going up?  And it worked...

--- End quote ---
Yes I actually typed in the original post that it seems to be a variant of the uniflow engine but edited that out before posting! I'll think a bit more on it, see if there's any sort of refinement that can be made. Changing the inlet from a circle to a slot springs to mind but not sure if that would make a positive difference  :Lol:

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