Are the compresion/expansion stages necessary?

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nufan_wfk
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Joined: Wed Aug 30, 2006 11:09 pm
First Name: Kevin
Last Name: Thayer

Are the compresion/expansion stages necessary?

Post by nufan_wfk »

I've been looking into Stirling engines recently, and am a little
confused about why the compression/expansion stages exist.

It seems to me that the 90-degree difference between the pistons is
more an artifact of having them mechanically connected, and the
compression/expansion stages are a way of coping with the need for
mechanical linkage.

By removing the mechanical linkage, it seems like you could get an
engine that's closer to the theoretical heat-engine and possibly more
efficient.

Or, does the hot/cold-sinking of the temperature generated by the
compression and expansion stages fully compensate for the added work
it takes to compress/expand the air?

I propose a design without mechanical linkage, which generates
electricity using a linear induction system.

Would the following engine be (theoretically) more efficient?

stage1: cool air is in hot side, no air in hot side. Air expands,
pushing up hot-side piston. Piston movement pushes magnet through a
coil, charging a battery, capacitor, whatever.
stage2: Hot side reaches maximum movement, reverse wiring on coil,
pushing hot side down, and pulling cold side up. Hot air is
transferred to the cold side. The energy required to move the air
would have to be less than the energy gained in stage 1
stage3: Cold air contracts, pulling down cold side piston, moving
magnet through a coil of wire, generating electricity, and storing it
somehow.
stage4: the reverse of stage2: cool air moving to hot side.

Here's
some pictures of what i mean. I know the magnet movements aren't quite
to scale, but it communicates the idea.
stan.hornbaker
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Joined: Thu Jun 20, 2002 6:01 pm
First Name: William S.
Last Name: Hornbaker

Response to Are the compresion/expansion stages necessary?

Post by stan.hornbaker »

Here is a link to a very good basic explanation and/or review of Stirling enines prepared by a PE who is deeply involved in the subject. It well worth your time to study.


http://www.sesusa.org/StirlingPrimer.htm


This should provide information to assist you to answer your questions.

The Ringbom engine is the only design I am aware of that does not incorporate linkages of some sort but has other features you sketch does not incorporate.
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