Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Invented by someone French.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.

user:
pass:
register,


                                                           

Solid Stirling Engine

The coolant is a solid metal
  (+4)
(+4)
  [vote for,
against]

In the regular Stirling engine, the expanding heated gas pushes the rotor, which in turn pushes a 'displacer' which pushes the heated gas away from the heat source and into the cooling chamber, and after cooling and compressing is pushed back to the heating chamber for another cycle.

In the solid Stirling engine the heated metal rod expands and pushes the rotor, it is then mechanically moved to the cooling location, where it is cooled and detracts, only to be set in place again for the heating cycle.

The movement to and from the heat source and cooling source, can be controlled mechanically, electrically or digitally. The action can be done by moving the sources of heat and cooling, or by moving the rod(s).

If the source of heat is concentrated sunlight, it can be directed (and avoided) dynamically along the pathway, creating a truly rotary Stirling engine.

pashute, Sep 01 2014

Malone liquid engine http://www.douglas-...id/maloneliquid.htm
Bad enough using water, never mind a solid ... [8th of 7, Sep 01 2014]

Nitinol Heat Engine http://www.youtube....watch?v=mlxrOHD49ZQ
Toy version. [LimpNotes, Sep 11 2014]

Bimetal heat engine http://sci-toys.com...thermo/thermo3.html
[scad mientist, Sep 17 2014]

Rubber band heat engine https://www.haverfo...and_heat_engine.htm
[scad mientist, Sep 17 2014]

[link]






       Stirling engines work best where the working fluid has a high coefficient of expansion; hydrogen gas is the optimum. Compared to gases, the expansion of solids is very small.
8th of 7, Sep 01 2014
  

       The expansion of solids is also rather irresistible. Imagine an associated gear ratio, converting that enormous force into significant motion....
Vernon, Sep 01 2014
  

       Soiled Sterling Engine. Engine composed of grubby English pound coins assembled together in such a way as to use their knurled edges as cog wheels that bear against each other.
xenzag, Sep 01 2014
  

       [Vern], that's just a matter of leverage - converting a high pressure short travel to a longer travel at lower force.   

       <link>   

       A "solid" stirling engine might be made to work using a set of long, very thin wires (to maximise &#916;l, and allow rapid heating/cooling) which move in and out of the hot and cold zones, generating power on contraction, not expansion.
8th of 7, Sep 01 2014
  

       //generating power on contraction, not expansion//
They're solid; no reason they can't push AND pull. Or were you thinking wires = too flexible for pull? A "swash plate" style system would be the way to go.
Crazy idea popped into my head - why have multiple independent wires? A piece of pipe (maybe thicker with machined cooling fins) that rotates past the hot source/cold sink, swash plate on a TINY angle at the end. Hmm, I may have to CAD+FEA a model at lunchtime...
neutrinos_shadow, Sep 01 2014
  

       It's a devil getting those &#916;l's like you used to, they just can't get the wood.   

       </bloodnock>
not_morrison_rm, Sep 02 2014
  

       <Henry Crun>   

       "Poor, poor, poor old Jim Tigernuts .... He couldn't get the wood either. He had to put 'em in cardboard boxes."   

       </Henry Crun>
8th of 7, Sep 02 2014
  

       <crun>   

       Come out of there. Tigers aren't meant to be slept in you know. You mustn't... Come out at once   

       </crun>   

       Asked Jutta to run this joke every 24 hours, it's unix server so it can be a crun job.   

       (how everyone laughed)   

       NB the best lines are in Shifting Sands, Series 7, Episode 17. Ironically it's partly about the British Army in Waziristan..
not_morrison_rm, Sep 02 2014
  

       I was able to follow the discussion up to not morrison's first anno.
pashute, Sep 02 2014
  

       You silly, twisted boy, you ...
8th of 7, Sep 02 2014
  

       I was serious :-(   

       Back to the discussion: If instead of a simple solid rod, the rod was made from a porous but rigid metallic material, it would on the one hand gain and lose heat quickly while also quickly expanding or contracting. This can be exploited in various ways, generating power from both contraction and expansion.
pashute, Sep 02 2014
  

       [marked-for-tagline] //expanding and detracting//
Voice, Sep 02 2014
  

       edited
pashute, Sep 06 2014
  

       There was a NASA-developed solar motor, that was a heat engine with a solid 'working fluid'. It was mentioned briefly in a sidebar in popular science or something about 30 years ago. It consisted of a metal pipe or tube, horizontal, supported on bearings at each end, and with a round heavy weight (i.e. a flywheel) at midspan. When placed in the sun, the top of the tube would heat and expand, causing the tube to bend upwards and thus to raise the weight, which (as weights do) preferred a lower position which was conveniently made accessible by rotation of the tube. As you might imagine, the cycle would continue as long as the tube was heated on one side, from any direction except directly underneath.   

       This arrangement leverages a small expansion with large force, as noted by Vernon.   

       I imagine the efficiency and power density to be poor, but it's an interesting and simple heat engine (not necessarily strictly a Stirling cycle, but neither are a lot of 'stirlings'). Also, it fits the description in this idea, hence my anno. Thank you for your kind attention.
afinehowdoyoudo, Sep 11 2014
  

       I might call this baked in the form of Nitinol engines. <link>
LimpNotes, Sep 11 2014
  

       No, you might not, because Nitinol engines exploit flexion, not the expansion/contraction ccle of the true Stirling engine.
8th of 7, Sep 11 2014
  

       Go to google books and look at Popular Science July 1980, page 112.
afinehowdoyoudo, Sep 16 2014
  

       Hmm, load of nitinol springs on a carousel, pressed up against car radiator, one gets hot, expands, then rotate away to let it cool, as the water in rad is usually 80 degrees c. Mighty expensive way to harvest energy given the price of the metal.   

       Now, if you had a closed circuit sub-atmospheric pressure steam engine, with lots of brass twiddly bits and a small robot Fred Dibnah..
not_morrison_rm, Sep 16 2014
  

       pashute, what substance would you use for the rod?
bungston, Sep 16 2014
  

       //I was able to follow the discussion up to not morrison's first anno   

       His Borgness was trying to use a character (not Seagoon) that doesn't work on HB, it's strictly boring old ASCII so something he typed ended up as   

       &#916;l   

       and I was just trying to point out that it didn't work. Unless of course he did mean to type &#916;l.   

       I can't argue with solids heating up and expanding, so I can only agree with pashute that this would work, but what would be the special advantage?   

       The mechanism does strangely remind me of a gatling gun.
not_morrison_rm, Sep 16 2014
  

       // &#916; //   

       Delta-l ; small change in length. Analagous to delta-vee for change in velocity.
8th of 7, Sep 16 2014
  

       //No, you might not// Well I will anyway. The austenite (high temp) crystal has tightly bonded electron bonds and is not flexible, the martensite (low temp) crystal is not as tightly bonded and is flexible. The change from (m) to (a) results in contraction of the material. That this energy is applied in a set vector only means that some of the mechanics for translating it are embodied in the material itself, rather than in piston, rod, and crankshaft.
LimpNotes, Sep 17 2014
  

       corrugated aluminum
pashute, Sep 17 2014
  

       Search for bimetal heat engines. Most are pretty simple lab demonstrations like <link>, but it seems to me that a motor very similar to the nitinol heat engine ought to be able to be built using a cheap bimetallic strip rather than nitinol. I suspect the reason for the typical demonstrations seen on the web is the wide availability of cheap thermometers. If you can't get a bimetallic loop to duplicate the nitinol engine, you could probably arrange several of these bimetallic springs in a rotating contraption to create continuous rotation. That might look similar to a rubber band heat engine <link>.
scad mientist, Sep 17 2014
  

       // a NASA-developed solar motor // Is it just me or is it ironic that NASA would develop a solar heat engine that uses gravity to operate. Of course it could be useful on the moon or simply by using a pulley with tensioned belt instead of the weighted flywheel, but it just struck me as odd.
scad mientist, Sep 17 2014
  
      
[annotate]
  


 

back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle