First it seems clearly obvious that regenerators have an effect once aded to the displacer but one may consider that advantage comes oftenly with inconvenient. Therefore obtained results could differ relative to the architectural design, size, shape and mateer used to proceed.

Nevertheless regenerators seemed to bring out more than they cost. Sumurazine of the subject will say that they increase speed transfer of the gas, creating new acces instead of the unique circle peripheric gate (clearance between dispacer and wall chamber)Further to this idea, the complete transfer of the gas will be more balanced and potentially be done at a higher speed if opertures are done within the dispacer. Paradoxaly these new opertures are creating dead volume within the chamber that basically we may avoid. The all trick is then to find the good balance of it, i.e. to achieve a good design. One more advantage of creating such air gap through regenerators is to help avoiding or reducing lateral movement of the displacer when running, keeping more constant the clearance. This remarks ends up the velocity fluid transfer and aerodynamic aspect relative to the displacer.

Second, one may consider the thermal aspect of the regenerator whom first goal is to use part of the heat left by the gas to increase the efficiency of the Carnot Cycle. In this way regenerators may be considered as heat capacity storage unity that will release it during heating and expansion phase. Here the question occurs since everyone knows that main body displacer is made out of isolation foam that prevent body diplacer to get hot and to avoid making a heat transfer gate with the cold plate.Therefore its also obvious that displacer should never be in contact with neither of the plates at end positions of the cycle engine. This is apparently the good combination of regerator size, thihcness and peripheric clearance for gas flow that will improove the performance compared to a full displacer. Senft may precise that compensation relative to the diameter of the displacer would be done in case adding regerators, so in in away to keep quite similar swept efficien gas volumes of the chamber. i.e. outside clearence will be reduced in case adding regerators that are obviusly ceating an additional dead volume (or unswept volume). Its then a question that should be first thouht when creating the design of the displacer and the chamber relative to their initial optimum volumes to perform at best.

Three, is the matter used for regerators. I’m actually trying different materials and consider as well their heat conductivity, weight,thichness, velocity gas flow and stucture to compare.Basically test could be done with some 3M Scocht brite, thin wire meshes or even some polyurethane foam on which im focusing some interest. Quick notice that only a small few holes in the dispacer will help gas transfer.

About your design it may seems the regerators diameter is too big, resulting a bigger dead volume which you could reduce. Top position of the mesh and thickness of it is a subject to further discuss. Please leave any comment about heat inertia about material u may use in regerator body. I ‘d appreciate if you could release some test depending from the material used for regerators.

For additional information here after is a copy of what u can find on Wikipedia Us about regerators. its quite a good sumarize of the topic i guess.

Philippe

[edit] Regenerator
Main article: Regenerative heat exchanger
In a Stirling engine, the regenerator is an internal heat exchanger and temporary heat store placed between the hot and cold spaces such that the working fluid passes through it first in one direction then the other. Its function is to retain within the system that heat which would otherwise be exchanged with the environment at temperatures intermediate to the maximum and minimum cycle temperatures,[12]thus enabling the thermal efficiency of the cycle to approach the limiting Carnot efficiency defined by those maxima and minima.
The primary effect of regeneration in a Stirling engine is to increase the thermal efficiency greatly by ‘recycling’ internal heat which would otherwise pass through the engine irreversibly. As a secondary effect, increased thermal efficiency promises a higher power output from a given set of hot and cold end heat exchangers (since it is these which usually limit the engine’s heat throughput), though in practice this additional power may not be fully realized as the additional “dead space” (unswept volume) and pumping loss inherent in practical regenerators tends to have the opposite effect.
The regenerator works like a thermal capacitor. The ideal regenerator has very high thermal capacity, very low thermal conductivity parallel to fluid flow, very high thermal conductivity perpendicular to fluid flow, almost no volume, and introduces no friction to the working fluid. As the regenerator approaches these ideal limits, Stirling engine efficiency increases.[13]
The design challenge for a Stirling engine regenerator is to provide sufficient heat transfer capacity without introducing too much additional internal volume (‘dead space’) or flow resistance, both of which tend to reduce power and efficiency. These inherent design conflicts are one of many factors which limit the efficiency of practical Stirling engines. A typical design is a stack of fine metal wire meshes, with low porosity to reduce dead space, and with the wire axes perpendicular to the gas flow to reduce conduction in that direction and to maximize convective heat transfer.[14]
The regenerator is the key component invented by Robert Stirling and its presence distinguishes a true Stirling engine from any other closed cycle hot air engine. However, many engines with no apparent regenerator may still be correctly described as Stirling engines as, in the simple beta and gamma configurations with a ‘loose fitting’ displacer, the surfaces of the displacer and its cylinder will cyclically exchange heat with the working fluid providing a significant regenerative effect particularly in small, low-pressure engines. The same is true of the passage connecting the hot and cold cylinders of an alpha configuration engine.

I have an off-grid house so energy from renewables is of special interest to me. A year or so ago, I saw something on TV about a generator powered by a Sterling engine at the focal point of a solar array (based on an old satellite dish).

I thought the process seemed fairly “developed” and looked for kits or something to come out. (Note – I have a degree in Music and am not allowed to handle sharp objects ’cause I’m accident prone, so trying to build something myself is not in the cards…) However, the discussion here makes me think that (for me) this would not be a practical addition to my system.

Lets face it – putting up a solar dish and engine in the front yard that only produces 1 watt would only irritate my wife while doing little to charge my batteries.

Is this technology just too “immature” to be of real use for someone like me? I’m looking for some alternatives to PV that I can use to expand my generation capacity. Water is not available, wind is good but windmills aren’t and generators based on the Tesla turbine seem to be “vapourware”.

Sorry if you feel this post is off-topic but I figured that you engineering types who are really working on this stuff would have the answers to my naive questions. Thanks for your patience.

Roger

I was looking at your Maker Faire 2008 Engine and it seems quite large however you state it only delivers 0.09W. I do not understand that.
Is that because you are only putting in a small amount of power or are there huge losses. For example, if you put in heat at a rate of 100W, how much power would the engine deliver? Thanks.

good job even i can understand it….

As air passes through the regenerator as well as around the displacer, could the speed gain be due to less air resistance?

Would it be more efficient to increased the diameter of the displacer, so more air passes through the regenerator?

nice work btw

Al

In one of my LTD Stirlings I used succesfully Scotch Brite cleaning pad as regeneratormaterial.

see:
Http://home.hccnet.nl/hvisser.5

next-Gallery- model 23

Greetings from Zeeland, Holland

Huib Visser