Stirlingengineforum.com

Yes the Ericson theoretically has a big advantage over the Stirling since the heater surface and volume can be as large as you want without any dead space losses. And in a pressurized closed loop version the same would be true of the cooler. It’s noteworthy though, that Ericson himself was much more successful producing Stirling engines. There’s a lot to be said for simple. Anyway, maybe modern tech could produce a better version and I wish you fun and success.

Bumpkin

One configuration for a ringbom Stirling, or heat engine I could not find in Senft's rather exhaustive coverage was an opposed cylinder arangement.

A video explaining the advantages (diesel engine)


https://youtu.be/UF5j1DvC954

A diesel has certain similarities with a Ringbom, except the Stirling has no ports, injectors, crank (free piston anyway) etc.

Otherwise, many of the advantages of a opposed cylinder diesel would seem to also apply to an opposed cylinder Ringbom.

So, here is a rough sketch, combining some of the best features of a NASA type free piston engine, opposed cylinder diesel and the Ringbom functionality.

I'm not entirely sure the free pistons in such an arrangement could actually maintain synchronization, but it's also difficult for me to imagine how it could be avoided.

There is an expansion of gas between to objects (pistons). They should both be propelled outward an equal distance at an equal rate. Maybe.

Maybe not.

Hankering back to this old thread:

viewtopic.php?f=1&t=461

Late last night, drifting off to sleep I suddenly came up with a newish, fairly simple Stirling turbine design:

It should be pretty self explanatory.


Other than the mechanics that should be pretty obvious I think (just an LTD type displacer in a more or less ordinary displacer chamber) when the displacer is lifted the expanding heated air escapes the chamber through the check valve on the left. Theoretically, this creates a pressure in the pipe that goes to a nozzle that shoots a stream of high velocity air out the nozzle to drive the turbine around which also turns the attached flywheel with the off center pin that controls the lifting and lowering of the displacer.

So as the turbine wheel turns it lowers the displacer down, stopping the heat input. The expanded gas cools as a result of doing the work of driving the turbine, leaving a partial vacuum in the chamber, that tends to pull air from the turbine at the turbine exit port (not seen as it is in the middle, behind the turbine)

Basically a thermal pump driving a turbine that controls the pump.

There is heat, or a temperature difference applied indicated by the flames under the engine and the word "HEAT" which could just as easily have been ice cubes and the word COLD.

Theoretically, due to slightly higher pressure in the nozzle side (left, facing the photo) should be a little warmer than the vacuum side (right).

The question is, would this temperature difference amount to anything that could be usefully employed ?

Oh, and I almost forgot. The turbine should have a generator built into it which should help keep the RPM down to a reasonable speed while giving the turbine some work to do generating electricity.

As the turbine might tend to want to spin at a high RPM, the flywheel controlling the displacer movement might require a step down gearing of some sort. One quick lift of the displacer might create enough pressure to sustain the turbine through who knows how many revolutions. One? Ten? Fifty? One hundred? More?

Probably zero. It might not work at all, but it seems to me like it should, or might.

Some fluid diodes might work better than mechanical check valves.

The difference between this and my earlier versions is that it is not a simple 'ice pump" nor is it so complicated that it could not be fairly easily constructed and tested.

As it is pretty much a closed system, it might even be charged with helium or hydrogen gas, either of which might be more effective than just air.

What about a saturated vapor? It might be possible to get a phase change, condenser (left pipe) evaporator (right pipe). Get some of Daemon's explosions going in there!

Methylene chloride ? ( The stuff in the drinking bird)

Probably construction would be simplified by using a square shaped displacer and square chamber with flat sides, so the check valves could be simple leaf valves.

Well, just sent off for some drinking bird juice (methylene chloride).

Since it is a solvent used as paint remover, and decaffeinating coffee and such, it would probably dissolve most things, like acrylic, foam rubber etc. That I might normally make a Stirling engine out of.

They actually put this stuff in a child's toy? Yikes.

https://pubchem.ncbi.nlm.nih.gov/compou ... oromethane

Might be useful as a heat of the hand thermoacoustic rice (glass bead) engine.

I was just parking the car at the grocery store and had an idea, but nothing to write on other than the wrapper from a slice of pizza. But I wanted to draw a sketch before I get home and forget all about it.


It is a wood (or coal or kerosene or propane or whatever) fired Vuilleumier heat pump.

I'm thinking with a COP > 1 it should supplement whatever fuel is being burned with whatever additional heat the heat pump can draw from the outside air, as well as some of the heat that might otherwise be lost up the chimney.

Not perpetual but impressive numbers never the less....
Omega 1 Engine, air cooled, 11 kg (35lb), 120 kw (160hp), 700cc (427ci), 231 Nm (170ft-lbs) torque (at 5000rpm), idle at 1000 rpm, max 25000
If engine bay is almost empty, chassis weight can be drastically reduced.
https://www.youtube.com/watch?v=Cgi5q0-omlY


The Patent 0602272 from 16.04.1997 of the single stroke engine has expired (Rotary piston machine, Walter Müller)
https://patents.google.com/patent/EP0602272B1/en
https://web.archive.org/web/20190814065 ... index.html



http://eintaktmotor.de/texte/a156.html
the google translation:
The characteristics of the single-stroke engine. . . . . . . .

1 ..are recognizable: by turning away from the 4-stroke process to the 1-stroke process, from dead centers to turning points and from flame front combustion to explosion combustion.

2 ..are recognizable: by the absence or obstruction of the temperature limiter. The explosion combustion may run upwards unchecked, without the risk of knocking!

3 ..are recognizable: Through the seamless expansion, without heat supply up to the exhaust.

4 ..are recognizable: by low engine speeds in the middle of 1500 rpm. and on average low piston speeds of approx. 6 m/s.

5 ..are recognizable: by continuous, undiminished piston speeds.

6 ..are recognizable: By reducing the mixture portions, which can be reduced to 1/16 of the four-stroke portion. These small mixture portions are explosively combusted and expanded in the full four-stroke stroke time (within half a revolution).
This process is equivalent to an extension of the combustion time.

7 ..are recognizable: through variably buffered explosions in the direction of rotation, which are used immediately to deliver work and an acceptable working pressure - which can variably expand to a low exhaust pressure.

8 ..are recognizable: by the high cylinder temperatures, which can be between 200°C and 800°C - and support the combustion explosion.

9 ..Recognizable by the surface cylinder wall temperatures, which at the same time build up the working pressure as a compensating heat accumulator.
The ceramic glow wall only creates the glow layer on approx. 0.2 to 1mm.
In a thin-wall construction, the entire wall thickness glows.

10. It can be seen that mixture enrichments for the purpose of better ignitability can be omitted, because the ignitability is generated by the additional supercritical collision of the charges and by the hot cylinder wall.

11 .Recognizable by the fact that powerful continuous ignition sparks and catalytically active glow zones support the ignition.

13. Recognizable by the thin-walled metal construction of rotary piston locking rollers and cylinders, in which the total sheet metal thickness of the rotary body is 200° to 800° C. This temperature then corresponds to the operating temperature.

14 Recognizable by its hollow, thin-walled and lightweight construction, sparing use of austenitic alloy metals.

15 Recognizable by the fact that cylinder temperatures from 200°C improve efficiency considerably.

16 Recognizable when using problem fuels, or with high C , CH, combustion residues that burn out cleanly.

17 Recognizable by the reduction in boost pressure, which may drop from 5 bar to 2 bar at higher cylinder temperatures.

18 Recognizable that the engine, the combustion is adapted to the fuel.
The fuel quality (octane number) plays a subordinate role.

19. Recognizable by the reduction in compression effort, which can be significantly reduced from a maximum of 5 bar to 2 bar, thus benefiting performance and efficiency.

20 Recognizable that there is no gas exchange. Each explosive combustion process is a self-contained process (loading + expanding).

21 Recognizable by cold compression and hot explosion combustion. The initial temperature of the explosion is not throttled, which corresponds to a correspondingly high initial pressure without knocking. (Peak pressures are buffered and converted into work)

22 Recognizable by the expansion distance, which adapts variably and optimally after the explosion.
The segment stroke can be up to 270°. See <Two Shaft Motor>

23 Recognizable by the fact that the time saved by the explosion compared to the four-stroke flame front is used for expansion. With this technique, a quasi-prolongation of the combustion time is achieved.

24 Recognizable by the fact that the segment lifting cylinders and rotary pistons are used twice within one revolution by changing sides. This doubles the capacity and halves the cylinder wall area.

25 Recognizable by the fact that the engine can be designed as a two- or three-shaft engine, with the two-shaft engine having the advantage that the piston travel of 360°, not 120°, but 270° can be used variably for the explosion and expansion. (enables optimal expansion)

26 Recognizable by the fact that at low power, charging is only possible with 2 bar.
This saves compression energy and improves efficiency.
This engine characteristic is particularly important in city traffic, because CO2 and other exhaust gases can only be reduced in this way.

27 Recognizable by the fact that the air is metered into the fuel, but not the fuel into the air, as is usual with petrol engines. The control is variable depending on the speed through the bypass.

28 Recognizable by the unchecked explosion combustion, in which brief high pressures are exerted on the piston, even during the explosion in the direction of rotation and full use of the expansion. This contributes to better effectiveness.

29 Recognizable by the more difficult NOx formation due to short contact times during explosion combustion.

30 Recognizable by the lack of rotary piston lubrication in the combustion chamber, because the rotary bodies on the surface are kept red hot if necessary. and turn without contact.

31 Recognizable by the missing sealing strips, because the rotary lobes are sealed by their own deposits. The excess is rubbed off.

32 Recognizable by the simple geometry of the rotating elements, which are continuously kept tight by the combustion. The rotating elements are thus insensitive to thermal expansion.
Sealing tolerances on the rotary piston and locking rollers correspond to the bearing and gear wheel tolerances.

33 Recognizable by the fact that there are no lubrication problems in the explosion area. The segment cylinder (hot cell) can be operated up to a surface temperature of 500°C or even 800°C, depending on the material.

34 Recognizable by the separate compressor, which is outside, in the cool area of the engine and can also be additionally cooled if necessary. The recuperative heating takes place only on the already compressed air or mixture.

35 ..you can see that the compressor is lubricated by the fuel itself. Pure bio-oil is well suited for this, but mixtures of diesel and bio-oil are also conceivable.
Gases are generally compressed with the addition of bio-oil.

36. .that the fuels are explosively combusted in accordance with their natural properties, without a disruptive ignition delay and without an upper temperature limit.
(multi-fuel combustion)

37. . are recognizable: by the low compression, which is limited to 2 to max. 5 bar. This decision is based on the consideration that a given mixture volume, whether high or low compression, provides the same amount of pure oxygen for combustion.

38. .are recognizable: through eight working strokes within two 4-stroke engine revolutions, further the hot cylinder wall.

39. .are recognizable by the fact that the charge is ready on demand and within half a turn with a charge pressure of 2 to 5 bar. loaded via eight side inlets.

40. .can be recognized by the fact that the mixture columns in the middle of the cylinder collide and homogenize at supersonic speed.

41. .can be recognized by the fact that there is no wear hardening because the synchronous gears have the same reference circles, but the driven hubs have different diameters. In this way, the solidifications are continuously worn away per revolution by different peripheral speeds.

42. .are recognizable by their smooth running, so that expensive plain bearings can be replaced by inexpensive ball or roller bearings. The symmetrically uniform explosion loading of the rotary wing allows this.

43 are recognizable by the high cylinder temperature.
When designing, it should be noted that a good <efficiency improvement> already occurs at 200°C.

44 it can be seen that the sealing is ensured by the burning. If there is too much, it will be worn down by different circumferential speeds per revolution. This solves a well-known rotary piston problem for maintenance safety.

45 ..Slip losses that may occur in the compressor - still in the intake port - are taken along and homogenized during the next stroke.

46.. that diesel oil can also be ignited at 2 bar because it is supported by two high-performance transistor spark plugs with ignition sparks that are shifted in time.

47 Biological fuels such as vegetable oil or weak gases such as methane, which tend to form soot, burn the soot with and without residue in the heat-insulated single-stroke engine in an environmentally friendly manner.

48 Pure oxyhydrogen or hydrogen - air mixtures can be converted into electricity as an alternative to the fuel cell with a higher efficiency than in the fuel cell, because the single-stroke engine is a real combustion engine with high efficiency. (80%)

49. Recognizable by the fact that the compressor volume is larger than the combustion chamber volume, and the air is metered to the fuel from a maximum via the <bypass>.

50 The critical ignitability of diesel or bio-oil, we more than secured by the up to 800°C hot cylinder walls, the turbulence and the two high-performance spark plugs.

51 Recognizable by the missing flywheel. The torque is transmitted to the motor shaft symmetrically and vibration-free on both sides.
There is no flywheel, the running of the motor is comparable to a three-phase motor, which with 3000 explosion impulses comes close to the AC force field of 50 Hz.

52 If the single-stroke engine is operated with full heat insulation, it is the first internal combustion engine that is similar to the heat-insulated th expansion steam engine), with 1500°C hot explosive gases as an expansion engine.

53 It can be seen that recuperative intake air preheating is possible. The faster small explosions can then also burn efficiently at higher speeds (because they are very small) - and thus also efficiently increase performance.

54 When the intake air is preheated by the exhaust gases, the exhaust gases can theoretically be cooled down to the dew point limit, which has a positive effect on efficiency.

55 There are no residual gas problems after the explosion combustion, because the explosion of the smallest mixture portions at very high temperatures causes all residual gases CO and HC and even soot to burn.
CO2 can only be reduced with a high level of efficiency, because a high proportion of CO2 is a sign of good combustion. (Soot burns completely in a hot chamber).

56 The unused residual heat with an efficiency of 80% is very low, i.e. only approx. 20%. This relatively low level of heating is only 1/4 that of the petrol or diesel engine.
This is the reason that the motor can be thermally insulated without extreme temperature rise.

57 The torque is adjusted by the load. At high speed the torque is low, at low speed the torque is high. A very favorable constellation for a motor that becomes flexible as a result.

58. . Recognizable by the fact that the charging time is also the ignition time and initiates the explosive combustion. This means a significant simplification of the ignition control.

59 The single-stroke engine can be recognized by its versatile application with full thermal insulation and recuperative preheating of the compressed air. With an achievable efficiency of 80%, the principle can hardly be surpassed.

60 Recognizable by the fact that the single-stroke system can also be used as an externally heated engine, as a hot-gas engine, as a high-speed Stirling engine, or as a steam engine.

61 it can be seen that the heat-insulated single-stroke engine can be used as an energy store because it can be operated without internal compression in the engine. if you work with external compressed air generation, the saved compression effort corresponds to the storage capacity.

62 are recognizable from the fact that the service life of the single-stroke motor corresponds to the service life of the synchronous gears and bearings, because the internal wear is self-healing without sealing strips.

63 The single-stroke engine as an impulse radial turbine engine type A-V-A generates within two engine revolutions and at 1500 rpm. 12000 working strokes/min. - without shortening the combustion time. This creates a turbine that develops high torque in the lower speed range.
This property can be transferred to the fast-running single-stroke hot-gas engine as a derivative of the Stirling engine and to the steam engine or engine with external compressed air type D-A-D.

64 The single-stroke engine offers manufacturing and cost advantages through few and uncomplicated engine parts.
The single-stroke rotating elements in the motor cell rotate contact-free without any lubrication. The optimum fit is created during engine operation by erosion, which forms a unit with the engine after a short period of operation. The result is a construction that is considered to belong to the engine, as if the engine were manufactured with the highest precision.

65 The single-stroke engine limits the risk considerably, because the preliminary work for the patent application was checked through functional tests

> There are currently no other alternative solution to the planned single-stroke engine
> There is no alternative engine that would be cheaper to produce than the single-stroke engine.
> There is no vehicle drive with a higher utility than the single-stroke engine.

> There is no more versatile engine system known than the single-stroke engine system,
future innovations with such a wide range of applications.

> The patent is granted and maintained.
> Awareness is spread widely so as not to jeopardize implementation.
> The interaction in function and the functional safety to be expected is in the
other projects, as far as these became known during the patent examination, were not given.
> The property rights have been granted
> Exclusive licensing is possible.

Tom Booth wrote: ↑Tue Feb 15, 2022 2:21 pm
I've actually been considering trying something similar but using a venturi type "pump" in a flowing stream, just to "siphon" cooling water to an elevated location and back into the stream. Don't know if it will work, but I've already bought the supplies.

Something like:

Resize_20220215_155957_7117.jpg

Haven't tried it, but my guess is that without a means to replenish it, the vacuum holding the fluid in the tubes would quickly diminish on account of the dissolved gasses in the water, or by whatever is produced by organisms. A pocket of gas will develop at the top breaking the flow. Vapor lock I think is the term. So it would certainly work until that happened.

Even tap water will do this over time with an inverted U tube filled with water and ends submerged in a beaker. In fact you might even end up with relatively pure O2 because of water's excellent ability to absorb and release it with temperature changes.

Interesting.

Maybe if the flow volume is great enough the potential bubbles would be pushed along, or never have a chance to form.

An occasional purging of trapped air bubbles with a pump?

Now I'm wondering if some kind of valve at the highest point with an inverted bottle above it as a bubble trap might work.

When the bottle fills up with air close the valve and replace it with a water filled bottle and then reopen the valve.
Think that would work?

Tom Booth wrote: ↑Mon Feb 06, 2023 11:35 am Interesting.

Maybe if the flow volume is great enough the potential bubbles would be pushed along, or never have a chance to form.

An occasional purging of trapped air bubbles with a pump?

Now I'm wondering if some kind of valve at the highest point with an inverted bottle above it as a bubble trap might work. When the bottle fills up with air close the valve and replace it with a water filled bottle and then reopen the valve

Think that would work?

All of the above would work. First one (high flow) is common, and your bubble trap/valve is a clever idea as well.

Not sure if everyone here has seen Rüchardt's oscillating ball experiment. There are a few videos on YouTube and a Wikipedia article, websites and such as well as scientific supply outlets where the apparatus can be purchased. Here is one boring video demonstrating this:


https://youtu.be/vLtU7_AofrM

And another explaining how it works:

https://youtu.be/vT6n7VVBvqw

And an advertisement:

https://youtu.be/wFF56-PUEwQ

This oscillator resembles a Stirling engine in many ways.

Theoretically if friction could be eliminated this "adiabatic bounce" could continue, almost indefinitely.

So between me and my wife, Estelle (who suggested using ferrofluid, I've talked about it so much) we came up with what she is calling, (instead of Maxwell's Demon), Tom Booth's energy angel.

I originally presented it as a "thought experiment" but her suggestion to use ferrofluid makes me think it might almost be possible.

Instead of a heavy metal ball use a heavy ferrofluid coated magnet to drop down the tube to reduce friction.

So this should oscillate for some time.

To the Rüchardt apparatus, I've added a regenerative displacer and a Ringbom type actuator.

The weight of the displacer/regenerator is perfectly counter balanced .

So, how it works:

Drop the ferrofluid coated magnetic ball down the tube.

The air in the lower space is compressed raising the pressure and temperature

The high pressure results in a Ringbom type actuation of the regenerative displacer.

While the gas is hot from compression the regenerator sweeps down due to the seesaw action as the counterbalance that is raised due to the high pressure.

When the ferrofluid coated magnet bounces back up, the air in the lower chamber drops in pressure and gets cold while the counterbalance falls raising the regenerator up which releases the stored heat.

In this way the "angel" separates the high energy, hot air molecules from the low energy cold molecules in the gas using only the initial energy derived from gravitational pull and atmospheric pressure that keeps the ball bouncing in the tube.

So, in theory at least, having eliminated friction. (The "Ringbom" type displacer plunger and pivot bearing are also magnetic and coated in ferrofluid) the device creates a temperature difference which could be used to run a number of Stirling engines.

Here is a quick drawing I just dashed off:

I'm thinking the Ringbom counterbalance thing could be oriented up or down depending on which way you want to cause the heat and cold to be separated out. Hot air up and cold air down or vice versa.

With cold on the down side, set on top of a beer cooler, the device could be used for refrigeration.

If it worked that is.

But why wouldn't it?

The labtrek kit video says they have developed a very fast thermometer with response time in milliseconds.

That is something that could be very useful in Stirling engine analysis, perhaps.

There is no price on the website for this kit and software, but I've already sent for a quote. Still awaiting a response.

Tom Booth wrote: ↑Thu Feb 09, 2023 6:28 pm The labtrek kit video says they have developed a very fast thermometer with response time in milliseconds.

A common gy-906 IR thermometer arduino module can provide real-time PWM output of temperature. The PWM period is 1mS per the data sheet.

Well, my gy-906 idea failed because I didn't read the fine print. I had some modules on-hand and decided to try it. The period is in fact good enough for 1k readings per second, BUT those readings are first smoothed out through an on-board DSP filter that cannot be fully disabled. The result is that it's only good enough for 12/second or about 85mS. Still very good, but not what I first thought.

Further, even if it worked, it's measuring the temperature of a target surface. What surface will change temperature at that rate anyway? If you're trying to measure the temperature of the gas, you'll need a target of extremely low thermal mass and high conductivity, while also being a suitable IR target. A very thin sheet of graphite perhaps?

It would be very cool to graph that temperature swing in relation to the cycle, if only to set aside assumptions about what's happening inside. Maybe there's another way to do this by proxy.. Like what other thing changes instantaneously with temperature that could be measured more easily? Pressure of course, but that has its own issues due to volume changes in the system. Voltage from a very low mass and high area thermocouple? Take a standard thermocouple and mash it into a foil thin enough to register changes at a high frequency?

There's probably a paper on techniques concerning this somewhere, but I haven't dug into it.

It's a bit of a difficulty. Just musing but in general a thermometer is measuring a reaction to "heat", that is an expansion of a liquid or metal after taking in some heat.

An IR camera I guess, is doing what?

Anyway, there are supposedly air molecules zipping around bumping into stuff.

A thermometer has what inside? A fluid that can expand. But what is it measuring really? Some average I guess. So it's not actually measuring the energy of individual impacts.

I'm just musing, maybe there is some more direct way of measuring a transfer of kinetic energy other than by measuring the secondary response of some other material.

Some kind of quantum thermometer?

LOL...

Just did a search on that "Quantum thermometer" and there's bunches of articles, but also this video.

I like video so:

Most notable is, whatever they are actually discussing applying this to, there is an offhand after 6:00 mention of the fact that the Quantum thermometer works to measure ambient temperatures like an ordinary thermometer, "to high levels of precision" by measuring the energy gap between qubits,... or some such thing

Unfortunately, I guess it hasn't actually been built yet by the sounds of it, but sounds kind of like what I had in mind, maybe, sort of, I think, possibly, or not.

https://youtu.be/ULd2CpSlh9U

Tom Booth wrote: ↑Sun Feb 13, 2022 2:46 pm The point is, the heat source for the engine is heated plates or vanes that are encapsulated in a very close tolerance heated enclosure with slots the vanes or plates fit into.
A cam controls when the vanes or hot metal plates will drop or slide out or down, out of their slots in the heating unit, into the air filled space, quickly and effectively heating ALL the air at once.

This is exactly what I have thought in the past. It should be the BEST theoretical way to go about it...only problem is I cant think of a way to make this design easy to duplicate and reliably leak free. I do however think I came up with a suitable alternative solution. I will update my post with what I come up with.