Talk:Stirling engine

Lede image
The image at the article head conveys nothing. It is too dark and even when animated it explains nothing about the working or history of the Stirling engine. A better image needs to be found. We need one that conveys the working with being confusing.Lumos3 (talk) 14:42, 8 April 2022 (UTC)


 * I favour this image because 1) it shows the essential simplicity of the design 2) it conveys the timeframe of the design which goes all they way to the industrial revolution.  3)It has warm attractive colours of brass and engineering red. It attracts the reader to look into the subject. Lumos3 (talk) 14:51, 8 April 2022 (UTC)



pressure
contrary to what one reads all over the internet stirling engines do not go below atmospheric pressure and suck the power piston back in if the power piston has one side in the open air.

in another part of the article it is correctly stated that the flywheel provides the work for compressing the working fluid.

imagine an engine sitting ready for work, start heating the hot end, engine runs, the cold end must be above ambient temperature to transfer heat to the atmosphere and so the pressure of the working fluid must be above atmospheric. Froggarana (talk) 16:10, 23 August 2020 (UTC)


 * Your argument is not convincing because the working piston's movement means the total volume is higher than at the start of the cycle. So the conditions you describe do not rule out a pressure of <1atm at the phase within 90° of max volume. 2.100.227.229 (talk) 11:21, 1 May 2024 (UTC)

While the above would be true for a perfectly sealed engine, in practice small leaks mean that the average internal pressure will stabilise to atmospheric, therefore the pressure will indeed be below atmospheric for part of the cycle.Pv&#61;mrt (talk) 18:48, 9 July 2021 (UTC)

by what means does the working fluid leak from a region which you say is below atmospheric to a region at higher pressure ie atmospheric ? 37.1.170.203 (talk) 10:53, 7 October 2021 (UTC)

Single source in section - hotairengines.com
Early hot air engines

This entire section depends upon a single source. While this dissertation seems well laid out, the entire website is the work of a single person, Isaac Woerlen, whose only point of contact is through LinkedIn. The author seems greatly concerned with the environmental impact of all types of engines, and he shows a distinct bias towards hot air energy.

Another problem here is that the text of this section follows very closely on what the website presents:

The first engine of this kind which, after various modifications, was efficiently constructed and heated, had a cylinder of 12 inches (approx. 30 cm) in diameter, with a length of stroke of 2 feet (approx. 61 cm), and made 40 strokes or revolutions in a minute (40 rpm). This engine moved all the machinery at the Dundee Foundry Company's works for eight or ten months, and was previously ascertained to be capable of raising 700,000 lbs. one foot in a minute (approx. 21 HP). —hotairengines.org

The first engine of this kind which, after various modifications, was efficiently constructed and heated, had a cylinder of 30 centimetres (12 inches) in diameter, with a length of stroke of 60 centimetres (2 ft), and made 40 strokes or revolutions in a minute (40 rpm). This engine moved all the machinery at the Dundee Foundry Company's works for eight or ten months, and was previously found capable of raising 320,000 kg (700,000 lbs) 60 cm (2 ft) in a minute, a power of approximately 16 kilowatts (21 horsepower). —Stirling_engine

I've started an RfC about this source. I'd like to hear thoughts on the rest. — Myk Streja ( beep ) 21:40, 31 December 2020 (UTC)


 * That text appears in the 1845 engineering journal where Stirling published his research. Copyright-wise, it is probably public domain now.  It should be presented as a quote here.  Thundermaker (talk) 15:07, 2 January 2021 (UTC)

Agree Re. single questionable source, plus the 'early hot air engines' section was intended to be a brief round-up of precursors to Stirling's work. TBF, this article seems to have become a bit of a mess since I last looked in!Pv&#61;mrt (talk) 18:31, 9 July 2021 (UTC)

The Beta-Configuration blatantly, avoidably, departs from the Stirling-Cycle.
As for the Beta-Configuration, the whole point of the Stirling is that the air expands at the max temp, with heat being added to keep it there, and is compressed at the min temp, with heat being removed to keep it there. But, in the Beta-Configuration, the expanding air has to go through, and be in contact with, the heat-sink. Having the heat-sink remove heat from the expanding air wasn't part of the plan. The Alpha-Configuration doesn't have that fault.


 * Here's a possible (at least partial)answer to my objections:
 * When the air in the hot-space expands: Though the air expanding through the regenerator (which evidently was around the displacer in Stirling's patent) is being cooled by the regenerator, and though the air expanding into the cool region is being cooled...most of the volume of the air is in the large (due to the position of the displacer) hot-space, and therefore most of the air is not being cooled by the regenerator and the cold-space. So the expansion isn't so seriously hindered by that cooling by the regenerator and the cold-space.
 * That mitigates the problems I spoke of, though it doesn't eliminate them. It seems to me that the Alpha Stirling would be more efficient, because it doesn't have that problem, not having to try to use those spaces for dual-purpose.
 * Maybe the inefficiency of Beta & Gamma could be reduced a bit:
 * 1. Maybe it would be feasible for the heat-sink surface to be arranged so that, when the displaer is at or near its top position, it covers all or most of the heat-sink surface.  ...so that the hot air expanding into the top section won't be (as much) chilled by the heat-sink surface.
 * 2. Why not have an outward-flare in the diameter of the displacer's cylinder, a little below the level where the bottom of the displacer is when the displacer is at the top. ...so that, when the displacer is up, having sent the air down to the hot-space, the bottom of the displacer will be in the flared section of its cylinder, thereby leaving a wider space around it, through which for the hot air from below to expand past the displacer without being chilled by the regenerator.
 * In that way, as well, of course the regenerator won't be heated by that expanding air, thereby leaving the regenerator more effective when it's later needed to cool the air being displaced upward to the cold-space.
 * Someone who collects & sells, and maybe makes Stirlings has said that he finds that the Alphas tend to be more powerful. An Alpha was what was used in NASA's Stirling Chevy Celebrity, which beat the original Otto Celebrity in 0 to 60.
 * Of course, if transportation-energy-use, as measured by gallons of fuel purchased, were alloted equally, then a driver could choose any of the ultra-clean-burning external-combustion engines--Stirling (Alpha, Beta, or Gamma) or Rankine (Steam or Freon) based on their price, and based on how much mileage they'd give, with the alloted gallons of fuel.
 * — Preceding unsigned comment added by 71.84.136.105 (talk) 01:24, 17 January 2021 (UTC)


 * Someone said that there are no examples of the Alpha-Configuration being used. Maybe not in table-models, but when, in or near 1986, a NASA team built an automotive Stirling, and installed it in a Chevy Celebrity, a fully-capable and practical prototype that did 0-60 faster than the ordinary Otto Celebrity, and was 33% more efficient, their Stirling-engine used the Alpha-Configuration.  — Preceding unsigned comment added by 71.84.136.105 (talk) 15:04, 4 January 2021 (UTC)

Efficiency compared to that of an internal combustion engine
The article says:

""Stirling engines by definition cannot achieve total efficiencies typical for internal combustion engine, the main constraint being thermal efficiency.""

Though it's true that Otto & Diesel engines can have a higher max temperature due to their briefer combustion, and that the combustion is inside the piston-cylinder, thereby not requiring heat-conduction through a cylinder-wall, the Stirling is still more efficient, due to its ability to more closely approach the Carnot efficiency for a given temperature-difference.

Typically, with current technology, the Stirling is reported to be about 33% to 60% more efficient than the Otto, and about 12.5% more efficient than the Diesel. — Preceding unsigned comment added by 71.84.136.105 (talk) 15:59, 4 January 2021 (UTC)


 * That entire section seems suspect just by the way it's written, making many assertions as if they were common knowledge without source.
 * It's even more suspect considering that it's flat out wrong. Solar concentrator Stirling engines can focus light through a clear section of the shell onto an internal tungsten wire mesh - making them internally heated. As the heat is not conducted though the structural casing you have a theoretical operating temperature limit for the non-structural heat source approaching 3000 degrees Celsius - the actually relevant concerns for max temp are the tungsten wire heat source actually melting (as we all know, tungsten is known for being easy to melt), cooling the transparent section enough for it to remain strong and transparent (that's a thing, clear stuff usually turns opaque at high temperatures!), and actually concentrating Solar energy to that kind of extreme (not as easy as it sounds due to conservation of etendue).

142.186.66.67 (talk) 04:00, 16 February 2022 (UTC)

Deletion of claim that Stirlings require more expensive material.
In the section that compares Stirlings to ICEs, there's a claim that Stirlings require more expensive materials. No, the NASA Stirling installed in a Chevy Celebrity didn't use metals more exotic than stainless-steel. Stainless-steel was used for the high-temperature parts.

Here's that passage, with that claim removed:

[quote] However, Stirling engines are generally not price-competitive as an automobile engine, because of high cost per unit power, low [[power density]. [/quote]

NASA's report about their MOD2 engine said that, with mass-production economy, a Stirling car could be priced comparably to an ICE-powered car. Sure, maybe a bit more, but not prohibitively, outright unaffordably, more. When comparing price, it's important to not forget that mass-production will cost less per unit than building a prototype.

Because of its greater efficiency, the Stirling can run a bit cooler. The MOD2 report said that, at the Stirling's max temperature, NOx emission isn't a problem.

A Stirling car has an advantage over an electric car: The Stirling, made of abundant metals like aluminum & iron (which is what stainless-steel is) doen't need the exotic scarce or semi-scarce metals that batteries & fuel-cells need. For everyone to have electric cars would likely cause disastrous environtal damage from the mining of the needed exotic metals. Iron and aluminum are very abundant in the Earth's crust.

Here's a possible disadvantage of the Stirling for a mass-ownership vehicle-engine:

One good thing about internal-combustion engines is that the combustion is enclose inside the large, heavy and thick motor-block. An external-combustion-engine's burner isn't quite as well isolated.

In any acceptable transportation/energy future, it would obviously be out of the question for the general population to own and drive the big & heavy cars that are now in use. Any personal motor-vehicles would have to be limited to low-power motorbikes & motor-scooters; and maybe tiny ultra-ultra-light cars for special needs, for families & disabled-people.

For such small vehicles, might there not be a problem protecting the fuel-tank and the driver (& any passengers) from the burner?

Well, maybe that problem could be avoided by having a V-2 or V-4 Alpha Stirling at the very rear of the motor-scooter, motor-bike, or tiny car. The crankshaft would be oriented transversely (parallel to the axles), and the hot cylinder(s) would be on the rear side of the V. In that way, the burner(s) would be far from the fuel-tank and the driver.

The cold-cylinder could be vertical, with the hot-cylinder horizontal and pointed backward.

By the way, ICEs have another huge disadvantage for mass-ownership vehicles: They're filthy. ...no matter what the fuel is. Even burning hydrogen or ammonia, there's NOx. Controllable by hang-on devices? With everyone having an ICE car, lots of people don't maintain their cars (maybe many can't afford to). The hang-on devices have to be maintained. The engine itself has to be maintained. With everyone owning & using the filthy ICEs, inevitably there will be many dirty unmaintained ones. ...all the worse when idling at the curbe or under your window, especially when they're cold. With ammonia fuel burned in mass-ownership ICEs, the air will be as full of NOx, in its many forms, and unburned NH3, as it now is full of half-burned carcinogenic hydrocarbons and particulates...and of course NOx. With hydrogen ICEs mass-owned, NOx will be thick.

So I suggest that ICEs (Otto & Diesel) are completely unacceptable for mass-ownership, no matter what the fuel.
 * it all comes down to sources. If you can provide verifiable references for the statements you want to include, that is suitable material for the article; otherwise it can't be used. Personal reasoning, synthesis, or arguments based on personal knowledge without a print source to back it up are not usable here. -- Elmidae (talk · contribs) 22:52, 16 January 2021 (UTC)


 * I know better than to try to get into the article anything that hasn't been copied from somewhere :D
 * Additionally, for verification about the unacceptability of ICEs for mass-ownership, just get a whiff of the air along any busy city street, or in a low-income neighborhood during morning warmup-time. The families of the drivers have to live there.
 * — Preceding unsigned comment added by 71.84.136.105 (talk • contribs) 02:33, 17 January 2021 (UTC)

Proposed explanation of Stirling cycle & the mechanisms that achieve it...for the beginning of the article.
— Preceding unsigned comment added by 71.84.136.105 (talk • contribs) 22:07, 22 January 2021 (UTC)

HP to KW
At 700,000 lb in 2 minutes that's 1,400,000 ft*lb/min. At 33,000 ft*lb/min per HP, that's 41 HP, or 30.75 KW, right? Not 16 KW or 21 HP. 2603:7080:7006:67D3:5197:4559:7896:2EF (talk) 22:46, 1 January 2022 (UTC)

STIRLING ENGINE, STILL JUST AN IDEA!
When we use the term "Stirling Engine" we must strictly distinguish whether we are referring to the heat engines built and patented by Robert Stirling or we are referring to Stirling's idea of a Heat Engine which should operate between two isotherms and two isochores in the so-called Stirling's Thermodynamic Cycle !

Likewise, if we want to explain to someone what the Thermodynamic cycle is, we cannot do it using the Boyle-Mariotte pV-diagram. What is a thermodynamic cycle and how heat is exchanged and converted into work and work into heat is shown in Thermodynamics with a Ts-diagram, i.e. the relationship between temperature and specific values of entropy, volume and pressure in a working medium. Only the Ts-diagram can clearly show the difference between Stirling's and Carnot's Thermodynamic Cycle.

In addition, when explaining the term Stirling engine, it is important to note to readers that this term is massively abused by: irresponsible hobbyists, fake inventors and experts, traders and fraudsters, who sell their " thermal toys " under the name Stirling engine, even though these toys do not have not the slightest connection with Stirling's idea and the Stirling cycle. The same can be said for all the illustrations and animations that mistakenly try to explain to Wikipedia readers what a Stirling engine is and how it should work.

It is even more important to note to the readers that Robert Stirling never realized his ingenious idea of the construction of a heat engine with heat regeneration of the working medium "at a constant volume"! Neither Stirling nor the later builders of the so-called Stirling engine did not solve the problem of guiding the machine elements at a constant volume, but remained on improvisations (it turned out that constant volume is not so easy to control!), which led to the misconception that the problem was solved! Without further ado, this is how I imagine the content of this page (https://austav.eu/stirling.html). Just an idea? Vjekoslav Brkić, Osijek. 89.201.254.27 (talk) 17:38, 5 February 2023 (UTC)

Please get another picture
The picture is terrible as it obscures the very parts we need to see to understand how a Stirling engine works. It is made even worse by the fact that it is the first thing one sees when googling Stirling engine. Earth deserves a better intro to this subject. 23.115.207.161 (talk) 11:20, 6 May 2023 (UTC)

Oil & Gas Wells as heat sources
It is recognized that exhausted oil and gas wells present problems, but many such wells provide a heat source, because the temperature deep in the well is generally quite a bit higher than the temperature at the surface. This temperature difference can be used to power a Stirling engine, so as to provide a source of electricity. I am in Alberta, and there is sporadic interest in utilizing abandoned wells in this way. I would like to see this idea discussed in an article, with a view to the value of many small power production sites. It is reasonable to power a farm or heat a home, using Stirling technology. Janice Vian, Ph.D. (talk) 16:14, 8 July 2023 (UTC)

Regenerator
I edited the leading description to distinguish between the working piston and the displacer. The next paragraph talks about a regenerator, which is not clear enough to judge whether it's true, because I can't tell what it's talking about. As far as I know my stirling engine has no regenerator that stores heat for more efficiency, unless we're saying that the hot side of the engine does not need tool cool down and heat up again because the fluid is moving rather than the flame. 2.100.227.229 (talk) 11:25, 1 May 2024 (UTC)

Ross Linkage
While the relevancy is debatable considering his chief contribution is the linkage design and the source would need fixed if not improved, Ross' work on alpha designs featuring the linkage has been cited by other sources for Stirling engine design, and I've seen multiple vendors with low-temperature beta designs marketed as novelties that are described as having Ross linkages, so I think it's safe to say his contribution is broadly recognized and its inclusion is not promotional. Proposing a removal or re-source. SoundwavePS (talk) 12:54, 27 June 2024 (UTC)