Talk:Stirling engine/Archive 4

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Introduction again

While trying to catch up on the current state of micro CHP, I happened upon this web page http://carbonlimited.org/2007/02/27/end-of-domestic-scale-chp/ which has a sort of pop-up link to the wiki stirling engine article. Try it and I think you'll agree that it highlights both the importance of the introduction and its deficiencies - though, of course, it leads on to the 'important stuff' I think the casual reader just looking at the contents of the pop-up box would not feel themselves particularly enlightened. So, could someone have a crack at a really KISS 'what is it and why should I be interested' first paragraph and can't we find an alternative to that £$%^& illustration which not only provokes repeated outbreaks of school-boy humour but doesn't even have a regenerator! Pv=mrt (talk) 12:18, 9 May 2008 (UTC)

Added 'why should I be interested?' para Pv=mrt (talk) 17:13, 11 May 2008 (UTC)

Introduction readability

I have just reverted to the version of the introduction I introduced on the 6th of December. It is important to note that the lede being for the lay reader means two things:

1. It should not be full of jargon.
2. This does not mean, "keep all the jargon but add in explanations".

This edit is guilty of the first problem - it attempts to summarise the entire article in the first line of the introduction. This is not necessary. This edit is guilty of the latter - much of the detail included here can be explained in the article body, as it is assumed that detail will be provided there.

Chris Cunningham (not at work) - talk 21:21, 19 December 2008 (UTC)

I like your new wording for the introduction. Lumos3 (talk) 21:42, 19 December 2008 (UTC)

Thanks. However, I see it has been changed again. I propose that the old version, which is much closer to the style detailed in WP:LEDE, should be restored. The current version contains far too much technical detail which is already contained within the article body. Chris Cunningham (not at work) - talk 11:34, 20 December 2008 (UTC)

We have revised the intro extensively before, and I have to warn you that by changing it you are opening Pandora's box! It's impossible to please all readers and all editors, so you must build consensus and seek compromise. I am disappointed that on one of the recent revisions, some important material was deleted and replaced with factually inaccurate material. That is not an appropriate way to "simplify" the article or to make the intro less technical. Also, don't assume that all the technical info in the intro is covered elsewhere, because I'm not sure it is. Keep in mind that other editors will delete material in the article on the basis that it is covered in the intro! Anyway, if you insist on a non-technical intro, it would be better to move it to a section titled "technical intro", or the like. That way this important information is available for technically minded readers who seek it, and it can be skipped by readers who aren't or don't. Please do not delete large sections of material without considering the interests of a variety of readers and editors. thanks. Mikiemike (talk) 21:03, 21 December 2008 (UTC)

My only interest here is in having the introduction conform to the norms expressed in the Manual of Style. I'm happy to discuss individual components of it, but I don't believe that the previous version was set in stone - especially because quite a bit of it was my doing in the first place. Lede sections are not supposed to be full of technical detail, and that's the long and the short of it. For now, I've moved the new material into appropriate sections of the article body - at some point someone will need to rigorously analyse this article's flow and content to ensure that material is covered in as logical an order as possible and that as little is duplicated as we can get away with. As for the argument "that other editors will delete material in the article on the basis that it is covered in the intro", that's a matter for diligence of this page's maintainers - it's not a reason to reduce the effectiveness of the lede. Chris Cunningham (not at work) - talk 11:11, 22 December 2008 (UTC)

I've now restored the previous revision, as there has been no counterargument. Chris Cunningham (not at work) - talk 11:46, 1 January 2009 (UTC)

Please stop reverting the introduction of this article to your preferred wording without discussing the issue. An open discussion of this issue is located here, where I express concern that the desire to fully summarise the article's subject within the course of the very first sentence is misguided and leads to a poorer flow. It is expected that when a user is reverted that the next step is to discuss this issue.

Over the last month, you have now reverted to your preferred wording three times without discussion. Edit summaries are no substitute. For now I'm going to leave the article as-is, but if you can't explain why it is that the use of the terms "closed-cycle" and "regenerative" are so essential to the first sentence that it is worth negatively impacting the readability of the article then I'll be removing them again. Chris Cunningham (not at work) - talk 14:56, 23 December 2008 (UTC)

I've now restored the previous version. Please discuss this issue on the article's talk page before reinstating your preferred version again. Chris Cunningham (not at work) - talk 11:46, 1 January 2009 (UTC)

Hi Chris, Aplogies for my lack of an earlier response - I have been away from the PC during the holiday period.

I had assumed that the concise first line definition of what comprises a Stirling engine was simply getting 'lost in the noise' of successive edits and therefore reverted without discussion. I was about to do so again when I saw your comments in the discussion page and the finally looked at my own talk page!

The sentence under discussion is not 'my' preferred wording as such, but wording which emerged by concensus after much discussion in April/May '08 and, as far as I can see, meets the requirements of the lead style guidelines admirably. It "unambiguously defines the topic" - a Stirling engine is unequivocably a closed cycle regenerative heat engine with gaseous working fluid (actually I'd prefer 'permanently' gaseous to positively differentiate it from Rankine machines and yes, I am aware of the Malone liquid Stirling engine!). That it is usually an external combustion engine is certainly important (therein lies some of the Stirling engine's greatest strenghths and weaknesses) but this follows from it being a closed cycle device and is not in itself a defining feature. I accept that some of the terms used in the definition might not be immediately familiar to the lay reader but, in accordance with the guideline "where uncommon terms are essential to describing the subject, they should be placed in context, briefly defined and linked", short definitions of 'closed-cycle' and 'regenerative' are included. Lumos observed that 'working fluid' might also be an unfamiliar term to some so that might also be worthy of some explanation.

The guide also states that the first sentence should answer the question "why is the subject notable?". I find that a difficult one as the Stirling engine has been an abiding interest of mine for over 30 years so as far as I am concerned its notability hardly needs qualifying!

I therefore propose that the first sentence, together with the supporting brief definitions, be reinstated.Pv=mrt (talk) 11:17, 5 January 2009 (UTC)

Left for a week and no counter argument - so here we go again! I really don't see this opening statement as contentious, there are other areas of the article which are far more worthy of the attentions of the 'professional' editors - for instance, exactly what does the Background section achieve?. Pv=mrt (talk) 10:20, 12 January 2009 (UTC)

That which is most important is not that which is necessarily the most discussed. :) Anyway, as to the point: A common problem with the ledes of technical articles on Wikipedia is that they are heavily front-loaded with qualifiers due to a perceived need to eliminate any potential ambiguity as soon as possible. I would suggest that in your admitted capacity as a subject expert that this is what is happening here.

Closed Cycle and Regenerative are not "qualifiers" but the very essence of what a Stirling engine is. They are two characteristics which ALL Stirling engines must have - even gaseous working fluid is open to question if one includes the Malone.

WP:LEDE applies to the first paragraph of the lede, not to the first sentence. Our readers are not to be assumed to have such severe ADD that reading past the initial sentence of an article is impossible; the revised first sentence (A Stirling engine is a type of heat engine with a gaseous working fluid) still establishes what the subject is, which is all that is required of it.

Yes, but it doesn't exactly narrow the field - in fact it could equally well refer to any internal combustion engine and even vapour power cycles unless one were to prefix 'gaseous' with 'permanently'. Mind you at least it's not one of those awful intro's which seeks to define the subject by telling you what it's not (cf Baldrick's definition of dog).

The material contained within the original first sentence was already incorporated into the paragraph as a whole, which is used to establish the subject's notability.

Why shilly-shally about with a whole paragraph when you can pin down exactly what the subject is in ten words?

I would suggest that it be reinstated due to the increased readability of the rewritten version; the paragraph as a whole is no more ambiguous, but it is easier to read as terms are introduced in logical and readable prose rather than front-loaded onto the first sentence and then explained by a disjointed mini-glossary in the second. Chris Cunningham (not at work) - talk 13:31, 13 January 2009 (UTC)

I guess we will have to agree to disagree, I find the wording broadly hammered out during the April/May discussion perfectly readable, admirably concise and to the point - you clearly feel it doesn't conform to the Wikipedia 'norms' (I compared with 'elephant' for some reason and although some of the terms used in the first sentence of that article may be more familiar, they are no less 'technical'). I shaln't revert it if you choose to change it again, but I do wish someone else would come in and arbitrate. Perhaps a citeable definition would help - I have access to a pretty good library of Stirling engine related titles, though most are written at a level which rather expects you to know what the subject is already!Pv=mrt (talk) 16:41, 13 January 2009 (UTC)

I'm happy to wait for wider input; we're not writing to a deadline here. The reason for "shilly-shallying" is for the sake of the quality of the article's prose; much like a novel does not introduce each character in a single line full of every adjective which would describe them, for the sake of not overwhelming the inexpert reader it makes sense to take a paragraph to nail down the basic description of the subject. But let's see what others think. Chris Cunningham (not at work) - talk 23:21, 13 January 2009 (UTC)

A couple of citeable definitions to add to the pot:-

"A Stirling cycle machine is a device which operates on a closed regenerative thermodynamic cycle with cyclic compression and expansion of the working fluid at different temperature levels and where the flow is controlled by volume changes so that there is a net conversion of heat to work or vice-versa" - and breathe!

(Graham Walker, lecture notes for Stirling seminar at University of Bath 1971 - I believe later published by Oxford University Press as "Stirling Cycle Machines").

"A heat engine is a Stirling engine for the purposes of this book when:

1. The working fluid is contained in one body at nearly a common pressure at each instant during the cycle.

2. The working fluid is manipulated so that it is generally compressed in the colder portion of the engine and expanded in the hot portion of the engine.

3. Transfer of the compressed fluid from the cold to the hot portion of the engine is done by manipulating the fluid boundaries without valves or real pumps. Transfer of the fluid back to the cold potion of the engine is done in the same way.

4. A reversing flow regenerator (regenerative heat exchanger) may be used to increase efficiency."

(William R Martini "Stirling engine design manual" NASA report available as print on demand book from University press of the Pacific and at http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19830022057_1983022057.pdf )

So both feel that the closed cycle aspect is important and also that the working fluid should be manipulated purely by volume changes without valves (Walker goes on to amplify on this point stating that open cycle regenerative machines employing valves should be called Ericsson cycle machines). I'm particularly taken with Martini's second point (pretty much tells you in simple terms how and why the engine works!) though he is suprisingly luke warm about the inclusion of a regenerator.Pv=mrt (talk) 11:36, 14 January 2009 (UTC)

Stirling Engines for Dummies. The gas goes inside a closed container. The fire goes on the outside. The rest is pure magic. Mikiemike (talk) 00:38, 15 January 2009 (UTC)

Not very constructive but I get your point. Perhaps you would care to share your opinion on the opening paragraph - or are you tiring (as I am) of this article which seems to suffer from more than its fair share of entropy growth ;-)Pv=mrt (talk) 10:08, 15 January 2009 (UTC)

Along with a major reorganization of the article (most of which works very well) I see we have another attempt at the the intro. Quite happy to see the 'proper' definition moved to a second paragraph, but unfortunately the first paragraph now tells you nothing whatsoever about the Stirling engine specifically - it could equally well refer to almost any other external combustion heat engine.

Pleased to see the back (well, relegation) of the 'oh so amusing' rhombic picture at last, but the replacement needs some explanation - and a regenerator!Pv=mrt (talk) 22:59, 18 January 2009 (UTC)

Gone ahead and added some info to new illustration + redone first parag to reflect very visible alternate compression and expansion at different temps (awaiting 'fallout'!). Also moved slightly reworded potted history/modern interest parag back to intro from history section - it was agreed some time ago that both these topics should be briefly mentioned there but I thinks the parag still needs work (should probably mention CHP as most likely modern application for Stirling as ref'd at one time by sleeve notes to AJO's "The air engine - Stirling power for a sustainable future").Pv=mrt (talk) 11:00, 19 January 2009 (UTC)

Re-reading the opening sentance I realised that what has emerged from all the wrangling is pretty much a simplified form of Walker's definition above. So accordingly I have added ref - perhaps that is one line of this article which can now be left alone!Pv=mrt (talk) 14:56, 29 January 2009 (UTC)

Oh Mikie, I thought we'd done this one to death and settled on the simplified Walker definition for the intro with all detail left 'till later (ie name, formal definition and classification section). But now, without a word of discussion, you have effectively reverted to a long dead version - and worse, you have left the citation to Walker which now has little or no relevance. Suggest if you feel that external combustion need clarification by reference to the steam engine you add material, either to the intro of (preferably) to the classification paragraph in the section referred to above and leave the hard won, layman friendy, citeable, first sentance alone! In the mean time, I will edit to reinstate first sentance but leave your material intactPv=mrt (talk) 10:36, 8 July 2009 (UTC)

First of all, "energy" is not "power". So the language could be improved. Also "heat engine" or at least "engine" is preferable to "device", because the sentence goes on to describe a heat engine: " by alternately compressing and expanding a fixed quantity of air or other gas (the working fluid) at different temperatures". Also doesn't the phrase "different temperatures" seem vague and non-descript? What's different about the temperatures? LOL.

I think my comparison with the steam engine is "laymen friendly", and it transitioned nicely, since there is other mention of steam engine. --Mikiemike (talk) 13:22, 9 July 2009 (UTC)

Oh a wholesale revert, how mature. Argument is clearly futile and I'm not going to get myself all wound up as happened before. I hope you will at least allow me to remove the now irrelevant Walker citation.Pv=mrt (talk) 15:21, 9 July 2009 (UTC)

I see the Walker quote from above: "A Stirling cycle machine is a device which operates on a closed regenerative thermodynamic cycle with cyclic compression and expansion of the working fluid at different temperature levels and where the flow is controlled by volume changes so that there is a net conversion of heat to work or vice-versa" (Graham Walker, lecture notes for Stirling seminar at University of Bath 1971 - "Pv_mrt" believes later published by Oxford University Press as "Stirling Cycle Machines").

It seems like he uses the words "cycle, machine, device" to avoid using engine. "cyclic" is perhaps more articulate than "alternating". "net conversion of heat to work" is a good way to put it. Note that "work" is energy, which is NOT quite the same as "mechanical power". I'd rather use the whole quote than paraphrase it to death. Mikiemike (talk) 03:05, 10 July 2009 (UTC)

Walker's wording is designed to cover both engines and heat pumps etc. "Cyclic" is indeed more articulate, but perhaps less well understood by the layman than "alternating" - as noted above, the statement was designed to work with the new lede animation where the alternating compression and expansion can be clearly seen. Likewise, power (work per unit time) will be a more familiar concept when applied to engines than work itself. Using the whole quote would be fine in my view, but when something similar was tried a while ago it had to be abandoned as other editors objected to the use of technical terms such as "regenerative" and "closed cycle" in the lede (briefly defining the terms was also rejected). Thus the Walker derived first sentance was arrived at which, together with the animation, would hopefully allow the ab initio reader to get an immediate 'handle' on what a Stirling engine is and be tempted to read further where it is formally defined and its operation, construction etc are described in greater detail.Pv=mrt (talk) 09:49, 10 July 2009 (UTC)

This may be the people's encyclopedia, but it is still supposed to be an encyclopedia first and foremost. (I shouldn't have to restate this obvious fact to other editors.) I understand editors wanting to use lede language that is "familiar" and "layman friendly", but when editors bend over backwards so far that they sacrifice factual and technical accuracy, that's when you know it's gone too far. Look at it this way, why would someone even read the encyclopedia if they didn't expect to learn something new? The whole point of an encyclopedia is to present information that is unknown and unfamiliar to the reader. The editor's art is to present that unfamiliar information in a way that can be deciphered and understood, without sacrificing factual accuracy. Unfamiliar information is not something to be avoided here, rather this is the place to put it!

So don't censor it, but rather, articulate it and explain it. --Mikiemike (talk) 13:07, 10 July 2009 (UTC)

Well, you'll have to take that up with those who deemed the lede as it was, say, here:- http://en.wikipedia.org/w/index.php?title=Stirling_engine&oldid=259715021 too technical as I find myself largely in agreement with your sentiments if not with your wording ;-)Pv=mrt (talk) 13:55, 10 July 2009 (UTC)

Mikie, I have made a few minor changes which should be non controvercial but have allowed reintroduction of citation for first sentance and, I hope, clarified wher you were heading with your contrast to steam engine.Pv=mrt (talk) 11:16, 27 July 2009 (UTC)

History

In response to the cleanup request, I have added a number of refs to the history section. This seems to have raised an issue as to whether Stirling's original intention was fuel saving or creating a safer engine. While it is interesting to speculate on what might have been in the mind of the 26 year old Robert Stirling when he invented his engine, the original patent of 1816 concentrates on fuel saving whereas the first reliable referance I can find to safety is in a paper presented by James Stirling to the Institute of Civil Engineers in 1845, exerpts from which appear in several souces including Robert Siers biography of Stirling. Accordingly I intend to add a citation request to the statement which gives priority to the safety aspect. Pv=mrt (talk) 08:45, 18 April 2008 (UTC)

No citation has been forthcoming to support the safety before economy argument. I intend therefore to remove citation request and revert article to the order of priorities suggested by the existing refs. Pv=mrt (talk) 10:40, 25 April 2008 (UTC)

Go ahead --Mikiemike (talk) 07:24, 27 April 2008 (UTC)

Mikiemike, Why did you revert to safety before economy without adding any supporting refs? Pv=mrt (talk) 07:19, 26 April 2008 (UTC)

Hargreaves suggests that safety may be equal to or more of a factor than efficiency. Also the steam engine was underdeveloped at that point in time (1816-1818), with efficiency at only 2%; later it was increased to 5%, and then 10%, (Hargreaves), making it similar to a Stirling. It's a minor point, so I'm not going to belabor it. (and no snide remarks from the peanut gallery :-). Pop quiz: Why is an exploding Stirling engine safer than an exploding steam engine? --Mikiemike (talk) 07:24, 27 April 2008 (UTC)

Ok, given the 'go ahead' followed by a few reservations (I have re read the relevant passage in Hargreaves), I shall reintroduce the ref to efficiency, but avoiding any specific claim of priority. Readers can see the relative dates of the original patent, which refers only to fuel saving, and the first mention (that I am aware of) of the safety aspect and draw their own conclusions. They may further reflect that Boulton and Watt built a successful business initially by licensing Watt's inventions for a fee based on the fuel savings they achieved.

Re. the relative 'merits' of an exploding boiler and Stirling engine - I guess it is all down to the relative amounts of stored energy. Robert Stirling's son Patrick was apparently present at two hot cylinder failures of the Dundee foundry engine and the only inconvenience he felt on these occasions was getting a little black smoke thrown in his face (Sier, biog. Robert Stirling). As well as compressed 'gas', a steam boiler contains a volume of hot water much of which will vaporise explosively if the boiler should rupture - ISTR this phenomenon is called a 'blevvy' (sp?). Pv=mrt (talk) 19:45, 3 May 2008 (UTC)

The picture labels the generator as 1951, but the linked picture is of a 1953? —Preceding unsigned comment added by 24.108.247.64 (talk) 02:40, 18 January 2009 (UTC)

External links

I'd like to know why this page has adopted such a strict policy regarding the external links section. While I fully support the notion that 'wikipedia isn't a collection of external links', I find external links sections to be very useful in most cases.

I don't see why one contributor has the right to go posting such a strong No More Links warning in the external links section, and wish to remove that warning and reinstate a range of subject relevant external links. GDHowlerson (talk) 11:29, 18 June 2008 (UTC)

There is no reason that you cannot submit as many links as you like to the Open Directory Project for indexing. That's what it's there for. As for why this page in particular takes a firm line, I'd say that it's rather than other pages fail to follow policy properly rather than that this one is being excessive. Chris Cunningham (not at work) - talk 15:25, 18 June 2008 (UTC)

I don't think it is sufficient to just state "you can post your links on the ODP" - the ODP has nothing to do with wikipedia, and is a different subject altogether. I disagree about other pages failing to follow policy, I think your interpretation of the policy is flawed. I will illustrate. Take a page such as this one, about cola drinks. Several of the links in the External Links section are good links, and beneficial to the article as a whole. However, in your view, they should be removed.GDHowlerson (talk) 16:10, 18 June 2008 (UTC)

Well, no, my understanding of policy isn't flawed. WP:EL is policy, and it explicitly makes the case that where there's no consensus that particular external links are appropriate (which there isn't, here) that a link to ODP is a good substitute. As for the examples on cola, I don't think any of those links are of particular value to the article and wouldn't have a problem with them being removed, but their existence is not a counterargument in itself. Chris Cunningham (not at work) - talk 17:48, 18 June 2008 (UTC)

Geothermal engines

After reviewing material online, I removed the section on Geothermal stirling engines due to speculative statements, original research, and weasel words. The only citation was a link to a forum thread summed up by "this would be cool if someone did this". There is a study by Los Alamos National Labs about hot rocks and heat extraction, but no follow-up studies on its use in stirling engines. There are no news posts of companies even thinking about doing this (Google News, all dates). Until anyone finds an actual implementation or research article, the section Stirling engine#Heat sources will have to do. -- mordel (talk) 18:51, 29 January 2008 (UTC)

---

Well done.

For a geothermal power plant, the Rankine cycle/(steam turbine) is a more appropriate technology, because AFAIK, it is easier to drill one big hole than lots of little holes, and a steam power plant is more affordable and easier to scale up to megawatt capacities. An exception would be where geothermal heat is distributed through an infrastructure of pipes, then CHP could favor Stirling engines.

Mikiemike (talk) 19:59, 5 February 2008 (UTC)--

---

Choice of diagram

I am having a difficult time seeing past how incredibly phallic that initial diagram is. It seems an intentional, and arguably successful, attempt at humor. Can other readers relate to this? Jaredsm (talk) 22:24, 19 June 2008 (UTC)

I have no problem with the image. As some Freudian once said "Sometimes an umbrella is just an umbrella". Lumos3 (talk) 23:42, 19 June 2008 (UTC)

I'd gladly see it replaced if it would end the repeated outbreaks of school-boy humour this article seems to suffer from. Besides which it does not even show that defining component of a Stirling engine - the regenerator! Pv=mrt (talk) 12:58, 25 June 2008 (UTC)

Yeah, sometimes an umbrella is just an umbrella, but sometimes a Stirling engine diagram is a penis. Besides, as Pv=mrt said, it's not very illustrative. --Xkcd (talk) 06:49, 21 July 2008 (UTC)

For posterity, File:BetaStirlingTG4web.jpg is the image in question. I'd also like to note that the preceding is the best comment I've ever read in my three years of active editing on Wikipedia. Randall, you should be very proud. -Verdatum (talk) 18:37, 15 October 2009 (UTC)

In the cooler (blue)cyliner, piston should be 2-3 times thicker and ther should be some gap between the walls and the piston. -VJ —Preceding unsigned comment added by 120.61.14.20 (talk) 05:54, 24 November 2009 (UTC)

Too long

Before splitting off into separate articles, how about organizing this article to remove duplications? We don't need the thermodynamic cycle explained twice, for example. Some of the prose seems a litle fat, too, and could probably be condensed without spiltting. --Wtshymanski (talk) 17:55, 25 August 2008 (UTC)

I'll try to work on this. This has the potential to be an excellent article, but it needs some top-down rearranging first. Chris Cunningham (not at work) - talk 18:30, 25 August 2008 (UTC)

Recent extensive work by thumperward, johnlogic and headbomb has gone some way towards bringing much needed order to this article. However, there is still a fair bit of overlap in the 'theory of operation' and 'functional description' sections and the important 'regenerator' section has become unwieldy as successive editors have added their own pet way of trying to understand this complex subject - "thermal capacitors", "lumps of matter" etc. For me, Allan Organ's elegantly simple "to retain within the system that heat..........." sentence says most of what needs to be said about what the regenerator actually does, but I appreciate that the section also needs to cover something about the design challenge of heat transfer and thermal capacity versus dead space and flow resistance, example physical implementations, why the regenerator is a defining component of the Stirling engine, and why some engines can still be correctly referred to as Stirling engines without having an identifiable regenerator.Pv=mrt (talk) 10:31, 20 January 2009 (UTC)