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This article should be checked for deletion. A radiator can not produce thrust as long as the air is not forced to expand one way. Unlike for a jet-engine or a ram-jet there is no mentioning of compressing the air prior to heating. Only the exhaust gases of an internal combustion engine themselves maybe used as jets. -- Moritzgedig ( talk) 12:09, 24 January 2014 (UTC)
@ Andy Dingley, Steelpillow: I also do not understand how "free energy power plants" work. Maybe you could explain like you explained this. Oh wait you didn't explain it. What surface does the thrust work on? How come the air does not go around the duct? Will the thrust exceed the drag? Was it thrust or just reduced drag? No one of us has to understand it for it to be real, but people just thinking they understand it does not make it real either. -- Moritzgedig ( talk) 10:12, 25 January 2014 (UTC)
@
User:Steelpillow "a ramjet [...] still works at subsonic speeds [...] but much less efficiently."
Ok, the air is compressible at the speeds these planes were going. At M=0.3 or 230mph compressibility can no longer be fully ignored as I did. At M=0.5 the effect becomes noteworthy. The article now mentions compression. --
Moritzgedig (
talk) 18:27, 25 January 2014 (UTC)
A 1941 Flight article with an explanation, and quote from Meredith here: [1] and an earlier 1937 article based on a lecture by Roy Fedden here: [2] and another article mentioning 'Mr Meredith of the RAE' here; [3]— Preceding unsigned comment added by 80.7.147.13 ( talk) 20:41, 1 March 2014 (UTC)
BTW, F. W. Meredith later worked on automatic pilots and after he left the RAE, took up a position at Smiths Instruments. — Preceding unsigned comment added by 80.7.147.13 ( talk) 19:59, 8 March 2014 (UTC)
@Moritzgedig-The Meredith effect does in effect "compress" the air. Incoming air will be traveling-relative to the plane at 100-400 mph. The diffuser before the radiator will slow the air, and its static pressure will increase. [5] As heat is transferred to the air by the radiator, it will expand to stay at ~ constant pressure. The now hotter air will be re-accelerated by the nozzle to produce some propulsion or at least reduce drag. The process is similar to nuclear-jet propulsion. [6]. ~JoeB34997152 — Preceding unsigned comment added by Joeb34997152 ( talk • contribs) 23:37, 4 August 2016 (UTC)
I find August 1935 http://naca.central.cranfield.ac.uk/reports/arc/rm/1683.pdf as the year of publication not 1936 as the article states. Vandalism? -- Moritzgedig ( talk) 17:47, 25 January 2014 (UTC)
A sub-sonic Meredith effect ducted radiator differs from a supersonic ramjet. A supersonic ramjet uses a constriction and resulting shockwave to compress and slow the air before further heating it, but constrictions only compress supersonic flows. A subsonic flow is instead expanded and accelerated by a constriction. So a Meredith effect duct first diverges, causing the flow to compress and slow before it meets the heat source, and then the exit nozzle is purely convergent in contrast to a ram jet's convergent-divergent nozzle. These facts were key to my understanding of the effect, but were only implicit in Meredith's original paper. They are confirmed by diagrams of the P51's radiator duct, e.g. http://i101.photobucket.com/albums/m56/babraham227/51.gif And here is a site that seems to have it straight: http://contrails.free.fr/engine_aerodyn_radia_en.php But the wikipedia article seems to be describing the principles of operation of a supersonic ramjet. In particular, while the forwards thrust is developed on the divergent section of the duct, unlike in a supersonic ramjet that section is not the exit but the inlet (called a diffuser). A Meredith ducted radiator is a subsonic ramjet, but as subsonic ram jets are quite different to supersonic ones, and probably more people are familiar with the supersonic version, it probably doesn't help to say so. thomas 86.159.241.198 ( talk) 20:23, 28 April 2014 (UTC)
"Many engineers did not understand the operating principles of the effect. A common mistake was the idea that the air-cooled radial engine would benefit most, because its fins ran hotter than the radiator of a liquid-cooled engine, with the mistake persisting even as late as 1949."
So, WHY is this wrong? The article doesn't say. The description appears to state that all you need to get thrust is to heat the air into a convergent/divergent nozzle. So why can't this be done on a radial?
Maury Markowitz ( talk) 14:51, 26 May 2014 (UTC)
Per [9] and others, there's some back and forth editing on whether the Cratus design by undergrad student Samantha Schueler should be included.
There are two refs included (of several out there, just Google it) which demonstrate that the design was awarded an American Institute of Aeronautics and Astronautics (AIAA) prize in a student design competition. One ref mentions that the Meredith effect was considered during the design. Should this section be included or not?
IMHO, no. It does not show any significant relevance to the Meredith effect. It does not appear to be substantially reliant on it (I don't doubt that the ability to keep the screen clear in flight, or the cupholders stable, was considered too). The sources are certainly weak on any detail of this. I can't see the student design paper visible on-line, which would be a big influence on judging it noteworthy here. I also doubt whether there's much Meredith effect to be had. It uses three BMW car engines, presumably turbocharged, and as modern engines (especially turbocharged) simply don't reject the same levels of waste exhaust heat as WWII V12s did, there's less energy for Meredith to work with.
This might yet be significant, but it needs a better source, probably the design paper, to demonstrate what relevance Meredith has to it, and more importantly here, vice versa. At present, it doesn't. Andy Dingley ( talk) 16:24, 6 August 2015 (UTC)
Actually the consensus is for it to be removed. I have no vendetta at all and am actually involved with aircraft engineering that uses this for reduction of cooling drag. Some have flown. But even these real life aircraft do not warrant inclusion since they do not provide the reader with useful information. I went to the wiki page to find useful information and found a useless reference to a paper aircraft (not an actual aircraft or engineering study on the subject) in the main text. Your wife's paper may be great. But many paper aircraft have made claims that they will use this and this alone is not useful information. — Preceding unsigned comment added by 2602:304:AE99:A229:755D:B031:F6BD:6A74 ( talk) 17:18, 19 January 2016 (UTC)
Please read the above and you will see the consensus was that it was not relevant. Please note that I absolutely never insulted anyone or anything and I hope you refrain from personal attacks in the future. I stick to stating the obvious facts and reasons. To me you are the one who is edit-warring like you have in the past with other pages. You are the one who made claim to a "personal vendetta" when in fact none exists on my part. There is no "notability" in a paper design even if it won an undergraduate award against a few other papers. But the real point here is the inclusion does not pass the most basic test of what should be included. Does it provide useful information to users of Wikipedia? No it does not. I am not at all fighting you or your friends. I am just trying to keep Wikipedia useful to everyone and I will keep trying to help where it is needed. — Preceding unsigned comment added by 2602:304:AE99:A229:755D:B031:F6BD:6A74 ( talk) 19:42, 19 January 2016 (UTC)
This article is based upon silly, sophomoric "junk science", and it attempts to describe an effect that does not exist in the real world. In fact, if it did, it would violate the laws of physics. What is described here is essentially a "free energy" device. Whatever heated air (or liquid) that the engine radiator generates is offset by increased drag. Furthermore, if the air is heated it would expand, yes. And if that expanded air was directed into a decreasing conic section it would indeed speed up a bit. However, the amount of "additional thrust" would be completely negligible, and insignificant and would not in any way add anything to the forward thrust of the aircraft. It would be about the same as gluing balloons to the aircraft tail and letting the air out. Insignificant.
The P-51 used an underbelly intake duct because of the design of the aircraft and the position of the engine within the airframe. It has nothing to do with this so-called, fictitious "Meredith Effect". There have been no papers or actual engineering research published to confirm this "effect". None. If it did work as described (?) in this article, then all subsequent prop-driven aircraft would have had this scoop to "compress" ... oh come on. Everyone knows that doesn't work as claimed. And it is NOT related to ramjet engines, which operate at supersonic speeds and are a completely different effect and topic. Someone please delete this article. It is based on a fiction and cannot be substantiated by any reliable source. 73.6.96.168 ( talk) 04:16, 24 August 2020 (UTC)
There are some pretty bizarre objections to this article from people that seem to know a little physics but not much thermodynamics. I think this might be partly because older versions of the article had false claims that have now been removed, but I am just going to go over the ones I spotted. The basic principle is so fundamental (use heat to expand/accelerate air to generate thrust) I am actually a little surprised that anyone could disbelieve it.
A lot of "free energy" designs are not really "free", but are in fact energy scavenging devices that only work on paper when you discount friction and other losses. You can't generate work from them or in a lot of cases even generate enough work to overcome their own internal friction. But the issue isn't that "they don't work", but that some people make inflated claims about what are basically classroom physics toys.
But... while many "free energy" devices are really just energy scavengers, that is not the same thing as the concept of energy scavenging being junk science. Stirling Engines and Dielectic generators are both commonly run on "waste" heat. Recovering usable energy from waste heat is a huge part of modern engineering design. The difference between a classroom physics toy and a power station is scale.
This one is just flat out backwards and wrong. Ramjets need to operate above a certain speed to generate ram pressure, but that speed is well below the speed of sound. In fact, the largest losses in supersonic engines comes from deccelerating supersonic airflow to subsonic speeds because fuel will not burn in a supersonic airflow.
(it might be worth removing an reference to ramjets, because there is not really any comparison between the ramjet pinciple and what this is. Ramjets generates heat by burning a compressed fuel/air mixture. This article describes a heat exchanger process. Compression has nothing to do with it.)
This one is reasonable, until you factor in that the drag was there already. This is the engine cooling system. Unless you make the entire skin of the aircraft a radiator, you are going to be in some way gathering air and transfering heat by conduction (and generating drag in the process). That air is hitting the plane and generating drag regardless. In the simplest of aircraft designs, the engine is just left exposed and the air flow cools it directly. The drag is always there, subsequent design is about minimising that. However large or small the any thrust effect might be, so long as a "Meredith" cooling system does not add MORE drag than a non-Meredith system, the overall result is a net gain. (absolutely a badly designed system might add more drag than an alternative, but drag is one one those things that is endlessly tested during design)
This is the most reasonable objection of all. Except it hinges on the question: what is the definition of a negligble effect on a high performance aircraft? Shaving rivets off the leading edge of the wing? Switching from fabric wings to stressed metal? Changing from 70% octane to 100% octane? There is only one definition that matters: has there there been shown to be a measurable difference in perfomance? It might be the case that this effect really is negligible. But, from the fact this article has citations and the concept has existed since the 1940s, it would seem to suggest that there is data out there better than the arguments on a Talk page.
If actual citations of evidence DISPROVING this effect exists, by all means add it to the article, but all of the objections below amount to "I don't see how this could work, therefore it can't." Jmackaerospace ( talk) 00:25, 10 May 2021 (UTC)
I found it! The article contains much, much math, and an analysis of head losses of air flowing through radiators, and through ducts to and from radiators. [1] We can see that if the radiator is contained in the fuselage or wings, the front area of the aircraft is reduced. It logically follows that the inlet duct is smaller than the frontal area of the radiator. Since the duct increases in size, we expect the air velocity to drop and the pressure to increase as per Bernoulli's principle. Some web sites remark on this, but it probably is an artifact of the duct's reduced frontal area. Meredith notes that the air passing through the radiator will increase temperature by around 40C°. I suspect that the radiator can be enlarged to dump heat at a reduced head loss. Meredith proposed at the end of the paper, that the heat generated by the radiators and the engine exhaust can be recovered to generate thrust — which is what we are discussing here.
It appears that Spitfires, Bf-109Es, de Havilland Mosquitos and P-51 Mustangs were designed to use Meredith effect. Curtis P-40 Warhawks, Hawker Typhoons, the production Tempests, and Lockheed P-38 Lightnings did not employ the principle. Annular radiators, used on Junkers engined Ju 88s and Fw 190s, probably did not get much thrust from radiator air, but the design reduces frontal area.
JHowardGibson ( talk) 20:13, 10 May 2021 (UTC)
References
This is the
talk page for discussing improvements to the
Meredith effect article. This is not a forum for general discussion of the article's subject. |
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|
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This article should be checked for deletion. A radiator can not produce thrust as long as the air is not forced to expand one way. Unlike for a jet-engine or a ram-jet there is no mentioning of compressing the air prior to heating. Only the exhaust gases of an internal combustion engine themselves maybe used as jets. -- Moritzgedig ( talk) 12:09, 24 January 2014 (UTC)
@ Andy Dingley, Steelpillow: I also do not understand how "free energy power plants" work. Maybe you could explain like you explained this. Oh wait you didn't explain it. What surface does the thrust work on? How come the air does not go around the duct? Will the thrust exceed the drag? Was it thrust or just reduced drag? No one of us has to understand it for it to be real, but people just thinking they understand it does not make it real either. -- Moritzgedig ( talk) 10:12, 25 January 2014 (UTC)
@
User:Steelpillow "a ramjet [...] still works at subsonic speeds [...] but much less efficiently."
Ok, the air is compressible at the speeds these planes were going. At M=0.3 or 230mph compressibility can no longer be fully ignored as I did. At M=0.5 the effect becomes noteworthy. The article now mentions compression. --
Moritzgedig (
talk) 18:27, 25 January 2014 (UTC)
A 1941 Flight article with an explanation, and quote from Meredith here: [1] and an earlier 1937 article based on a lecture by Roy Fedden here: [2] and another article mentioning 'Mr Meredith of the RAE' here; [3]— Preceding unsigned comment added by 80.7.147.13 ( talk) 20:41, 1 March 2014 (UTC)
BTW, F. W. Meredith later worked on automatic pilots and after he left the RAE, took up a position at Smiths Instruments. — Preceding unsigned comment added by 80.7.147.13 ( talk) 19:59, 8 March 2014 (UTC)
@Moritzgedig-The Meredith effect does in effect "compress" the air. Incoming air will be traveling-relative to the plane at 100-400 mph. The diffuser before the radiator will slow the air, and its static pressure will increase. [5] As heat is transferred to the air by the radiator, it will expand to stay at ~ constant pressure. The now hotter air will be re-accelerated by the nozzle to produce some propulsion or at least reduce drag. The process is similar to nuclear-jet propulsion. [6]. ~JoeB34997152 — Preceding unsigned comment added by Joeb34997152 ( talk • contribs) 23:37, 4 August 2016 (UTC)
I find August 1935 http://naca.central.cranfield.ac.uk/reports/arc/rm/1683.pdf as the year of publication not 1936 as the article states. Vandalism? -- Moritzgedig ( talk) 17:47, 25 January 2014 (UTC)
A sub-sonic Meredith effect ducted radiator differs from a supersonic ramjet. A supersonic ramjet uses a constriction and resulting shockwave to compress and slow the air before further heating it, but constrictions only compress supersonic flows. A subsonic flow is instead expanded and accelerated by a constriction. So a Meredith effect duct first diverges, causing the flow to compress and slow before it meets the heat source, and then the exit nozzle is purely convergent in contrast to a ram jet's convergent-divergent nozzle. These facts were key to my understanding of the effect, but were only implicit in Meredith's original paper. They are confirmed by diagrams of the P51's radiator duct, e.g. http://i101.photobucket.com/albums/m56/babraham227/51.gif And here is a site that seems to have it straight: http://contrails.free.fr/engine_aerodyn_radia_en.php But the wikipedia article seems to be describing the principles of operation of a supersonic ramjet. In particular, while the forwards thrust is developed on the divergent section of the duct, unlike in a supersonic ramjet that section is not the exit but the inlet (called a diffuser). A Meredith ducted radiator is a subsonic ramjet, but as subsonic ram jets are quite different to supersonic ones, and probably more people are familiar with the supersonic version, it probably doesn't help to say so. thomas 86.159.241.198 ( talk) 20:23, 28 April 2014 (UTC)
"Many engineers did not understand the operating principles of the effect. A common mistake was the idea that the air-cooled radial engine would benefit most, because its fins ran hotter than the radiator of a liquid-cooled engine, with the mistake persisting even as late as 1949."
So, WHY is this wrong? The article doesn't say. The description appears to state that all you need to get thrust is to heat the air into a convergent/divergent nozzle. So why can't this be done on a radial?
Maury Markowitz ( talk) 14:51, 26 May 2014 (UTC)
Per [9] and others, there's some back and forth editing on whether the Cratus design by undergrad student Samantha Schueler should be included.
There are two refs included (of several out there, just Google it) which demonstrate that the design was awarded an American Institute of Aeronautics and Astronautics (AIAA) prize in a student design competition. One ref mentions that the Meredith effect was considered during the design. Should this section be included or not?
IMHO, no. It does not show any significant relevance to the Meredith effect. It does not appear to be substantially reliant on it (I don't doubt that the ability to keep the screen clear in flight, or the cupholders stable, was considered too). The sources are certainly weak on any detail of this. I can't see the student design paper visible on-line, which would be a big influence on judging it noteworthy here. I also doubt whether there's much Meredith effect to be had. It uses three BMW car engines, presumably turbocharged, and as modern engines (especially turbocharged) simply don't reject the same levels of waste exhaust heat as WWII V12s did, there's less energy for Meredith to work with.
This might yet be significant, but it needs a better source, probably the design paper, to demonstrate what relevance Meredith has to it, and more importantly here, vice versa. At present, it doesn't. Andy Dingley ( talk) 16:24, 6 August 2015 (UTC)
Actually the consensus is for it to be removed. I have no vendetta at all and am actually involved with aircraft engineering that uses this for reduction of cooling drag. Some have flown. But even these real life aircraft do not warrant inclusion since they do not provide the reader with useful information. I went to the wiki page to find useful information and found a useless reference to a paper aircraft (not an actual aircraft or engineering study on the subject) in the main text. Your wife's paper may be great. But many paper aircraft have made claims that they will use this and this alone is not useful information. — Preceding unsigned comment added by 2602:304:AE99:A229:755D:B031:F6BD:6A74 ( talk) 17:18, 19 January 2016 (UTC)
Please read the above and you will see the consensus was that it was not relevant. Please note that I absolutely never insulted anyone or anything and I hope you refrain from personal attacks in the future. I stick to stating the obvious facts and reasons. To me you are the one who is edit-warring like you have in the past with other pages. You are the one who made claim to a "personal vendetta" when in fact none exists on my part. There is no "notability" in a paper design even if it won an undergraduate award against a few other papers. But the real point here is the inclusion does not pass the most basic test of what should be included. Does it provide useful information to users of Wikipedia? No it does not. I am not at all fighting you or your friends. I am just trying to keep Wikipedia useful to everyone and I will keep trying to help where it is needed. — Preceding unsigned comment added by 2602:304:AE99:A229:755D:B031:F6BD:6A74 ( talk) 19:42, 19 January 2016 (UTC)
This article is based upon silly, sophomoric "junk science", and it attempts to describe an effect that does not exist in the real world. In fact, if it did, it would violate the laws of physics. What is described here is essentially a "free energy" device. Whatever heated air (or liquid) that the engine radiator generates is offset by increased drag. Furthermore, if the air is heated it would expand, yes. And if that expanded air was directed into a decreasing conic section it would indeed speed up a bit. However, the amount of "additional thrust" would be completely negligible, and insignificant and would not in any way add anything to the forward thrust of the aircraft. It would be about the same as gluing balloons to the aircraft tail and letting the air out. Insignificant.
The P-51 used an underbelly intake duct because of the design of the aircraft and the position of the engine within the airframe. It has nothing to do with this so-called, fictitious "Meredith Effect". There have been no papers or actual engineering research published to confirm this "effect". None. If it did work as described (?) in this article, then all subsequent prop-driven aircraft would have had this scoop to "compress" ... oh come on. Everyone knows that doesn't work as claimed. And it is NOT related to ramjet engines, which operate at supersonic speeds and are a completely different effect and topic. Someone please delete this article. It is based on a fiction and cannot be substantiated by any reliable source. 73.6.96.168 ( talk) 04:16, 24 August 2020 (UTC)
There are some pretty bizarre objections to this article from people that seem to know a little physics but not much thermodynamics. I think this might be partly because older versions of the article had false claims that have now been removed, but I am just going to go over the ones I spotted. The basic principle is so fundamental (use heat to expand/accelerate air to generate thrust) I am actually a little surprised that anyone could disbelieve it.
A lot of "free energy" designs are not really "free", but are in fact energy scavenging devices that only work on paper when you discount friction and other losses. You can't generate work from them or in a lot of cases even generate enough work to overcome their own internal friction. But the issue isn't that "they don't work", but that some people make inflated claims about what are basically classroom physics toys.
But... while many "free energy" devices are really just energy scavengers, that is not the same thing as the concept of energy scavenging being junk science. Stirling Engines and Dielectic generators are both commonly run on "waste" heat. Recovering usable energy from waste heat is a huge part of modern engineering design. The difference between a classroom physics toy and a power station is scale.
This one is just flat out backwards and wrong. Ramjets need to operate above a certain speed to generate ram pressure, but that speed is well below the speed of sound. In fact, the largest losses in supersonic engines comes from deccelerating supersonic airflow to subsonic speeds because fuel will not burn in a supersonic airflow.
(it might be worth removing an reference to ramjets, because there is not really any comparison between the ramjet pinciple and what this is. Ramjets generates heat by burning a compressed fuel/air mixture. This article describes a heat exchanger process. Compression has nothing to do with it.)
This one is reasonable, until you factor in that the drag was there already. This is the engine cooling system. Unless you make the entire skin of the aircraft a radiator, you are going to be in some way gathering air and transfering heat by conduction (and generating drag in the process). That air is hitting the plane and generating drag regardless. In the simplest of aircraft designs, the engine is just left exposed and the air flow cools it directly. The drag is always there, subsequent design is about minimising that. However large or small the any thrust effect might be, so long as a "Meredith" cooling system does not add MORE drag than a non-Meredith system, the overall result is a net gain. (absolutely a badly designed system might add more drag than an alternative, but drag is one one those things that is endlessly tested during design)
This is the most reasonable objection of all. Except it hinges on the question: what is the definition of a negligble effect on a high performance aircraft? Shaving rivets off the leading edge of the wing? Switching from fabric wings to stressed metal? Changing from 70% octane to 100% octane? There is only one definition that matters: has there there been shown to be a measurable difference in perfomance? It might be the case that this effect really is negligible. But, from the fact this article has citations and the concept has existed since the 1940s, it would seem to suggest that there is data out there better than the arguments on a Talk page.
If actual citations of evidence DISPROVING this effect exists, by all means add it to the article, but all of the objections below amount to "I don't see how this could work, therefore it can't." Jmackaerospace ( talk) 00:25, 10 May 2021 (UTC)
I found it! The article contains much, much math, and an analysis of head losses of air flowing through radiators, and through ducts to and from radiators. [1] We can see that if the radiator is contained in the fuselage or wings, the front area of the aircraft is reduced. It logically follows that the inlet duct is smaller than the frontal area of the radiator. Since the duct increases in size, we expect the air velocity to drop and the pressure to increase as per Bernoulli's principle. Some web sites remark on this, but it probably is an artifact of the duct's reduced frontal area. Meredith notes that the air passing through the radiator will increase temperature by around 40C°. I suspect that the radiator can be enlarged to dump heat at a reduced head loss. Meredith proposed at the end of the paper, that the heat generated by the radiators and the engine exhaust can be recovered to generate thrust — which is what we are discussing here.
It appears that Spitfires, Bf-109Es, de Havilland Mosquitos and P-51 Mustangs were designed to use Meredith effect. Curtis P-40 Warhawks, Hawker Typhoons, the production Tempests, and Lockheed P-38 Lightnings did not employ the principle. Annular radiators, used on Junkers engined Ju 88s and Fw 190s, probably did not get much thrust from radiator air, but the design reduces frontal area.
JHowardGibson ( talk) 20:13, 10 May 2021 (UTC)
References