Request for input on radically new turbine concept!

[recursive prophet]

I would greatly appreciate any comments/criticisms the physics cognoscenti on this forum might be able to offer on this proposed new family of turbo devices. If what is claimed here is correct, this might be a truly unique and promising application of turbine technology that will affect many disciplines.

The intro below is a first draft. Do take a moment to check out the full analysis of XpoTurbines available clicking the link. Many graphs and pictures, plus a detailed description of how the XT works. Looks feasible to me, but my knowledge of thermodynamics is quite limited.



XpoTurbines
I would like to introduce you to a new family of turbomachines with a wide range of applicability, including electricity production, shaft work, thrust generation, and cooling. The technology provides new directions in flow organization, thermal management, materials, and processes. As a family, XpoTurbines offer reduced cost, reduced mass, reduced volume, reduced noise, and reduced pollution. In addition, they provide increased reliability, durability, fuel flexibility, dynamic range, and power density. The family characteristics include statorless construction, integrated heat exchangers, controlled porosity passages, helicotoroidal blading, and the use of rotating turbomachine enclosures as compact heat exchangers and “fans”.

Although XpoTurbine technology can be used to manufacture turbomachines with a wide range of sizes, small turbomachines are especially attractive as they have the potential for greatly increased power/mass and power/cost. Additional benefits of reduced scale include reliability via parallelism, throttlability via modularity, and the ability to provide power closer to the point of use, which reduces grid costs and losses and increases the potential to use the waste heat from the engine for combined heat and power.

XpoTurbine technologies are outlined in the attached PDF and available on the web at http://www.thermodynamic.biz

[ben m]

Just a comment: after paging through dozens of pages of your document I still have no idea what your technology actually is. It's some sort of turbine something---in a very flat package? Or maybe in a tube? Maybe bladeless? And something similar (or the same? Or in reverse?) can be used as a chiller or something? I really can't tell.

So, my advice: if you've got a design for a small, efficient, compact turbine, start your document with a nice clear cutaway picture of the turbine. What's rotating? Where is the fuel injected? Where does it burn? Then explain why this is better than the next-best-thing in small turbines---remember, anyone can claim that they have a hyperefficient turbine. Why should I believe you rather than the last guy?

That's what *I* look for in a sales pitch, anyway.

[mhaze]

I would greatly appreciate any comments/criticisms the physics ...
XpoTurbine technologies are outlined in the attached PDF and available on the web at http://www.thermodynamic.bizI'm dubious about flameholders working on the combustor section integrated into the disk at small size factors.

Also there's considerable efficiency loss in the movement of air (think momentum) sideways and then along the helical sections.

Finally, at small sizes friction forces predominate due to laminar flow which creates some scaling issues.

Generally, small is "way harder".

[Fnord]

Didn't Nicola Tesla (http://en.wikipedia.org/wiki/Tesla_turbine) invent something like this?


The Tesla turbine is a bladeless centripetal flow turbine patented by Nikola Tesla in 1913. It is referred to as a bladeless turbine because it uses the boundary layer effect and not a fluid impinging upon the blades as in a conventional turbine. The Tesla turbine is also known as the boundary layer turbine, cohesion-type turbine, and Prandtl layer turbine (after Ludwig Prandtl). Bioengineering researchers have referred to it as a multiple disk centrifugal pump.

[Furcifer]

If GE hasn't bought it it isn't worth buying.

When I get better access I'll check it out.

edit: the pic looks like it could be an impulse/reaction hybrid.

[casebro]

IF recursive prophet actually can sail down wind faster than the wind, I suppose the same technology (perpetual motion) could be used to built a fuel-less turbine.

[recursive prophet]

I'm dubious about flameholders working on the combustor section integrated into the disk at small size factors.

Also there's considerable efficiency loss in the movement of air (think momentum) sideways and then along the helical sections.

Finally, at small sizes friction forces predominate due to laminar flow which creates some scaling issues.

Generally, small is "way harder".

Thanks for the reply mhaze. One follow up question question for now; did you read all of the explanation on the PDF File? (https://docs.google.com/viewer?a=v&pid=gmail&attid=0.1&thid=12753a73642ecb31&mt=application%2Fpdf&url=https%3A%2F%2Fmail.google.com%2Fmail%2F%3Fui%3 D2%26ik%3D70c76a5c9b%26view%3Datt%26th%3D12753a736 42ecb31%26attid%3D0.1%26disp%3Dattd%26realattid%3D f_g6pbsblv0%26zw&sig=AHIEtbSaogTXm_PehiqtP2cE4zjFqX8z8Q&pli=1).

Didn't Nicola Tesla (http://en.wikipedia.org/wiki/Tesla_turbine) invent something like this?
I believe if you read the PDF linked above you'll see what is being proposed here is quite different from what Tesla had in mind.


If GE hasn't bought it it isn't worth buying.

When I get better access I'll check it out.

edit: the pic looks like it could be an impulse/reaction hybrid.
This was only released this morning 3bod. Perhaps GE will be interested. ;)

IF recursive prophet actually can sail down wind faster than the wind, I suppose the same technology (perpetual motion) could be used to built a fuel-less turbine.

Actually, I'm one of the very few still a tiny bit skeptical about going ddwfttw casebro, and am looking forward to the NALSA test in a couple months. But I can tell you this topic was discussed for over 3k replies here on JREF, and only 2 people-humber and Christoph-remained unconvinced. Ask sol invictus or Dan_O about it, or look for yourself where it began here. -- http://forums.randi.org/showthread.php?t=128483

[Fnord]

I believe if you read the PDF linked above you'll see what is being proposed here is quite different from what Tesla had in mind.
.
Well then, build it and give a demonstration.

Use of concept is proof of concept.

[Ziggurat]

IF recursive prophet actually can sail down wind faster than the wind, I suppose the same technology (perpetual motion) could be used to built a fuel-less turbine.

That's not perpetual motion. There is a clear source of energy (the velocity differential between the ground and air), and driving the vehicle acts to decrease that source of energy.

Oh, and this turbine design isn't fuel-less either. I have no idea about its practicality, but they aren't claiming a fuel-less design, nor are they claiming to be able to beat thermodynamic efficiency limits.

[ben m]

OK, looking at the PDF in more detail I'm now able to tell where the gas is going and generally "how the thing works". I still can't tell what makes you think that this way of doing it is a good idea. On the good side, you've confined all of the combustion to the interior of the rotor, and thermally-insulated that against the rest of the device. On the bad side:

Well, it just doesn't look like a whole lot of torque gets imparted to the rotor. I have a hard time imagining that the big screens, and the long flow paths towards and away from them, aren't a big constriction. Why not shrink the input channels, expand the exhaust channels, and let all the combustion happen way out at the edge? If you have numerical fluid mechanics to tell me I'm wrong, please let me know. But my amateur eyeball analysis doesn't see it.

[Furcifer]

I'm going to upload the pdf to my computer and read it again, but it claims efficiency of 50%, that's typical for a GT. Lower operating temps don't do much for combined cycle either. I have to take another look at the TS graphs for the Brayton cycle, but I swear higher temps are more efficient. Then again the claim is lower compression needs so that may more than balance out, 2/3 of turbine energy goes into the compressor.

I believe new GT combined cycles are getting near 80% efficiency so I'm not sure what the claim here is other than lower temps mean less wear and less exotic alloys ie; cheaper. That's about all I've got for now. It is interesting though, will read more.

[recursive prophet]

.
Well then, build it and give a demonstration.

Use of concept is proof of concept.
I have seen a few working prototypes of this design, and I can tell you putting together some good videos to post on YouTube is a high priority. I’m hoping they can have something up by April. This is still in the developmental stage, and right now John has many things pressing on this time. But you make a very valid point; thanks. It has been built, and the public demonstration will soon come. My purpose in posting this here, however, is primarily aimed at getting input on the concept itself.

That's not perpetual motion. There is a clear source of energy (the velocity differential between the ground and air), and driving the vehicle acts to decrease that source of energy.

Oh, and this turbine design isn't fuel-less either. I have no idea about its practicality, but they aren't claiming a fuel-less design, nor are they claiming to be able to beat thermodynamic efficiency limits.
Thanks so much for the clarifications Zig. If fact no claims are made about efficiency, and higher efficiency isn’t what the XpoTurbines have to offer. It’s all about cost per unit of work.

OK, looking at the PDF in more detail I'm now able to tell where the gas is going and generally "how the thing works". I still can't tell what makes you think that this way of doing it is a good idea. On the good side, you've confined all of the combustion to the interior of the rotor, and thermally-insulated that against the rest of the device. On the bad side:

Well, it just doesn't look like a whole lot of torque gets imparted to the rotor. I have a hard time imagining that the big screens, and the long flow paths towards and away from them, aren't a big constriction. Why not shrink the input channels, expand the exhaust channels, and let all the combustion happen way out at the edge? If you have numerical fluid mechanics to tell me I'm wrong, please let me know. But my amateur eyeball analysis doesn't see it.

He does, and I’m waiting for his written reply. He explained it by phone, but I’m afraid to try and paraphrase his response. I can only say that most who have commented seem to primarily be looking at XT from an efficiency viewpoint. Think instead in terms of the advantages of smaller units and cost reductions in materials etc. that ensue. But sincere thanks for your detailed critique. A sufficient reply will soon be posted here. Sorry I somehow missed your earlier reply. I have tried to emphasize to John-the inventor-that his intro needs a lot of work. Inventers are not by nature good pitch-men, Edison aside.

I'm going to upload the pdf to my computer and read it again, but it claims efficiency of 50%, that's typical for a GT. Lower operating temps don't do much for combined cycle either. I have to take another look at the TS graphs for the Brayton cycle, but I swear higher temps are more efficient. Then again the claim is lower compression needs so that may more than balance out, 2/3 of turbine energy goes into the compressor.

I believe new GT combined cycles are getting near 80% efficiency so I'm not sure what the claim here is other than lower temps mean less wear and less exotic alloys ie; cheaper. That's about all I've got for now. It is interesting though, will read more.

Thanks for taking the time to look closer at the PDF 3bod, and I would value your analysis when you have time. Again there are NO claims made wrt any efficiency and that isn’t the key potential contribution of the XT family. It reminds me of another successful invention of his; a portable foam hot tub that has minimal losses and derives it’s heat from a coil wrapped around the pump motor that powers the massage jets. If one just looks at the speed and efficiency per BTU in heating the water, it wasn’t very efficient. It takes over a day or so to get the water up to the desired temperature. But then you can have it available for use 24/7 at a much lower cost than it takes to heat the water just a few times per month in a standard hot tub.

[Furcifer]

No problem RP. I'll try to get some of the other Power Engineers at work to take a look as well, I'm sure they'll be interested. Maybe I'll run off a copy of the pdf. and pass it around at the next IPE meeting.

[Christian Klippel]

Think instead in terms of the advantages of smaller units and cost reductions in materials etc. that ensue.

....

Again there are NO claims made wrt any efficiency and that isn’t the key potential contribution of the XT family.

Hmm, i'm curious what the overall gain is then? I mean, producing smaller/cheaper units is one thing, but if these units are not at least as efficient as normal ones, i don't see any gain in the long run.

Let me give an exaggerated example:
You build a turbine for half the cost & somewhat smaller size than regular ones. But that sucker needs twice as much fuel to do the same work. Sure, initially you are cheaper. But in the long run, you pay much more because of the increased fuel consumption.

So, i think that numbers about efficiency are quite important here. Just reducing the unit cost is only a very short term benefit. Once the fuel and operating costs kick in, you have to consider these factors as well.

Greetings,

Chris

[Lithrael]

Hmm, i'm curious what the overall gain is then? I mean, producing smaller/cheaper units is one thing, but if these units are not at least as efficient as normal ones, i don't see any gain in the long run.

There's always a place for smaller stuff, though. Any application where you're trying to conserve space or weight, for example.

[a_unique_person]

Hmm, i'm curious what the overall gain is then? I mean, producing smaller/cheaper units is one thing, but if these units are not at least as efficient as normal ones, i don't see any gain in the long run.

Let me give an exaggerated example:
You build a turbine for half the cost & somewhat smaller size than regular ones. But that sucker needs twice as much fuel to do the same work. Sure, initially you are cheaper. But in the long run, you pay much more because of the increased fuel consumption.


Greetings,

Chris

A lot of business models run on that idea, shifting future costs onto the buyer. Multi story building towers made with floor to ceiling glass windows. Cheaper to build, much more expensive to run. Doesn't seem to bother anyone.

[recursive prophet]

@3bod: Thanks for your interest; greatly appreciated. I had a long conversation with John Popovich this afternoon. He said while he is busy drawing charts and graphs for publication in a few Tech journals and lacks the time to type out explanations on the internet, for any who have read the PDF file and have specific questions, just give him a call. His number is listed at the bottom of his web page, and will be happy to explain how conservation of momentum comes into play here, along with how high pressure is effectively replaced by heat regeneration ratios and parallel processing. Sorry I can’t do better than this for now, but I need to spend some doing some advanced google and wiki-searches before I can feel comfortable relaying his thoughts.

I should mention my experience with the inventor goes back to 1965 at UCLA. It was the annual meeting of the International Solar Energy Society, (ISES) and an engineer I knew from San Diego Gas and Electric’s Solar Division told me he had just seen the future of flat plate collectors and dragged me to JP’s booth. I won’t go into details, but at a much later workshop I conducted on testing collectors with ERDA funding, I saw him convince the crème of the radiation physics docs in solar just how many things they had missed in developing their standards. Give him a call. I think you’ll be blown away.

Hmm, i'm curious what the overall gain is then? I mean, producing smaller/cheaper units is one thing, but if these units are not at least as efficient as normal ones, i don't see any gain in the long run.

Let me give an exaggerated example:
You build a turbine for half the cost & somewhat smaller size than regular ones. But that sucker needs twice as much fuel to do the same work. Sure, initially you are cheaper. But in the long run, you pay much more because of the increased fuel consumption.

So, i think that numbers about efficiency are quite important here. Just reducing the unit cost is only a very short term benefit. Once the fuel and operating costs kick in, you have to consider these factors as well.

Greetings,

Chris

@Chris: Yo dude! Really miss reading your hilarious comments on the ddwfttw thread here, and sure wish you’d rejoin the fun at TR-just use the link in my sig and check it out. JB and spork will be showing an enormous, drivable cart to NALSA out in Nevada next week to see what will be required to test it. Great suspense, with lots of videos and more to come.

As to your question, what if your cost was less than half and efficiency a very small percentage lower? Not saying that’s the case, as John believes the efficiency will in many cases exceed existing turbines. Do read the PDF carefully. It’s long I know, but I believe it will answer most of your questions. Hope what I’ve posted below from the PDF will fuel your interest. There are aspects of this similar to the angular momentum of spork’s cart. Hope this helps, and thanks for your interest.

"Efficiency: efficiency decreases generally with decreasing scale but the loss mechanisms associated with scale reduction can be mitigated in XpoTurbine engine design. Engine efficiency can be increased by increasing the pressure and temperature ratios. XpoTurbines can be designed to operate with a wide range of pressure and temperature ratios, but there is another possible avenue of design that allows high efficiency without high‐pressure temperature ratios. The XpoTurbine engines described pursue this avenue.

Thermally regenerative Brayton cycle engines INCREASE in efficiency with decreasing pressure ratio and this allows reduced component mass, stress, and cost.

Thermal regeneration in XpoTurbines is provided by intake and exhaust flow heat exchange and by exhaust gas recirculation. Engine efficiency returns diminish with increasing temperature ratios and the material costs and heat
losses increase. High pressure ratios also cause the air entering the combustion region to be at a high temperature from compression and the temperature rise from combustion must be added to this. Xpoturbines can use low pressure ratios and catalytic combustion to reduce the maximum temperature and thereby reduce component stresses, component costs, and heat losses.

Assuming an ambient temperature of 300°K and a 300°K temperature rise to 600°K the theoretical maximum efficiency is 50% (600°K‐300°K/600°K=0.5) and the proportion of the theoretical efficiency realized can be higher than would be the case with higher maximum operating temperatures because the heat losses Fare less and the choice of materials and processes used in construction allow further heat loss reductions. Reduced operating temperatures, vacuum insulation and low emission surfaces also allow Xpoturbines to be more easily incorporated into consumer products.

Controlled porosity passages: The degree of shear force usage can be varied by the incorporation of porous elements which can be used to exchange work between the fluid and the rotor, increase surface area for heat exchange, enhance mixing, provide catalyst support, act as flameholder, and provide structural communication. Planar wire cloth (screen) rotors with intake and exhaust flows in the plane of the screen can be used to provide a large heat transfer area in a compact system. (S Fi See Fig.11) Porous passage walls normal to the plane of the system may be of spiral form and may be made to lead or lag the flow spiral pattern that would be created by the enclosure surfaces without walls. On the compressor side where the
rotor velocity exceeds the flow velocity and the rotor is transporting work to the fluid, the spiral/s may be “faster” than the unimpeded flow path and thereby increase outward forces.

Controlled porosity elements can be used to divide the flow stream into a large population of small streams and thereby reduce the diffusion path length for heat and mass transport and the consequent time required for mixing, heat transport, catalysis, and combustion.

Consider an engine with an entry cross‐sectional area of 1cm2 (0.2cmX5cm) and 20 passage walls of spiral form, each with a porous catalyst region near the perimeter of 0.2cm in height X 2.5cm in length for a total cross‐sectional area of 0.2X2.5X20=10cm2. If the passage walls are composed of stainless steel wire cloth with 20 wires per/cm spacing in the warp and woof axis, 0.014cm diameter wire, and 50% open area, the flow cross‐sectional area will be increased by a factor of 5 and the number of flow passages will be increased to 4000 (20X20X10cm=4000). Further increase in cross‐sectional area is possible by corrugating the porous walls in this region. The flow will also be reduced in velocity in proportion to the radius ratio between the inlet radius and the local radius at the passage wall divided by the increase in the temperature ratio. The division of the flow into a large population of small flows allows combustion to take place in a very short time period, as diffusion of heat and mass is proportional to the square of the travel distance (l2). Copper or stainless steel screens can be nickel plated and further plated/coated by catalyst media such as Palladium for methane combustion or Platinum for propane combustion. (See Fig.3)

Porous elements can also provide structural communication, prevent dissipative secondary flows by energizing boundary layers, and reduce the drag associated with heat and mass transport processes. Wire cloth used to mfr passage walls can be bias cut at 45 degrees to minimize edge effects associated with processing and to reduce drag by presenting more optimal passage form to the flow. The wire cloth can then be selectively plastically deformed by pressing or rolling to reduce warping and to vary porosity.

[ben m]

Hmm, i'm curious what the overall gain is then? I mean, producing smaller/cheaper units is one thing, but if these units are not at least as efficient as normal ones, i don't see any gain in the long run.

You should take the "cheaper units" thing with a grain of salt to begin with. I don't see the existing plan as having anywhere near enough detail to be able to translate into a cost-per-unit. The idea of "lightweight = low materials cost" is irrelevant---turbines aren't expensive because they use lots of pounds of commodity steel, they're expensive because of all the precision tooling. Your design has all sorts of very weird tooling---the rotor, for example isn't a simple casting; in fact it looks like a welder's worst nightmare. Then you enclose it in a thin-wall chamber that needs to sustain high vacuum, high-speed rotation, and a large temperature differential. That all goes onto a weird, nonstandard high-speed bearing with multiple rotating couplings for various high-temperature and high-pressure fluids. Jeez. All of that is doable, but none of it is cheap.

On what grounds does this thing get pitched as a low cost turbine?

So, i think that numbers about efficiency are quite important here. Just reducing the unit cost is only a very short term benefit. Once the fuel and operating costs kick in, you have to consider these factors as well.


If you build a microturbine that can work in a combined-heat-and-power setting, then to some extent its efficiency doesn't matter. Imagine having the choice between (a) heating your house with a 10 kW gas burner, or (b) heating your house with a 10 kW gas turbine that happens to produce 1000W of electricity on the side. All else being equal, the latter is a better choice *even though* that happens to be an absurdly low efficiency.

[ben m]

It reminds me of another successful invention of his; a portable foam hot tub that has minimal losses and derives it’s heat from a coil wrapped around the pump motor that powers the massage jets. If one just looks at the speed and efficiency per BTU in heating the water, it wasn’t very efficient. It takes over a day or so to get the water up to the desired temperature. But then you can have it available for use 24/7 at a much lower cost than it takes to heat the water just a few times per month in a standard hot tub.

RP, I know you're presenting this as an example of "this is a really clever engineer" but this is a particularly bad example of a fallacy about heating and energy efficiency. The power required to keep a tub warm depends only on the insulation---the rate of heat loss through the walls. The heat loss through the walls also determines how long it takes the tub to cool down on its own if you turn the heating system off. The way it works out: it always takes more energy to keep a warm thing on "standby" all the time than it does to warm it up for use and turn off the heaters when it's not in use. Always. It doesn't feel that way intuitively---you're always thinking, "wow, it takes so much energy to get the water hot to begin with, I'd better try to avoid that heating step"---but that's not how it works. (For an analogy with identical math: imagine that you have a bucket with a small hole in the bottom. The fuller the bucket is, the faster water sprays out the hole. You obviously consume more water if you try to keep the bucket full all the time, versus if you let it drain when not in use and do the "extra" work refilling it when you need it.)

(There was an article in the Times once where someone in Arizona complained about how it was so expensive to air-condition their home---so they left the AC on all day (!) so they wouldn't have to blast it in the evenings (!!). If there was a way to throw things at a Web page I would have done it.)

Your friend has invented an insulated tub---good for him---and is heating it with waste heat---also good. But since he's leaving the "waste heat" source on all the time, it's not a waste heat source, it's just a heater; he's actually wasting energy. And he's accumulating wear on an expensive component (a motor) rather than a cheap one (a resistive heating element). These two mistakes do not give me confidence that this person is designing a workable turbine at all, nor that he's thought through the manufacturing and/or lifetime costs of the thing.

[recursive prophet]

Your friend has invented an insulated tub---good for him---and is heating it with waste heat---also good. But since he's leaving the "waste heat" source on all the time, it's not a waste heat source, it's just a heater; he's actually wasting energy. And he's accumulating wear on an expensive component (a motor) rather than a cheap one (a resistive heating element). These two mistakes do not give me confidence that this person is designing a workable turbine at all, nor that he's thought through the manufacturing and/or lifetime costs of the thing.

As to the hot tub Ben, I shouldn’t have brought it up as I don’t have the time or motivation to go into details. That was over 20 years ago, and he long ago sold his interest in the company he started to develop it. I will just say that the water circulating in the coil around the pump kept it cool enough while eliminating all the heat loss of those using a fan. Also, the tub came with a thick highly insulating lid, and the pump did not need to run that often to maintain temperature. The main advantage was that the cost of having it available 24/7-a major convenience if you’ve ever owned a hot tub-was lower than heating a conventional unit just a few times a month. And his was just one of many inventions he has developed over the years. I mentioned it because of its simplicity and the efficient conservation of energy that I saw in other projects of his as well. But you raise an interesting point about the pumps, and I’m not sure if anyone later looked into their life span and how this would affect the tubs economic benefits.

Thanks for the critique, especially the reply to Chris. Questions skeptics such as you have is exactly what I'm looking for. I only wish I felt comfortable in attempting to respond to them at this point. Remember, John only finished the PDF file explaining the XT last Saturday. I will need to go over it several more times, as I lack the physics background to comprehend it all without much help from wiki, and other commitments have prevented me from doing so. If you have read the entire PDF and still have the same concerns, below are some links to relevant research in this area. He sent 5, but 3 required paid subscriptions so I didn’t post them. If you still have reservations, do give him a call at the number given on his website. I for one would be very interested in what insights such a direct conversation might produce, on both ends.

CFD IN THE DESIGN OF AN ULTRA MICRO GAS TURBINE COMBUSTION CHAMBER (http://www.onera.fr/eucass/2005/Proceedings/5.08.07.pdf)

Aero-Thermal Research Particulars in Ultra-Micro Gas Turbines (http://ftp.rta.nato.int/public//PubFullText/RTO/EN/RTO-EN-AVT-131///EN-AVT-131-03.pdf)

[Furcifer]

So, i think that numbers about efficiency are quite important here. Just reducing the unit cost is only a very short term benefit. Once the fuel and operating costs kick in, you have to consider these factors as well.

Greetings,

Chris


Efficiency has always been the drawback of using turbines. High output to weight ratio and reliability are the biggest reasons to consider them in applications. You wouldn't typically consider using a turbine where efficiency is your main consideration.

[Christian Klippel]

Efficiency has always been the drawback of using turbines. High output to weight ratio and reliability are the biggest reasons to consider them in applications. You wouldn't typically consider using a turbine where efficiency is your main consideration.

Right. But i was referring to a comparison of the efficiency of existing turbines to the proposed one. If the efficiency is considerably less, at a given output power, compared to an existing unit, the savings in material/production cost gets eaten up very quickly by the cost for fuel. In such a case i simply don't see any benefit to already existing units.

Sure, the size factor may be important, but then again, it should be compared to existing units, i think. Like, i could produce paper bags that cost only half the price of the others. Sure, the thickness of the paper would be only one quarter of that used by regular bags. So you can put much less goods in it, requiring you to buy twice as much bags at least. So, while a single bag would be cheaper then, there is no net gain for the consumer.

Greetings,

Chris

[tsig]

Thanks for the reply mhaze. One follow up question question for now; did you read all of the explanation on the PDF File? (https://docs.google.com/viewer?a=v&pid=gmail&attid=0.1&thid=12753a73642ecb31&mt=application%2Fpdf&url=https%3A%2F%2Fmail.google.com%2Fmail%2F%3Fui%3 D2%26ik%3D70c76a5c9b%26view%3Datt%26th%3D12753a736 42ecb31%26attid%3D0.1%26disp%3Dattd%26realattid%3D f_g6pbsblv0%26zw&sig=AHIEtbSaogTXm_PehiqtP2cE4zjFqX8z8Q&pli=1).


I believe if you read the PDF linked above you'll see what is being proposed here is quite different from what Tesla had in mind.



This was only released this morning 3bod. Perhaps GE will be interested. ;)



Actually, I'm one of the very few still a tiny bit skeptical about going ddwfttw casebro, and am looking forward to the NALSA test in a couple months. But I can tell you this topic was discussed for over 3k replies here on JREF, and only 2 people-humber and Christoph-remained unconvinced. Ask sol invictus or Dan_O about it, or look for yourself where it began here. -- http://forums.randi.org/showthread.php?t=128483

Wrong

[Furcifer]

Right. But i was referring to a comparison of the efficiency of existing turbines to the proposed one. If the efficiency is considerably less, at a given output power, compared to an existing unit, the savings in material/production cost gets eaten up very quickly by the cost for fuel. In such a case i simply don't see any benefit to already existing units.

Sure, the size factor may be important, but then again, it should be compared to existing units, i think. Like, i could produce paper bags that cost only half the price of the others. Sure, the thickness of the paper would be only one quarter of that used by regular bags. So you can put much less goods in it, requiring you to buy twice as much bags at least. So, while a single bag would be cheaper then, there is no net gain for the consumer.

Greetings,

Chris

They function like any other turbine using the Brayton cycle so they have the same theoretical efficiencies.

[sol invictus]

IF recursive prophet actually can sail down wind faster than the wind, I suppose the same technology (perpetual motion) could be used to built a fuel-less turbine.

How is a wind powered vehicle "perpetual motion"? It only works when there's wind, and wind is powered by the sun - which will eventually go out.

If you think it's impossible to beat the wind to a downwind point for some mechanical reason, well... you're wrong. Land and ice sailors do it routinely, and fast sailboats can do it too.

[recursive prophet]

@tsig-Yo T-indeed I was wrong and I apologize. I think I forgot about you still being active here as most of your posts I read on ddwfttw were at TR. Sorry. You should come back. Harold has dropped out and humber could use some support. Big weekend in Cartville. I suspect they aren't ready for prime time.

Any thoughts on the XT? The presentation needs work, but the concept has a lot of promise IMHO.

@3bod: Thanks for the explanation. Brayton cycles are one of many things I need to read up on. Did you ever show the PDF to the engineers at your job? I would really appreciate any critiques, and as I've mentioned you can actually contact the inventor via the number on the website.

@Ol Sol Invictus; been a while good sir. I've been meaning to send you a PM and ask you to take a look at this. You're far better at finding flaws in new concepts than most, and I'd love to read your analysis of this one. (Oh,and if a NALSA video is posted I'll PM you a link. I'm betting it ain't gonna happen. Too many drive/stability problems; not enough time.

[Furcifer]

I didn't have a chance yet. Probably next week. I did bring it up with a friend and told him to check it out. He mentioned the same thing I had, that GT turbines are typically running at higher temps for maximum efficiency. The alloys they use in the turbines today are some of the most exotic metals on earth because of this. We don't evem have the rods to weld them. The manufacturer typically sends you an unmarked rod at your request, if they can be repaired at all. The idea of lower temperature turbine with less exotic metal seems very appealing. I'm sure the guys will be interested but highly skeptical. Or maybe not, I'll let you know.

[MRC_Hans]

Have downloaded pdf. Will read and comment. Later.

Hans

[MRC_Hans]

OK, I have read through it. I must admit that my scam indicator went right into red.

The last few lines are a heavy scam indicator:

XpoTurbine technologies are proprietary and the property of John Popovich.


The technologies have patents pending status and are available for licensing and partnering.

Developers kits are available.

That is usually what people write when trying to scam investment money.

When we look at the product, I haven't gone enough into it to have an opinion on whether the principle is viable, but many of the features you list are mutually exclusive, for example high power density and ability to work in a low temperature differential: The principle may be adaptable to both, but not in the same device.

Hans

[Furcifer]

When we look at the product, I haven't gone enough into it to have an opinion on whether the principle is viable, but many of the features you list are mutually exclusive, for example high power density and ability to work in a low temperature differential: The principle may be adaptable to both, but not in the same device.
Hans

Power density is an inherent property of turbines, usually offset by their inefficiency. Relative to another prime mover in the same application ie; a low temperature differential, a turbine is still going to have a higher power density.
In this case we're talking about comparing the Brayton cycle and say the Otto or Rankin cycle.

[MRC_Hans]

Mmm, I think that turbines have a far from linear response to flow speeds and hence pressure differentials. Whereas many primary movers are fairly linear, at least in a given range. So I don't think the density advantage for turbines is true for all ranges.

Anyhow, I was challenging the sweeping statements given in the text, and pointing out that these devices will have a lot of compromizes, like any other device.

If you list only the strong sides of many different optimisations, you may list the same advantages for many other devices, but that is dishonest.

Hans

[recursive prophet]

@3bod and Hans: Thanks for your comments. As I mentioned in the OP the PDF file posted on the website is a work in progress, and all analysis as to it's strengths and weaknesses is appreciated and helpful.

The inventor's top priority right now is completion of some drawings and a video of one of his prototypes running. The explanation of it's advantages definitely needs work, and to be shortened. I will pass on that potential disadvantages should also be noted though; good point Hans. :)

[MRC_Hans]

@3bod and Hans: Thanks for your comments. As I mentioned in the OP the PDF file posted on the website is a work in progress, and all analysis as to it's strengths and weaknesses is appreciated and helpful.

The inventor's top priority right now is completion of some drawings and a video of one of his prototypes running. The explanation of it's advantages definitely needs work, and to be shortened. I will pass on that potential disadvantages should also be noted though; good point Hans. :)

Thx, however, my main point, which I may not have expressed explicitly, is:

**** the pretty presentations and drawings. Make some prototypes and show that they work. That will impress the world. Anyone can make pretty presentations.

Hans

[ben m]

The inventor's top priority right now is completion of some drawings and a video of one of his prototypes running. The explanation of it's advantages definitely needs work, and to be shortened. I will pass on that potential disadvantages should also be noted though; good point Hans. :)

Hello RP,

As for me, I'd say that I don't need "explanation of its advantages"---I need

a) evidence that this design actually has the advantages the inventor says that it has. A prototype experiment is a good start, but unlike MRC I'd actually be *more* convinced by a competent CFD numerical simulation. The numerical model allows you to see the scaling laws---"will this be better or worse if I scale down by a factor 2"---and it allows you to separate the fundamental behavior of the gas from the specific compromises you made in building the prototype. (It's very easy to build a garage-workshop-quality prototype, find that it coughs along at 2% efficiency, and say, "Look it works! Pay no attention to the performance, I blame that on the bearings and the inlet piping and etc. etc. I bet the polished-up version will be 30% efficient." That's not convincing. Of course if the garage-workshop-quality results are impressive on their own---as MRC Hans says, that speaks for itself!)

b) Comparison of this design's properties to the state of the art. You don't just want to say, "Here is the efficiency-vs-power curve, here is the weight, here is the estimated cost per unit, here is the fuel cost per joule of output, here is the speed at no load" (or whatever is on the list of things one asks about a turbine). Then pick three competing technologies for the same application---piston engines, microturbines, fuel cells, batteries, whatever---and line up all of those properties in a matrix. Be scrupulously honest on this; if you've got a hoped-for number that you aren't sure you can achieve, say so and put both an optimistic and a pessimistic value into your table.

[recursive prophet]

Thanks again for the input guys. John does read this thread, and I'm sure some of your suggestions here will be helpful. As I mentioned before though, his first priority right now is getting some good pictures and and videos of some of the prototypes in action.

As I am unable to adequately answer many of the questions put forth here, I will not respond further until the inventor has time to provide more guidance on the issues already raised, and hopefully some YT videos of the XpoTurbine in action.

Again thanks to all who have taken the time to read and comment on this idea. Your time was much appreciated and I hope others do likewise. Just understand it may take a while before you get any significant feedback from John Popovich. I will say I've known him for nearly 40 years, and have been to his incredible shop just off the ocean in Solana Beach slightly north of Del Mar. He has made his living through licencing agreements of his patents for many years now, and I've known highly regarded experts in various fields who have been quite impressed with his past work. This said, whether or not the XT is really the breakthrough he believes it to be is sadly beyond my capacity to evaluate. Hopefully that will change in the near future.

[Furcifer]

The design seems to be like a pinwheel, as the fluid expands through the passages like a typical reaction turbine it passes through the disc and then exhausts. If I'm correct, multistage designs would use and axial arrangement.
I'd be cautious of the porousity claims. Even natural gas has its impurities, it seems the design would be prone to clogging. Especially with biofuels or other less pure combustibles.
Just an observation.