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Thread: A work of pure genius! - Brilliant "Revetec" Engine

  1. #1306
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    Brad, using the X4v2 are Peus looking at about 10 (units/apartments) per Engine?
    Do you know what fuel they are testing or thinking of running on?
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  2. #1307
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    Quote Originally Posted by hightower99 View Post
    Nope it doesn't convince me when a single company produces a single published result under odd conditions.
    Odd conditions?
    It was tested at the normal speed and load an engine experiences at cruise up a slight gradient 18kW@2,000RPM which is the point where engines are at there most efficient on a BMEP chart, where fuel efficiency is most important to the end user, and where almost everyone quotes their highest efficiency.

    Quote Originally Posted by hightower99 View Post
    The average efficiency wasn't explored over a wide range of conditions. I am 100% certain that a conventional engine could be designed to produce exactly the same result under the same conditions.
    The cylinder heads were designed by me and built, all under 2 weeks with no analysis performed. We have never claimed our engine (especially our cylinder heads) is at peak efficiency at the moment, and this will be achieved in the near future.

    If you are 100% certain that a conventional engine can be designed to produce this figure somone would have, so, post from any independent testing that a gasoline engine has achieved a better result in the tested range. It is simple to disprove me if you are correct.

    Quote Originally Posted by hightower99 View Post
    Sorry I don't buy that at all. The Diesel cycle is less efficient, given equal compression ratio, than modern Otto/Petrol cycle. Yet a diesel cycle engine has achieved 50% thermal efficiency.
    Great quote! So you are comparing a diesel engine with the same compression ratio as a gasoline engine. What is the point of that statement? A diesel is compression ignition which requires a higher compression ratio to generate enough compression heat to fire, and of course it won't operate efficiently at a compression ratio it was not designed to operate at. I am very suprised at the naivity of this quote.

    Quote Originally Posted by hightower99 View Post
    I don't believe an industry-wide unanimous agreement on an arbitrary 37% limit actually exists. Rather I would believe that some would find the results you are able to show to be insufficient/inconclusive. What could that limit possibly be based on? Who actually agrees with that limit?
    I think you should do some research on the theoretical thermal efficiency limits of gasoline engines matter and post them here with the reference website, rather than you opinion. I invite you to do so.

    Achieving a BSFC of 207g/(kW-h) in actual independent testing is conclusive. Our engine achieved this result.

    I invite you to post anything to back up your statements with references from any reputable source, if you can't do this, then everything you have stated is your own opinion.

    BTW. What are your credentials in this area?

  3. #1308
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    Quote Originally Posted by henk4 View Post
    I am sure the diesel engine (given equal compression ratio) will be much more efficient than a petrol engine (WITHOUT A SPARK PLUG), because the higher compression ratio in diesel causes the ignition....so if you take away the ignition option for a diesel, it is only fair to do that also for a petrol engine, isn't it?
    Great quote Henk4.

  4. #1309
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    Quote Originally Posted by Revetec Raptor View Post
    Brad, using the X4v2 are Peus looking at about 10 (units/apartments) per Engine?
    Do you know what fuel they are testing or thinking of running on?
    Yes, multiple apartments. VW has already announced it will enter this market using their Jetta engine.

    The fuel available in this usage is natural gas.

  5. #1310
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    Quote Originally Posted by hightower99 View Post
    I don't believe an industry-wide unanimous agreement on an arbitrary 37% limit actually exists.
    Quote taken from Wikipedia - Subject: Internal Combustion Engines - Sub: Energy Efficiency

    Quote:"Engine efficiency can be discussed in a number of ways but it usually involves a comparison of the total chemical energy in the fuels, and the useful energy extracted from the fuels in the form of kinetic energy. The most fundamental and abstract discussion of engine efficiency is the thermodynamic limit for extracting energy from the fuel defined by a thermodynamic cycle. The most comprehensive is the empirical fuel efficiency of the total engine system for accomplishing a desired task; for example, the miles per gallon accumulated.

    Internal combustion engines are primarily heat engines and as such the phenomenon that limits their efficiency is described by thermodynamic cycles. None of these cycles exceed the limit defined by the Carnot cycle which states that the overall efficiency is dictated by the difference between the lower and upper operating temperatures of the engine. A terrestrial engine is usually and fundamentally limited by the upper thermal stability derived from the material used to make up the engine. All metals and alloys eventually melt or decompose and there is significant researching into ceramic materials that can be made with higher thermal stabilities and desirable structural properties. Higher thermal stability allows for greater temperature difference between the lower and upper operating temperatures thus greater thermodynamic efficiency.

    The thermodynamic limits assume that the engine is operating in ideal conditions: a frictionless world, ideal gases, perfect insulators, and operation at infinite time. The real world is substantially more complex and all the complexities reduce the efficiency. In addition, real engines run best at specific loads and rates as described by their power band. For example, a car cruising on a highway is usually operating significantly below its ideal load, because the engine is designed for the higher loads desired for rapid acceleration. The applications of engines are used as contributed drag on the total system reducing overall efficiency, such as wind resistance designs for vehicles. These and many other losses result in an engine's real-world fuel economy that is usually measured in the units of miles per gallon (or fuel consumption in liters per 100 kilometers) for automobiles. The miles in miles per gallon represents a meaningful amount of work and the volume of hydrocarbon implies a standard energy content.

    Most steel engines have a thermodynamic limit of 37%"

  6. #1311
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    Quote Originally Posted by revetec View Post
    Odd conditions?
    The parameters you quoted are all fine I was talking specifically about the conditions that the claimed peak efficiency was measured at, namely the odd A/F ratio of 15.2:1. It would be interesting to know what other conventional engines could achieve if tested at that A/F ratio under the same conditions.

    Quote Originally Posted by revetec
    The cylinder heads were designed by me and built, all under 2 weeks with no analysis performed.
    Surely you performed some initial analysis of the engine and the conditions it would run during testing. Did you just guess all the dimensions?

    Quote Originally Posted by revetec
    If you are 100% certain that a conventional engine can be designed to produce this figure somone would have, so, post from any independent testing that a gasoline engine has achieved a better result in the tested range.
    You are missing the point. The range of testing your engine underwent was highly limited and the rapport shows that other than the one very specific point, your engine wasn't overly efficient at all. My point is that it is much easier to make an engine that is designed to achieve peak efficiency at one very specific point compared to making an engine that has to achieve a high average efficiency over a wide range of conditions. I have no doubt that a conventional engine could be designed to beat your mark in those specific conditions but it would be rubbish under all other conditions.

    Quote Originally Posted by revetec
    So you are comparing a diesel engine with the same compression ratio as a gasoline engine. What is the point of that statement?
    Unfortunately it seems both you and Henk4 missed my point. I will break it down for you: Diesel engines have achieved a thermal efficiency just over 50%; The modern Otto cycle is more efficient than the Diesel cycle at any given compression ratio, granted a diesel engine can run at a higher static compression ratio then a Otto cycle based engine at current time; Current static compression limits on Otto based engines is largely limited by octane value of fuel burned, however technological progress has allowed increases in static compression without raising octane value; Several variable compression concepts show static compression as high as 20:1 under low load (comparable to diesel engines), Where does the 37% limit come from?

    Quote Originally Posted by revetec
    I think you should do some research on the theoretical thermal efficiency limits of gasoline engines matter and post them here with the reference website, rather than you opinion. I invite you to do so.
    I have done research and I never ran into the 37% limit, not once. That is why I invited you to explain where you got the idea but your answer was that is was common knowledge and a worldwide business agreement. I disagree with those statements. I could understand if 37% was the current top efficiency achieved in testing but your statement was that 37% was the absolute limit.

    Quote Originally Posted by revetec
    Achieving a BSFC of 207g/(kW-h) in actual independent testing is conclusive. Our engine achieved this result.
    Ah but conclusive of what? Your engine achieved high efficiency under a single set of conditions, so what? the average efficiency over the range of conditions tested was not good at all and certainly not convincing enough to prove that the revetec design is better than conventional designs, designed for high average efficiency over a wide set of conditions.

    Quote Originally Posted by revetec
    I invite you to post anything to back up your statements with references from any reputable source, if you can't do this, then everything you have stated is your own opinion.
    I think you will find that I make statements of disbelief and give you questions to answer. What statements should I backup? that I don't believe you? That I haven't seen what you say is all around? As far as I have found in my own looking into the subject, the actual physical limit of Otto based internal combustion engines has not been set to any fixed value. It has been limited insofar as it cannot exceed Carnot efficiency between the same heat sinks.

    Quote Originally Posted by revetec
    What are your credentials in this area?
    I wasn't aware that I needed any to discuss this with you? What credentials should I have? Bare in mind that I have no intention of going into a lab and performing experiments solely to disprove anything you say at the present. What credentials does one need to discuss one's opinions of another's statements?

    Quote Originally Posted by revetec via wikipedia
    Most steel engines have a thermodynamic limit of 37%
    Really? So your proof of your statement is a single, unreferenced line in a wikipedia article that seems to be grammatically incorrect. Shouldn't it be "All steel engines..." as opposed to "Most steel engines" if it is talking about a limit? Does the limit only apply to "steel engines" and what exactly constitutes a "steel engine"? I thought you said this was pretty much common knowledge and that your...

    Quote Originally Posted by revetec
    problem since is convincing the engine industry, as prior to our result it has been believed that a gasoline internal combustion engine has a maximum possible thermal efficiency of 37%.
    My questions stand.
    Last edited by hightower99; 07-31-2010 at 03:48 PM.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  7. #1312
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    Quote Originally Posted by hightower99 View Post
    I wasn't aware that I needed any to discuss this with you? What credentials should I have? Bare in mind that I have no intention of going into a lab and performing experiments solely to disprove anything you say at the present. What credentials does one need to discuss one's opinions of another's statements?
    Well.. T.C. you are a Chinese/Australian 17yo school student that has very limited experience in what you are talking about.

    When on a limited budget there is a structured way of testing we have to move through to prove our engine. We don't have $300 million to spend designing, prototyping, and testing like many large automotive companies do.

    To move the project forward we had to prove how efficient could we get this engine, even though we were under budget and time constraints.

    We picked the target point, I manually calculated the piston acceleration rates, torque application angles, cams, valve size and lift, and a whole other range of parameters, targeted at a mid sized car at 100kph under cruise and light load @2,000rpm.

    I then designed the engine to meet this criteria. Bare in mind the budget for the calculation, design, build to run was around AUD$350k with only 7 months to complete with myself and a machinist. The goal I set myself was set at 238g/(kW-h).

    We worked 16 hour days, and completed the engine in 6.5 months from start to finish. Inhouse testing proved the target figure under in-house testing. We then had to prove this figure under independent testing, so we sent the engine to Orbital.

    After more tuning (We had only run this engine for under 10 hours up to the point we sent it to Orbital) we achieved a best fuel efficiency of 207g/(kW-h) in independent testing.

    The next stage was to then seek a development partner with the right skills and equipment to then optimise the design to all operational ranges and conditions. Please bare in mind that the cylinder heads we designed purely "to fit". Now we are working with two specialist companies who are working on optimising the engines for production.

    The funny thing is that through the struggle to prove this technology, and people like yourself trying to disprove the technology in the past, I proved that the efficiency levels are higher than a conventional engine, and posted the results. Then everyone turned around and started hammering our company's performance. We now have signed two development and licensing deals to move into production, and young kids like yourself are still trying to disprove our achievements to date in efficiency. Kinda funny really, as we are now progressing towards production.

  8. #1313
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    Quote Originally Posted by hightower99 View Post
    Really? So your proof of your statement is a single, unreferenced line in a wikipedia article that seems to be grammatically incorrect. Shouldn't it be "All steel engines..." as opposed to "Most steel engines" if it is talking about a limit? Does the limit only apply to "steel engines" and what exactly constitutes a "steel engine"? I thought you said this was pretty much common knowledge and that your.
    Why don't you read the whole article. I suppose that Most steel engines includes Revetec. Steel engine is defined as made from metals as opposed to ceramics. Why don't you quote me being wrong from another reference source? After all a 17yo kid's comments on this doesn't hold weight against some of the world's most experienced engine authorities.

    Cheers

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    Quote Originally Posted by revetec View Post
    Well.. T.C. you are a Chinese/Australian 17yo school student that has very limited experience in what you are talking about.
    Ummm I'm confused are you talking about me? What does T.C. stand for? I am a 22yo Caucasian Canadian living in Denmark, attending university... and my initials are not T.C. So far my experience is enough to not get lost in anything you have talked about.

    Quote Originally Posted by revetec
    We picked the target point, I manually calculated the piston acceleration rates, torque application angles, cams, valve size and lift, and a whole other range of parameters, targeted at a mid sized car at 100kph under cruise and light load @2,000rpm.

    I then designed the engine to meet this criteria.
    So you did exactly what I suspected. You designed the engine to excel at this very specific set of conditions. I personally think that that was a mistake. Instead I would have designed the engine to be good under a wide set of conditions instead of excellent at one point FWIW. I believe that would be more easily and fairly comparable to conventional engines and show whether there is merit in the revetec design.

    Quote Originally Posted by revetec
    The funny thing is that through the struggle to prove this technology, and people like yourself trying to disprove the technology in the past, I proved that the efficiency levels are higher than a conventional engine, and posted the results. Then everyone turned around and started hammering our company's performance. We now have signed two development and licensing deals to move into production, and young kids like yourself are still trying to disprove our achievements to date in efficiency. Kinda funny really, as we are now progressing towards production.
    I am not trying to "disprove" your engine, simply stating that I have not been convinced. I wouldn't attack your work ethic or the resources you have put into the business. I still have doubts that revetec engines will make it into actual production (at least enough to not be worried about my wager).

    Quote Originally Posted by revetec
    Why don't you read the whole article. I suppose that Most steel engines includes Revetec. Steel engine is defined as made from metals as opposed to ceramics. Why don't you quote me being wrong from another reference source? After all a 17yo kid's comments on this doesn't hold weight against some of the world's most experienced engine authorities.
    Not only have I read that article some time ago I have also explored the references from the article.

    I can't exactly quote you being wrong as you are the one claiming a set limit whereas I have only seen the limiting factors which don't give a set limit. Do you want me to get a quote from an "engine authority" that states a maximum efficiency above 37%?

    I am not 17yo.

    Why haven't you shown one single quote from one of these "experienced engine authorities" claiming a maximum of 37%???
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  10. #1315
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    Quote Originally Posted by hightower99 View Post
    So you did exactly what I suspected. You designed the engine to excel at this very specific set of conditions. I personally think that that was a mistake. Instead I would have designed the engine to be good under a wide set of conditions instead of excellent at one point FWIW. I believe that would be more easily and fairly comparable to conventional engines and show whether there is merit in the revetec design.
    If I had the budget at the time to do, so I would have. It would have been great to have a larger capital budget and a longer timeframe to build that prototype, then we could have utilsed Computational fluid dynamics (CFD) in programs such as ANSYS to optimise the cylinder heads. Also we had to machine the heads on our 3 axis CNC mill. The original designs had the inlet ports at a different angle, but we could not physically machine the original design. So we compromised by changing the angle of the ports. In this next stage the heads will be redesigned using CFD and rapid prototyping, allowing us to optimise the heads to perform over a greater range of RPM and load conditions.

    One thing you may not understand is that at a University or large companies you have the resources in the way of software and test equipment that small businesses like ourselves simply don't have.

    One thing I am very proud of is that we made such an achievement on such a limited budget and equipment. The testing was a stepping stone towards attracting an experienced company in this field to take on the development of the engine to the next level it deserves. We have signed two licensing agreements and we are working on signing more at the moment. The more companies that get involved, the more experience and knowledge is poured into the development.

    Quote Originally Posted by hightower99 View Post
    I am not trying to "disprove" your engine, simply stating that I have not been convinced. I wouldn't attack your work ethic or the resources you have put into the business. I still have doubts that revetec engines will make it into actual production (at least enough to not be worried about my wager).
    We have signed two licensing agreements for engine production. These companies are now spending a lot of their own capital to develop and produce our engines. They wouldn't do this if the engine wasn't going into production. The engine is coming, and with the experience of Peus and Atalan Makine on board, the production engine will perform great in all areas you are identifying, and more.

    Quote Originally Posted by hightower99 View Post
    Not only have I read that article some time ago I have also explored the references from the article.

    I can't exactly quote you being wrong as you are the one claiming a set limit whereas I have only seen the limiting factors which don't give a set limit. Do you want me to get a quote from an "engine authority" that states a maximum efficiency above 37%?
    Fuel has a potential energy. An engine has frictional and pumping losses which can be measured. Engines have combustion pressures than can be measured in analysis software and in physical BMEP tests with sensors in the combustion chambers. You can measure heat loss from an engine. You can measure parasitic losses from ancillaries. We hopefully all know the Carnot cycle theory. Given all these tests it is stated that with the energy that gasoline has, and the losses experienced in an engine, that it is possible to achieve 37% efficiency if everything was operating at maximum efficiency.

    My theory is that the heat lost through the exhaust was not a total loss, and that the loss was the difference between heat lost in an engine minus the power produced.

    To explain, the heat produced the power. If we deduct the heat loss, then we must deduct the power that was produced by that heat. Then if you graph a crankshaft against a cylinder pressure graph, you experience losses, such as when the cylinder pressure is at its highest, it is around 15-25deg ATDC where the torque lever of a crankshaft is not very good, creating mechanical losses which do not show up in cranking friction and pumping loss tests. If we were able to produce a design that the torque was applied at right angles to the shaft all the way though the stroke, then it would be 100% efficient as a mechanical device. Of course this can't be achieved, but we can calculate the losses experienced from a crankshaft even though 100% is not achieveable.

    In the therory of engine thermal dynamics there is no room for the mechanical losses experienced from a crankshaft. This is why I challenged the theory. I designed an engine that has less mechanical losses than a crankshaft. When tested (and it doesn't matter what test conditions are used) we achieved 39.5%. Taking all engine losses as tested including friction, pumping and combustion losses we accounted for over 100% of losses+power in the equation. This means the thermal dynamic equation is wrong, as it is impossible to account for over 100% of fuels potential energy.

    So lets look at a jet engine. Air is compressed (compression losses) fuel is injected and ignited. We can measure the losses through the exhaust blades (slippage/waste) and then most of the heat is expelled through the thrust. If we were to consider that the heat lost out of the exhaust as a loss then a jet engine (gas turbine) can produce little power, and we know that the thrust energy is huge and can lift a jet aeroplane. The heat has expanded the gas which produces thrust. No heat - No thrust.

    The same thing happens in an internal combustion engine. Air is compressed, fuel is ignited. The difference is that instead of thrust, the pressure pushes on a piston. The heat lost out of the exhaust has already produced the pressure to push the piston, and produce power. No heat - No power.

    So if an engine achieves 30% efficiency and 37% of heat is lost out of the exhaust and cooling system, then we have lost 7%, not 37%.

    So take this 30% out of the equation and slot the 30% mechanical losses from the crankshaft into the equation and now it is correct. Now decrease the mechanical losses such as we have done and a greater than 37% efficiency is achieveable.

    Quote Originally Posted by hightower99 View Post
    Why haven't you shown one single quote from one of these "experienced engine authorities" claiming a maximum of 37%???
    Because I believe this to be incorrect, but for reasons that are different to yours.

    Cheers

  11. #1316
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    BTW. Many people have tried to recover energy lost through the exhaust through heat exchangers. MAN is one of the leading companies in this area. I personally have not seen any heat recovery system achieving 7% recovery. If 37% is lost through the exhaust then why cant anyone recover more energy. This gels in with my theory that the energy lost through the exhaust is not as high as commonly stated. And yes, this is a theory, but one I have proved there is a flaw in. To what degree of % is still unknown but I can theorise that it is close to what I have stated.

  12. #1317
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    Quote Originally Posted by hightower99 View Post
    Ummm I'm confused are you talking about me? What does T.C. stand for? I am a 22yo Caucasian Canadian living in Denmark, attending university... and my initials are not T.C. So far my experience is enough to not get lost in anything you have talked about.
    My mistake. There is a 17yo Chinese Australian student who's nickname is Hightower99 registered in deviantart website. What a coincident.

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    Quote Originally Posted by revetec View Post
    We have signed two licensing agreements for engine production. These companies are now spending a lot of their own capital to develop and produce our engines. They wouldn't do this if the engine wasn't going into production. The engine is coming, and with the experience of Peus and Atalan Makine on board, the production engine will perform great in all areas you are identifying, and more.
    Firstly R&D by a company does not always lead to serial production, regardless of the licensing agreement. It does look like AM has manufacturing facilities as well as some partners in Turkey, however I still have doubts as to the possibility of actual serial production.

    Quote Originally Posted by revetec
    Fuel has a potential energy. An engine has frictional and pumping losses which can be measured. Engines have combustion pressures than can be measured in analysis software and in physical BMEP tests with sensors in the combustion chambers. You can measure heat loss from an engine. You can measure parasitic losses from ancillaries. We hopefully all know the Carnot cycle theory. Given all these tests it is stated that with the energy that gasoline has, and the losses experienced in an engine, that it is possible to achieve 37% efficiency if everything was operating at maximum efficiency.
    My question is where has this (specifically the 37%) been stated??? What are the specific maximums for the different parameters stated in order to achieve this magical 37%??? I have read about all the stated parameters and I have never seen anyone other than you claim that given their respective minimums a gas powered engine can only achieve 37% efficiency.

    Quote Originally Posted by revetec
    My theory is that the heat lost through the exhaust was not a total loss, and that the loss was the difference between heat lost in an engine minus the power produced.
    That is just plain wrong. Any heat out the exhaust which isn't subsequently used to generate power in some way is lost. Subtracting the power from exhaust heat is subtracting it twice from the equation.

    Quote Originally Posted by revetec
    To explain, the heat produced the power. If we deduct the heat loss, then we must deduct the power that was produced by that heat.
    But that heat is there because it didn't produce any power! If it had produced power then the heat would not be there! This statement makes me think you have completely misunderstand how a heat engine works.

    Quote Originally Posted by revetec
    Then if you graph a crankshaft against a cylinder pressure graph, you experience losses, such as when the cylinder pressure is at its highest, it is around 15-25deg ATDC where the torque lever of a crankshaft is not very good, creating mechanical losses which do not show up in cranking friction and pumping loss tests.
    That exact test should be part of the mechanical advantage testing.

    Quote Originally Posted by revetec
    If we were able to produce a design that the torque was applied at right angles to the shaft all the way though the stroke, then it would be 100% efficient as a mechanical device. Of course this can't be achieved, but we can calculate the losses experienced from a crankshaft even though 100% is not achieveable.
    Actually even if the force was always at a right angle and maintained the same lever arm length it wouldn't achieve 100% mechanical efficiency (still friction and sealing losses)it would have 100% mechanical advantage for any given pressure profile though. Also this feat is possible and has already been achieved (ever really thought about a turbine?). There are also other designs that achieve this feat including a design I am working on myself.

    Quote Originally Posted by revetec
    In the therory of engine thermal dynamics there is no room for the mechanical losses experienced from a crankshaft.
    Yes there is actually. It just isn't expressed as a direct relationship between mechanical advantage and thermal loss, because that isn't really possible. Rather the lower than 100% mechanical advantage will show increased losses in the other parameters, like cylinder wall heat losses.

    Quote Originally Posted by revetec
    This is why I challenged the theory. I designed an engine that has less mechanical losses than a crankshaft. When tested (and it doesn't matter what test conditions are used) we achieved 39.5%. Taking all engine losses as tested including friction, pumping and combustion losses we accounted for over 100% of losses+power in the equation. This means the thermal dynamic equation is wrong, as it is impossible to account for over 100% of fuels potential energy.
    I would look at your equation. Maybe a loss is accounted for twice? Or the value was incorrectly included (decimal point in the wrong place). Also I might not be understanding what you mean properly. Do you mean that when you added the total losses to the power output of your engine you achieved a value that was higher than the total energy input from fuel? If that is the case there are two possible answers: A: you created a second order perpetual motion machine or B:You screwed up you initial equation. Psst... you only really need to look at B

    Quote Originally Posted by revetec
    So lets look at a jet engine. Air is compressed (compression losses) fuel is injected and ignited. We can measure the losses through the exhaust blades (slippage/waste) and then most of the heat is expelled through the thrust. If we were to consider that the heat lost out of the exhaust as a loss then a jet engine (gas turbine) can produce little power, and we know that the thrust energy is huge and can lift a jet aeroplane. The heat has expanded the gas which produces thrust. No heat - No thrust.
    You are mixing two very different thing here. You either have a gas turbine which is optimized to produce power at the shaft and therefore very little thrust from the exhaust or you have a jet engine which is optimized to produce power as thrust and therefore very little excess power at the shaft. A gas turbine is very much like a piston engine where you would count the heat lost in the exhaust as a total loss (after the turbine section, mind). Whereas with a jet engine you count the power as thrust (not shaft HP) and the exhaust heat is only partially lost. Alot of it is used to produce thrust but still a large portion is dumped to atmosphere, this is the waste.

    Quote Originally Posted by revetec
    The heat lost out of the exhaust has already produced the pressure to push the piston, and produce power. No heat - No power.
    No. Heat coming out the exhaust didn't produce any power at all. The power was produced inside the cylinder by heat that has been removed from the working fluid via expansion. Power is produced by converting heat to mechanical motion (ie kinetic energy).

    Quote Originally Posted by revetec
    So if an engine achieves 30% efficiency and 37% of heat is lost out of the exhaust and cooling system, then we have lost 7%, not 37%.
    Nope you did lose all 37% of the potential energy in the fuel as waste heat in the exhaust. In your quote you have accounted for 67% of the fuels energy, leaving only the final 33% to find.

    Quote Originally Posted by revetec
    So take this 30% out of the equation and slot the 30% mechanical losses from the crankshaft into the equation and now it is correct. Now decrease the mechanical losses such as we have done and a greater than 37% efficiency is achieveable.
    Wow there is alot of funny math and physics going on in this quote. Firstly the 30% mechanical advantage loss (meaning the crankshaft has a mechanical advantage of 70%) is not directly equatable to a thermal loss. Any thermal losses have already been accounted for through the other parameters the lower mechanical advantage has just allowed those losses to be greater. Also this quote seems to show that you indeed believe in a maximum efficiency of 37% but only for engines using conventional crankshafts, is that correct?

    Quote Originally Posted by revetec
    Because I believe this to be incorrect, but for reasons that are different to yours.
    But we aren't discussing the validity of the actual 37% statement (it is plainly and blatantly incorrect). We are discussing whether anyone other than you ever said it. We are discussing whether or not it is an established view in the minds of engine authorities worldwide. In which case it should be exceedingly easy for you to show a quote from some established engine authority stating the theoretical maximum thermal efficiency of a gas powered four stroke engine is 37%. All I say is that you can't actually do that.

    Quote Originally Posted by revetec
    Many people have tried to recover energy lost through the exhaust through heat exchangers. MAN is one of the leading companies in this area. I personally have not seen any heat recovery system achieving 7% recovery. If 37% is lost through the exhaust then why cant anyone recover more energy.
    Ok a few questions for you: Where does this 37% value for heat lost through exhaust come from? Where do you think turbochargers get the energy required to compress intake air?

    It looks like you have never looked into turbo-charging as it can be clearly shown in a myriad of setups that turbochargers use more than 7% of total energy input. Also I would point you to BMW's proposed concept for exhaust heat recovery called the turbosteamer I believe. Apparently it captures more than 80% of the waste heat in the exhaust so if the total waste was 37% then the turbosteamer gets 29.6% back again.
    Here is a link: Here

    Quote Originally Posted by revetec
    This gels in with my theory that the energy lost through the exhaust is not as high as commonly stated. And yes, this is a theory, but one I have proved there is a flaw in. To what degree of % is still unknown but I can theorise that it is close to what I have stated.
    You haven't proved that there is a problem with the conventional laws and theories. You have proved you own misunderstanding of the conventional laws and theories governing heat engines.

    Eh?
    Last edited by hightower99; 08-03-2010 at 11:34 PM.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  14. #1319
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    Quote Originally Posted by hightower99 View Post
    That is just plain wrong. Any heat out the exhaust which isn't subsequently used to generate power in some way is lost. Subtracting the power from exhaust heat is subtracting it twice from the equation.

    But that heat is there because it didn't produce any power! If it had produced power then the heat would not be there! This statement makes me think you have completely misunderstand how a heat engine works.
    I had a little time today to clarify the issue.

    Pressure peaks in a cylinder at around 50bar and at a temp of around 2,100degC at the flame. As the piston moves down the gas expands. A expansion in vlume reduces heat (PV=C) Where as P=pressure, V=Volume and C=Temp. Just as the exhaust valve opens the pressure is around 5bar and the temp is around 700degC. Even though the heat is now about on third of the heat generated the pressure the heat created (which creates force on the piston is only 10%. If we are to take a reading at this point it is 700degC. But as the formulae goes, the heat is higher due to the pressure. As the gas flows down the manifiold we reach close to 1 bar with flow (if not restricted) which using the formula means the exhaust temperature drops to arouns 175degC. If it is restricted as a blocked muffler the temp is higher, but engine performance decreases. So at 175degC this is around 8% of the peak temp in the cylinder during combustion. Note than when the exhaust is driving a turbo, the manifold between the engine and turbo glows very hot due to the restriction of turning the turbo blades, and after the turbo the exhaust is much cooler (and it hasn't lost that much heat in radiation, rather than the gas is at a lower pressure and thus temperature.

    This is why exhaust heat exchangers cannot recoup 30% heat as the exhaust would have to be restricted to around 5 bar to maintain the heat.

    I sourced this information from NASA and MIT
    Boyle's Law
    Charles and Gay-Lussac's Law

  15. #1320
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    Quote Originally Posted by revetec View Post
    Pressure peaks in a cylinder at around 50bar and at a temp of around 2,100degC at the flame. As the piston moves down the gas expands. A expansion in vlume reduces heat (PV=C) Where as P=pressure, V=Volume and C=Temp.
    The math here is incorrect. The equation I think you tried to use is Boyle's law which is actually:
    pV = k
    Where (p) is pressure, (V) is volume, and (k) is a constant (not temperature). So in the case shown the volume would increase thus decreasing the pressure to maintain the constant k. I must say I am confused why you are trying to use Boyle's law here? Why not use the wonderful ideal gas law which is a combination of all the relevant gas laws.
    However seeing as you seem to want to find the temperature I would suggest you look at the Isentropic process equation where the ratio known is the ratio between maximum and minimum volume, in which case the temperature is T2 = T1(V2/V1)^(1 − γ) where gamma is the heat capacity ratio (normally 1.4 for air and 1.3 for combustion processes)

    Quote Originally Posted by revetec
    Just as the exhaust valve opens the pressure is around 5bar and the temp is around 700degC. Even though the heat is now about on third of the heat generated the pressure the heat created (which creates force on the piston is only 10%.
    Actually 700degC is over 40% of the heat if the peak was 2100degC. Remember heat ratios need to be calculated from absolute temperature. If the pressures you have given are absolute then yes the pressure is now only 10% of peak, however if they are gauge readings (more likely) then 5bar is almost 12% of peak pressure. However all of this is really moot because the set of conditions and parameters you set can't co-exist...

    If the given parameter for peak pressure is applied to a cylinder with a 10:1 static compression ratio then the exhaust temperature would be roughly 920degC. In order to achieve 700degC you would need a static compression ratio over 19.5:1. If you look at the pressure parameters you gave (peak: 50bar gauge, minimum: 5bar gauge) that only requires a static compression ratio just over 5:1 to achieve at which point the exhaust temperature would be almost 1200degC. At 10:1CR you would only measure 0.6bar gauge for exhaust pressure and at the 19.5:1CR required for the given exhaust temperature of 700degC you would only measure 0.07bar gauge for exhaust pressure. Just FYI...

    Quote Originally Posted by revetec
    If we are to take a reading at this point it is 700degC. But as the formulae goes, the heat is higher due to the pressure.
    Not sure what you mean by the heat being higher? higher than what?

    Quote Originally Posted by revetec
    As the gas flows down the manifiold we reach close to 1 bar with flow (if not restricted) which using the formula means the exhaust temperature drops to arouns 175degC. If it is restricted as a blocked muffler the temp is higher, but engine performance decreases. So at 175degC this is around 8% of the peak temp in the cylinder during combustion.
    What formula are using here? Also 175degC is still almost 19% of the peak temperature.

    Quote Originally Posted by revetec
    Note than when the exhaust is driving a turbo, the manifold between the engine and turbo glows very hot due to the restriction of turning the turbo blades, and after the turbo the exhaust is much cooler (and it hasn't lost that much heat in radiation, rather than the gas is at a lower pressure and thus temperature.
    Firstly turbo-chargers don't increase manifold temperature much by restriction, rather the turbo allows the engine to burn more fuel per cycle, this and the increased exhaust temperature when the exhaust valve opens contribute to manifold heating. Of course the exhaust is cooler after the turbo it was expanded in the turbine section of the charger and heat was extracted and converted to power which was subsequently used to spin the compressor and compress the intake air.

    Quote Originally Posted by revetec
    This is why exhaust heat exchangers cannot recoup 30% heat as the exhaust would have to be restricted to around 5 bar to maintain the heat.
    Massive leap of logic there Brad. There is a massive difference between a heat exchanger and a something like the turbine section of a turbocharger. Where do you think the heat went? Please read the article about BMW's turbosteamer!

    Quote Originally Posted by revetec
    I sourced this information from NASA and MIT
    Boyle's Law
    Charles and Gay-Lussac's Law
    What? You couldn't read a simple high school physics text book? Had trouble navigating Wikipedia? Seeing as you got most of it wrong I would seriously consider reviewing the credentials of the guy who told you he was from NASA/MIT
    Last edited by hightower99; 08-04-2010 at 07:48 AM.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

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