Lots of previous threads on this forum.
There was one a year or so ago by someone who claimed to have converted his car to run on water and hence he saved a fortune. And there were references to online shops selling books at high prices explaining how to convert your car. Basically it is a scam, and the aim is to get you to buy a book that is full of nonsense. That Stanley bloke was a charlatan, and if you Google you should find out the truth.
If you split water into its constituents, that takes energy. When you recombine it, you cannot get back more energy. In fact you always get less due to inefficiencies in the process. You then have to convert that output energy into useful work i.e. propulsion. It is far more efficient to cut out the water carp and just feed petrol into an engine. The modern internal combustion engine is a marvel, despite the global warming issue.
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'Look up Stan Meyer. His electrolysis method is in the process of being patented.'
I looked this up and him being found guilty of fraud, lack of independent test evidence,breaching laws of themodynamics, and his death seem to discourage further progress towards a patent being granted.
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I have read reports claiming that water, if subjected to extreme sudden heat and pressure shock, can explode violently. Supposedly the process is that the shock separates the hydrogen and oxygen which recombine explosively as soon as the 'shock' subsides. However, a vehicle engine would not be able to produce sufficient heat or pressure to cause such a reaction.
If this exploding water phenomenon is true, it could be an explanation for the Tunguska 'meteor' that exploded over Siberia in 1908. If it was a comet made mostly from ice, as suspected, and it hit the atmosphere at 90,000 kph, which is faster than most meteors etc. hit, the sudden heat and pressure shock could have caused the huge explosion that occurred.
There is a device called a cavitation heater that has a rotor that spins water centrifugally and heats it very rapidly and was originally publicised as a producing more energy than you put in. Anyway, these things are now a commecial product, out there and used in industry now. They can boil water in a few seconds.
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>>I have read reports claiming that water, if subjected to extreme sudden heat and pressure shock, can explode violently.
Was this in a peer reviewed journal? If so, where can we find the article?
>>was originally publicised as a producing more energy than you put in.
There can't be any truth in this. If a perpetual motion machine had been shown to work, it would have made the news coverage for the LHC pale into insignificance. It would be the news story of the century, as all the world's energy problems would have been solved.
It's fairly easy with cheap, nasty, broken, and duff instruments as used by many home based crackpots to kid yourself that you have made more energy than you've spent, but, when proper testing, using traceable, calibrated instruments is performed, the claims are always seen to be unfounded.
>>Anyway, these things are now a commecial product, out there and used in industry now. They can boil water in a few seconds.
Yes, anything with a large enough input power can boil water quickly. However, none of these machines will be violating any laws of thermodynamics while operating.
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I dropped some water on an exhaust manifold today. It turned into steam in front of my eyes in a fraction of a second. Amazing speed of boiling water!
Amazing; can I sell this idea on anywhere?
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I dropped some water on an exhaust manifold today. It turned into steam in front of my eyes in a fraction of a second. Amazing speed of boiling water!
As I understand it, a turbocharger uses what would otherwise be waste energy in the exhaust gasses to get more power from the engine, making it more efficient. Isn't it possible to get any more use out of the hot exhaust, or is the amount of left over energy just too small?
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It can be done - Scania have been among the more active in finding use for the remaining energy in exhaust gas, using a fluid coupling to accomodate the large difference in speeds between the second turbine and the crank. See;
www.rotaryeng.net/Truck-TC.html
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It can be done - Scania have been among the more active in finding use
Thanks NC, interesting. What's the typical efficiency of today's engines, and are there theoretical limits on how efficient they can become?
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The most theoretical limit is given by the Carnot cycle.
en.wikipedia.org/wiki/Carnot_cycle
and
en.wikipedia.org/wiki/Carnot_heat_engine
The Carnot cycle represents an unachievable ideal. However, the equation for the cycle efficiency,
eta= (T2-T1)/T2
where T2 is the hot reservoir temperaure, and T1, the cold, begins to point towards the idea that for a real engine, the more heat energy you extract during the expansion, the more efficient the engine - it is this larger expansion ratio (very closely linked to the compression ratio) that makes a diesel very efficient - extracting further energy from the exhaust is better still.
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The most theoretical limit is given by the Carnot cycle.
Again interesting, but a bit beyond me. I was hoping for a rough idea of % efficiency from fuel energy to energy at the wheel. Googling found:
jagadees.wordpress.com/2007/10/20/ic-engine-effici.../
which mentions 15% or 20%. This seems quite low on the face of it to someone like myself who doesn't understand all the physics and/or chemistry behind it, but how far off the theoretical maximum are these?
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To take an extreme case of the hot temperature being the melting point of Aluminium, and the cool temperature to be close to ambient; (Temperatures in Kelvin)
(930-300)/930
ans =
0.6774
So, the very best that is still beyond actual possibility is about 65%.
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I soon gave up on the Carnot cycle equations! One question, NC. Is it not the difference in gas temperature that delimits the heat cycle? Thus, say 1922K as "TH", minus the coolest "reservoir" temperature, TC. Whatever that is.
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One way to see that subtracting Tc from Th doesn't lead to a measure of efficiency is to consider the untis - it's still a temperature.
The work done in the Carnot cycle is proportional to the difference between Th and Tc, while the heat energy supplied is proportional to Th.
Thankfully, the constant of proportionality is the same (the entropy difference) for both the work done, and heat supplied.
So, as efficiency is defined as the Work done divided by the energy supplied, you end up with
eta = (Th - Tc) / Th
This is non-dimensional, and so passes the first sanity check.
I know I'm riding roughshod over a lot of the finer details of thermodynamics by relating real engine cycles of operation to the Carnot cycle, but, it's not a bad starting point.
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Yes, I see what you mean. Its a sort of permanent boundary on the energy that can be extracted. I think:)
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I think:)
Yes!, The Carnot Cycle is as good as it could ever get, it assumes no heat lost to the surroundings, no friction, no losses, etc. It's an entirely ficticious cycle which could never be realised, but, even this ideal cycle predicts efficiencies far below 100% for reasonable temperature differences.
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Thanks NC. A real fount of knowledge, and interesting material!
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