Efficient Engines - [ Engineering ]

Efficient Engines - [ Engineering ]
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Engines as conduits of Energy "The Mindset of An Engineer"
1. A properly designed engine is not to use energy.
2. A properly designed engine processes energy, not use it.
3. Inefficiency in an engine occurs, when an engine uses any amount of energy, even 1 %.
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What is Efficiency Cost ?
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What does an Engineer desire the engine built to do?
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When an engine is built, the machine is graded in the unit: "Efficiency Cost".
Efficiency Cost is defined as:
"The amount of energy an engine USES, to perform the work it was built to do."
Example: If an engine processes 98% of the energy to perform the work it was built to do, it's Efficiency Cost is 2% or "2 points", or "2".
Therefore
An engine with an Efficiency Cost grade of '2', is understood to be 98% Efficient.
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An Engineer desires an engine to perform some type of work,with minimum Efficiency Cost.
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Further
The difference between processing energy and using energy Using energy is stagnation in "Work Done"; that is, no "work" is performed.
Example: The Gasoline Engine.
(i) The Gasoline engine uses energy, it does not process it.
(ii) The Gasoline Engine does "no work",because it uses (burns) gasoline.
(iii) Since the gasoline engine uses energy, it is therefore stagnant, That is, it does not move anything. ------------------------------------------------------
Challenge for Engineers:
Remember: An engine processes energy, not use it.
Heat is energy not the mixture for cold fusion that produces heat.
Therefore
Build an engine that processes heat energy.
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snipped-for-privacy@yahoo.com writes

[snip long diatribe]
You have clearly never studied, or completely failed to understand, thermodynamics.
David
--
David Littlewood

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On Wed, 24 Jan 2007 23:23:33 +0000, David Littlewood

Or perpetual motion <g> -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
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writes

Right; there are those of us who know everything and those who know sod all. I fall in to the latter but aspire to the former.
Neither of your answers tell me anything about the OP. The OP 'appears' carefully reasoned, but your reply posts are just piffy one liners telling us nothing, appart from a desire on both your parts to belittle the OP.
All you guys are demonstrating is your arrogance and intollerance to those who arent as clever as you. Perhaps Im a stoned old hippy, but I thought news groups were about sharing infomation, not demonstating how cool and clever we are.
No?
I would be nice to see a proper explanantion as to why the OP is rubbish.
AC
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AC wrote:

Perhaps you could be less reliant on others and go looking for the answers yourself. A starter would be the efficiency of heat engines. If you had paid attention during physics classes at school an explanation wouldn't be necessary now. The OP is is a troll, looks like he's hooked you.
Tom
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Tom wrote:

To cut a long story short:
efficiency is basically the energy input divided by kinetic energy given to whatever you are moving.
Trouble is, there are practical limits using normal matter (not hocus-pocus science fiction "frozen force" [1] or such) because all matter is lumpy, if you look close enough at it.
It's impossible to have a *perfectly* smooth surface, so there will always be losses due to rubbing of some sort, whether steam down a pipe, electrickery down a cable, or a shaft rotating in a bearing - this produces heat and sound which is a loss of efficiency, and you can't get around it.
Modern machining methods can't produce an engine with perfect efficiency - even rocket engines (which are supposedly most efficient) have losses due to turbulence effects (the particles in the blast rubbing each other) otherwise they would be completely silent.
[1]which will still be lumpy because whether quanta are particles or waves, they still have a finite size or they couldn't interact. And if they can't interact, then they don't exist.
--
BigEgg
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bigegg wrote:

A better description of efficiency is useful energy output compared to energy input. Then you can apply it to an alternator for example, where mechanical energy is input (force in the fan belt times distance) and electrical energy is useful output (volts times amps) - heat and noise are not useful outputs.
I don't have a handy definition of what an engine is (as opposed to a motor), but for heat engines where hot gases have to expand to do work there is an inevitable inefficiency - this is the thermodynamic guff about entropy always increasing - when pressed most scientists will write you an equation, but it turns out they don't actually understand entropy - not in the way an engineer needs to understand something - they just use it in calculations and think of it as disorder in the universe. Even if every bearing is perfect there is a fundamental limit to the efficiency of a heat engine related to the difference in temperature between hot and cold, and the smaller the difference in temperature the less efficient it is. Don't press me on this - I am not a scientist and its an airy fairy concept hard to grasp for an engineer - but it is proven and you can calculate it.
I expect the most efficient heat engines are gas turbines in electricity generation, which get to 57%. Every % is worth a fortune to the power generators, its not just poor bearings !! Its this inevitable inefficiency in heat engines.
Anyway, engineers don't always strive for efficiency in an engine. I suspect an aircraft engineer will place reliability above efficiency. I sure as hell don't lay awake nights wondering how to make things more efficient. After all, we are up against the laws of physics.
Look up Carnot Cycle in Wikipedia for more info. This is a very odd way to explain efficiency, but the principle applies to all engines with expanding hot gases - steam, diesel, petrol, gas turbine, even stirling engines.
Steve
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Cheshire Steve wrote:

<snip>
<snip>
I thought my description was easier for a layman. :.)

It's cos at a given temperature, the particles of the material are at a particular (heh-heh) average speed and distance. This makes them statistically more likely interact than at different temperatures (1) - it's the interaction which causes the inefficiency.
(1)it's sort of like having a bowling ball and a marble on a snooker table which is relative in size to the average size of the balls - it's easier to make the marbles hit each other on a table 100x the size of a marble than make a marble hit a bowling ball on a table 50x the size of the bowling ball (or 1500x the size of the marble). The more they marbles hit, the more inefficiency there is.
In the case of atoms, this ineffieciency shows as light and other radiation (sometimes in immeasurably small amounts, but it adds up), in the case of marbles, it shows as sound and heat
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I think you are getting a little fanciful. Your balls explanation is self-referential.
The simplest explanation of why heat is lost in a heat engine is that in any process conducted at finite speed there will always be temperature differences between different parts of the system. Heat will flow from hotter part to cooler part, and all the King's Horses and all the King's Men cannot make it flow back up the temperature gradient again (First Law). A significant part of this heat is flowing to bits you don't want it to flow to, and it's mostly gone forever (well, you can do a bit to help with heat exchangers and the like, if the plant is big enough to justify it, but only a bit).
Light and sound are just special forms of energy (or heat, or work - these are all thermodynamically equivalent). They also form relatively minor components in most systems, except at very high temperatures in the case of light (radiation).
David
--
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Sorry, should have said "Second Law". Brain out of gear.
David
--
David Littlewood

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Alan,
I gave a one liner response partly because the bollocks he posted annoyed me. However, a fully-reasoned answer would be very long, and would take me an amount of time I don't feel like spending. Those readers of the NG who need to know probably know more about it then I do, and those who don't would mostly be bored stiff. Also, the post was so far removed from reality that it is hard to know where to begin. The purpose in posting a short "critique" was to discourage him from coming back with more, and to discourage anyone without the scientific background to refute his words from taking it seriously.
However, as you are clearly someone who has a genuine desire to know more, some suggestions. The 3 laws of thermodynamics set out certain principles which apply to all matter, and especially to heat engines. The laws have been proven both theoretically and experimentally literally millions of times. The second law shows that no heat engine can work with 100% efficiency except at absolute zero of temperature (and the third law, rather awkwardly, shows that you can never reach absolute zero). It turns out the maximum theoretical efficiency of any heat engine is limited by the absolute temperature ratio between the hot end and the cold end.
This is why (or one of the reasons why) electrical power generating stations go to so much trouble to cool the cold end with cooling towers, and why turbine designers go to so much trouble to find ever more expensive ways of making the hot end (the gas turbine combustion chamber) of a gas turbine as hot as material science will permit. Large modern combined cycle gas turbine (CCGT) electricity generating sets approach 60% thermal efficiency, which is pretty close to the thermodynamic limit of efficiency for the temperatures achievable. Most smaller-scale heat engines cannot approach this efficiency, as their size makes control of heat loss much more difficult to achieve.
I suggest you look around for suitable books on basic thermodynamics - I'm not about to spend hours writing on the NG - and also look at some introductory texts on the Otto cycle (the one used in petrol/gasoline engines) and the Stirling cycle (which uses external heat sources to heat air). Then you should understand why the OP's diatribe was such bullshit.
David
--
David Littlewood

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This isn't what I would call a proper explanation but it is good enough.
I quote the OT(1). (ii) The Gasoline Engine does "no work", because it uses (burns) gasoline.
A simple enough statement that if true would mean that almost all cars, planes, ships can't move as they are all powered by "Gasoline Engines" or their close relatives. However as these vehicles do work the OT's statement is false.
(1) OT = Original Troll.
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snipped-for-privacy@yahoo.com wrote:

What is this load of illiterate baloney ?
Steve
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On 25 Jan 2007 03:12:47 -0800, "Cheshire Steve"
I think you just answered your own question - its a load of illiterate baloney. <G>
Regards, Tony
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