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dedeleco
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Message non lupar dedeleco » 29/04/11, 21:02

In the Wikipedia is a big mistake or inaccuracy
Call it what you think.
we must indicate the volume of the cylinder, which is in addition to its surface and its length.
assume that the length of the cylinder is equal to 1.

This power is the maximum of Kinetic energy that can be extracted by stopping all the air arriving in one second.
By second it is the kinetic energy inside the cylinder of air passing in one second, with a length equal to the L= Velocity m/s so that it gives the formula P = 0,5 x density x aera x velocity^3

It is calculated by extracting all the kinetic energy of the air arriving every second in the cylinder LxArea=VxArea by stopping it completely at zero velocity after.
The length of the cylinder is not assumed equal to 1, but it is the length passing in one second at velocity of the wind.

So I do not see any error.

Real wind turbine can never stop all the wind and thus have a quite lower power and even a different velocity power law.
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Message non lupar inventor » 03/05/11, 03:12

dedeleco a écrit :
.... equal to the L= Velocity m/s

So I do not see any error.



However, there is an error. Since when is the length L is given in units of speed?
Because it is convenient??

Image

This is Homer. Now you can safely drink, because he knows the underground fan will give him a lot cheaper green energy.
It can use an underground windmill used an old engine, for example, the Harrier. Or the same fan.

Image

Regards Andrew :cheesy: :cheesy:
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Message non lupar inventor » 06/05/11, 12:11

" The Full Underground Windmill "

Image

Regards Andrew :D :D
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Message non lupar dedeleco » 06/05/11, 14:13

However, there is an error. Since when is the length L is given in units of speed?
Because it is convenient??


No !
Because the definition of power is the energy by unit of time, i.e. second and thus the volume of air stopped in the same unit of time is given by the surface times the lenth of this volume moved in this unit of time, the second, i.e. the speed which is the length moved in the unit of time !!

I hope that it is clear .
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Message non lupar inventor » 07/05/11, 00:09

dedeleco a écrit :
However, there is an error. Since when is the length L is given in units of speed?
Because it is convenient??


No !
Because the definition of power is the energy by unit of time, i.e. second and thus the volume of air stopped in the same unit of time is given by the surface times the lenth of this volume moved in this unit of time, the second, i.e. the speed which is the length moved in the unit of time !!

I hope that it is clear .


"Because the definition of power is the energy by unit of time.'-This statement is undoubtedly true.

Well, now comes to the energy:

But energy ust have two expression, mass and V cube.

And now it comes to give proper weight (mass) of air, which is involved in the production of this energy.

If we take a completely flat disc theory, a face of S ( 3.14 R ^ 2 ) he has no weight (mass) because it is flat.

This is a situation of flat sail, which does not move and standing still, despite the urge to wind it. So do not give any energy, since V = 0

Only when it starts to move in accordance with the wind, we can talk about some kind of energy received from the wind.

The magnitude of this energy in such a sail depends on the pace of a sail, and not from the wind speed....
And it might happen and this situation:

http://en.wikipedia.org/wiki/Ice_boat
http://www.youtube.com/watch?v=aJpdWHFqHm0
http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind#Sailing_dead_downwind_faster_than_the_wind

However, to calculate the energy needed air mass, and in addition to the flat surface of the disk must have its length, independent of the speed of the wind.
So far, for convenience, or unfairness has attempted to introduce mass as a function of wind speed. this leads to inaccurate and simplified calculation results of energy.
You can now imagine pipe with an area of ​​the disk, but relatively long. Mass will be in this case, S x L x G, and all will take part in the creation of energy, he can not, this " pillar of the air " break into several parts
Is it now clear?

Andrew :D :D
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Message non lupar dedeleco » 07/05/11, 02:06

This is not very clear ?

I agree energy is mass times 0.5xV squared . (not cube) and all power of incoming wind is 0.5xair-mass-incoming/second-times-Vsquared
and for a surface S this power of all the incoming wind is 0.5xSxdensityxV^3

I hope to be more clear with this :
There is 2 things:
The real power of a real design, quite variable with the design as function of the speed of the wind, not to slow or not too fast

and the maximum possible power of the wind for all designs.
The maximum power inside the wind is defined as ;
This power is the maximum of Kinetic energy that can be extracted by stopping all the air arriving in one second.

without considering how it is made or even if it is possible easily !!

If extremely very clever, it is possible to extract all the energy inside the wind so that at the end, the wind is no more moving !!!
For example stopping bullets, like the air, gives all their energy in heating and accelerating the stopping material.

The difficulty is what to make with the air immobile unable to go out of the turbine at zero speed !!
For example several turbine with increasing diameter consequently are possible, so that the speed of the wind is quite smaller.
For example 1/5 with 5 times diameter for out, allows to extract the same quantity of air as at the entrance, and gives (1/5)^2=1/25 of power in the wind lost in the outside ( 4% ) and the 96% inside the turbines !!
!!
There is commercialy several turbines one after the other !!

I agree that if the turbines or the sails are not moving, the real power obtained is zero !!
but it is not a good design.
The design is free and the maximum possible power of the wind, (or the necessary power to move the wind), is given by this formual as V^3.
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Message non lupar inventor » 08/05/11, 00:39

I think that even one session, and we'll be in full accord :D


dedeleco a écrit :This is not very clear ?





and the maximum possible power of the wind for all designs.
The maximum power inside the wind is defined as ;
This power is the maximum of Kinetic energy that can be extracted by stopping all the air arriving in one second.


without considering how it is made or even if it is possible easily !!

If extremely very clever, it is possible to extract all the energy inside the wind so that at the end, the wind is no more moving !!!
For example stopping bullets, like the air, gives all their energy in heating and accelerating the stopping material.

The difficulty is what to make with the air immobile unable to go out of the turbine at zero speed !!
For example several turbine with increasing diameter consequently are possible, so that the speed of the wind is quite smaller.
For example 1/5 with 5 times diameter for out, allows to extract the same quantity of air as at the entrance, and gives (1/5)^2=1/25 of power in the wind lost in the outside ( 4% ) and the 96% inside the turbines !!
!!
There is commercialy several turbines one after the other !!

I agree that if the turbines or the sails are not moving, the real power obtained is zero !!
but it is not a good design.
The design is free and the maximum possible power of the wind, (or the necessary power to move the wind), is given by this formual as V^3.



This power is the maximum of Kinetic energy that can be extracted by stopping all the air arriving in one second.

The answer to this question: Why in one second ? :?
And not, for example, at time 0, 5 seconds or 3 seconds?
I you a hint: because it's such a whim, in order to "simplify " the calculations were...
Because one second looks nice.. :D
And you can completely skip the discussion of mass energy, which gives the energies....

And why do you consider a complete stop the wind, as in the venturi nozzle is repeated acceleration of the wind ??


For example stopping bullets, like the air, gives all their energy in heating and accelerating the stopping material.


We are not a good example.
After the first round has its own strictly defined mass.
Wind staying on a fixed obstacle, rather, it is not heated, and vice versa - cooled.
More interesting is an example of how the ball takes on this energy, for example, pneumatic weapons.
In short, a pneumatic gun, the ball is rather low energies, while in the air rifle with a long barrel, energy and range of a projectile are much larger.
Because the length L is of crucial importance here.

Regards Andrew :D :D
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Message non lupar dedeleco » 08/05/11, 01:47

A second : because it is the unit of time used in the definition of power and acceleration used for kinetic energy, energy in one unit of time.

Why to stop? because starting from immobile air, it is the energy necessary to move this air at speed V giving to air its kinetic energy.

This energy is the maximum possible to extract, equal to the kinetic energy of air.

Stopping the wind, even partially, heats the surface, quite evident on a supersonic airplane like concorde or on a satellite coming back in the air !!!!
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Message non lupar inventor » 08/05/11, 02:23

dedeleco a écrit :A second : because it is the unit of time used in the definition of power and acceleration used for kinetic energy, energy in one unit of time.

Why to stop? because starting from immobile air, it is the energy necessary to move this air at speed V giving to air its kinetic energy.

This energy is the maximum possible to extract, equal to the kinetic energy of air.

Stopping the wind, even partially, heats the surface, quite evident on a supersonic airplane like concorde or on a satellite coming back in the air !!!!







This energy is the maximum possible to extract, equal to the kinetic energy of air.

What amount(mass) of air? Please carefully and not propaganda slogans.



because it is the unit of time used in the definition of power and acceleration used for kinetic energy, energy in one unit of time.

That is undoubtedly a unit of time, but it certainly is not I demand to define energy. First, define the energies, and then the power....



Stopping the wind, even partially, heats the surface, quite evident on a supersonic airplane like concorde or on a satellite coming back in the air !!!!


Well, not so obvious. Especially with what you are writing is in Concord, it's not stopping the wind, and friction is entrusted with the plane, and this is another matter..

Regards Andrew :D
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Message non lupar inventor » 09/05/11, 00:41

You know how it works "Underwater Windmill" ?




Image


Regards Andrew :D :D
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