h a l f b a k e r yThe word "How?" springs to mind at this point.
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Piezoelectric devises are used in many common devises like watches oscillators small linear actuators and many sensors. The principal is that when a very high voltage is run across the surface of the piezoelectric crystal, the shape of the crystal changes VERY slightly. On the other hand, when a pressure
is applied to a piezoelectric crystal a potential difference forms across its surface.
My idea is to use some sort of fuel combustion engine to pressurize some of these crystals as opposed to spinning an output shaft. The slight surface deformation these crystals will undergo will result in a very large potential difference. This voltage could then be stored in a battery, or run an electric motor directly.
I suggest using gas combustion since it is a readily available fuel source. I am working on a way to transfer pressure from expanding gas to the crystal in the most efficient way possible (something more thermally efficient than a piston-cylinder-connecting rod assembly). Maybe a turbine-compressor assembly would work best here?
It has been very hard to find DETAILED information on piezoelectric crystals regarding power outputs. I know they can produce a lot of voltage, but I don’t know about amperage.
This idea seems too simple to have not been tried before, especially given the fact that piezoelectric crystals are VERY common place this day in age, right?
Any thoughts?
Here's some info for you.
http://www.bostonpiezooptics.com/?D=6
[ldischler, Aug 10 2006]
Types of crystals
http://materials.gl...zoelectric_Ceramics
[ldischler, Aug 10 2006]
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It doesn't seem "too simple" to me... |
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Most electrical power is generated through gasoline anyway. I don't know if this could potentialy be more eficient than turbines, though. |
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Er... you're looking for the most efficient way to convert the pressure wave from gas combustion into pressure on piezo crystals? I don't think any conversion is necessary - just use the pressure wave itself and no moving parts. |
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yeah, that what i had in mind for the most part...but i wanted to go into a little more detail with the idea. where is the gas going to detonate? a combustion chamber of some sort is needed. what do you suggest [david]? |
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oh, and thanks for the links guys |
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Perhaps a combustion chamber whose lower surface is free to move, much as a piston in a cylinder. A spring allows it to descend when the combustion occurs until it hits a stop; when combustion subsides an exhaust valve is opened and the spring pushes the piston up to exhaust the spent gases. Would need some way to drive the valvegear though; I suppose it could be electrical if the device generated worthwhile power outputs. |
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yeah, or maybe a piston with combustion chambers on either side of it, this could improve power output. i am just concerened that this design might result in a lot of wasted kinetic energy that would be needed to draw in the charge air and expell exhaust, and not enough pressure on the crystal surface. maybe a very small gas turbine blowing air through a narrow tube with these crystals as an inner layer. or maybe a small turbine pressurizing a tanks with the crystals on the inner layer. this would eliminate the need for a valve gear. also the impellers would be experiencing low inertial roatation, so this would lower the amount on KE that the fuel would have to create, the rest would go into creating the pressure. |
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they produce little current but voltage can be sizeable. A gas igniter scheme where a spark is produced by striking the crystal has been used for years and it works quite well. They vary in their output but a couple of good producers are rochelle salts (water soluble) and barium titanate. |
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Maybe useful as a microelectromechanical device? |
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Don't know how you'd integrate the crystals... Maybe instead of a piezo crystal, use a mechanically-powered charge pump (pull charged capacitor plates apart)? This might be possible in silicon... |
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Why not making the entire combustion chamber completely out of the piezoelectric material? |
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I don't know if anyone will see this since the post is so old, but why not use steam? Place the piexoelectric crystals on the inside of the expansion chamber. Maybe wire them in parallel? |
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