since somone had a ultrasonic question....

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dacflyer
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since somone had a ultrasonic question....

Post by dacflyer »

i have a ultrasonic question too. anyone seen them cold steam fountains at these foo foo shops?\
its a decorative bowl full of water and inside it sits a puck of metal with a hole in it.. and it is some sort of ultrasonic device,, how does this thing make cold stram ( FOG ) you can see the water shoot up about an inch and it stams really hard...but its cold steam,,, is it a pizo disk buzzing at a certain khz. or gigHz. ??
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Re: since somone had a ultrasonic question....

Post by jwax »

You got it!
Typically piezo-ceramic driven at 30KHz-50 KHz.
When the shock wave from the piezo travels through water, it literaly "tears apart" the water molecules at the water/air interface.
Same effect seen at an atomic blast at sea- that radiating "white water" is the result of shock meeting the water surface.
It's been theorized that the regional effective temperature at those little bubbles of "cavitation" in ultrasonics is millions of degrees! Whew!
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Re: since somone had a ultrasonic question....

Post by jollyrgr »

These are nice to have but I have a couple complaints about them. The "steam" soaks everything around it but gives a good smoking effect. The other thing is the fine white powder that gets all over everything. At first I thought it was from deposites in the water so I used water from a soft water tap. Still the same dust.<p>(BTW: If you don't want a foo foo fountain you can get a halloween skull like mine.)
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Re: since somone had a ultrasonic question....

Post by terri »

Same effect as with ultrasonic room humidifiers. I've often wondered if the "dusting effect" is due more to collection and settling of dust particles on the water droplets in the air rather than solute load in the supplied water. Anyone know?
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Re: since somone had a ultrasonic question....

Post by dacflyer »

what is that dust anyway...seen that before too..
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Re: since somone had a ultrasonic question....

Post by High4Volts »

I had one of these ultrasonic mist makers for keeping the humidity up in my carnivorous plant tank. I never did see the white powder you are talking about. I did use RO water though so maybe that's why.
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Re: since somone had a ultrasonic question....

Post by terri »

I still wonder how much of the dust is due to water droplets picking up dust particles before they evaporate.<p>Aren't your carnivorous plant tanks a relatively dust-free environment, so regardless of what kind of water you use, you would not get the dust effect anyhow ?
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Re: since somone had a ultrasonic question....

Post by terri »

"Aren't your carnivorous plant tanks a relatively dust-free environment, so regardless of what kind of water you use, you would not get the dust effect anyhow ?"<p>That was poorly stated. What I meant was that the fact that you might be using the humidifier in a relatively dust-free environment (your plant tank) and using "pure" water does not allow us to discriminate between the three possibilities: (1) the dust is from the solute load in the water; (2) the dust is from the water droplets aggregating the dust particles in the air before evaporating, or; (3) both.<p>Me go now.<p>[ December 07, 2004: Message edited by: terri ]</p>
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Re: since somone had a ultrasonic question....

Post by High4Volts »

i did not have a cover on the tank because it need moving air. As far as dust, my house has plenty of that. lol
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Re: since somone had a ultrasonic question....

Post by Externet »

Hi ultrasonic fellows.
Which type of ultrasonic transducer could be attached to/replace the butterfly valve in a carburetor?
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Re: since somone had a ultrasonic question....

Post by terri »

Unclear:<p>D'you mean nozzles (jets) instead of "butterfly valve?" To atomize the fuel in the carb's venturi? You're thinking of using the fogging effect instead of a spray from the jets?<p>Believe it or not, there used to be something called a "brush carburetor," which used a rotating brush partially immersed in a pool of fuel, which then ran against an edge, thereby forming a spray. Much as if you ran a thumbnail over a wet toothbrush. Ca. 1912 or so.<p>[ December 08, 2004: Message edited by: terri ]<p>[ December 08, 2004: Message edited by: terri ]</p>
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Re: since somone had a ultrasonic question....

Post by Externet »

Hi terri.
I was thinking on the butterfly valve so the jets spray becomes finely atomized when the spray hits or passes nearby the ultrasonic butterfly. Unless that would not be the way to do it... I really don't know what would be the proper approach.
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Re: since somone had a ultrasonic question....

Post by terri »

Before you even get into what kind of transducer should be on the butterfly valve to enhance the atomization, the first question is: How much power is going to be put into the transducer to do all this extra atomizing, versus how much increased power the engine will show from this enhanced atomization. Will there be a net gain?<p>Many years ago I did a little informal research on all the devices that one can stick in one's carb(s) to supposedly enhance this atomization/vaporization and my opinion (challengeable, I suppose) was that any time you stuck something down the throat of an engine it had difficulty breathing and lost a little power. Even the "turbines" that you shove down there restrict the air flow --let's face it, the energy to spin the blades has to come from somewhere.<p>My long-term opinion is that carburetor builders have it down pretty good, and any "improvements" are the result of sales department hype, not dynamometer results.<p>However, even so, admittedly, carbs are not the best method of doing this mixing of fuel and oxidizer.... which is why the Goddess invented fuel injection.<p>In addition, I would be leery of having all this electrical power being applied right where the fuel/air mixture is coming down the intake piping. One teeny little spark....<p>If I were to do it, I'd probably try to figure out a way to use magnetostriction --maybe in the walls of the intake piping. Just stick a BMF coil around the pipe and cram a couple of hundred watts at 20-30 kHz into the coil.
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Re: since somone had a ultrasonic question....

Post by Externet »

Ha!... I did not expect the need of hundreds of Watts for such action.
A room humidifier or a carnivorous plant tank use hundreds of Watts to atomize ? <p>Well, the amount of gasoline spray in an automobile should not be much more than an ounce per minute ¿? How many Watts could that use ?<p>About the throat obstruction, well, yes, can be significant at wide open throttle demand, but at normal driving should not be of concern unless it is a huge transducer.<p>Fuel injection is about the same spraying technique at a different location in the engine. It does not improve much from carburation as atomization could.<p>On an improperly insulated wiring, a tiny spark at the throat could cause the same effect as backfiring, a undesirable event but not fatal.
¿What is the typical voltage used in a humidifier transducer... is it that high to be concerned with arcing?<p>Thanks for educating me. It's not my field.
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Re: since somone had a ultrasonic question....

Post by terri »

Well, I don't know for sure about the "hundreds of watts" --that was kind of an exaggeration for the sake of demonstration. <p>I'm sure you could configure something that would squirt a spray into the intake pipes. What I was really getting at was the fact that (a) some extra energy would be required from somewhere to generate the ultrasonics --even turning on headlights uses some extra fuel, which is something people forget, and (b) that the extra effort to do it this way might not be worth it unless a really dramatic increase in performance would result --and carb manufacturers have got the atomization problem down pretty pat. And fuel injection gets it even "patter."<p>The voltage required at the transducer depends on the transducer. "Crystal" transducers (barium titanate, quartz, rochelle salts, for example) require a high operating voltage (these are "high impedance" devices), whereas magnetostrictive transducers require a high operating current (these are "low impedance" devices) to generate a strong magnetic field.<p>Capacitive transducers likewise reuire a high operating voltage --they work just like capacitive loudspeakers except they don't need a bias voltage.<p>Magnetostrictive transducers work on a little-known principle that when you apply a magnetic field to some magnetic materials (like iron) they "shrink" a little, thereby generating mechanical motion from the magnetic field.<p>Both magetostrictive and capacitive transducers will generate a meechanical frequency at twice the frequency of the applied voltage, since they will distort in the same direction regardless of the direction of the applied field. Taking the capacitive tranducer as an example of this effect, the two plates of a capacitor will attract each other whenever a voltage is applied to them, regardless of which plate is positive and which plate is negative. So on the next alternation of voltage, they will still attract each other. So applying, for example, 60 Hz to the two plates of a capacitor will result in the two plates attracting each other 120 times a second.<p>The same holds true for magnetostrive transducers. A bar of magnetostrictive material will "shrink" regardless of the direction of the applied field. So applying a 60 Hz magnetic field to the bar will result in its "shrinking" twice for every full cycle of the applied alternating current.<p>In both cases, the only time the materials are "relaxed" is at the zero-crossing point of the applied fields --either electric in the case of the capacitive transducer or magnetic in the case of the magnetostrictive transducer.<p>This is why capacitive loudspeakers require a "bias" voltage --to keep them stressed in one direction while no sound signal is applied to them. Without this bias voltage, capacitive loudspeakers would double the frequency of the sound signal applied --this would be the worst form of sound distortion, no?<p>Whew! Sorry for running off at the keyboard.<p>This doubling of the frequency does not occur in (most) crystal-type transducers, since the direction of their mechanical distortion depends on the direction of the applied fields --not the strength of the applied fields.<p>The magnetostrictive and capacitive transducers are not used much, mainly because of their lack of efficiency. However, most crystal-type transducers have limited life and are fragile --electrets tend to lose their "built-in" fields over time, and rochelle salt and barium titanate crystals tend to degrade, mainly because of humidity and lack of mechanical strength. Sharp blows tend to fracture the crystalline structure. Magnetostrictive and capacitive transducers are pretty stable, though, and they are used in some specialized applcations. Quartz crystals are likewise stable but are expensive and are only really suitable for frequencies above the usual ultrasonic range... radio work, that is.<p>Anyhow, were I to attempt to improve carburation by use of ultrasonics, I would regard it as a "pure science" project without expection of any direct valuable results. However, I have found (as the whole human race has, over history) that even "impractical" experiments occasionally result in great breakthroughs in engineering and science. <p>And one potential application of the idea of ultrasonic cuarburation might be in carburating those new tiny micro-engines I read about a couple of years ago. These are supposed to be small enough to power eensy-tiny-little generators --the idea being to make the whole engine-generator package small enough to replace batteries in small appliances. Like your laptop. Seems like ultrasonic carburation might find a place in this kind of application. I understand they are thinking of using little itty-bitty Wankel engines for this.<p>Whew! Again, sorry for running off at the keyboard.<p>But my mind is "kiting off" again. Can you imagine opening your laptop and pulling a microscopic choke out and yanking on a teeny little threadlike pullcord to start its engine-generator set? Tee-hee!<p>And if this all comes to pass, we'll have you to blame for developing the teeny little ultrasonic carburetor that feeds the little engine!
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