induction heating diesel injection lines

I'd say that you should assume that you will heat with eddy currents. This suggests 100s of KHz as the running frequency.

Why not wrap the lines with resistive heater tape? That's cheap and common and very reliable.

John

Sounds bizarre, hope you don't have a loose fittings, the arc will indubitably display some nice side effects.

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Induction heating sounds like more fun though.

The guy on this web page is using about 200 khz.

You won't need as much heat has he got but he also describes several ways to limit heating.

Tom

Wow, that guy is a maniac. Great stuff.

John

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Thanks for the link. That guy mentions skin effect. I'd rather go for internal heating (eddy currents and hysteresis loss). Check out Tim Williams' induction heater page

Scroll down to the oscillator diagram. After a quick check of the SG3524 datasheet it looks to me like it would run at 5 kHz if you leave the "frequency control" open. I'll admit I know nothing about designing an induction heater. I had fancied that it might not be too complicated, just a matter of driving the coils. But there could be power factor issues.

Here's the link that got me started thinking about induction heating

I'm a newbie at magnetics but I'll give this a shot. (:o ...ducks flying books..)

The Goldilocks point for this is driving hard near saturation at the frequency where the permeability cuts off. That is if you want the least amount of turns. (A spin off idea is to use winding heat + induction heat. So more turns. Perhaps a nichrome wound inductor?)

Your core power follows the steinmetz equation. Lots of flux and use the highest frequency that doesn't degrade the inductance. You want to swing near -Bsat to +Bsat and that takes time. Too high f and you get less eddy heat and an overloaded driver. (That could be incorrect. The flux intensity is dropping but there's more frequency flux changes. Sweet spot?. )

Google for steel permeability vs frequency. I'd just do an experiment to test ur vs f and another experiment for Bsat.

Perhaps another experiment cause permeability varies with temperature.

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

Consider looking at prior art. There are so many better ways to run veggie oil that an exotic induction heater seems like more problems that it is worth.

Yes, maximize B. Steel saturates at about 1.6 T or something like that. So with one or two dozen turns we're talking about a few kiloHertz. Let me ask you (or whoever might know) whether the following equation is correct for a coil driven with a square wave? B=3DE/(N Ae 4 f) B: Teslas Ae: m^2

I'd use resistive heating in the fuel line running towards the fuel pump. Heating after the fuel pump won't be necessary and also introduces errors if the engine is controlled electronically. Also make sure not to heat the fuel too much otherwise too little fuel may be injected. Room temperature is enough.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
                     "If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------

E is average voltage. So I suppose that yeilds Bavg.

But you might want Bpk

Bpk = Epk * 10E8* (pulse time) ----------------------- gauss N*Ae Ae cm

1T = 10000gauss

I'm guessing you could try a resonant design if you need a crapload of supply voltage.

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

There are other people using induction heating, though I personally would only try it on an old mechanical fuel pump, not one full of expensive microprocessors.

From what I read, straight veg oil does need to be pretty hot, maybe 80C to get the viscosity anywhere near diesel. To start the engine, it is probably necessary to get the fuel in the injectors and pump warmed up, not just the fuel lines, (unless you ran it on mineral diesel before shutting down last time).

Chris

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I don't get why they call it "peak." Doesn't that equation just address a flat pulse of voltage E of duration t and Bpk equals B at time t or did I miss something?

Epk actually means Epp. The peak to peak voltage of the pulse.

Epk suggests a discontinous voltage. IOW..a pulse.

Just E alone suggests DC. This is not a DC circuit.

Bavg.. suggests a ripple. Bavg = /\/\/\/\/\/\/\/\/ Same goes for Eavg. It's to account for pulse duty.

_______Max / / / / Bmax, Bpk...suggests a limit. / / Max _/ /

That's the B you need when you compare to the saturation level.

Recall I mentioned 'near' saturation. I meant less than saturation. If you go over the curve you loose magnetizing efficiency.

Ok...I might botch the math and theory but here goes...

Inductor Energy E = LI^2 Joules

Specific Heat Capacity Vegatable oil = 1.67 KJ/KgK

Specific heat E = C*m*(dT)

So if you had 10 amps, 1H and 100% efficiency then transfering 100 Joules of EM energy to heat energy will raise 1gram of oil about 60K or 213.15 degrees.

Good enough to cook 1 french fry.

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

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No need to look at permeability just yet. The equation for flux in a voltage-driven coil doesn't include a term for permeability. I reviewed the theory last night and that equation I gave for a coil driven with a square wave Bpk =3D E / ( 4 f N Ae) still looks quite correct to me. So if steel saturates at 1.6 T and I say I want Bpk =3D 1 Tesla and I have 20 turns on an injection line with 8mm diameter, I get f =3D 16 kHz Unfortunately, the equation for skin depth _does_ include a term for permeability, and steel's high permeability means a very shallow skin depth of only about .04 mm at 16 kHz. No way reduce the frequency enough to get eddy currents _inside_ the tubing, either. I'd have to drive it at about 10 Hz. I can hope though, that magnetic hysteresis from the high B provides some internal heating.

r

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I should stop typing and start experimenting? Perish the thought!

_Max

You mean one french fry per second (f^2 s^-1)? Plenty enough to make my truck happy at idle, just maybe not on the highway.

I didn't check the math..

The equation assumes the core material can magnetically align at any frequency. Like in a vacuum. E / ( 4 f N Ae) = B may not be the same at 10kHz and 10kV compared to

100Hz and 100V.. For example a fictional material may not be able to switch polarities at 10khz. I do know ferrite can switch polarity much faster than steel.. I don't know how fast steel can align, then reverse.. That's why I suggested to research steel permeability vs frequency. When B/H drops off and ur drops to 1 due to increasing frequency, it means your driving an air core. An air core doesn't have hysteresis. It's as if the steel wasn't there.

I've been holding too, but...

Induction heating won't heat up the coil, as heating coil would.

Same..

Although I can't back it up with the math, I'd guess heating element beats induction heater for energy transfer.

Perhaps run current through a section of resistive tubing.

\-----------//----------/----nichrome coiled tube /

khz.http://www.richieburnett.co.uk/indheat.html

You can catch Tim,and other smart folks at

too. ;-)