Measuring Instantaneous and Total Fuel Flow with a Pelton Sensor and Digital Readout

good question. Trouble is, my melts are so short the difference wouldn't be discernable. I did a melt yesterday, you saw the #6 packed solid and I was pouring in 25mins off just jet-a. Why bother with oil for that?

 

I use a 2" PVC valve to control combustion air flow, and so my thoughts on having a fuel flow meter would be to add an indicator and large dial on the combustion air valve, and then mark on that dial that show the associated fuel flow for each air valve setting across the 90 degrees of valve opening.
That way if the flow meter fails, or if it is not compatible with long-term use with diesel (the manufacturer will not guarantee that it will keep working with diesel), then you only need to adjust the combustion air valve, and then adjust the needle valve accordingly.

Its always good to have a backup plan.
There was a cartoon strip, it was either B.C. or Wizard of ID, and they were fighting a huge battle, and the king asked the general "We are losing; do we have a backup plan?".
The general said "Yes we do" and then shouted very loudly "OK MEN, BACK UP !!!".

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I’ve put the meter to work for its maiden voyage. It is behaving as hoped/expected. I am lovin being able to make fine adjustments up and down and knowing where I am flow-wise. It seems like the difference between using a drill press vs a milling machine with DRO. Instead of hunting around for the desired setting, I can nail it and know that it is spot on.

Right now the furnace is running good and hot at 2.2 gallons per.



Denis

 

Dennis, I got to hand it to you. You got the largest furnace that I dream of!

You must have neighbours half a mile away.

During my tests I’ve had rubberneckers come out of the woodwork that I’ve never met before. They seem to watch from a distance.

Being able to measure fuel is a large step. And, I think the most important one!

I have been playing with a needle valve that has nine rotations and 20 slash marks per rotation. And I’ve been playing with a high-velocity-air-turbine.

The airspeed (CFM) it is quite manageable using a ball valve. The fuel is a bit touchy.

Awesome thread!

Edit; I do like seeing litres per minute. (Or millilitres per minute, Same same)

 

No, his neighbors are just whiny bastards... "Oh the noise..." That's his silencer to keep the peace.

Did I hear you correctly?? A needle valve? Ball valves for fuel are a "bit touchy" ?????????
He does some nice woodwork. Notice he routed the edges all fancy like? I might have to look into making one of these someday.
Cool party trick! Best part>>>>>>>>>>. NO AIR COMPRESSOR!

 

Jason, thanks for your kind words.

I am not sure what you meant by “no air compressor”. I use an air compressor to atomize fuel set at 3 PSI. Using the compressor at such a low pressure means it is just loafing and it reduces the air flow velocity which increases the air/fuel dwell time in the furnace which I think improves heat extraction.

The needle valve I use is quite sensitive—-about a 5 to 10 degrees turn results in a .01 liter per min flow rate. A ball valve would seemingly be essentially “on” or “off.”

I am still learning how to tune the furnace, but I feel that knowing the fuel input is very helpful as it provides one more “known” in the equation.

Denis

 

Lowering the air pressure seems to increase the droplet size.
The higher the compressed air pressure, the finer the mist.

I would have thought that fuel broken into finer particles would burner hotter, but that is not how it works.
The white paper by the Delavan engineer sheds some light on that topic.

It also has to do with solid cone/ hollow cone spray pattern, and some other variables such as combustion chamber size, fuel viscosity, etc.

And the white paper about pulsing the fuel pressure to increase the surface area of the hottest parts of the flame is also interesting, and supposedly results in a 20-30 % fuel savings.

To get completely away from compressed air, you need a gear pump and pressure-style nozzle, which is my next build (in progress).

Edit:
I have suspected that the fuel flow rate could be reduced to less than 3.0 gal/hr.
I have used about 2.75 gal/hr to melt iron, and it worked fine, and still seemed excessive.
My guess is that iron could be melted with 2.0 gal/hr, especially on a repeat melt, and that would reduce the required combustion air, and combustion air pressure, which would reduce leakage around the lid joint.

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Yes your experience has got me backpedalling a little bit for now. (Maybe forever!) but I will be cursing myself with the first needle clog.

I’ve been playing with the fuel pumps for delivery through 3/16 ID tube. Depending on the length of the tube there is a certain amount of static pressure. The needle valve is making things very consistent or fuel.

Today I accidentally stumbled on to a even smaller nozzle. It is so small it all fits inside of a 1/8 iron gas pipe. It might be limited in its BTU, but.... the burn tube works with my blower and atomized water with great performance with no air compressor.

I’m using standard brake line with the fuel delivery coming through the flare fitting. The Bernoulli principal tripped me up a bit. I was thinking about pressurizing from the outside in. Oh I was wrong. Now I just need to figure out how to make the fuel delivery pipe adjustable. At this size,... I’ll probably put two burners in depending on there BTU performance.

 

yeah bernoulli, he's a bastard. People will swear up and down that's what makes airplanes fly. When I show them a rock flying, you can see smoke coming out their ears.

 

I think you pointed out to me in my first nozzle the water trapped just after the Venturi. This is an example of Bernoulli principal.

This is my test nozzle. The air does rush around and smash the fluid. Different fuel flow rates and different air flow rates change atomizing depending on how close the flare is to the burn tube.

 

Dennis sorry if you’ve had problems with your neighbors. I must’ve missed that, I wasn’t poking fun. Is that a insulated chimney or homemade chimney?

 

No worries, Matt. The neighbors' house is about 150 or 170 feet from my burner and yes they complained about noise which registered as 73dB at the property line and about 40 feet from their house. I was really concerned there would be no practical solution ot their concern and the county noise ordinance says "any loud or unusual sound" may be objectionable and therefore cause for correction. That definition is so vague the only option, if push came to shove, would be an expensive legal battle or fix the noise.

Intuition lead me to try adding on a pipe to act as a long noise-reducing chimney and it worked much to my surprise and relief.

The chimney is simply a 10" galvanized heat duct line with 1" of 2600 degree wool with a 6 inch pipe also lined with wool. I also brushed on a layer of satanite for the first 18 inches of the lower pipe and at the junction of the second pipe to the first. Why the smaller second pipe? No good reason but it works an is smaller and easier to handle than the ten. Both are pretty light. It is important to have pretty good seals where the chimney meets the lid and where the two sections join. Any jet of hot gas will break down the pipe in short order. the pipe surface temp during a melt is around 550 F near the furnace and around 400 near the top. It is also good to figure out how to support the chimney so that it is not bearing on the center of the lid. I can provide more details on that should anyone care. Also, I used about thirty 5/8" long number 8 SS pan head screws per pipe poked through the pipe and into the insulation to prevent it sliding out of the pipe. The chimney in its current iteration is holding up very well.

With the chimney in place the furnace is very quiet---inaudible 100 feet away an easily talked around in a normal voice nearby.

Denis

Edit: Here is a link to the original thread though the chimney has morphed some since that thread. http://forums.thehomefoundry.org/index.php?threads/reducing-noise-from-an-oil-fired-furnace.503/

 

I ran the furnace melting iron again today. I decided to run at .19liters per minute ( I cannot tell you how nice it is to actually no real-time fuel burn rate rather than guessing.). The furnace ran modestly hotter than at .15L per min. Now I am not quite sure if I have bracketed the optimal burn rate or not. So, next melt occurring in a few days will likely be at .7 to .18 L or min. Eventually I hope to find the sweet spot and the I expect to be able to hit it time after time. The meter is working very smoothly and accurately.

Denis

 

Then you won't need that thing anymore. Leave the valves set and mail it to me!

 

After using the fuel pump/pressure meter/flow rate meter a couple times, I am satisfied that I’m unlikely to need to make sigificant modifications to it. So, I boxed it in to prevent accidental bumps etc causing damage to the delicate sensor wires etc. She ain’t pretty, but she’s solid This was a sort of evolving build which could have been executed with a more craftsman-like touch. It should be robust enough, however, and the box panels are easily removed to gain access to the innards.



I used a non-standard plug on my device and 12v DC power supply to prevent air-headed plugging into 110AC power. I can make any imaginable error. I started to plug into 110 a while ago and was glad the plug stopped me before I fried the pump!






Denis

 

That is a smart idea on the plug.
Nice meter.
If I had more time I think I would build one of those.
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Thanks for the kind words.

For anyone thinking of making a similar setup: I will mention that the only flow sensor I would spend my money on is the one I pictured in the thread above. Others advertised on eBay were worthless. But this one, made in Germany, is great. I was a little concerned that delivery time might be an issue, but delivery was very prompt---less than ten days from eBay order. And it comes with excellent documentation. FWIW. I think there are a variety of readouts that would work. But I bought the one I used here on Amazon. In general, the readouts have little or no documentation.

Denis

 

I did go out to the barn today and fired up the foundry with the fuel set at .18L/min. That may just be an ideal setting. The furnace felt really hot but more objectively it had 50 pounds of iron a little too hot in an hour and twenty minutes. I measured the iron temp to be 2600f with my usual pour temp closer to 2550.

Once again, the meter/pressure panel worked smoothly and helped me keep the fuel flow constant. One observation that I have not quite figured out yet is that during the first 15 minutes of a burn fuel flow rate seems to tend to decrease by 10 to 15% despite no changes in the needle valve setting. That the fuel flow really is decreasing seems born out by evident leaning out of the burn consistent with measured flow changes and subsequent normalizing of burn with opening up the needle valve to normalize measured flow rate. Just to be sure that I am not being misled by the meter, next time, I will put my fuel can on a scale and breakout the calculator and stopwatch.

I also felt a lot more secure with the sensor and readout fully boxed-in as I did not have to worry about clumsily damaging the tiny wires that attach to the sensor and readout.

Denis

 

Some of my iron melts have been at 2.75 gal/hr, which is pretty close to your 2.85 gal/hr., and I had what appeared to be very hot iron, with a 20 lb melt reaching pour temperature in 50 minutes.

I have speculated that iron could be melted anywhere from 2.o to 2.5 gal/hr, but I have not had time to test that.

It would be interesting to see what a 20 lb melt at 2.0 gal/hr would do, and then compare that with perhaps 2.25 gal/hr and 2.5 gal/hr.
My guess is that at some point you will still be able to melt iron, but the time-to-pour-temperature will start increasing if you get the fuel flow too low.
And of course at some fuel flow level, you will not melt the iron at all.

For the metric-challenged (like me), here is the following conversion (if I did the math correctly).

1 gal/hr = 3.785 L/hr = 0.0630902 L/min
2 gal/hr = 7.570 L/hr = 0.12618 L/min
3 gal/hr = 11.35 L/hr = 0.18927 L/min
4 gal/hr = 15.14 L/hr = 0.25236 L/min

To change from L/min to gal/hr, multiply by 15.850326

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Put, your math looks really good. And if you want to measure this using a standard measuring cup that has millilitres, just multiply all your litres by 1000(as in red above).