Gear-pump pressure nozzle burner

Hi
Maybe an easy way to pulse the flame is to use a piston pump.
Dazz

 

Hi
I scanned through the pulsing paper. It looks like he pulsed at 10Hz but I didn't see a description of the pulsing valve. I also saw 100% pressure pulse produced the best results.

If I was to make a pulsing valve, I would borrow from the design of steam safety valves. They are designed to snap open and stay open until the pressure drops to some value below the opening pressure. Then they snap shut.

A small hydraulic accumulator just before the valve, with an adjustable air volume could be used to tune the pulse frequency. The relief pressure adjustment on the safety valve would then act as the pressure regulator for the nozzles.

It could be possible to use a standard safety valve. The problem would be finding a small enough one. Maybe the ones used on model steam trains would be suitable. Standard safety valves are designed to vent to atmosphere, so they don't usually have the fittings required to connect plumbing to the output.

Dazz

 

I just got a better idea.
Use a Corliss style valve, which is a steel rod with one side milled off flat.
The valve would rotate in a block of metal that was drilled for a passage straight through, and the valve goes through the centerline of the passage.
An o-ring on the motor side of the valve shaft would seal it.
The other side would be in a blind hole.

A variable speed Dremel could be used on the shaft, and so the rpm could easily go to 10,000.

I think this type of valve would work well in this application.
It could easily and cheaply be made and tested too, assuming you can machine small stuff.
It would need to be a pretty snug fit, but would not need to be a perfect fit.
The oily diesel would act as a lubricant.

A piece of drill rod would work, or a dremel tool bit shaft.

Seems like overkill, but if it worked as well as the white paper states, then perhaps worthwhile.
Dremels don't last very long, but perhaps with no load on it, it would last.

.

 

I did a bit of searching around about large pulsated furnaces other than that paper and the improved economy was about 5% with the main payoff being a reduction in nitrous oxide in the exhaust gases. I'm not sure it's needed for home use and I'd be wary of any claims made in Indian scientific papers: I've found more than a few were cut and paste Wikipedia pages in the past.

 

I tend to agree with you on that.
Its an interesting concept, but I think simpler is better, especially in the harsh environment around a furnace.

.

 

Hi
The only potential benefit from adding this feature would be if it increases the temperature in the furnace. If it does that then it would increase the margin measured above a furnace that only just melts iron. Anything that increases the margin of success is worth considering.

Dazz

 

Hi
I did some calculations and a modified safety valve would be unsuitable. The fuel flow rate is too low. The mechanism would be tiny.

The rotary valve idea is a much better idea. A small cheap 12V/24V geared motor would be the way to go. The research paper used 10Hz, or 600rpm.
This would be an easy thing to make and retrofit to an existing system. It would be easy to experiment with different on/off ratios and frequency.

There are some very smart people in India so I wouldn't automatically dismiss the concept based on where the paper was written.

Dazz

 

Hi
I have looked at the rotary valve option a bit more.
It would be dead easy to make a pulse valve with variable frequency and on/off ratio.
The valve shaft just needs a tapered end and the ability to adjust the longitudinal position in the body.
See the attached drawings that illustrate the principle.

Some small leakage might be desirable to avoid the risk of flame out with zero flow.

Dazz

 

Why not just take the handle off a ball valve and attach it to a motor?

 

Hi
I can buy a small geared motor and make a rotary valve for less than $USD5.
Dazz

 

I guess I’m a little bit confused. So… I have a lot of questions.

-What material, size, length fuel line will be delivering this pulsed fuel after said rotary valve?
-At what pressure will the gear pump be pumping the fuel?

From my understanding you’re trying to pulse the fuel 10 times a second.
-Is this to vary the pressure and create different spray patterns?

- How are you pumping the fuel (what kind of pump are you using)?
- What type of spray nozzle are you using?

- How are you maintaining the viscosity (at different temperatures) of the fuel? During the whole test.

- How are you measuring fuel flow rate?

- How are you adjusting and maintaining and measuring combustion air?

I’m playing with different viscosities as a moving target at different temperatures and pressures on the fuel. I took one step forward and 10 steps backwards. I might just stick with diesel, or do a dual fuel mixture. One torch with diesel, the second torch WVO. I don’t want to mix the fuels too much.

So far I’ve been keeping them totally separate and saving what I call mixed. I have absolutely no knowledge of the percentage of the mix. I’ve just been saving it in peanut butter jars from the wash through purge with diesel.

 

Hi
I should have explained in more detail.

My drawings shows a pulse valve. It has zero pumping capability.
The drawings illustrate a concept. You would not want to make the valve as drawn.

The purpose of the pulse valve is to take advantage of the effect reported in the research paper linked in post 104.
It would work by rotating the shaft to open/close the path between an inlet hole on one side and an outlet hole on the other.
The shaft would only need to be about 5mm diameter. The geared motor would drive the shaft.
The motor would only need enough power to overcome friction. A small geared $3 12V DC motor would have more than enough power.

The end of the shaft is tapered.
The further the shaft is slid into the hole in the valve body, the more it blocks flow during a revolution.
The further the shaft is slid out, the less it blocks the flow during each revolution.

This pulsing valve would be installed between the pressure (gear) pump output and the nozzle. It could be retrofitted to any pressured burner.

The inclusion of a pulse valve would make operation of the furnace to achieve maximum power a whole lot more complex.
This would be greatly simplified by adding Lambda and temperature transducers to monitor the exhaust. These used to be expensive but not anymore.


Dazz

 

I’m still confused. I don’t think you’ve answered any of my questions.

 

Hi
There is a lot of science and maths applied to multi-variable optimization.
In the absence of that, the practical method would be to hold as many variables constant as practical from melt to melt.
Fuel type (diesel, kero, gas), fuel pressure, metal load, metal type etc.
Then make small adjustments plus and minus to each remaining variable (air flow, pulse ratio and frequency) while monitoring the furnace output temp and Lamba.

Most importantly record all settings.

After doing this often enough a pattern will develop. Based on that pattern, you will be able to predict the settings required during a melt to maximise performance.

This technique assumes there is a single peak or ridge leading to maximum performance. It is entirely possible for multiple performance peaks to exist.

Dazz

 

Very interesting. Can you show a video of how you’re doing this?

 

Hi
Here is an example of a performance map for a gas turbine compressor.
It is a two dimensional map that plots 3 variables:

• gas flow,
• compressor ratio and
• turbine speed.

The map will be corrected to fix variables like air temp/pressure, humidity, fuel, trim etc.
The green line is a ridge line of peak efficiencies.

A similar map could be produced for a furnace where the ridge line would be maximum temp.

Dazz

 

Hi
Give me a few months. I first need to build my first furnace.

Dazz

 

I look forward to your furnace build, fuel delivery build and torch build. I think you’ll have fun.

I thought you didn’t want to use a compressor.... maybe I was mistaken.

 

OK, how big is the furnace going to be? I went, I think medium. 12 inch ID, 14 inches deep. I went as big as I was willing to store. Some pick a container and then work within its limits. From what I found, Not very many people wish they built smaller than 12” x 14” ID.

 

Hi
That is something I need to figure out. I only plan to make small castings.

Dazz