naturally aspirated burner

Hey guys! I took some time this weekend to build a burner. It is naturally aspirated and seems to work better than I had anticipated being my first attempt at building my own. After I built the burner I had to test it, so I built a small prototype furnace out of an old ten gallon propane tank. I liked the rotation I got with my flame inside the furnace but did notice that inside the furnace my flame was bluish green and when I put the lid on the flame went out. I know that there will be a little experimenting on air to gas ratio, and that each furnace and burner will be a slightly different, so my question is...what is a good starting point for gas pressure? I seemed to do well anywhere from 5 to 2o psi but each time I stuck the lid on I put the flame out. Any tips on start up setting?

 

The flame goes out when you put the lid on the furnace ? Well, that is due to the back pressure inside the furnace, the air cannot escape fast enough through the vent hole. Keep the lid open for a while or put a brick between the lid to have temporary more exhaust volume. When it is red hot, you can close the lid entirely.

Probably forced air will work better and is hotter anyway.

 

I was thinking I may have too much air going in, but I did not have refractory in furnace yet so didnt want it to get too hot. I hope to do refractory this week and try it again this weekend where I can play around with getting temp higher. Would forced air have the same issues? Still need to get hot before turning on forced air? I also have all the parts to convert over to oil and forced air if I desire, but would rather use propane as the other fuel sources are hard to get or more expensive here.

 

Billy,
The most important factor is the direction of the flame around the furnace. Northern hemisphere has to go anti-clockwise. Our friends south of the equator have to go clockwise, otherwise the flame will want to shoot out the back of the burner tube. That happened to me with my first furnace but since I got it squared away it's been working great.

Pete

Just busting your ass!

 

LOL. In colder climates the air tends to want to twist and burn clockwise. This is an old wives tale. If you have a blower it really depends on the blowers rotation and how close the blower is and its type of construction.

Naturally aspirated burners are very difficult when they get confined too much. They need more radiant heat inside the furnace to adjust to flu control. Slowly closing the lid and getting your temperatures up helps.

This is where pumped air gets temperatures up quicker with fuel rates higher. You can dial back the fuel rate or air shortly after you maintain a good flame coming out the flu. Then you can juice one or both of them up slightly.

 

Why the fascination with naturally aspirated? Stick a hair dryer that thing and watch temps skyrocket! Leave the naturally aspirated burner crap to the monkeys that beat metal into knives.
If you wanna melt metal, you are building a furnace, not a forge.

 

Those are bigger words than I wanted to use. But they are very well accurate. Almost 200 years ago forced air was implemented for forges and furnaces. The more air you pump into either or, the more rage you get from the fuel.

The hotter and dryer of the air you are pumping in with more oxygen can amplify this... Of course a hairdryer that has hot air being pumped into the furnace or forge would have more detrimental meltdown effect utilizing 20% of the oxygen.

 

I say a hairdryer because anyone with a woman in the house has one. A cold air charge is always better because cold air is more dense. Runways get much shorter for me on a hot day. I have a trip soon to an airport at 7000ft field elevation. You can bet your ass I'm opening the book on that takeoff.

 

There was a helicopter cattle mustering company in my state that bought an experimental three bladed rotor for a Bell 47 to compensate for hot weather operation. One day the engineers had fitted it to the helicopter and were still working on it, they stopped for lunch and while they were having lunch, the company owner jumped into the helicopter and started it up and tried to take off. Unfortunately the Jesus nut hadn't been fitted and the main rotor took off like one of those kid's toys, flew a short distance and smashed itself on the ground. The owner quietly got out of the helicopter and walked back into his office without saying as word and the episode was never spoken of again .

Edit: forced air is the way to go for a high rate of burn needed for brass and iron.

 

So...I should have made the inlet for the burner on the left side of the furnace so it will rotate clockwise. Got it! I think I will add one to both sides so I am not limited by which side of the hemisphere I am located on.LOL

 

I'm fascinated by all forms of melting and forging and fabrication in general.LOL I will most likely add compressed air after I get the natural flow mastered. Probably going to start off with aluminum to make parts to use and gradually climb up the ladder to iron. But in general since this is my first build I figured I would start off basic and work my way up.

 

I can easily adapt one to my burner. I almost feel like I am getting to much air now without a lining in the furnace I cant really heat it up too much, but I got 4 bags of uniram so it will be lined by this weekend and I will be able to set it up properly.
I have never flown a real airplane but have about 100 RC that I never fly anymore....actually thought about getting pilots license one day. Kind of lost interest after my two year old was born.

 

I like simple. It's much easier to explain to the onlookers.LOL

 

Running the furnace burner (anti)clockwise has nothing to do with on which hemisphere you are on. That only applies to low and high pressure weather systems in the atmosphere, i.e. cyclones run anticlockwise in the northern hemisphere and clockwise in the southern. But a furnace does not matter.

Indeed, that is OK for a forge or an aluminum melting furnace, and in some cases for brass or copper when the burner is tuned very well. See BigstackD's Youtube channel, he has a Devil's Forge (actually a furnace) and reaches 1300 C without forced air.

I use a very simple $10 12 volts air mattress inflator as air supply to the propane with a lamp dimmer to regulate it. Works fine !

 

I think I will go in the opposite direction of the earths rotation. That should make it rotate much faster. I could add suction on the lid vent tangent with the rotation as well.


Jus kiddin

 

I ran A hobbimelter with the Naturally ASpirated Burner Leonard shipped with it for a couple of years for Brass, moved up to a 1 inch Trex (lots of bragging ) with no improvement , went to my current forced air rig and cut my melt times by a third 1:30, to 50 minutes

V/r HT1

 

I

I have a few things I could use for a blower instead of using compressed air. Would be better than having the compressor kick on and off every few minutes. I can easily adapt one to my burner and see how it goes. I am hoping to get it finished this week and try it out this weekend. I already see the need for a bigger one though. I suspect that is the case with most people.LOL

 

Something may have gotten lost in translation. The discussion was meant as a joke.lol

Pete