Melchior Posted October 18, 2012 Share Posted October 18, 2012 Hello, I just started up my new T-Rex burner from hybrid burners and tried to tune it. I am new to venturi burners, I have a blown burner setup for welding. How am I to attack this new resource in term of tuning and control? What is your experiences? I tried to tune it yesterday, but I did not see so much difference in the flame that I expected. Moving the flare and MIG tip does not really change the flame and sound much at all. I could not really see any "sweet spot". The T-Rex is an amazing piece of burner, I ran it at 40 PSI for a short period of time and it dug a big hole in my insulation blanket. So I need to reline it already... :) It also seems like the bottom firebrick I am using is absorbing a lot of heat so I need to change it to something better. Also I need to add the refractory stuff and sort out a front door of some kind. Everything to save fuel and heat. Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted October 19, 2012 Share Posted October 19, 2012 Casting the interior with Kast-0-Lite will help with the heat sink problem then paint it with Plistix or Metrikote IR reflective will help even more. The Kast-0-Lite will give you a good tuff forge and is also resistant to flux. Use soft fire bricks for the doors. You need to have a rear opening as well as the front to allow more air in for more complete combustion. This helps reduce back pressure. Quote Link to comment Share on other sites More sharing options...
Frozenforge Posted October 19, 2012 Share Posted October 19, 2012 If you were trying to tune the burner while running at 40psi it would be difficult to see small adjustments. Try tuning it at lower gas pressure 6 to 10 psi maybe. With a venturi burner the size of the exhaust ports on the forge can mess with the tuning on the burner, as Wayne said you dont want back pressure with a venturi burner. You will probably be surprised at how closed the choke will be when tuning he burner at 6psi! On my burner i would roughly estimate that I have 80% of the air blocked off to get a neutral flame. Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted October 19, 2012 Share Posted October 19, 2012 I typically run my 1" T-Rex at 2 to 5 # of pressure. Quote Link to comment Share on other sites More sharing options...
Melchior Posted October 20, 2012 Author Share Posted October 20, 2012 I will add some refractory to get the efficiency up a bit. Then add a door using soft bricks as you recommend. I do not want to open up the back door right now. I prefer a bigger front door. But as you say, it may be necessary to add an opening. The Kast-0-Lite is really interesting, I will try to get my hands on it here in Europe. Many Thanks! /E Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 23, 2012 Share Posted October 23, 2012 /E: When you're tuning naturally aspirated burners only do ONE thing at a time! Doing more than one at a time and you'll never know what caused what to happen. You shouldn't have to adjust the jet or flare on a Rex burner, the basic device should come set correctly and only need a little adjustment, unless it got banged around in shipping. The main concern is back pressure but with a large door that should be okay. However if you have it aimed perpendicular to a face in the forge and too close back pressure, perhaps rebound back pressure is a better term, WILL cause poor operation. ESPECIALLY at 40 psi. There really shouldn't be many things you'll be doing in a forge requiring THAT much fire. What's your forge's volume? A 3/4" Rex will bring 350 cu/in to welding heat at around 15 psi. depending on variables like altitude, intake air temp, etc. A 1" Rex will bring 700+ cu/in to welding heat at around 15 psi. These are good burners and should work well right out of the box. Mess with HOW you're using it before you start messing with the burner itself. And NO I don't have a Rex, I make my own ejector type naturally aspirated burners. Venturi is a misnomer, there are no venturis in a Rex, a Michael Porter type 5, any of Ron Reil's linear burners or mine. They're basic home made, simple induction devices running propane through the jets. The navy uses similar inducers made from pipe running steam to pump large amounts of water. Okay, that's getting carried away. Post some pics of the flame in your forge and I'll be able to give you a much better idea of what's going on and what to do about it. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Melchior Posted October 23, 2012 Author Share Posted October 23, 2012 Hello, The T-Rex came unassembled with instructions on how to assemble and tune it. The flare setting did not make much of a difference at 10PSI. So I set it to the recommended setting. Then I tried to see changes in the burn when moving the nozzle back and forth, but this did not make any noticeable difference, so I also set it to the recommended setting. My forge volume is about 300-350 cubic inches. So it is working nicely without any indications of back pressure. It did weld at 5 PSI so I do not think I am much off on the settings, but I am not sure. So the correct term for this kind of burner is "Ejector type" or "Naturally aspirated burner"? Why is it not a Venturi burner? I am curious, I have googled it and it seems like the Venturi effect is achieved when the tube has a "waist" in it to force a change in the pressure. I will post pics and better videos tomorrow when I am in the shop again for another go at the tuning. The first video I made did not get the brightness correct so I could not see the flame characteristics. Thank you for all the input. Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 23, 2012 Share Posted October 23, 2012 Sounds like you have it running properly if it welds at 5psi. Does it scale steel while in the fire? Okay, yeah "Ejector" inducer is the correct industry term and I think I'm the only one in blacksmithingdom that uses it. The reason it's not a venturi burner is not because bernoulli's principle as described by Venturi isn't at work however a proper Venturi device uses the large quantity of gas or liquid to induce the smaller quantity into the device at or just behind the "venturi." The venturi in a carburator is the best example I can think of at the moment. The engine draws air in through the "barrel(s)" Barrels are what we call the large air intake port behind the air filter. Part way in there is a smooth ridge running around the inside of the barrel which not only narrows the intake diameter but forms an airfoil. Venturi's enhancement to Burnulli's descriptions of the fluid laws states simply that any fluid, gasses count as they behave the same way, flowing over a curved surface accelerates with a concurrent pressure drop. So, as air is drawn into the carburator a partial vacuum forms at the crest of the foil (Venturi) which draws fuel into the air flow. So, what does the fuel PUMP do? It keeps the float chambers full it doesn't force fuel into the carburator. none of this applies to fuel injected engines of course. Okay, Naturally Aspirated has little to do with it being an ejector or linear, "Naturally Aspirated" means it draws air without being forced into the device. Aspirated means to "be breathed in" or in this case "Breathing in by it's own power" Aspire means inhale and has a root "Spirit" from the Greek, "Espiritus." meaning devine breath. The burner industry has it's own established terms for both naturally aspirated and gun (blown) burners. While naturally aspirated and gun aren't "wrong" they aren't the "correct" industry terms. Okay, is that way more than you wanted to know or what? I should have something in my sign off warning folks I get going easily and am long winded. <grin> Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Melchior Posted November 3, 2012 Author Share Posted November 3, 2012 Ah, great information. Just what I wanted. But one thing eludes me, what do you actually want to call this type of burner? Ejector burner seems to be the closest name for it if I understand the information that you have given. Here is a video of when I am tuning the burner. Notice how to burner sounds different and the flame changes. What would you say is an ideal setting for this burner? Can you note the time in the video where it runs as "it should"? Slightly rich mixture to prevent oxidation. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 5, 2012 Share Posted November 5, 2012 Melchior---what is the ideal speed to run your car at? Does it matter if you are on a bad dirt road or on the unlimited section of the Autobahn? Give some thought that the burner has NO ideal setting without including what you are doing. I've run my burner everywhere from extreme excess fuel to extreme excess air depending on what *I* was doing. Quote Link to comment Share on other sites More sharing options...
Melchior Posted November 6, 2012 Author Share Posted November 6, 2012 Good point Thomas! I would like to run the burner at the optimal efficiency, eg. as much heat per kilo of propane as possible. Forging knifes. I need as little scales as possible so I want to run it a little rich. Is is so that I need to change how a perceive the efficiency of the burner, it is already efficient in almost all the settings (except when I am reducing the air intake to much and no "jet" stream is formed)? So the most "savings" would be a result of running the burner on as low pressure as possible? /E Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 6, 2012 Share Posted November 6, 2012 You burn less gas at the lowest pressure setting that will heat the forge to the correct temperature---why we often harp on *insulation* as the forge is a heat balance: Heat In vs Heat Out Heat in costs by the minute. Heat out is a one time insulation cost (well until reline time...) and the savings build up fast! I had an old forge with tattered insulation; still worked ok but I had to crank the pressure up. When I relined it it was *melting* work pieces at the same pressure that was "ok" before. You have a good handle on the fact that a balanced burn is the most efficient; however we often nudge it reducing to cut down on scale/decarburization for blademaking. When I tune mine I tune for a balance burn---brightest flame impingement/loudest sound and then nudge it a bit less air for blademaking. I may check the tuning after the forge is up to heat if it looks to have changed slightly. If I'm teaching with the door wide open for multiple people to work at the same time I will up the pressure a bit and retune if needed Quote Link to comment Share on other sites More sharing options...
pkrankow Posted November 6, 2012 Share Posted November 6, 2012 Try this The "neutral" or slightly "rich" is where you should be for general work. Remember when you stick it in a forge cavity the setting in open air may not be correct anymore. The dragon's breath from the forge door should look similar to your blown forge when running at a similar setting. Phil Quote Link to comment Share on other sites More sharing options...
Melchior Posted November 7, 2012 Author Share Posted November 7, 2012 Understood. I think I understand the general idea regarding efficiency and tuning. So I will start with properly insulating the forge using the refractory cement and also try to change the bottom protection plate to something that does not absorb so much energy. Thank you for the information. /E Quote Link to comment Share on other sites More sharing options...
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