kraythe Posted January 9, 2012 Share Posted January 9, 2012 .Author's Note: This thread talks about activities and techniques that are DANGEROUS. You use this information at your own risk. I suggest you read the entire thread before embarking on the build. It should be noted that is not a project for a beginner. Look into brick pile forges and building venturi burners to get some experience before tackling something like this. In my previous thread "Ribbon Burner Build" I created a square ribbon burner and learned a lot of things about what makes these things work. One thing that I neglected to include in my calculations was Bernouli's Principle; which states that a gas exiting a small tube into a large tube results in a larger pressure in the bigger tube but slower velocity. When we consider a ribbon burner, this means that the plenum doesn't need to be pressurized by back pressure building in the burner but rather its a natural result of the principle. What it also explains is the performance of the final burner. The numerous 5/16" holes on the exit of the burner are essentially one exit pipe since all will be backed by the same plenum pressure. So applying the principle we see that our 14 holes 5/16" wide comprise an exit pipe about a third of the input pipe. Applying Bernouli's principle it is clear that this means that the exit from the plenum will be three times the velocity (and a third of the pressure) of the gas inflow. Thus the reason that the burner has such a high velocity and hard time staying lit. Furthermore, since each jet is a flat casted tube, the burner lacks the dynamics of the traditional burner's flare to slow down the gas and balance flame front velocity. Another lesson learned is the cumbersome nature of a square burner. With the square burner, the forge dimensions must be accurate on all four sides to accommodate the burner. This leaves us with precious little tolerance for fitting. A perfectly round burner would work better. Additionally the structure of burner requires that there is little contact surface between the castable and the burner itself, only a small ridge and ¾" of metal around the edge. This will weaken the burner's ability to handle thermal shock. Also with the way it is cast, the square burner is prone to error in the depth and efficiency it is set in the castable; if a builder makes a small adjustment or the castable doesn't flow and resettle over the burner properly, it won't work properly and could break. A potential castable failure is another problem of that design. With the manner in which it is cast, a catastrophic castable failure would result in a complete failure of the plenum enclosure and thus a very bad result. as propane is dumped in at high pressure. The forge could suddenly burst in propane resulting in bad consequences. So clearly we need to work on a superior design. Thus is the Three Inch Round Pressurized Plenum Multi-Jet Burner (Ribbon Burner) Born. I started on my cad system planning the Burner. I planned to use a 3" inside diameter pipe (3.5" outside) as the size. The burner would be fed by a 1" feed tube and would be built to learn all the past lessons. The burner will have 9 jets that are ⅜" in diameter with ½" flares for each jet. The reason for the calculation of size results from the calculation of feed pipe input to burner jet output pipe size. So I wanted to make sure the jets comprised at least the same area in sum as the feed pipe. The calculation is fairly simply derived from the formula for the area of a circle. Area = πr2. So we want to know how many pipes of diameter x will take to equal a feed pipe of diameter y so: π(y/2)2 / π(x/2)2 ==> (y/2)2 / (x/2)2 ==> (y2/4) / (x2/4) ==> (y2/4) * (4/x2) ==> y2 / x2. From the complex we derive a simple equation courtesy of a little algebra. Putting the numbers in for a 1" feed pipe and a ⅜" output pipe, we get 12 / (⅜)2 ==> 1 / (9/64) ==> 1 * 64/9 ==> 7.111111 jets. So we would need 8 jets to accomplish a jet total diameter equivalent to the feed pipe. Wow. Is Everyone's brain hurting now? Stuffing all of this into my CAD system you have the following Burner. You may note that I included not 8 but 9 jets. The reason is that I wanted to make sure I really had enough output flow to slow it down. In retrospect I might have gone with 8 or even 7. Although the burner works good with 9, as you see later it seems to lack a little velocity. This is a pretty spiffy model but how do we construct it in real life? Well those that use CAD systems know that the easiest way to do a model like this is to whip up a cross section, create a single object from it and then extrude that cross section for the 3d model. I did exactly that and here are the cross sections for the Baffle, Flare and metering plate respectively. The fuel/air mixture enters through the feed pipe in the back then passes through the baffle which is designed to cause turbulence in the stream and make sure the mix is as complete as possible. The fuel/air is then forced through the metering tubes and is forced out into the flare. The flare jets are half inch in diameter, which is the outside diameter of each metering tube. The casted flare will now grip the metering plate, and the edge of the plenum as well as the wall of each of the metering tubes. The metal metering tubes also are a safety mechanism. If the flare were to crack catastrophically and drop into the forge, the metering tubes would still be working as jets and give you time to shut down the burner safely rather than a whole mess of pressurized propane bursting into the forge. To build this burner I selected 3" inside diameter ¼" wall mild steel pipe with ¼" x 4" wide plate to use for the baffle, metering and back plates. The metering tubes are ⅜" inside diameter by 1/16" wall tubing equaling ½" outside diameter. The very heavy materials will let us repeatedly recast the flare as needed. We can even hit a damaged flare with a hammer to break it off due to the plenum's strength. Now its time to build it. We start by cutting 4" of the pipe to serve as the plenum and 12" of the ¼" x 4" flat stock. For the baffle and metering plates we trace the inside of the pipe on the flat stock with the welding pencil. For the back plate we trace the outside of the pipe. Now we take a center punch and clearly mark the drawn circles with push marks. Later when working with the plates, we will be putting the metal under a lot of heat and the pencil or chalk lines could rub off. The punch marks will endure despite OA torch work or anything short of grinding them off. Also note that if you don't have a welding pencil, a permanent marker will do the trick. I have marked over my welding pencil lines in the images with the marker to demonstrate. Use a thin marker or your lines will be erratic. Now the task is to find the middle of the circle and then draw the 45º angle lines which will help us align the punch marks for drilling the holes. At this time I was estimating the best I could for how to do the center so it was slightly off. A day after I had drilled everything I found a geometric and easy way way to find the exact center of any circle. I will talk about that method later so don't start marking yet. My marks were reasonably accurate though I can see them a tiny bit off. I chose the best marked plate to punch for the metering tubes. I measured in along each line from the outside circle one half an inch and punched a mark. For the metering plate, I punched a mark in the middle as well. Now its time to drill the holes for the metering tubes and baffle. You might notice that i haven't cut apart the plates yet. You shouldn't either. The long plate makes it easy to clamp to the drill press securely. Clamping the individual circles would be very difficult. Drill first, then cut. When it comes to drilling I have put a piece of scrap plywood under the plate and adjusted the drill press to stop halfway through the plywood. That way I can make sure I get all the way through the metal as well as not hit my drill press table. I am using Dewalt Titanium drill bits because, frankly, they are awesome. You could theoretically do this with a hand drill but your accuracy will suffer badly. If you don't have a drill press, borrow one. Now its time to cut the hole for the feed pipe in the back plate. A bimetal saw will do this as long as you have a good lead drill bit to guide the hole saw. This will generate a TON of noise and vibration and so I recommend you put on as many clamps as you can and put them on tight. Unfortunately my hole saw rig was damaged and I couldn't use a lead bit. As a result the hole saw wandered off center and skipped a bit. The result would still be acceptable as the burner doesn't have to be centered. However, I am something of a perfectionist for this and I will correct it later. Now we can separate the plates first with a chop saw and then with an OA torch we rough cut out the outer circle of each plate. After that we use an angle grinder and clamp each plate in a vise and then grind down to the dots we punched for the circle (all welder's pencil and ink marks will be long gone). We just keep grinding down and turning the plates in the vise until they are right. To make sure they fit, test fit them in the pipe and grind down as needed. Don't forget to grind a slot for the seam inside the pipe. Then grind the plates clean and shiny for better welding. Now we can install the metering tubes. Cut off a 1 inch piece of tubing for each metering tube and then use a round file to clean off any metal burrs and grind a small bevel in one end of each of the tubes. Then take a hammer and set the beveled end in the metering plate and tap them down with the hammer but don't crush them. If they won't go, file out the hole a bit to make it work. It should be tight and take a hammer to set them but they should go in. Tap each tube down til it hits the metal underneath. All tubes should be flush with the back of the plate. Now using a MIG welder carefully weld around the outside of the metering tubes on the back of the plate. Try not to fill in the tubes too much or you will be filing for a while. Make good welds. Although they don't absolutely need to be gas tight, if you can weld them that way, all the better. Once welded, use a grinder to smooth off the back of the metering plate flat. The picture shows this in progress. Next take a round file and file out the inside of each tube to round again to get rid of any weld material. Now the metering plate is done. You can see the basic "Gatling Gun" structure and the lights from behind show the metering tubes are smooth inside and not obstructed. Now we put the plenum on a flat piece of metal that is at least as wide as the plenum and drop in the metering plate facing down and make sure it is sitting flat. Then we gently tack weld the metering plate in place. Now flip over the plenum and inspect it. The metering tubes should all be in flat with all tubes flush with the edge of the plenum. If it all is good then weld around the side of the plate to permanently mount it in the plenum. Take care to make good welds as gas tight would be beneficial. Try not to obstruct a tube with weld material or you will have to file that out with the round file. Its hard to brush off welds down in the pipe to make it look good but the principles of the weld are important, not its appearance. Now we are back to the problem of the back plate. Recall earlier I had a problem cutting the feed tube hole. I decided to redo it and this time i used my new method to find the center of a circle. It seems that geometrically any chord of a circle can be used to help find its center. A line passing through the halfway point of any chord and perpendicular to the chord must pass through the circle. So once you have pushed the circle, take a ruler and draw a chord exactly two inches long. Mark the 1" center of that chord. Then using a right angle draw a line passing clear through the circle. I used a cheap $5 adjustable metal protractor from Home Depot. Repeat this process and where the two perpendicular lines intersect is the exact center of the circle. Neat huh? I punch a mark at the center and drill a half inch hole (largest drill bit I have) in the middle. Then I draw out a one inch circle centered on the drilled hole. If you have a locking compass this should be easier to do before you drill out the center. Finally I punch the center circle with a center punch and then use the OA torch to cut it out. I file it as smooth as I can get it and then use the OA torch to cut the outside, and then grind it as before. in retrospect a Dremel might have made better work of the center but it doesn't have to be precise as turbulence is actually desired. I could have, of course, just bought another hole saw but now you have two ways to do it. Now its time to install the baffle plate. We measure down 1" into the plenum and mark it with a welding pencil. Then my helper (my son) holds the plate with some needle nose vise grips at the lines and flat so I can tack it in. We check the fit and then weld it in permanently. Next I weld the feed tube to the back plate. For the tube we used a 1" black pipe connector. Do not use a nipple or you will not have much material to weld to. Its better to use a straight connector for its greater metal mass. This weld MUST be gas tight and we will insure that later. Once this is done, we fit it on the plenum and then weld the back plate to the plenum. For this weld make sure you use high heat and probably two passes. Next I pass over the back plate and feed tube welds with an OA torch with a number 3 welding tip. The goal here is just to walk the weld puddle around the plenum and tube. If there are pinholes, they will be filled. If there are voids they will collapse and can be filled from welding rod in your hand. We dipped it in the water to cool it off after it was black again. The dead cricket in the water seems to help. Now I did something a bit boneheaded. Or rather ill timed. We decided to paint the plenum to resist rusting. Good idea to use an engine approved paint for 500º as the plenum shouldn't ever get that hot. So we crafted a box and painted it nicely. It looks great. Except we forgot later we will have to shove the thing in a forge and that will burn off our paint job. Oh well, live and learn. We will paint it again later when it is done. And now the plenum is done! Time to work on the flare. The flare will be cast out of Kastolyte 30 reinforced with stainless steel needles. In retrospect I might have used something a bit more dense but with the same rating. I don't know if a base of kastolyte with a Mizzou last inch would hold together. It might be worth a try. The problem is the kastolyte is an insulating refractory that is soft and the jets at the flare end might be prone to fracturing. Perhaps less jets and more space between jets would help. At any rate, to cast the flare we have to keep castable from getting inside the plenum and also cast ½" jets centered right over the metering tubes. We accomplished this by first trying to epoxy in ⅜" dowels into the plenum and then epoxying ½" dowels on top of the metering tubes. This is shown below but it didn't work well because it was nearly impossible to get the top dowels centered properly and remain perfectly vertical. Back to the drawing board. We took our half inch dowels and sanded them off and drilled out or pressed out the ⅜" dowels inserted in the metering tubes. If they go inside that is ok because they will burn out later. We then throw the plenum in the forge and burn it clean, burning epoxy as well as wood. This is NASTY so have a good ventilation fan! Oh yeah, the paint didn't hold up to the forge. We then decided to glue the ⅜" inserts to the dowel rods first and let them cure 24 hours first. In the meantime we experimented with making a tool out of the tubing used on metering tubes and a drill press. We also tried using sandpaper like a lathe since we only had to take off 1/16". These didn't work as well. I am sure there is a better way to do this to keep the tube perfectly straight but I haven't found one. At any rate our glued dowels worked. One thing we would have done is to sharpen the "up" points of the dowels so the castable would fall easier in between the dowels later. Make sure your dowels clear the top of the flare by at least 3.5". We glue them into the metering tubes with two part epoxy and let cure at least 24 hours. In retrospect would have also made a top plate out of thin wood with holes cut for the dowels for perfect alignment fit after the castable is poured. The pattern for the metering plate would have worked nicely with a larger outside diameter; for materials use the thin wood that you can get from the hardware store with a shiny side. To create the form for the outside of the flare we will use poster board and duct tape. We cut a 5" long slice out of poster board and roll it around the flare so the shiny side is inside. It should roll around several times. Get it nice and tight and tape the roll end. Now slide the new poster board tube up the plenum to make a depth of exactly 3 inches from the plenum pipe edge to the top of the poster board. Its possible you might be able to use a shorter cast but this looked good for insulation reasons. We duct tape the form in place on the plenum then later duct tape to reinforce the poster board all the way up the form. Now its time to mix the castable. We put on respirators (this stuff is bad for you to be breathing) and then my son opens the can we store Kastolyte 30 in and scoops it out into a drywall mud pan for mixing. We then get a couple of handfuls of stainless steel needles that will help reinforce the castable and put them in the dry castable. Now we add water VERY SLOWLY to the pan using a small plastic cup. You will be astonished at how a few drops can change the mix. Put a very small amount in, mix it up like crazy and then very slowly add a thimble full of water at a time. The final consistency should be like thick peanut butter. Now its time to pour. Scoop out the castable and put it right on top of the dowels. If I had sanded them into cones like pencils on top, this would have been easier. Fill the form until its full. Periodically you will have to pick up the burner and rap it solidly against the table repeatedly. This will force the castable mix to settle and fill all gaps. The vibration tamping is important. Without this you could end up with large voids. Just pick it up, keep it upright and rap it against the table several times and add more castable until it is full and even a bit overflowing. Once the form is full you can put on the top alignment form (not shown) tap down the form until its flush against the top of the poster board tube (some castable may squish out but that is ok). Then rap the whole thing against the table a few more times to settle the castable around any rods you have moved. Now you have to wait three days; if its cold where you live, bring it inside where temperature is constant. After three days you can peel off the duct tape and unroll the poster board off the flare. This will let the bottom parts of the flare cure faster. Leave the top plate of the form in place as removing it now could crack the cast. After another day drying its time to bake it. Put the whole thing in a forge you have currently operating or a brick pile quick forge. It doesn't have to be that efficient of a forge. Put the flare in the forge when the forge is cold. Light the forge and let the thing bake. The wood dowels, top plate and epoxy will burn out. This will be NASTY so have good powered ventilation. Now we let it cool in the forge a couple of minutes and use a shop vac in blower mode to blow out ash and charcoal. Keep an eye on where embers go and put them out quickly. A friend helps for this part. Make sure you have a fire extinguisher handy if needed. DO NOT VACCUM THE EMBERS INTO YOUR SHOP VAC. If you do, you are courting a bad fire later. Eventually you might have one or two holes plugged. Use a spare welding rod or metal or whatever to clean it out. At the end you should be able to see smooth bores for the flare and the top of the metering tubes. Now we let the burner cool and very carefully, very gently touch any extraneous ridges with an angle grinder. The grinder will eat through the castable like it is air so be very gentle and quick. There may be some stainless steel needles on top of the flare but they will burn away later so don't stress over them. Now it is time to build the supply pipe. We take a ⅛" brass pipe plug and chuck it in the drill with the dimple side up. Make sure to get the ones with the centered dimple. It will save you some time. We drill a small hole for the propane jet. As will all blown burners the exact size isn't that important. Then we screw that plug into a straight connector, that into a pipe nipple, pass the pipe nipple through a 1" to ½" black or galvanized reducer and through a ½" inch brass plug that has been drilled out to be almost exactly the outside diameter of the brass pipe nipple. We attach the other end of the nipple to a ¼" to ⅛" reducer and an elbow. This assembly we attach to the supply assembly. This consists of a propane hose to the regulator attached to a propane flashback suppressor, then a fuel to pipe thread converter than a ball valve and finally a ¼" brass nipple to the jet assembly. Use propane sealant on all brass connections and check for leaks with child's bubble solution while pressurized. Now we attach our blower (clamp it) to the a pipe to feed the air in. The feed plate is a 2" black iron pip nipple welded to a plate with a 2" hole in it. Then attach the blower feed to a bell reducer then to a gate valve using some pipe nipples and then to an elbow and then another long nipple. The propane feed assembly is attached to the top of a T fitting, the pipe from the blower enters on the leg of the T and the nipple leading to the plenum is on the other leg. This setup allows you to adjust the position of the jet, though I haven't really noticed a difference so I will probably go down to a shorter brass pipe nipple in the jet assembly. Any space around the pipe nipple will leak fuel /air unless you seal it off with duct tape or something else. I am working on a better config that isn't so leaky. Now we attach another elbow and then another nipple and then finally the plenum with its cast flare. We are now ready to test. We start a plumber's torch, set propane to 5 psi, turn on the blower and open the ball valve with the plumber's torch in front of the flare and WHOOSH, it lights. My son is waiting with his hand on the bottle valve, ready to cut the propane if anything bad happens. The flare really roars, all 9 jets are firing. We end up feeling like we aren't getting enough air velocity but even as imperfect as it is, its awesome in its functionality. It totally blows the normal blown burners to heck. I might try plugging one or two jets and seeing what the result is in velocity. The video is sort of on it's side so I hope you will pardon the roughness. I should have filmed it in landscape. Oops. Next we go to test it in a brick pile forge. We rig up a support arm, use hose clamps to attach the feed tube to the arm, mount the blower and move our brick pile to center up the burner. This is not the optimal forge for this burner but it will make a nice test. We close up the forge and shove pieces of insulating block to accommodate the roundness of the burner in the square forge. The burner is a bit low in the forge but for now its fine. We put the plumber's torch flame in the forge and open the ball valve (with the blower on). The burner really rocks the forge. You can see the blue jets in the picture. This forge was running hotter than it ever has and heating up very quick with only 2.5 to 3 psi of propane! After we play around and run it a bout 20 minutes, we see that it heats awesomely. We cut the propane, waited for all to cool, and the took apart the forge to examine the flare. There is some minor breaking around one jet but nothing serious. This is the reason I was thinking of a denser castable next time. When running we heard a couple of times a thump and then a low rumbling. I am not entirely sure what is causing it and I will investigate it. It was a low pitched ruble. This flare could be covered with ITC-100 and used. The extra stainless wires will degrade quickly. I might experiment with fewer jets and tinker with the castable process but the burner performs magnificently. The burner is easy to build, low cost and very durable. If you drop it and break it or the castable cracks due to wear, you can recast it easily. It uses a fraction of the propane of my old blown and venturi burner and the increased surface area of flame allows much better heat transfer into the forge. It is a resounding success. Quote Link to comment Share on other sites More sharing options...
Dodge Posted January 11, 2012 Share Posted January 11, 2012 Neat burner! What is the final gas suppy oriface size? (Jet size) Quote Link to comment Share on other sites More sharing options...
kraythe Posted January 11, 2012 Author Share Posted January 11, 2012 Neat burner! What is the final gas suppy oriface size? (Jet size) Honestly I dont recall. 1mm maybe? I drilled that orafice a heck of a long time ago. Quote Link to comment Share on other sites More sharing options...
prburner Posted January 11, 2012 Share Posted January 11, 2012 Hello kraythe, The thump and low rumble sound you hear means the burner is backburning. All combustion should take place from the face of the burner outward. But when the combustion rate of the fuel mix is greater than the outflow speed of the burner, the fuel mix then burns down inside the burner orifices. If you look at the last picture in your post you can see that the orifices are still glowing red inside, a sure sign that combustion was taking place inside the burner. Backburning will greatly reduce the life of the burner. You are right about rethinking your choice of castable. Kast-o-lite 30 is an insulating castable. It does not have good mechanical strength ("some minor breaking around one jet" after 20 minutes use is a clue). Much better to use a hard refractory castable. Choose one rated for at least 3000 degrees and designed for repeated heating/cooling cycles.Regards, Tom Quote Link to comment Share on other sites More sharing options...
kraythe Posted January 11, 2012 Author Share Posted January 11, 2012 Hmm, are you the pine ridge burners guy? If so that is way cool. Thanks for the information. Thats pretty much what I figured. I am going to have to do some tinkering with the design to make sure that doesnt happen. I have been experimenting with the flare and I think the length of the flared tubes is too long, that they should be 3/8" much further and then flare out perhaps only at the final inch. Unlike the burners you guys sell, I am going for small forge designs and that is kind of a hard thing to do. I actually broke the flare off and the 3/8" jets were able to stay fired in the forge and outside the foge if i turned down the air a lot. At the same time I am wondering what would happen if the flare end was actually metal on the outside, perhaps coated with an ITC coating designed for metal. It is fun experimenting with it. Quote Link to comment Share on other sites More sharing options...
mudbugone Posted February 20, 2012 Share Posted February 20, 2012 I read the square buildup and then found the round buildup here... BOTH are Super I noticed the glowing interior of the burner tubes too and thought that was from internal combustion... Looking at the plumbing lines for the gas injection and the blower air flow wouldn't you get a better airflow (less turbulance) if you swapped the gas injection to where the airflow is connected and the blower where the gas inlet is now mounted and then have a straight flow pattern for the blower. It might increase your pressure..as it's connected the air flow must hit a junction and then switch direction to the left which must cause a great deal of turbulance inside the fuel line and has to cause back pressure(at least lower pressure)issues. That simple adjustment might help eliminate the internal combustion at the burner head. After typing all that I took your lead and checked Tom's website on burners and that's exactly how the airflow lines are connected to their systems with the gas injected into the straight line airflow by a special fuel feed tube mounted in the blower air flow.. Quote Link to comment Share on other sites More sharing options...
kraythe Posted February 27, 2012 Author Share Posted February 27, 2012 Turbulence is good in the mixing part of the pipe. It ensures a complete mix. According to the laws of fluid dynamics you might get a better pressure by removing an elbow but the difference is negligible. The main pressure drop is in the flare tubes. On the other hand I shoved this thing in my brick pile even without the cast flare and it nearly melted iron in the forge. So it does well. I am actually playing with a couple of variants of this. Quote Link to comment Share on other sites More sharing options...
Backhertz Posted April 22, 2018 Share Posted April 22, 2018 Anyway to see the pics? i Quote Link to comment Share on other sites More sharing options...
Frosty Posted April 22, 2018 Share Posted April 22, 2018 Check the date, the last post was 6 years ago. Pics are long gone with an OS change. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted April 22, 2018 Share Posted April 22, 2018 Check out the Ribbon Burner attachment at the Forge Supplies page on my web-site. Let me know if I can help. Wayne Quote Link to comment Share on other sites More sharing options...
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