Hello Forum I copied a propane furnace that I found online. It starts up and runs but, doesn't get hot enough for reasons of lack of forced air. Seems to me that the addition of air at the gas inlet would cause the flame to occur outside the fire box and at the air/fuel mix location. Would someone be so kind to point me in a direction where I could advance my project to incorporate forced air. Thank you
Some more detail of your furnace and with photos would be helpful in diagnosing any issues. Forced air gas fueled furnaces are fairly straightforward and can be as simple as a gas pipe entering the tuyere. The combustion still occurs in the chamber as the airflow in the inlet tuyere is usually faster than the flame propagation speed of the fuel gas.
Excuse me. Please find the attached pictures. Chamber measures; 10" diameter, 12" verticle height refractory lined I'm running a 20lb regulator Thank you!
Hot enough for what? To melt aluminum? Bronze? Iron? What's the size of the main burner tube? What's the size of the fuel orifice? . It'd be helpful if you had a picture of the burner flame. Besides the question above, just observing your burner, the fuel tube looks to be a bit askew in the burner opening. Both the center alignment and axial position can significantly affect burner performance, but a naturally aspirated burner won't be able to achieve the temps of a forced air burner. Best, Kelly
Thanks for the photos, you may need a higher flow rate regulator than a standard unit. There are adjustable higher flow rate units that the pottery crowd use for their kilns that are suitable. Hopefully other forum members can weigh in on this topic as I've only ever used forced air gas furnaces.
Hello Kelly Thank you for responding! Yes, I know it's sorta kinda ghetto.......It's a project that's been in mothballs for a while. Intended for melting aluminum or bronze. Am I incorrect to believe that this furnace is starving for air? A blower on a rheostat is my first inclination. Where and how to make the tie in? Yes, the fuel tube is out of alignment. Now realigned. Diameter of fuel tube; 1" black pipe Fuel orifice; 0.0625" hole. Picture of; fuel orifice and flame attached Hopefully video attaches; https://na01.safelinks.protection.outlook.com/?url=https://photos.app.goo.gl/e4GooeUdnz4HZ3N67&data=05|02||f4f2bf8e8599486b3d1308dcb2ecbc46|84df9e7fe9f640afb435aaaaaaaaaaaa|1|0|638581977043910522|Unknown|TWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0=|0|||&sdata=TDDrYjFa3xDEKzGzP1JsmySMZG11WtKpK3fnaZFmDyI=&reserved=0
I think that orifice might be too large, that'll slow down the speed of the fuel entering the burner and that in turn reduces the amount of air. I've been using a .035" mig tip as an orifice, that works well for me. My burner has a 3/4"npt tube and using a 0-15psi regulator, I'm able to adjust anywhere from a slow, lazy flame to a forceful, slightly lean flame.
Do you have a suggestion for adding forced air. My thoughts were to fab in a blackpipe "Y" somewhere along the fuel gas piping. I'm not sure if the flame will "land" Thank you for the mig tip suggestion
There's no doubt there is higher heat potential with a forced air burner, but whether forced air or naturally aspirated (NA), the burner still needs to be in good tune or neither will perform well. Since the primary aim is just aluminum and bronze, before, you switch directions, you might want to make sure you have a decent tune on your present burner. There's nothing wrong with pipe fitting burners and a 1" diameter pipe burner can supply a lot of heat for that size furnace. Though forced air burners have higher heat potential, it does add the need for electricity which can be a bit inconvenient. NA burners are ejectors and for a given fuel flow, ejectors need the highest velocity fuel/ gas stream possible to be the most efficient, so the mig tip suggestion will help, but the tip still needs to be positioned properly. There are higher pressure regulators but 20 psig is within the range many run with good success. As opposed to the in-furnace burner video, most experiment with burner tuning outside the furnace first. You will need to put a flare on the end of the burner to support flame outside the furnace. A flare is just a short section larger in diameter than the burner tube. Most just use a pipe coupling that threads onto the end, then remove it to reinstall in the furnace. Then observe color and shape of the flame. In your case, you can only adjust fuel flow to adjust tune. If you search this site or YouTube, there will be descriptions of flame for a given burn, lean/rich, oxidizing/reducing. You want slightly oxidizing for aluminum and reducing for bronze. Best, Kelly
Electricity is no problem...........Before doing anything, I'll step down the size of the orifice and "tune" as recommended. Flaring included. In addition to not getting hot enough, the behavior of the flame (sometimes; unsteady/erratic, flame outs, orange and occasional blue) leads me to believe "controlled" forced air will eliminate those previously mentioned issues. Thanks for the advice on the; lean/rich, oxidizing/reducing flames. Question is, where to place the air injection point in relation to the fuel gas orifice please so that I keep the flame in the furnace box and not in the tube? Thanks again! jerry
This is a simple burner for forced air. You can either use a mig tip or a #60 drill bit. If you use a mig tip the cross pipe has to be close enough to the end to thread it on after putting the pipe in the tube. Make sure the tip or hole is pointed down the pipe and solder it in place.
One thing to try that works for both forced air and naturally aspirated burners is to drill a tiny hole through the furnace wall and fit a K type thermocouple away from the direct burner flames. You can then tune the burner for the fastest rate of temperature rise. There are $10 ceramic sheath K type thermocouples and basic digital displays for $5 on Ali Express. I discovered that for my oil furnace, a blue flame was way too lean and a richer orange flame gave the fastest rate of temp rise.
K type thermocouple ........... love it https://www.amazon.com/T-PRO-Thermo...b70-a84d-d5663bd3a2f4&pd_rd_i=B0748DFJFN&th=1
If you want to add more air to to your burner you need to modify yor burner. Here's my solution to the need for more air. You need to do a little more cutting on your burner. Mix and match, 4 pipe burners | The Home Foundry Sorry, this starts at the bottom of the thread and you need to scroll all the way to the top. Fred,
The thermocouple gives some certainty to experimenting and tuning the furnace burner and may not be needed once you have a working setup. These are what I'm currently using: the thermocouple has a ceramic sheath and thicker wires so it's a bit rugged but will melt at bang on 1350 degrees C. https://www.aliexpress.com/item/1005006524855756.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.4.21f83SkM3SkMhP&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=7527cff2-03d7-4522-82cc-dd65a6f44007&_t=gps-idcDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:7527cff2-03d7-4522-82cc-dd65a6f44007,tpp_buckets:668#2846#8113#1998&pdp_npi=4@dis!AUD!12.26!12.26!!!56.91!56.91!@2101c59517226840585604463e60bd!12000037526975530!rec!AU!702414536!X&utparam-url=scenecDetailTopMoreOtherSeller|query_from: These displays are cheap but need padding on the battery to keep the AAA cells in place. https://www.aliexpress.com/item/1005005593821417.html?spm=a2g0o.productlist.main.1.207cK3YKK3YKql&algo_pvid=9b018b4a-7472-4804-8254-eada293539a1&algo_exp_id=9b018b4a-7472-4804-8254-eada293539a1-0&pdp_npi=4@dis!AUD!5.48!5.48!!!25.42!25.42!@2101fb1317226839356408311e7a4c!12000033747663729!sea!AU!702414536!X&curPageLogUid=ZmMNDeS5GvWU&utparam-url=scene:search|query_from:
Been under the weather for the past few days, sorry that I haven't responded. At the moment, I'm considering not going forced air (novice experience/knowledge level) At this point I'll remain N/A and advance with redesigning the current burner to incorporate forum suggestions. Recognizing that my current burner is downright ghetto, I scoured YouTube and found a build version that is much more sophisticated (burner with an adjustable air inlet) Kelly stated; "You will need to put a flare on the end of the burner to support flame outside the furnace" (as in the video) The suggestion of adding a thermocouple and the smaller fuel orifice (mig tip) Until then burner work is inprogreee Thanks again Jerry
Yes, if you get the ejector highly tuned, it can entrain more air than optimal for the burn. A choke on the inlet adds an added degree of tunability. Lots of ways to do that. Many just use a disc with a threaded/adjustable distance from the burner inlet like in your video. Adapting barrel and carburetor butterfly valves is also fairly common. NA burner can be decent performers but can also be a little more sensitive to back pressure in the furnace. Once you get a little experience with your burner, pretty hard to beat them for simplicity. Best, Kelly
