BOILER BURNER UPDATE:
Well, looks like burner number 3 was a bust because after it is placed into the boiler burner tube for over 20 minutes, the stainless screen becomes too hot and 'back burning' occurs. It sounds like an afterburner with a real loud roar. I tried to place the screen/screens in all different positions and burner tube lengths, but it did not prevent the back burning. Why?...because the whole burner heats up too much and the thin screen can not dissipate the heat well enough to prevent ignition of the gas before the tiny pores of the screen. This only happens when the burner is inside the burner tube where the air circulation is directional and minimized.
So..how to fix?.... Addressing the back burning first: The 4th design incorporates a .3 in thick brass slug with 150 #54 holes drilled through. The .3 in length is arbitrary but seems more than thick enough to prevent gas burning through the pores even when hot. This slug was then pressed into the end of the short tube and tested. This burned well but not really hot. Took a while to get the boiler going. So back to the long tube with an axial gas flow design. Beveled base port mixes air/gas well with the longer tube. The collar is for air adjustment with several different air hole sizes tried as well.
Then, when things started looking good, the 'long' burner was placed into the boiler and WOW boiler tube harmonics and a standing wave with the burner jet created the worst loud whistle(like a flute). When the burner was far enough out to stop the whistle, it was too far out of the boiler. The standing wave actually compressed the flame decreasing heat when in too far...so..back to the drawing board.
I decided to press the brass slug back into the long burner tube about 1/2 inch. This significantly decreased the standing wave nearly to nill, but the burner was now running poorly due to lack of oxygen at tip.
Next, I drilled 8 holes ~3/8 around the burner tip to allow air into the flame. WOW!! this was it. Now the 1/4 inch gap around the burner (when inside the boiler tube) really supplies air into the burner tip and the burner roars out the end with a really hot flame. Almost all of the orange glow is gone and the flame base is blue/white in color and dancing well on the brass slug!! The boiler really heats up well now, and with the wood lagging. The flame is hot enough to melt brazing sivler rod if placed in the flame three inches or closer to the slug end. However, it does not seem hot enough to melt the cross tube brazing due to the water drawing heat away. Burner can be turned down to less heat if needed by bottle valve.
Pics show the attempts, and vid the final iteration.
see vid.
[ame="http://www.youtube.com/watch?v=JTg72W_h630"]http://www.youtube.com/watch?v=JTg72W_h630[/ame]
All 2-56 screws stainless. 3 set the slug and three set the tube. tube and base brass. Air collar bronze
Well, looks like burner number 3 was a bust because after it is placed into the boiler burner tube for over 20 minutes, the stainless screen becomes too hot and 'back burning' occurs. It sounds like an afterburner with a real loud roar. I tried to place the screen/screens in all different positions and burner tube lengths, but it did not prevent the back burning. Why?...because the whole burner heats up too much and the thin screen can not dissipate the heat well enough to prevent ignition of the gas before the tiny pores of the screen. This only happens when the burner is inside the burner tube where the air circulation is directional and minimized.
So..how to fix?.... Addressing the back burning first: The 4th design incorporates a .3 in thick brass slug with 150 #54 holes drilled through. The .3 in length is arbitrary but seems more than thick enough to prevent gas burning through the pores even when hot. This slug was then pressed into the end of the short tube and tested. This burned well but not really hot. Took a while to get the boiler going. So back to the long tube with an axial gas flow design. Beveled base port mixes air/gas well with the longer tube. The collar is for air adjustment with several different air hole sizes tried as well.
Then, when things started looking good, the 'long' burner was placed into the boiler and WOW boiler tube harmonics and a standing wave with the burner jet created the worst loud whistle(like a flute). When the burner was far enough out to stop the whistle, it was too far out of the boiler. The standing wave actually compressed the flame decreasing heat when in too far...so..back to the drawing board.
I decided to press the brass slug back into the long burner tube about 1/2 inch. This significantly decreased the standing wave nearly to nill, but the burner was now running poorly due to lack of oxygen at tip.
Next, I drilled 8 holes ~3/8 around the burner tip to allow air into the flame. WOW!! this was it. Now the 1/4 inch gap around the burner (when inside the boiler tube) really supplies air into the burner tip and the burner roars out the end with a really hot flame. Almost all of the orange glow is gone and the flame base is blue/white in color and dancing well on the brass slug!! The boiler really heats up well now, and with the wood lagging. The flame is hot enough to melt brazing sivler rod if placed in the flame three inches or closer to the slug end. However, it does not seem hot enough to melt the cross tube brazing due to the water drawing heat away. Burner can be turned down to less heat if needed by bottle valve.
Pics show the attempts, and vid the final iteration.
see vid.
[ame="http://www.youtube.com/watch?v=JTg72W_h630"]http://www.youtube.com/watch?v=JTg72W_h630[/ame]
All 2-56 screws stainless. 3 set the slug and three set the tube. tube and base brass. Air collar bronze
