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Good point. I really like having the union, but maybe a quicker disconnect elsewhere is a better plan.

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Eliminating the elbow I had

That part just registered in my head...

The elbow was the problem before, not the length. Blown burners can turn corners, Venturi burners cannot!

 

Jerrod may already know the physics, but for the sake of the overall thread:

The orderly passage of the gas through a straight tube (Laminar Flow) is essential to maintain the gas velocity established by the high pressure fuel gas injection. That velocity lowers the relative pressure inside the tube, which atmospheric pressure then rushes to fill (Venturi Effect). Additional air is also pulled in by the atmospheric friction created by the air rushing to fill the low pressure (Entrainment). The combination of the Venturi Effect and Entrainment determines how much atmospheric air is available for combustion.

 

Anything that disrupts that orderly flow (converting all or part of the air stream to a Turbulent Flow) decreases the velocity dramatically, well beyond the reduction caused by the additional friction on it's own. Engineers working super-critical applications like aerospace, would even go so far as to remove the weld bead running down the inside of the pipe... and then polish it to remove any burrs.

 

Incidentally, this is also why I emphasize having the gas injection nozzle projecting all the way into the start of the final tube of the burner. That way it avoids turbulence induced by transitioning through the reducer bushings and stays in front of the turbulent inflow of atmospheric air through the T junction, allowing that air to stabilize into more of a laminar flow before joining the fuel gas.

James

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That part just registered in my head...

The elbow was the problem before, not the length. Blown burners can turn corners, Venturi burners cannot!

 

Jerrod may already know the physics, but for the sake of the overall thread:

The orderly passage of the gas through a straight tube (Laminar Flow) is essential to maintain the gas velocity established by the high pressure fuel gas injection. That velocity lowers the relative pressure inside the tube, which atmospheric pressure then rushes to fill (Venturi Effect). Additional air is also pulled in by the atmospheric friction created by the air rushing to fill the low pressure (Entrainment). The combination of the Venturi Effect and Entrainment determines how much atmospheric air is available for combustion.

 

Anything that disrupts that orderly flow (converting all or part of the air stream to a Turbulent Flow) decreases the velocity dramatically, well beyond the reduction caused by the additional friction on it's own. Engineers working super-critical applications like aerospace, would even go so far as to remove the weld bead running down the inside of the pipe... and then polish it to remove any burrs.

 

Incidentally, this is also why I emphasize having the gas injection nozzle projecting all the way into the start of the final tube of the burner. That way it avoids turbulence induced by transitioning through the reducer bushings and stays in front of the turbulent inflow of atmospheric air through the T junction, allowing that air to stabilize into more of a laminar flow before joining the fuel gas.

James

 

Point of fact, they might dimple it ;).

 

Well said though, lol...I'm just being contrary today :D.

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Btw, I just built a burner almost exactly like this less than two weeks ago lol. Mine doesn't protrude down into the 3/4" burner tube however. I may need to adjust that!

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Point of fact, they might dimple it ;).

Well said though, lol...I'm just being contrary today :D.

You are thinking about certain objects traveling through air (like golf balls) that utilize dimpling to generate specific patterns of turbulence capable of providing lift.

 

They would not use dimples in a burner tube application since there is no pattern of turbulence I am aware of that would be beneficial to create.

 

(Sorry, no smilies, posting from my phone.)

James

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Actually dimpling and/or a roughened surface is very useful for increasing airflow and air speed within a port (which is what our burner tubes are). The idea is that air has less friction than the surface if virtually any other medium, and so by creating a thin layer of turbulence via a regular patterning of dimples or roughness, the air that is not disrupted will see significant gains in air speed and so, overall CFM. The idea isn't to promote lift, but to make the tube more 'slippery' for want of a better word, to reduce the overall coefficient of friction, and increase airflow. I've used this method to not only direct air, but to also improve the CFM rating of cylinder heads I've ported.I also do it on piston tops and even in the chamber to increase burn efficiency after having run an engine and looking at the flame pattern witness marks. I've seen as much as 20cfm on open ports (again, what we have here) at 28" of depression.

As I said though...I was just being contrary lol. The applications do have many similarities however, both in the need to turn the air from the inlet to the burner tube (port opening and past the valve into the chamber), as well as wanting as much airflow as possible. The main difference is wet flow vs dry flow...but the gains I saw were in a dry flow testing scenario, vs wet flow testing. This is why you will never see a mirror polished intake port on a professionally built motor. Here is an example of the kind of roughness I mean, in a finish ported intake manifold.

port_intake1.jpg

:)

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I sit corrected! :huh:

When I read your earlier post I was imagining dimples the size you might see on a golf ball, which are as small as think I could produce with a drill, but would be way overdone for what you actually meant. :blink:

With this explanation, I can see how that would work with the uniform and reasonably polished tiny dimples in your example pic. ;)

 

And no worries on playing the contrarian, tis a role that needs must be played and you play him well. :D

James

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I sit corrected! :huh:

When I read your earlier post I was imagining dimples the size you might see on a golf ball, which are as small as think I could produce with a drill, but would be way overdone for what you actually meant. :blink:

With this explanation, I can see how that would work with the uniform and reasonably polished tiny dimples in your example pic. ;)

 

And no worries on playing the contrarian, tis a role that needs must be played and you play him well. :D

James

No worries!

 

I'm about to be contrary again lol...

 

Golf ball dimples will work as well, particularly for rich mixture wet flow applications. It makes the 'boundary layer' thicker, decreasing overall effective port volume, but helps reduce puddling and increases overall flow. I just never used it because it's too difficult to get even dimples inside a port for an average guy...thus the low grit port walls to get a similar net effect. This kind of stuff is F1 car level and higher, where an engine can cost $250,000, and set of cylinder heads an easy 40% of that lol.

 

dimples_3_zps8462d1dc.jpg

dimple%20cylinder%20head%20porting_zpsmr

 

 

Edit ~ I'm also very grateful you're taking this as intended!! It's all in fun and for general education, plus it's great trivia lol. I actually built a burner very much like yours last week without seeing this thread, but have been using it to help me fine tune my work since. Your efforts are very much appreciated my friend!

Edited by C.Anderson

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I don't want this thread to go any further afield, but this topic is quite interesting to me, so I will shift my remaining questions to private messages. Unless Chris wants to start a new thread to continue the discussion. :ph34r:

 

To bring this back to the topic:

Bottom line as I now understand it, for a "regular" garage or shop built Venturi burner, you don't need to polish your burner tube :huh: , but I wouldn't recommend attempting to dimple it either. :blink::wacko::unsure: (That sounds so wrong...it must be right.)

 

Unless you can do so in a well patterned and extremely uniform coverage, dimples are not likely to improve performance and could be severely detrimental.

 

The two best keys to high performance that I have found are:

Keep the tube and gas injection assembly as concentric (centered) as possible and

Extend the gas injector past the air inlet and into the final tube of the burner.

 

Those details eliminate the most common causes of excessive turbulence and help maintain the gas velocity required to optimize the flow of the fuel gas/air mixture. This should give a mildly oxidizing atmosphere when operated with the air damper "wide open" at lower propane settings and strongly oxidizing atmosphere if the propane regulator is set around 10 psi or above. I find that condition offers the greatest range of temperature control (achieved by adjusting propane pressures) along with excellent atmosphere control (achieved by adjusting the air damper).

James

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I don't want this thread to go any further afield, but this topic is quite interesting to me, so I will shift my remaining questions to private messages. Unless Chris wants to start a new thread to continue the discussion. :ph34r:

 

To bring this back to the topic:

Bottom line as I now understand it, for a "regular" garage or shop built Venturi burner, you don't need to polish your burner tube :huh: , but I wouldn't recommend attempting to dimple it either. :blink::wacko::unsure: (That sounds so wrong...it must be right.)

 

Unless you can do so in a well patterned and extremely uniform coverage, dimples are not likely to improve performance and could be severely detrimental.

 

The two best keys to high performance that I have found are:

Keep the tube and gas injection assembly as concentric (centered) as possible and

Extend the gas injector past the air inlet and into the final tube of the burner.

 

Those details eliminate the most common causes of excessive turbulence and help maintain the gas velocity required to optimize the flow of the fuel gas/air mixture. This should give a mildly oxidizing atmosphere when operated with the air damper "wide open" at lower propane settings and strongly oxidizing atmosphere if the propane regulator is set around 10 psi or above. I find that condition offers the greatest range of temperature control (achieved by adjusting propane pressures) along with excellent atmosphere control (achieved by adjusting the air damper).

James

Tomorrow I'm picking up the required parts to extend my injection nozzle down into the 3/4" port. I think that one thing, along with adding a port, will make the biggest difference in my burner's efficiency. I am at 300ci right now, and *should* be able to weld once I get things set.

 

I'm also ordering some new tapered nozzles with bigger thread diameter that *should* be able to thread right into a tapped 1/8" brass nipple. This will help keep things concentric also. I'm currently using a .036" diameter orifice...but have the choice of .023", .030", and .036" in the form factor I'm looking at.

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So is 1/8 nfp the same as 1/8 npt? And where should I worry about loose threads and over cutting of said threads, I ask in this awesome thread

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Yes I believe NFP and NPT are the same.

 

All of the brass parts should fit together as cleanly as possible to give a straight assembly without any "play" in the joints.

Go slow, use a light cutting oil or WD40 and turn the taps with a T wrench by hand, not a powered drill or driver. Do that and clear the chips by backing the tap out a quarter turn for every turn or two of cutting and you shouldn't have any significant issues.

 

The threads for the air damper spring/screw assembly are less critical, just don't blow out the side of the rim on the black iron fitting when drilling the hole.

 

James

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Hi james! 

just to let you know that I used your plans for my first propane forge and it works great! thank you so much for sharing!

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7 hours ago, Joël Mercier said:

Hi james! 

just to let you know that I used your plans for my first propane forge and it works great! thank you so much for sharing!

That's great to hear. Congrats!

James

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OK...I started gathering parts of this burner build and have a few questions.  

One note:  In order to get the 1 1/4" opening on the T (the side where the propane connects) I had to use 3 reducers...from 1 1/4 to 3/4, then 3/4" to 3/8", then 3/8" to the 1/4" desired, which made that side a little longer.  In addition, I had to run a drill part way into the unthreaded side of the last reducer to allow the 1/8" brass pipe fit in. 

Also, the cap that the welding tip will be threaded into is way too big to fit through all of that, so I'll have to insert that backwards into the T.  No big deal, just a note.

Questions:

1 - How do you regulate the propane PSI?

2 - I have one to use, but is a 1/4" valve really necessary?  Couldn't you just turn off the propane at the tank?

3 - I'm a ways off from needing to know this, but how the heck do you LIGHT this safely?

 

I'm sure I'll have other questions as I get futher along.  Need to buy a 1/8 NFP tap and the adapter that will go from my propane hose to the valve that I have.

 

                                          Thanks in advance,

                                                 Warner

 

Edited by Warner Smith

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The valve is mostly for security. If your flame goes off, you have to shut gas quickly! You valve should be gas rated(yellow handle)

I used a 0-40 psi gauge and 0-30 psi regulator from Amazon.

https://www.amazon.com/gp/aw/d/B06XTGXFC9/ref=mp_s_a_1_1

https://www.amazon.com/gp/aw/d/B01HIM65EM/ref=mp_s_a_1_1?ie=UTF8&qid=1505081435&sr=8-1&pi=AC_SX236_SY340_QL65&keywords=0-40+psi+propane+gauge&dpPl=1&dpID=31wh8ofHO6L&ref=plSrch

Now for the light up simply use lit paper, wood or cardboard BEFORE turning on the gas.

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On 9/10/2017 at 5:12 PM, Joël Mercier said:

The valve is mostly for security. If your flame goes off, you have to shut gas quickly! You valve should be gas rated(yellow handle)

I used a 0-40 psi gauge and 0-30 psi regulator from Amazon.

https://www.amazon.com/gp/aw/d/B06XTGXFC9/ref=mp_s_a_1_1

https://www.amazon.com/gp/aw/d/B01HIM65EM/ref=mp_s_a_1_1?ie=UTF8&qid=1505081435&sr=8-1&pi=AC_SX236_SY340_QL65&keywords=0-40+psi+propane+gauge&dpPl=1&dpID=31wh8ofHO6L&ref=plSrch

Now for the light up simply use lit paper, wood or cardboard BEFORE turning on the gas.

Thanks Joel...you've been most helpful.  I got all the pieces to put it together with the exception of the welding tip, the 1/8 NPT tap (those must be uncommon...it's not in my tap set and neither of the big box hardware stores I went to had them - I'll ask the guy in my machine shop tomorrow).  I'll also need to get a regulator and gauge....something tells me I may have some gauges somewhere...I remember getting some last year in a box lot. 

I used my angle gringer with a wire brush to get all of the paint off of the body of my propane tank, but I want to get it cut before painting it.  I suppose I should have the burner installed first, too, huh?  My concern is cutting the front off evenly and in the correct spot....and also figuring how to hinge it, also.  

For something that seems to simple, there actually are several things to figure out and do to get it all together.  I'll also have to get the super wool and refractory junk...whichever I find is the best option.  Also probably need a brick for the floor, huh?

 

                                 Thanks again for the hand-holding!

                                                       Warner

 

Here's how the burner assembly is looking right now (the 1/4" brass pipe is NOT tapped yet...the 1/8" pipe is just resting there):

 

burner 1.jpg

burner 2.jpg

burner 3.jpg

Edited by Warner Smith

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Warner,

Joel was spot on with his answer to your earlier questions. The quarter turn valve at the burner is a safety feature, but it also helps when lighting it. I use a longneck fireplace/grill lighter that allows me to keep my hand out of the way, but I'm still close enough to operate the valve and air damper. A paper ball or other such solid fuel is a great alternative. Just be sure to turn the gas on slowly so you don't blow the paper back out of the forge.

Looks like you have a reasonable assembly for the injector, even if your bushing options were less convenient. Make sure the gas injector extends past the air intake and down into the burner tube. That stabilizes the flame so it isn't as sensitive to random drafts and burns more efficiently.

Good luck and let us know how it goes,

James

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6 minutes ago, James Spurgeon said:

Warner,

Joel was spot on with his answer to your earlier questions. The quarter turn valve at the burner is a safety feature, but it also helps when lighting it. I use a longneck fireplace/grill lighter that allows me to keep my hand out of the way, but I'm still close enough to operate the valve and air damper. A paper ball or other such solid fuel is a great alternative. Just be sure to turn the gas on slowly so you don't blow the paper back out of the forge.

Looks like you have a reasonable assembly for the injector, even if your bushing options were less convenient. Make sure the gas injector extends past the air intake and down into the burner tube. That stabilizes the flame so it isn't as sensitive to random drafts and burns more efficiently.

Good luck and let us know how it goes,

James

Thanks James....and yeah, I was thinking the same thing about the injector extending past the intake...with all those damned bushings.

                                Warner

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If one were going to make this with a blower instead, what type of blower would be required?  A hair dryer?  A small box fan ducted?   I mean, how many CFM would be desired or required?   I may just build it like that from the start if it makes sense....

                         Thanks in advance,

                               Warner

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25 minutes ago, Warner Smith said:

If one were going to make this with a blower instead, what type of blower would be required?  A hair dryer?  A small box fan ducted?   I mean, how many CFM would be desired or required?   I may just build it like that from the start if it makes sense....

                         Thanks in advance,

                               Warner

For that you go to this thread:

and then toss out everything you have already because a blown burner uses none of that.  Except the straight pipe, that is.  And the valve.

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No need to toss anything...

As a blown burner just leave off the mig tip and plumb your air to the open side of the T.

Hair dryer could work, but I haven't done much with this design as a blown burner because it works so well as a venturi.

The air source info on Geoff's thread (to which Alan linked) should apply directly to this burner as long as the final burner tube is the same diameter.

James

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48 minutes ago, Alan Longmire said:

For that you go to this thread:

and then toss out everything you have already because a blown burner uses none of that.  Except the straight pipe, that is.  And the valve.

The reason I asked is because I read this part from the original author, making is sound like this setup WILL work with a blower, by plumbing the blower in place of where the damper is now:  

"No problem, to use this with a blower, omit the sheet steel damper and plumb your air source to the T fitting.

One thing to point out with this burner compared to the burners in the blown burner sticky:

This burner has a focused nozzle for the gas relative to the 1/4 inch nozzle on the other. So this burner needs higher pressures in the gas line to supply the same gas volume.

The increased pressure is essential for operation as a venturi as the velocity of gas injection determines the strength of the draft it creates through the air inlet.

As a blown burner the velocity is not critical, but pressure still needs to be higher to maintain the volume of gas.

James"

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1 minute ago, James Spurgeon said:

No need to toss anything...

As a blown burner just leave off the mig tip and plumb your air to the open side of the T.

Hair dryer could work, but I haven't done much with this design as a blown burner because it works so well as a venturi.

The air source info on Geoff's thread (to which Alan linked) should apply directly to this burner as long as the final burner tube is the same diameter.

James

You posted at EXACTLY the same time I was.  I'll try it with the venturi approach first.  Thanks James.

                                Warner

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1 minute ago, Warner Smith said:

You posted at EXACTLY the same time I was.  I'll try it with the venturi approach first.  Thanks James.

                                Warner

No problem, glad to help.

Another reason I like the Venturi is that it works even if you lose power.

James

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