Smokebox draft blower ring
- cyberbadger
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Smokebox draft blower ring
I asked my buddy to make a blower draft ring for the smokebox/smokehood on my new VFT and he came back with this.
We are curious to see if these hacksaw made orifices work decently as drilled holes. I think it should work, I'll see how well. I just wanted something to turn on the draft for 10's of seconds after adding new fuel to get things burnering well (as needed basis).
Any thoughts?
-CB
We are curious to see if these hacksaw made orifices work decently as drilled holes. I think it should work, I'll see how well. I just wanted something to turn on the draft for 10's of seconds after adding new fuel to get things burnering well (as needed basis).
Any thoughts?
-CB
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Re: Smokebox draft blower ring
It'll probably use quite a lot more steam than necessary. Small holes also would direct the flow (correctly, as a cone converging inside the first few inches of the flue.) better. Will it work? More than likely, almost anything that forces things up the flue seems to.
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- Lopez Mike
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Re: Smokebox draft blower ring
I have a single 1/16" (1.5mm) hole directed up the stack and about the only improvement I have planned is to make a more sophisticated hole.
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
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Re: Smokebox draft blower ring
Just a small word of warning, I suggest you do not make a ring blower in mild steel piping. My boiler had one with it when I bought it and of course it rusted inside. As a blower it worked very well but as I could not hear it, I tended to leave it on until the safeties lifted! The internal rust is well nigh impossible to remove and however well you poke it back in, it always comes back up to block the hole. I changed to a simple pipe with small hole directed up the stack. As an addition, I added pressure gauge in the blower line as an indication of how much "blow" I have. The boiler is 3 ft dis by 3 ft hight VFT - coal fired.
- cyberbadger
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Re: Smokebox draft blower ring
I'm pretty happy with the result. I don't intend leaving it on for long periods (more then a few minutes). My buddy may want to try some other designs, I told him to go for it.
-CB
-CB
- cyberbadger
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Re: Smokebox draft blower ring
Spark show! Pictures in the video.
New nozzel made from a swagelok cap fitting drillbit and center drill.
It's a delavan nozzel. Way better then the ring and uses less steam to achieve a lot more.
-CB
New nozzel made from a swagelok cap fitting drillbit and center drill.
It's a delavan nozzel. Way better then the ring and uses less steam to achieve a lot more.
-CB
- Lopez Mike
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Re: Smokebox draft blower ring
What sized drill and did you taper the hole with the center drill on both sides?
If you think you are too small to make a difference, try sleeping with a mosquito.
Dalai Lama
Dalai Lama
- cyberbadger
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Re: Smokebox draft blower ring
My buddy steve:
Because Steve has been getting a little silly with the blower I added this to the valve this morning:
-CB
Sir, I have a result for characterizing the swagelok blower.
I did a worst case simulation with 200 PSI @ 350 degrees. All the internal dimensions are correct or very close to correct. The external dimensions don’t matter. I got velocities of ~20000 in/sec which is roughly mach 1.5 (1135 MPH) at the choke point. The free stream velocity os more like 400 mph. Which is what we are looking for to be high.
The jumble of flow you see up top is recirculation. I can only analyse this as a closed volume so it wants to suck on itself. So what you see there is the venturi effect causing vacuum which is drawing in the flow from the stream (it’s a good thing and its showing that its working.) I will run some more iterations and see if I can get a better nozzle with the tools we have at hand. This one is easy since I know what the nozzle is seeing in terms of feed. I will drop down the pressure to a realm where we would expect to use it like 100psi.
My buddy Steve again:Lopez Mike wrote:What sized drill and did you taper the hole with the center drill on both sides?
Steve has at least one more iteration of blower planned, even though I like this one.The swaged draft blower is a #18 drill .169” with a 60 degree taper center drill used to set the taper. Much too wide of a taper but better than a straight hole and the best we can do with the tools at hand.
Because Steve has been getting a little silly with the blower I added this to the valve this morning:
-CB
- fredrosse
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Re: Smokebox draft blower ring
"I got velocities of ~20000 in/sec which is roughly mach 1.5 (1135 MPH) at the choke point. "
Very commendable that Steve has access to CFD (Computational Fluid Dynamics) modeling, however I question the statement that Mach 1.5 is attained. With small orifices operating on steam, anything exceeding Mach 1 is just not reality. I do not know what software he is using, and most probably the software treats the steam as an ideal gas. Here at my employer we have seen CFD simulations of steam flow phenomenon that were typically far from truth. An analyst conducting compressible flow evaluations with steam, with its significant deviations from ideal gas properties near saturation (typical of our steam launch conditions) would need to add an order of magnitude extra complexity to get accurate results.
The results presented do give realistic, (although optimistic) outcomes as far as using a gas jet to produce boosted flow in the stack. Mixing and momentum transfer fundamentally make stack eductors work.
The only US Patent I have is for a power plant implosion protection device which provides reverse flow pumping when a large boiler (typically about 80 ft x 80 ft furnace plan area, several hundred feet high) experiences a fuel cutoff, and the fans sucking out the flue gas would collapse the furnace walls, which can only withstand several inches of vacuum. Unless rapid corrective action is taken, the furnace waterwalls, or flue gas ducts of the system, would collapse. This patent uses a transient gas jet system (fundamentally identical to stack blowers that have been used for over 200 years) to counter the destructive effect of the fans.
Very commendable that Steve has access to CFD (Computational Fluid Dynamics) modeling, however I question the statement that Mach 1.5 is attained. With small orifices operating on steam, anything exceeding Mach 1 is just not reality. I do not know what software he is using, and most probably the software treats the steam as an ideal gas. Here at my employer we have seen CFD simulations of steam flow phenomenon that were typically far from truth. An analyst conducting compressible flow evaluations with steam, with its significant deviations from ideal gas properties near saturation (typical of our steam launch conditions) would need to add an order of magnitude extra complexity to get accurate results.
The results presented do give realistic, (although optimistic) outcomes as far as using a gas jet to produce boosted flow in the stack. Mixing and momentum transfer fundamentally make stack eductors work.
The only US Patent I have is for a power plant implosion protection device which provides reverse flow pumping when a large boiler (typically about 80 ft x 80 ft furnace plan area, several hundred feet high) experiences a fuel cutoff, and the fans sucking out the flue gas would collapse the furnace walls, which can only withstand several inches of vacuum. Unless rapid corrective action is taken, the furnace waterwalls, or flue gas ducts of the system, would collapse. This patent uses a transient gas jet system (fundamentally identical to stack blowers that have been used for over 200 years) to counter the destructive effect of the fans.
- cyberbadger
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Re: Smokebox draft blower ring
The way he explained it to me is that it would only happen at the choke point and the velocity would dissipate quickly within say 1/4", given ideal conditions.fredrosse wrote:Very commendable that Steve has access to CFD (Computational Fluid Dynamics) modeling, however I question the statement that Mach 1.5 is attained.
-CB