Stuart boiler HB4 with noisy ceramic burner.

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Mechanicboy

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Hi folks!

When i lit the ceramic burner it burn a nice red glowing ceramic and burn silent. When the burner are in the furnace, there is problem where noise came from burner after some minutes silent burning. There is hot exhaust from chimney with silent burning, after some minutes suddenly it came noise from burner and a bit smoke from chimney + weak hot. Is it common problem in Stuart boiler HB4 with ceramic burner without secondar air?

The jet is number 8 who followed with the set of boiler/burner.
 

Rudy

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Mecanicboy
I recognize this phenomena from my propane terrace heater. After a while it started to make noise like a ram jet, but still burning behind the ceramic element. This was caused by false air leaking in behind the ceramic element, making the mixture wrong. This leads me to believe when you put the burner into the furnace the mixture becomes to rich because of less surrounding air. I would try to open up the holes where the air enters the burner just in front of the jet. If i'm wrong, try to make them smaller.
Another thing maybe worth trying, lift the furnace a few mm from the base so there will be moe air flow to the burner.
I'm actually in the process of making a boiler my selves and have bought some of that ceramic stuff to make a burner, so i'm right behind you!
Rudy
 

Mechanicboy

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Thanks you for reply.. I has created the burner who are noiseless. :) Works very well. The burner is Primus 2,6 kiloWatt camping burner.
IMG_20200214_173347.jpg
IMG_20200214_173426.jpg
 
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Steve_n

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Hi folks!

When i lit the ceramic burner it burn a nice red glowing ceramic and burn silent. When the burner are in the furnace, there is problem where noise came from burner after some minutes silent burning. There is hot exhaust from chimney with silent burning, after some minutes suddenly it came noise from burner and a bit smoke from chimney + weak hot. Is it common problem in Stuart boiler HB4 with ceramic burner without secondar air?

The jet is number 8 who followed with the set of boiler/burner.
 

Steve_n

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It should be a blue color. Move your jet in or out of the tube to adjust the air mixture. (Loosen screw and slide the jet-tube assembly)
 

Mechanicboy

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It should be a blue color. Move your jet in or out of the tube to adjust the air mixture. (Loosen screw and slide the jet-tube assembly)
I has received e-mail from Stuart steam:

If the burner is working correctly you should hear a gentle roar from the boiler, you can get various noises depending on how the jet is set up.
Here's how to get the correct burner set up.
Place the burner in the boiler, Start with the jet holder fully pushed into burner, turn the gas on fully and light the gas at the chimney, you should get a flame out of the chimney, then slowly lift the jet holder up from its bottom position in very small increments, fractions of a millimetre at a time, it will get to a point where the flame will disappear inside the chimney and you will hear a slight roar from the boiler, It can be quite quiet so don’t think the flame has got out, by carefully placing your hand above the chimney, without burning yourself you will be able to feel the heat still rising from the chimney, This will be just about the optimum position for the burner, If you go to far you will hear a war war sound, at this point if you push the jet holder down very slightly again this will be the right place for the burner. As the pressure in the gas cylinder decreases you may need to adjust the jet further.

But in fact i can't like the noise from burner due it's so awful to hear. Impossible to see flame while the burner is mounted on boiler since there is not secondary air in the burner. I designed own burner who are noiseless :)
 

Rudy

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Is it the Primus burner you referring to ar the noiseless burner Mechanicboy?
In my case I'm just about finished with my Stuart 10V steam plant and the only thing missing is actually the burner, and it shall be a quiet one indeed.
I'm currently planing to make an adjustable spirit burner. I have a "Stuart 504 style" horisontal boiler, so a Primus circular burner is maybe not all that suitable.
Rudy
 

Rudy

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Thanks Jens Erik. I have actually thought of using a gas burner and already bought a ceramic terrace heater to get hold on the ceramic, so I'll give it a shot and try making one. I absolutely like the idea of using gas. Clean and simple. If I fail I can always buy one or make that spirit burner.
Rudy
 

master53yoda

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my background is combustion. It sounds like the gas is no longer burning on the face of the ceramic, infrared or ceramic burners are designed for secondary air they do not draw enough primary for complete combustion, once you have burned up the secondary air in the firebox the flame will lift off the burner and the whole fire box to the exit of the chimney becomes a primary air only combustion chamber this is the sound change.

It could also be that the primary combustion mixture has slowed down through the ceramic burner enough that the flame has gotten behind the burner, this could be due to back pressure in the firebox.

The other possibility is a broken ceramic, it would not repeat but go to a noisy burner to start with.

i hope this helps

Art B
 
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Mechanicboy

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The other possibility is a broken ceramic, it would not repeat but go to a noisy burner to start with.

Art B
The burner is new when i bought the boiler. No broken or craks in the ceramic burner. It burn very well with red glowing ceramic.
When the ceramic burner is mounted on the boiler, then the burner noises. Adjusting the nozzle from least to max does not counteract noise.

I has the other boiler with ceramic burner mounted on the boiler, there is no noise since there is secondary air in the burner.
 

master53yoda

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if the flame gets behind the ceramic it makes a similar to a pulse noise. if it is caused by the lack of secondary air it will make a more roaring sound. also the lack of secondary air could actually cause the flame to exit the chimney, it depends on how little primary air there is. on big boilers you set what is called a neutral pressure point in the exhaust to prevent a pressure build up in the fire box. the firebox pressure if not neutral can slow down the fuel flow through the ceramic and allow the flame to get behind the ceramic.

Art b
 

master53yoda

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i took a good look at the pictures of the burner that burner has secondary air holes around the burner, it also isn't really a ceramic burner like the one in the video from David Shealey.
You might try firing it up and when the sound changes pull the burner assembly out of the boiler far enough to see the burner, if the sound changes back as soon as the burner starts drawing air around the burner it pretty well verifies the insufficient secondary air, if the flame comes back around the burner that would suggest a pressurized fire box.

Art B
 

Steamchick

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All,
There are a couple of odd remarks here that I want to "challenge" - as it seems the way to the truth is not by Engineering, but by debate:
In my experience, (looking at commercially-made Gas fires, space heaters, Kebab grills, etc.) the ceramic burner is used by the Mass Production Market as an Infra-red emitter to heat objects (people, food, Industrial processes, etc.), therefore is designed to work as a Red to Orange glowing surface, heated by sufficient Gas and Air (all from the intake pipe) in the correct mixture (stoichiometric) so that the temperature is not too high (to cause NOx formation), nor "Incomplete" (to allow free issue of CO in the exhaust) from having cold secondary air, cold surface (not red) or too much gas so the CO forms a cloud over the burner. Therefore (as an old and crusty engineer) I think someone is missing the point to say that the "surface should not glow red", or to suggest that the burners "only work with adequate secondary air".
My reaction is that Kebab shops in the high street have glowing red burners - and the chefs are NOT interested in Engineering or popular opinion, just do as the cooker manufacturers recommend. The manufacturers of gas appliances must "by law" make appliances that do not release CO or NOx into the atmosphere where people exist. (e.g. Living rooms, kitchens, Kebab shops, factories, etc. ).
Also, while the burners are designed for a specific heat output in certain controlled conditions, to use them with excess gas is not what they were designed to do. If you need secondary air in your application, then the ceramic burner is being supplied with TOO MUCH GAS, and the resulting exhaust will be full of CO - which incidentally will poison anyone breathing it. (See the "blue" flame in my attached picture). But, like tobacco smoking, some people will ignore health warnings and deliberately choose to do harmful things for other altruistic reasons...
I have made ceramic burners, and learnt that making the air inlet larger than "others" do (including some companies) allows the combustion only on the surface of the ceramic - and I get long life and clean exhaust. The attached pictures show a "mock-up" of a burner with both an 8mm dia and 10mm dia air intake and using the same gas supply, jet, etc.. (gas diffuser still needs some tuning). Guess which I think is correct?
P4042376.JPG
P4042378.JPG


Still, most coal-fired locomotives were built "for Power" - not Economy, nor Clean exhausts. That is the objective of a different group of engineers, e.g. the ship builders and power-station builders. To them, any un-burnt gas in the exhaust is wasted and expensive. - The same applies today for Car makers and Truck builders as well. Of course, "engineering" is solving the problems to the optimum compromise - to suit the customer, who is often not an engineer.
Finally, as the whole system, from air and gas intakes through to the end of the chimney, is a (complex) tube, with gas at a certain pressure, excited by the white noise from the gas jet (or other source), the "musical instrument" will "sing" at its natural resonant frequency. Mostly, this singing is too low or too high a note that we cannot hear it, but I made one application where the "singing" sounded like an air-horn! I could change the note by adding a length of tube to the chimney, but eliminated the noise by finding a tiny particle of dust that caused a "buzz" at the surface of the ceramic. Changing the gas-air mixture did not affect the noise. I also managed to damp the noise by a flexible shroud over the air intake, but that wasn't the true solution. I had managed at one point to tune the noise to a high frequency so I could barely hear it - but the solution is "cleanliness, is next to godliness". Cleaning the burner at the single hole where the noise was triggered did get rid of the noise. Any pulsation observed at the burner must be resolved, and it may not be the gas-air mixture that is wrong, just a rogue (hot?) particle, or some other fault, to distort the gas flow through the burner.
Happy firing: and believe that "none of us are perfect", but engineers try to make things that are.... by design, not by chance!
 

Steamchick

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my background is combustion. It sounds like the gas is no longer burning on the face of the ceramic, infrared or ceramic burners are designed for secondary air they do not draw enough primary for complete combustion, once you have burned up the secondary air in the firebox the flame will lift off the burner and the whole fire box to the exit of the chimney becomes a primary air only combustion chamber this is the sound change.

It could also be that the primary combustion mixture has slowed down through the ceramic burner enough that the flame has gotten behind the burner, this could be due to back pressure in the firebox.

The other possibility is a broken ceramic, it would not repeat but go to a noisy burner to start with.

i hope this helps

Art B
Thanks Art, a very interesting comment. As a principle, I try and design and make my boilers and burners effectively "air-tight" - I.E. No secondary air. I do this by making the air-intake adequate for the jet and gas required, so I get at least a stoichiometric combustion - with no excess CO that needs secondary air. Surely this is the "commercial" method - by design - to prevent heating excess air unnecessarily, and hence wasting heat? I do get a very flat flame on my ceramic burners - so they glow a reasonably bright Orange - but I try to avoid Yellow spot or white, as in my experience the ceramic will not withstand that heat stress and crack or fail. (I made one burner and had almost all the surface nearly White - like a lime-light! - It broke upon cooling).
With non-ceramic (Simple flame) burners, I find that they can be fuelled more with the entrainment (back-pressure?) inside a firebox than in open air. As an amateur - My experience is with Infernal combustion engines - I suspect that the slightly increased pressure causes an equivalent increase of flame temperature, and Flame propagation speed, but the increase of back-pressure also causes the flame to sit-down on the burner by slowing the gas egress from the burner holes. Providing the burner pressure does not cause excess velocity of gas beyond the flame propagation speed the flame will not lift-off the burner holes. But if the burner is over-fuelled to the point where the internal pressure of gas-air mixture exceeds the flame propagation speed then the flame must lift-off the burner holes. However, I suspect there is an initial condition of "partial" lift-off, or lift-off such that there is a pressure oscillation at the exit of the burner holes, thus causing and oscillating pressure wave that will naturally resonate in the following arrangement of tubes. Any wind instrument player can explain that they "just make the oscillations", but the fingering on the holes of the instrument, of valves and extra pipework, cause the natural frequency of the instrument to determine the note of the "exhaust". This resonance is also called the "natural frequency" - because it is a natural consequence of the geometry of "pipework" and pressure when stimulated by any oscillation. When we make systems of chambers at various pressures, all interconnected, of course we are making "musical instruments with natural frequencies" in the process. We simply need to avoid the oscillation of pressure that will cause the instrument to "sound".
Returning to your explanation, I suspect that the simple answer is that the addition or cut-off of secondary air simply changes the pressure beyond the burner and the flame propagation speed to enable the flame to sit-down on the burner and not create the oscillation of lift-off. Either slightly increasing the burner hole size, increased air through the burner to increase the flame propagation speed (by modifying the air-intake, mixer-tube, and diffuser?), changing the pressure within the burner body (by changing the gas intake and diffuser cross-sections or geometry, or by changing the back-pressure in the firebox (by addition of secondary air) will all change the conditions of gas velocity at the burner and flame propagation speed to not reach the "lift-off" point and therefore achieve a "quieter" burner. This may sound complicated, but it is what we engineers do, isn't it? I am not an expert on combustion, but with your experience, perhaps you can "correct my errors-of-innocence" - I'd love to learn more about what is happening here.
 

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Steamchick

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I found this interesting, though difficult to understand all the Maths!
It is quite a big (free) download. It does contain some "Simple" rules: - E.G. The Mixer CSA needs to be >250 times the jet CSA (I Think?), and the diffuser/burner CSA needs to be >4 x the Mixer CSA. Check out your burners and see if they follow these rules? They do work for me, but a larger sample of results may give us all more clues on the right "Engineering" solutions.
Thanks.
 

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