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#15 Reply
Posted by
RedRyder
on 01 Nov, 2021 10:27
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Hi Maurice, You have constructed a superb boiler!
Thank you for sharing it here.
Gil
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Hi,
Well, the burner seems to work OK, it produces plenty heat, it is surely big enough.
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I have also tried Tony's idea with the plate, it gives a nice stable flame a low load, at high load it does not seem to give any improvement.
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Regards,
Maurice
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#17 Reply
Posted by
Tony Bird
on 02 Nov, 2021 03:32
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Hi Maurice,
I am wondering what the flue gas fan looks like, any video or picture on that?
I don't have a photograph of my fan but later today I will find the tool box it is in and take one.
Interesting photographs of your burner in action, you have a good flame combustion wise but the ceramic isn't producing any radiant heat, I haven't seen this happen before. The second photograph with the deflector plate which is certainly producing radiant heat shows a ring of radiation on the ceramic, strange. A thought, do we know that the ceramic that is being used radiates?
I will cogitate on it (doesn't hurt if you are sitting down) until I post the photographs of the fan.
Take care Tony.
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Hi Tony,
I have purchased this ceramic at at a model eng shop, this was the only type available.
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Regards,
Maurice.
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Hi Tony,
I checked my book on ceramic burners:
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I guess that you are using different ceramics, in my case the ceramic should not glow as it can damage the ceramics and increases the risk of blow-back.
Interesting subject though, wonder what would be the most efficient.
Regards,
Maurice
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#20 Reply
Posted by
Tony Bird
on 02 Nov, 2021 12:54
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Hi Maurice,
I have that book and hadn't noticed that the burners weren't producing radiant heat! The ceramic elements which seem to be used in the UK and supplied through model engineering companies come from portable gas heaters.
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They are designed to produce radiant heat, I and many others have used them for many years and I haven't heard of any problems with blow back and I have models maybe 30 years old that still use the ceramics they were originally fitted with. They are vulnerable if they get wet as they can fall apart. As to whether one produces more heat than the other I would not know. At least now we know why yours doesn't turn red.
As to Fan blower or maybe they should be called suckers; they are a battery powered fan that fits over the chimney. One that I use on my larger steam models:
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Or if there is an air supply available a simpler version of doing the same Job.
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They are used to create a vacuum to draw the fire until steam is raised when the blower is turned on to continue the job.
I think I would just try your burner in the boiler and see how things go, hopefully all will be well. But if the flames aren't drawn into the tubes it would be worth trying some form of suction. I is good to know your burner is performing as it should and look forward to further progress reports.
Take care.
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Hi Tony,
Thanks for the pics, I really like the fan idea.
I just did a quick test run on the boiler, couldn't hold the curiosity, it is working very well, I very pleased with the burner setup.
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The draft is very good and I got 3 bar pressure in just a few minutes.
Tommorow I will hookup my Regner long stroke engine.
Regards,
Maurice
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#22 Reply
Posted by
Tony Bird
on 03 Nov, 2021 04:04
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Hi Maurice,
A very good result, might it be an idea to try the disc you made above the burner to spread the heat to the outer tubes the radiant heat from the disc should keep the centre tubes happy. Though I suspect it will produce enough heat as it exists.
I think you might have solved the problem of the smell (poor combustion) I was having with my boilers fitted with fire tubes. Mostly I build model steam locomotives and the odd boat when these have vertical boiler they have centre flues and heat exchanger's to maximise their water capacity so that they will run for the longest possible time, though all are fitted with top-up valves if they get low on water. Because these models work out in the elements their ceramic burners are sealed into the bottom of their boilers.
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These burners have virtually no secondary air for combustion but exhaust OK because of the larger central flue. When I built the fire tube boilers I sealed the burners in as I usually did and though they worked they smelt, these burners were of a standard design which worked OK in boilers with one large flue. So I conclude that the exhaust gases don't like going up the many smaller tubes so have to be drawn out by either a blower or the exhaust from an engine just like a coal fired boiler needs. Your boiler with the fire doors open allows a lot of secondary air into the fire box which somehow aids the exhaust gases through the smaller flues? Might be worth trying your boiler with the doors closed to see if there is anything to my theory.
You might be interested in the type of heat exchangers I use in my vertical boiler, these are photographs of my part built boiler for a locomotive which is my next project.
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I am a few weeks away from finishing a 7/8" scale model of a tram engine this uses a ceramic burner under a pot boiler fitted with heat exchangers under it.
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I am also helping a friend who had an old model boat hull, a vertical boiler and a double acting single cylinder engine. The single flue boiler was meths fired and I have made a ceramic burner for it which is sealed in but has no problems working. The engine is a bit large and has a big four-blade propeller. There is a bit of pipe work to complete when it can be tested in a tank. I suspect if the propellers torque doesn't cause the model to capsize it should be quite quick.
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Take care Tony
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Hi Tony,
Some nice boilers you got there, I especially like the look of the horizontal boiler.
Interesting consept with those heat exchanger pins on the boiler plate, does this not give more resistance and turbulence in the flue gas channels ?
Optimal flue gas stream depends mainly on the density difference between the hot gas from the burner and the cold surrounding air supplied to the to the fire box.
If there is no cold air due to a closed fire box then there will be limited flue gas flow, independent from the combustion air supplied through the burner.
Excessive flue gas in the firebox will cause poor combustion of the gas.
Could the lack of cold air supply cause some of the issues you are expirencing ?
Regards,
Maurice
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#24 Reply
Posted by
Quickj
on 03 Nov, 2021 10:13
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This is a very interesting thread on Boilers and Burners. I am learning a lot.
Thanks guys
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#27 Reply
Posted by
Tony Bird
on 04 Nov, 2021 04:56
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Hi Maurice,
It looks as if if your boiler/burner combinations produces more than enough steam for your engine and excellent result. Well done!
Some nice boilers you got there, I especially like the look of the horizontal boiler.I hope in the next week or so to be able to fire the boiler for the first time, the chassis has been test on the track using a test boiler mounted on a truck and the ceramic burner is one of my well proven designs. The pot boiler has about 30 heat exchanging staple shaped pins similar to the ones to be used in the vertical boiler, again a design I have used before.
Interesting concept with those heat exchanger pins on the boiler plate, does this not give more resistance and turbulence in the flue gas channels?Yes, but the slowing down of the exhaust gases allows more heat to be absorbed by the boiler and in a centre flue boiler doesn't seem to effect the combustion and I have used a similar design before. These boilers are quite small 55 mm in diameter or less and trying to keep the water capacity as large as possible and producing enough heat can be a challenge. Some years ago I boilers with plain flues and similar boilers with different types of heat exchanging pins, there was a much larger steam production with pins that without, not easily quantifiable but the engines used to test them could be run at a much higher speed continuously using the boilers with heat exchangers.
Optimal flue gas stream depends mainly on the density difference between the hot gas from the burner and the cold surrounding air supplied to the to the fire box. If there is no cold air due to a closed fire box then there will be limited flue gas flow, independent from the combustion air supplied through the burner. Excessive flue gas in the firebox will cause poor combustion of the gas. Could the lack of cold air supply cause some of the issues you are experiencing?Yes, that is the case and was cured on my boilers by using a blower to suck the gases though the tubes. I think the difference is probably caused by the different types of heat produces by our different ceramics. It is seemingly general in the model steam locomotive world to pretty much seal the burner be they ceramic or poker into the boiler using the air mixed with the gas for combustion. In this video which I have just posted in the model boat section the holes that used to supply air to the original meths burner have been sealed when convert to a ceramic burner. The burner is lit by a flame applied to the top of the chimney and turning the gas on. The covered holes can be seen on the still photograph below
https://youtu.be/SkWwADGt9o0Take care Tony.
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