Author Topic: Gas Burner for Horiz Boiler  (Read 3524 times)

Offline simonrowley

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Gas Burner for Horiz Boiler
« on: October 12, 2016, 04:32:22 PM »
Just finalising my first boiler but I am having difficultly getting a good temperature from the gas burner. I know this has been a common subject but I cannot find anything posted that gives me an indication on what I am doing wrong.
When the Gas Jet Carrier is fixed in the Mixer Tube, as per the Sandy Campbell's design, I get a very weak flame. I increased the size of the holes in the Mixer Tube but this has not made any difference.
It is only when the jet is held 15mm completely outside the tube that I can get any kind of red glow on the ceramic, see photos. Strange that it works at all like this but suggests that I am not getting enough air mixed with the gas (Butane).
Any advice gratefully received.
« Last Edit: October 12, 2016, 04:38:32 PM by simonrowley »

Offline SandCam

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Re: Gas Burner for Horiz Boiler
« Reply #1 on: October 12, 2016, 11:41:08 PM »
Hi Simon,
Welcome to the forum, I am sure you will find a lot of helpful people and ideas here.
If you get a spare moment or two It would be nice if you could do a short introduction piece, in the appropriate section, so that everyone knows who you are and what sort of things you enjoy building... they are a very friendly lot here and I am sure you will get a warm welcome.

It is good to see you have made progress on your boiler so very well done.

Something is certainly not right with your burner though since you should be getting a flame of some 3 inches or more in length with short white centre cones surrounded by blue cones coming from the holes in the ceramic... the cones should be touching the ceramic at their base.
The flame cones should not be lifting away from the top surface of the ceramic... if they are then reduce the feed rate until they are in the correct place.

You should never have a flame forming beneath the ceramic as this can easily lead to a flashback to the gas tank.

What sort of tank are you feeding the gas from? and what sort of regulator does it have?
What size gas jet do you have fitted?

You mention you are using Butane, which may be part of the problem since it has a very much lower vapour pressure at average ambient temperatures.

Typically 6.9psi @ 50deg F
             11.6psi@ 60degF
             16.9psi@ 70 deg F

The burner is actually designed to use mixed gas (70/30 Butane/Propane) usually supplied in camping gas type canisters with a screw top. ('Colmans' is one manufacturer but there are several others).

This gas has a much higher vapour pressure...

Typically 28psi @ 50deg F
           35.8psi @ 60deg F
           44.6psi @ 70deg F

The gas pressure determines 2 things: -

1/ The amount/volume of gas per minute that can pass through the jet.

2/ The velocity of the gas inside the mixer tube.

The first determines the total available BTU capability per minute assuming a perfect burn.

The second one is most important as far as getting sufficient Primary air mixed with the gas... it is the velocity which draws this in via the 4 side holes in the mixer tube and can be adjusted for optimum by adjusting the position of the jet relative to these holes.

Typically the end of the jet should be protruding between 1/3rd to 1/2 the across the dia. of these side holes.

I suspect you are not able to achieve the necessary gas velocity to draw in the correct amount of Primary air... and pure Butane requires a larger amount of this than does the mixed gas.

Try switching to the 70/30 Butane/Propane mix and see if that helps.

The other thing to check out is that you don't have a partially blocked pipe ate the joint to the gas jet carrier.

Let us know how you get on.

Best Regards.

Sandy.
« Last Edit: October 12, 2016, 11:52:03 PM by SandCam »

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #2 on: October 14, 2016, 02:59:53 PM »
Thanks Sandy

That all makes sense. I am using a No. 8 Jet and butane gas from a camping gas bottle (the larger one, not the small canister) and a standard regulator.

As soon as I get the right canister connector, I will try with butane/propane gas.

All the best

Simon

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #3 on: October 20, 2016, 01:57:01 PM »
Hi Sandy, All

My gas canister connector and pipe finally arrived, which I duly connected to a new butane/propane canister and the burner.

There was an immediate improvement in burner heat output but still not enough to maintain a reasonable steam pressure, i.e. driving my single cylinder engine - this engine runs on just a few psi.

I then moved the jet right back almost out of the mixer tube, it was actually just sitting lose in the tube, see pictures, so must have been allowing more air to be sucked in. This improved the burner heat/steam output and did just about kept the engine running at a moderate speed (still unloaded). The boiler at this stage started to howl  which I assume was the flame sucking air through the secondary burner holes and out the chimney, see video.

As you can see from the pictures I have fitted a sleeve to the mixer tube to moderate air into the tube but it does not seem to make much difference either way.

I will keep experimenting but again any suggestions would be much appreciated.

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #4 on: October 20, 2016, 02:02:08 PM »
Photo of overall set-up.

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #5 on: October 20, 2016, 02:03:01 PM »
Photo of overall set-up.

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #6 on: October 20, 2016, 02:08:32 PM »
Video of howling boiler.

Offline simonrowley

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Re: Gas Burner for Horiz Boiler
« Reply #7 on: October 20, 2016, 02:15:29 PM »
Burner as installed.

 

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