[TheForge] Burner types was Fixing my forge

[Jerry Frost]

You bet. <grin>

What we use for naturally aspirated burners are 
induction devices in the commercial world. They operate 
based on bernoulli's pinciples rather than Venturi's. 
Basically a jet of high velocity gas, liquid or mist 
will draw another gas, mist or liquid along with it. 
Placed in a confined space of the right shape and it 
will induce quite a bit of movement from the ambient 
atmosphere.

There are two (of many) types of devices that will 
induce ambient air in a burnable ratio; these are the 
only two that are useful for forge burners.

The first type is known as a "linear" inducer. The jet 
and air intake are inline with the tube; you can look 
into the end and see right through it if there isn't a 
choke, etc. blocking the intake end. Examples of linear 
inducers are the: Bunsen burner, Aussie, Reil, etc.

The other applicable type is the "Jet Ejector". The jet 
and air intakes are at 90* to each other; looking up 
the tube you'll see th end of the jet but the air 
intakes will be in the sides so you can't see through 
it. Examples of "Jet Ejectors: are the: Fisher burner, 
Porter, Rex, Side Arm, and "T" jet.

A commercial linear inducer using gas on air has a max 
induction rate of around 19:1. (the ratios of induction 
are different if you use a liquid to induce a gas or 
visa versa, there is an entire industry devoted to 
designing these things for specific applications.) A 
neutral ratio of air to propane is 17.5:1. So you can 
see you have to make your linear burner to a pretty 
high degree of accuracy to produce a neutral flame. 
There are a number of tricks to adjust the ratio so 
don't worry, they will work just fine.

A comercial Jet Ejector using gas on air has a max 
induction rate of around 29:1 (I'll fess up, I don't 
know if "Jet Ejector" is the correct term for this type 
burner. I use it because it's the term used in the 
information I was given some 15 years ago) As you can 
see using an inducer with a max rate of 29:1 means you 
have a lot of tolerence to play with; in other words 
you can fall far short of ideal and still have a good 
neutral flame in you furnace.

I have ZERO idea of why a jet ejector is nearly 50% 
more efficient than a linear. I've never even tried to 
find out. While I'd be intereted in knowing, it really 
isn't important, I use the things and they work dandy.

Of the many Jet ejector type burners only a couple are 
as difficult to fab up as a basic linear inducer. A 
case in point is the "T" jet I built. To build it you 
need to accurately drill and tap a hole in the top of a 
"T" fitting so the jet will be aligned straight down 
the burner tube.

During the summer of 98' Robert Grauman was visiting 
Alaska and spent a few days with us. We were in the 
midst of building the house and I had almost all my 
smithing gear packed away. Being a caster Robert has as 
much or more interest in burner design as I do so we 
spent many delightful hours talking about HOT fires and 
glowy metal. It seemed Robert understood exactly what I 
was describing so I didn't dig out my "T" jet burner to 
show him nor did I make a sketch. A few months later I 
got an E-mail from him with a few pics of his burner in 
operation.

I almost sent a reply saying he'd screwed up because he 
hadn't built what I'd described. He'd built the Side 
Arm. Fortunately I came to my senses and didn't say 
something so dumb. He did send pictures of his burner 
in operation, including the bronze pouring merrily into 
the mold. <grin> Later on I confessed my near stupid 
statement to Robert and he told me he understood 
exactly what I was talking about but it seemed more 
trouble than necessary and experimented with turning 
the "T" 90*.

The Side Arm is a lot easier to build than the "T" jet 
unless you have a lathe. The only drawback (and it's 
slight) to the Side Arm is tuning it. The air intake is 
all on one side so you have to aim the jet slightly 
into the intake stream to keep everything flowing 
straight down the center of the tube.

When I get my shop finished I'll start experimenting 
with burners again, the "T" I'm using is at lest 15 
years old now and I think I can do better. <grin> The 
next real change I'm making is to use a "Cross" rather 
than a "T" so a person doesn't need a lathe or jig and 
drill press or a really GOOD eye with a drill to align 
the jet properly. A write up of the "T" jet burner will 
be appearing in an upcoming issue of the Hammer's Blow; 
unless Brian comes to his senses in time. <grin>

There are any number of configurations for a jet 
ejector, Mikey's being one of the best of the home made 
ones out there. The basis of his design is a straight 
tube with longitudinal slots cut in the back. (The end 
with the flame coming out being the front for the 
puposes of discussion) His gas jet can be mounted in 
any number of simple ways as long as it's aligned 
straight down the center of the tube.

Anyway, there are a lot of options; some simple to 
build and harder to tune, some harder to build but 
simpler to tune and some in between. Hopefully I didn't 
completely muddy the waters for you but if so, I'll be 
more than happy to toss a little more clay in the 
waters. <grin>

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Geoff" <gjn111 at gmail.com>


> Hi I am normally a lurker but I realised from this 
> that I have no idea what you wrote here. Jerry can 
> you please explain in a bit more detail what the 
> major differences are between the two types of 
> burners that you describe. And can you please help me 
> understand how the efficiency differs.
>
> Thank you in advance
>
> Geoff
>