Semi-pressurizing an ESBIT stove

I'm wondering if there would be any benefit in flame pattern &/or heat output to contain ESBIT-type fuel tabs in a containter that would create some pressure and jet the flames out through say, 8 holes, each about 1/8 inch in diameter. The container would likely need some bottom air intake holes, no?

Just a thought.

Eric

Ugh. That sounds like complicating something whose main advantage is simplicity. And it's extra weight to boot. Esbit is generally the lightest way to go (not the cheapest) but more importantly it's the most straightforward. You light it and sit back. I used to be an alcohol stove guy (and they are fun) but now I find myself using Esbit more and more just because there is so little fuss factor.

That's my opinion as a backpacker. However in terms of thermodynamics then yes, there may be a small advantage to a pressurized system. Sort of like at your local power plant. Coal will just burn if you light it. But at the power plant they grind it to a powder and feed it into a swirling vortex to get the most energy out per ounce. The same principle may apply to Esbit stoves. But do you really want to go there?

I know a windscreen makes a difference for the Esbit. If I can squeeze it in with all my other unfinished projects I will attempt to build something like what you described. Sure, it complicates a simple idea but it sounds like fun. Any excuse to play with fire is OK (smile).

The problem I foresee is getting enough air into the system. Alcohol vaporizes to provide the pressure. Only vapors burn so there must be some vaporization with the Esbit. However it doesn't vaporize as readily as alcohol or liquid fuels so pressure may be difficult to achieve without forcing air into it. Maybe study how solid fuel rocket engines work for an idea?

I might be missing something in my logic.

Solid rocket engines carry both fuel and oxidizer mixed together so that they can operate in space or very high altitudes where atmospheric oxygen is missing or minimal.

There is a "hybrid" rocket engine which uses (generally) a solid fuel and a liquid oxidizer, but that has little similarity to the Esbit stove operation.

Experiment. Tinker. That is where great ideas often originate.

I understand the part about carrying solid fuel and oxidizer, and understand that fuel and oxidizer can be part of the same molecule (as in high explosives, which I know a little something about). So my question is, how does it it vaporize enough to get through the fuel lines and into a combustion chamber?

Again, I know nothing about rocket engines so may be asking an inane question.

Solid rocket motors have no pumps.... solids don't pump. It doesn't exactly vaporize like liquid hydrogen or kerosine or gasoline.

It is a crefolly formed solid, cast into a pressure vessel (the rocket body) and it has an interior ignition surface designed into the casting. So, there is some kind of a hollow extending over most or all of the length of the propellant "grain".

It is ignited with a flame and combusts in a controlled fashion by design.

There are a lot of good web pages which have nice explanatory pictures. Google "solid rocket motor design" and the figures will make it clear.

Or go to a hobby shop and buy a solid rocket motor kit, assemble it and launch it.

Coming soon: The model rocket engine solid fuel backpacking stove. The pot stand may need some work but it will heat your chow in a jiffy.

As I've said here before, I'm just waiting for modified solid rocket fuel to become the new backpacking fuel - probably with a molded-in oxidizer tablet. (NauticK military labs, are you listening? Forget capillary stoves.)

Talk about backpacking being a "blast"...

Eric

Eric
I think that the better windscreen option is the easiest way to do that.
The only one that works for me is the Caldera Cone, never had much luck with any of the other windscreen types.
Having said that I might have a go at making a "stove" for that fishy stuff.

Franco

Franco,

I'm going to get a Caldera Cone and the new wood burning adapter so I'll try ESBIT with the C.c. this winter. Been using an MSR windscreen fit closely to my pot. Works well but likely not nearly as well as a C. Cone.

Eric

I have a picture around here somewhere of a Ethiopian traveling blacksmith, brazing a bicycle together using a cow patty as fuel. He uses an over inflated bicycle innertube as a "bellows" and meters just the right amount of air to oxygenate his fuel. Having lots of innertubes around here, I tried that with esbit and alcohol stoves....yeah, they get crazy hot and burn your fuel faster. So, I suppose 'jetting' esbit would provide a more direct and hotter flame, but you'd also consume your fuel quicker and end up with a stinky/gooey mess in whatever your using as a stove. Capturing the extra heat is the tricky part.
As previously mentioned, the simplicity of Esbit is hard to beat. Light it, kick back, cook. I don't mess with alcohol anymore....it's fun to build the little stoves but Esbit is easier to use.

I never tried this as stove fuel, since rocket fuel is supposed to burn fast and hot which is not the best way to heat water. But if you can't wait for the Army researchers, making rocket fuel out of potassium nitrate and sugar is not that hard.

http://www.jamesyawn.com/skillet/large/index.html

Let me know how high you can launch your pot.

Eric
Caldera Cone Inferno
That looks like a great system. I have the Ti Tri 550ml and it works for me. I noticed Hendrik's video of the Inferno set up
http://hikinginfinland.blogspot.com/2009/09/gear-talk-trail-designs-ti-tri-inferno.html
so I made my (temporary) version with a wind screen . Works very well. The Esbit kit you get with that is the one that works for me. (but I really only use alcohol, however now I have made a gas conversion for it...)

lars
as you said - cracks in the propellant stick is not good, it creates an extra unplanned burning surface. Generally the inside of the propellant is either a star shape to increase the burning area, or solid in the event that an end burn creates enough gas. Did you know that there is a chemical "librarian" who is responsible for all of the solid rocket propellant in all of this countries solid fueled ICBM's?

Your fuel is an ancient recipe, I made similar stuff over 40 years ago, but you really have the process down - often organic chemistry is far more complex in its process than in its theory.

So - Galcite rocket fuel - used in the Polaris because of its waterproofness for underwater launch, later replaced because it creates vast plumes of steam that could identify the launch spot. Galcite is road oil and a nitrate compound.

Jim

Jim, I can't take credit for the instructions, I just linked to them. Actually,since I only make some once in a great while when demoing small rockets for kids, I prefer the oven method. And yes, molding different shapes to show how the surface area affects the burn rate is part of the experiment.

Since my original post was a somewhat offhand comment, I should probably point out that rocket fuel is about the worst thing you can use for backcountry cooking: it's designed to create a lot of hot gas during combustion. Expelling that gas through a nozzle is what propels the rocket forward, so you want loads of it. Not really something you want to do in a tent, under a tarp, or anywhere near a camp site. One other use of sugar/KNO3 is smoke bombs.

More in my upcoming book Backcountry Cooking with ANFO ;-)

You could always just skip the esbit and cook over a dried cow patty...

Actually in all seriousness, having burned them on dry range here, it's probably smell a heck of a lot better than esbit

Franco,

Weddy, weddy clever gas conversion young man. What burner did you use as a basis?

Eric

The stove is the world famous Bu Lin BL 100 b5
(160g before , but still B5)
Now it is a bit under 110g with the screw/wing nut and curtain hook wire for the stand.
As it is because of the pre-heat tube that is the minimum height that I can have it at (I am not brave enough to bend that tube) and it is the correct distance for my set up.
Franco
110g = 3.88oz
160g = 5.64 oz

BuLin
http://www.cnbulin.com/en/product.asp?class_id=31

I save my Esbit for times when there are no twigs or cow patties. That Ethiopian blacksmith made is living with it and his forced air source make the stuff hot enough to melt steel.

With enough forced air, you can basically burn any organic material at high heat. As one of my former bosses demonstrates by cutting through steel with his bacon lance.

http://www.popsci.com/bacon