Pulse Combustor

[Rossco]

Hey to all interested.

I am thinking of building of a pulse combustor for burning wood/rubish/anything flamable out of an old 60L LPG tank.

The fuel will be held internaly and mixing im thinking will be optimised by way of rotating the air through the dry fuel while igniting.

A good pulsating configuration is what im takling first. And am asking now for some ideas on that.

Do you think that i have the exhast stack at the top, or try to rotate the gasses back down to a base level intake/exhast?

I am intending to add a heat exchange for water once opperational, so that will be a consideration in initial confugureation too i suppose.

I will post my ideas soon as to start some thought on the concept.

Rossco

[jmhdx]

A rubbish burning jet engine would make a celebrity of you for sure, I won't dampen your spirits but surely your'e joking.
Coal dust probably, saw dust? not in my estimation, I have trouble mixing propane.

[yipster]

thats daring but not really really novel. rubbish turning and burning jet engines are proposeded by rubbish authority's couse they burn hotter, cleaner etc.

[Tom]

The Nye Brothers made a turbine that burnt wood, but I am not sure rubbish is in the PJ fuel class : o)

Tom

[Graham C. Williams]

Have a look at this.
http://www.seas.ucla.edu/combustion/pro ... ction.html

Graham.

[Rossco]

Thankyou Graham.

As for the rest of you, well, the world could still be flat!

How many of you have seen an old chip heater? This is a pulse combustor, and loosely in the form of a pulse jet (if you think about it).

I am by no means implying to produce thrust out of the thing, nor fly it for that matter.
A hot burn with efficient heat release is the only goal.

Re-ignition is a very different matter in this than a pulse jet. A swirling vortex mixing the volitile gas is thrown at red hot embers... bang, well, whoosh, and the process is re-initiated.

Any body of compresable gas will resonate if initiated by an exiting force. If the body is formed with auxilaries, flue etc., that resonate in a sympathetic manner then the magnitude will be amplified.

Im thinking now for the low frequency the "tail pipe"/flue would be coupled with a Helmholtz resonator, to shorten the overall length.
This may have some application in a pulse jet tail too!, i must do some work on such a thing. Any theorys there?

Rossco

PS keep an open mind.
It has been misserably cold here over the last few weeks, nearly gets down to 0 deg. C over night! So i plan to get one going.
What i would really like to see is one of you that actualy knows cold weather to get one built and send me a pic of the thing melting a big hole in the snow/ice! Running on old rags and the remnants of your last oil change!

[Grant]

Hi Rossco!

I say go for it!

My local tire change place has an old heater that they keep on the workshop floor. Apparently they burn oil in it, and it is a pulsating combustor.

The other thought is the "chuffas" (water heaters) used by the Australian army. They are drip fed diesel and also give of a beautiful deep humming sound when in operation. The best fun was getting a chuffa started...they would make a huge wooooosh and "blow there stack" if started incorrectly.

Ive always wanted to make a minature pulsating combuster stove for hiking. Imagine sitting in the serene silence of the bush with only the melody of pusating combustion to keep you company....yeah!

[Anthony]

Cold weather to test it? Come on, let me my very short summer hehe.

In 4 months it's gonna be snowing and in 5 months the temperature's gonna go down to -20C very often. However, I'm not gonna be your crash test dummy, I already have all the needed hardware to keep it hot hehe.

[nick67]

Heck, it was just mid-summer here a few days ago--and we had a frost warning issued. Cover them tomatoes. It's why I don't have much use for propane as a pulse jet fuel. I regularly barbeque on the deck when it's -15º C--and the barbie doesn't work nearly the same as when it's +20º C!!! Mid-January we can see -45º C--and then propane is solid! The ongoing project is to build a Reynst pot for this winter--and see if it blows continuous smoke rings in the cold, calm air--and film it! On the plus side, tonight will be the July 1 Canada Day fireworks at midnight. Not that it is really dark, then either. Just as dark as it is going to get! 20 hours of daylight and +35º C in July, 18 hours of darkness and -45º C in January. Welcome to Canada's Peace River country! Cold weather pulsejet testing area!

[Bruno Ogorelec]

Rossco, what you need is not a pulsejet layout but a Rijke tube layout. It is simpler than a pulsejet anyway. Look it up. Nothing easier than putting a heat exchanger on it. In fact, it will work better if heat is extracted (from a proper location) than without it.

[Rossco]

Bruno, yes, ive already looked into the Rijke tube burners.
BUT i think that they are too high a frequency for good heat release?
I would like to realy get the air pumping back and foward to utalize all the heat of each stroke?

I am collecting tanks and drums for the purpose now, so ill get a few layouts tested.

Am i right in saying that a Rigjke tube with a big bulge (tank) in the middle somewhere as an inline Helmholtz resonator would bring that frequency down? Would it be more that just exiting a pipe into its fundamental resonant frequency?

What i have been really trying to get into a good config in my mind is a huge rynest. Get the fire really roaring on wood and oil with the door open somewhere near the bottom, then slam the door shut. Low pressure sucks in a votex of new air, mixes with the stalled unburnt gasses and then rolles around in the hot embers? will it re-ignite? Now i can accept some critasism for this one, go for it.

Firs things first, one Rossco Rijke comming up! (marshmellows anyone?)

Rossco

[Bruno Ogorelec]

Rossco,

Reynst did a number of solid fuel burner designs, but I think they all required the fuel to be pulverized.

How about a Rijke tube with low air input to turn waste into gas and then a Reynst pot to turn gas into heat? Much opportunity for preheating incoming air etc.

[Rossco]

Bruno, i like that one indeed. Afterburner.
Or in stove terms, re-burner. Low emissions too!

Im on to it. But, where back to hard mixing and reignition problems?
Or do you propose that the Rijke directly feeds the Rynest from the bottom and provides the ignition there too? Might be possible im just not seeing the frequency couple up. I think that they may be so far out of tune it may not be improtant?

Start up is also a big problem. How to get the proccess going in the first place? After the Rijke is well going and producing fuel into the Rynest, how is the initial low pressure for intake achieved?

Think...Think...

Rossco

[Mark]

Hi Rossco!

I say go for it!

My local tire change place has an old heater that they keep on the workshop floor. Apparently they burn oil in it, and it is a pulsating combustor.

The other thought is the "chuffas" (water heaters) used by the Australian army. They are drip fed diesel and also give of a beautiful deep humming sound when in operation. The best fun was getting a chuffa started...they would make a huge wooooosh and "blow there stack" if started incorrectly.

Ive always wanted to make a minature pulsating combuster stove for hiking. Imagine sitting in the serene silence of the bush with only the melody of pusating combustion to keep you company....yeah!

Can you find a picture of one of these, I think I saw one once on eBay, it had two stacks and a round flat disk chamber at the bottom and was also drip fed? You put it into a drum of water to heat it. I think they would be a neat thing to study, the chimney effect and some howler tube action going on. The one I saw was an old military surplus item.
Mark

[Mark]

Did your heater look like this one?

http://cgi.aol.ebay.com/ws/eBayISAPI.dl ... eName=WDVW

Mark