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Tangental feed

richard orr


Joined: Apr 18, 2012
Posts: 18
What would happen if the burn tunnel was led into the heat riser at a tangent? Would the resulting extra spin help intensify the burn, or would it tend to cool the the burn by keeping the gasses in the tunnel longer?
R Scott


Joined: Apr 13, 2012
Posts: 2309
Location: Kansas Zone 6a
    
  28
that depends on the ratio of the sizes. It should work if the riser diameter is small enough to keep the speed up. Not sure if it will help mix any better than tumbling of a standard design.


"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
"Preach the Gospel always, and if necessary, use words." --Francis of Assisi. "Family farms work when the whole family works the farm." -- Adam Klaus
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 903
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
Been there done that.

Works a treat for a four incher.

http://www.permies.com/t/10367/stoves/Cyclone-rocket

The site which gave me the idea.

http://billpentz.com/woodworking/cyclone/index.cfm

I've made a cyclone for dust extraction.


God of procrastination (Pratchett's style) )
richard orr


Joined: Apr 18, 2012
Posts: 18
Thank you, gentlemen for your replys. Have given a lot of thought about rocket stove aplication to my steam boat since last post. None of the steam boat men, nor the steam car crowd have applied rocket stove principals to their boilers. Have posted on the S.A.C.A. forum but no one seems to consider such an application as do-able. It seems the S.A.C.A. crowd feels it is rediculous to place generating tubes outside and away from the radiant fire area. There is a person experimenting with rocket stove / steam boiler on Youtube, but his design is not really using rocket stove principals. The boiler I am designing is a mono-tube and I so value the safety principal of being able to isolate the generating tubes from the fire that I am determined to come up with a design that does so.
There are three main principals I am designing toward:
1. Ability to isolate generating tubes from the fire.
2. Clean burn.
3. Use of long, strait screw-togather generating tubes.

The third principal is the most demanding of design restraints, but the strait, screw-togather tubes allow the system to be taken apart and cleaned out periodically which is also a very high priority and the long length of the tubes allow for less elbows in the system thus cutting down on resistance.
But there is the rub. In a conventional steam boiler, the generating tubes are placed inside the fire box. They are directly exposed to the radiant heat, thus absorbing the greatest heat, but at the same time they also cool the firebox and encourage sooting. In a rocket stove, the generating tubes want to be in a pancake, coiled configuration just above the riser where-by the gasses have had time to thoroughly burn. Yet any distance beyond that point the tubes start getting further away from the primary radiant heat and more into the cooler zones of the convective gasses.
And so, with strait tubes, the heat arriving at the "sweet spot" in a conventional riser would only impinge upon a small area of the generating tubes. The solution may have to be a compromise of principals. What may be called for is a narrow, elongated riser. The generating tubes of my boiler will be six feet long and running horrizontaly. Therefore the riser, in order to have that "sweet spot" impinging on the full length of the tubes, will also have to be of the same length. This in turn indicates that the fire box will have to run horrizontally the full length of the riser so that the radiant heat will address the "sweet spot " evenly.
I invision fuelling the boiler with six foot lengths of bamboo or switch grass. In emergency situations or when on stand-by, the firebox will be isolated from the rest of the system by a damper running it's full length.
richard orr


Joined: Apr 18, 2012
Posts: 18
A brief explination:
The reason I was concidering a tangental fire box feedeing into the riser of a conventionaly configured rocket stove design is that I was trying to contrive a system that would create enough force/pressure behind the convective gasses as to deliver them the full length of the generating tubes. But then I concluded that distance away from the radiant heat source and the greater space that the gasses would have to fill before impinging upon the tubes all equated to loss of heat.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 903
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
Richard, just a quick thought.

Your tubes, if in the heat riser would have to have water permanently in them, to cool down the tubes, so they don't melt. This in turn, cooling the burn, and lowering the eficiency. Or, you could fit theses between the barrel and heat riser. Thought, would this be eficient enough at producing steam?

richard orr


Joined: Apr 18, 2012
Posts: 18
That is exactly the point; the tubes, if in the heat riser, would create an adverse effect by cooling down the gasses prematurely. That is why the tubes must be placed just above the heat riser just as if one was placing a pot to boil at the top of a rocket stove designed for cooking - the sweet spot. However, place that pot too far above the riser and it looses efficiency.
And so , it seems that there are two principals in oppisition: the closer the heat exchanger is to the radiant heat the more of the heat it will absorb, yet the closer it is the more it will mitigate that heat and thusly create a dirty burn. Most steam boat or steam car boiler designers are willing to accept a dirty burn in order to get the most heat. This in turn causes sooting of the tubes and an eventual loss of efficiency. I am designing for a BALANCE OF PRINCIPALS with the highest priority set towards safety.
A mono-tube boiler has little to no water reserve. If the feed water to the boiler some how fails there is but a few seconds to resolve the issue. Convential methods are to shut down the burner of the boiler if using liqued or gas fuel, but if using solid fuel, the proces of shut-down becomes more timely. Now, if the boiler is designed so that the generater tubes are not in the fire box, then a damper can be placed between the tubes and the fire box and shut-down can be achieved within seconds.
I believe the thing to do is place the tubes just above yet outside of the heat riser. Shorten the heat riser to just enough length to achieve a (reasonably) clean burn and thusly get the tubes as close to the heat source as possible. Then put 309 stainles mesh just at the outlet of the heat riser to achieve a secondary burn so that the tubes may recieve some radiant heat and the rest of the particulate is burned to reduce sooting of ther tubes. Place a bell over the entire tube bank so configured that the heat rises up one side of the tube bank, over the top and down through the tubes, exiting out the far side bottom of the tubes. This should capture all the heat of the combustables while allowing the cooler, non-combustable elements of the gasses to siphon out the bottom. Yes?
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 903
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
Richard, just a thing which comes to mind.

Make the barrel out of tubes welded together, may be insulated on the outside, then at the end of the barrel, you have the tubes all of them, exhausting between two thick metal plates wih a space tuned for your use, where the pre heated water would become real steam.
richard orr


Joined: Apr 18, 2012
Posts: 18

P.S. No, I think placing the generating tubes between heat riser and barrel would be too far from the original source and only produce low pressure steam at best. Think of it this way: Every extra square inch of space the gasses have to fill, the cooler the gasses get. Not enough to power a boat. The lower the pressure, the larger must be the boiler and engine. If not a larger engine then the more r.p.ms. a smaller engine would have to turn to produce a given horse power.
richard orr


Joined: Apr 18, 2012
Posts: 18
Please excuse me Satamax. Did not mean to make a post that may have sounded curt. Posted last message in reply to your earlier post and not the current suggestion which is worth thinking around. Quite interesting idea to apply to a water heater but there are inhearent problems when applying it to high preasure (above 15 pds. per sq.in.) scenarios.
I plan on running the boiler at about 80 p.s.i. and generate around 8 h.p. The top plate you invision would have to be thoroughly reinforced with stay bolts. Has been done many times before but must be done correctly to high standards. With such a configuration there are expansion issues and the boiler must be brought on and off line very slowely. This type of boiler would also require a bottom ring - not impossible but still requiring a high set of skills. Such a design approach is in the order of a natural recirculation boiler and would require either a recirculation pump or some kind of down-commer system - a much different critter then a mono-tube.
Keep in mind that the bottom part of the tubes are ,again, pretty far from the heat source and in an area probably better suited for the economiser section. Also to be considered is the fact that when gasses flow along the length of a tube they are 1/4th as effective as when they impinge upon the tubes at right angles. This impingement at the top of the riser in a rocket stove is one of it's high points and I believe a steam boiler design must be such as to take the most advantage of this area. A set of counter flow pancake coils atop the riser would work fine but the problem with that is that such tubes could not be mechanicly cleaned out and that is one of my design prioritys.
Such a design as you suggest is somewhat of the BABCOX/WILCOX design and if the top plate were removable it would be a real sweetheart to clean out.
The boiler I am going for will be of the screw-togather kind. It will allow people of an average skill set to build such. This is an approach that is looked down upon in professional circles as it is concidered a bad practice to have screw-togather joints exposed to the gasses of the boiler. However, it is no great challenge to design such as to have the joints behind a plate and completely outside the flow of gasses.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 903
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13


Ok Richard.

Well, don't worry too much bout me. It's just thoughts which come to mind when reading what you write. I have no experience with steam other than for bending wood. And reading my old engineering books. Thought Babcox/wilcox seem to stir some memories.

May be the multi tubes could be replaced by two sleeves or jackets. This would be mono tube Dut please, don't pay atention to my babling.
richard orr


Joined: Apr 18, 2012
Posts: 18
There is no babbling here - just dreams and ideas for a starting point. I think on this forum, we are all mostly dreamers and tinkerers. On the S.A.C.A. forum, they are mostly steam engineers having extensive experience with steam cars - a most challenging application. Their equations make my head swim and I am intimidated to even ask questions there. When broaching the subject of steam production with a rocket stove, I was dissmissed with much derision. Their perspective, though, is restricted to the tight design parrameters of having to solve for steam cars which means that they are interested in boilers that are tight, light, ultra responsive and run at extreemly high pressures. (800 p.s.i. and above)
 
 
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