Kristijan,
Thanks for this observation. My MGB nozzle is based on your design but is 1 inch ID straight through AND air enters from both ends (post 77). It will be interesting to see how this arrangement performs. I’m within a few hours of first fire, but I am currently in Oklahoma visiting grandbabies.
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I wanted to say but forgot to that l think you have overcome this problem with haveing air intakes from both sides.
Dont forget to document it! We have waited to see this work of art for a long time!
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Yes, the long wait has been painful for me. The next possible day to work on the MGB char-iot is August 3. On the subject of nozzles, I have some old 2 inch ID cast iron drain pipe with a wall thickness of about 3/16 inch. I hope to try it in a small gasifier someday with a slot instead of holes. The diameter is great enough to allow a crescent shaped blade to be inserted to clear clinkers.
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Hi Bruce, Kristijan,
The path off the least resistance… the air flows where the vacuum pulls,
Keep the path unrestricted unto the nozzles ( input orifice bigger then the sum of nozzle orifice’s)
In your case Kristijan, you’ll have to look further downstream in your design… remember my observation on your nozzles clogged up ?
First recommondation: enlarge your air intake to eliminate restrictive vacuum. ( other then the nozzles )
Rule of thumb Nozzles are 70% of the air intake size
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The clogging can not be an issue becouse l poke the nozzles every day now (thanks Bruce) with a poking wire.
The path of least resistance yes, but thain the closest nozzle to the airtake shuld get more air not the other way around. Allso the nozzle tube is about 10 cm dia. 40cm long so that isnt very restrictive. But the air intake is 3/4" so at high air velocitys it creates a Venturi efect. Imagine a propane burner difusor. The pressure is lower at the air intake thain the the burner tip.
Unfortunaly l can not enlarge the intake. lll try to put a restriction in to swirl the air a bit rather thain have it all rushing to the back.
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Hi Kristijan,
Based on what i have seen on your pictures and from your observations, i would suspect following happening in your system: ( my personal obeservation on your case)
after cleaning and starting, you will have all 4 nozzles working, but the first one will get clogged up, then the second and so on, due to your high temperatures,
The last nozzle will not clog so easy because of the increasing velocity after the clogging from 1, 2 and 3…
( cutting torch effect, vissible in your earliar picture.)
since your engine creates a vacuum above the nozzles and your airinlet is bigger then the 4 nozzles, its more likely to have an even divided force on all your nozzles ( same vacuum on same hole size )
Any turbelance in your nozzle pipe would be minor due to the airspeed increasing on your 4 nozzles at start up.
In my opinion, even neglectible since you have a nearly constant flow and not pulsating from a single cylinder…
anyway, its a nice phenomen to study into…
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l think that is exactly what is happening. But the fact that the last nozzle always stays clean the longest got me thinking. Like you sayd, it shuld be the opposite ( path of least resestance).
The real question now is what to do about it. l was thinking to thread the nozzles and put smaller inserts in them. This wuld increase air velocity and aid slag breaking. Maybe put a smaller nozzle on the last hole zo equalize air flow on all four.
By the way, l was playing a litle with water injection today and l got the speedometer from usual 95km/h (60mph) on plain chargas to 110km/h (70mph) with water. lnjected about 4l/100km (1,5 gal/100miles ) of water. Charcoal catching world speed record on wood. Brigt side beware 
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Copying this from my post on another string to keep this info under nozzles:
My nozzle is 4 vertical holes in thick-walled copper tube passing through the reactor and sucking air from both ends. Copper because it has been used successfully for crude iron smelting.
“A suggestion by Dr. K. Smith on the possible use of copper tuyeres historically led to some experimentation with this material. Several tuyeres were forged from differing thickness of scrap copper plate and tested at a workshop in February 2005. … During this workshop, Sauder, Williams and McCarthy worked with a tuyere forged from 1/4 inch thick (about 7 mm) plate. The forming process created a conical shape that varied in thickness from roughly 3 mm at the air supply end to about 7 mm thick at the smelter end. … The interior diameter was approximately 20 cm in the smelter. This copper tuyere proved extremely durable. the high conductivity of the copper allows it to radiate away the heat its working tip is exposed to.”
I hope to have my MG running on this nozzle by the end of August. Don’t hold your breath, I previously thought I would have it going by the end of May. I fear that there may be a good reason that we have not seen copper nozzles in gasifiers (other than war-time scarcity). Time will tell.
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Hi Bruce,
Really enjoyed reading this and it might opened my eyes for the reason why…
Thinking: Could it be that; the thermal conductivity capacity from the copper, prevents the heating from the glowing because the inside of the nozzle is fed with cooler air ?
This also can explain why some nozzles, be it ceramic or others, crack from the temperature stress between the inner and outside of the nozzle
On other “strange” observation; one of my test sets, stainles 1/2" pipe, does not “touch” the glowing carbon and seems to stay “in-affected”
Could we “assume” that, glowing carbon from the charcoal, strips away the carbon content from metals, in contact with oxygen from the incoming air, even some catalyctic processing / thermo chemical reactions between metals and the glowing carbon ?
The nozzle from my “water pump demo set” is a reducing 1" to1/2" welding piece steam pipe material, after so many hours still not corroded away…
the nozzles i use for my “farmer cooking sets” are cast grey iron nipples, 1/2", drilled and grinded to fit the purpose. waiting for the next results afters hours testing…
So many things to observe… so much still to learn… real life, not lab scale…
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My latest uses a cast iron power steering (vane pump) housing. I have not had much time to play with it yet, Only about 5 hours on two small engines( 21/2 hp Kawasaki flat head and a 3 1/2 hp Subaru /Robin (Fuji) flat head. The nozzle is vertical. I have not used any water or exuaste yet. I have only run it about 5 hours so far and have not dumped the char to inspect yet. It dose seem to pull a great deal of heat out of the bottom of the gasifire. I have plans for some insulation and a water drip. I hope toplay with it some more real soon. I have built a new DC charger from a 8 hp Briggs and Stratton flat head( smokes and drinks) and will need an overhaul eventually. It runs two 150 amp generator starters from a tow truck car starting unit. In a short run I was putting 150 - 180 amps in my battery bank till one of my home made wired together belts failed. I will need a charge controller to protect my batteries before further testing. This and my 3200 att inverter should make a nice little generator. I have a third one of these generators to couple with a 5hp OHV Tecumseh engine and 2200 watt inverter. That will be my first OHV engine. I have run 5 different flat heads on chargas so far.
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l was thinkin about that when building the nozzle for my Seat. That is the reason l went with such a big diametar abd thick wall. The thicknes allows the heat to be conducted in the lower partof the pipe and the big volune alows air to swirl inside longer, cooling it.
Bruce got it eaven better with the copper pipe sticking out of the gasifier where they can radiate in ambient air.
I allso agree on the cheramic nozzle absorvation. Cheramic is a poor heat conductor. Hot on the tip and cool on the base, it just has to crack. I used your fuse type nozzle on mi moped when l noticed that phenimenom. The water drip allso wasnt friendly to it…
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Yesterday I couldn’t start my engines on charcoal , no matter what I did , all ok on petrol though ,
so a while ago I did a blow test on all seals with air and soapy water , all good , so that only leaves one thing left , so laying the tank over on its side I opened up and took a look at the nozzle …
It was huge , I had one massive clinker build up all around the nozzle , and as soon as I tried to take the nozzle out it all just came away in my hand , including the nozzle that just crumbled away under a little pressure from my hands , I guess that’s the one bad thing about mixing refractory cement willy nilly , you have to make the mix as dry as possible and vibrate and compress it as tightly into the mould as you can .
Anyway no big deal just means that nozzle lasted around 45 days of running and only the past week and a bit on a water drip , so I still got a good enough run out of it .
I have replaced the stainless steel tube and drilled out the holes to 9mm and shall fire it up again in a little while and see how well that will last , in the mean time I have found some lovely thick walled mild steel pipe with a wall thickness of 3/4 of a inch , so I shall blank off the end and work out hole sizes once I have a better idea from running this stainless tube .
Dave
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Hi guys, I’ve been following this nozzle talk and like the idea of the slot. The nozzle in the following picture is one inch pipe made from stainless steel. It screws into the nipple inside of the Simple-fire. The slot is 3/8 inches wide and four inches long. The rod next to it is designed to be run into the nozzle and clean any ash build up while the nozzle is in use. A fluid drip also helps cool the nozzle and increase the richness of the chargas. Any ash that falls into the nozzle is cleaned out using a piece of 3/4 inch conduit. The conduit is pushed into the nozzle and the ash is scooped up by it and removed. Shown above the new nozzle is a straight stainless steel nozzle that has been used several times.
Gary in PA
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Quick update , stainless pipe is up and running , almost no noticeable difference to running on petrol at all once the water drip is on at 1 drip every 2 seconds I am getting the full 30 amps @ 24 volts from this tiny 87cc generator ,
Starting was very easy just start the fan and let a few pieces of charcoal get sucked up the pipe and then hit it with the gas gun and away it went , the water drips onto the pipe and runs towards the 9mm holes up the tube , but before it gets there its already steam and away it goes up through the holes .
Be interesting to see how your slotted pipe goes Gary , what engine do you plan on running with it ? .
Dave
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Hi Dave, I agree with letting the water (or oil) just drip into the nozzle. The heat in there will vaporize it and also help cool the nozzle, To that end, I’ve given the air inlet a 5 degree or so tip downward to make sure the fluid flows down the nozzle and not out on the ground, The nozzle I showed should run your small engine up to a 450cc, engine,
Gary in PA
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Based on Kristijan’s nozzle this 1 1/4 inch tube with .281" wall looks promising as a double inlet tuyere. The combined area of the two open ends is very close to the area of a 1" ID. $36 post paid for a 24 inch piece, more pieces saves on shipping cost.
http://www.ebay.com/itm/181188321765?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
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Hi Bruce , i guess you cant moan at that price as I am sure they will last a long long time .
The stainless tube I put back into my gasifier is still up and running ok , I have not had a chance to open up the tank and take a look inside yet , but its still making gas so that’s all that matters right now , total run time so far must be around 64 hours .
Last week I bought 3 suitcase 3.5kva inverter generators all not working from a dealer on ebay and managed to get 2 of them up and running ,and also onto charcoal gas, they are running the Power Jack battery charger on the inverter and loading 50 amps into the batteries when flat , but if I run them with no water drip the engine hunts and cannot keep up the power , soon as there is a water drip the engine smooths out and I get a constant output of power .
Dave
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Your run times are the best and your experience helps keep us all confident in this technology. I can hardly wait to see how long your’s and Gary’s SS nozzle’s last.
Besides giving two ways for heat to migrate away from the hot zone, a double ended tuyere allows water to flow out if the drip is accidentally left on. This happened to me. Hopefully I will get the MG back on the road soon and start logging some miles on my copper nozzle.
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Nozzle Report
I happened to have the gasifier apart yesterday, so I snapped a picture of the nozzle.
This is the almumina ceramic tube coated with about 1/4" of refractory cement.
It only has about 2-3 hours of run-time on it. So far, it is showing no damage.
There is a slag spur building up on one side. It seems pretty firmly attached. Since it isn’t blocking the air flow, I decided to leave it rather than risk cracking the nozzle when removing it.
This is the first time I have used this particular design. I don’t know if it is a coincidence, or something to do with a change in the chemistry, but I had some strange white slag or ash blobs building up in the nozzle area that I had not observed before.
This stuff crumbles to a fine white powder under finger pressure.
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Silica ash maybe? I have seen this also.
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