nozzles in gasifier
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That depends on the model. Mine has one. It is located directly in the center bottom of the firebox...
Hi Wade
Best of luck in your attempts to reinvent the gasifier. The commercial designs all have some sort separately controlled primary and secondary combustion air supply, I think this is what you're getting at. The two home built boilers that I have seen (one being my own) were both built with separate air supply, but over the course of fine tuning this was eliminated. The reality is that my boiler does not have as finely controlled combustion as a commercial unit. It would be more accurately described as a close coupled secondary combustion boiler, not a gasifier. Since I light mine and keep it going full blast for a few days, I don't think the control is as important as if it were cycling on and off.
I know you're a welder and everything looks better in steel, but firebrick is a much more suitable material for the construction of a wood burner combustion chamber. Just look at old coal boilers. Their design was very sophisticated given the technology available at the time. There were Dutch ovens for firing low grade coal, wood waste, and tannery waste. They contained a long insulated secondary combustion chamber that the flames passed through before contacting the colder steel of the boiler. Complete combustion is no more complicated than the three T's, time, temperature and turbulence. A gasifier accomplishes that but you can do the same thing with a masonry heater and a lot of designs in between.
I wouldn't recommend designing your own gasifier unless you have used one already and have specific improvements you want to experiment with. Imitation is the sincerest form of flattery, find one that you can see operate and model it after that design. The garn would be my favorite to imitate, it's a rather brutish and effective way to burn wood, not the kind where changing the dimensions a millimeter here and there is going to affect the operation.
Best of luck in your attempts to reinvent the gasifier. The commercial designs all have some sort separately controlled primary and secondary combustion air supply, I think this is what you're getting at. The two home built boilers that I have seen (one being my own) were both built with separate air supply, but over the course of fine tuning this was eliminated. The reality is that my boiler does not have as finely controlled combustion as a commercial unit. It would be more accurately described as a close coupled secondary combustion boiler, not a gasifier. Since I light mine and keep it going full blast for a few days, I don't think the control is as important as if it were cycling on and off.
I know you're a welder and everything looks better in steel, but firebrick is a much more suitable material for the construction of a wood burner combustion chamber. Just look at old coal boilers. Their design was very sophisticated given the technology available at the time. There were Dutch ovens for firing low grade coal, wood waste, and tannery waste. They contained a long insulated secondary combustion chamber that the flames passed through before contacting the colder steel of the boiler. Complete combustion is no more complicated than the three T's, time, temperature and turbulence. A gasifier accomplishes that but you can do the same thing with a masonry heater and a lot of designs in between.
I wouldn't recommend designing your own gasifier unless you have used one already and have specific improvements you want to experiment with. Imitation is the sincerest form of flattery, find one that you can see operate and model it after that design. The garn would be my favorite to imitate, it's a rather brutish and effective way to burn wood, not the kind where changing the dimensions a millimeter here and there is going to affect the operation.
thanks ben you seem like a very man and i will look at the garn boiler and go from there but any help you can give me with the design i would appericate thanks ..wade
benjamin is right, check out garnification's and nofossil's brothers boilers they built using a proven model. Combustion design is not for the faint of mind or wallet,extensive testing and monitoring equiptment is necessary to prove a design's effiency. I envy your enthusiasm, good luck.
I've got nothing but admiration for anyone with the skill and gumption to consider trying to do a DIY gasifier-
that said-
I forget who made the remark on here, but I think it was well put- that a downdraft gasifier is a lot like a carburetor (only even more so, in that you're not just mixing fuel and air and sending them off to a separate combustion chamber, you're burning a solid fuel to distill the gaseous fuel (wood gas) and then combusting the wood gas in the very same spaces and processes that you're doing the distillation and mixing. So it's not just how many nozzles, or what area the nozzle has in square inches or centimeters- but a much more complex set of interacting variables about firebox volume and proportions/ shape, burn volumes of solid and gaseous fuel and velocities of fuel and air through the main nozzle. volumes and velocities of air through the secondaries, and size and shape of the secondary burn chamber and firetubes (where you want a lot of surface area and the right amount of residence time and turbulence to catch most, but not all, of the heat. I am a DIY junkie, and have a real knack for diving in over my head and then learning enough to not only figure things out but get good results and finished product-- but without some hard-core engineering abilities to go beyond seat of pants/ instincts/ empirical observation, I wouldn't want to take a flying run at making a downdraft and hoping that my first one would come anywhere near hitting any of the sweet spots of the above interacting variables. If you _do_ I think that's impressive and I am not looking to discourage you- just trying to highlight some of the parameters that you'll be working with.
I'm sure that the Garn-style is no less of a work of engineering art of nailing a bunch of the same disparate variables and getting them all to hit mutual/ overlapping sweet spots- but I think it may be easier to conceptualize and maybe take a run at emulating - plus it'd give you boiler and storage all in one vessel, while removing all of the control/ pump stuff you get into when harnessing a downdraft gasifier to storage. If I had good welding equipment and lots of experience in using it, plus necessary time and materials to play, I'd be curious to try to build sort of a "cube shaped garn" - you'd probably need to have some cross ties in the tank to make up for/ avoid the tendency of straight side walls to bow out.
If you have any mix of confidence and skill, or the personality to give it a try and know that you're doing your own R&D and may need to do some significant rework or revision - then more power to you - go forth and keep us posted- we'll all be cheering, drooling, and offering any help that we collectively can (which, given some of the horsepower 'round here in the Boiler Room (pun specifically intended), will be a lot.
Back to your original question, if someone had a front-looking cut-away of a downdraft gasifier, then that'd be worth at least a mega-word- lacking that, try to get to go look at one. I saw a Portage and Main downdraft at the NE Forest product Expo and was favorably impressed with both design and construction (it had long multi-pass firetubes with turbulators, all of which were easy to get at and clean). Or take a look at the Froling picture here- although it's actually several steps beyond the basic downdraft that many of us know (and are pretty pleased with- me included); Piker did a series of droolworthy photos of a Froling that may give you some further ideas if you are going to think about 'imitation as the sincerest form of flattery." NOTE that I am NOT condoning anything that'd involve any form of infringement of any protected intellectual property or proprietary know-how- especially if you are looking at anything other than perhaps a one-off for your own use.
http://www.woodboilers.com/product-photos.aspx?product=50
that said-
I forget who made the remark on here, but I think it was well put- that a downdraft gasifier is a lot like a carburetor (only even more so, in that you're not just mixing fuel and air and sending them off to a separate combustion chamber, you're burning a solid fuel to distill the gaseous fuel (wood gas) and then combusting the wood gas in the very same spaces and processes that you're doing the distillation and mixing. So it's not just how many nozzles, or what area the nozzle has in square inches or centimeters- but a much more complex set of interacting variables about firebox volume and proportions/ shape, burn volumes of solid and gaseous fuel and velocities of fuel and air through the main nozzle. volumes and velocities of air through the secondaries, and size and shape of the secondary burn chamber and firetubes (where you want a lot of surface area and the right amount of residence time and turbulence to catch most, but not all, of the heat. I am a DIY junkie, and have a real knack for diving in over my head and then learning enough to not only figure things out but get good results and finished product-- but without some hard-core engineering abilities to go beyond seat of pants/ instincts/ empirical observation, I wouldn't want to take a flying run at making a downdraft and hoping that my first one would come anywhere near hitting any of the sweet spots of the above interacting variables. If you _do_ I think that's impressive and I am not looking to discourage you- just trying to highlight some of the parameters that you'll be working with.
I'm sure that the Garn-style is no less of a work of engineering art of nailing a bunch of the same disparate variables and getting them all to hit mutual/ overlapping sweet spots- but I think it may be easier to conceptualize and maybe take a run at emulating - plus it'd give you boiler and storage all in one vessel, while removing all of the control/ pump stuff you get into when harnessing a downdraft gasifier to storage. If I had good welding equipment and lots of experience in using it, plus necessary time and materials to play, I'd be curious to try to build sort of a "cube shaped garn" - you'd probably need to have some cross ties in the tank to make up for/ avoid the tendency of straight side walls to bow out.
If you have any mix of confidence and skill, or the personality to give it a try and know that you're doing your own R&D and may need to do some significant rework or revision - then more power to you - go forth and keep us posted- we'll all be cheering, drooling, and offering any help that we collectively can (which, given some of the horsepower 'round here in the Boiler Room (pun specifically intended), will be a lot.
Back to your original question, if someone had a front-looking cut-away of a downdraft gasifier, then that'd be worth at least a mega-word- lacking that, try to get to go look at one. I saw a Portage and Main downdraft at the NE Forest product Expo and was favorably impressed with both design and construction (it had long multi-pass firetubes with turbulators, all of which were easy to get at and clean). Or take a look at the Froling picture here- although it's actually several steps beyond the basic downdraft that many of us know (and are pretty pleased with- me included); Piker did a series of droolworthy photos of a Froling that may give you some further ideas if you are going to think about 'imitation as the sincerest form of flattery." NOTE that I am NOT condoning anything that'd involve any form of infringement of any protected intellectual property or proprietary know-how- especially if you are looking at anything other than perhaps a one-off for your own use.
http://www.woodboilers.com/product-photos.aspx?product=50
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