Post by tortue1958 on Mar 6, 2015 0:00:57 GMT -8
After spending the past 4 months frustrated by one smokey failure after another, I finally managed to produce a 3" rocket stove pellet heater that scares the bejesus out of me. I've seen 825 degrees on the top of this thing.
This thing has so much power, I have to choke the intake down (P channel air at 1.5 sq/in and primary air of .75 sq/in) to keep the stove top below 600 degrees. I'll get some pics going soon, but suffice it to say, this thing is frikken launchable, but still controllable.
Instead of a firebrick or a dual insulated pipe stack, I used 1" ceramic fiber blanket (2300 degree), cut to length and diameter and held together by 1/4" hardware cloth. Super refractive qualities.
I got it from a local pottery supplier here in Seattle.
It's shown no sign of degradation in over 75 cycles.
It weighs very almost nothing and is easily replaceable, and this stuff apparently lasts forever in kiln installations.
Took me about 20 minutes to cut it out, roll it up in hardware cloth and tie it up with SS wire.
I cast the body from perlite and refractory cement. I rounded the inside edges with a wood rasp to quite that obnoxious rocketyness. It still rockets and chuffs now and again with fuel dumps, but the smooth corners have provided for an a nice quite laminar flow 95% of the time. All in all, the body looks like a cinder block, but don't get stuck on that image).
I'm a welder/fabricator and decided to build my own box-like enclosure. The unit is 24" tall, 12" wide and 16" deep. I'm using a 4" exhaust and found that the heat can be scavenged by a short run (10') of flexible dryer vent. I have a feeling that a 6", 8" or even a 10" exhaust wouldn't change a thing, as long as the the exhaust can handle the thermal expansion within the enclosure.
Like most of you, I've stumbled upon a few simple foolproof methods for obtaining a quick, hot, clean and efficient burn.
There seems to be a lot of grate and basket designs for burning pellets.
I tried both and I went with a tapered basket, slanted 30 degrees inward toward the burn tunnel, two inches of exposed pellets and made from SS 1/8" rod. It transfers heat really well and hasn't clogged (yet).
It's also important to have lots of air through the P-channel. At least 1/2 if not 3/4 of the pre-fuel air quantity (after warm-up), at least in this stove.
I have a long stainless ashtray under the basket with a forward slanted deflector plate positioned in the middle of it. The deflector plate leaves a 1/4" gap just under the basket apex, and forces the primary air through the lower basket, creating a super-heated zone that turns the lowest pellets almost white. By moving the ashtray/deflector upwind or downwind of the basket, I can control where the flames occur. If I slide it more than 1/2" past the basket, the surface temp goes way up as the burning happens higher in the stack. This is how I've seen the 800+ readings.
I've been heating a 360 sq/ft shop for a month now. I burn about 5 cups/hour to start (air temp 60 deg/typical). I can get this thing smokeless in less than 2 minutes and up to temp (550), from cold, in about 12 minutes. I get my non-insulated shop to around 70 degrees before I dampen it down to 4 cups/hr. Takes about 45 minutes.
I'm working toward 2" and 3", all stainless, heavily finned/multi bell, gravity fed pellet heaters for sailboats/small spaces.
I'll get some pics to y'all once I've cleaned up my prototyping a bit. Don't wanna embarrass myself too much...
BTW Anyone use 410 stainless?
Jon
This thing has so much power, I have to choke the intake down (P channel air at 1.5 sq/in and primary air of .75 sq/in) to keep the stove top below 600 degrees. I'll get some pics going soon, but suffice it to say, this thing is frikken launchable, but still controllable.
Instead of a firebrick or a dual insulated pipe stack, I used 1" ceramic fiber blanket (2300 degree), cut to length and diameter and held together by 1/4" hardware cloth. Super refractive qualities.
I got it from a local pottery supplier here in Seattle.
It's shown no sign of degradation in over 75 cycles.
It weighs very almost nothing and is easily replaceable, and this stuff apparently lasts forever in kiln installations.
Took me about 20 minutes to cut it out, roll it up in hardware cloth and tie it up with SS wire.
I cast the body from perlite and refractory cement. I rounded the inside edges with a wood rasp to quite that obnoxious rocketyness. It still rockets and chuffs now and again with fuel dumps, but the smooth corners have provided for an a nice quite laminar flow 95% of the time. All in all, the body looks like a cinder block, but don't get stuck on that image).
I'm a welder/fabricator and decided to build my own box-like enclosure. The unit is 24" tall, 12" wide and 16" deep. I'm using a 4" exhaust and found that the heat can be scavenged by a short run (10') of flexible dryer vent. I have a feeling that a 6", 8" or even a 10" exhaust wouldn't change a thing, as long as the the exhaust can handle the thermal expansion within the enclosure.
Like most of you, I've stumbled upon a few simple foolproof methods for obtaining a quick, hot, clean and efficient burn.
There seems to be a lot of grate and basket designs for burning pellets.
I tried both and I went with a tapered basket, slanted 30 degrees inward toward the burn tunnel, two inches of exposed pellets and made from SS 1/8" rod. It transfers heat really well and hasn't clogged (yet).
It's also important to have lots of air through the P-channel. At least 1/2 if not 3/4 of the pre-fuel air quantity (after warm-up), at least in this stove.
I have a long stainless ashtray under the basket with a forward slanted deflector plate positioned in the middle of it. The deflector plate leaves a 1/4" gap just under the basket apex, and forces the primary air through the lower basket, creating a super-heated zone that turns the lowest pellets almost white. By moving the ashtray/deflector upwind or downwind of the basket, I can control where the flames occur. If I slide it more than 1/2" past the basket, the surface temp goes way up as the burning happens higher in the stack. This is how I've seen the 800+ readings.
I've been heating a 360 sq/ft shop for a month now. I burn about 5 cups/hour to start (air temp 60 deg/typical). I can get this thing smokeless in less than 2 minutes and up to temp (550), from cold, in about 12 minutes. I get my non-insulated shop to around 70 degrees before I dampen it down to 4 cups/hr. Takes about 45 minutes.
I'm working toward 2" and 3", all stainless, heavily finned/multi bell, gravity fed pellet heaters for sailboats/small spaces.
I'll get some pics to y'all once I've cleaned up my prototyping a bit. Don't wanna embarrass myself too much...
BTW Anyone use 410 stainless?
Jon
