Last piece of the puzzle on homemade gasifier

[mlappin]

I'm on the 14th heating season of the conventional OWB I built, before the next heating season I plan on having a gasifier built to take it's place. I've calculated firebox size, nozzle size, secondary reaction chamber size and my heat exchanger.

I've done a search in these forums but haven't found what I was looking for so if this has been covered before I apologize.

Last piece of the puzzle is this. I have my CFM calculated but haven't been able to find anything on what static pressure to expect so I can properly size the blower. Is any static pressure that's encountered strictly a result of restrictions in the primary and secondary air supply assembly's or will some back pressure as well be present from the gasification process?

At first I wasn't to concerned with this but I spent an afternoon and drove over to the next county where the Natures Comfort GT6000 is assembled. I talked to the production manager and it came up they had difficulties in finding a squirrel cage fan that would deliver the required CFM at the static pressure their stove had, part of this I'm sure could be alleviated by increasing the size of their air feeds to the secondary chamber. The CFM was never mentioned but it was mentioned that the fan they use could supply the required air up to 2 inches of SP.

I also seen a new video of P&M's Optimizer 250 and it clearly showed what I would consider a higher pressure blower, narrow width but larger diameter and from the soundtrack on the video it sounded like their fan was a high speed one. I've thought about buying a fan directly from P&M but I'm also aiming for a continuous output somewhere between the 250 and 350 so it may be undersized.

Any thoughts on this or a point in the right direction would be greatly appreciated.

 

[mr.fixit]

Surplus Center has a couple that are relatively inexpensive to try; http://www.surpluscenter.com/Electr...M-115-VAC-McMILLAN-BLOWER-2051762-16-1436.axd

The flue draft will probably affect cfm needed,as on my boiler with cold flue start I turn the fan on 100% and after things get warmed up I can turn it down some.

If you can put some sort of adjustable flap on the blower intake you could adjust while burning.

It will take some experimenting for sure.

 

[mlappin]

I have two ways I might pursue adjusting airflow while burning:

1: I've found several two speed blowers that might work, start on high then after water temp starts to rise have it run on low.

2: I've also found a few three phase blowers that would work. Use a VFD controlled by a PID. Start out at a user determined speed then as water temp rises have the PID keep throttling back the fan speed to a predetermined low. If heat load should be high enough that it starts to loose ground have the pid controller speed the fan back up.

I use a couple of PID controllers already in our grain drying setup as well as a few VFD's that have built in PID's. The auto tune function is a gods send.

 

[mlappin]

Thanks for the suggestion with the surplus center, problem is with McMillan is they only sell to manufacturers in lots of 250. So I'd either have to order several for spares or try to figure out what that fan was used on originally and order from that manufacturer.

I was hoping to find a common fan thats easily replaceable, like from WWGrainger or McMaster Carr, a sealed non ventilated motor would also be a huge plus considering this will be outside.

 

[cityboy172]

Very interested in seeing this as it progresses.

 

[cityboy172]

A ball bearing air conditioner condenser motor would work well. Plentiful and cheap.