Hello from Upstate New York

Subject: Hello from Upstate New York Wed Mar 18, 2015 1:28 am

I've been investigating and contemplating a RS build for some months now. After watching numerous videos, I ran across ppotty1's ‘cast riser’ series. These have really piqued my interest mostly with incorporation of a pre-heated outside air feed. I’m especially interested in finding out where exactly is the most efficient\effective place to introduce air from the beginning of the burn chamber to the top of the riser tube or beyond. Along with that, I’m curious to learn more about T2H Instructionals’s dual vortex design and thoughts. I'm intrigued to know if the presence of induced vortices is truly evidence of complete gasification and if two is actually better than one.

As a novice with zero builds to this point, I’m not sure how much I’ll be able to contribute to this forum but I look forward to learning more from the posts here. One of my interests though is in modifying an oil-fired forced hot air furnace as a rocket stove and maybe eventually doing the same with an oil-fired boiler system. A cast iron boiler might present an issue due to its weight and the fact that most of the old ones I’m familiar with are removed in sections (broken apart usually with a sledge hammer) making reassembly impractical. That said, if one were attainable in safe operating condition (an older, less efficient model being upgraded for a newer one) I might be willing to take a run at it.

I look forward to viewing all the design ideas and thoughts out here. Thank you for adding me to the community.

g man

Moderator Posts : 1477 Join date : 2013-12-08

welcome to the site g man

you will have some fun reading through the posts on the site plenty of info on builds

you might like this post here

https://woodstoves.forumotion.co.uk/t14-from-kyoto-japan

Subject: Re: Hello from Upstate New York Wed Mar 18, 2015 5:31 am

gadily, I had seen part of that thread just before I signed up today. Now I'm anxious to catch the vids and read it more thoroughly. Thanks again!

Posts : 113 Join date : 2014-11-13

hey g man,
Lots of great stuff here, glad you joined!

Subject: Re: Hello from Upstate New York Wed Mar 18, 2015 6:34 am

gman,

Welcome to the forum. I see you are from upstate New York. I am about an hour south of Buffalo. There is a lot to learn here. I too am very curious about the benefits of the vortex. I can tell you that i followed ppotty's design and have a great votrex.

Vesuvius

Subject: Re: Hello from Upstate New York Wed Mar 18, 2015 7:27 am

keepittoasty wrote:: hey g man,
Lots of great stuff here, glad you joined!

Thanks keepittoasty. I appreciate the warm welcome (pun intended).

Subject: Re: Hello from Upstate New York Wed Mar 18, 2015 7:32 am

Vesuvius wrote:: gman,

Welcome to the forum. I see you are from upstate New York. I am about an hour south of Buffalo. There is a lot to learn here. I too am very curious about the benefits of the vortex. I can tell you that i followed ppotty's design and have a great votrex.

Vesuvius

Hey Vesuvius. I'm a couple hours east of you, just north of Albany. Can't wait to have the time to actually put something together, even on a small scale. I look forward to learning all I can and maybe someday even being able to contribute. Thanks.

Subscribers Posts : 333 Join date : 2013-10-07

Welcome to the forum g man.

g man wrote:: These have really piqued my interest mostly with incorporation of a pre-heated outside air feed.

For some time there have been some discussions on the benefits of introducing pre-heated air into a wood stove. Some people tried to establish parallel between an internal combustion engine and a wood stove, but of course these two work best under total different conditions. This French guy gave a very convincing answer https://www.youtube.com/watch?v=VCZSR3CFn8U and ppotty confirmed his results.

g man wrote:: I’m especially interested in finding out where exactly is the most efficient\effective place to introduce air from the beginning of the burn chamber to the top of the riser tube or beyond.

Just to give some examples, take a look at mine, T2H, ppotty's videos, take a look at https://www.youtube.com/watch?v=NJENCc3o_-Y , https://www.youtube.com/watch?v=crcRDazNVfM

g man wrote:: I'm intrigued to know if the presence of induced vortices is truly evidence of complete gasification and if two is actually better than one.

Vortex is useful for combustion on rocket stove heaters. From the laws of physics, a vortex is a place of low pressure, thus a nice place to introduce heated air to improve smoke combustion. Beside that, the vortex keeps fire and burning materials for a longer period inside the riser tube, allowing a better combustion.

Without using external energy input, like in any chemical reaction (there is an equilibrium point, never total reaction of initial components), in wood combustion there is no complete gasification. In this forum we are just trying to shift the balance point of this chemical reaction a bit further in the direction of water and CO2 .

g man wrote:: As a novice with zero builds to this point, I’m not sure how much I’ll be able to contribute to this forum but I look forward to learning more from the posts here.

You're already contribution with your questions. Curiosity makes us go forward...

Posts : 113 Join date : 2014-11-13

I second that motion, gman. heres an example of the discussion prompting more understanding....

(there's a whole lot, I'm trying to understand hahaha)

caotropheus wrote:

Vortex is useful for combustion on rocket stove heaters. From the laws of physics, a vortex is a place of low pressure, thus a nice place to introduce heated air to improve smoke combustion. Beside that, the vortex keeps fire and burning materials for a longer period inside the riser tube, allowing a better combustion.

Im glad you wrote that. I sort of understand things there, but I think in the end, Ive still got holes in my understanding.

Im wondering, where the low pressure happens. If we could take PPotty1's cast riser as an example. So, the draft pulls the hot gasses from the firebox and they hit what I would call a restriction(the curved part), logic tells me that the pressure would increase where the firebox meets the riser and then even more just past that at the wedge. The wedge being where the curve of the gasses happens. Is the low pressure happening just past this where the full diameter of the riser is achieved(after the wedge)? like where the flame is swirling?

It seems like that's where his secondary comes in. Is it the drop in pressure that pulls the secondary air in?

Could we then create a second vortex area just further up the riser a tad with another shape change and heated tertiary air?

sorry if this seems all over the place, my head is all over the place trying to figure this out!
thanks guys, thanks g man!

Subject: Re: Hello from Upstate New York Fri Mar 20, 2015 7:48 am

Caotropheus

Thanks for the explanation on the Vortex and it's role in the rocket stove.

This leads me to another question about the draw and where and how it is produced. If the vortex creating restriction in the burn chamber, creates an area of higher pressure followed by a drop in pressure immediately after the restriction, would there be a further pressure drop as the heated air exits the top of the riser? I expect there might be a pressure drop because of the wider section through the heat exchanger and also in part because the air takes up less volume as it cools in the heat exchanger. Has anyone done the calculations or better yet what equipment would be required to check pressure and airflow of the various points in the rocket stove?

Or... am I over thinking and complicating the issues?

Vesuvius

Moderator Posts : 1477 Join date : 2013-12-08

the restriction actually causes a speed up of the flames entering the vortex area this also means you have a better pull on your firebox

with this effect taken into account a secondary air can be used as the tube will have low pressure inside of it therefore pulling in air into the tube to be burnt

i tend to see it with central heating systems with the feeding tank been on the return side of the boiler and then the pump after the boiler as the water does pull slightly down when you first start the system up

Subject: Re: Hello from Upstate New York Fri Mar 20, 2015 8:14 am

Gadily,

Thanks. I have built a cast burn chamber following ppotty's lead but I am planning to use your idea of a pipe running through the burn chamber to introduce secondary air. My hope is that this will superheat the secondary air.

Does anyone have any advice on what equipment might be used to measure airflow, pressure and heat within the stoves?

Vesuvius

Posts : 113 Join date : 2014-11-13

nice explanation guys, helps me understand this a whole lot better

Moderator Posts : 1477 Join date : 2013-12-08

the simplest way to check air flow or suction on a system is using a manometer a manometer can be used also for pressure as well

heat would be a heat probe as a lazer gun would only be able to do the outside temps

http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section2/Manometers.htm

you can also use them on a vacuum as well

this one gives the velocity pressure or how to do it

Posts : 113 Join date : 2014-11-13

the last video points out to something important, air pressures in the living space.

When I run my woodstove wide open, i"m pulling the same volume of cold air through leaks in my home, that I am sending up the chimney. Warm sitting on the floor in front of the stove, move 6 feet away and sit on the floor and their is a cold draft.

Without any make up air, I am heating and cooling the home at the same time. Even with a very efficient design of a stove, over all efficiency of the heat in the home decreases.

I would argue, in my old cabin, its not that bad, because it keeps fresh air introduced into the home all the time. But it is not very efficient and it wastes wood.

My greenhouse stove will bring the primary and secondary air directly from outside as I am not interested in exchanging any air, without control over the process.

It is dangerous in a new construction home, as we build a tight envelope. In a home I was working on I saw a natural gas water heater back drafting, into a home during the winter. It was because it had a woodstove, a clothes dryer and a kitchen hood and bathrom fans, all putting the home under negative pressure. WIth a tight envelope and nowhere to pull from, the flue of the waterheater became the house intake. Luckily there was no fire.

I remember reading about a home that had a stylish, but giant stainless hood in the kitchen and it pulled so hard on a tight home, you could read vacuum levels in the soil of the yard. They were pulling Radon into the home.

So if any of you guys are running the stoves in tight spaces, remember one out equals one in, be sure to include make up air into your design and install.

sorry that was way off from measuring vacuum in the riser, but I felt it was worth mention.

Subscribers Posts : 333 Join date : 2013-10-07

Gentleman, I do not want to hijack g man's presentation thread.

I just want to refer that I think that you're right in your general observations. From my empirical experimentation and knowledge that I accumulated playing with stoves is that all the combustion happens where the fire is, this means that if you want secondary burn it has to be at the edge of the primary burn flame and if you want tertiary burn, it has to be on the edge of secondary burn flame, and so on...
Also, overall, independently of local high pressure or low pressure inside the stove, if there is no overall low pressure at the flue exit, the stove will not work.
No doubt that a set of measuring devices for pressure, temperature, flow speed, flow volumes and flue gases composition would make us a lot more knowledgeable!