Tuning Secondary by color

[BoilerMan]

Installed a secondary chamber window and now there is one more thing to look at

Wondering what is considered a good flame, it seems to be different than tuning a torch flame. One would think that the primary air would be the fuel gas (acetylene) and the secondary air (oxygen).

Well all was well until I actually moved the secondary shutter. I seem to have the bluest and most stable flame with the secondary almost closed and primary wide open. The book recommends primary 100% and secondary 33%. Right mow I'm primary 100% and secondary 5% in the middle of the burn.

What say you?

Tune to the most stable flame? color? time of burn? So many questions now that I can see whats going on in there! This is GREAT!

TS

 

[Floydian]

Hey Taylor,

I don't see any window......I guess you'll have to try uploading that pic again

Noah

 

[BoilerMan]

Ok ok ok so I actually uploaded a pic in this post

The color does not do it justice more blue than it looks in the pic.

 

[Floydian]

Sweet, nice job!

I can't really offer anything on adjusting the secondary. The Varm's flame just doesn't change much at all as far as I can tell.

 

[BoilerMan]

Well I was jealous of the Varm's window. So when I saw Dean at a forestry products show last year (3hour drive) I ordered one from him. With for drilling through cast iron and some machine work it looks factory installed

Taylor-made factory installed

 

[jebatty]

My Tarm has a window. I fiddled with tuning early on, but now just set the primary/secondary lever about mid-way and forget it. Color starts bright orange, changes to orange/blue, then light blue about half through the burn, then colorless and just a roar. The window does fog up with ash residue and a light film of creosote forming on water condensation on the glass at a cold start-up. A wipe of acetone cleans the glass easily.

 

[BoilerMan]

Jim, I find that the secondary is unstable and will not stay lit with the recommended secondary setting. I'm going to have a few more burns and see if it's similar. I must admit it sure is fun to actually see the source of that secondary rumble now. I figure I've invested $70 all said and done in this little summer project. 70 bucks for a 1" window glad windows for the house aren't $70/inch

TS

 

[jebatty]

With the Tarm, things that help getting the secondary going quickly are: 1) a good ash bed in the firebox. Leftover unburned coals also help a lot to provide a good ignition source as the gases pass through the new wood load and into the gasifer slot. I don't clean mine out very often. 2) an ash bed on the floor of the secondary burn area might help some, at least it provides some protection for the floor refractory. 3) on start-up with bypass damper open, getting a good fire going in the firebox and flue temps up to about 300F or more with a good draft, then closing the bypass damper. 4) dry wood, of course. With these, the secondary burn (bright orange) starts almost immediately.

 

[maple1]

The flame will change through the burn, and also from burn to burn if you've got wood that's a bit inconsistent. Mine acts like Jims too - starts orange, then the blue/purple comes in, then it goes clear.

So you could turn this into a constant endeavour, if you wanted to.

My secondary air shutter thingie (which is actually just opening & closing the viewing window) stays pretty well closed all the time.

 

[Tennman]

Don't know how I'd have ever learned to run/tune our boiler without a window. You'll love reading the burn health from the glow as you step into a dark boiler room. Your color is about as good as I've ever seen. Rarely have I seen only blue without a hint of orange. The manufacturers recommendation probably covers a broad spectrum of users and wood quality. You're certainly not their average customer and I suspect you're burning wood with better than average moisture content.

I've never seen a flame like in the Econoburn ad, looks amazing. But I think on a flame color chart white is cooler than blue. Anyway, I'm happy when I see your color in my burns. Best wishes.

 

[TCaldwell]

what you are describing, flame ionization, is used in burner/combustor design. Through flame and fluegas analysis the burner and combustor can be optimised. In a batch burn, the conditions and primary/secondary air need to be manipulated to maintain that flame color you show. The 30% sec air would be a good choice for a batch start, a little short for high burn creating a very hot sec burn tenp and a low o2, and good towards end of burn for a large wood load. However as you saw by the yellow flame, at that point in the burn 30% was too much excess air to maintain a good flame, when reduced to 5%, the air fuel ratio was good. This is also represented in fluegas analysis, a yellow flame from too much secondary air will show a high carbon monoxide level[ unburned fuel] and a higher flue temp. Also its doubtful if the p/s air flows are induced at the same flow rate, causing 30 and 100 to be ammt of damper or slide open, not true to airflow volume. all in all, chasing the flame can give alot of insight to a control strategy!

 

[jebatty]

My understanding is that hydrogen and CO burn color-less, starting a little over 900F for H and CO starting somewhat over 1100F. When the "flame" turns color-less, I would assume all that's burning is H and CO. That's a pretty amazing point. I'm still in awe of the color-less burn. Just a roar.

My astrophysicist brother says that's one reason H is so dangerous when it combusts - you can't see that anything is burning.

 

[Tennman]

TC, Where did you get your O2 sensor and what type. A guy in the BioMass Sticky used an automotive sensor and display. I don't intend to add control, but it would be useful for damper tuning.

 

[TCaldwell]

the insitu fluegas analyser, a o2 sensor with a calculated co2 value based on a fuel factor for wood and a flue temp, is what I use for control. Its made by adc gas analysis and called the optimiser, it has a bosch lsm11 wideband sensor. This is a single gas analyser,higher price will sample more gasses, like co and calculate nox ect. I have a low end testo 327 portable fluegas analyser, provides much more comprehensive info but cant control from it. The testo employs extractive sampling. I think tom from maine has a uei baby bell, portable unit, not sure how he likes it but would be fine for spot checks and damper manipulations. A unit like this will provide more useful info than just o2%

 

[Tennman]

Thanks TC. The Optimiser is impressive but more capable than I need for occasional tuning/spot checks. I'll check out the others. Thx

 

[BoilerMan]

I've been trying to talk my boss into buying a testo. He is a master oil burner but we now focus mostly on electrical, refrigeration, and controls. Color tuning is the next step in my control strategy. with the ultimate goal of closed-loop air control.

TS