Flame pattern - yellow streaks at tips

Ok, this has been vexing me. When I use butane, or Coleman Fuel in an Omnifuel, the flame remains a nice blue no matter what. Intense pumping, raging flame, little simmer flame, pot on pot off, butane can inverted (liquid flow) or upright (vapor) it matters not. Flame remains blue.

But with kerosene, the results are different. I use the 28 jet and get some yellow flame tips with a pot on the flame. With the pot off the flame, it is a nice blue with very occasional random yellow streaks in it. Nothing unusual as I imagine the kerosene has occasional large bits in it that don't burn well. It looks no different than a natural gas stove.

But when I place a pot on the kerosene flame, a small portion of the flame pattern turns yellow right at the tips. I don't have a good picture since it is hard to capture, but follow me here:

If the flame is a clock, the flame has a yellow tip from about the 9 o'clock to 11 o'clock position directly beneath the pot. Remainder of the circumference is blue. It's just the last maybe 20% of the flame length that is yellow.

I checked the jet to ensure it was sufficiently torqued and not leaking vapor that might disrupt the flame. So that's good.

Why this concerns me is the yellow tips seem to excessively burn the bottom of the pot. Now, it's a metal pot and not some family heirloom. I'm more puzzled about it in general.

Is there anything I can try differently? Has anyone else noticed this? I will theorize, and please tell me if I am correct here, why this happens. I imagine the cup and roarer plate like a venturi -- vapor leaves the jet, mixes with atmospheric gasses, and accelerates through the cup and picks up speed and more atmospheric gasses which are needed for complete combustion.

With the pot in place, that flow is slowed enough to where there is not sufficient atmospheric air to complete combustion fully. Hence the oxygen depleted area at the junction of flame and pot, creating a yellow flame.

But knowing or theorizing this doesn't fix the situation, if it is at all fixable.

 

Before we get to the fix, is it broken?

 

You have to ruin a perfectly good question with common sense, eh?

No, no problems at all. More of curiosity than anything.

 

Have you got the filter in the fuel line?

 

Yes, I checked the fuel line filter and the filter at the distal tip of the pump assembly. Both appear in good shape.

 

I would try a different brand of kerosene

Maybe try white spirits with the kero jet to see if you have problems in the same area. Might be hard to light but it should work.

 

When you refer to "white spirits" you mean something like odorless mineral spirits?

I have read the MSDS on one particular brand and believe this to be what you mean:
http://www.wmbarr.com/ProductFiles/KS Low Odorless Mineral Spirits (GL251)%206-4-10.pdf

Sound like the right stuff?

--

Nevermind. I just looked at a kerosene MSDS and the MSDS above. Looks like nearly identical stuff, save for a few minor differences. Will give it a shot.

 

I think its probably down to the kero here in the uk kero\parrafin varies quite a lot tho i burn it mostly in lamps i often mix some petrol or coleman fuel into the parrafin to make a lamp\stove run better it lowers the flash point get a better burn just try maybe 5% maybe up to 20% maybe in a stove
cheers pete

 

Here in NZ white spirits means coleman fuel, shellite, etc

 

On other stoves some have had success raising the flame plate a bit, I've never tried it myself.

Alternatively, if you wanted to spend the money, you could try another jet.

I can second what Pete says about the effect of adding a little Coleman fuel to the kero. But then you will be using Coleman fuel, which is not what you want to be doing here I surmise.

How bad is the soot? Maybe just live with it?

 

What sort of kero are you using? Water clear K1 that comes in plastic jugs? Or, the stuff that comes out of a pump at a filling station/fuel oil distributor?
If it's the latter, I'd suggest trying the former.
If it's the former, then I'm no help at all.

I threw my filters away long ago on the Omnifuel, and the Novas, too, for that matter. Your call, of course. Usual disclaimers apply.

Cheers,
Gary

 

Well, it has a faint tan color. Supposedly K-1 kero from a pump, but I bought it at a rental shop where turnover on their kerosene could be a bit low. I know of a high-volume filling station where the kerosene could be fresher. Still bulk K-1 from a pump.

If the filter is clogged or obstructed, what effect does that have on the flame itself?

I'm kind of confused at what the point of the filter is on any stove. The bottleneck in the case of the Omnifuel would be the valve at the stove or perhaps the jet itself. It seems like the filter just moves the clog up the line.

As for the soot, there's not much sooting at all. Just a coffee-brown burn on the bottom of the pans roughly in the shape of the flame pattern. Not a strong odor either unless you turn the flame way down which is when the stove becomes less efficient anyway no matter the fuel.

I toss a bit of kero with some coleman this evening and ran it through the 27 jet. Only when you pump the crap out of the tank do you see the yellow tips.

No matter the case, sounds like a skank batch of kerosene. I don't quite know what to do to get rid of the remainder of it. Burn it in a cup maybe or something.

 

Possibly what has happened is that the lighter fractions of the blend have evaporated off leaving the heavier long chain alkanes behind, so your fuel/air mix is richer than intended.

The pan will be interfering with the airflow into the burner by diverting the burnt gasses flat and wide instead of straight up. This air restriction is then not enough to fully burn the heavier fuel mix.

A splash of Coleman fuel reduces the average molecular weight of the fuel blend and so leans out the gas mix.

 

Just curious, what about a splash of methanol? That is what HEET fuel additive is and it is used to make water mix with gas so that it can be expelled with fuel as it burns. Would it do the same for impurities in kerosene?

Or is this what was meant by white spirits? Sorry but with so many names for these fuels in various countries it can be hard to keep track.

 

Since the odd flame colour is off to one side i'd suggest there is a wee bit of difference in the orfice of the jet. This odd bit of difference is causeing a bit more fuel to exit to that one area. This is not a problem as i see it unless this is causing great goobs of loose black soot on the pan. In that event you need to change the jet.

lance

 

Just use the kero in the stove, a few yellow flames will not hurt anything. If you don't want to do that, kero has many other uses: it is a great degreaser and is a good sub for charcoal lighter fluid (which is just kero with other stuff).

 

If you are scoring this at home, put Itchy on the board with +1.

This was solved by raising the flame diffuser ever so slightly. I pulled the center disc upward, straightened out the arms a bit (they were rotated slightly from the factory). Then I pumped the crap out of it until the thing sound it was full afterburner oh crap I just missed the arresting wire and I'm going to crash loud. I pumped it so much that it was bordering on just plain stupid.

No yellow flames anymore. Previously, vigorous pumping would be a 100% assured way to reproduce the situation.

I did try changing one variable at a time. Added 33% coleman fuel to the questionable kerosene. This helped a bit, but at full power it still had a touch of yellow in it.

I cleaned the jet, but suspect that as was mentioned there is perhaps the teensyest imperfection in the jet.

I'm still curious about the fuel quality. Home Depot has a 5 gallon drum of Klean-Strip kerosene for $32.50 which, albeit more pricey than the gas station price of kero, might be a bit cleaner. And it has the added benefit of not requiring that I drive through the ghetto to go find the kerosene station.

What I found with the plate was that if you raise it up too much, the flame wants to go out. If you mush it down, it creates a bit more hydrocarbon stink though the flame remains blue which makes me wonder if it is killing the efficency of the stove. I noticed there is a horrid sink on simmer with these stoves (most stoves I've used) and the research results that someone posted here about the differing stoves (Nova, Primus, MSR) from South Africa says the stoves are markedly less efficient at low output vs high.

Anyway, thanks for the help. Who knew the simplest part of the stove had such an impact on its performance.

--

One other thing -- raising the flame diffuser up had the same effect on the flame density and pattern as using the wrong size jet. For instance, trying to burn butane with the 27 jet. This makes me wonder if a fuel like diesel, which I have not yet tried, might burn better with the diffuser raised up a bit.

 

I was curious about this too, and did a bit of reading. Apparently methyl alcohol has a potential detrimental effect on gaskets and seals. I wear nitrile gloves at work, and noticed that both ethyl alcohol and isopropyl alcohol have a bizarre effect on the nitrile. They seem to strip a bit of it off, changing the rubber somehow. My concern with the methanol is that it might cause some harm to the o-rings. They are a user serviceable part and are included with the service kit.

Here's two references I found among thousands.

http://books.google.com/books?id=g3...0#v=onepage&q=methanol damage nitrile&f=false

Page 730

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA236040&Location=U2&doc=GetTRDoc.pdf
Page 11.

 

Just a comment in passing, recognizing that you were experimenting: while I ocassionally add Coleman to kero, I don't go above about 10%, maybe 15% max. And even then one can't "officially" recommend it. But higher and the increased volatility is too much for kero stove use, I think.

 

The filter on the fuel pick up stops muck getting in the fuel line, the filter in the stove end of the fuel line also stops muck but mainly regulates fuel flow (makes it more steady and stops pulsing).

If the filters are clogged the stove won't do at all. The stove will go with out filters.