Orange flames with Omnilite Ti silencer

Discussion in 'Stove Forum' started by Oksen, Oct 20, 2020.

  1. Oksen Norway

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    Hi guys,

    having read earlier posts about the Primus silencer for Omnilite Ti and underburn issues, I still went ahead and bought one because I dont plan om running it om gas canisters anyway. Turns out that it burns with a very orange flame on both white gas and isobutane, all the way from simmer to full throttle. Has anyone seen this before and know what might be wrong? Got a replacement and no difference there.


    Tried white gas with the 0.36 jet intended for gas canisters and then there is finally some blue color, but it turns yellow after s minute or so:


    I cant really figure out whats wrong
     
  2. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Oksen The cap of the device is getting up to red heat and colouring the flame.

    The same issue was reported HERE in respect of a Manaslu with a roarer burner. Same Manaslu stove and jet:

    Original flame ring.

    041D4EEE-D924-4A28-AA7F-7C68ED7DBFE3.jpeg


    Flame ring from another make of stove.

    951DE60B-6B25-4280-884F-C7CD33A7D5FD.jpeg


    The effect is even more pronounced with your silent burner converter than with the Manaslu roarer because the flamelets are generated within the red-hot metal of the cap and not below the vapourising chamber on the roarer burner.

    I doubt there’s a user solution, short of re-manufacturing the cap in different metal, or chucking the design and starting again! Failure of design, previously reported here on CCS as you say - reported by @ArcticFlame as underburning.

    John
     
    Last edited: Oct 20, 2020
  3. Oksen Norway

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    Thank you for the reply. It does look like the metal discolors the flame. Does it cause incomplete combustion though? Should I get tid of the thing?
     
  4. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    ArcticFlame suggested it developed underburn, but he also seems to have got acceptable combustion out of it with the smallest jet. I don’t have one so I can’t speak from personal experience.

    If it really does underburn, the device would literally burn itself out after a few sessions. If it’s not underburn and its just discoloured flames you might be willing to accept that for the trade-off of silent burning.
     
  5. G1gop

    G1gop United Kingdom Subscriber

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  6. Oksen Norway

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    Im mostly concerned with co production. With the roarer bell it burns with a blue flame and all looks good. I find it strange that the biggest jet makes the bluest flame when using the silencer. Should it not be opposite?
     
  7. Reflector

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    I've only used mine with isopropyl alcohol (enlarged the kerosene jet to 1/32" for anyone curious) and it produce a blue flame with alcohol. If I have a chance I'll fire it up on pure butane later and see what it looks like to report back.

    Perhaps what's going on with the Omnilite silencer is that it needs enough vaporized gas flow to ensure proper air mixing with the fuel mixture? Recently I some flow restriction my Soto Stormbreaker and it caused a lot of underburn with an orange flame on pure butane but less so with white gas where it instead mostly had a loss in output. Just a guess as to maybe what causes the orange flame.

    I've heard that some stove designs have more "optimal" air and fuel mixing at higher flow settings as the flow is sufficiently turbulent enough to create a proper mix. I've noticed this in some canister stove designs where a very low simmer produces a little bit of a yellow core in an otherwise blue flame but they always work fine at any of the higher settings.
     
  8. HunterStovie

    HunterStovie United States Subscriber

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    @Oksen

    I removed the large screen from the inside of mine and the flames are much prettier.
     
  9. Tron

    Tron Subscriber

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    You should leave the silencer stock, it will "season" within a couple hours actual use and give a perfect blue flame. I have two of these and they burn very yellow at first, it is like they have either some coating that needs to burn off or the opposite, the steel needs a smear of carbon not to colour the flame. By the way, these burns perfectly with canister fuel as well, in my experience. I do not know wether Primus have made changes to them or if previous reports of trouble with these silencers ar due to other factors than than the silencers themselves. I have had nothing but excellent results in both my TI`s (one stock, the other in a Trangia adapter) burning both white gas (Aspen) and canisters. I have used both mine a lot this year, apart from the jet needing the occasional unclogging (very tedious with Primus stoves) they alway burn perfectly, with the stock silencer.

    Truth be told, I have only used the large jet with canister gas a couple times for testing, for regular use I leave the .32 jet in the stove for both fuels.

    Kind regards
    Tron
     
  10. Tron

    Tron Subscriber

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    You should also clean the jet regularly at first, if the stove is new.

    Kind regards
    Tron
     
  11. SimonFoxxx

    SimonFoxxx Subscriber

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    I have a Primus Omnilite Ti stove with a Primus silent burner. It runs very well on white gasoline (Fuelite here in New Zealand) and iso butane & propane mix. Never any sign of orange flames. On a very low simmer, sometimes under burn occurs. This is not unique to this stove. It also occurs on very low simmer with other stoves with an optional silent burner, where a roarer is standard. Having said that, I have never had underburn with my Coleman 400 brown, which has an excellent simmer.

    Cheers
    Simon Foxxx
     
  12. Reflector

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    I've been experimenting with the Primus silencer on my Omnilite Ti and found a way to reduce or eliminate the orange or reddish tint in the flames. After heating the stove up sufficiently and getting it to operation, cut the flow and let the cap cool down until it stops glowing (5-15 seconds). Then open the valve for a half second before lighting the stove off, the jets from the holes should be long and spindly when the valve is wide open. I think what is going on is that some of the flame does make it inside the holes a little and makes the silencer heat up a bit.

    Caveat: This is only from a single session of experimentation and a few relights to test. I'm running a weird mix of kerosene, character lighter fluid (which is some kind of heavier cut of naphtha) and white gas through the white gas jet.
     
  13. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Reflector Full marks to you for persistence in experimentation. Zero marks to the cap designer that it should require that to get a decent flame. Can you imagine how your procedure would appear in printed instructions?!!
     
  14. Reflector

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    I ran the Omnilite Ti with the silencer again today but it was getting to sunrise so I couldn't tell how relatively blue the flame was as well as when I ran it at night. Lengthy and necessary preheat aside due to the fuel mix it seems the same method of getting the stove operational: Running it normally until the flame turns a bit red to ensure that the cap and bell are hot, turning the stove off and relighting it makes it work.

    There's an alternative way of lighting it off and that's to hold the lighter flame about 4-6" away from the top of the stove and then cranking the valve on the stove open rapidly before bringing the lighter down. It'll light with a "bloopf" but it seems to allow for the flame to be blue or mostly blue.

    I say mostly blue because this isn't at night and when the bell heats up to the point it glows a little reddish at maximum power the flame itself will have a slight reddish tint in parts of it. It is otherwise mostly invisible against daytime so I assume the flame is fairly blue from what I can make of it.
     
  15. ArcticStoves

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    Oksen: Though there are many here who know far more than I on silencers, I gave up on the idea of putting one on a possible MSR XGK-II a couple of years ago, as I realized it could not really work in subarctic winter temperatures. Thermodynamics.

    In the end, I put more effort into insulating a Trangia-25 for winter alcohol use, and stuck with a refurbished MSR Whisperlite for occasional white gas use in winter.

    If you do work out a way to light a white gas stove with a silencer at -30C, do let us all know!!
     
  16. 907_Nick

    907_Nick United States Subscriber

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    I bought a new Omnilite TI last fall and have been using it all winter without any issues, even at low simmer. You might try contacting Primus tech support. They sent me a new burner bell and valve free of charge just because I asked if I could buy one!

    I always prime with alcohol. If it gets really cold I just take the silencer off and use the roarer spreader. There is a lot less metal to get up to temperature with the roarer plate and priming is much easier. If you want to use the silencer in cold temps you might need to double or triple prime - and that's with white gas. The instructions say not use the silencer with Kerosene, I've gotten it to work it just takes more priming than is practical in the winter - it's ok in the summer though.
     
  17. Reflector

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    I think I figured out what the problem is: The white gas jet is clogging up during preheat and causing the fuel mixture to run closer to lean than rich. Looking at the design of the cap, it lacks the holes in the burner bell in contrast to the splash plate bell. All the air is coming through the holes in the bottom of the base.

    When I tried running the silencer with another fuel mix I thought it was the problem of the charocal lighter fluid I added more of to my fuel mix but instead it is the jet clogging up during preheating. When I light the stove off I found an unusually weak flame in contrast to when I had been experimenting with it from the night before and it would slowly become redder and redder as the cap itself heated up. Furthermore I thought I hadn't pressurized it enough and continued to pump, the action of the stove wobbling a little as the force of pumping bumped the fuel line a little and tipped the stove back and forth. The output went up and I realized what was going on.

    After a full run, I used some paper towels as an improvised shield and unscrewed the cap and prodded the jet with the cleaning needle. There was a tiny bit of resistance but only a tiny bit. A good jabbing and re-screwing on of the cap and reheat afterwards with alcohol the output was exactly what I remembered from the night before. I'd say it was 2-3x of when the jet was clogged up.

    I find the problem is caused when the Omnilite Ti is being preheated and the valve is closed but the stove isn't fully heated up enough to vaporize fuel. Leaving the jet ajar causes some crud to build up in the jet and it doesn't clear away readily. I may have to experiment with seeing if a MSR shaker jet can be stuck inside of the jet and left there because disassembly is a massive pain.

    Through most of the valve settings on anything but the lower end I was able to get blue flames. Pushing it more aggressively and with my fuel mix (Kerosene-CLF-White Gas) would show some yellow flames that were "entrapped" in the blue but at that point the output on Omnilite Ti was through the roof. The problem seems to be that the cap doesn't like operating in a specific regime.

    If I were to describe the output of 100% being the point where the stove puts out a 100% blue flame without a hint of yellow flames, then this is what I would say is going on:

    1% / Super Simmer - Cap glows faintly red
    10% - Cap glows red with blue flames dancing around inside
    20% - Cap begins to underburn
    50% - Cap is OK, begins to cool off as the flames "exit" from the holes
    100% - Cap is OK
    150% - Some yellow flame tips show up in some of the holes on one side (like a quarter)
    200% - A lot of yellow flames show up but the flame is still mostly blue, just with a yellow core (doesn't seem to soot readily?)

    So there is a sort of "no go" zone for the cap, regardless of ignition methods as the throttling back of the stove causes the flame to retreat inside of the silencer cap. Note the length of the flames, a clogged jet causes the flames to become short little nubs or dimples rather than spindly long jets around the silencer cap. I assume that is the lean combustion that is occurring a little too deep inside of the cap or otherwise the flow is too low and combustion occurs a little closer to the holes rather than occuring right outside of each of the holes as a jet.

    This is how you know the jet is clogged and the fuel mixture is lean, the stove operates as normal but output is reduced and there is a faint red/orange halo. This is a "milder" condition but it got worse over time. Turn the stove off, let it cool or use something to prevent burns and unscrew the cap to clean the jet. It will only get over time:
    Clogged underburn.jpg

    This is the "no go" throttle setting around "20%" you really want to avoid, increasing output to a certain point will cause the underburn to get worse:
    Valve setting induced underburn.jpg

    This is the "150%" valve setting from my fuel mixture experiments, as the jet was recently cleaned this is pushing the limits as to how well the stove can vaporize or mix the fuel but this may also be part of my fuel mix being a little richer than white gas in regards to the oxygen requirements:
    Overthrottle rich fuel mixture.jpg

    And this is simmer underburning which I think shouldn't be too harmful to the cap so long as it doesn't continue to underburn when the jet isn't clogged and the cap rapidly cools off when the valve is opened up:
    Simmer underburn.jpg

    This is proper operation at "100%":
    Proper operating cap.jpg
    Proper operating cap 2.jpg

    An additional note for anyone having issues heating the stove up: When there is nothing on the stove the cap and bell tends to run cooler but this is especially the case with the burner bell. Placing a pot (even a raised bottom of a heat exchanger pot/kettle) will reduce the free flow of combustion gases (which will force them against the bell edge/change the flame pattern) and will quickly cause the bell to begin to heat up and it will begin to glow red depending on the throttle setting when it previously wasn't. I suspect operating the stove at a lower setting when it is still warming up and incapable of supporting "wide open" and placing a pot on will let it heat up faster than if the burner had nothing over it.
     
    Last edited: Feb 7, 2021
  18. Reflector

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    A correction to my post from above: Only get over time = Only get worse (with underburn) over time.
     
  19. Reflector

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    I'm now fairly certain that a lot of the (unacceptable) underburn issues is caused by a clogged jet in combination with the lighting method. With the jet clogging up the fuel mixture ratio becomes leaner and leaner as it mixes within the cap and is capable of early ignition right as the mixture exits through the mesh. This leads to certain output levels inducing some underburn and with further clogging the mixture must be running so lean that it outright wants to combust at the mesh.

    After cleaning the jet yet again after some significant usage (several hours) and bad priming starts I once again found that the flame could become a bit rich with ease at lower output settings in contrast to the past few days where it only became too rich at the highest of outputs with a highly pressurized bottle. However what I noticed was that the burner bell tended to glow less intensely at the settings that had it glowing a nice cherry red. The silencer cap itself also tended to be more resistant to underburn induced heating as it glowed far duller. It looks like the "safe" kind of underburn at the "super simmer" setting I refer to in the above post.

    I also noticed a little more buildup of a little bit of soot on the bell lip in comparison to the previous times I've fired it up where I was left with a mostly clean brass bell against the flames. So there is definite cooling provided by a "rich" fuel mixture.

    My advice for anyone with an Omnilite Ti is to try cleaning the jet first. Then try igniting the stove from further away and only after opening the valve with a brief fraction of a second wait if you're using a torch.
     
  20. Tron

    Tron Subscriber

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    Sound advice, and I think you are pointing at very possible culprits for those who have had bad experiences with the TI silent burner. As mentioned above I have had nothing but succsess with it, but I have had to clean the jet regularly when the stove was new. I also always light silent burners the way you describe. When I first bought a silencer cap for my Optimus Nova I remember the instructions clearly adviced that you should light the stove (with the silent burner) by keeping the lighting source away from the cap and let the combustible mix reach the flames.

    I have had no incidents at all with underburn using the TI, neither with white gas (Aspen) nor canister gas. I use it a lot to cook cheese sandwiches and make cofee with a bialetti, meaning very low simmer for many minutes. My only criticism towards this stove is the lack of a built-in cleaning needle. Having to remove the jet to clean it with a needle, that can easily get broken in my backpack, is very cumbersome.

    Tron