Why do some burners produce that distinctive howl and why are some silent ? (all you hear is a hiss).

My 740 howls when cold ie: first firing up but when the burner is hot it only happens if the fuel pressure is above 120 psi. Is it the burner plate resonating (surely a resonating burner plate will lead to cracking) or is it the venturi ?

Can the howling be stopped by a different sized nozzle and what impact will this have on the burners performance ie: taking the jets affect away from the natural frequency of the burner plate ?

I recall seeing the burner plate vibrating when I test fired it off the car, a frightening experience for one who has none.

Any and all ideas welcome !

Regards
Ian Vinton

Ian,

Nobody is rising to your bait!!!

There has been a lot on this over the years on both the Woodson and SACA discussion forums.

General view seems to be that the noise is due to resonance in the venturi pipes, much like blowing across a bottle or the action of an organ pipe. It can happen when the burner is off the boiler so it is clearly in the venturi not in the boiler tubes.

The airflow has to be such as to set off the natural resonating frequency of the venturi which is why the howl comes and goes depending on lots of factors such as fuel pressure, whether or not the fuel is fully vaporised, jet size etc. Putting a bit of suction on the flue with the stack blower will stop it. A slight cooling of the gas - say the fire has been out for a short time - will make it howl and it will also do this more when firing from cold than when up to temperature - I guess this means the fuel is slightly less than fully vaporised which will change the airflow characteristics quite a bit. I once out a bit of a wind deflector a couple of inches in front of my jets - howled like mad all the time!

Many people like as they think it means the burner is giving its best. I'm not convinced about that - if it comes on because the fuel is going in as a spray not fully vaporised I suspect the induction of air will be inferior and the extra fuel will burn too rich. The limiting factor in the venturi/jet system is the amount of air drawn in not the amount of fuel.

Mike

Mike,

If the whole source of the noise is in the venturi, why do Ottaway burners have such a reputation for howling? Certainly the Ottaway burner on my CX is much noisier than the conventional burner fitted to the Mountain Wagon.

Peter

My thoughts for the noise has always been that the venturi hits the natural frequency of the burner plate causing it to vibrate, this was seen when I test fired the burner off the car.
I am going to try different nozzle sizes to see if I can tune the burner to stop the howling which occurs when the fuel pressure is between 120 psi and 140 psi with the burner hot.

Peter,

Perhaps the Ottaway has a freer passage for the hot gasses than the Stanley type - I really can't say. Perhaps as in a violin, the character of the material surrounding the sound chamber changes the quality and volume of the noise. The thin Ottaway plate may be a like sound board which amplifies the howl.

Ian if you are brave enough you could poke your burner casting with a substantial steel bar to see it that stops the vibration and stops the howling. I think the howl is from the venturi and the vibration of the plate is a secondary effect so the howl should continue even if you damp the vibration of the plate. Don't singe your eyebrows.

Mike

Let me first say that I am not an expert on the subject, but thought this might be a reply worth reading.
The source is George Woodbury's book "The Story of a Stanley Steamer" published in 1950. It is from the part of the book where he is "firing up" for the first time.
He has "George" who works at Fred Marriott's garage who has come out to help him.

The following in quotes is fom the book:

He has the pilot going and George tells him to "open up the firing up valve and then shut it off". "That runs gasoline into the main burner system". "The castings are still too cold to vaporize kerosene, but warm enough to vaporize gasoline". "Now you can shut off the 'firing up' and turn on the kerosene." "As I did this a low, insistent hiss rose from the burner. The jets shot into the venturi a white tongue of milky vapor. The perforations of the main burner casting a blaze into a serried mass of blue flames, not very high but of such intensity we could feel it yards away. Then as though approaching from a distance, there arose a low mournful howl, eerie, anguished, as though voicing all sufferings of Mankind."

Now here is the part pertinent to this post from George...

"Raised your heat too fast. She'll stop in a minute".

It also appears that the fuel viscosity has something to do with it. I use a 50/50 mix petrol to diesel (sort of,I it mix at the fuel station so it's NOT really accurate). Sometimes it howls much worse than other times. It always goes away when hot BUT it seems just to go beyond our range of hearing; the pitch just keeps increasing (painfully so) untill it disappears, to us at least, haven't asked any dogs. I had a John Gould drilled burner and have just replaced it with a drilled STEEL burner. John's finally cracked too much to keep the backfiring at bay. The new burner which I've just installed (haven't driven with it yet; tomorrow I hope) Has more holes but smaller ones and it's tone is completely different. I'm thinking the howl is the fuel vapour going through the holes and causing the plate to vibrate. I don't believe it is the mixing tubes since they remained the same. Also I can,with the fuel valve drive the car below the howl point untill it's totally HOT, less power but less noise. And remember the howl is a GOOD thing; you can be assured the burner has lit off properly. Cheers Ron Parola

I have suspected for a bit that my Model H Stanley burner could be improved if I could get it to draw more air. The problem was that the branch forks were too close to the front axle so that I could only locate the jets about 0.5 inch out from the intakes. I had seen Ron Parola's picture of his venturis with an extra inner flared tube and thought I'd try this idea as well.

I had a chance to fire it up today with new branch forks with a slight alteration which let me bring the jets an extra half inch out. I found that moving the jets out really helps the burner - I was able to drive faster up my local test hill but still hold 480psi instead of seeing it fall to 400.

I've been playing around with a second inner venturi with the idea of boosting the induction of air. Bit like some of the old Zenith carburettors. My thought was that having the double venturi might help to reduce smoking as the burner ignites or goes out as the jets might be able to induce more air at those times through the smaller venturi. Well this part of the project didn't work out - the burner howled like hell, even firng with the starting valve at 40psi; on the main jets it screamed unbearably which it normally never does. Good I thought - howling more should mean more heat ......... wrong - it was much slower to raise steam, taking nearly 20 seconds to go from 350 to 400 psi instead of about 12 seconds without the inner venturi.

I still think the inner venturi theory is right - just needs a bit more fiddling around but I'm more than happy with the re-located jets so that's enough for now.

I think this experience pretty much shows that the howl comes from the venturi as that was the only thing that was changed. The howl was a much higher pitch than normal and warbled an octave up as well and this again makes sense because of the shorter length and smaller diameter of the inner venturi. I could reduce the howl a little by shutting the smoke hood lid.

Mike

Gentlemen,

I am relatively new to the world of steam cars so please excuse me if I talk a load of ‘hot air’! This ‘burner howl’ is a subject which has really taken my interest as I have a 1921 model 735 which drives quite beautifully, but the burner howls to the extent that I can barely hear anything else on the car. I'm always listening out for mechanical noises to identify trouble early and the howl makes this very difficult! The howl is present even at relatively modest burn rates.

Before I made any changes, I thought it best to talk to some people more experienced than I – but in so doing, I got back as many different answers as times I've asked the question…

However I had some dialogue with David Nergaard who recommended that I looked at the fuel jets first, with a view to checking that the size and fuel mixture was somewhere near correct. He advised me that the richer the mixture, the more likely the burner is to howl. Apparently the fuel jets should be 0.038” (No. 62) diameter. So I dutifully measured mine and found that they were 0.049”! This would explain why I was achieving good burn rates with the burner valve barely open i.e. a relatively low fuel delivery pressure, but the burner howling like hell. For your information, the fuel reservoir pressure is 140psi.

I have now made a new pair of jets and I will try them this coming weekend. I’ve made the jets deliberately undersize at 0.0315”, as it’s an easy job to open them out a little at a time. I expect all sorts of trouble with this small jet size as the mixture is likely to be on the weak side for any given fuel flow rate; but hopefully I may be able to ‘home in’ on a satisfactory combination of jet size / fuel pressure.

As for my theory on burner howl, I think it’s a product of the way that flame front speed is influenced by flow rate, temperature and mixture (and probably lots more)– but I’m sure it’s all been said before…

As luck would have it, I have access to a high-speed camera which can record around 8,000 frames per second for 2 seconds; I thought that I might install a small pyrex window in the burner casing, just above the burner plate and ‘gaze into the fire’ for a bit! I would be really interesting to see what the flame is actually doing close to the burner plate.

I’ll keep you posted on how I get on – good luck to all those other experimenters…

Mark Drake

I think I have heard all the different causes of burner howling from the most qualified people. Amoungst other things, due to the burner howling being directly dependant on the amount of fuel delivery, I would say that the cause of howling was as Mark has presented. The howling is caused by the oscillation of the flame front jumping up and down over the burner grate. A similar event can be experienced by using an oxygen/acetylene torch and giving it too much oxygen. The flame jumps away from the torch tip but continues to burn while making noise. Different harmonics of this noise is heard in the Stanley with the sound being piped up through the boiler's fire tubes, just like in a musical instrument. Personally, I like to hear just a "little bit" of this burner howl as it assures me that I have a good fire burning and the pilot light should still be lite. My Stanley burners howl more in cool air and also when the burners are cold than when after they have warmed up. To settle this debate, it would be really nice to find the sure cause for this howling.