Re: Stanley Burner Howling
Posted by: Mark Drake
Date: March 21, 2007 08:35AM
Hi Jeff, Mike,
Thanks for your input, I’ve got some interesting stuff to report, another long one…
I tend to agree with the you, Mike, that the ultrasonic / beat idea is unlikely; the tone just doesn’t have that kind of quality and also tends to be fixed in it’s fundamental and harmonic frequencies. The beat effect in prop aircraft is quite well known I think and can be extremely damaging.
Both your comments about smokebox flap and blower are most interesting – I too have had similar experiences with the smokebox flap on first start up.
However, down to the good stuff-
I took yesterday off to finish a plumbing job in the house. The job went so well that I spent the afternoon mucking about with fuel jets, here’s what I found (all tests initially with fuel at 140psi and ambient temp 5°C).
Jet Size 0.032” – Struggled to get the burner to light-off on hexane and flat refused to light on kerosene at all. The mixture was so lean that I could see that the pilot flame wouldn’t propagate across the burner – if I partly covered one of the venturis, I could get the burner to light off rather badly. Not recommended! But at least it showed that the mixture was too lean to burn.
Jet size 0.035” – Burner would just run on hexane, but the observed flame was a very pale blue in colour, unstable and not covering the burner plate completely. The burner would not run on kerosene, but would briefly light-off when fuel was first admitted.
Jet size 0.037” – Runs reasonably on hexane, but clearly unhappy. When switching to kerosene the burner would light-off, the flame was a thin blue in colour with lilac near the burner plate but I could see that flame did not entirely cover the burner plate. There was also a significant amount of unburned fuel vapour issuing from the smokebox flap.
Jet size 0.0385” – Goodness, what a difference! The burner lit-off sharply on both hexane and kerosene. No noticeable unburned vapour coming out of the flap / stack. The flame had a bright blue colour and sat fairly neatly on the burner plate. On first lighting, the burner howled a little but this disappeared within a few seconds. Once everything was thoroughly warmed through and I had about 300 psi of steam, I found that I could run the burner at full fire with no howling at all – something I just couldn’t do with the 0.049” jets. The burner just produced the usual strong hiss, with a quiet rumble.
I took the car for a run locally to see what the steaming was like, and this is where things get really weird. As soon as I moved off, the burner began to howl, literally within a ˝ turn of the wheels! Stop and it disappeared again. On the move, however, the burner still howls, but much less intensely, with a warbling quality, like Jeff describes on his Brooks. It also comes and goes quite readily, suggesting that I’m right on the margin between howling and not. It was a very cold day, so I’m looking forward to trying it when it’s warmer. Also this jet size gave much sharper burner response on the road, particularly when lighting-off when opening the throttle at the bottom of a hill, for example.
In reflection, I would say that fine tuning the mixture certainly has merit – just 0.0015” made a massive difference. However, I feel that burner howl is the product of multiple effects, a strong contender is the resonant behaviour of the whole system geometry. I think I’ll have a look at geometry and damping next.
Could temperature difference of the superheater cause the burner to only howl on the move and not stationary? I’m a bit stumped by that observation – I’m joining the ranks of the confused too…
Clocks change to summer time next weekend = more steaming time!