Hi Pete, Thanks for the info. This may help with my attempts to quieten a couple of my engines. (Made in America, built in China). A Shay was made to run quietly by fitting an 8 mm burner into it with holes, not slots. It takes a little longer to get on the boil, but runs longer when hot. 1) My pulsations were not at a constant rate. and 2) they stopped when I cooled the gas tank!. very definitely temperature has to do with this problem. Maybe also the tank form? I have fitted a new tank of different form and set it in the rear of the engines side tank with a large part protruding into the cab. The problem is solved for this engine. I wanted to keep the original gas tank if I can (the engine is old) So if I can solve the problem - or have it solved! I can keep my restoration project unchanged.
As I wrote in my last mail All of this model engines suffered with pulsating burners. Usually toward the end of the run. The information is reliable. I have had some very good and unusual cures offered. One was to try a piece of a cigarette filter in the jet holder. I will be trying some of the suggested cures to see if I do get a solution. I'm about to start on a new project : this time a Ulysses Also very old and down at the heal. I may have luck here as well. Thank you again, I'm learning a lot . Regards Bert Am 19.07.2011 um 22:19 schrieb Peter T: > >> I have heard from an informed source that ALL genesis engines had a tendency >> to > pulsate. > > Bert, > I was waiting for some results yesterday so I idly googled (and binged) "gas > jet pulsing' which thrust me into the world of pulse jet engines. The first > thing I noticed on Wikipedia was the phrase 'resonant combustion'. I've seen > gas burners pulse, so I figured it was time to try that as a search. > > This popped up in a paper on noise from gas burners. > > "Combustion driven oscillations > Combustion driven oscillations arise when positive coupling occurs between > the flame and the acoustics of the combustion system, ie when the flame acts > as an amplifier of disturbances (acoustic or fluidic) at some natural > frequency of the combustion system. Although this phenomenon is relatively > uncommon, when it occurs, it can give rise to extremely high noise levels > within a relatively narrow frequency range. Hence the descriptions of this > phenomenon as: > - Combustion oscillations > - Combustion resonance > - Pulsations > - Combustion hum > Combustion oscillations normally occur if there is some similarity between a > characteristic frequency of the flame (eg the mean residence time in the > flame, or an eddy shedding frequency in the fuel or air supply to the flame) > and a natural Helmholtz resonator or organ pipe frequency in the combustion > chamber, flue ways, or air and fuel supply systems (often in combination)." > http://www.handbook.ifrf.net/handbook/cf.html?id=176 (International Flame > Research Foundation) > > I didn't buy Tom Burns' (excellent) theory, as pulsations are usually at a > constant frequency. If you had bubbles or surging, it wouldn't be a fixed > frequency. [Maybe it isn't anyway?] > > That last paragraph above should give you some ideas. Before you change the > tank, try altering the gas pipe length and/or the flue size (insert a liner ?) > > > > Pete > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > http://postfix.45mm.com/pipermail/sslivesteam/attachments/20110719/d58dc641/attachment.html > _______________________________________________ > SSLiveSteam mailing list > Send messages: SSLiveSteam@postfix.45mm.com > Cancel subscription: http://postfix.45mm.com/mailman/listinfo/sslivesteam > Rules: http://www.45mm.com/sslivesteam_guide.html > _______________________________________________ SSLiveSteam mailing list Send messages: SSLiveSteam@postfix.45mm.com Cancel subscription: http://postfix.45mm.com/mailman/listinfo/sslivesteam Rules: http://www.45mm.com/sslivesteam_guide.html
