The trick is to modulate the resonant frequency. (Bends won't work much differently here than they do on a Tuba!) The standing wave formed has to be disrupted. Unless a lower frequency pulsing is heard, this is not analogous to a pulse jet which has distinct regions of rarified and compressed gasses. Mark
From: [email protected] [mailto:[email protected]] On Behalf Of WJ Seidl Sent: Wednesday, February 16, 2011 4:34 AM To: Discussion of biomass pyrolysis and gasification Subject: Re: [Gasification] thermoacoutics, rijke tubes, sondhauss tubes, pulse jets-- how do we make them not work? Jim: Drill a hole. That's right, a hole. About 1/4 inch should do. Put it a few inches up on that pipe extension (from the joint you added that section to) If that doesn't solve it, put a bolt or rod in that hole, across the gas path. That should do it. If you don't care for a hole, try adding a bend at the top of the tube, say 45 degrees full diameter. The trick is to modify the modulation frequency of the gasses passing out of the pipe. But you already know that. Best, Wayne On 2/16/2011 2:11 AM, jim mason wrote: any ideas out there for how to make a pulse jet robustly not work? we're having lots of problems with thermoacoustics now that we've put a tall stack on our gasifier swirl burner. we're using a tall stack now to keep startup gasses away from the operator. the swirl burner is 5" in diameter, 10" tall. we've added a 4 foot or so stack of the same 5" diameter. it looks like this http://www.gekgasifier.com/forums/showthread.php?t=501 (though this one without the joint at 10") when run under high load, it howls rather loudly. if art, it would be fabulous. if a genset, not so good. any other ideas or experience for how to make your pulse jet not work under any circumstance? jim
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