i want to calculate the flame transfer function of swirl stabilized non premixed flame. I have a loud speaker at my disposal. Do i need a siren instead of a loudspeaker.
A loud speaker might be better, if it will do the intensity you need.
Hi
Have you considered using acoustic reciprocity to measure Frequency Response Functions (FRFs)?
A flame, I am sure you know, is a thermoacoustic source. It modulates the density, i.e. it causes a mass flow variation which implies that it can be seen as one (or more) acoustic monopole sources.
For structures, the relation Vibration2/Force1 = Vibration2/Force1 is well known, where numbers refer to position and direction dof.
In acoustics, we have Pressure1/VolumeAcceleration2 = Pressure2/VolumeAcceleration1. Another version for vibroacoustics is Pressure1/Force2 = Acceleration2/VolumeAcceleration1.
Acoustic volume acceleration for a loudspeaker with a rigid cabinet would be cone area times its acceleration. The speaker/flame acts as a single monopole when its dimensions is 1/10 or smaller than the shortest acoustic wavelength of interest.
A FRF measured at cold conditions would have to be scaled to mimic the FRF found at higher temperature.
I found this MSc thesis on reciprocity methods that might help.
http://iem.kug.ac.at/fileadmin/media/iem/projects/2012/bissardella.pdf
Sincerely
Claes
Hi
The concept of Flame Transfer Function is new to me. I just found this paper and had a quick look at it where the speaker is used to modulate the flow through the nozzle.
http://www.combustion-institute.it/proceedings/MCS-7/papers/CDRT/CDRT-05.pdf
It seems to me that you might be able to detect part of the information you want on the downstream side using reciprocity but, I may be off so treat the above with a grain of salt.
/C
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