Interaction between main line standing waves and side branch resonance frequencies

Abstract

Acoustic standing waves may be established in main gas delivery lines and are caused by resonance in branch lines. The branch line resonance frequency is normally determined from the geometry of the branch. Data are presented that show the branch line standing wave couples with the main line standing wave, and a range of side branch resonance frequencies are possible, with multiple frequencies existing in the side branch at the same time in some cases. This phenomenon is important to gas delivery systems where acoustic frequencies and loads must be predicted to facilitate design of the system components.

Side Branch Interaction with Main Line Standing Waves and Related Signal Handling Approaches

“…The main line has a reflective boundary at the entrance and where the rigid pipe meets the corrugated aluminum exit line; so, waves injected at the branch location are reflected at the main line ends. The acoustic behavior in the main line was explored for varying main line lengths in previous work [12]. The main line and branch acoustic amplitudes are not stationary for the majority of the system configurations that were tested.…”

“…Two initial permutations of the facility geometry were conducted at a constant main line flow velocity of 38 m/s [12], corresponding to a flow Mach number of 0.111. The position of the branch line, section 5, was varied by changing the length of pipes 1 and 6.…”

Interaction between main line standing waves and side branch resonance: stochastic signal attributes

“…The data acquisition and data handling methods reported here were developed over approximately two years of effort. Details of the facility were presented in a previous paper [7].…”

“…This paper presents data showing influence of a standing wave in the main line on the side branch pressure amplitude. A previous study using the same facility examined the frequency variation [7]. The side branch resonance amplitude varies over long times, making characterization of the system behaviour impossible unless attributes of the signal variability are included.…”