FREE GAS PULSATIONS IN ACOUSTIC SYSTEMS COMPOSED OF 2 THIN, CURVED ORFLAT, 2-DIMENSIONAL GAS CAVITIES WHICH SHARE A COMMON OPEN BOUNDARY

A general procedure for the analysis of thin, curved gas cavities has been developed by the authors [1, 2], valid for cases where the thickn ess of the cavity is small compared to the shortest wavelength of inte rest. Also, the analysis of gas pulsations in multi-cylinder compresso r manifolds was demonstrated by the authors [3] as a practical applica tion example. In this study, a line impedance method is proposed for t he analysis of composite acoustic systems which consist of two differe nt thin gas cavities which share a common line-like boundary. Line imp edances are formulated, in analogy to line receptances in structural a nalysis, from the pressure responses of thin, curved or flat cavities to a line volume flow rate inputs which are distributed harmonically a long the interface of the two subsystems. The composite system frequen cy equation is derived and then solved for the natural frequencies and mode shapes of the combined acoustic system. Several cases including two rectangular boxes joined together, two cylindrical thin cavities j oined together and a circular disk box attached to a cylindrical cavit y, which represents a model for a refrigeration compressor manifold, a re investigated. Certain results obtained from the line impedance meth od and finite element method calculations are compared and show satisf actory agreement. (C) 1996 Academic Press Limited