State Variables and Pseudo Bond Graphs for Compressible Thermofluid Systems

Abstract

Bond graphs aid in the creation of lumped parameter models for a wide variety of physical and biological systems but have proved less useful when it is desired to use control volume methods and a variable amount of matter is enclosed by the volume. In the present paper, a class of pseudo bond graphs is presented which handles control volume problems in a natural way and which retains most of the advantages of true bond graphs. The effort and flow variables do not, however, represent complementary power variables and thus many of the multiport element constitutive laws do not obey symmetry conditions based upon stored energy state functions. On the other hand, the general structure of the model is quite clearly shown and the causality of component interactions can be compactly and clearly shown just as in true bond graphs.