Surge prediction in industrial compressors

The stability limit of industrial compressors is strongly influenced by the dynamics of the surrounding process and the individual slopes of the stage characteristics. Most common stall criterions which are also used as surge criterions do not take this into account. In order to include the system dynamics and the individual slopes of the stage characteristics into the surge line prediction, the TOLDYM-method was developed. TOLDYM stands for Two Variable, One Dimensional, Linearized Dynamic Model. The real system is represented by a mathematical model. If the model is stable the real system is assumed to be stable too. Three simplifications (1-dimensional, linearized, constant temperature) are made in order to reduce model complexity. A set of model element types is available for the assembling of a model. The mathematical representation of the model elements and of the entire model are transfer matrices. The test of stability is performed by checking the real part of the eigenvalues of the transfer function. Three examples show that the results of this method are in agreement with measurements.