Linear model of a closed three-shaft Brayton cycle

Abstract

A linear model of a closed three-shaft Brayton cycle at normal power operation is developed. The model is intended to give an understanding of the dominant dynamic behaviour in a nuclear power system that utilizes a closed three-shaft Brayton cycle. The insights gained from the model can be used for system design as well as for the design of control algorithms. A conceptual linear model is constructed and it is explained how this model can be developed starting with the models of the turbines and compressors followed by models of the shafts and the volumes inside the circuit to finally obtain the linear state space equations. A time domain comparison is made between the linear system model and the responses predicted by the thermal-fluid analysis software program, Flownet.