dynamic stability, Lyapunov Stability Theorem, stability margin, refrigeration system
The stable operation of a system is restricted by the intrinsic characteristics, namely harmonious matching among and between structure parameters and operation parameters. In this paper, we put forward an analysis method of the dynamic stability of the refrigeration system based on the First Approximation Theory of Lyapunov Stability Theorem and the evaluation of stability margin. It is carried out by linearizing the governing equations and analyzing the eigenvalue form of coefficient matrix. And the minimum logarithmic decrement is calculated to represent the stability margin. Analyzing the stability of gas cooler confirms the consistency between the mathematical stability and the actual dynamic one. The proposed method is performed in a transcritical CO2 ejector expansion refrigeration system (EERS) to analyze the system dynamic stability. The present results show that, even each component of the system is in the stable state, it cannot guarantee the dynamic stability of the whole system. Moreover, the effect of state parameter on system dynamic stability is investigated. The work supplies a guiding principle on system control and may be extended in more general thermodynamic cycle.