Abstract: The time domain model for stability analysis of flow dynamics with supercritical fluid was described. With the model the dynamic behaviors of supercritical water flowing in heated pipes were studied. The mass flow fluxes versus time were given out, and the portraits of system inlet and outlet mass fluxes were plotted in the phase plane. The stability characteristics of system when the logarithmic decay ratios (LDRs) are very close to zero were checked out, and the results show that the system has stable limit cycles with nearzero LDRs. Through transient simulations with jumping heating powers the stability oscillations of system of high outlet enthalpies were observed. The frequency domain analysis and time domain analysis are consistent with each other. However, the latter method can provide better analysis of the nonlinear characteristics of fluid flow.

Key words:  time domain model, flow stability, supercritical