Nonlinear dynamic behavior of a water-lubricated hybrid bearing-rotor system
In this study, the stability analysis is carried out on a water-lubricated hybrid bearings used as the support of a high-speed motorized spindle. A two-dimension finite element method considering turbulence effect has been developed to solve the nonlinear oil film force. This paper mainly studies the influence of the water supply pressure, rotating speed, and unbalance mass on the axis orbit of the rotor-bearing system. The results of the axis orbit indicate that the effect of nonlinear for the hybrid bearing studied in this paper is not obvious, and the bearing-rotor system can run safely and stably at the rotating speed not more than 30000 rpm.
Investigation of recessed hydrostatic and slot-entry journal bearings for hybrid hydrodynamic and hydrostatic operation☆
Abstract Results of investigations into recessed hydrostatic bearings and slotentry hydrostatic bearings are presented. Initial comparative results show that there are certain conditions under which slot-entry bearings may have marked advantages. Results are given for such parameters as load, torque and flow rate under hydrostatic ( i.e. zero speed) conditions and also under hybrid hydrodynamic/hydrostatic operating conditions.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.