Inertia Effect of the Fluid Particles on the Lubricant Flow in a Dynamic Thrust Bearings
Closed form equations are derived from the fundamental principles for the evaluation of volume flow rate of lubricant in between the pads of a thrust bearing accounting for the centrifugal inertia effect. Two types of configuration i.e. parallel disk and nonparallel disk configurations are considered. The theoretical analysis is presented.
Flow Between a Smooth Stationary Disk and Grooved Rotating Disk
The radial outflow between a grooved rotating disk and a smooth stationary disk was examined analytically and experimentally with an emphasis on flow rate and drag moment. All investigations were conducted for a zero overall pressure differential across the disk. The analysis was based on an integral method with an area-averaged boundary condition on the grooved rotor. Nondimensionalization of the governing equations revealed that the radial inertia terms cannot in general be neglected. With the exception of the centrifugal acceleration terms, the radial inertia terms are usually neglected in this type of analysis. However, for higher flow rates these terms were found to make a significant contribution. A finite difference scheme was employed in the radial direction and a zero pressure differential across the disk was satisfied by an iterative solution technique. This technique required iteration on both the inlet flow rate to the gap and groove region until compatible flow rates in these two regions were obtained through convergence. The analytical predictions for the smooth rotor, a radially grooved rotor, and a rotor with grooves inclined at ± 20 degree to the radius are compared with experimental data generated using both air and 10 wt. motor oil as test fluids. The agreement between theory and experiment is generally good. A transition regime from laminar to turbulent flow is tentatively identified and plausibility arguments are presented to explain its existence.
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.