Joseph K. Scharrer

A Study of the Transient Performance of Hydrostatic Journal Bearings: Part I-Test Apparatus and Facility

A test apparatus was developed to study the transient performance of hydrostatic journal bearings operating in liquid nitrogen. The objective of the test program was to determine the number of revolutions of shaft contact before liftoff and after touchdown as a function of bearing/shaft material combinations and operating conditions. The results show that bearing liftoff occurs quickly in most cases. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in St. Louis, Missouri, October 14–16, 1991

Rotordynamic coefficients of multistepped annular seals

The basic equations are derived for incompressible flow in multi-stepped annual seals. A 2-D CFD solution is used to verify the model. Exit and entrance loss factors substituted into the bulk flow solution for pressures in the cavity match the 2-D CFD solution. The flow is assumed to be completely turbulent in the axial and circumferential directions with no separation and is modeled using Moodys friction factor relationship. Linearized zeroth- and first-order perturbation equations are developed for small motion about an arbitrary position by an expansion in the eccentricity ratio. The zeroth-order continuity and momentum equations are integrated, yielding the axial and circumferential velocity components and the pressure distribution. The first-order equations are integrated to satisfy the boundary conditions and yield the perturbation pressure distribution. This resultant pressure distribution is integrated along and around the seal to yield the force developed by the seal and the corresponding dynami...

Rotordynamic Coefficients for Partially Roughened Annular Gas Seals

The basic equations are derived for compressible flow in an annular seal with partially roughened surfaces. The flow is assumed to be completely turbulent in the axial and circumferential directions with no separation, and is modeled by Moody’s equation for roughness. Linearized zeroth and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. The zeroth-order continuity and momentum equations are solved exactly, yielding the axial and circumferential velocity components and the pressure distribution. The first-order equations are reduced to three ordinary, complex, differential equations in the axial coordinate Z. The equations are integrated to satisfy the boundary conditions and yield the perturbation pressure distribution. This resultant pressure distribution is integrated along and around the seal to yield the force developed by the seal and the corresponding dynamic coefficients.Since no test data exist for this type of seal, the results of a parametric study on the effect of the rough length/smooth length ratio on the seal leakage and rotordynamic coefficients is presented.Copyright