Engine High-pressure Oxidizer Turbopump Research Articles

Thermohydrodynamic analysis of fluid film bearings for cryogenic applications

A thermohydrodynamic analysis and computer program for prediction of the static and dynamic force response of hydrostatic journal bearings, annular seals, or damping bearings, and fixed arc-pad bearings are presented. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility, and thermal effects. Numerical results detail a comparison of the static performance and dynamic force coefficients for a six-recess hydrostatic bearing and a damping bearingseal for the Space Shuttle Main Engine high-pressure oxidizer turbopump. The calculations indicate that turbulent-flow, externally pressurized bearings support the expected loads with moderate journal center eccentricities and with force coefficients of relevant magnitude for this critical application.

Turbomachinery unsteady load predictions with nonuniform inflow

A two-dimensional frequency domain source-doublet based potential paneling formulation is developed to predict steady and unsteady turbomachinery blade loadings. The method employed blade-to-blade periodic boundary condition and interblade phase angles to simulate the complex blade-wake interactions in turbomachinery stages. The method is used in the present paper to simulate the unsteady response on Space Shuttle main engine high-pressure oxidizer turbopump diffuser blades. The amplitude of unsteady pressure and the wave propagation characteristics are discussed by comparing similar studies.

An analysis of pump cavitation damage

The cavitation assessment for the space shuttle main engine high pressure oxidizer turbopump is documented. A model of the flow through the pump was developed. Initially, a computational procedure was used to analyze the flow through the inlet casing including the prediction of wakes downstream of the casing vanes. From these flow calculations, cavitation patterns on the inducer blades were approximated and the damage rate estimated. The model correlates the heavy damage on the housing and over the inducer with unsteady blade surface cavitation. The unsteady blade surface cavitation is due to the large incidence changes caused by the wakes of the upstream vanes. Very high cavitation damage rates are associated with this type of cavitation. Design recommendations for reducing the unsteady cavitation include removing the set of vanes closest to the inducer and modifying the remaining vanes.

Rotordynamic Coefficients for Compressible Flow in Tapered Annular Seals

Derivation of the governing equations for compressible flow in a tapered annular seal is based on Hirs’ turbulent bulk-flow model. Zeroth and first-order perturbation equations are developed by an expansion in the eccentricity ratio. These equations are numerically integrated to obtain the leakage, and the direct and cross-coupled stiffness and damping coefficients. Seal parameters similar to the Space Shuttle Main Engine High Pressure Oxidizer Turbopump are used to demonstrate output from the analysis procedure. The effects of preswirl and seal taper are shown for three different length-to-diameter ratios. Generally the results indicate that prerotating the fluid significantly increases the cross-coupled stiffness but has little effect on the other coefficients, and increasing the convergent taper increases the direct stiffness while decreasing the direct damping and cross-coupled stiffness.