Analytical and experimental studies of flow-induced vibration of SSME components

Components of the Space Shuttle Main Engines (SSMEs) are subjected to a severe environment that includes high-temperature, high-velocity flows. Such flows represent a source of energy that can induce and sustain large-amplitude vibratory stresses and/or result in fluidelastic instabilities. Three components are already known to have experienced failures in evaluation tests as a result of flow-induced structural motion. These components include the liquid-oxygen (LOX) posts, the fuel turbine bellows shield, and the internal inlet tee splitter vane. Researchers considered the dynamic behavior of each of these components with varying degrees of effort: (1) a theoretical and experimental study of LOX post vibration excited by a fluid flow; (2) an assessment of the internal inlet tee splitter vane vibration (referred to as the 4000-Hz vibration problem); and (3) a preliminary consideration of the bellows shield problem. Efforts to resolve flow-induced vibration problems associated with the SSMEs are summarized

Analytical and experimental study of two concentric cylinders coupled by a fluid gap

From a structural point of view a liquid coolant type nuclear reactor consists of a heavy steel vessel containing the core and related mechanical components and filled with a hot fluid. This vessel is protected from the severe environment of the core by a shielding structure, the thermal liner, which is usually a relatively thin steel cylinder concentric with the reactor vessel and separated from it by a gap filled with the coolant fluid. This arrangement leads to a potential vibration problem if the fundamental frequency, or one of the higher natural vibration frequencies, of this liner system is close to the frequency of some vibration source present in the reactor vessel. The shell rigidly clamped at its base and free at the top was investigated since it is a better description of the conditions encountered in typical reactor designs

Argonne National Laboratory Reports

Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contract all of the TSPs. Noncontact results in an inactive TSP which can lead to detrimental flow induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimental quantities

Identification of root cause and abatement of vibration of monochromator.

Silicon crystal mirrors are used to reflect high-intensity X-ray beams. A large amount of heat is generated in each mirror. To minimize the effect of thermal expansion on the crystal mirrors, heat is removed by pumping liquid gallium (with a boiling point of 29.8 C) through passages in the crystal mirrors. During system operation, mirror motion should be kept to an acceptable level to avoid performance degradation. There are many potential sources of excitation to the crystal assembly; one such source is the flowing gallium. Two series of tests were performed earlier for a near-prototypical gallium cooling system (1-2). This paper describes a series of tests to measure the general vibration response characteristics of critical components in the monochromator system that contains the mirrors. The main objective of this work is to identify the root cause of vibration and to recommend general guidelines for abatement of vibration. This is achieved by performing many tests to understand the response characteristics under various conditions, by analysis of the response data, and by use of some theoretical considerations

Argonne National Laboratory Reports

Motion-dependent fluid forces acting on a tube row with a pitch-to-diameter ratio of 1.35 are measured for several flow velocities and a series of oscillation frequencies. Fluid-damping and fluid-stiffness coefficients are obtained from motion-dependent fluid forces as a function of reduced flow velocity. Fluid-force coefficients agree reasonably with published data. Based on the fluid-force coefficients, the critical flow velocity and instability characteristics of tube arrays in crossflow can be predicted

Hydroelastic response of a circular tube in eccentric annular flows

This paper presents the experimental study of the hydroelastic response of a tube located concentrically and eccentrically in a circular water-flow channel. Acceleration components in two orthogonal directions are measured at the midpoint of the test element using a pair of accelerometers. The investigation includes determination of natural frequencies, damping factors, rms displacements, and the variations of the above dynamic quantities with eccentricity and mean axial-flow velocity. The experimental data is processed into statistical forms, including power spectral density function and root-mean-square values. The results show that the natural frequency of the tube shifts as the eccentricity or flow velocity increases, that the damping in flowing water is greater than that in stationary water and increases with increasing flow velocity and eccentricity, and that the rms displacement increases as the eccentricity and/or flow velocity increases

Argonne National Laboratory Reports

Tests and analysis are made for tubes conveying fluid for two types of support conditions. The objectives are to study the characteristics of different types of instability, the transition of one instability mechanism to another, and the control of instability