The present work describes experiments conducted on several pocket damper seal (PDS) designs using a high pressure annular gas seal test rig. Both rotating and non-rotating tests were conducted for a 12, 8, and 6 bladed PDS. The objective of the tests was to determine the rotordynamic force coefficients and leakage for the different PDS while varying parameters such as: (1) clearance ratio, (2) rotor surface speed, (3) PDS pressure differential, and (4) excitation frequency. Two different methods were used to determine frequency dependent force coefficients: (1) the impedance method, which involved using a baseline subtraction and (2) the dynamic pressure response method, which comprised of measuring seal cavity dynamic pressure and phase relationship to vibration. Both methods were used to determine coefficients, but the dynamic pressure response method revealed insights to the dynamics of the PDS that were the first of its kind and allowed the comparison to the damper seal theory at the most fundamental of levels. The results indicated that the conventional PDS possessed high positive damping, negative and positive stiffness, and same sign cross-coupled coefficients. Another objective of the work is to investigate a new fully partitioned PDS design and accompany experimental results with the development of a modified damper seal theory. The new fully partitioned PDS design was shown to give twice as much damping as the conventional design and revealed the ability to modify direct stiffness without degradation in direct damping. Finally, both the conventional theory and the newly proposed theory predictions are compared to experimentally determined force coefficients. The last objective was to evaluate the leakage characteristics of the different designs and to investigate the effect of blade profile on seal leakage. Results showed that beveled tooth blade profiles yield higher mass flow leakage compared to rectangular blade profiles.

Instantaneous wall-pressure data were recorded for a 25% eccentric whirling annular seal for rotor speeds of 1800RPM and 3600RPM, axial Reynolds numbers of 24000 and 12000, and whirl ratios of 0.1-1.0 following the procedure set forth by Winslow (1994), Robic (1999) and Suryanarayanan (2003). Overall, the phase averaged wall-pressure distributions were consistent with previous results. The “switch” in the pressure distribution measured by Suryanarayanan (2003) and Robic (1999) from pressure to suction between the seal entrance and exit occurs at and above a whirl ratio of 0.7 for 1800RPM and 0.4 for 3600RPM. For both rotor speeds, decreasing the flow rate by one-half also decreases the wall pressure fluctuation distributions by one-half. For whirl ratios less than 0.5, the phase averaged pressure field was relatively constant which leads to minimal forces being imparted on the rotor by the fluid in the annulus. Talyor-Gortler vortices are measured for 1800RPM and Re=24000 at whirl ratios 0.1 and 0.3-0.7. As the whirl ratio increases past 0.5, longitudinal vortices begin to emerge in the pressure contours and skew axially with 180° shifts occurring when the Taylor-Reynolds ratio is large enough. Longitudinal vortices were measured for both rotor speeds when the whirling motion is greater than 1400RPM for Re=12000 and greater than 1600RPM for Re=24000. Attempts were made to apply Childs (1983) procedure for finding the rotordynamic coefficients of annular seals; however, the seal moves in a non-circular orbit about the seal’s center so Childs analysis cannot be applied.

Non-contacting annular seals are internal sealing devices used in rotating machinery, such as multistage centrifugal pumps and compressors. Their design affects both efficiency and rotor stability. Traditional plain and labyrinth seals are being replaced with stators containing different roughness patterns to reduce leakage and enhance rotor response. Several roughened seal experiments with liquid and air have produced leakage data indicating that the friction factor increases as the seal clearance is increased. Simplified models based on bulk flow theory and Moody’s approach to characterize wall friction in pipes cannot explain this outcome. This research is an extension of a 2-D numerical analysis of flat plate experiments with water which found that friction factor of these surfaces is governed by the roughness’ ability to develop high static pressures. An exhaustive 3-D numerical analysis of several experiments with liquid annular seals has been performed using a CFD code. Direct numerical simulations (DNS) of turbulent channel flow and smooth seals were replicated within 1% using Reynolds-averaged Navier-Stokes (RANS) equations and turbulence modeling. Similarly, measured groove seal leakage rates were reproduced within 2%. On the other hand, no turbulence model combination predicts the leakage in most 3-D pattern roughened seals with the same accuracy. Present results reproduce the friction factor ‘plateau’ behavior predicted with the 2-D analysis and observed in the flat plate experiments. They also reproduce the friction-factor-to-clearance indifference behavior, the maximum friction factor observed in a specific roughness pattern size is independent of the actual clearance in a certain Reynolds number range, but clarify the role of the roughness length-to-clearance ratio and the actual roughness size in defining the friction-factor-toclearance proportionality. All simulations indicate that roughened surface area and roughness aspect ratios are the parameters defining the friction factor at a given seal clearance. The roughness pattern size, relevant in determining the friction-factor-to-clearance proportionality, plays a moderate role once the above cited ratios are defined. In any shape and size, shallow patterns are predicted and observed to provide larger friction factors than deep patterns. Predictions also confirm limited experimental data showing that friction factor is affected by the mean flow orientation relative to the roughness pattern. Solving RANS equations is sufficient to model simple seal geometries but might not be enough to replicate turbulent flow in liquid annular seals with roughened surfaces.

A rotordynamic analysis of hole-pattern gas annular seals using a two-control-volume model, Ha and Childs and frequency dependent transfer-function model, Kleynhans and Childs is modified with four features. The energy equation is added, and real gas properties are used instead of the ideal gas equation of state. The depth of the hole-pattern is made variable with the axial distance along the seal. And last, the addition of deep grooves to hole-pattern seals is analyzed, and the code’s predictions for the influence of a groove are compared with test data.

This dissertation discusses research on the leakage and rotordynamic characteristics of pocket damper seals (PDS) and see-through labyrinth seals, presents and evaluates models for labyrinth seal and PDS leakage and PDS force coefficients, and compares these seals to other annular gas seals. Low-pressure experimental results are used alongside previously-published high-pressure labyrinth and PDS data to evaluate the models. Effects of major seal design parameters; blade thickness, blade spacing, blade profile, and cavity depth; on seal leakage, as well as the effect of operating a seal in an off-center position, are examined through a series of non-rotating tests. Two reconfigurable seal designs were used, which enabled testing labyrinth seals and PDS with two to six blades. Leakage and pressure measurements were made with air as the working fluid on twenty-two seal configurations. Increasing seal blade thickness reduced leakage by the largest amount. Blade profile results were more equivocal, indicating that both profile and thickness affected leakage, but that the influence of one factor partially negated the influence of the other. Seal leakage increased with increased eccentricity at lower supply pressures, but that this effect was attenuated for higher pressure drops. While cavity depth effects were minor, reducing depths reduced leakage up to a point beyond which leakage increased, indicating that an optimum cavity depth existed. Changing blade spacing produced results almost as significant as those for blade thickness, showing that reducing spacing can detrimentally affect leakage to the point of negating the benefit of inserting additional blades. Tests to determine the effect of PDS partition walls showed that they reduce axial leakage. The pressure drop was found to be highest across the first blade of a seal for low pressure drops, but the pressure drop distribution became parabolic for high pressure drops with the largest drop across the last blade. Thirteen leakage equations made up of a base equations, a flow factor, and a kinetic energy carryover factor were examined. The importance of the carryover coefficient was made evident and a modified carryover coefficient is suggested. Existing fullypartitioned PDS models were expanded to accommodate seals of various geometries.

Thesis (Ph. D.)--University of Chicago, Dept. of Near Eastern Languages and Civilizations, June 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph.D.)--University of Melbourne, Dept. of Zoololgy, 2009. / Typescript. Includes bibliographical references.

VHF radio-telemetry was used to study individual and seasonal variation in common seal haul-out behaviour in a study area in Orkney, Scotland. The timing of the annual cycle was also described and seasonal changes in behaviour, distribution and abundance were related to the constraints of breeding and the moult. There were consistent seasonal trends in site-use, with some sites being used during the breeding season, and others during the winter. Sex differences in site-use also occurred during the summer, with mothers and pups being seen regularly at some sites, and males predominating at others. A high degree of individual, sex-related and seasonal variation in haul-out behaviour was found. In general, seals spent most time in inshore waters, and hauled out frequently, during the summer. For males, this was especially marked during the moult, whereas females came ashore most regularly during the pupping period. Outside the breeding season, seals left the study area for longer periods, of several days, but regularly returned between trips to haul out. These longer winter trips are believed to represent periods of more intense feeding activity, and it is suggested that the constraints of breeding and the moult restrict seals to shorter feeding trips during the summer. Changes in haul-out behaviour during the moult resulted in common seals being most abundant on land in August. Behaviour was also less variable during the moult, and it is suggested that population surveys should be made at this time of year. An aerial survey was made over Orkney in August 1985 and, in conjunction with telemetric data on haul-out frequency, the results were used to produce a preliminary estimate of the size of the population in this area.

Seals-of-approval have been employed as one of the information sources at the time of purchase. However, little is known about how seals’ sponsoring organizations affect consumers’ decision making and how consumers use seals in different food categories such as healthy-seeming vs. unhealthy-seeming products. Applying Consumers’ Decision Making Model and Signaling Theory to the above inquiry, I propose that people who are exposed to healthy-seeming food products are using seals-of-approval to evaluate brand quality and credible third-party seals may significantly affect their brand attitude and buying decision. In contrast, the seals-of-approval on unhealthy-seeming food products may not affect significantly consumers’ brand attitude or buying intention because consumers rely more on their previous experience such as taste when choosing unhealthy foods. After this theoretical proposition, next step will be an experimental survey to test suggested hypotheses. / text

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