Experiments conducted at the Texas A&M Turbomachinery Laboratory and field applications have shown that pocket damper seals (PDS) can be used to suppress vibrations in compressors. A mathematical model is presented for the notched PDS. The notch is a prominent feature in all the PDS manufactured in recent times. The notch is provided at the exit blades of the PDS to act as a diverging clearance, which is one of the conditions for the damper seal to perform satisfactorily The model to be presented has been adapted from a theory previously developed to predict the direct stiffness and damping coefficients. The flow equations are numerically solved and a computer program is developed correspondingly. The predictions from this notched model are compared with the existing model to highlight the effect of the notch in the analysis. These predictions correlate well with the experimental results from the notched PDS. Also experimental results from testing of a two bladed PDS are compared to the code predictions thus validating the notched model. The notched model performs satisfactorily to predict the direct damping coefficients. Coastdown tests are conducted on a four bladed eight pocket PDS with a partial arc notch of large radius across the exit blades. The PDS offers positive direct damping which increases with an increase in seal inlet pressure. The low stiffness of the test rig combined with the negative stiffness of the seal made it impracticable to conduct testing above inlet pressures of 64.7 psia (4.461 bar). The existing theoretical models are compared with the experimental data collected up to 64.7 psia (4.461 bar).

Indices of nutritional condition and diet were evaluated in harp seals Phoca groenlandica obtained from hunters in Hudson Strait and the Gulf of St. Lawrence, December 1988 to October 1990. In winter seals, blubber and the lean, eviscerated carcass contributed 90% and 9% of total body lipids, respectively. Lipid was distributed homogeneously throughout the blubber. Blubber thickness and girth at 50% of length showed the strongest correlation to fat stores. Sculp and core mass in females increased from autumn to winter. Mature males were observed to significantly increase their blubber mass from early to late winter. Muscle and liver lipid content varied seasonally in both sexes, and were highest in a sample of females one month post-partum which were feeding very intensively. These females had reduced blubber mass and blubber lipid content, but the highest observed core mass, the later being significantly heavier than in autumn. Changes in nutritional condition reflect seasonal variation in feeding intensity.

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Precision of determining age in ringed seals (Phoca hispida) was examined by repeated readings of undecalcified cross sections and decalcified stained longitudinal sections of mandibular canines. There appeared to be geographical differences in repeatability although this could not be tested statistically. There was no difference in repeatability between cross and stained sections. / The effect of precision on population parameters was examined. Smoothing procedures necessary to construct life tables and to do Leslie matrix calculations obscured any differences in ages between readings. Variance between readings was found to give inconsistent notions of sexual maturity. Imprecision caused little overall difference in growth curves. / Without known age animals, accuracy cannot be evaluated directly. High correlation between ages from canines from different sides of the same animal, between dentine and cementum of teeth from the same animal, and between readers examining the same sets of teeth gave an indirect suggestion of accuracy.

Seals are basic mechanical devices commonly used in machinery to avoid undesired flow losses of working fluids. To understand the working of these seals specifically those placed between relatively moving parts is still one of the major engineering challenges for the scientific community. Particularly Annular seals are one of the most widely used in rotating machinery comprising turbines, compressors and pumps. They are mounted on the shaft that rotates within a stationary case. These seal designs make an impact on (i) machinery energy conversion efficiency and (ii) rotor dynamic stability due to the interaction between rotor and stator through fluid flow leakage. Among all annular seals straight through rectangular labyrinth seals are the most commonly used ones. Their designs have not changed much a lot since its inception by C.J. Parsons [1] back in 1901. These seals provide resistance to the fluid flow through tortuous path comprising of series of cavities and clearances. The sharp tooth converts the pressure energy to the kinetic which is dissipated through turbulence viscosity interaction in the cavity. To understand the accurate amount of leakage the flow is modeled using the discharge coefficient and for each tooth and the kinetic energy carry over coefficients. This research work is aimed at understanding the fluid flow though labyrinth seals with tooth mounted on the rotor. A matrix of fluid flow simulations has been carried out using commercially available CFD software Fluent® where all parameters effecting the flow field has been studied to understand their effect on the coefficients defining the seal losses. Also the rotor surface speed has been used varied in a step by step manner to understand the fluid flow behavior in high speed turbo-machinery. The carry over coefficient is found to be the function of all the geometric elements defining the labyrinth tooth configuration. A relation between the flow parameters and the carry over coefficient has also been established. The discharge coefficient of the first tooth has been found to be lower and varying in a different manner as compared to a tooth from a multiple cavity seal. Its dependence upon flow parameters and dimensionless geometric constants has been established. The discharge coefficient of the first teeth is found to be increasing with increasing tooth width. Further the compressibility factor has been defined to incorporate the deviation of the performance of seals with compressible fluid to that with the incompressible flow. Its dependence upon pressure ratio and shaft speed has also been established. Using all the above the mentioned relations it would be easy decide upon the tooth configuration for a given rotating machinery or understand the behavior of the seal currently in use.

Thesis (Ph.D.) - University of St Andrews, September 2008.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 82-95). Also available on microfiche.

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