Thesis (PhD)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Robert A. Garrott. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 1987. / Bibliography: leaves 153-177. Also available on the World Wide Web.

Thesis (Ph. D.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: Jay J. Rotella. Includes bibliographical references.

No description available.

Doctor of Philosophy / The ancient region of Elam (southwestern Iran) has produced a significant assemblage of cylinder seals across a considerable chronological span. Unlike the glyptic material from the related and neighbouring region Mesopotamia, the Elamite cylinder seals have not previously been studied in detailed reference to one another, nor has there been an established paradigm of stylistic development articulated. This study addresses this lacuna by compiling all the published cylinder seals from Elam (as defined here, thus incorporating the historical provinces of Khuzistan, Luristan and Fars), from their earliest appearance (c.3500 BC), throughout the era of their typological dominance (over stamp seals, thus this study departs c.1000 BC). This compilation is presented in the Elamite Cylinder Seal Catalogue (Volume II), and is annotated and described through the annunciation of eighteen chronologically defined developmental styles (with another two non-chronological type classifications and four miscellaneous groups). Through the further analysis of this data, including the newly formulated and articulated styles, several facets and problems of Elamite glyptic material have been addressed (and thus the reliance upon assumed similarity in type and function with the Mesopotamian glyptic material is abandoned). These problems particularly pertain to the function of cylinder seals in Elam and the type and form of the Elamite-Mesopotamian glyptic interaction. In regards to function, a standard administrative function can be discerned, though of varying types and forms across the region and the period of study. Other, non-standard, symbolic glyptic functions can also be demonstrated in the Corpus, including the apparent proliferation of a form known as the ‘votive’ seal, perhaps a specifically Elamite form. The analysis of the style type (whether ‘Elamite’, ‘Mesopotamian Related’ or ‘Shared Elamite-Mesopotamian’), in association with their relative geographical and chronological distribution, has also enabled the discussion of the nature of Elamite-Mesopotamian glyptic interaction, and thereby the constitution of Elamite civilisation (especially in regards to Mesopotamian cultural impact and influence, and thus the testing of several previously presented paradigms [Amiet 1979a; 1979b; Miroschedji 2003]).

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.

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.

A computational study was conducted on the flow, both compressible and incompressible, in a labyrinth seal at various geometries and rotation rates. The computations were performed using the commercial software Fluent® which solves the k-ε model to predict the flow field in the seal. Various clearance-pitch ratios were used to study the effect of clearance on the flow. The aspect ratio, which is defined as the pitch-height ratio was varied to study the influence of the depth of the cavity on the flow as a whole. These studies span a range of Taylor's number that is defined accordingly, while fixing the Reynolds number at 1000. The effects of clearance, aspect ratio and rotational rates are studied using carry-over coefficient and discharge coefficient. It is observed that a secondary recirculation zone (SRZ) occurs inside a seal cavity at above certain Taylor's number. This significantly changes the flow field in the seal and the cavity which results an increases in pressure drop across the seal for a given flow boundary condition. This formation of SRZ's is more evident in incompressible flow and occur at prohibitively high rotational speeds in case of air (compressible flow). It is also observed that flow with teeth on rotor are characterized by SRZ's while it's not case with teeth on stator. A flow map which shows the onset and presence of SRZ's is shown. The ratio of tangential velocity of the shaft to the average of the swirl velocity in a cavity at various geometries of the cavities are presented. They seem to be decreasing with decreasing depth and follow a linear pattern with the aspect ratios of the cavity.

Results are presented for experimental and theoretical rotordynamic coefficients and leakage of straight smooth annular gas seals. Experimental rotordynamic coefficients were measured and trends in changes of rotordynamic coefficients with operating variables such as rotor speed, back-pressure, fluid preswirl, and seal clearance are analyzed. Experimental results show that cross-coupled stiffness coefficients are highly influenced by fluid preswirl and only moderately influenced by other operating parameters, whereas direct damping is nearly unaffected by changes in operating parameters. Effective damping, a good indicator of stability, is highly affected by fluid preswirl. Although rotordynamic coefficients of straight smooth annular gas seals are assumed to be frequency independent, experimental results suggest a frequency dependent nature at high back-pressures and high excitation frequencies. Experimental results for rotordynamic coefficients and leakage are compared with theoretical predictions of ISOTSEAL, an isothermal-flow, two-control-volume, bulk-flow rotordynamic analysis program. All rotordynamic coefficients are underpredicted. Direct stiffness is poorly predicted while cross-coupled stiffness and direct damping are predicted reasonably well. Leakage is also consistently under-predicted. Theory predicts a slight frequency dependent nature for a limited number of test configurations.