Download or read book Leakage and Rotordynamic Effects of Pocket Damper Seals and See through Labyrinth Seals written by Ahmed Mohamed Gamal Eldin and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 fully partitioned PDS models were expanded to accommodate seals of various geometries.

Download or read book Rotordynamic Effects of Pocket Damper Seals written by Hector Emilio Laos and published by . This book was released on 1999 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of a Slanted tooth See through Labyrinth Seal to a Straight tooth See through Labyrinth Seal for Rotordynamic Coefficients and Leakage written by Naitik Mehta and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This research compares the leakage and rotordynamic characteristics of a slanted-tooth labyrinth seal to a conventional straight-tooth labyrinth. Detailed results comparing the rotordynamic coefficients and leakage parameters of a slanted-tooth see-through labyrinth seal and a straight-tooth see-through labyrinth seal are presented. The straight-tooth labyrinth seal used in this research was originally tested by Arthur Picardo. The slanted-tooth labyrinth seal was designed and fabricated to be identical to the straight-tooth labyrinth seal in terms of pitch, depth, and the number of teeth. The angle of inclination of the teeth in the slanted-tooth labyrinth seal was chosen to be 65° from the normal axis. The seals were tested at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10,200, 15,350, and 20,200 rpm, and a radial clearance of 0.2 mm (8 mils). The experiments were carried out at zero, medium, and high inlet preswirl ratios. The experimental results show only minute differences in the rotordynamic coefficients between the two seals. But, the slanted-tooth labyrinth seal leaked approximately 10% less than the straight-tooth labyrinth seal. A study of prediction versus experimental data was done. XLlaby was used for prediction. XLlaby was developed for a straight-tooth labyrinth seal design and did not do a good job in predicting the rotordynamic coefficients and the leakage rate.

Download or read book Labyrinth Seal Leakage Analysis written by Gaurav Chaudhary and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Rotordynamic Force Coefficients of Pocket Damper Seals written by Bugra Han Ertas and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Labyrinth Seal Leakage Analysis written by Orcun Inam and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Annular seals are devices used in turbomachinery to avoid flow losses which reduce efficiency. The dynamic stability of the machine is also improved by the seal. Thus, it is an important subject to understand the flow behavior through the seal. Straight through triangular labyrinth seals are one of the most commonly used types of non-contacting annular seals. The energy dissipation through these seals is achieved by a series of teeth and cavities. As the flow passes above each tooth, a portion of its pressure energy is converted into kinetic energy. A portion of this kinetic energy is dissipated through turbulence-viscosity interaction in the cavity that follows. Moreover, some portion of the pressure energy is also lost through viscosity of the fluid. This research aims to understand the effects of flow parameters and seal geometry on these losses. This will make it possible to estimate the mass flow leakage through the seal. ANSYS Fluent is used to simulate the flow through the seal. The effect of seal geometry is studied by varying clearance, pitch, tooth height, tooth width and upstream side angle. It was found that, amongst other geometrical parameters, tooth clearance and pitch has a strong influence on carryover coefficient. Smaller values of c/s have better kinetic energy dissipation in the cavity. Carryover coefficient is also found to be a function of the Reynolds number and shaft speed. Discharge coefficient of the seal presents the overall efficiency while carryover coefficient only shows the cavity performance. Discharge coefficient is also found to be a strong function of tooth clearance, pitch, Reynolds number and shaft speed. Remaining parameters have smaller effects. It was observed that the discharge coefficient of first tooth is always lower than those of intermediate teeth. The compressibility effects are presented by using an expansion factor which is the ratio of compressible flow discharge coefficient to incompressible flow discharge coefficient. It was found that the expansion factor is fairly independent of geometrical parameters but a strong function of flow parameters. Considering the effects of seal geometry and flow parameters on carryover coefficient, discharge coefficient and expansion factor, the seal geometry is optimized to increase the kinetic energy dissipation and pressure head loss which in turn will reduce the mass flow leakage.

Download or read book Vexillum fratrum religiosorum Divae Virginis de Monte Carmelo written by and published by . This book was released on 1506 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of Experimental and Ideal Leakage Flows Through Labyrinth Seals for Very Small Pressure Differences written by and published by . This book was released on 1970 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Compressible and Incompressible Flows Through See through Labyrinth Seals written by Jeng Won Woo and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The labyrinth seal is a non-contact annular type sealing device used to reduce the internal leakage of the working fluid which is caused by the pressure difference between each stage in a turbomachine. Reducing the leakage mass flow rate of the working fluid through the labyrinth seal is desirable because it improves the efficiency of the turbomachine. The carry-over coefficient, based on the divergence angle of the jet, changed with flow parameters with fixed seal geometry while earlier models expressed the carry-over coefficient solely as a function of seal geometry. For both compressible and incompressible flows, the Reynolds number based on clearance was the only flow parameter which could influence the carry-over coefficient. In the case of incompressible flow based on the simulations for various seal geometries and operating conditions, for a given Reynolds number, the carry-over coefficient strongly depended on radial clearance to tooth width ratio. Moreover, in general, the lower the Reynolds number, the larger is the divergence angle of the jet and this results in a smaller carry-over coefficient at lower Reynolds numbers. However, during transition from laminar to turbulent, the carry-over coefficient reduced initially and once the Reynolds number attained a critical value, the carry-over coefficient increased again. In the case of compressible flow, the carry-over coefficient had been slightly increased if radial clearance to tooth width ratio and radial clearance to tooth pitch ratio were increased. Further, the carry-over coefficient did not considerably change if only radial clearance to tooth width ratio was decreased. The discharge coefficient for compressible and incompressible flows depended only on the Reynolds number based on clearance. The discharge coefficient of the tooth in a single cavity labyrinth seal was equivalent to that in a multiple tooth labyrinth seal indicating that flow downstream had negligible effect on the discharge coefficient. In particular, for compressible fluid under certain flow and seal geometric conditions, the discharge coefficient did not increase with an increase in the Reynolds number. It was correlated to the pressure ratio, Pr. Moreover, it was also related to the fact that the flow of the fluid through the constriction became compressible and the flow eventually became choked. At low pressure ratios (less than 0.7), Saikishan's incompressible model deviated from CFD simulation results. Hence, the effects of compressibility became significant and both the carry-over coefficient compressibility factor and the discharge coefficient compressibility factor needed to be considered and included into the leakage model. The carry-over coefficient compressibility factor, phi, had two linear relationships with positive and negative slopes regarding the pressure ratios. This result was not associated with the seal geometry because the seal geometry ratios for each instance were located within the nearly same ranges. Further, the phi-Pr relationship was independent of the number of teeth regardless of single and multiple cavity labyrinth seals. The discharge coefficient compressibility factor, psi, was a linear relationship with pressure ratios across the tooth as Saikishan predicted. However, in certain flow and seal geometric conditions, Saikishan's model needed to be modified for the deviation appearing when the pressure ratios were decreased. Hence, a modified psi-Pr relationship including Saikishan's model was presented in order to compensate for the deviation between the simulations and his model.

Download or read book The Effect of Land Wear Upon Flow Leakage Through Labyrinth Seals written by David Rex Ek and published by . This book was released on 1984 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbomachinery Fluid Dynamics and Heat Transfer written by Hah and published by CRC Press. This book was released on 1997-02-04 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This festschrift in honor of Professor Budugur Lakshminarayana's 60th birthday-based on the proceedings of a symposium on Turbomachinery Fluid Dynamics and Heat Transfer held recently at The Pennsylvania State University, University Park-provides authoritative and conclusive research results as well as new insights into complex flow features found in the turbomachinery used for propulsion, power, and industrial applications. Explaining in detail compressors, heat transfer fields in turbines, computational fluid dynamics, and unsteady flows, Turbomachinery Fluid Dynamics and Heat Transfer covers: Mixing mechanisms, annulus wall boundary layers, and the flow field in transonic turbocompressors The numerical implementation of turbulence models in a computer code Secondary flows, film cooling, and thermal turbulence modeling The visualization method of modeling using liquid crystals Innovative techniques in the computational modeling of compressor and turbine flows measurement in unsteady flows as well as axial flows and compressor noise generation And much more Generously illustrated and containing key bibliographic citations, Turbomachinery Fluid Dynamics and Heat Transfer is an indispensable resource for mechanical, design, aerospace, marine, manufacturing, materials, industrial, and reliability engineers; and upper-level undergraduate and graduate students in these disciplines.

Download or read book Labyrinth Seal Leakage Equation written by Saikishan Suryanarayanan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A seal is a component used in a turbomachine to reduce internal leakage of the working fluid and to increase the machine's efficiency. The stability of a turbomachine partially depends upon the rotodynamic coefficients of the seal. The integral control volume based rotodynamic coefficient prediction programs are no more accurate than the accuracy of the leakage mass flow rate estimation. Thus an accurate prediction of the mass flow rate through seals is extremely important, especially for rotodynamic analysis of turbomachinery. For labyrinth seals, which are widely used, the energy dissipation is achieved by a series of constrictions and cavities. When the fluid flows through the constriction (under each tooth), a part of the pressure head is converted into kinetic energy, which is dissipated through small scale turbulence-viscosity interaction in the cavity that follows. Therefore, a leakage flow rate prediction equation can be developed by comparing the seal to a series of orifices and cavities. Using this analogy, the mass flow rate is modeled as a function of the flow coefficient under each tooth and the carry over coefficient, which accounts for the turbulent dissipation of kinetic energy in a cavity. This work, based upon FLUENT CFD simulations, initially studies the influence of flow parameters, in addition to geometry, on the carry over coefficient of a cavity, developing a better model for the same. It is found that the Reynolds number and clearance to pitch ratios have a major influence and tooth width has a secondary influence on the carry over coefficient and models for the same were developed for a generic rectangular tooth on stator labyrinth seal. The discharge coefficient of the labyrinth seal tooth (with the preceding cavity) was found to be a function of the discharge coefficient of a single tooth (with no preceding cavity) and the carry over coefficient. The discharge coefficient of a single tooth is established as a function of the Reynolds number and width to clearance ratio of the tooth and a model for the same is developed. It is also verified that this model describes the discharge coefficient of the first tooth in the labyrinth seal. By comparing the coefficients of discharge of compressible flow to that of incompressible flow at the same Reynolds number, the expansion factor was found to depend only upon the pressure ratio and ratio of specific heats. A model for the same was developed. Thus using the developed models, it is possible to compute the leakage mass flow rate as well as the axial distribution of cavity pressure across the seal for known inlet and exit pressures. The model is validated against prior experimental data.

Download or read book Investigation of the Performance of Labyrinth Seals for Centrifugal Compressor Applications written by Casey Palanca and published by . This book was released on 2022 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Labyrinth seals were one of the first seal configurations used in modern turbomachinery and, due to their robust qualities and relatively low-cost productions, remain one of the most widely used seal configurations today. Their primary purpose is to control internal leakage between the rotating and stationary components of rotating machinery, including the centrifugal compressor. A reduction in secondary leakage flow will always be accompanied by an increase in efficiency. However, while fulfilling the objective of restricting secondary fluid flow, labyrinth seals have been known to cause adverse stability effects on the rotor. Driving forces inside the cavities from the circumferential flow path have been known to be a potential source of destabilizing vibrations. Therefore, accurately predicting these forces is a primary interest in compressor design. These forces are characterized by stiffness and damping coefficients.The present study utilizes the growing advances in CFD to understand, model, and predict the aerodynamic and rotordynamic performance of labyrinth seals. The scope of this work progresses from a well-established steady state CFD method to a more novel transient CFD approach. The benefits and disadvantages of each method are evaluated and discussed by comparing accuracy, reliability, and computational efficiency. Each method is validated with experimental data. Additionally, the proposed transient CFD method can be used to perform a reasonably accurate prediction of the frequency-dependent rotordynamic coefficients by using a Fast Fourier Transform analysis on the monitored force response and displacement data.Lastly, the transient CFD approach is expanded upon by investigating the flow characteristics of long 18 tooth on rotor balance piston labyrinth seal modeled with abradable grooves on the stator. It was discovered that the creation of abradable grooves on the stator can cause the vortex between the labyrinth teeth to change directions (clockwise to counterclockwise). This observation is used to determine the relationship between the flow pattern and rotordynamic performance. A parametric study shows the effect of abradable groove geometries and operating flow conditions on the labyrinth seal rotordynamic coefficients.

Download or read book Rotordynamic and Leakage Characteristics of a 4 Stage Brush Seal written by and published by . This book was released on 1992 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental results are presented for the direct and cross-coupled stiffness and damping coefficients as well as the leakage performance for a 4- stage brush seal. Variable test parameters include the inlet pressure, pressure ratio, shaft speed, fluid prerotation, and seal spacing. Direct damping is shown to increase with running speed; otherwise, the rotordynamic coefficients are relatively insensitive to changes in the test parameters. Cross-coupled stiffness is generally unchanged by increasing the inlet tangential velocity to the seals, suggesting that the brush seal is not affected by inlet swirl. Direct stiffness is shown to increase with frequency; however, the magnitudes of direct stiffness are always positive. Cross-coupled stiffness increases slightly with frequency; yet not as drastically as dire stiffness. Comparisons of test results for the 4-stage brush seal with an 8-cavity labyrinth showed superior rotordynamics performance for the brush seal; viz., large values for direct stiffness and lower values for the (destabilizing) cross-coupled stiffness coefficient. The damping for brush seals is smaller, but comparable to labyrinth seals. The whirl-frequency ratio is always smaller for the brush seal. Brush seal, Rotordynamics, Seal, Turbine.

Download or read book The Measurement and Prediction of Rotordynamic Forces for Labyrinth Seals written by D. W. Childs and published by . This book was released on 1988 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of rotordynamic (stiffness and damping) coefficients and leakage characteristics were completed for labyrinth-rotor/honeycombe stator seals. Comparisons to labryinth-rotor/smooth-stator seals showed no stability improvements. Tests were also carried out on smooth-rotor/honeycombe-stator seals and demonstrated superior stability and leakage performance for this type of seal if the entering flow is pre-rotated in the direction of rotation. A new 'bulk-flow' theory for labyrinth seals has been developed and its prediction compare well with measured results for tooth-on-rotor labyrinths. Also, a more sophisticated model was developed which solves the 3-D Reynolds-averaged Navier-Stokes equations for compressible flow. Keywords: Labyrinth seals, Rotordynamic forces, Turbine stators, Computational fluid dynamics. (jes).

Download or read book High Temperature Leakage Performance of a Hybrid Brush Seal Compared to a Standard Brush Seal and a Labyrinth Seal written by Zachary Ashton and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Adequate sealing in turbomachinery reduces secondary leakage and results in more efficient and stable systems. Labyrinth seals are most common, although brush seals are popular in specialized applications. The Hybrid Brush Seal (HBS) is a novel design that adds to the bristle brush matrix a number of cantilever pads that rest on the rotor surface. Upon shaft rotation the pads lift due to the generation of a hydrodynamic gas film while the brushes effectively seal an upstream pressure. Hence the HBS has no wear and no local thermal distortion effects. Measurements of leakage versus pressure differential are obtained in a three-teeth labyrinth, a conventional brush seal, and a hybrid brush seal for operation at high temperature (300o.C), with shaft surface speeds to 27 m/s, and at supply pressures to 3.5 bar. Flow measurements are presented in terms of a flow factor to remove dependency on the air temperature and supply pressure. The measurements demonstrate the HBS leaks less (~61%) than a standard brush seal and is significantly better (~38%) than a similarly sized labyrinth seal. Predictions of flow through a labyrinth seal predict well at supply pressures under 1.7 bar but overpredict by as much as 25% at high supply pressures. A porous medium fluid flow model predicts the flow through the HBS and brush seal. The model for the HBS and brush seal underpredicts the flow rate at low supply pressures but match well at high supply pressures. Measurements of the drag torque of the test seals show the HBS has a larger torque when pressurized compared to the brush seal and labyrinth seal. This indicates that the HBS experiences a larger degree of blow-down due to the pads decreasing the clearance. The mechanical parameters of the brush seal and HBS are found based upon the flexibility function from impact load tests. A combined structural and dry friction damping model represent well the measured flexibility. An equivalent damping is found based upon the energy dissipation. Based upon the damping ratio, the HBS has twice of the viscous damping as the brush seal at a supply pressure of 2.0 bar.

Download or read book Gas Seal Leakage at High Temperature written by Alain Anderson and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Reducing secondary leakage is a common challenge in numerous machines, particularly in steam and gas turbines. Too large leakage in seals produces a substantial loss in efficiency and power delivery with an increase in specific fuel consumption. Various seal types exist, each with unique advantages and disadvantages as per leakage, power loss, and wear. Labyrinth seals are most common due to their simple design and low cost. Their main drawback is a too high leakage due to enlarged (worn) clearances when a rotor vibrates. More complicated seal types, such as brush seals can withstand rotor excursions and ensure lower leakage rates than with labyrinth seals. Brush seals utilize a bristle bed which contacts the rotor and wears out thereby reducing leakage performance. The HALO[superscript TM] seal, an all-metal seal with flexibly supported shoes, is engineered as a clearance control seal to reduce leakage even more, in particular for operation with high pressure differentials and with high surface rotor speeds. Static leakage tests with hot air at a high temperature (max. 300°C) conducted in a test rig holding a labyrinth seal and a novel all-metal seal (HALO[superscript TM] seal), both of the same diameter, length and clearance, show the novel seal leaks ~1/5 the flow of a labyrinth seal for pressure ratios (P[subscript s]/P[subscript a]) > 3.5. The savings in leakage are maximized during operation at high pressure differentials. Leakage measurements with a rotor spinning to a maximum speed of 2,700 rpm (surface speed = 23.6 m/s) produce a slight decrease in leakage with increasing rotor speed. The research product is a reliable leakage data base enabling the application of a state of the art sealing technology that increases system efficiency by reducing leakage and extends maintenance intervals by eliminating wear of components. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151242