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1
Daniels, W. A., B. V. Johnson, D. J. Graber, and R. J. Martin. "Rim Seal Experiments and Analysis for Turbine Applications." Journal of Turbomachinery 114, no. 2 (April 1, 1992): 426–32. http://dx.doi.org/10.1115/1.2929161.
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An experimental investigation was conducted to determine the sealing effectiveness and the aerodynamic characteristics of four rim seal models for a number of flow conditions. The experiments were conducted to obtain an extended data base for advanced turbine rim seal design. The class of rim seals investigated are those found on the downstream side of the rotor where the boundary layer on the disk is pumped directly into the seal gap. The experiments were conducted at disk tangential Reynolds numbers up to 5.1 × 106 with a simulated gas path flow across the top of the seal. The simulated gas path flow was injected with various amounts of swirl to determine the effect of swirl on the seal effectiveness. The radial gap and the axial overlap of the seal were varied and results compared with a baseline configuration. A rim seal configuration intended to prevent disk pumping directly into the seal gap was also investigated. A mass transfer analogy was used to characterize the rim seal ingestion characteristics and the trace gas chosen for this technique was CO2. The results of this investigation indicate that decreasing the radial gap of the seal produces a better improvement in seal effectiveness than increasing the axial overlap of the seal, that seal effectiveness increases only modestly as the swirl across the top of the seal decreases, and that the trace gas technique employed to determine seal effectiveness is an accurate alternative to pressure measurement or flow visualization techniques used by other investigators. The results of this investigation were compared with results from a boundary layer model for rim seals with axial gap geometries.
2
Sun, Dan, Yan Ting Ai, Wan Fu Zhang, and Jian Gang Yang. "Design of a New Kind of the Radial Annular Seal for the Aeroengine." Advanced Materials Research 621 (December 2012): 326–29. http://dx.doi.org/10.4028/www.scientific.net/amr.621.326.
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To minimize fluid leakage loss and improve rotordynamic stability of traditional aeroengine seals, a new kind of radial annular rim seal (RARS) is presented in this paper. Comparing with the conventional labyrinth rim seal (LRS), the fluid leakage direction is modified from the axial to radial direction. The flow resistance increases, and the flow-induced force is greatly reduced. The completed three-dimensional CFD model between RARS and LRS were employed to analyze the inherent characteristics of the fluid flow in the whole passage. Calculated results show that RARS has less leakage and fluid-induced force compared to the LRS.
3
Kirk, R. Gordon. "A Method for Calculating Labyrinth Seal Inlet Swirl Velocity." Journal of Vibration and Acoustics 112, no. 3 (July 1, 1990): 380–83. http://dx.doi.org/10.1115/1.2930519.
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The results of numerous investigators have shown the importance of inlet swirl on the calculated dynamic stiffness and stability of labyrinth seals. These results have not included any calculation of inlet leakage of swirl as a function of complex disk geometry including the sealing conditions of the given seal. This paper outlines a method of calculating the inlet swirl at the entrance of the labyrinth seal by introducing a radial chamber which when added to the axial flow solution allows the prediction of the gas swirl as it flows radially from the stage tip along the disk face inward to the seal location. This solution is consistent with the leakage model for the seal and allows rapid evaluation of seal designs. For a centrifugal compressor, this added feature permits the designer to include the flow path from the impeller discharge, down the back of the disk or front of the cover, then into the shaft seal or eye packing, respectively. The solution includes the friction factors of both the disk and stationary wall with account for mass flow rate and calculation of radial pressure gradients by a free vortex solution. The results of various configurations are discussed and comparisons made to other published results of disk circumferential velocity swirl.
4
Stadnik, Mykola, Serhiy Shargorodskiy, and Volodymyr Rutkevych. "ENSURING CONTINUOUS HYSTERESIS OF SPROAD ACTION VALVE SAFETY VALVES." ENGINEERING, ENERGY, TRANSPORT AIC, no. 4(111) (December 18, 2020): 100–108. http://dx.doi.org/10.37128/2520-6168-2020-4-11.
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In the article principles of construction and design of spring valve units are considered, which allow to obtain a given dynamic quality to ensure constant hysteresis of spool safety valves of direct action. The analysis of efficiency of devices of correction of dynamic quality of spring valve units for ensuring their working capacity at variation of external operating factors by purposeful management of kinematic and force parameters of elastic-damping elements, and also the reasons influencing hysteresis It is noted that one of the reasons for the increase in hysteresis is damage to the rubber seals of the spool safety valves of direct action. Identifying the main causes of damage to rubber seals: constant friction of the edge of the radial holes of the spool on the seal ring; reverse the direction of the operating pressure; the pressure drop created by the axial hole of the spool when the valve is fully open. A spool spring valve with a mechanical spring having high throughput and low hysteresis is proposed. This characteristic was achieved through the use of high quality materials, which allowed to have a high throughput with minimal dimensions; optimization of geometrical characteristics of the flowing part of the valve; reducing the seal tension and, as a consequence, reducing the hysteresis. It is noted that the absence of contact of the radial holes of the spool with the rubber seal in the extreme off position protects the seal from plastic deformation during reverse flow. The prospect of further research in obtaining experimental dependences of the influence of spool speed, rubber stiffness, geometrical characteristics of the contact gap and pressure on the change of the valve hysteresis is revealed.
5
Bayley, F. J., and C. A. Long. "A Combined Experimental and Theoretical Study of Flow and Pressure Distributions in a Brush Seal." Journal of Engineering for Gas Turbines and Power 115, no. 2 (April 1, 1993): 404–10. http://dx.doi.org/10.1115/1.2906723.
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A relatively simple theory is presented that can be used to model the flow and pressure distribution in a brush seal matrix. The model assumes laminar, compressible, isothermal flow and requires knowledge of an empirical constant: the seal porosity value. Measurements of the mass flow rate together with radial and axial distributions of pressure were taken on a nonrotating experimental rig. These were obtained using a 122 mm bore brush seal with 0.25 mm radial interference. The experimental data are used to estimate the seal porosity. Measurements of the pressure distributions along the backing ring and under the bristle tips and discussed. Predicted mass flows are compared with those actually measured and there is reasonable agreement considering the limitations of the model.
6
Kaneko, S. "Application of Porous Materials to Annular Plain Seals: Part 2—Dynamic Characteristics." Journal of Tribology 112, no. 4 (October 1, 1990): 624–30. http://dx.doi.org/10.1115/1.2920307.
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For improving the dynamic performance of the annular plain seals employed in pumps, porous materials are applied to the seal surface by insertion into the inlet part of the seal. The linear stiffness and damping coefficients of the seal film are calculated in the laminar-flow regime, assuming the mass effect of the fluid to be negligibly small. Numerical results show that the annular plain seals with the porous materials have larger main stiffness terms and smaller cross-coupled stiffness terms and main damping terms than the conventional ones with the solid surfaces. This tendency is more marked with increasing the axial length of the porous matrix applied to the seal surface. The larger main stiffness terms for “the porous seal” yield larger radial reaction force acting on a rotor as a consequence of small whirling motion of shaft about a centered position, which would contribute to rotor stability.
7
Zhulyov, A., V. Martsinkovsky, and C. Kundera. "Analysis of Forced Spatial Vibrations of a Centrifugal Pump Impeller with Axial Forces Balancing Device." International Journal of Applied Mechanics and Engineering 21, no. 3 (August 1, 2016): 737–50. http://dx.doi.org/10.1515/ijame-2016-0043.
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Abstract In this paper, a model of a pump impeller with annular seals and a balancing device, used as a combined support-seal assembly, is considered. The forced coupled radial, angular and axial vibrations of the rotor are determined with consideration of linearized inertial, damping, gyroscopic, positional and circulating forces and moments acting on the impeller from the side of the fluid flow in annular seals. The theoretical analysis is supplemented with a numerical example, the amplitude frequency characteristics are shown.
8
Arauz, Grigory L., and Luis San Andre´s. "Analysis of Two-Phase Flow in Cryogenic Damper Seals—Part II: Model Validation and Predictions." Journal of Tribology 120, no. 2 (April 1, 1998): 228–33. http://dx.doi.org/10.1115/1.2834414.
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Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a “continuous vaporization” bulk flow model for prediction of the seal dynamic forced response is given in Part I. The numerical method of solution of the flow equations is detailed here. Computed predictions for static seal characteristics, leakage and axial pressure drop, correlate well with existing measurements for a gaseous nitrogen seal and a liquid nitrogen seal with two-phase at the seal exit plane. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are discussed. Fluid compressibility effects, particularly for mixtures with low mass content of vapor, are of utmost importance. Under these conditions, an increase on seal direct stiffness and reduction of whirl frequency ratio are shown to occur.
9
Childs, D., and F. Garcia. "Test Results for Sawtooth-Pattern Damper Seals: Leakage and Rotordynamic Coefficients." Journal of Tribology 109, no. 1 (January 1, 1987): 124–28. http://dx.doi.org/10.1115/1.3261303.
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Test results consisting of direct and transverse force coefficients are presented for eleven, sawtooth-pattern, damper-seal configurations. The designation “damper” seal refers to a seal which uses a deliberately roughened stator and smooth rotor, as suggested by von Pragenau [1], to increase the net seal damping force. The designation “sawtooth-pattern” refers to a stator-roughness pattern whose cross section normal to the axis of the seal resembles saw teeth with the teeth direction opposing fluid motion in the direction of shaft rotation. The sawtooth pattern yields axial grooves in the stator which are interrupted by spacer elements which act as flow constrictions or “dams.” Sawtooth-pattern seals had more damping than smooth seals but less than the round-hole-pattern seals tested previously. Stiffness of sawtooth and round-hole-pattern seals were comparable. Leakage of maximum-damping configurations was greater for sawtooth-pattern than for round-hole-pattern seals; both types of seals leaked substantially less than did smooth seals. If damping is sacrificed, sawtooth-pattern seals can be designed to leak less than round-hole-pattern seals.
10
Dogu, Yahya. "Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach." Journal of Engineering for Gas Turbines and Power 127, no. 1 (January 1, 2005): 136–44. http://dx.doi.org/10.1115/1.1808425.
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The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.
11
Kong, Xiaozhi, Gaowen Liu, Yuxin Liu, Zhao Lei, and Longxi Zheng. "Performance evaluation of the inter-stage labyrinth seal for different tooth positions in an axial compressor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (November 6, 2017): 579–92. http://dx.doi.org/10.1177/0957650917739532.
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Labyrinth seals are normally used to control the leakage flow in the compressor stator well. The upstream and downstream rotor-stator cavities of the labyrinth seal can cause complex reverse leakage flows. Remarkable temperature increases and high swirl velocities are observed in this region. In addition, another characteristic of inter-stage labyrinth seal is that large expansions of rotor and stator may easily lead to severely rubbing between the teeth and shrouds, which can shorten the lifetime of the compressor obviously. Experiments were conducted at a rotating compressor inter-stage seal test facility. Different labyrinth rings were tested to compare the performances of inter-stage labyrinth seals with different tooth positions. Leakage flow rates, windage heating and swirl ratios in the outlet cavity were measured at different rotating speeds and pressure ratios. In order to get the working tip clearance accurately, the set up tip clearance was measured with plug gauges, while the radial displacements of rotating disc and stationary casing were measured separately with two high precision laser distance sensors. Numerical simulations were carried out to present the important flow physics responsible for the effects of different tooth positions. In this article, performances of different cases for single, double and triple teeth were investigated and the experimental data provide a new way for the design of inter-stage seals. This method can reduce the leakage flow and avoid severely rubbing at the same time by changing axial positions of teeth in the stator well. When teeth are placed downstream of the model and the tooth pitch is larger, the inter-stage seal would have better sealing performance. For triple teeth cases, N = 3-Case1 has the lowest discharge coefficients, 15% less than that of N = 3-Baseline.
12
Gamal, Ahmed M., Bugra H. Ertas, and John M. Vance. "High-Pressure Pocket Damper Seals: Leakage Rates and Cavity Pressures." Journal of Turbomachinery 129, no. 4 (September 3, 2006): 826–34. http://dx.doi.org/10.1115/1.2720871.
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The turbomachinery component of interest in this paper, the pocket damper seal, has the dual purpose of limiting leakage and providing an additional source of damping at the seal location. The rotordynamic coefficients of these seals (primarily the direct stiffness and damping) are highly dependent on the leakage rates through the seals and the pressures in the seals’ cavities. This paper presents both numerical predictions and experimentally obtained results for the leakage and the cavity pressures of pocket damper seals operating at high pressures. The seals were tested with air, at pressures up to 1000psi(6.92MPa), as the working fluid. Earlier flow-prediction models were modified and used to obtain theoretical reference values for both mass flow rates and pressures. Leakage and static pressure measurements on straight-through and diverging-clearance configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal, while the leakage rates for the eight-bladed seals were predicted with reasonable accuracy. Differences in the axial pitch lengths of the cavities and the blade profiles of the seals are used to explain the discrepancy in the case of the twelve-bladed seal. The analysis code used also predicted the static cavity pressures reasonably well. Tests conducted on a six-bladed pocket damper seal to further investigate the effect of blade profile supported the results of the eight-bladed and twelve-bladed seal tests and matched theoretical predictions with satisfactory accuracy.
13
Morrison, G. L., M. C. Johnson, and G. B. Tatterson. "3-D Laser Anemometer Measurements in a Labyrinth Seal." Journal of Engineering for Gas Turbines and Power 113, no. 1 (January 1, 1991): 119–25. http://dx.doi.org/10.1115/1.2906518.
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The flow field inside a seven-cavity labyrinth seal with a 0.00127-m clearance was measured using a 3-D laser-Doppler anemometer system. Through the use of this system, the mean velocity vector and the entire Reynolds stress tensor distributions were measured for the first, third, fifth, and seventh cavities of the seal. There was one large recirculation region present in the cavity for the flow condition tested, Re = 28,000 and Ta = 7000. The axial and radial mean velocities as well as all of the Reynolds stress terms became cavity independent by the third cavity. The azimuthal mean velocity varied from cavity to cavity with its magnitude increasing as the flow progressed downstream.
14
Zhao, Hailin, Hua Su, Guoding Chen, and Yanchao Zhang. "Study on the Leakage and Inter-Stage Pressure Drop Characteristics of Two-Stage Finger Seal." Applied Sciences 11, no. 5 (March 3, 2021): 2239. http://dx.doi.org/10.3390/app11052239.
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To solve the high leakage and high wear problems faced by sealing devices in aeroengines under the condition of high axial pressure difference, the two-stage finger seal is proposed in this paper. The finite element method and computational fluid dynamics (FEM/CFD) coupling iterative algorithm of the two-stage finger seal is developed and validated. Then the performance advantages of two-stage finger seal compared to the one-stage finger seal are studied, as well as the leakage and the inter-stage pressure drop characteristics of two-stage finger seal are investigated. Finally, the measure to improve the inter-stage imbalance of pressure drop of two-stage finger seal is proposed. The results show that the two-stage finger seal has lower leakage and lower contact pressure than the one-stage finger seal at high axial pressure difference, but there exists an inter-stage imbalance of pressure drop. Increasing the axial pressure difference and the root mean square (RMS) roughness of finger element can aggravate the imbalance of pressure drop, while the radial displacement excitation of rotor has little influence on it. The results also indicate that the inter-stage imbalance of pressure drop of the two-stage finger seal can be improved by increasing the number of finger elements of the 1st finger seal and decreasing the number of finger elements of the 2nd finger seal.
15
Cao, Hao, Wanfu Zhang, Lu Yin, and Li Yang. "Numerical Study of Leakage and Rotordynamic Performance of Staggered Labyrinth Seals Working with Supercritical Carbon Dioxide." Shock and Vibration 2022 (January 20, 2022): 1–17. http://dx.doi.org/10.1155/2022/3896212.
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The numerical model of a staggered labyrinth seal working with supercritical carbon dioxide (S–CO2) is established. The dynamic and static characteristics of the staggered labyrinth seal for different axial shifting distances of the rotor, various cavity geometries (heights/widths of the rotor convex plate, heights of the seal cavity), and seal clearances were investigated and compared with the conventional see-through labyrinth seal. The results show that the effective damping coefficient (Ceff) with positive axial shifting distance is higher than that with negative axial shifting distance. When the rotor with convex plate operates without axial shifting, the cross-coupled complex dynamic stiffness (hR) of the staggered labyrinth seal shows little effect on the Ceff, and the average direct damping (Cavg) has a dominant influence on the Ceff. As the whirling frequency (Ω) is lower than 60 Hz, the Ceff decreases with increasing height of the rotor convex plate. For Ω < 140 Hz, the damping coefficient generally increases with the decreasing height of the seal cavity. For Ω < 160 Hz, the Ceff of the see-through labyrinth seal is about 107%–649% of the staggered labyrinth seal. Otherwise, the Ceff of the staggered labyrinth seal is about 105%–113% of the see-through labyrinth seal. The Ceff of the seal with the rotor convex plate width of 5.13 mm is relatively high, which is conducive to the stability of the system. The Ceff increases with the decreasing seal clearance. The Ceff of the seal with 0.4 mm clearance is about 116%–148% the seal with 0.6 mm. The leakage flow rate of the staggered labyrinth seal of the see-through labyrinth seal is increased by about 45.5%. The leakage flow rate of the staggered labyrinth seal decreases with the increasing convex plate height, the seal cavity height, and the decreasing seal clearance.
16
Liu, Yuxin, Benzhuang Yue, Xiaozhi Kong, Hua Chen, and Huawei Lu. "Effects of Front Plate Geometry on Brush Seal in Highly Swirling Environments of Gas Turbine." Energies 14, no. 22 (November 19, 2021): 7768. http://dx.doi.org/10.3390/en14227768.
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Advanced brush seal technology has a significant impact on the performance and efficiency of gas turbine engines. However, in highly inlet swirling environments, the bristles of a brush seal tend to circumferentially slip, which may lead to aerodynamic instability and seal failure. In this paper, seven different front plate geometries were proposed to reduce the impact of high inlet swirl on the bristle pack, and a three-dimensional porous medium model was carried out to simulate the brush seal flow characteristics. Comparisons of a plane front plate with a relief cavity, plane front plate with axial drilled holes, anti-“L”-type plate and their relative improved configurations on the pressure and flow fields as well as the leakage behavior were conducted. The results show that the holed front plate can effectively regulate and control the upstream flow pattern of the bristle pack, inducing the swirl flow to move radially inward, which results in decreased circumferential velocity component. The anti-“L” plate with both axial holes and one radial hole was observed to have the best effect on reducing the swirl of those investigated. The swirl velocity upstream the bristle pack can decline 50% compared to the baseline model with plane front plate, and the circumferential aerodynamic forces on the bristles, which scale with the swirl dynamic head, are reduced by a factor of 4. This could increase the bristle stability dramatically. Moreover, the front plate geometry does not influence the leakage performance significantly, and the application of the axial hole on the front plate will increase the leakage slightly by around 3.5%.
17
Lindsey, W. Todd, and Dara W. Childs. "The Effects of Converging and Diverging Axial Taper on the Rotordynamic Coefficients of Liquid Annular Pressure Seals: Theory Versus Experiment." Journal of Vibration and Acoustics 122, no. 2 (November 1, 1995): 126–31. http://dx.doi.org/10.1115/1.568457.
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Experimental results are compared to predictions for turbulent flow, short (D=76.2mm,L/D=.17), smooth annular seals with converging and diverging axial taper. Results are presented for four geometries with the same minimum clearances: two convergent, two divergent, and a constant-clearance. Measurements were taken at seal pressure differentials and shaft rotation rates ranging from 1.34 to 3.54 MPa and 10,200 to 24,600 rpm, respectively. Measurements parameters include leakage, direct stiffness, cross-coupled stiffness, and direct damping coefficients. Results show that direct stiffness generally increases with converging axial taper and decreases with diverging axial taper; however, direct stiffness decreases in the first increase in the taper angle, contrary to predictions. Direct damping and cross-coupled stiffness were shown to decrease with increasing convergent or divergent taper. Measured damping values increase with increased running speed and decreasing average clearance. Theoretical predictions for rotordynamic coefficients are in reasonable qualitative agreement with measured results. The theory consistently underpredicts leakage by ranges of 10∼30 percent. The accuracy of predictions for leakage and rotordynamic coefficients was not influenced by running speed. [S0739-3717(00)70102-4]
18
Childs, D. W., and J. B. Dressman. "Convergent-Tapered Annular Seals: Analysis and Testing for Rotordynamic Coefficients." Journal of Tribology 107, no. 3 (July 1, 1985): 307–16. http://dx.doi.org/10.1115/1.3261059.
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A combined analytical-computational method is developed to calculate the pressure field and dynamic coefficients for tapered high-pressure annular seals typical of neck-ring and interstage seals employed in multistage centrifugal pumps. Completely developed turbulent flow is assumed in both the circumferential and axial directions and is modeled by Hirs’ bulk-flow turbulent-lubrication equations. Linear zeroth- and first-order perturbation equations are developed for the momentum equations and continuity equations. The development of the circumferential velocity field is defined from the zeroth-order circumferential-momentum equation, and a leakage relationship is defined from the zeroth-order axial-momentum equation. A short-bearing approximation is used to derive an analytical expression for the first-order (dynamic) pressure gradient. This expression is integrated numerically to define dynamic coefficients for the seal. Numerical results are presented and compared to previous results for straight and tapered seals. The direct stiffness and leakage increase with increasing taper angle, while the remaining dynamic coefficients decrease. An optimal taper angle is shown to exist with respect to (a) the direct stiffness, and (b) the ratio of direct stiffness to leakage. Stiffness increases on the order of 40-50 percent are predicted. Experimental results are presented for seals with three taper angles which show generally good agreement between theory and prediction.
19
Moore, J. Jeffrey, and Alan B. Palazzolo. "CFD Comparison to 3D Laser Anemometer and Rotordynamic Force Measurements for Grooved Liquid Annular Seals." Journal of Tribology 121, no. 2 (April 1, 1999): 306–14. http://dx.doi.org/10.1115/1.2833937.
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A pressure-based computational fluid dynamics (CFD) code is employed to calculate the flow field and rotordynamic forces in a whirling, grooved liquid annular seal. To validate the capabilities of the CFD code for this class of problems, comparisons of basic fluid dynamic parameters are made to three-dimensional laser Doppler anemometer (LDA) measurements for a spinning, centered grooved seal. Predictions are made using both a standard and low Reynolds number κ-ε turbulence model. Comparisons show good overall agreement of the axial and radial velocities in the through flow jet, shear layer, and recirculation zone. The tangential swirl velocity is slightly under-predicted as the flow passes through the seal. By generating an eccentric three-dimensional, body fitted mesh of the geometry, a quasi-steady solution may be obtained in the whirling reference frame allowing the net reaction force to be calculated for different whirl frequency ratios, yielding the rotordynamic force coefficients. Comparisons are made to the rotordynamic force measurements for a grooved liquid annular seal. The CFD predictions show improved stiffness prediction over traditional multi-control volume, bulk flow methods over a wide range of operating conditions. In cases where the flow conditions at the seal inlet are unknown, a two-dimensional, axisymmetric CFD analysis may be employed to efficiently calculate these boundary conditions by including the upstream region loading to the seal. This approach is also demonstrated in this study.
20
Braun, M. J., V. V. Kudriavtsev, B. M. Steinetz, and M. P. Proctor. "Two- and Three-Dimensional Numerical Experiments Representing Two Limiting Cases of an In-Line Pair of Finger Seal Components." International Journal of Rotating Machinery 9, no. 3 (2003): 171–79. http://dx.doi.org/10.1155/s1023621x03000162.
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The work presented here concerns the numerical development and simulation of the flow, pressure patterns, and motion of a pair of fingers arranged one behind the other and axially aligned in line. The fingers represent the basic elemental component of a finger seal and form a tight seal around the rotor. Yet their flexibility allows compliance with rotor motion and, in a passive-adaptive mode, compliance with the hydrodynamic forces induced by the flowing fluid. Although this article does not treat the actual staggered configuration of a finger seal, the in-line arrangement represents a first step toward that final goal. The numerical two-dimensional (axial-radial) and three-dimensional results presented herein were obtained using a commercial package (CFD-ACE+). Both models use an integrated numerical approach, which couples the hydrodynamic fluid model based on Navier-Stokes equations to the solid mechanics code that models the compliance of the fingers.
21
Sun, Huifang, Yue Lv, Jinbing Ni, Xianyu Jiang, and Zhengwei Wang. "Effect of Seal Locations of Pump-Turbine on Axial Hydraulic Trust." Journal of Marine Science and Engineering 9, no. 6 (June 4, 2021): 623. http://dx.doi.org/10.3390/jmse9060623.
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Axial hydraulic thrust is an important factor that affects safety and stability of pump turbine operation. Research and analysis of axial hydraulic thrust is of a great significance for guiding the safe and stable operation of a pumped storage power station. Since the runner shape of the pump turbine is flat and its radial dimension is large, an increase of leakage can happen easily. In order to reduce the leakage and improve the efficiency of the unit, a labyrinth ring seal is usually used in the upper crown and lower ring of the runner because the inner clearance of the seal has a great influence on the axial thrust. In order to study the influence of the change of labyrinth seal position on axial hydraulic thrust, a fluid domain model with a pressure balance pipe, upper crown clearance, and lower ring clearance is established for a pump turbine of a power station. The distribution position of labyrinth ring in the upper crown clearance is changed. The CFD numerical simulations are carried out under both 100% working load and 75% working load of turbine conditions, considering the flow in clearance areas. The research results of this paper have found that the axial hydraulic thrust of the 100% load condition is consistent with the change of the gap position compared with the 75% load condition. The amplitude of the change of the water thrust under the 100% load condition is greater. As the sealing position of the labyrinth ring in the upper crown gap moves away from the central axis, the resultant vertical and upward water thrust increases, and the operating efficiency of the unit first increases and then decreases. As the position of the labyrinth ring seal in the upper ring clearance moves away from the central axis, the resultant vertical and upward water thrust increases, and the operating efficiency of the unit first increases and then decreases. Defining the radial dimension ratio δ between the front clearance area and the total area of labyrinth ring, the closer δ is to 0.5, the unit efficiency is higher; the smaller that δ is, then the high pressure area in the upper crown clearance is smaller, and the hydraulic thrust force increases vertically. Considering a variety of factors, the clearance seal position has the optimal value. In the practical application of the project, the condition of excessive upward hydraulic thrust leading to the lifting of the unit can be avoided, and the phenomenon of excessive downward hydraulic thrust leading to the excessive load-bearing of the frame is evitable.
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Turner, M. T., J. W. Chew, and C. A. Long. "Experimental Investigation and Mathematical Modeling of Clearance Brush Seals." Journal of Engineering for Gas Turbines and Power 120, no. 3 (July 1, 1998): 573–79. http://dx.doi.org/10.1115/1.2818185.
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In this paper, an experimental program and a CFD based mathematical model using a brush seal at two bristle to rotor clearances (0.27 mm and 0.75 mm) are presented. The experimental program examined the radial pressure distributions along the backing ring, the axial pressure distribution along the rotor, and the mass flow through the seal through a range of pressure ratios while exhausting to atmosphere. The results from this experimental program have been used to further calibrate a CFD-based model. This model treats the bristle pack as an axisymmetric, anisotropic porous region, and is calibrated by the definition of nonlinear resistance coefficients in three orthogonal directions. The CFD analysis calculates the aerodynamic forces on the bristles, which are subsequently used in a separate program to estimate the bristle movements, stresses, and bristle and rotor loads. The analysis shows that a brush seal with a build clearance produces a very different flow field within the bristle pack to one with an interference, and the need to understand the bulk movements of the bristles. These are shown to be affected by the level of friction between the bristles and the backing ring, which has an important effect on the bristles wear and seal leakage characteristics.
23
Adebayo, David Shina, and Aldo Rona. "The Three-Dimensional Velocity Distribution of Wide Gap Taylor-Couette Flow Modelled by CFD." International Journal of Rotating Machinery 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/8584067.
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A numerical investigation is conducted for the flow between two concentric cylinders with a wide gap, relevant to bearing chamber applications. This wide gap configuration has received comparatively less attention than narrow gap journal bearing type geometries. The flow in the gap between an inner rotating cylinder and an outer stationary cylinder has been modelled as an incompressible flow using an implicit finite volume RANS scheme with the realisablek-εmodel. The model flow is above the critical Taylor number at which axisymmetric counterrotating Taylor vortices are formed. The tangential velocity profiles at all axial locations are different from typical journal bearing applications, where the velocity profiles are quasilinear. The predicted results led to two significant findings of impact in rotating machinery operations. Firstly, the axial variation of the tangential velocity gradient induces an axially varying shear stress, resulting in local bands of enhanced work input to the working fluid. This is likely to cause unwanted heat transfer on the surface in high torque turbomachinery applications. Secondly, the radial inflow at the axial end-wall boundaries is likely to promote the transport of debris to the junction between the end-collar and the rotating cylinder, causing the build-up of fouling in the seal.
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Luo, Yin, Wenqi Zhang, Yakun Fan, Yuejiang Han, Weimin Li, and Emmanuel Acheaw. "Analysis of Vibration Characteristics of Centrifugal Pump Mechanical Seal under Wear and Damage Degree." Shock and Vibration 2021 (April 8, 2021): 1–9. http://dx.doi.org/10.1155/2021/6670741.
Full textAbstract:
Mechanical seal is a kind of shaft sealing equipment. Face wear is one of the main causes of mechanical seal failure. Mechanical seal condition is also related to the reduction of energy consumption and carbon emission. Therefore, we need to detect the centrifugal pump seal condition. At present, vibration signal is a common method for fault monitoring and diagnosis of centrifugal pump. In this paper, the vibration signal under the condition of damaged centrifugal pump seal is measured by studying the characteristics of vibration signal after the end face damage of centrifugal pump. Statistical indicators such as RMS and kurtosis were taken to analyze the average energy and shock wave energy of vibration signal. The time-frequency characteristics of vibration signal are analyzed by frequency spectrum. The results show that there are a large extent variation of vibration amplitude in the direction of base and axis and a weak variation of vibration amplitude in the direction of radial and vertical. With the increasing of flow rate, the RMS of vibration signal falls at first, then keeps steady, and mounts at last when the flow rate is over the design flow rate. It can be shown from the time-frequency spectrum that there is a shock wave and pause signals caused by the shock wave, which are reflected by the higher frequency band components of the vibration signal that can provide a reference to the diagnosis of the occurrence of damaged mechanical seal. From the analysis, the energy of vibration signal is related to the running condition, we can find that the occurrence of mechanical seal wear makes the centrifugal pump to produce high-frequency vibration signal, and the axial vibration is the strongest and the instability in the fluid makes the vibration signal produce high amplitude characteristics. Analyzing the vibration signal characteristics of centrifugal pumps with damaged mechanical seal is of great significance to find the mechanical seal failure of the centrifugal pumps and adjust the operating parameters.
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Tam, L. T., A. J. Przekwas, A. Muszynska, R. C. Hendricks, M. J. Braun, and R. L. Mullen. "Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings." Journal of Vibration and Acoustics 110, no. 3 (July 1, 1988): 315–25. http://dx.doi.org/10.1115/1.3269519.
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A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.
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Kühl, Hans-Detlev, and Jan Sauer. "Appendix gap losses in Stirling engines – review of recent findings." E3S Web of Conferences 313 (2021): 03001. http://dx.doi.org/10.1051/e3sconf/202131303001.
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The appendix gap loss in Stirling cycle machines is generated by the annular gap around the thermally insulating, thin-walled dome typically attached to a piston or displacer plunging into the hot cylinder volume of an engine or the cold volume of a cryocooler. It was considered to be of minor importance for decades. Thus, simplified analytical models were considered sufficiently accurate for its description, until numerical simulations and experimental results gave rise to a more detailed analysis revealing that, neglecting entrance and end effects, the flow is typically laminar, but unsteady. Subsequently, an enhanced analytical model accounting for fluidic and thermal inertia effects as well as the volumetric displacement by the seal was developed. Compared to the previous ones, this model predicts a shift of the optimum width to smaller values, a higher minimum overall loss and furthermore, an option to decrease the loss by reducing the effective seal diameter. This could be experimentally confirmed as well as the unsteady gas temperature profiles predicted by this model. Subsequently, both theoretically and experimentally founded correlations for the radial and axial energy transport in the gap were derived and implemented in a differential simulation of the gap within a third order code.
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Sun, Junfeng, Meihong Liu, Zhen Xu, and Taohong Liao. "Research on operating parameters of T-groove cylindrical gas film seal based on computational fluid dynamics." Advanced Composites Letters 28 (January 1, 2019): 096369351986437. http://dx.doi.org/10.1177/0963693519864373.
Full textAbstract:
Cylindrical gas film sealing technology is a new type of dry gas sealing technology. Compared with the face gas film sealing technology, the cylindrical gas film seal presents a strong floating property, which can reduce the vibration and thermal deformation of the rotor system. In this article, the effect of operating parameters such as speed, pressure difference and viscosity on the T-groove gas cylindrical film seal performance are studied in detail by the method of control variable in computational fluid dynamics software, and pressure distribution, gas film stiffness, leakage, leakage stiffness ratio and hydrodynamic force are analysed. Results show that with the increase of the rotational speed, static pressure, hydrodynamic force and film stiffness increase, but leakage decreases first and then increases. Furthermore, the results indicate that with the increase of pressure difference, the static pressure, leakage and hydrodynamic force increase. In addition, the simulations show that when the viscosity increases, the maximum pressure and film stiffness increase, but the leakage decreases. This indicates that as the rotational speed increases, the hydrodynamic effect and the amount of gas overflow in the axial direction increase, resulting in an increase of leakage. Lastly, the results also show that when the pressure difference increases, both the radial and axial gas flow rates increase, resulting in an increase in both the film stiffness and the leakage. With the increase of viscosity, the viscous shear force and fluid hydrodynamic force increase, resulting in the increase of the gas film stiffness. This study can provide a theoretical basis in industrial applications for setting the operating parameters and serving as a reference.
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Shade, W. N., and D. E. Hampshire. "An Experimental Investigation of Oil-Buffered Shaft Seal Flow Rates." Journal of Engineering for Gas Turbines and Power 107, no. 1 (January 1, 1985): 170–80. http://dx.doi.org/10.1115/1.3239679.
Full textAbstract:
An experimental investigation was conducted to identify an optimum oil-buffered shaft seal for use on centrifugal compressors, with the primary objective being minimal seal oil exposure to process gases that cause seal oil degradation or are toxic. Types of seals tested included smooth bore cylindrical bushings, spiral groove cylindrical bushings, radial outward-flow face seals, and radial inward-flow face seals. The influence of shaft speed, gas pressure, seal oil differential pressure, oil bypass flow rate, and oil supply temperature on process side seal oil flow rate was determined. The investigation revealed some surprising relationships between seal oil flow rates and the escape of process gas.
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Childs, D. W. "Fluid-Structure Interaction Forces at Pump-Impeller-Shroud Surfaces for Rotordynamic Calculations." Journal of Vibration and Acoustics 111, no. 3 (July 1, 1989): 216–25. http://dx.doi.org/10.1115/1.3269845.
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Governing equations of motion are derived for a bulk-flow model of the leakage path between an impeller shroud and a pump housing. The governing equations consist of a path-momentum, a circumferential-momentum, and a continuity equation. The fluid annulus between the impeller shroud and pump housing is assumed to be circumferentially symmetric when the impeller is centered; i.e., the clearance can vary along the pump axis but does not vary in the circumferential direction. A perturbation expansion of the governing equations in the eccentricity ratio yields a set of zeroth and first-order governing equations. The zeroth-order equations define the leakage rate and the circumferential and path velocity distributions and pressure distributions for a centered impeller position. The first-order equations define the perturbations in the velocity and pressure distributions due to either a radial-displacement perturbation or a tilt perturbation of the impeller. Integration of the perturbed pressure and shear-stress distribution acting on the rotor yields the reaction forces and moments acting on the impeller face. Calculated results yield predictions of possible resonance peaks of the fluid within the annulus formed by the impeller shroud and housing. Centrifugal acceleration terms in the path-momentum equation are the physical origin of these unexpected predictions. For normalized tangential velocities at the inlet to the annulus, uθ0(0) = Uθ0(0)/Riω of 0.5, the phenomenon is relatively minor. As uθ0(0) is increased to 0.7, sharp peaks are predicted. Comparisons for rotordynamic coefficient predictions with test results of Bolleter et al. show reasonable agreement for cross-coupled stiffness and direct damping terms. Calculated results are provided which make comparisons between seal forces and shroud forces for a typical impeller/wear-ring-seal combination.
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Ma, Dengqian, Jun Li, Yuanqiao Zhang, Zhigang Li, Xin Yan, and Liming Song. "Application of blade tip shroud brush seal to improve the aerodynamic performance of turbine stage." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, no. 6 (October 22, 2019): 777–94. http://dx.doi.org/10.1177/0957650919883153.
Full textAbstract:
The blade tip shroud brush seal is applied to replace the labyrinth seal for the aerodynamic performance improvement of turbine stage. The leakage flow characteristics of the brush seal are numerically predicted by using the Reynolds-Averaged Navier–Stokes equations and non-linear Darcian porous medium model. The numerical leakage flow rate of the brush seal is in well agreement with the experimental data. The last and first long teeth of the labyrinth seal were designed to bristle pack named as the postposed and preposed brush seals based on the 1.5 turbine stage. The leakage flow rate and aerodynamic performance of the turbine stage with blade tip shroud labyrinth seal and brush seal are numerically investigated. The effect of the sealing clearance between bristle pack and tip shroud on the aerodynamic performance of turbine stage is conducted which ranged from 0 mm to 0.4 mm. The axial deflection of the bristle pack is analyzed with consideration of the aerodynamic forces and contact frictional force. The obtained results show that the leakage flow rate of the tip shroud brush seals with bristle tip 0.4 mm clearance which decreases by up to 18% in comparison with the labyrinth seal, and the aerodynamic efficiency increases by 0.6%. Compared to the tip labyrinth seal, tip shroud brush seals can decrease the relative deflection angle of exit flow. This flow behavior results in reducing the mixing loss between the tip leakage flow and mainstream. The similar axial deflection of the bristle pack for two kinds of brush seals is observed at the same sealing clearance. The deflection of the bristle pack under the function of the aerodynamic forces is protected by the backing plate. This work provides the theoretical basis and technical support for the brush seal application in the turbine industries.
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Soto, E. A., and D. W. Childs. "Experimental Rotordynamic Coefficient Results for (a) a Labyrinth Seal With and Without Shunt Injection and (b) a Honeycomb Seal." Journal of Engineering for Gas Turbines and Power 121, no. 1 (January 1, 1999): 153–59. http://dx.doi.org/10.1115/1.2816303.
Full textAbstract:
Centrifugal compressors are increasingly required to operate at higher pressures, speeds, and fluid density. In these conditions, compressors are susceptible to rotordynamic instabilities. To remedy this situation, labyrinth seals have sometimes been modified by using shunt injection. In shunt injection, the gas is taken from the diffuser or discharge volute and injected into an upstream chamber of the balance-piston labyrinth seal. The injection direction can be radial or against rotation. This study contains the first measured rotordynamic data for labyrinth seals with shunt injection. A comparison has been made between conventional labyrinth seals, labyrinth seals with shunt injection (radial and against rotation), and a honeycomb seal. Labyrinth seals with injection against rotation are better able to control rotordynamic instabilities than labyrinth seals with radial injection; however, the leakage is slightly higher. The leakage comparison for all seals demonstrates that the honeycomb seal has the best flow control. Test data are presented for a top rotor surface velocity of 110 m/sec, a supply pressure of 13.7 bars, and IPr = 0.95 (injection pressure is 1.05 = 1/0.95 times the seal inlet pressure). For these conditions, and considering effective damping, the labyrinth seal with injection against rotation is better than the honeycomb seal when the pressure ratio across the seal PR < 0.45. On the other hand, the honeycomb seal is better when PR > 0.45. The effectiveness of the shunt-injection against rotation in developing effective damping is reduced with increasing rotor surface velocity.
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Xi, Jinxiang, and David L. Rhode. "Rotordynamics of Turbine Labyrinth Seals with Rotor Axial Shifting." International Journal of Rotating Machinery 2006 (2006): 1–11. http://dx.doi.org/10.1155/ijrm/2006/93621.
Full textAbstract:
Rotors in high-performance steam turbines experience a significant axial shifting during starting and stopping processes due to thermal expansion, for example. This axial shifting could significantly alter the flow pattern and the flow-induced rotordynamic forces in labyrinth seals, which in turn, can considerably affect the rotor-seal system performance. This paper investigates the influence of the rotor axial shifting on leakage rate as well as rotordynamic forces in high-low labyrinth seals over a range of seal clearances and inlet swirl velocities. A well-established CFD-perturbation model was employed to predict the rotordynamic coefficients. A surprisingly large effect was detected for rotordynamic characteristics due to rotor shifting. It was also found that a less destabilizing effect arose from rotor axial shifting in the leakage flow direction, whereas a more destabilizing effect arose from shifting against the leakage flow direction. Further, a tentative explanation was proposed for the large sensitivities of dynamic forces to rotor axial shifting.
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Childs, D. W., and J. K. Scharrer. "Theory Versus Experiment for the Rotordynamic Coefficient of Labyrinth Gas Seals: Part II—A Comparison to Experiment." Journal of Vibration and Acoustics 110, no. 3 (July 1, 1988): 281–87. http://dx.doi.org/10.1115/1.3269514.
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An experimental test facility is used to measure the leakage and rotordynamic coefficients of teeth-on-rotor and teeth-on-stator labyrinth gas seals. The test results are presented along with the theoretically predicted values for the two seal configurations at three different radial clearances and shaft speeds to 16,000 cpm. The test results show that the theory accurately predicts the cross-coupled stiffness for both seal configurations and shows improvement in the prediction of the direct damping for the teeth-on-rotor seal. The theory fails to predict a decrease in the direct damping coefficient for an increase in the radial clearance for the teeth-on-stator seal.
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Ma, Fang Bo, Peng Yun Song, and Jie Gao. "Numerical Analysis of Radial Groove Gas-Lubricated Face Seals at Slow Speed Condition." Advanced Materials Research 468-471 (February 2012): 2304–9. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.2304.
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An effective finite difference method (FDM) is adopted to calculate the pressure distribution of radial groove gas-lubricated face seals at slow speed condition. Some key parameters of seal performance, such as open force, gas film stiffness, and leakage rate are calculated. Effect of seal ring parameters on seal performance is also analyzed. Compared with the results of non-slip-flow condition, it is shown that the effect of slip flow should be considered when the gas seal is analyzed at slow speed
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Dadkhah, S., A. B. Turner, and J. W. Chew. "Performance of Radial Clearance Rim Seals in Upstream and Downstream Rotor–Stator Wheelspaces." Journal of Turbomachinery 114, no. 2 (April 1, 1992): 439–45. http://dx.doi.org/10.1115/1.2929163.
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A new experimental facility for the investigation of rim sealing is described and measurements are presented for two representative radial clearance seals with a nominally axisymmetric external flow. One radial seal has an upward rotor lip and is upstream of the rotor, while the other has an upward stator lip and is downstream of the rotor. Measurements include surface pressures, tangential velocities in the core region of the disk cavity flow, and traverses of gas concentration in the cavity showing the distribution of mainstream ingestion. Tests were conducted at rotational Reynolds numbers up to 3 × 106 with nominal seal clearance to radius ratios in the range 0.002 to 0.01. For the radial seals a differential pressure criterion is found to overestimate the minimum sealing flow. Tangential velocity measurements in the wheelspace are in excellent agreement with other workers’ measurements and with theoretical predictions.
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Bondarenko, G. A., V. N. Baga, and I. A. Bashlak. "Flow Simulation in a Labyrinth Seal." Applied Mechanics and Materials 630 (September 2014): 234–39. http://dx.doi.org/10.4028/www.scientific.net/amm.630.234.
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The paper studies the labyrinth seals of centrifugal compressor profit-proved stages using modern methods of numerical and physical modeling of the centrifugal compressor stages. A series of studies of the effect of operational and geometrical parameters on the maze, namely the quantities of the packed differential pressure, speed, fluid, geometric parameters of the seal, the magnitude of the eccentricity and radial clearance swirl flow at the inlet of a seal, etc. The technique of physical modeling seal has been specified. Research was conducted in two phases: numerical simulation using complex software Flow Vision and receiving data on a universal test bench to study the labyrinth seals.. A three-dimensional model of the labyrinth seal has been created, its verification by "known data has been held.. Integral characteristics in the form of distribution of flow velocities and pressures, flow visualization were obtained. Results of studies made it possible to refine the workflow and introduce amendments to the known calculation formula for a more accurate calculation of leakage through the seal, subject to a number of additional factors that were not previously taken into account
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Kilgore, J. J., and D. W. Childs. "Rotordynamic Coefficients and Leakage Flow of Circumferentially Grooved Liquid-Seals." Journal of Fluids Engineering 112, no. 3 (September 1, 1990): 250–56. http://dx.doi.org/10.1115/1.2909397.
Full textAbstract:
Measured leakage flow and rotordynamic coefficients for six, circumferentially-grooved, liquid seals are compared to predictions based on Nordmann et al.’s (1986) grooved seal model. The grooved seal model uses a modification of Hirs’ (1973) bulk-flow theory to account for the difference in friction factor in the circumferential and axial directions due to the grooves. Also, the model uses an average groove depth to account for the circumerential flow in the grooves. Comparison of the predicted and measured friction factors in grooved-seals with orbiting-rotors shows a poor correlation. In spite of the poor friction-factor correlation, the accuracy of predictions for rotordynamic coefficients are comparable to predictions of Childs et al. (1988) and Childs and Kim (1986) for smooth and hole pattern seals.
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Zhang, Kai, Xinkuo Jiang, Shiyang Li, Bin Huang, Shuai Yang, Peng Wu, and Dazhuan Wu. "Transient CFD Simulation on Dynamic Characteristics of Annular Seal under Large Eccentricities and Disturbances." Energies 13, no. 16 (August 5, 2020): 4056. http://dx.doi.org/10.3390/en13164056.
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Annular seals of turbomachinery usually suffer from various degrees of eccentricities and disturbances due to the rotor–stator misalignment and radial loads, while the discussion of annular seal under both large static eccentricities and dynamic disturbances is relatively limited. In this paper, the applicability of linear assumption and reliability of nonlinear dynamic model for eccentric annular seals under large eccentricities and disturbances is discussed based on the investigation of seals with various rotor motions through computational fluid dynamics (CFD). After the validation of transient CFD methods by comparison with experimental and bulk theory results, the dynamic behaviors of annular seal are analyzed by adopting both direct transient simulations and the nonlinear Muszynska model. The results show that the nonlinear dynamic model based on rotor circular whirls around seal center can predict the fluid excitations of different types of rotor motions well under small static eccentricities, while it is limited severely with large static eccentricities, which indicates that the dynamic characteristics of annular seal under large eccentricities are related with the rotor’s motion ways. The paper provides a reference for studies of rotor–seal system with complex rotor motions considering radial loads or running across the resonance region.
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Zhao, Haifang, and Robert J. Stango. "Effect of Flow-Induced Radial Load on Brush Seal/Rotor Contact Mechanics." Journal of Tribology 126, no. 1 (January 1, 2004): 208–15. http://dx.doi.org/10.1115/1.1609492.
Full textAbstract:
Brush seals comprised of special-alloy wire bristles are currently being used in lieu of traditional labyrinth seals for turbomachinery applications. This advancement in seal technology utilizes close-packed bristles that readily undergo lateral deformation arising from aerodynamic loads as well as loads imparted by the rotor surface. Thus, during operation, filament tips remain in contact with the rotor surface, which, in turn, inhibits leakage between successive stages of the turbine, and increases engine efficiency. However, contact forces generated at the interface of the rotor and fiber tips can lead to eventual bristle fatigue and wear of the seal/rotor system. Therefore, it is important that reliable modeling techniques be developed that can help identify complex relationships among brush seal design parameters, in-service loads, and contact forces that arise during the operation of turbomachinery. This paper is concerned with modeling and evaluating bristle deformation, bending stress, and bristle/rotor contact forces that are generated at the interface of the fiber and rotor surface due to radial fluid flow, and augments previous work reported by the author’s, which assessed filament tip forces that arise solely due to interference between the bristle/rotor. The current problem derives its importance from aerodynamic forces that are termed “blow-down,” that is, the inward radial flow of gas in close proximity to the face of the seal. Thus, bristle deformation, bristle tip reaction force, and bristle bending stress is computed on the basis of an in-plane, large-displacement mechanics analysis of a cantilever beam that is subjected to a uniform radial load. Solutions to the problem are obtained for which the filament tip is constrained to lie on the rotor surface, and includes the effect of Coulombic friction at the interface of the fiber tip and rotor. Contact forces are obtained for a range of brush seal design parameters including fiber lay angle, flexural rigidity, and length. In addition, the governing equation is cast in non-dimensional form, which extends the range of applicability of solutions to brush seals having a more general geometry and material composition.
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Yu, Xin Qi, Mei Hong Liu, Zhen Hui Wang, Pei Ying Peng, and Ren Liang Cai. "Experimental Investigation on Friction Performance of Mechanical Seals with a Laser-Textured Seal Face." Materials Science Forum 532-533 (December 2006): 81–84. http://dx.doi.org/10.4028/www.scientific.net/msf.532-533.81.
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Regular micro-surface structure in the form of micro-pores produced on the face of mechanical seals by laser technology can be used to improve the friction performance of the seal mating rings. A test rig with variable axial load was used to test laser-textured seal rings with micro-pores of various pore depth and pore ratio to study the effect of the laser-textured seal face structure parameters on the friction performance of mechanical seals. It is found that there are optimum texturing face parameters at which the friction torque and the face temperature rise of seal rings are minimum. Results of these tests show that the micro-pores on one of the seal mating faces can generate substantial hydrodynamic effect. Heat generation due to frictional contact on seal-ring surfaces is a major factor that causes deterioration of face seals and shortens their service life[1,2]. Excessive temperature rise can be avoided by improving structure of a seal surface. By means of laser technology return-flow structure, oblique line groove and spherical micro-pores are engraved on the seal face[3-5]. The research shows that substantial hydrodynamic effect can be generated between the seal faces with micro-pores[6-8]. In this study experiments are performed on laser-textured micro-pores seal faces at various axial loads to investigate the effect of the face structure and operating parameters on friction torque and face temperature rise.
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Childs, Dara W., Matthew Graviss, and Luis E. Rodriguez. "Influence of Groove Size on the Static and Rotordynamic Characteristics of Short, Laminar-Flow Annular Seals." Journal of Tribology 129, no. 2 (January 5, 2007): 398–406. http://dx.doi.org/10.1115/1.2647471.
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Test results are presented for a smooth seal and three centrally grooved seals that are representative of buffered-flow oil seals in centrifugal compressors. The seals are short (L∕D≅0.21), with a diameter of 117mm and a nominal radial clearance of 0.085mm, netting the clearance-to-radius ratio 0.0015. The grooves have groove depth to clearance ratios (Dg∕Cr) of 5, 10, and 15. Test conditions include three shaft speeds from 4000rpm to 10,000rpm, three inlet oil pressures from 24bar to 70bar, and seal eccentricity ratios from 0 (centered) to 0.7. Dynamic results include stiffness, damping, and added-mass coefficients; static results include stator position, attitude angles, and seal leakage. Stiffness, damping, and mass coefficients plus leakage are compared for the seal geometries. Results show that all rotordynamic coefficients consistently decrease with increasing seal groove depths, and seal leakage is largely unchanged. Comparisons are also made between experimental results and predictions from a computer program based on a Reynolds + energy equation model. The model includes the assumption that a groove is large enough to create separate lands within the seal, creating a zero or negligible pressure perturbation within the groove. Test results show that even the deepest groove depth tested is not deep enough to satisfy this assumption.
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Du, Qiuwan, and Di Zhang. "Numerical Investigation on Flow Characteristics and Aerodynamic Performance of a 1.5-Stage SCO2 Axial-Inflow Turbine with Labyrinth Seals." Applied Sciences 10, no. 1 (January 3, 2020): 373. http://dx.doi.org/10.3390/app10010373.
Full textAbstract:
The leakage problem of supercritical carbon dioxide (SCO2) axial-inflow turbine brings great challenges to the efficiency and security of the power system. Labyrinth seals are usually utilized to improve the leakage characteristics of the blade tip. In this paper, a 1.5-stage SCO2 axial-inflow turbine is established and labyrinth seals are arranged on the top of the first stage stator and rotor blades. The effects of seal clearance, groove on seal cavity surface and circle groove shape on flow characteristics and aerodynamic performance under different pressure ratio are investigated. Increasing seal clearance can significantly weaken the turbine performance. Arranging rectangle, circle and V-shaped grooves on the seal cavity surface near the outlet of the seal gap can enhance the energy dissipation, reduce the relative leakage and improve the power and efficiency. Increasing the groove width can improve the aerodynamic performance while the effect of the groove depth is weak. The configuration where the circle groove width is 50% of the pitch of seal tooth achieves the best performance with the relative leakage of stator1 and rotor, power and efficiency of 6.04 × 10−3, 8.09 × 10−3, 3.467 MW and 86.86% respectively. With an increase in pressure ratio, the relative leakage increases firstly and then remains almost constant. The power increases while the efficiency increases firstly and then decreases, reaching the peak value under the design condition.
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Joachimiak, Damian, and Andrzej Frąckowiak. "Experimental and Numerical Analysis of the Gas Flow in the Axisymmetric Radial Clearance." Energies 13, no. 21 (November 5, 2020): 5794. http://dx.doi.org/10.3390/en13215794.
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This paper focuses on the analysis of the gas flow in the axisymmetric mini gap bounded by the surface of the top of the labyrinth seal tooth and the surface of the body. It includes the results of experimental research and numerical calculations. Experimental research focused on the analysis of gas flow for six clearance heights in a wide range of pressure drops. Based on this research, we determined the mass flow in the clearance. Using the Saint-Venant equation, we determined the flow coefficient versus the pressure ratio upstream and downstream from the seal. Flow coefficients for various clearance heights obtained from the experiment can be divided into two data groups, the values of which differ significantly. To explain changes in the value of the gas flow coefficient for selected clearance heights, numerical analysis of the said gas flow was performed using the Fluent software. This analysis allowed us to explain the reason for the variability of the flow coefficient. This research can be the basis for determining the change of seal integrity during operation for staggered and stepped seals.
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Перевезенцев, Виктор, Viktor Perevezentsev, Максим Шилин, and Maksim Shilin. "Improving the design of the seal gaps in the flow of the pumping unit GTK-10-4." Bulletin of Bryansk state technical university 2015, no. 1 (March 31, 2015): 35–40. http://dx.doi.org/10.12737/22746.
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Describes the methods of modernization seal the radial clearance of the gas turbine by using the honeycomb structure at the periphery of the wheel. Discusses the gas-dynamic and thermal engineering problems using honeycomb seals in turbomachinery.
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Da Soghe, Riccardo, Cosimo Bianchini, Carl M. Sangan, James A. Scobie, and Gary D. Lock. "Numerical Characterization of Hot-Gas Ingestion Through Turbine Rim Seals." Journal of Engineering for Gas Turbines and Power 139, no. 3 (October 11, 2016). http://dx.doi.org/10.1115/1.4034540.
Full textAbstract:
This paper deals with a numerical study aimed at the characterization of hot-gas ingestion through turbine rim seals. The numerical campaign focused on an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. Single-clearance arrangements were considered in the form of axial- and radial-seal gap configurations. With the radial-seal clearance configuration, computational fluid dynamics (CFD) steady-state solutions were able to predict the system sealing effectiveness over a wide range of coolant mass flow rates reasonably well. The greater insight of flow field provided by the computations illustrates the thermal buffering effect when ingress occurs: For a given sealing flow rate, the effectiveness on the rotor was significantly higher than that on the stator due to the axial flow of hot gases from stator to rotor caused by pumping effects. The predicted effectiveness on the rotor was compared with a theoretical model for the thermal buffering effect showing good agreement. When the axial-seal clearance arrangement is considered, the agreement between CFD and experiments worsens; the variation of sealing effectiveness with coolant flow rate calculated by means of the simulations displays a distinct kink. It was found that the “kink phenomenon” can be ascribed to an overestimation of the egress spoiling effects due to turbulence modeling limitations. Despite some weaknesses in the numerical predictions, the paper shows that CFD can be used to characterize the sealing performance of axial- and radial-clearance turbine rim seals.
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Jia, Xingyun, Lidong He, Chunrui Liu, and Le Zhang. "Buffer effect of turbine rim cavity on hot gas ingestion." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, April 17, 2022, 095765092210824. http://dx.doi.org/10.1177/09576509221082449.
Full textAbstract:
The rotor disc in the gas turbine creates a pump effect that entrains the fluid near it to radially outward. The hot gas in the mainstream enters the stator–rotor wheel space to maintain mass balance, leading to gas ingestion. The mechanism of the gas ingestion, and the spoiling effect of purge flow on mainstream, and the formation and transform mechanism of the source and core fluid regions in rotor–stator system are revealed in this research. In addition, a radial–radial–axial clearance rim seal (RRACS) is proposed to form a new stator–stator cavity to buff the ingestion flow. Numerical results show that the minimum mass flow rate for seal of the RRACS is 15.76% of the standard axial clearance rim seal.
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Sangan, Carl M., James A. Scobie, J. Michael Owen, Gary D. Lock, Kok Mun Tham, and Vincent P. Laurello. "Performance of a Finned Turbine Rim Seal." Journal of Turbomachinery 136, no. 11 (August 26, 2014). http://dx.doi.org/10.1115/1.4028116.
Full textAbstract:
In gas turbines, rim seals are fitted at the periphery of the wheel-space between the turbine disk and its adjacent casing; their purpose is to reduce the ingress of hot mainstream gases. A superposed sealant flow, bled from the compressor, is used to purge the wheel-space or at least dilute the ingress to an acceptable level. The ingress is caused by the circumferential variation of pressure in the turbine annulus radially outward of the seal. Engine designers often use double-rim seals where the variation in pressure is attenuated in the outer wheel-space between the two seals. This paper describes experimental results from a research facility that models an axial turbine stage with engine-representative rim seals. The radial variation of CO2 gas concentration, swirl, and pressure, in both the inner and outer wheel-space, are presented over a range of purge flow rates. The data are used to assess the performance of two seals: a datum double-rim seal and a derivative with a series of radial fins. The concept behind the finned seal is that the radial fins increase the swirl in the outer wheel-space; measurements of swirl show the captive fluid between the fins rotate with near solid body rotation. The improved attenuation of the pressure asymmetry, which governs the ingress, results in an improved performance of the inner geometry of the seal. The fins also increased the pressure in the outer wheel-space and reduced the ingress though the outer geometry of the seal.
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Lu, Xueliang, and Luis San Andrés. "Leakage and Rotordynamic Force Coefficients of A Three-Wave (Air in Oil) Wet Annular Seal: Measurements and Predictions." Journal of Engineering for Gas Turbines and Power 141, no. 3 (October 4, 2018). http://dx.doi.org/10.1115/1.4041270.
Full textAbstract:
In subsea environments, multiphase pumps and compressors add pressure to the process fluid, thus enabling long distance tie back systems that eliminate topside oil and gas separation stations. One challenge to construct a reliable multiphase pump or a reliable wet gas compressor is that the first must handle, without process upset, a mixture whose gas volume fraction (GVF) changes suddenly; while the other must remain stable while working with a liquid volume fraction (LVF) changing over long periods of time. The mixture GVF/LVF affects the static and dynamic forced performance of secondary flow components, namely seals, and which could lead to an increase in both rotor lateral or axial vibrations, thus compromising system reliability and availability. The current research is a planned endeavor toward developing seal configurations amenable to maintain rotor dynamic characteristics during changes in the contents of flow components. This paper extends prior work with uniform clearance annular seals and presents the static and dynamic forced performance of a three-wave surface annular seal designed to deliver a significant centering stiffness. The test element has length L = 43.4 mm, diameter D = 127 mm, and mean radial clearance cm=0.191 mm. At a shaft speed of 3.5 krpm (23 m/s surface speed), an air in ISO VG 10 oil mixture with an inlet GVF, 0 to 0.9, feeds the seal at 2.5 bara pressure and 37 °C temperature. The mixture mass flow rate decreases continuously with an increase in inlet GVF; shaft speed has little effect on it. Dynamic load tests serve to identify the seal dynamic force coefficients. The liquid seal (GVF = 0) shows frequency independent force coefficients. However, operation with a mixture produces stiffnesses that vary greatly with excitation frequency, in particular the direct one that hardens. The direct damping coefficients are not functions of frequency albeit dropping rapidly in magnitude as the GVF increases. The work also compares the performance of the wavy seal against those of two other seals: one with clearance equal to the mean clearance of the wavy seal, and the other with a large clearance emulating a fully worn wavy seal. The small clearance seal leaks 20% less than the wavy seal, whereas the leakage of the worn seal is twofold that of the wavy seal. For the three seals, the leakage normalized with respect to a pure liquid condition collapses into a single curve. The wavy seal produces the greatest direct stiffness and damping coefficients, whereas the worn seal produces the smallest force coefficients. Derived from a homogeneous mixture bulk flow model, predicted force coefficients for the three-wave seal match well with the test data for operation with a pure oil and an inlet GVF 0.2. For operation with GVF > 0.2, the discrepancy between the prediction and experimental data grows rapidly. The extensive test campaign reveals a wavy-surface seal offers a centering stiffness ability, a much desired feature in vertical submersible pumps that suffer from persistent static and dynamic stability issues.
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Nagai, Keisuke, Kazuki Koiso, Satoru Kaneko, Hiroo Taura, and Yusuke Watanabe. "Numerical and Experimental Analyses of Static and Dynamic Characteristics for Partially Helically Grooved Liquid Annular Seals." Journal of Tribology 141, no. 2 (September 17, 2018). http://dx.doi.org/10.1115/1.4040574.
Full textAbstract:
Numerical and experimental analyses of the static and dynamic characteristics of the liquid annular seals with axially partial helical grooves were conducted to investigate the effects of the axial length gal of a helically grooved section in a seal stator. The numerical solution and experimental procedures were applied in the same manner as in previous studies on through-helically grooved seals, wherein the grooves extend across the seal length. The numerical results qualitatively agreed with the experimental results, demonstrating the validity of the numerical analysis. The leakage flow rate Q was lower in the partially helically grooved seals than that of conventional through-helically grooved seals across a small range of rotor spinning velocities. In contrast, the reduction in Q due to the pumping effect caused by the spin of the rotor diminished with the decrease in gal. For a small concentric whirling motion of the rotor, the radial dynamic reaction force Fr and magnitude of variation in the tangential dynamic reaction force Ft with the whirling angular velocity increased with the decrease in gal, and their values approached the corresponding values for the smooth-surface seal. Under the same rotor whirling velocity, the Ft for the partially helically grooved seals became lower than that for the smooth-surface seal (similar to the case for the through-helically grooved seal), although decreasing gal tended to increase Ft. These results suggest that partially helically grooved seals can improve the efficiency and stability margin of the pumps because of the reduction in leakage flow rate and suppression of the rotor forward whirling motion (with large radial and tangential dynamic reaction forces) as compared to conventional through-helically grooved seals.
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Alex Moreland, J., Dara W. Childs, and Joshua T. Bullock. "Measured Static and Rotordynamic Characteristics of a Smooth-Stator/Grooved-Rotor Liquid Annular Seal." Journal of Fluids Engineering 140, no. 10 (August 6, 2018). http://dx.doi.org/10.1115/1.4040762.
Full textAbstract:
Electric submersible pumps (ESPs) utilize grooved-rotor/smooth-stator (SS/GR) seals to reduce leakage and break up contaminants within the pumped fluid. Additionally, due to their decreased surface area (when compared to a smooth seal), grooved seals decrease the chance of seizure in the case of rotor-stator rubs. Despite their use in industry, the literature does not contain rotordynamic measurements for smooth-stator/circumferentially grooved-rotor liquid annular seals. This paper presents test results consisting of leakage measurements and rotordynamic coefficients for a SS/GR liquid annular sdeal. Both static and dynamic variables are investigated for various imposed preswirl ratios (PSRs), static eccentricity ratios (0–0.8), axial pressure drops (2–8 bars), and running speeds (2–8 krpm). The seals' static and dynamic features are compared to those of a smooth seal with the same length, diameter, and minimum radial clearance. Results show that the grooves reduce leakage at lower speeds (less than 5 krpm) and higher axial pressure drops, but does little at higher speeds. The grooved seal's direct stiffness is generally negative, which would be detrimental to pump rotordynamics. As expected, increasing preswirl increases the magnitude of cross-coupled stiffness and increases the whirl frequency ratio (WFR). When compared to the smooth seal, the grooved seal has smaller effective damping coefficients, indicative of poorer stability characteristics.