The Experts below are selected from a list of 2499 Experts worldwide ranked by ideXlab platform
Izhak Etsion - One of the best experts on this subject based on the ideXlab platform.
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stiffness and efficiency optimization of a hydrostatic laser surface textured Gas Seal
Journal of Tribology-transactions of The Asme, 2007Co-Authors: Y. Feldman, Yuri Kligerman, Izhak EtsionAbstract:Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic Gas-lubricated mechanical Seals. This is achieved by applying microdimples with high area density over a certain portion of the Sealing dam width adjacent to the high-pressure side, leaving the remaining portion untextured. The textured portion provides an equivalent larger gap that results in converging clearance in the direction of pressure drop and hence, hydrostatic pressure buildup, similar to that of a radial step Seal. A mathematical model based on the solution of the Reynolds equation for compressible Newtonian fluid in a narrow gap between two nominally parallel stationary surfaces is developed. A detailed dimensionless analysis of the texturing parameters is performed to achieve maximum Gas film stiffness with minimum Gas leakage. DOI: 10.1115/1.2540120
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A Hydrostatic Laser Surface Textured Gas Seal
Tribology Letters, 2006Co-Authors: Y. Feldman, Yuri Kligerman, Izhak EtsionAbstract:A theoretical model is developed to study the effect of partial laser surface texturing (LST) on a hydrostatic Gas Seal. The partial LST provides a mechanism for hydrostatic pressure build up in the Sealing dam similar to that of a radial step. The surface texturing parameters are numerically optimized to obtain maximum efficiency in terms of the ratio of load carrying capacity over Gas leakage. The performance of the optimum partial LST Seal compares favorably with that of a radial step Seal.
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Near-Contact Laser Surface Textured Dry Gas Seals
Journal of Tribology-transactions of The Asme, 2004Co-Authors: A. D. Mcnickle, Izhak EtsionAbstract:A new concept of a near-contact Gas Seal is experimentally investigated. A simulated Gas face Seal for a high-speed Gas turbine engine is used for the investigation. A baseline conventional contacting-type Seal is compared with an identical Seal that was laser surface textured (LST) to turn it into a near-contact Gas Seal. Results show the potential benefits of the new concept in terms of smoother running, lower friction torque, and lower face temperature at 12,000 RPM over a range of face loading.
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analysis of the hydrodynamic effects in a surface textured circumferential Gas Seal
Tribology Transactions, 2001Co-Authors: Yuri Kligerman, Izhak EtsionAbstract:A theoretical finite-element model was developed to study the hydrodynamic effect of micro-pores generated by laser surface texturing (LST) in a circumferential Gas Seal. The Seal is represented by two non-contacting annular surfaces of a rotating shaft and a stationary ring. The micro-pores of spherical segment shape are distributed uniformly over one of the annular surfaces. The hydrodynamic dimensionless pressure distribution in the uniform clearance between the annular surfaces is obtained from a solution of the Reynolds equation for compressible viscous Gas in a laminar flow. Results of a parametric study along with a numerical example for a specific circumferential Seal demonstrate a substantial hydrodynamic effect that can raise the opening average pressure in the Seal clearance above the ambient one by up to 50 percent. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
Dara W Childs - One of the best experts on this subject based on the ideXlab platform.
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static and rotordynamic characteristics for a new hole pattern annular Gas Seal design incorporating larger diameter holes
ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, 2012Co-Authors: Michael Vannarsdall, Dara W ChildsAbstract:To reduce manufacturing cost and time, a new larger-diameter hole-pattern Seal incorporating hole diameters of 12.27 mm, versus prior hole diameters of 3.175 mm has been proposed. The 12.27 mm hole-diameter Seal had substantially better stability performance with higher effective damping and a markedly lower cross-over frequency. It had negative direct stiffness coefficients at low frequency, while the 3.175 mm hole-diameter Seal did not.Copyright © 2012 by ASME
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measurement versus predictions of rotordynamic coefficients of a hole pattern Gas Seal with negative preswirl
ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, 2012Co-Authors: Philip D. Brown, Dara W ChildsAbstract:Test results are presented for rotordynamic coefficients of a hole-pattern annular Gas Seals at supply pressures to 84 bar and running speeds to 20,200 RPM. The principal test variable of interest was negative preswirl. Preswirl signifies the circumferential fluid flow entering a Seal, and negative preswirl indicates a fluid swirl in a direction opposite to rotor rotation. The influences of pressure ratio and rotor speed were also investigated. Measured results produce direct and cross-coupled stiffness and damping coefficients that are a function of excitation frequency Ω.Changes in pressure ratio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the mid-range of Ω values.Increasing rotor speed significantly increased cross-coupled stiffness and cross-coupled damping. At 10,200 RPM, high negative inlet preswirl produced negative cross-coupled stiffness over an excitation frequency range of 200–250 Hz. Negative preswirl did not affect direct stiffness and damping coefficients.Effective damping combines the stabilizing effect of direct damping and the destabilizing effect of cross-coupled stiffness. The cross-over frequency is the precession frequency where effective damping transitions from a negative value to a positive value with increasing frequency. At 20,200 RPM with a pressure ratio of 50%, peak effective damping was increased by 50%, and the cross-over frequency was reduced by 50% for high-negative preswirl versus zero preswirl. Hence, reverse swirl can greatly enhance the stabilizing capacity of hole-pattern balance-piston or division-wall Seals for compressors.A two-control-volume model that uses the ideal Gas law at constant temperature was used to predict rotordynamic coefficients. The model predicted direct rotordynamic coefficients well, but substantially under predicted cross-coupled rotordynamic coefficients especially at high negative preswirls.© 2012 ASME
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Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl
Journal of Engineering for Gas Turbines and Power, 2012Co-Authors: Philip D. Brown, Dara W ChildsAbstract:Test results are presented for the rotordynamic coefficients of a hole-pattern annular Gas Seal at supply pressures to 84 bar and running speeds to 20200 rpm. The principal test variable of interest was negative preswirl. Preswirl signifies the circumferential fluid flow entering a Seal and negative preswirl indicates a fluid swirl in a direction opposite to rotor rotation. The influences of the pressure ratio and rotor speed were also investi- gated. The measured results produce direct and cross-coupled stiffness and damping coefficients that are a function of the excitation frequency X. Changes in the pressure ra- tio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the midrange of X values. Increasing rotor speed significantly increased the cross-coupled stiffness and cross-coupled damping. At 10,200 RPM, high negative inlet preswirl produced negative cross-coupled stiffness over an excitation frequency range of 200–250 Hz. Negative preswirl did not affect the direct stiffness and damping coefficients. Effective damping combines the stabilizing effect of direct damping and the destabilizing effect of cross-coupled stiffness. The crossover fre- quency is the precession frequency where effective damping transitions from a negative value to a positive value with increasing frequency. At 20,200 rpm with a pressure ratio of 50%, the peak effective damping was increased by 50%, and the crossover frequency was reduced by 50% for high-negative preswirl versus zero preswirl. Hence, reverse swirl can greatly enhance the stabilizing capacity of a hole-pattern balance-piston or division-wall Seals for compressors. A two-control-volume model that uses the ideal Gas law at constant temperature was used to predict rotordynamic coefficients. The model predicted direct rotordynamic coefficients well, however, substantially under- predicted cross-coupled rotordynamic coefficients, especially at high negative preswirls
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Rotordynamic-Coefficient and Leakage Characteristics for Hole-Pattern-Stator Annular Gas Seals—Measurements Versus Predictions
Journal of Tribology, 2004Co-Authors: Dara W Childs, Jonathan WadeAbstract:Selected test results are presented for an annular Gas Seal using a smooth rotor and a hole-pattern-roughness stator for a supply pressure of 70 bar, three pressure ratios, three speeds up to 20,000 rpm, two clearances, and three preswirl ratios. Dynamic data include frequency-dependent direct and cross-coupled stiffness and damping coefficients. Static data include leakage and upstream and downstream pressures and temperatures. Very good agreements are found between measurements and predictions from a two-control-volume bulk-flow model.
Jonathan Wade - One of the best experts on this subject based on the ideXlab platform.
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Rotordynamic-Coefficient and Leakage Characteristics for Hole-Pattern-Stator Annular Gas Seals—Measurements Versus Predictions
Journal of Tribology, 2004Co-Authors: Dara W Childs, Jonathan WadeAbstract:Selected test results are presented for an annular Gas Seal using a smooth rotor and a hole-pattern-roughness stator for a supply pressure of 70 bar, three pressure ratios, three speeds up to 20,000 rpm, two clearances, and three preswirl ratios. Dynamic data include frequency-dependent direct and cross-coupled stiffness and damping coefficients. Static data include leakage and upstream and downstream pressures and temperatures. Very good agreements are found between measurements and predictions from a two-control-volume bulk-flow model.
Yuanjian Xu - One of the best experts on this subject based on the ideXlab platform.
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A new system design for supercritical water oxidation
Chemical Engineering Journal, 2015Co-Authors: Zhong Chen, Fengjun Yin, Hongzhen Chen, Guangwei Wang, Yuanjian XuAbstract:As the main obstacles for the industrialization of supercritical water oxidation (SCWO) technology, corrosion and plugging are mostly occurring in the high pressure high temperature (HPHT) sections, including preheater, reactor, heat exchanger and cooler. In this paper, a lab-scale SCWO system based on dynamic Gas Seal wall reactor (DGSWR) has been described, tested and discussed in detail. The results showed that the preheating problems of waste with high solid content has been solved and the "Gas Seal" of DGSWR has been successfully verified under 28-29. MPa and around 400. °C. Sewage sludge with 2.62-11.78% dry solid has been degraded and the COD removal efficiency can reach up to 99.15%. However, the solid particle sedimentation was only partly achieved. According to the results analysis, based on the Stokes' Law, both small particle size and counter-current of upward reaction medium and downward solids are responsible. Future improvements for the SCWO system were also discussed at the end of this article.
Pengyun Song - One of the best experts on this subject based on the ideXlab platform.
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the performance of spiral groove dry Gas Seal under choked flow condition considering the real Gas effect
Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2020Co-Authors: Hengjie Xu, Pengyun Song, Qiangguo DengAbstract:By taking carbon dioxide and hydrogen as lubricating Gas, respectively, this paper presents an analysis on the pressure characteristics and temperature distribution of spiral groove dry Gas Seal wh...
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Analysis of performance of spiral groove dry Gas Seal considered effects of both real Gas and slip flow
Huagong Xuebao CIESC Journal, 2016Co-Authors: Pengyun Song, Shuai Zhang, Hengjie XuAbstract:© All Right Reserved. In order to analyze the performance of the spiral groove dry Gas Seal considered effects of both real Gas and slip flow simultaneously, the modified pressure governing equations of the Seal based on the narrow groove theory by taking the effective viscosity coefficient instead of the Gas dynamic viscosity and the real Gas Virial state equation instead of the ideal Gas state equation. N 2 , H 2 , CO 2 were taken as examples. The leakage, the pressure at groove root radius and the opening force of the Seal were calculated. Meanwhile, the leakage, the pressure at groove root radius and the opening force under the condition of ideal Gas without slip flow, ideal Gas with slip flow, real Gas without slip flow and real Gas with slip flow were compared, respectively. The results showed that the effect of slip flow made the leakage increase, and the pressure at groove root radius and the opening force decrease. The effect of real Gas made the leakage, the pressure at groove root radius and opening force of susceptible compressed Gas (Z < 1) increase whereas the leakage, the pressure at groove root and opening force of non-susceptible compressed Gas (Z > 1) decrease. With increasing Sealed pressure p o , the effect of slip flow was reduced, while that of the real Gas was strengthened. Under the condition of low Sealed pressure, the slip flow effect was significant. On the contrary, the real Gas effect played a predominant role under the condition of high Sealed pressure.
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the liquid condensation conditions in the dry Gas Seal system
Applied Mechanics and Materials, 2015Co-Authors: Pengyun SongAbstract:Dry Gas Seal is often used as the Seal devices in centrifugal compressor and other high-speed rotating equipment, which requires Seal Gas clean and dry. If there is some liquid in the Seal Gas, the dry Gas Seal will rapidly fail. When the Seal Gas flows through the filters, valves, orifices, Seal faces and so on, the Gas temperature will decrease resulted from the Joule- Thomson effect. If the Gas temperature is lower than the corresponding dew point, there will be liquid condensation in dry Gas Seal system. Wet air is taken as an example to show how to calculate the pressure and temperature relationship when it is adiabatic expansion. Dew point lines at different conditions are calculated by considering the vapor-liquid equilibrium. Liquid condensation conditions are acquired by comparing expansion lines and dew point lines, and the factors of influencing liquid condensation were analyzed. The results shows that decreasing Gas humidity, increasing the Gas temperature can effectively reduce the liquid condensation.
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Theoretic Analysis of the Effect of Real Gas on the Performance of the T-Groove and Radial Groove Dry Gas Seal
Applied Mechanics and Materials, 2012Co-Authors: Xiao Peng Hu, Pengyun SongAbstract:Dry Gas Seal is a kind of non-contact Seal in which Gas dynamic and static pressure forming opening force, being with less Gas leakage and longer using time. Generally speaking, the Gas performance of the dry Gas Seal is regarded as an ideal Gas when the dry Gas Seal is investigated, designed, and operated. However, some real Gas performance may be quite different from the ideal Gas when the Gas pressure is high. Some Gases, such as carbon dioxide, hydrogen and nitrogen, are considered, both the T-groove dry Gas Seal and the radial groove dry Gas Seal are analyzed. The virial equation of state is used to express real Gas performance, and the effect of real Gas on the performance of dry Gas Seal is analyzed. The results show the maximum relative of opening force error is -4.98% and the maximum relative error of leakage is -20.11% for carbon dioxide; the maximum relative error of opening force is -0.46% and the maximum relative error of leakage is 2.47% for hydrogen; the maximum relative error of opening force is -0.04%, and the maximum relative error of leakage is -0.16% for nitrogen. So the effects of real Gas of carbon dioxide and hydrogen have much influence on the performance of the dry Seal; but the nitrogen has less influence on the performance of the dry Seal.
