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Dara W Childs - One of the best experts on this subject based on the ideXlab platform.
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measured rotordynamic and leakage characteristics of a tooth on rotor Labyrinth Seal with comparisons to a tooth on stator Labyrinth Seal and predictions
ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, 2015Co-Authors: Stephen P Arthur, Dara W ChildsAbstract:Rotordynamic and leakage data are presented for a see-through tooth-on-rotor (TOR) Labyrinth Seal with comparisons to a see-through tooth-on-stator (TOS) Labyrinth Seal. Measurements for both Seals are also compared to predictions from XLLaby. Both Seals have identical diameter and can be considered as relatively long Labyrinth Seals. The TOR Seal has a length-to-diameter ratio of 0.62, whereas the TOS Seal is longer and has a length-to-diameter ratio of 0.75. Both Seals also differ by number of teeth, tooth height, and tooth cavity length. TOR Labyrinth tests were carried out at an inlet pressure of 70 bar-a (1,015 psia), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds up to 20,200 rpm, a radial clearance of 0.1 mm (4 mils), and three preswirl ratios. For comparison, TOS Labyrinth tests were run at identical conditions as the TOR tests but for only one positive preswirl ratio.TOR Labyrinth measurements show a pronounced dependence of rotordynamic coefficients on rotor speed, especially when compared to prior documented TOS Labyrinth Seal tests run at a radial clearance of 0.2 mm (8mils). The TOR Labyrinth cross-coupled stiffness is higher in magnitude and increases at a higher rate than that of the TOS Labyrinth across all test speeds. However, the TOR Labyrinth effective damping was determined to be greater due to higher measurements of direct damping. Measured leakage rates for the TOR Labyrinth were approximately 5–10% less than the TOS Labyrinth. XLLaby underpredicted the rotordynamic coefficients for both Seals. However, as with measurements, it predicted the TOR Labyrinth to have higher effective damping than the TOS Labyrinth.Copyright © 2015 by ASME
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measured comparison of leakage and rotordynamic characteristics for a slanted tooth and a straight tooth Labyrinth Seal
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013Co-Authors: Naitik J. Mehta, Dara W ChildsAbstract:Measured results are presented to compare rotordynamic coefficients and leakage of a slanted-tooth Labyrinth Seal and a straight-tooth Labyrinth Seal. Both Seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slanted-tooth Labyrinth was 65° from the normal axis. Experiments were carried out at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2 mm (8 mils). One zero and two positive inlet preswirl ratios were used.The results show only minute difference in the rotordynamic coefficients between the two Seals. The slanted-tooth Labyrinth Seal consistently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulk-flow model (1CVM) which was developed for a straight-tooth Labyrinth Seal design. 1CVM under-predicted the rotordynamic coefficients and the leakage.Copyright © 2013 by ASME
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Measured Comparison of Leakage and Rotordynamic Characteristics for a Slanted-Tooth and a Straight-Tooth Labyrinth Seal
Journal of Engineering for Gas Turbines and Power, 2013Co-Authors: Naitik J. Mehta, Dara W ChildsAbstract:Measured results are presented to compare rotordynamic coefficients and leakage of a slanted-tooth Labyrinth Seal and a straight-tooth Labyrinth Seal. Both Seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slanted- tooth Labyrinth was 65 deg from the normal axis. Experiments were carried out at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2mm (8 mils). One zero and two positive inlet preswirl ratios were used. The results show only minute difference in the rotordynamic coefficients between the two Seals. The slanted-tooth Labyrinth Seal consis- tently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulk-flow model (1CVM) which was developed for a straight-tooth Labyrinth Seal design. 1CVM under-predicted the rotordynamic coefficients and the leakage.
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Predicted Rotordynamic Behavior of a Labyrinth Seal as Rotor Surface Speed Approaches Mach 1
Journal of Engineering for Gas Turbines and Power, 2010Co-Authors: Manish R. Thorat, Dara W ChildsAbstract:Prior one-control-volume (1CV) models for rotor-fluid interaction in Labyrinth Seals pro- duce synchronously reduced (at running speed), frequency-independent stiffness and damping coefficients. The 1CV model, consisting of a leakage equation, a continuity equation, and a circumferential-momentum equation (for each cavity), was stated to be invalid for rotor surface speeds approaching the speed of sound. However, the present results show that while the 1CV fluid-mechanic model continues to be valid, the calcu- lated rotordynamic coefficients become strongly dependent on the rotor’s precession fre- quency. A solution is developed for the reaction-force components for a range of preces- sion frequencies, producing frequency-dependent stiffness and damping coefficients. They can be used to define a Laplace-domain transfer-function model for the reaction-force/ rotor-motion components. Calculated results are presented for a simple Jeffcott rotor model acted on by a Labyrinth Seal. The model’s undamped natural frequency is 7.6 krpm. The fluid properties, Seal radius Rs, and running speed ? cause the rotor surface velocity Rs ? to equal the speed of sound c0 at ?? 58 krpm. Calculated synchronous-response results due to imbalance coincide for the synchronously reduced and the frequency- dependent models. For an inlet preswirl ratio of 0.5, both models predict the same log-dec out to ? ? 14.5 krpm. The synchronously reduced model predicts an onset speed of instability (OSI) at 10 krpm, but a return to stability at 48 krpm, with subsequent increases in log-dec out to 70 krpm. The frequency-dependent model predicts an OSI of 10 krpm and no return to stability out to 70 krpm. The frequency-dependent models predict small changes in the rotor’s damped natural frequencies. The synchronously reduced model predicts large changes. The stability-analysis results show that a frequency-dependent Labyrinth Seal model should be used if the rotor surface speed approaches a significant fraction of the speed of sound. For the present example, observ- able discrepancies arose when Rs ?? 0.26c0.
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predicted rotordynamic behavior of a Labyrinth Seal as rotor surface speed approaches mach 1
ASME Turbo Expo 2009: Power for Land Sea and Air, 2009Co-Authors: Manish R. Thorat, Dara W ChildsAbstract:Prior one-control-volume (1CV) models for rotor-fluid interaction in Labyrinth Seals produce synchronously-reduced (at running-speed), frequency-independent stiffness and damping coefficients. The 1CV model, consisting of a leakage equation, a continuity equation, and a circumferential-momentum equation (for each cavity) was stated to be invalid for rotor surface speeds approaching the speed of sound. However, the present results show that, while the 1CV fluid-mechanic model continues to be valid, the calculated rotordynamic coefficients become strongly frequency dependent. A solution is developed for the reaction-force components for a range of precession frequencies, producing frequency-dependent stiffness and damping coefficients. They can be used to define a Laplace-domain transfer-function model for the reaction-force/rotor-motion components. Calculated rotordynamic results are presented for a simple Jeffcott rotor acted on by a Labyrinth Seal. The Seal radius Rs and running speed ω cause the rotor surface velocity Rs ω to equal the speed of sound c0 at ω = 58 krpm. Calculated synchronous-response results due to imbalance coincide for the synchronously-reduced and the frequency-dependent models. For an inlet preswirl ratio of 0.5, both models predict the same log decs out to ω≈14.5 krpm. The synchronously-reduced model predicts an onset speed of instability (OSI) at 15 krpm, but a return to stability at 45 krpm, with subsequent increases in log dec out to 65 krpm. The frequency-dependent model predicts an OSI of 65 krpm. The frequency-dependent models predict small changes in the rotor’s damped natural frequencies. The synchronously-reduced model predicts large changes. The stability-analysis results show that a frequency-dependent Labyrinth Seal model should be used if the rotor surface speed approaches a significant fraction of the speed of sound. For the present example, observable discrepancies arose when Rs ω = 0.26 c0 .© 2009 ASME
Corentin Delebarre - One of the best experts on this subject based on the ideXlab platform.
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High speed interaction between an abradable coating and a Labyrinth Seal in turbo-engine application
2020Co-Authors: Corentin Delebarre, Vincent Wagner, Jean-yves Paris, Gilles Dessein, Jean Denape, Julien Gurt-santanachAbstract:The design of gas turbine aims to enhance the engine efficiency by developing new materials able to work at higher temperatures, or to promote new technologies, fuel management and airflow direction. One solution is the reduction of clearance between rotary parts in turbomachinery air systems. This clearance reduction causes direct interactions in the secondary air system of a turbo-engine when a rotary Seal, called Labyrinth Seal, rubs on the turbo-engine as a result of successive starts and stops, thermal expansions and vibrations. The purpose of the present paper is to study interaction phenomena between an abradable material (Al-Si 6%) and a nickel alloy (718 alloy) during high speed contacts. A high speed test rig has been designed to simulate interactions between Labyrinth Seals and abradable coatings in similar operating conditions of turbo-engine in terms of geometries, rotational and linear velocities. A series of experiments has been carried out in order to get a first assessment under different turbo-engine operating conditions. Experimental results are presented using visual observations of test samples, quantitative approaches of interacting forces and micrographic observations. This work provides new basic data for a preliminary study of the interaction between a Labyrinth Seal teeth tips and its casing for turbo-engine applications.
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an experimental study of the high speed interaction between a Labyrinth Seal and an abradable coating in a turbo engine application
Wear, 2014Co-Authors: Corentin Delebarre, Vincent Wagner, Jean-yves Paris, Gilles Dessein, Jean Denape, Julien GurtsantanachAbstract:A new high-speed test rig was designed to simulate the interactions between Labyrinth Seals and abradable coatings in similar turbo-engine operating conditions. To determine a solution for turbo-engine efficiency enhancement, we investigated the clearance reduction between the rotary parts in air systems, the successive starts and stops, the thermal expansion and the vibrations that might cause direct rub interactions between a rotary Seal, known as a Labyrinth Seal, and a turbo-engine housing coated with a sacrificial abradable material. High interaction speeds from 0 to 130 m s−1 were obtained using a 5-axis milling machine fitted with a unique magnetic bearings spindle developed specifically for the study. The purpose of this paper is to study the interaction phenomena between an abradable material (Al–Si 6%) and a nickel alloy (Alloy 718) to obtain a first contact assessment under different turbo-engine operating conditions. The experimental results are first presented by visual observations of the posttest samples, as specified by accurate profile measurements. A quantitative approach to the interaction forces recorded during the tests and micrographic observations complete the preliminary study. This work provides new basic data for a preliminary study of the interaction between Labyrinth Seal teeth tips and abradable coatings in turbo-engine applications.
Naitik J. Mehta - One of the best experts on this subject based on the ideXlab platform.
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measured comparison of leakage and rotordynamic characteristics for a slanted tooth and a straight tooth Labyrinth Seal
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2013Co-Authors: Naitik J. Mehta, Dara W ChildsAbstract:Measured results are presented to compare rotordynamic coefficients and leakage of a slanted-tooth Labyrinth Seal and a straight-tooth Labyrinth Seal. Both Seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slanted-tooth Labyrinth was 65° from the normal axis. Experiments were carried out at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2 mm (8 mils). One zero and two positive inlet preswirl ratios were used.The results show only minute difference in the rotordynamic coefficients between the two Seals. The slanted-tooth Labyrinth Seal consistently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulk-flow model (1CVM) which was developed for a straight-tooth Labyrinth Seal design. 1CVM under-predicted the rotordynamic coefficients and the leakage.Copyright © 2013 by ASME
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Measured Comparison of Leakage and Rotordynamic Characteristics for a Slanted-Tooth and a Straight-Tooth Labyrinth Seal
Journal of Engineering for Gas Turbines and Power, 2013Co-Authors: Naitik J. Mehta, Dara W ChildsAbstract:Measured results are presented to compare rotordynamic coefficients and leakage of a slanted-tooth Labyrinth Seal and a straight-tooth Labyrinth Seal. Both Seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slanted- tooth Labyrinth was 65 deg from the normal axis. Experiments were carried out at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2mm (8 mils). One zero and two positive inlet preswirl ratios were used. The results show only minute difference in the rotordynamic coefficients between the two Seals. The slanted-tooth Labyrinth Seal consis- tently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulk-flow model (1CVM) which was developed for a straight-tooth Labyrinth Seal design. 1CVM under-predicted the rotordynamic coefficients and the leakage.
Julien Gurtsantanach - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the high speed interaction between a Labyrinth Seal and an abradable coating in a turbo engine application
Wear, 2014Co-Authors: Corentin Delebarre, Vincent Wagner, Jean-yves Paris, Gilles Dessein, Jean Denape, Julien GurtsantanachAbstract:A new high-speed test rig was designed to simulate the interactions between Labyrinth Seals and abradable coatings in similar turbo-engine operating conditions. To determine a solution for turbo-engine efficiency enhancement, we investigated the clearance reduction between the rotary parts in air systems, the successive starts and stops, the thermal expansion and the vibrations that might cause direct rub interactions between a rotary Seal, known as a Labyrinth Seal, and a turbo-engine housing coated with a sacrificial abradable material. High interaction speeds from 0 to 130 m s−1 were obtained using a 5-axis milling machine fitted with a unique magnetic bearings spindle developed specifically for the study. The purpose of this paper is to study the interaction phenomena between an abradable material (Al–Si 6%) and a nickel alloy (Alloy 718) to obtain a first contact assessment under different turbo-engine operating conditions. The experimental results are first presented by visual observations of the posttest samples, as specified by accurate profile measurements. A quantitative approach to the interaction forces recorded during the tests and micrographic observations complete the preliminary study. This work provides new basic data for a preliminary study of the interaction between Labyrinth Seal teeth tips and abradable coatings in turbo-engine applications.
Manish R. Thorat - One of the best experts on this subject based on the ideXlab platform.
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Predicted Rotordynamic Behavior of a Labyrinth Seal as Rotor Surface Speed Approaches Mach 1
Journal of Engineering for Gas Turbines and Power, 2010Co-Authors: Manish R. Thorat, Dara W ChildsAbstract:Prior one-control-volume (1CV) models for rotor-fluid interaction in Labyrinth Seals pro- duce synchronously reduced (at running speed), frequency-independent stiffness and damping coefficients. The 1CV model, consisting of a leakage equation, a continuity equation, and a circumferential-momentum equation (for each cavity), was stated to be invalid for rotor surface speeds approaching the speed of sound. However, the present results show that while the 1CV fluid-mechanic model continues to be valid, the calcu- lated rotordynamic coefficients become strongly dependent on the rotor’s precession fre- quency. A solution is developed for the reaction-force components for a range of preces- sion frequencies, producing frequency-dependent stiffness and damping coefficients. They can be used to define a Laplace-domain transfer-function model for the reaction-force/ rotor-motion components. Calculated results are presented for a simple Jeffcott rotor model acted on by a Labyrinth Seal. The model’s undamped natural frequency is 7.6 krpm. The fluid properties, Seal radius Rs, and running speed ? cause the rotor surface velocity Rs ? to equal the speed of sound c0 at ?? 58 krpm. Calculated synchronous-response results due to imbalance coincide for the synchronously reduced and the frequency- dependent models. For an inlet preswirl ratio of 0.5, both models predict the same log-dec out to ? ? 14.5 krpm. The synchronously reduced model predicts an onset speed of instability (OSI) at 10 krpm, but a return to stability at 48 krpm, with subsequent increases in log-dec out to 70 krpm. The frequency-dependent model predicts an OSI of 10 krpm and no return to stability out to 70 krpm. The frequency-dependent models predict small changes in the rotor’s damped natural frequencies. The synchronously reduced model predicts large changes. The stability-analysis results show that a frequency-dependent Labyrinth Seal model should be used if the rotor surface speed approaches a significant fraction of the speed of sound. For the present example, observ- able discrepancies arose when Rs ?? 0.26c0.
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predicted rotordynamic behavior of a Labyrinth Seal as rotor surface speed approaches mach 1
ASME Turbo Expo 2009: Power for Land Sea and Air, 2009Co-Authors: Manish R. Thorat, Dara W ChildsAbstract:Prior one-control-volume (1CV) models for rotor-fluid interaction in Labyrinth Seals produce synchronously-reduced (at running-speed), frequency-independent stiffness and damping coefficients. The 1CV model, consisting of a leakage equation, a continuity equation, and a circumferential-momentum equation (for each cavity) was stated to be invalid for rotor surface speeds approaching the speed of sound. However, the present results show that, while the 1CV fluid-mechanic model continues to be valid, the calculated rotordynamic coefficients become strongly frequency dependent. A solution is developed for the reaction-force components for a range of precession frequencies, producing frequency-dependent stiffness and damping coefficients. They can be used to define a Laplace-domain transfer-function model for the reaction-force/rotor-motion components. Calculated rotordynamic results are presented for a simple Jeffcott rotor acted on by a Labyrinth Seal. The Seal radius Rs and running speed ω cause the rotor surface velocity Rs ω to equal the speed of sound c0 at ω = 58 krpm. Calculated synchronous-response results due to imbalance coincide for the synchronously-reduced and the frequency-dependent models. For an inlet preswirl ratio of 0.5, both models predict the same log decs out to ω≈14.5 krpm. The synchronously-reduced model predicts an onset speed of instability (OSI) at 15 krpm, but a return to stability at 45 krpm, with subsequent increases in log dec out to 65 krpm. The frequency-dependent model predicts an OSI of 65 krpm. The frequency-dependent models predict small changes in the rotor’s damped natural frequencies. The synchronously-reduced model predicts large changes. The stability-analysis results show that a frequency-dependent Labyrinth Seal model should be used if the rotor surface speed approaches a significant fraction of the speed of sound. For the present example, observable discrepancies arose when Rs ω = 0.26 c0 .© 2009 ASME
