Les Inscriptions à la Bibliothèque sont ouvertes en
ligne via le site: https://biblio.enp.edu.dz
Les Réinscriptions se font à :
• La Bibliothèque Annexe pour les étudiants en
2ème Année CPST
• La Bibliothèque Centrale pour les étudiants en Spécialités
A partir de cette page vous pouvez :
| Retourner au premier écran avec les recherches... |
Détail de l'auteur
Auteur Ryu, Keun
Documents disponibles écrits par cet auteur
Affiner la rechercheEffect of cooling flow on the operation of a hotrotor-gas foil bearing system / Ryu, Keun in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 10 (Octobre 2012)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 10 (Octobre 2012) . - 12 p.
Titre : Effect of cooling flow on the operation of a hotrotor-gas foil bearing system Type de document : texte imprimé Auteurs : Ryu, Keun, Auteur ; Luis San Andrés, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : gas turbines Langues : Anglais (eng) Mots-clés : gas foil bearings; cooling flow streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas foil bearings (GFBs) operating at high temperature rely on thermal management procedures that supply needed cooling flow streams to keep the bearing and rotor from overheating. Poor thermal management not only makes systems inefficient and costly to operate but could also cause bearing seizure and premature system destruction. This paper presents comprehensive measurements of bearing temperatures and shaft dynamics conducted on a hollow rotor supported on two first generation GFBs. The hollow rotor (1.36 kg, 36.51 mm OD and 17.9 mm ID) is heated from inside to reach an outer surface temperature of 120 °C. Experiments are conducted with rotor speeds to 30 krpm and with forced streams of air cooling the bearings and rotor. Air pressurization in an enclosure at the rotor mid span forces cooling air through the test GFBs. The cooling effect of the forced external flows is most distinct when the rotor is hottest and operating at the highest speed. The temperature drop per unit cooling flow rate significantly decreases as the cooling flow rate increases. Further measurements at thermal steady state conditions and at constant rotor speeds show that the cooling flows do not affect the amplitude and frequency contents of the rotor motions. Other tests while the rotor decelerates from 30 krpm to rest show that the test system (rigid-mode) critical speeds and modal damping ratio remain nearly invariant for operation with increasing rotor temperatures and with increasing cooling flow rates. Computational model predictions reproduce the test data with accuracy. The work adds to the body of knowledge on GFB performance and operation and provides empirically derived guidance for successful rotor-GFB system integration. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000010 [...] [article] Effect of cooling flow on the operation of a hotrotor-gas foil bearing system [texte imprimé] / Ryu, Keun, Auteur ; Luis San Andrés, Auteur . - 2012 . - 12 p.
gas turbines
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 10 (Octobre 2012) . - 12 p.
Mots-clés : gas foil bearings; cooling flow streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas foil bearings (GFBs) operating at high temperature rely on thermal management procedures that supply needed cooling flow streams to keep the bearing and rotor from overheating. Poor thermal management not only makes systems inefficient and costly to operate but could also cause bearing seizure and premature system destruction. This paper presents comprehensive measurements of bearing temperatures and shaft dynamics conducted on a hollow rotor supported on two first generation GFBs. The hollow rotor (1.36 kg, 36.51 mm OD and 17.9 mm ID) is heated from inside to reach an outer surface temperature of 120 °C. Experiments are conducted with rotor speeds to 30 krpm and with forced streams of air cooling the bearings and rotor. Air pressurization in an enclosure at the rotor mid span forces cooling air through the test GFBs. The cooling effect of the forced external flows is most distinct when the rotor is hottest and operating at the highest speed. The temperature drop per unit cooling flow rate significantly decreases as the cooling flow rate increases. Further measurements at thermal steady state conditions and at constant rotor speeds show that the cooling flows do not affect the amplitude and frequency contents of the rotor motions. Other tests while the rotor decelerates from 30 krpm to rest show that the test system (rigid-mode) critical speeds and modal damping ratio remain nearly invariant for operation with increasing rotor temperatures and with increasing cooling flow rates. Computational model predictions reproduce the test data with accuracy. The work adds to the body of knowledge on GFB performance and operation and provides empirically derived guidance for successful rotor-GFB system integration. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000010 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 3 (Mars 2011) . - 09 p.
Titre : Identification of structural stiffness and energy dissipation parameters in a second generation foil bearing: : effect of shaft temperature Type de document : texte imprimé Auteurs : Luis San Andrés, Auteur ; Ryu, Keun, Auteur ; Tae Ho Kim, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Damping Gas turbines Machine bearings Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Established high temperature operation of gas foil bearings (GFB) is of great interest for gas turbine applications. The effects of (high) shaft temperature on the structural stiffness and mechanical energy dissipation parameters of a foil bearing (FB) must be assessed experimentally. Presently, a hollow shaft warmed by an electric heater holds a floating second generation FB that is loaded dynamically by an electromagnetic shaker. In tests with the shaft temperature up to 184°C, the measurements of dynamic load and ensuing FB deflection render the bearing structural parameters, stiffness and damping, as a function of excitation frequency and amplitude of motion. The identified FB stiffness and viscous damping coefficients increase with shaft temperature due to an increase in the FB assembly interference or preload. The bearing material structural loss factor best representing mechanical energy dissipation decreases slightly with shaft temperature while increasing with excitation frequency. Separate static load measurements on the bearing also make evident the preload of the test bearing-shaft system at room temperature. The loss factor obtained from the area inside the hysteresis loop of the static load versus the deflection curve agrees remarkably with the loss factor obtained from the dynamic load measurements. The static procedure offers substantial savings in cost and time to determine the energy dissipation characteristics of foil bearings. Post-test inspection of the FB reveals sustained wear at the locations, where the bumps contact the top foil and the bearing sleeve inner surface, thus, evidences the bearing energy dissipation by dry friction. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Identification of structural stiffness and energy dissipation parameters in a second generation foil bearing: : effect of shaft temperature [texte imprimé] / Luis San Andrés, Auteur ; Ryu, Keun, Auteur ; Tae Ho Kim, Auteur . - 2012 . - 09 p.
Génie Mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 3 (Mars 2011) . - 09 p.
Mots-clés : Damping Gas turbines Machine bearings Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Established high temperature operation of gas foil bearings (GFB) is of great interest for gas turbine applications. The effects of (high) shaft temperature on the structural stiffness and mechanical energy dissipation parameters of a foil bearing (FB) must be assessed experimentally. Presently, a hollow shaft warmed by an electric heater holds a floating second generation FB that is loaded dynamically by an electromagnetic shaker. In tests with the shaft temperature up to 184°C, the measurements of dynamic load and ensuing FB deflection render the bearing structural parameters, stiffness and damping, as a function of excitation frequency and amplitude of motion. The identified FB stiffness and viscous damping coefficients increase with shaft temperature due to an increase in the FB assembly interference or preload. The bearing material structural loss factor best representing mechanical energy dissipation decreases slightly with shaft temperature while increasing with excitation frequency. Separate static load measurements on the bearing also make evident the preload of the test bearing-shaft system at room temperature. The loss factor obtained from the area inside the hysteresis loop of the static load versus the deflection curve agrees remarkably with the loss factor obtained from the dynamic load measurements. The static procedure offers substantial savings in cost and time to determine the energy dissipation characteristics of foil bearings. Post-test inspection of the FB reveals sustained wear at the locations, where the bumps contact the top foil and the bearing sleeve inner surface, thus, evidences the bearing energy dissipation by dry friction. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 11 (Novembre 2010) . - 07 p.
Titre : Measurements of drag torque, lift-off journal speed, and temperature in a metal mesh foil bearing Type de document : texte imprimé Auteurs : Luis San Andrés, Auteur ; Thomas Abraham Chirathadam, Auteur ; Ryu, Keun, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Automotive engineering Helicopters Lubricating oils Machine bearings Rotary engines Torque measurement Turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Metal mesh foil bearings (MMFBs) are a promising low cost gas bearing technology for high performance oil-free microturbomachinery. Elimination of complex oil lubrication and sealing system by deploying MMFBs in rotorcraft gas turbine engines offers distinctive advantages such as reduced system weight, enhanced reliability at high rotational speeds and extreme temperatures, and extended maintenance intervals compared with mineral oil lubricated bearings. MMFBs for oil-free rotorcraft engines must demonstrate adequate load capacity, reliable rotordynamic performance, and low frictional losses in a high temperature environment. The paper presents the measurements of MMFB break-away torque, rotor lift-off and touchdown speeds, and temperature at increasing static load conditions. The tests, which were conducted in a test rig driven by an automotive turbocharger turbine, demonstrate the airborne operation (hydrodynamic gas film) of the floating test MMFB with little frictional loses at increasing loads. The measured drag torque peaks when the rotor starts and stops, and drops significantly once the bearing lifts off. The estimated rotor speed for lift-off increases linearly with the applied static load. During continuous operation, the MMFB temperature measured at the back surface of the top foil increases both with rotor speed and static load. Nonetheless, the temperature rise is mild, demonstrating reliable performance. Application of a sacrificial layer of solid lubricant on the top foil surface reduces the rotor break-away torque. The measurements give confidence on this simple bearing technology for ready application into oil-free turbomachinery. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Measurements of drag torque, lift-off journal speed, and temperature in a metal mesh foil bearing [texte imprimé] / Luis San Andrés, Auteur ; Thomas Abraham Chirathadam, Auteur ; Ryu, Keun, Auteur . - 2011 . - 07 p.
Génie Mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 11 (Novembre 2010) . - 07 p.
Mots-clés : Automotive engineering Helicopters Lubricating oils Machine bearings Rotary engines Torque measurement Turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Metal mesh foil bearings (MMFBs) are a promising low cost gas bearing technology for high performance oil-free microturbomachinery. Elimination of complex oil lubrication and sealing system by deploying MMFBs in rotorcraft gas turbine engines offers distinctive advantages such as reduced system weight, enhanced reliability at high rotational speeds and extreme temperatures, and extended maintenance intervals compared with mineral oil lubricated bearings. MMFBs for oil-free rotorcraft engines must demonstrate adequate load capacity, reliable rotordynamic performance, and low frictional losses in a high temperature environment. The paper presents the measurements of MMFB break-away torque, rotor lift-off and touchdown speeds, and temperature at increasing static load conditions. The tests, which were conducted in a test rig driven by an automotive turbocharger turbine, demonstrate the airborne operation (hydrodynamic gas film) of the floating test MMFB with little frictional loses at increasing loads. The measured drag torque peaks when the rotor starts and stops, and drops significantly once the bearing lifts off. The estimated rotor speed for lift-off increases linearly with the applied static load. During continuous operation, the MMFB temperature measured at the back surface of the top foil increases both with rotor speed and static load. Nonetheless, the temperature rise is mild, demonstrating reliable performance. Application of a sacrificial layer of solid lubricant on the top foil surface reduces the rotor break-away torque. The measurements give confidence on this simple bearing technology for ready application into oil-free turbomachinery. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p.
Titre : Prediction of axial and circumferential flow conditions in a high temperature foil bearing with axial cooling flow Type de document : texte imprimé Auteurs : Ryu, Keun, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Gas foil bearings (GFBs) Thermal management GFB-rotor system Axial cooling streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A successful implementation of gas foil bearings (GFBs) into high temperature turbomachinery requires adequate thermal management to maintain system reliability and stability. The most common approach for thermal management in a GFB-rotor system is to supply pressurized air at one end of the bearing to remove hot spots in the bearings and control thermal growth of components. This technical brief presents test data for a laboratory rotor-GFB system operating hot to identify the flow characteristics of axial cooling streams flowing through the thin film region and underneath the top foil. A bulk flow model is used for description of the fluid motion and includes the Hirs' friction factor formulation for smooth surfaces. Laminar flow prevails through the thin film gas region; while for the cooling flow between the top foil and bearing housing, a transition from laminar flow to turbulent flow occurs as the cooling flow rate increases. Large cooling flow rate and the ensuing turbulent flow conditions render limited effectiveness in controlling temperatures in a test rotor-GFB system. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Prediction of axial and circumferential flow conditions in a high temperature foil bearing with axial cooling flow [texte imprimé] / Ryu, Keun, Auteur . - 2012 . - 06 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p.
Mots-clés : Gas foil bearings (GFBs) Thermal management GFB-rotor system Axial cooling streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A successful implementation of gas foil bearings (GFBs) into high temperature turbomachinery requires adequate thermal management to maintain system reliability and stability. The most common approach for thermal management in a GFB-rotor system is to supply pressurized air at one end of the bearing to remove hot spots in the bearings and control thermal growth of components. This technical brief presents test data for a laboratory rotor-GFB system operating hot to identify the flow characteristics of axial cooling streams flowing through the thin film region and underneath the top foil. A bulk flow model is used for description of the fluid motion and includes the Hirs' friction factor formulation for smooth surfaces. Laminar flow prevails through the thin film gas region; while for the cooling flow between the top foil and bearing housing, a transition from laminar flow to turbulent flow occurs as the cooling flow rate increases. Large cooling flow rate and the ensuing turbulent flow conditions render limited effectiveness in controlling temperatures in a test rotor-GFB system. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 6 (Juin 2011) . - 10 p.
Titre : Thermal management and rotordynamic performance of a hot rotor-gas foil bearings system—Part I: measurements Type de document : texte imprimé Auteurs : Luis San Andrés, Auteur ; Ryu, Keun, Auteur ; Tae Ho Kim, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Turbines à gaz Langues : Anglais (eng) Mots-clés : Cooling Gas turbines Machine bearings Rotors Shafts Temperature measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Implementation of gas foil bearings (GFBs) into micro gas turbines requires careful thermal management with accurate measurements verifying model predictions. This two-part paper presents test data and analytical results for a test rotor and GFB system operating hot (157°C maximum rotor outer diameter (OD) temperature). Part I details the test rig and measurements of bearing temperatures and rotor dynamic motions obtained in a hollow rotor supported on a pair of second generation GFBs, each consisting of a single top foil (38.14 mm inner diameter) uncoated for high temperature operation and five bump strip support layers. An electric cartridge (maximum of 360°C) loosely installed inside the rotor (1.065 kg, 38.07 mm OD, and 4.8 mm thick) is a heat source warming the rotor-bearing system. While coasting down from 30 krpm to rest, large elapsed times (50–70 s) demonstrate rotor airborne operation, near friction free, and while traversing the system critical speed at ~13 krpm, the rotor peak motion amplitude decreases as the system temperature increases. In tests conducted at a fixed rotor speed of 30 krpm, while the shaft heats, a cooling gas stream of increasing strength is set to manage the temperatures in the bearings and rotor. The effect of the cooling flow, if turbulent in character, is most distinctive at the highest heater temperature. For operation at a lower heater temperature condition, however, the cooling flow stream demonstrates a very limited effectiveness. The measurements demonstrate the reliable performance of the rotor-GFB system when operating hot. The test results, along with full disclosure on the materials and geometry of the test bearings and rotor, serve to benchmark a predictive tool. A companion paper (Part II) compares the measured bearing temperatures and the rotor response amplitudes to predictions. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...] [article] Thermal management and rotordynamic performance of a hot rotor-gas foil bearings system—Part I: measurements [texte imprimé] / Luis San Andrés, Auteur ; Ryu, Keun, Auteur ; Tae Ho Kim, Auteur . - 2011 . - 10 p.
Turbines à gaz
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 6 (Juin 2011) . - 10 p.
Mots-clés : Cooling Gas turbines Machine bearings Rotors Shafts Temperature measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Implementation of gas foil bearings (GFBs) into micro gas turbines requires careful thermal management with accurate measurements verifying model predictions. This two-part paper presents test data and analytical results for a test rotor and GFB system operating hot (157°C maximum rotor outer diameter (OD) temperature). Part I details the test rig and measurements of bearing temperatures and rotor dynamic motions obtained in a hollow rotor supported on a pair of second generation GFBs, each consisting of a single top foil (38.14 mm inner diameter) uncoated for high temperature operation and five bump strip support layers. An electric cartridge (maximum of 360°C) loosely installed inside the rotor (1.065 kg, 38.07 mm OD, and 4.8 mm thick) is a heat source warming the rotor-bearing system. While coasting down from 30 krpm to rest, large elapsed times (50–70 s) demonstrate rotor airborne operation, near friction free, and while traversing the system critical speed at ~13 krpm, the rotor peak motion amplitude decreases as the system temperature increases. In tests conducted at a fixed rotor speed of 30 krpm, while the shaft heats, a cooling gas stream of increasing strength is set to manage the temperatures in the bearings and rotor. The effect of the cooling flow, if turbulent in character, is most distinctive at the highest heater temperature. For operation at a lower heater temperature condition, however, the cooling flow stream demonstrates a very limited effectiveness. The measurements demonstrate the reliable performance of the rotor-GFB system when operating hot. The test results, along with full disclosure on the materials and geometry of the test bearings and rotor, serve to benchmark a predictive tool. A companion paper (Part II) compares the measured bearing temperatures and the rotor response amplitudes to predictions. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...]
Permalink
