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Development and performance measurement of oil-free turbocharger supported on gas foil bearings / Yong-Bok Lee in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 11 p. Titre : Development and performance measurement of oil-free turbocharger supported on gas foil bearings Type de document : texte imprimé Auteurs : Yong-Bok Lee, Auteur ; Dong-Jin Park, Auteur ; Tae Ho Kim, Auteur ; Kyuho Sim, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Géne mécanique Langues : Anglais (eng) Mots-clés : Compressors  Diesel  engines  Heat  transfer  Machine  bearings  Polynomials  Turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper present the development of an oil-free turbocharger (TC) supported on gas foil bearings (GFBs) and its performance evaluation in a test rig driven by a diesel vehicle engine (EG). The rotor-bearing system was designed via a rotordynamic analysis with dynamic force coefficients derived from the analysis of the GFBs. The developed oil-free TC was designed using a hollow rotor with a radial turbine at one end and a compressor wheel at the other end, a center housing with journal and thrust GFBs, and turbine and compressor casings. Preliminary tests driven by pressurized shop air at room temperature demonstrated relatively stable operation up to a TC speed of 90,000 rpm, accompanied by a dominant synchronous motion of ~20 µm and small subsynchronous motions of less than 2 µm at the higher end of the speed range. Under realistic operating conditions with a diesel vehicle engine at a maximum TC speed of 136,000 rpm and a maximum EG speed of 3140 rpm, EG and TC speeds and gas flow properties were measured. The measured time responses of the TC speed and the turbine inlet pressure demonstrated time delays of ~3.9 and ~1.3 s from that of the EG speed during consecutive stepwise EG speed changes, implying the GFB friction and rotor inertia led to time delays of ~2.6 s. The measured pressures and temperatures showed trends following second-order polynomials against EG speed. Regarding TC efficiency, 4.3 kW of mechanical power was supplied by the turbine and 3.3 kW was consumed by the compressor at the top speed of 136,000 rpm, and the power loss reached 22% of the turbine power. Furthermore, the estimated GFB power losses from the GFB analysis were approximately 25% of the total power loss at higher speeds, indicating the remainder of the power loss resulted from heat transfer from the exhaust gas to the surrounding solid structures. Incidentally, as the TC speed was increased from 45,000 to 136,000 rpm, the estimated turbine inlet power increased from 19 to 79 kW, the compressor exit power increased from 7 to 26 kW, and the TC output mass flow rate from the compressor increased from 21 to 74 g/s. The average TC compressor exit power was estimated at ~34% of the turbine inlet power over this range. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...] [article] Development and performance measurement of oil-free turbocharger supported on gas foil bearings [texte imprimé] / Yong-Bok Lee, Auteur ; Dong-Jin Park, Auteur ; Tae Ho Kim, Auteur ; Kyuho Sim, Auteur . - 2012 . - 11 p. Géne mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 11 p. Mots-clés : Compressors  Diesel  engines  Heat  transfer  Machine  bearings  Polynomials  Turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper present the development of an oil-free turbocharger (TC) supported on gas foil bearings (GFBs) and its performance evaluation in a test rig driven by a diesel vehicle engine (EG). The rotor-bearing system was designed via a rotordynamic analysis with dynamic force coefficients derived from the analysis of the GFBs. The developed oil-free TC was designed using a hollow rotor with a radial turbine at one end and a compressor wheel at the other end, a center housing with journal and thrust GFBs, and turbine and compressor casings. Preliminary tests driven by pressurized shop air at room temperature demonstrated relatively stable operation up to a TC speed of 90,000 rpm, accompanied by a dominant synchronous motion of ~20 µm and small subsynchronous motions of less than 2 µm at the higher end of the speed range. Under realistic operating conditions with a diesel vehicle engine at a maximum TC speed of 136,000 rpm and a maximum EG speed of 3140 rpm, EG and TC speeds and gas flow properties were measured. The measured time responses of the TC speed and the turbine inlet pressure demonstrated time delays of ~3.9 and ~1.3 s from that of the EG speed during consecutive stepwise EG speed changes, implying the GFB friction and rotor inertia led to time delays of ~2.6 s. The measured pressures and temperatures showed trends following second-order polynomials against EG speed. Regarding TC efficiency, 4.3 kW of mechanical power was supplied by the turbine and 3.3 kW was consumed by the compressor at the top speed of 136,000 rpm, and the power loss reached 22% of the turbine power. Furthermore, the estimated GFB power losses from the GFB analysis were approximately 25% of the total power loss at higher speeds, indicating the remainder of the power loss resulted from heat transfer from the exhaust gas to the surrounding solid structures. Incidentally, as the TC speed was increased from 45,000 to 136,000 rpm, the estimated turbine inlet power increased from 19 to 79 kW, the compressor exit power increased from 7 to 26 kW, and the TC output mass flow rate from the compressor increased from 21 to 74 g/s. The average TC compressor exit power was estimated at ~34% of the turbine inlet power over this range. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...]

Rotordynamic performance of shimmed gas foil bearings for oil-free turbochargers / Kyuho Sim in Transactions of the ASME . Journal of tribology, Vol. 134 N° 3 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 11 p. Titre : Rotordynamic performance of shimmed gas foil bearings for oil-free turbochargers Type de document : texte imprimé Auteurs : Kyuho Sim, Auteur ; Yong-Bok Lee, Auteur ; Tae Ho Kim, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : tribology Langues : Anglais (eng) Mots-clés : oil-free  turbochargers;  internal  combustion  engines;  lubricant;  gas  foil  bearings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Oil-free turbochargers (TCs) will increase the power and efficiency of internal combustion engines, both sparking ignition and compression ignition, without engine oil lubricant feeding or scheduled maintenance. Using gas foil bearings (GFBs) in passenger vehicle TCs enables compact, lightweight, oil-free systems, along with accurate shaft motion. This paper presents extensive test measurements on GFBs for oil-free TCs, including static load-deflection measurements of test GFBs, rotordynamic performance measurements of a compressed air driven oil-free TC unit supported on test GFBs, and bench test measurements of the oil-free TC driven by a passenger vehicle diesel engine. Two configurations of GFBs, one original and the other modified with three shims, are subjected to a series of experimental tests. For the shimmed GFB, three metal shims are inserted under the bump-strip layers, in contact with the bearing housing. The installation of shims creates mechanical preloads that enhance a hydrodynamic wedge in the assembly radial clearance to generate more film pressure. Simple static load-deflection tests estimate the assembly radial clearance of the shimmed GFB, which is smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy in the top foil and bump strip layers. Test GFBs are installed into a TC test rig driven by compressed air for rotordynamic performance measurements. The test TC rotor, 335 g in weight and 117 mm long, is coated with a commercially available, wear-resistant solid lubricant, Amorphous M, to prevent severe wear during start-up and shutdown in the absence of an air film. A pair of optical proximity probes positioned orthogonally at the compressor end record lateral rotor motions. Rotordynamic test results show that the shimmed GFB significantly diminishes the large amplitude of subsynchronous rotor motions arising in the unmodified GFB. Predicted synchronous rotor amplitudes and rigid body mode natural frequencies agree reasonably well with recorded test data. Finally, the oil-free TC is installed into a passenger vehicle diesel engine test bench. The TC rotor speed is controlled by the vehicle engine. Speed-up tests show dominant synchronous motion (1X) of the rotor. Whirl frequencies of the relatively small subsynchronous motions are associated with the rigid body natural mode of the TC rotor-GFB system as well as (forced) excitation from the four-cylinder diesel engine. The bench test measurements demonstrate a significant reduction in the amplitude of subsynchronous motions for the shimmed GFB, thus verifying the preliminary test results in the TC test rig driven by compressed air. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013400 [...] [article] Rotordynamic performance of shimmed gas foil bearings for oil-free turbochargers [texte imprimé] / Kyuho Sim, Auteur ; Yong-Bok Lee, Auteur ; Tae Ho Kim, Auteur . - 2012 . - 11 p. tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 11 p. Mots-clés : oil-free  turbochargers;  internal  combustion  engines;  lubricant;  gas  foil  bearings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Oil-free turbochargers (TCs) will increase the power and efficiency of internal combustion engines, both sparking ignition and compression ignition, without engine oil lubricant feeding or scheduled maintenance. Using gas foil bearings (GFBs) in passenger vehicle TCs enables compact, lightweight, oil-free systems, along with accurate shaft motion. This paper presents extensive test measurements on GFBs for oil-free TCs, including static load-deflection measurements of test GFBs, rotordynamic performance measurements of a compressed air driven oil-free TC unit supported on test GFBs, and bench test measurements of the oil-free TC driven by a passenger vehicle diesel engine. Two configurations of GFBs, one original and the other modified with three shims, are subjected to a series of experimental tests. For the shimmed GFB, three metal shims are inserted under the bump-strip layers, in contact with the bearing housing. The installation of shims creates mechanical preloads that enhance a hydrodynamic wedge in the assembly radial clearance to generate more film pressure. Simple static load-deflection tests estimate the assembly radial clearance of the shimmed GFB, which is smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy in the top foil and bump strip layers. Test GFBs are installed into a TC test rig driven by compressed air for rotordynamic performance measurements. The test TC rotor, 335 g in weight and 117 mm long, is coated with a commercially available, wear-resistant solid lubricant, Amorphous M, to prevent severe wear during start-up and shutdown in the absence of an air film. A pair of optical proximity probes positioned orthogonally at the compressor end record lateral rotor motions. Rotordynamic test results show that the shimmed GFB significantly diminishes the large amplitude of subsynchronous rotor motions arising in the unmodified GFB. Predicted synchronous rotor amplitudes and rigid body mode natural frequencies agree reasonably well with recorded test data. Finally, the oil-free TC is installed into a passenger vehicle diesel engine test bench. The TC rotor speed is controlled by the vehicle engine. Speed-up tests show dominant synchronous motion (1X) of the rotor. Whirl frequencies of the relatively small subsynchronous motions are associated with the rigid body natural mode of the TC rotor-GFB system as well as (forced) excitation from the four-cylinder diesel engine. The bench test measurements demonstrate a significant reduction in the amplitude of subsynchronous motions for the shimmed GFB, thus verifying the preliminary test results in the TC test rig driven by compressed air. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013400 [...]

Thermal performance measurement of a bump type gas foil bearing floating on a hollow shaft for increasing rotating speed and static load / Tae Ho Kim in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 2 (Février 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 2 (Février 2012) . - 05 p. Titre : Thermal performance measurement of a bump type gas foil bearing floating on a hollow shaft for increasing rotating speed and static load Type de document : texte imprimé Auteurs : Tae Ho Kim, Auteur ; Jin Woo Song, Auteur ; Yong-Bok Lee, Auteur ; Kyuho Sim, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Machine  bearings  Motor  drives  Strain  gauges  Temperature  measurement  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Identifying thermal characteristics of gas foil bearings (GFBs) provides an insight for successful implementation into high speed oil-free turbomachinery. The paper presents temperature measurements of a bump type GFB floating on a hollow shaft for various operating conditions. Two angular ball bearings support the hollow shaft at one end (right), and the other end (left) is free. Test GFB has the outer diameter of 100 mm and the axial length of 45 mm, and the hollow shaft has the outer and inner diameters of 60 mm and 40 mm, respectively. An electric motor drives the hollow shaft using a spline coupling connection. A mechanical loading device provides static loads on test GFB upward via a metal wire, and a strain gauge type load cell placed in the middle of the wire indicates the applied loads. During experiments for shaft speeds of 5 krpm, 10 krpm, and 15 krpm and with static loads of 58.9 N (6 kgf), 78.5 N (8 kgf), and 98.1 N (10 kgf), twelve thermocouples measure the outer surface temperatures of test GFB at four angular locations of 45 deg, 135 deg, 215 deg, and 315 deg, with an origin at the top foil free end, and three axial locations of bearing centerline and both side edges at each angle. Two infrared thermometers measure the outer surface temperature of the hollow shaft at free and supported ends close to test GFB. Test results show that GFB temperatures increase as the shaft speed increases and as the static load increases, with higher temperatures in the loaded zone (135 deg and 215 deg) than those in the unloaded zone (45 deg and 315 deg). In general, the recorded temperatures are highest at 225 deg where a highest hydrodynamic pressure is expected to build up. Measured temperatures at the bearing centerline are higher than those at the side edges, as expected. In addition, large thermal gradients are recorded in the hollow shaft along the axial direction with higher temperatures at the supported end. The axial thermal gradient of the shaft is thought to cause higher temperatures at the bearing right edge facing the ball bearing support than those at the left edge. The paper presents test data along with detailed test GFB/shaft geometries and material properties. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000002 [...] [article] Thermal performance measurement of a bump type gas foil bearing floating on a hollow shaft for increasing rotating speed and static load [texte imprimé] / Tae Ho Kim, Auteur ; Jin Woo Song, Auteur ; Yong-Bok Lee, Auteur ; Kyuho Sim, Auteur . - 2012 . - 05 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 2 (Février 2012) . - 05 p. Mots-clés : Machine  bearings  Motor  drives  Strain  gauges  Temperature  measurement  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Identifying thermal characteristics of gas foil bearings (GFBs) provides an insight for successful implementation into high speed oil-free turbomachinery. The paper presents temperature measurements of a bump type GFB floating on a hollow shaft for various operating conditions. Two angular ball bearings support the hollow shaft at one end (right), and the other end (left) is free. Test GFB has the outer diameter of 100 mm and the axial length of 45 mm, and the hollow shaft has the outer and inner diameters of 60 mm and 40 mm, respectively. An electric motor drives the hollow shaft using a spline coupling connection. A mechanical loading device provides static loads on test GFB upward via a metal wire, and a strain gauge type load cell placed in the middle of the wire indicates the applied loads. During experiments for shaft speeds of 5 krpm, 10 krpm, and 15 krpm and with static loads of 58.9 N (6 kgf), 78.5 N (8 kgf), and 98.1 N (10 kgf), twelve thermocouples measure the outer surface temperatures of test GFB at four angular locations of 45 deg, 135 deg, 215 deg, and 315 deg, with an origin at the top foil free end, and three axial locations of bearing centerline and both side edges at each angle. Two infrared thermometers measure the outer surface temperature of the hollow shaft at free and supported ends close to test GFB. Test results show that GFB temperatures increase as the shaft speed increases and as the static load increases, with higher temperatures in the loaded zone (135 deg and 215 deg) than those in the unloaded zone (45 deg and 315 deg). In general, the recorded temperatures are highest at 225 deg where a highest hydrodynamic pressure is expected to build up. Measured temperatures at the bearing centerline are higher than those at the side edges, as expected. In addition, large thermal gradients are recorded in the hollow shaft along the axial direction with higher temperatures at the supported end. The axial thermal gradient of the shaft is thought to cause higher temperatures at the bearing right edge facing the ball bearing support than those at the left edge. The paper presents test data along with detailed test GFB/shaft geometries and material properties. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000002 [...]