Stability and response predictions are presented for a Flexibly Mounted Rotor (FMR) mechanical seal ring using the model developed by Childs in 2018. The seal ring is excited by lateral/pitch vibration from the rotor/housing. The model includes a frequency dependent stiffness and damping model for the O-ring and a frequency independent model for the fluid film. The dynamic coefficients are speed and frequency dependent. The mechanical seal is modeled after a typical FMR mechanical seal. Parameters for radius, fluid film clearance, and O-Ring axial distances are varied. The axial distance between the O-Ring and seal ring inertia center doz is found to couple lateral rotor motion and seal ring pitch vibration. The predictions show a dependency on both excitation frequency and running speed. The analyzed FMR has a critical region with high transmissibility in a region around a speed and excitation frequency of 70 kRPM. Another region of high transmissibility is predicted to be with sub-harmonic excitation frequency. The FMR seal ring also has an unstable region that is sub-harmonic of 1% running speed. Running back on the HQ curve for a pump causes broadband sub-harmonic excitaiton, which can cause rub failures for FMR mechanical seals.
{"title":"Predictions for Non-Contacting Mechanical Face Seal Vibration With External Excitation From Pump Vibration: Part II — Flexibly Mounted Rotor","authors":"Clay S. Norrbin, D. Childs","doi":"10.1115/GT2018-77200","DOIUrl":"https://doi.org/10.1115/GT2018-77200","url":null,"abstract":"Stability and response predictions are presented for a Flexibly Mounted Rotor (FMR) mechanical seal ring using the model developed by Childs in 2018. The seal ring is excited by lateral/pitch vibration from the rotor/housing. The model includes a frequency dependent stiffness and damping model for the O-ring and a frequency independent model for the fluid film. The dynamic coefficients are speed and frequency dependent. The mechanical seal is modeled after a typical FMR mechanical seal. Parameters for radius, fluid film clearance, and O-Ring axial distances are varied. The axial distance between the O-Ring and seal ring inertia center doz is found to couple lateral rotor motion and seal ring pitch vibration. The predictions show a dependency on both excitation frequency and running speed. The analyzed FMR has a critical region with high transmissibility in a region around a speed and excitation frequency of 70 kRPM. Another region of high transmissibility is predicted to be with sub-harmonic excitation frequency. The FMR seal ring also has an unstable region that is sub-harmonic of 1% running speed. Running back on the HQ curve for a pump causes broadband sub-harmonic excitaiton, which can cause rub failures for FMR mechanical seals.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"21 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132805609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Oil lubricated floating ring bearings (FRBs) are popular among the passenger vehicle turbochargers. Air entrainment occurs in the inner film of the FRB under low oil-supplied pressure. Air entrainment has great impact on the bearing performance. Experiments reported that FRB with a circumferential groove on the ring shows lower ring-to-shaft speed and improved stabilizing capacity at high shaft speed. This study aims to construct the numerical simulation method to predict the multiphase flow in the grooved ring (GR) FRB. Computational fluid dynamic (CFD) method is adopted to obtain the bearing performance considering air entrainment. CFD calculation can obtain detailed air entrainment results that experiment cannot provide. Calculation results are compared with the experimental results to validate the proposed CFD method. Analysis shows the great influence of grooved ring on the air entrainment. Air entrainment contributes to the decrease of the ring-to-shaft speed ratio in the GR FRB. The proposed CFD calculation considering air entrainment can give good prediction of the ring rotation speed under different shaft speed. Besides, detailed analysis of the effective viscosity indicates that outer film is mainly affected by thermal effect. Inner film is affected by both thermal effect and air entrainment effect, where latter is more predominant.
{"title":"Investigation of Air-Oil Distribution of Low Oil-Supplied Pressure Grooved Ring Floating Ring Bearing","authors":"Wang Yan, Li Yuhong","doi":"10.1115/GT2018-75887","DOIUrl":"https://doi.org/10.1115/GT2018-75887","url":null,"abstract":"Oil lubricated floating ring bearings (FRBs) are popular among the passenger vehicle turbochargers. Air entrainment occurs in the inner film of the FRB under low oil-supplied pressure. Air entrainment has great impact on the bearing performance. Experiments reported that FRB with a circumferential groove on the ring shows lower ring-to-shaft speed and improved stabilizing capacity at high shaft speed. This study aims to construct the numerical simulation method to predict the multiphase flow in the grooved ring (GR) FRB. Computational fluid dynamic (CFD) method is adopted to obtain the bearing performance considering air entrainment. CFD calculation can obtain detailed air entrainment results that experiment cannot provide. Calculation results are compared with the experimental results to validate the proposed CFD method. Analysis shows the great influence of grooved ring on the air entrainment. Air entrainment contributes to the decrease of the ring-to-shaft speed ratio in the GR FRB. The proposed CFD calculation considering air entrainment can give good prediction of the ring rotation speed under different shaft speed. Besides, detailed analysis of the effective viscosity indicates that outer film is mainly affected by thermal effect. Inner film is affected by both thermal effect and air entrainment effect, where latter is more predominant.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"151 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132579083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Different forms of Reynolds equation are widely used to predict the performances of foil thrust bearings for air cycle machines. When analyzing bearings operating with highly dense CO2, computational fluid dynamics yields more accurate results, particularly at the high rotational speed. In addition, the structural deformation of the top and bump foils are also considered. For some applications, the high temperature increase caused by the viscous heating effect are also modelled in literature. The multi-physics effects within foil bearings, including the fluid flow, structural deformation and viscous heating create challenges and modelling complexity to accurately predict its performances. The aim of this paper is to review and compare different modelling approaches for foil thrust bearings with CO2 at a range of operating conditions, including loads and rotational speed. For steady state performances, results from turbulent Reynolds equation and computational fluid dynamics are in close agreement for foil thrust bearings operating with low load (large rotor to top foil separations). However, considerable differences exist between turbulent Reynolds equation and computational fluid dynamics method at high loads (small rotor to top foil separation). Here the computational fluid dynamics method must be employed, as the centrifugal inertia effect becomes significant. The top foil deflection need to be considered as the corresponding deformation is significant compared to the initial separation between the rotor and the top foil. At the rotational speed larger than 30000 rpm, the results from the fully fluid-structure-thermal simulations differ from other modelling approaches. The additional deformation caused by temperature increase largely alters the separation between the rotor and top foil. For dynamic performance, the top foil deflection again must be considered as the equivalent stiffness and damping are influenced by bump foil structures. This work provides recommendations for the selection of the suitable modelling approaches for bump-type foil thrust bearings operating with supercritical CO2.
{"title":"Comparison of Modelling Approaches for Bump-Type Foil Thrust Bearings Operating With CO2","authors":"Kan Qin, Daijin Li, Kai Luo, Z. Tian, I. Jahn","doi":"10.1115/GT2018-75705","DOIUrl":"https://doi.org/10.1115/GT2018-75705","url":null,"abstract":"Different forms of Reynolds equation are widely used to predict the performances of foil thrust bearings for air cycle machines. When analyzing bearings operating with highly dense CO2, computational fluid dynamics yields more accurate results, particularly at the high rotational speed. In addition, the structural deformation of the top and bump foils are also considered. For some applications, the high temperature increase caused by the viscous heating effect are also modelled in literature. The multi-physics effects within foil bearings, including the fluid flow, structural deformation and viscous heating create challenges and modelling complexity to accurately predict its performances. The aim of this paper is to review and compare different modelling approaches for foil thrust bearings with CO2 at a range of operating conditions, including loads and rotational speed. For steady state performances, results from turbulent Reynolds equation and computational fluid dynamics are in close agreement for foil thrust bearings operating with low load (large rotor to top foil separations). However, considerable differences exist between turbulent Reynolds equation and computational fluid dynamics method at high loads (small rotor to top foil separation). Here the computational fluid dynamics method must be employed, as the centrifugal inertia effect becomes significant. The top foil deflection need to be considered as the corresponding deformation is significant compared to the initial separation between the rotor and the top foil. At the rotational speed larger than 30000 rpm, the results from the fully fluid-structure-thermal simulations differ from other modelling approaches. The additional deformation caused by temperature increase largely alters the separation between the rotor and top foil. For dynamic performance, the top foil deflection again must be considered as the equivalent stiffness and damping are influenced by bump foil structures. This work provides recommendations for the selection of the suitable modelling approaches for bump-type foil thrust bearings operating with supercritical CO2.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114436014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stability and response predictions are presented for a Flexibly Mounted Stator (FMS) mechanical seal ring using the model developed by Childs in 2018. The seal ring is excited by external vibration from the rotor/housing. The model includes a frequency dependent stiffness and damping model for the O-ring and a frequency independent model for the fluid film. The dynamic coefficients depend on both speed and excitation frequency. Data used in defining the model are representative of a typical FMS mechanical seal. Parameters for radius and O-Ring placement are varied. The predictions show an insignificant dependency on speed. The predictions are strongly frequency dependent with a critical speed of 90 kRPM. The FMS is predicted to be stable to frequencies below 140 kRPM. The distance between the O-Ring and seal ring inertia center doz couples lateral and pitch-yaw motion of the seal ring. Overall, if doz is kept small, the seal ring is predicted to not have any stability or response issues.
{"title":"Predictions for Non-Contacting Mechanical Face Seal Vibration With External Excitation From Pump Vibration: Part I — Flexibly Mounted Stator","authors":"Clay S. Norrbin, D. Childs","doi":"10.1115/gt2018-77198","DOIUrl":"https://doi.org/10.1115/gt2018-77198","url":null,"abstract":"Stability and response predictions are presented for a Flexibly Mounted Stator (FMS) mechanical seal ring using the model developed by Childs in 2018. The seal ring is excited by external vibration from the rotor/housing. The model includes a frequency dependent stiffness and damping model for the O-ring and a frequency independent model for the fluid film. The dynamic coefficients depend on both speed and excitation frequency. Data used in defining the model are representative of a typical FMS mechanical seal. Parameters for radius and O-Ring placement are varied. The predictions show an insignificant dependency on speed. The predictions are strongly frequency dependent with a critical speed of 90 kRPM. The FMS is predicted to be stable to frequencies below 140 kRPM. The distance between the O-Ring and seal ring inertia center doz couples lateral and pitch-yaw motion of the seal ring. Overall, if doz is kept small, the seal ring is predicted to not have any stability or response issues.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132919773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates the effect of gas foil thrust bearing (GFTB) on the rotordynamic performance of the rotor-gas foil bearing (GFB) system. A rigid rotor supported on two gas foil journal bearings (GFJB) and a pair of GFTBs is studied using a five degree of freedom (5-DOF) model. The studies were performed in both frequency domain using excitation frequency-dependent bearing coefficients (modal analyses) and non-linear analyses (time domain orbit simulations). Modal analyses were performed for both symmetrically and asymmetrically supported rotor systems. For the symmetric rotor, the modal stiffness for the conical mode increases with the axial force, while cylindrical mode is not affected. The axial force has little effects on the modal damping for both the cylindrical mode and conical mode. Thus, the natural frequency and threshold speed (stability limit) for the conical mode increases as the axial force increases, while these values for the cylindrical mode remain almost constant. For the asymmetric rotor, the modal stiffness for both the cylindrical mode and conical mode increases with the axial force, and thus both natural frequency and threshold speed increase with the axial force. Rotor lateral vibrations were also predicted using synchronous bearing coefficients (of both GFJB and GFTB) for both conical and cylindrical modes. The predicted rotor lateral responses show the critical speed increases with axial force for both cylindrical mode and conical mode. The nonlinear analysis using time-domain orbit simulation was also performed including the effect of axial force on the GFTB. The effect of axial force on the stability of the rotor system were discussed. The predicted results showed that the stability of rotor system improved as the axial force increases for Case 1 when the out of phase imbalances were added on the rotor. However, the stability of the rotor system for Case 2 not only influenced by the axial force but also influenced by how asymmetry the rotor is. For the in phase imbalances, the onset speed of subsynchronous motion decreases as axial force increases for the large asymmetric rotor bearing system and the decrement of the onset speed of subsynchronous decreases as the asymmetry of the rotor bearing system decreases. For the out of phase imbalances, the onset speed of subsynchronous motion also decreases as axial force increases for the large asymmetric rotor, but an opposite trend was shown as the asymmetry of the rotor decreases.
{"title":"Effect of Axial Force on Rotordynamics of a Rigid Rotor Supported by Foil Bearings","authors":"Wanhui Liu, Daejong Kim, K. Feng","doi":"10.1115/GT2018-76261","DOIUrl":"https://doi.org/10.1115/GT2018-76261","url":null,"abstract":"This paper investigates the effect of gas foil thrust bearing (GFTB) on the rotordynamic performance of the rotor-gas foil bearing (GFB) system. A rigid rotor supported on two gas foil journal bearings (GFJB) and a pair of GFTBs is studied using a five degree of freedom (5-DOF) model. The studies were performed in both frequency domain using excitation frequency-dependent bearing coefficients (modal analyses) and non-linear analyses (time domain orbit simulations). Modal analyses were performed for both symmetrically and asymmetrically supported rotor systems. For the symmetric rotor, the modal stiffness for the conical mode increases with the axial force, while cylindrical mode is not affected. The axial force has little effects on the modal damping for both the cylindrical mode and conical mode. Thus, the natural frequency and threshold speed (stability limit) for the conical mode increases as the axial force increases, while these values for the cylindrical mode remain almost constant. For the asymmetric rotor, the modal stiffness for both the cylindrical mode and conical mode increases with the axial force, and thus both natural frequency and threshold speed increase with the axial force. Rotor lateral vibrations were also predicted using synchronous bearing coefficients (of both GFJB and GFTB) for both conical and cylindrical modes. The predicted rotor lateral responses show the critical speed increases with axial force for both cylindrical mode and conical mode. The nonlinear analysis using time-domain orbit simulation was also performed including the effect of axial force on the GFTB. The effect of axial force on the stability of the rotor system were discussed. The predicted results showed that the stability of rotor system improved as the axial force increases for Case 1 when the out of phase imbalances were added on the rotor. However, the stability of the rotor system for Case 2 not only influenced by the axial force but also influenced by how asymmetry the rotor is. For the in phase imbalances, the onset speed of subsynchronous motion decreases as axial force increases for the large asymmetric rotor bearing system and the decrement of the onset speed of subsynchronous decreases as the asymmetry of the rotor bearing system decreases. For the out of phase imbalances, the onset speed of subsynchronous motion also decreases as axial force increases for the large asymmetric rotor, but an opposite trend was shown as the asymmetry of the rotor decreases.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131684548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hirotoshi Arihara, Yukiyoshi Kameyama, Y. Baba, L. Andrés
Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e. 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads’ temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields, and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads’ maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.
{"title":"A Thermoelastohydrodynamic Analysis for the Static Performance of High-Speed Heavy Load Tilting-Pad Journal Bearing Operating in the Turbulent Flow Regime and Comparisons to Test Data","authors":"Hirotoshi Arihara, Yukiyoshi Kameyama, Y. Baba, L. Andrés","doi":"10.1115/GT2018-77151","DOIUrl":"https://doi.org/10.1115/GT2018-77151","url":null,"abstract":"Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e. 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads’ temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields, and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads’ maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130677531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yi-xin Su, Yanhui Ma, Yongpeng Gu, Suyuan Yu, Gexue Ren
In contrast with traditional mechanical bearing, Active magnetic bearing (AMB) has no friction and lubrication, and its dynamic performance can be adjusted by active control. To isolate low frequency vibration of the rotating machinery under 50Hz, a novel design of cascade PID controller (CPC) with two control loops for AMB is proposed. The main loop is a position loop and the secondary loop is a transmission force loop. According to the theoretical derivations in this study, the CPC controls both the rotor position and the transmission force. Even when the control parameters maintain constant, the dynamic characteristic parameters, equivalent stiffness and equivalent damping, vary with frequency continuously and smoothly. Therefore, they can be adjusted in a wide range to achieve isolation of low frequency vibration when using proper control parameters. A simulation example shows that the transmission force with a CPC is lower in the 8–50Hz when the rotor displacement is almost same as with a single stage PID controller (SSPC). Experimental verification was carried out in an experimental bench of AMB under unbalanced rotor condition. Results show that a CPC can reduce the vibration acceleration at 15–50Hz especially near the peaks. Simulation and experimental results well demonstrate the effectiveness and guaranteed stability of the CPC in the present study.
{"title":"Improvement of Low Frequency Vibration Isolation Capability of AMB Using a Cascade PID Controller","authors":"Yi-xin Su, Yanhui Ma, Yongpeng Gu, Suyuan Yu, Gexue Ren","doi":"10.1115/GT2018-76023","DOIUrl":"https://doi.org/10.1115/GT2018-76023","url":null,"abstract":"In contrast with traditional mechanical bearing, Active magnetic bearing (AMB) has no friction and lubrication, and its dynamic performance can be adjusted by active control. To isolate low frequency vibration of the rotating machinery under 50Hz, a novel design of cascade PID controller (CPC) with two control loops for AMB is proposed. The main loop is a position loop and the secondary loop is a transmission force loop. According to the theoretical derivations in this study, the CPC controls both the rotor position and the transmission force. Even when the control parameters maintain constant, the dynamic characteristic parameters, equivalent stiffness and equivalent damping, vary with frequency continuously and smoothly. Therefore, they can be adjusted in a wide range to achieve isolation of low frequency vibration when using proper control parameters. A simulation example shows that the transmission force with a CPC is lower in the 8–50Hz when the rotor displacement is almost same as with a single stage PID controller (SSPC). Experimental verification was carried out in an experimental bench of AMB under unbalanced rotor condition. Results show that a CPC can reduce the vibration acceleration at 15–50Hz especially near the peaks. Simulation and experimental results well demonstrate the effectiveness and guaranteed stability of the CPC in the present study.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125000476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Test results are presented for a smooth-rotor/circumferentially-grooved, annular pump seal. The seal’s geometry and operating conditions are representative of electrical submersible pumps (ESPs) as used for oil recovery; however, most ESPs use grooved rotors instead of grooved stators. Test results include static and rotordynamic data at speeds ω of 2, 4, 6 krpm, axial pressure drops ΔP of 2.1, 4.1, 6.2, 8.3 bars. The grooved seal has a length-to-diameter ratio L/D of 0.5 and a minimum radial clearance Cr of 203 μm. It employs 15 circumferential grooves with a length Gl, and depth Gd of 1.52 mm, which are equally-spaced by a land length of 1.52 mm. Tests are conducted for eccentricity ratios ϵ0 of 0.00, 0.27, 0.53, 0.80. Three different inlet-fluid prerotation inserts are used upstream of the test seals to create a range of inlet preswirl ratios. Pitot tubes are used to measure the circumferential velocity at one location immediately upstream of the test seal and one downstream location near the seal exit. The test fluid is ISOVG2 oil @ 46 °C. Test results for the grooved seal are compared to test results for a smooth annular seal with the same L, D, and minimum Cr. The grooved-seal’s leakage rate Q̇, ranges from a low 15.64 LPM at ω = 6 krpm, and ΔP = 2 bar, to a high 56.36 LPM at ω = 2 krpm, and ΔP = 8 bar. When compared to the smooth seal, the grooved seal provides a 20% Q̇ reduction at ω = 2 krpm, and a 6% reduction at ω = 6 krpm. The grooved seal’s rotordynamic coefficients are generally not sensitive to changes in ϵ0. The smooth seal’s stiffness and damping coefficients are not very sensitive to changes in ϵ0 in moving from ϵ0 = 0 to 0.5, but typically increase dramatically in magnitude in moving from ϵ0 = 0.5 to 0.8. From a rotordynamic viewpoint, the major difference between the two seals concerns the direct stiffness coefficients, with the grooved seal having near zero to negative values and the smooth seal having larger positive values, particularly at increased ϵ0 values. The grooved seal generally produces lower-magnitude cross-coupled stiffness and direct damping coefficient values than the smooth seal.
{"title":"Static and Rotordynamic Characteristics of Liquid Annular Seals With a Circumferentially-Grooved Stator and Smooth Rotor Using Three Levels of Circumferential Inlet-Fluid Rotation","authors":"D. Childs, Jose Torres, Joshua T. Bullock","doi":"10.1115/GT2018-75325","DOIUrl":"https://doi.org/10.1115/GT2018-75325","url":null,"abstract":"Test results are presented for a smooth-rotor/circumferentially-grooved, annular pump seal. The seal’s geometry and operating conditions are representative of electrical submersible pumps (ESPs) as used for oil recovery; however, most ESPs use grooved rotors instead of grooved stators. Test results include static and rotordynamic data at speeds ω of 2, 4, 6 krpm, axial pressure drops ΔP of 2.1, 4.1, 6.2, 8.3 bars. The grooved seal has a length-to-diameter ratio L/D of 0.5 and a minimum radial clearance Cr of 203 μm. It employs 15 circumferential grooves with a length Gl, and depth Gd of 1.52 mm, which are equally-spaced by a land length of 1.52 mm. Tests are conducted for eccentricity ratios ϵ0 of 0.00, 0.27, 0.53, 0.80. Three different inlet-fluid prerotation inserts are used upstream of the test seals to create a range of inlet preswirl ratios. Pitot tubes are used to measure the circumferential velocity at one location immediately upstream of the test seal and one downstream location near the seal exit. The test fluid is ISOVG2 oil @ 46 °C. Test results for the grooved seal are compared to test results for a smooth annular seal with the same L, D, and minimum Cr. The grooved-seal’s leakage rate Q̇, ranges from a low 15.64 LPM at ω = 6 krpm, and ΔP = 2 bar, to a high 56.36 LPM at ω = 2 krpm, and ΔP = 8 bar. When compared to the smooth seal, the grooved seal provides a 20% Q̇ reduction at ω = 2 krpm, and a 6% reduction at ω = 6 krpm. The grooved seal’s rotordynamic coefficients are generally not sensitive to changes in ϵ0. The smooth seal’s stiffness and damping coefficients are not very sensitive to changes in ϵ0 in moving from ϵ0 = 0 to 0.5, but typically increase dramatically in magnitude in moving from ϵ0 = 0.5 to 0.8. From a rotordynamic viewpoint, the major difference between the two seals concerns the direct stiffness coefficients, with the grooved seal having near zero to negative values and the smooth seal having larger positive values, particularly at increased ϵ0 values. The grooved seal generally produces lower-magnitude cross-coupled stiffness and direct damping coefficient values than the smooth seal.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115783770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rolling bearing is a key part of turbomachinery. The performance and reliability of the bearing is vital to the safe operation of turbomachinery. Therefore, degradation feature extraction of rolling bearing is important to prevent it from failure. During rolling bearing degradation, machine vibration can increase, and this may be used to predict the degradation. The vibration signals are however complicated and nonlinear, making it difficult to extract degradation features effectively. Here, a novel degradation feature extraction method based on optimal ensemble empirical mode decomposition (EEMD) and improved composite spectrum (CS) analysis is proposed. Firstly, because only a few IMFs are expected to contain the information related to bearing fault, EEMD is utilized to pre-process the vibration signals. An optimization method is designed for adaptively determining the appropriate EEMD parameters for the signal, so that the significant feature components of the faulty bearing can be extracted from the signal and separated from background noise and other irrelevant components to bearing faults. Then, Bayesian information criterion (BIC) and correlation kurtosis (CK) are employed to select the sensitive intrinsic mode function (IMF) components and obtain fault information effectively. Finally, an improved CS analysis algorithm is used to fuse the selected sensitive IMF components, and the CS entropy (CSE) is extracted as degradation feature. Experimental data on the test bearings with single point faults separately at the inner race and rolling element were studied to demonstrate the capabilities of the proposed method. The results show that it can assess the bearing degradation status and has good sensitivity and good consistency to the process of bearing degradation.
{"title":"Degradation Feature Extraction of Rolling Bearings Based on Optimal Ensemble Empirical Mode Decomposition and Improved Composite Spectrum Analysis","authors":"Fengli Wang, Hua Chen","doi":"10.1115/GT2018-75041","DOIUrl":"https://doi.org/10.1115/GT2018-75041","url":null,"abstract":"Rolling bearing is a key part of turbomachinery. The performance and reliability of the bearing is vital to the safe operation of turbomachinery. Therefore, degradation feature extraction of rolling bearing is important to prevent it from failure. During rolling bearing degradation, machine vibration can increase, and this may be used to predict the degradation. The vibration signals are however complicated and nonlinear, making it difficult to extract degradation features effectively. Here, a novel degradation feature extraction method based on optimal ensemble empirical mode decomposition (EEMD) and improved composite spectrum (CS) analysis is proposed. Firstly, because only a few IMFs are expected to contain the information related to bearing fault, EEMD is utilized to pre-process the vibration signals. An optimization method is designed for adaptively determining the appropriate EEMD parameters for the signal, so that the significant feature components of the faulty bearing can be extracted from the signal and separated from background noise and other irrelevant components to bearing faults. Then, Bayesian information criterion (BIC) and correlation kurtosis (CK) are employed to select the sensitive intrinsic mode function (IMF) components and obtain fault information effectively. Finally, an improved CS analysis algorithm is used to fuse the selected sensitive IMF components, and the CS entropy (CSE) is extracted as degradation feature. Experimental data on the test bearings with single point faults separately at the inner race and rolling element were studied to demonstrate the capabilities of the proposed method. The results show that it can assess the bearing degradation status and has good sensitivity and good consistency to the process of bearing degradation.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"272 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126056540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aerodynamic foil bearings are suitable to support light, high-speed rotors under extreme operating conditions such as very low or very high temperatures, e.g. in cooling turbines, small gas turbines or exhaust gas turbochargers. The required bearing load capacity is generated by an aerodynamic pressure build-up in the corresponding lubrication gap. Due to the high dependence of the bearing performance on the bore geometry, the rotordynamic behavior (e.g. bearing stability) and static properties (e.g. load capacity) as a function of radial clearance and hydrodynamic preload are one of the main points of interest in recent studies. The outcome of both the experimental and the numerical investigations show the advantages and disadvantages of the various configurations of the bearing bore in different operating conditions. These observations lead to the basic idea of an adaptive air foil bearing (AAFB) in which, depending on the operating conditions, the bearing bore contour is changed by means of piezoelectric actuators applied to the compliant supporting shell. Similar to other shape morphing approaches, optimization with regard to various components of the mechanism is the next step in the design process after targeting the design pattern. This paper concentrates on an AAFB as an efficient approach to actively shape the contour of the bore clearance in a 3-pad bearing. Numerous FEM analyses of a functional model for an AAFB in addition to the experimental efforts reveal the main concerns of the design. Finally, the result of this study is a working graph for the AAFB under various loading conditions while operating with different input voltages of the actuators.
{"title":"Design Characteristics of an Aerodynamic Foil Bearing With Adaptable Bore Clearance","authors":"H. Sadri, H. Schlums, M. Sinapius","doi":"10.1115/GT2018-76204","DOIUrl":"https://doi.org/10.1115/GT2018-76204","url":null,"abstract":"Aerodynamic foil bearings are suitable to support light, high-speed rotors under extreme operating conditions such as very low or very high temperatures, e.g. in cooling turbines, small gas turbines or exhaust gas turbochargers. The required bearing load capacity is generated by an aerodynamic pressure build-up in the corresponding lubrication gap. Due to the high dependence of the bearing performance on the bore geometry, the rotordynamic behavior (e.g. bearing stability) and static properties (e.g. load capacity) as a function of radial clearance and hydrodynamic preload are one of the main points of interest in recent studies. The outcome of both the experimental and the numerical investigations show the advantages and disadvantages of the various configurations of the bearing bore in different operating conditions. These observations lead to the basic idea of an adaptive air foil bearing (AAFB) in which, depending on the operating conditions, the bearing bore contour is changed by means of piezoelectric actuators applied to the compliant supporting shell. Similar to other shape morphing approaches, optimization with regard to various components of the mechanism is the next step in the design process after targeting the design pattern. This paper concentrates on an AAFB as an efficient approach to actively shape the contour of the bore clearance in a 3-pad bearing. Numerous FEM analyses of a functional model for an AAFB in addition to the experimental efforts reveal the main concerns of the design. Finally, the result of this study is a working graph for the AAFB under various loading conditions while operating with different input voltages of the actuators.","PeriodicalId":131756,"journal":{"name":"Volume 7B: Structures and Dynamics","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133730406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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