The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Guang Meng - One of the best experts on this subject based on the ideXlab platform.
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Multi-faults decoupling on turbo-expander using differential-based ensemble empirical mode decomposition
Mechanical Systems and Signal Processing, 2017Co-Authors: Hong Guang Li, Fucai Li, Cheng Li, Ming Li, Guang MengAbstract:Abstract This paper dedicates on the multi-faults decoupling of turbo-expander rotor system using Differential-based Ensemble Empirical Mode Decomposition (DEEMD). DEEMD is an improved version of DEMD to resolve the imperfection of mode mixing. The nonlinear behaviors of the turbo-expander considering temperature gradient with crack, rub-impact and pedestal looseness faults are investigated respectively, so that the baseline for the multi-faults decoupling can be established. DEEMD is then utilized on the vibration signals of the rotor system with coupling faults acquired by numerical simulation, and the results indicate that DEEMD can successfully decouple the coupling faults, which is more efficient than EEMD. DEEMD is also applied on the vibration signal of the misalignment coupling with rub-impact fault obtained during the adjustment of the experimental system. The conclusion shows that DEEMD can decompose the practical multi-faults signal and the industrial prospect of DEEMD is verified as well.
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Rotor dynamics behavior of turbo-expander involving droplet impact
Mathematical and Computer Modelling of Dynamical Systems, 2016Co-Authors: Hong Guang Li, Shengtong Zhou, Fucai Li, Xiaohu Wang, Ming Li, Guang MengAbstract:ABSTRACTThis paper dedicates on the rotor dynamics behaviour research on the turbo-expander rotor system involving droplet impact. A stochastic model based on Beta distribution and Bernoulli distribution of droplet generation is established and the formulations of droplet impact forces are deduced, which is applied on the rotor dynamics equations of the tilting pad bearing supported turbo-expander considering the temperature gradient for a further analysis. A time domain research is carried out and a conclusion that continuously droplet impact will perturb the steady vibration of the turbo-expander rotor system is obtained. Monte Carlo method is implemented for a statistics dynamics research and the results suggests that in the design of expander impellers, in order to decrease the uncertainty brought by droplet impact, the number of channels should be as few as possible, the droplet impact should be controlled to occur uniformly, and the collision, entrainment of the primary droplets and the stripping of...
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Rotor dynamics behavior of turbo-expander involving droplet impact
Mathematical and Computer Modelling of Dynamical Systems, 2016Co-Authors: Hong Guang Li, Shengtong Zhou, Fucai Li, Huiyu Bai, Rui Zhu, Xiaohu Wang, Ming Li, Guang MengAbstract:? 2016 Informa UK Limited, trading as Taylor & Francis Group.This paper dedicates on the rotor dynamics behaviour research on the turbo-expander rotor system involving droplet impact. A stochastic model based on Beta distribution and Bernoulli distribution of droplet generation is established and the formulations of droplet impact forces are deduced, which is applied on the rotor dynamics equations of the tilting pad bearing supported turbo-expander considering the temperature gradient for a further analysis. A time domain research is carried out and a conclusion that continuously droplet impact will perturb the steady vibration of the turbo-expander rotor system is obtained. Monte Carlo method is implemented for a statistics dynamics research and the results suggests that in the design of expander impellers, in order to decrease the uncertainty brought by droplet impact, the number of channels should be as few as possible, the droplet impact should be controlled to occur uniformly, and the collision, entrainment of the primary droplets and the stripping of the liquid film on the blade should be strictly restrained.
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Rotor Dynamics Behavior of Tilting Pad Bearing Supported Turbo-Expander Considering Temperature Gradient
Journal of Computational and Nonlinear Dynamics, 2015Co-Authors: Ming Li, Fucai Li, Huiyu Bai, Rui Zhu, Xingxing Liu, Hong Guang Li, Xiaohu Wang, Guang MengAbstract:This paper dedicates on the rotor dynamics behavior analysis on a tilting pad bearing supported turbo-expander rotor system considering temperature gradient. Both numerical and experimental investigations are conducted intensively. The influence of the temperature gradient is modeled as the change of the lubrication oil viscosity and the length variation of the clearance due to the cryogenic thermal expansion of the journal. The analytical expressions of the tilting pad bearing oil-film force are then amended and substitute into the lumped parameter model of the turbo-expander rotor dynamics. Linear analysis based on this model indicates that the existence of the temperature gradient can stabilize the turbo-expander rotor system to an extent, while the nonlinear analyses reveal that the temperature gradient will advance the occurrence of the quasi-periodic motion and break the equilibrium of the vibration between the expander side and the compressor side. Furthermore, an experimental system is established and the experimental results show that the temperature of the tilting pad bearing is influenced by the environment temperature greatly; the spectrum of the displacement of the rotor is dominated by the synchronous frequency of the impellers and bearings. The experiment results also observe the vibration amplitude decreases when the environment temperature gets down and grows when the rotating speed increases. At the same time, the sensitivity of the vibration amplitude versus rotating speed decreases as the environment temperature rises, and vice versa.
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Nonlinear rotor dynamics on turbo expander with unbalanced bearing force caused by temperature difference
JOURNAL OF VIBROENGINEERING, 2015Co-Authors: Ming Li, Xianbo Liu, Fucai Li, Hong Guang Li, Cheng Li, Guang MengAbstract:This paper dedicates on the non-dimensional nonlinear rotor dynamics analysis of a turbo expander under unbalanced bearing forces caused by the temperature difference. The turbo expander rotor system is abstracted to a strictly symmetric lumped parameter model. The influence of temperature difference is simplified to the ratio of oil viscosity, which is applied on Capone oil film model. 1-Dimensional and 2-Dimensional bifurcation analysis are implemented in order to obtain the dynamic characteristics of the turbo expander rotor system. It can be concluded that the compressor wheel and the expander wheel are of the same pattern of motion in spite of the existence of the temperature difference; High temperature difference results in a high entrance point of 1-periodic motion to quasi-periodic motion, but the entrance point keeps still when the ratio of viscosity reaches some critical value. The oil-whirl, first and second order oil whip of sliding bearings are the most important factors influencing the asymmetric vibration of the compressor wheel and the expander wheel.
Shuangtao Chen - One of the best experts on this subject based on the ideXlab platform.
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Numerical study on the spontaneous condensation flow in an air cryogenic turbo-expander using equilibrium and non-equilibrium models
Cryogenics, 2020Co-Authors: Liang Chen, Shuangtao Chen, Xingqun ZhangAbstract:Abstract The difficulty of data measurement in cryogenic environments and the complicated mechanism of nucleation process have restricted the design of wet type turbo-expander for cryogenic liquid plants. In this paper, equilibrium and non-equilibrium models are used to model the spontaneous condensation flow in a cryogenic turbo-expander along the main stream passage including nozzle, impeller and diffuser. The comparison shows a distinct difference of the predicted wetness fraction distribution along the streamline between the equilibrium model and the non-equilibrium model. In non-equilibrium model, the distributions of supercooling and nucleation rate along the length of turbo-expander are given for the analysis of flow characteristics. The comparison of outlet wetness fraction with the experimental data is also provided for verification and discussion. Both the effects of the rotation on nucleation and the effects of the nucleation on flow along suction side of the impeller are investigated.
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Numerical studies on two-phase flow in cryogenic radial-inflow turbo-expander using varying condensation models
Applied Thermal Engineering, 2019Co-Authors: Shuangtao Chen, Shanshan Bu, Zaiyong Ma, Luteng ZhangAbstract:Abstract An accurate condensation model plays an important role in the development of high-efficiency turbine. Many efforts have been devoted into the research on steam non-equilibrium condensation. However, aiming at the cryogenic gas at high-speed flow the studies on the condensation model are still inadequate and incomprehensive. In present paper, different condensation models, established via the alternations of nucleation model and droplet growth model are compiled into commercial CFD software to simulate the non-equilibrium condensation flow within a cryogenic radial-inflow turbo-expander. Firstly, the rotation effect on droplets diameter and distribution within the impeller passage are analyzed. The results point out the region where large droplets are prone to form and gather. Furthermore, the influence mechanism of heat and mass transfer in varying condensation models on the flow fields, including rapid nucleation, supercooled degree, liquid mass fraction, droplet diameter, are revealed based on the analysis of Nusselt number and Knudsen number. The results imply that the predicted location of condensation onset is little sensitive to the droplet growth model. At last, the effect of modifications for nucleation rate and droplet growth rate on the thermodynamic losses in turbo-expander are quantificationally discussed.
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Non-equilibrium spontaneous condensation flow in cryogenic turbo-expander based on mean streamline off-design method
Cryogenics, 2019Co-Authors: Xingya Chen, Shuangtao ChenAbstract:Abstract In a modern cryogenic liquefaction system, the turbo-expander is used to operate in the two-phase region so that a high cooling capacity can be provided. Compared with the expansion process in a conventional over-heated turbo-expander, non-equilibrium condensation occurs in the duct when the turbo-expander operates in the two-phase region, which varies the expansion process. In our previous works, the simulation by CFX can predict the nucleation process controlled by gaseous sub-cooling well, and the outlet liquid fraction has a good agreement with our experimental data. As the non-equilibrium condensation simulated by using CFX consumes much time and massive computing resource, it is not feasible to simulate the two-phase expansion in the turbo-expander in a wide off-design range. In this study, we investigate the non-equilibrium spontaneous condensation along the mean streamline of a cryogenic turbo-expander passage by using an off-design computational code compiled by Matlab. The two-phase off-design computational code is developed from our previous overheated off-design code. The calculation function of thermodynamic parameters on the mean streamline and non-equilibrium condensation module are integrated with this code. The variations of thermodynamic parameters on the mean streamline in a non-equilibrium condensation process are simulated. Nucleation onset, droplet growth/vaporization process, liquid fraction distribution are revealed. Droplet developing region is divided according to the droplet critical and mean radius. Simulation results of five two-phase cases are compared and analyzed, and different non-equilibrium condensation features and liquid fraction distributions are found. At last, isentropic efficiency and outlet liquid fraction are used to evaluate two-phase expansion performance, and it is found that the performance results from the simulation in five cases agree with experimental data well.
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Numerical studies on the off-design performance of a cryogenic two-phase turbo-expander
Applied Thermal Engineering, 2018Co-Authors: Shuangtao Chen, Shanshan Bu, Zaiyong MaAbstract:Abstract The two-phase Turbo-Expanders are in more popular as their advantage of more provided cooling capacity in cryogenic applications. However, it makes the preliminary or alternative design and off-design prediction for this type turbine to remain an unworked area, due to a lack of better understanding for machine performance under two-phase conditions. This paper numerically studies the machine off-design performance based on a cryogenic turbo-expander, which is a key equipment to supply main cooling capacity for an air separation plant. The investigative off-design conditions including 420 numerical cases cover both superheated region and two-phase region. The simulations of gas expansion involving two-phase flow in nozzle and impeller are performed on non-equilibrium condensation model of ANSYS CFX. According to the state of gas expansion end point, the numerical results could be categorized as three types, i.e. superheated, supercooled and spontaneous condensation expansions. The effect of non-equilibrium thermodynamic process on the outlet parameters also is revealed via comparison with results from ideal equilibrium condensation model. Moreover, the turbo-expander performance maps under superheated and two-phase conditions, including mass flow rate, degree of reaction and total-to-static efficiency, are compared and analyzed. Finally, taking liquid mass fraction as a fundamental parameter as well as velocity ratio, new 3-D performance maps of reaction and efficiency are developed. The research achievements could be applicable to turbine design and performance prediction at two-phase conditions.
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Off-design performance analysis of cryogenic turbo-expander based on mathematic prediction and experiment research
Applied Thermal Engineering, 2018Co-Authors: Yang Meng, Shuangtao Chen, Xiaojiang Li, Qiang ZengAbstract:Abstract Cryogenic turbo-expander is most significant equipment to provide cooling energy in system and its working condition is always deviated from design point. A mathematic prediction method study is carried out to estimate turbo-expander off-design performance. Computational iterative loop is compiled by Matlab, dimensionless mass flow rate equation of mean streamline and novel loss correlation are applied to quantitatively describe the flow expansion through turbine ducts. Cryogenic turbo-expander performance is evaluated by total-to-static efficiency. According to velocity ratio, the effect of pressure ratio, inlet temperature, rotational speed variation to turbine performance is analyzed, and the predicted performance map is plotted. Meanwhile, an experimental study is conducted under off-design condition. Temperature, pressure, rotation speed and volume flow rate are collected, total-to-static efficiency are calculated from turbine inlet and outlet states over pressure ratio range of 2.4–3.4, and the tested rotation speed range is set from 52,000 to 60,000 rpm. Turbine efficiency in different pressure ratio range are categorized and plotted with velocity ratio to validate against computational predicted characteristic. With experimental comparison, this off-design performance mathematic code can predict turbine real operation well.
Ari Darmawan Pasek - One of the best experts on this subject based on the ideXlab platform.
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Geometry Analysis and Effect of Turbulence Model on the Radial Rotor Turbo-Expander Design for Small Organic Rankine Cycle System
Journal of Mechatronics Electrical Power and Vehicular Technology, 2015Co-Authors: Maulana Arifin, Ari Darmawan Pasek, Zaidan EddyAbstract:Organic Rankine Cycle (ORC) is one of the most promising technology for small electric power generations. The geometry analysis and the effect of turbulence model on the radial Turbo-Expanders design for small ORC power generation systems were discussed in this paper. The rotor blades and performance were calculated using several working fluids such as R134a, R143a, R245fa, n-Pentane, and R123. Subsequently, a numerical study was carried out in the fluid flow area with R134a and R123 as the working fluids. Analyses were performed using Computational Fluid Dynamics (CFD) ANSYS Multiphysics on two real gas models, with the k-epsilon and SST ( shear stress transport ) turbulence models. The result shows the distribution of Mach number, pressure, velocity and temperature along the rotor blade of the radial Turbo-Expanders and estimation of performance at various operating conditions. The operating conditions are as follow: 250,000 grid mesh flow area, real gas model SST at steady state condition, 0.4 kg/s of mass flow rate, 15,000 rpm rotor speed, 5 bar inlet pressure, and 373K inlet temperature. By using those conditions, CFD analysis shows that the turbo-expander able to produce 6.7 kW and 5.5 kW of power when using R134a and R123, respectively.
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Process manufacture rotor radial turbo-expander for small scale organic Rankine cycles using selective laser melting machine
Energy Procedia, 2015Co-Authors: Maulana Arifin, Endro Junianto, Bambang Wahono, Ari Darmawan PasekAbstract:This paper discusses the manufacturing process of rotor radial Turbo-Expanders for small Organic Rankine Cycle systems using additive manufacturing machine Selective Laser Melting (SLM) machine. The process manufacturing consists of data preparation, build job process, and process finishing product. Data preparations are include material preparations, build data preparation using software 3D design Solidworks, support management with software magics and additive manufacturing software with Autofab for build job process on SLM machine. The results shows rotor with material Aluminum Silicon Powder (AlSi) can be made with either the appropriate geometry design within 5 hours with total cost for the whole processing is up to 11 milion IDR.
Maulana Arifin - One of the best experts on this subject based on the ideXlab platform.
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Geometry Analysis and Effect of Turbulence Model on the Radial Rotor Turbo-Expander Design for Small Organic Rankine Cycle System
Journal of Mechatronics Electrical Power and Vehicular Technology, 2015Co-Authors: Maulana Arifin, Ari Darmawan Pasek, Zaidan EddyAbstract:Organic Rankine Cycle (ORC) is one of the most promising technology for small electric power generations. The geometry analysis and the effect of turbulence model on the radial Turbo-Expanders design for small ORC power generation systems were discussed in this paper. The rotor blades and performance were calculated using several working fluids such as R134a, R143a, R245fa, n-Pentane, and R123. Subsequently, a numerical study was carried out in the fluid flow area with R134a and R123 as the working fluids. Analyses were performed using Computational Fluid Dynamics (CFD) ANSYS Multiphysics on two real gas models, with the k-epsilon and SST ( shear stress transport ) turbulence models. The result shows the distribution of Mach number, pressure, velocity and temperature along the rotor blade of the radial Turbo-Expanders and estimation of performance at various operating conditions. The operating conditions are as follow: 250,000 grid mesh flow area, real gas model SST at steady state condition, 0.4 kg/s of mass flow rate, 15,000 rpm rotor speed, 5 bar inlet pressure, and 373K inlet temperature. By using those conditions, CFD analysis shows that the turbo-expander able to produce 6.7 kW and 5.5 kW of power when using R134a and R123, respectively.
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Process manufacture rotor radial turbo-expander for small scale organic Rankine cycles using selective laser melting machine
Energy Procedia, 2015Co-Authors: Maulana Arifin, Endro Junianto, Bambang Wahono, Ari Darmawan PasekAbstract:This paper discusses the manufacturing process of rotor radial Turbo-Expanders for small Organic Rankine Cycle systems using additive manufacturing machine Selective Laser Melting (SLM) machine. The process manufacturing consists of data preparation, build job process, and process finishing product. Data preparations are include material preparations, build data preparation using software 3D design Solidworks, support management with software magics and additive manufacturing software with Autofab for build job process on SLM machine. The results shows rotor with material Aluminum Silicon Powder (AlSi) can be made with either the appropriate geometry design within 5 hours with total cost for the whole processing is up to 11 milion IDR.
Hong Guang Li - One of the best experts on this subject based on the ideXlab platform.
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Multi-faults decoupling on turbo-expander using differential-based ensemble empirical mode decomposition
Mechanical Systems and Signal Processing, 2017Co-Authors: Hong Guang Li, Fucai Li, Cheng Li, Ming Li, Guang MengAbstract:Abstract This paper dedicates on the multi-faults decoupling of turbo-expander rotor system using Differential-based Ensemble Empirical Mode Decomposition (DEEMD). DEEMD is an improved version of DEMD to resolve the imperfection of mode mixing. The nonlinear behaviors of the turbo-expander considering temperature gradient with crack, rub-impact and pedestal looseness faults are investigated respectively, so that the baseline for the multi-faults decoupling can be established. DEEMD is then utilized on the vibration signals of the rotor system with coupling faults acquired by numerical simulation, and the results indicate that DEEMD can successfully decouple the coupling faults, which is more efficient than EEMD. DEEMD is also applied on the vibration signal of the misalignment coupling with rub-impact fault obtained during the adjustment of the experimental system. The conclusion shows that DEEMD can decompose the practical multi-faults signal and the industrial prospect of DEEMD is verified as well.
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Rotor dynamics behavior of turbo-expander involving droplet impact
Mathematical and Computer Modelling of Dynamical Systems, 2016Co-Authors: Hong Guang Li, Shengtong Zhou, Fucai Li, Xiaohu Wang, Ming Li, Guang MengAbstract:ABSTRACTThis paper dedicates on the rotor dynamics behaviour research on the turbo-expander rotor system involving droplet impact. A stochastic model based on Beta distribution and Bernoulli distribution of droplet generation is established and the formulations of droplet impact forces are deduced, which is applied on the rotor dynamics equations of the tilting pad bearing supported turbo-expander considering the temperature gradient for a further analysis. A time domain research is carried out and a conclusion that continuously droplet impact will perturb the steady vibration of the turbo-expander rotor system is obtained. Monte Carlo method is implemented for a statistics dynamics research and the results suggests that in the design of expander impellers, in order to decrease the uncertainty brought by droplet impact, the number of channels should be as few as possible, the droplet impact should be controlled to occur uniformly, and the collision, entrainment of the primary droplets and the stripping of...
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Rotor dynamics behavior of turbo-expander involving droplet impact
Mathematical and Computer Modelling of Dynamical Systems, 2016Co-Authors: Hong Guang Li, Shengtong Zhou, Fucai Li, Huiyu Bai, Rui Zhu, Xiaohu Wang, Ming Li, Guang MengAbstract:? 2016 Informa UK Limited, trading as Taylor & Francis Group.This paper dedicates on the rotor dynamics behaviour research on the turbo-expander rotor system involving droplet impact. A stochastic model based on Beta distribution and Bernoulli distribution of droplet generation is established and the formulations of droplet impact forces are deduced, which is applied on the rotor dynamics equations of the tilting pad bearing supported turbo-expander considering the temperature gradient for a further analysis. A time domain research is carried out and a conclusion that continuously droplet impact will perturb the steady vibration of the turbo-expander rotor system is obtained. Monte Carlo method is implemented for a statistics dynamics research and the results suggests that in the design of expander impellers, in order to decrease the uncertainty brought by droplet impact, the number of channels should be as few as possible, the droplet impact should be controlled to occur uniformly, and the collision, entrainment of the primary droplets and the stripping of the liquid film on the blade should be strictly restrained.
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Rotor Dynamics Behavior of Tilting Pad Bearing Supported Turbo-Expander Considering Temperature Gradient
Journal of Computational and Nonlinear Dynamics, 2015Co-Authors: Ming Li, Fucai Li, Huiyu Bai, Rui Zhu, Xingxing Liu, Hong Guang Li, Xiaohu Wang, Guang MengAbstract:This paper dedicates on the rotor dynamics behavior analysis on a tilting pad bearing supported turbo-expander rotor system considering temperature gradient. Both numerical and experimental investigations are conducted intensively. The influence of the temperature gradient is modeled as the change of the lubrication oil viscosity and the length variation of the clearance due to the cryogenic thermal expansion of the journal. The analytical expressions of the tilting pad bearing oil-film force are then amended and substitute into the lumped parameter model of the turbo-expander rotor dynamics. Linear analysis based on this model indicates that the existence of the temperature gradient can stabilize the turbo-expander rotor system to an extent, while the nonlinear analyses reveal that the temperature gradient will advance the occurrence of the quasi-periodic motion and break the equilibrium of the vibration between the expander side and the compressor side. Furthermore, an experimental system is established and the experimental results show that the temperature of the tilting pad bearing is influenced by the environment temperature greatly; the spectrum of the displacement of the rotor is dominated by the synchronous frequency of the impellers and bearings. The experiment results also observe the vibration amplitude decreases when the environment temperature gets down and grows when the rotating speed increases. At the same time, the sensitivity of the vibration amplitude versus rotating speed decreases as the environment temperature rises, and vice versa.
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Nonlinear rotor dynamics on turbo expander with unbalanced bearing force caused by temperature difference
JOURNAL OF VIBROENGINEERING, 2015Co-Authors: Ming Li, Xianbo Liu, Fucai Li, Hong Guang Li, Cheng Li, Guang MengAbstract:This paper dedicates on the non-dimensional nonlinear rotor dynamics analysis of a turbo expander under unbalanced bearing forces caused by the temperature difference. The turbo expander rotor system is abstracted to a strictly symmetric lumped parameter model. The influence of temperature difference is simplified to the ratio of oil viscosity, which is applied on Capone oil film model. 1-Dimensional and 2-Dimensional bifurcation analysis are implemented in order to obtain the dynamic characteristics of the turbo expander rotor system. It can be concluded that the compressor wheel and the expander wheel are of the same pattern of motion in spite of the existence of the temperature difference; High temperature difference results in a high entrance point of 1-periodic motion to quasi-periodic motion, but the entrance point keeps still when the ratio of viscosity reaches some critical value. The oil-whirl, first and second order oil whip of sliding bearings are the most important factors influencing the asymmetric vibration of the compressor wheel and the expander wheel.
