Motion Of Rotor Research Articles

Dynamic modeling and analysis of high-speed aerostatic journal bearing-rotor system with recess

To analyze the dynamic properties of high-speed aerostatic journal bearing with recess, a bidirectional fluid-structure coupling dynamic model is established. The mathematical model is established by coupling the governing equation of the transient air film flow, the flow balance equation, and the rotor motion equation. Based on the trajectory of rotor axis, trajectory of rotor center, Poincare map, time response of rotor, frequency spectrum, mass flow rate, and bifurcation diagram, the influences of operating parameters on the coupling system are analyzed theoretically and experimentally. The results indicate that the system has abundant nonlinear behavior, and the instability parameters of the system are determined. This study provides guidance for the theoretical design and practical operation of this type of system.

Quantification of active bearing input force for vibration reduction performance of unbalanced rotor systems

Recently, rotating machinery has been widely applied in various mechanical systems such as hydroelectric and nuclear power plants. When mechanical systems are operated, the main rotor is rotated to manufacture the product. If a fault occurs in the rotor, then the system is damaged. Thus, to avoid malfunction of the system and rotor damage, vibration issues because of bending, misalignment, and imbalance should be considered. In this regard, a smart structure-based active bearing system is extensively researched and developed to control rotor vibration. This system can continuously improve the noise, vibration, and harshness performance under various operating conditions by controlling the dynamic characteristics of the active bearing. This study focused on the effect of rotor motion control by quantifying the active bearing force and phase when an active bearing was applied in a simple rotor model. A simple rotor with two active bearing systems was modeled based on lumped-parameter modeling. In the rotor model, the active bearing, which had two piezoelectric actuators and rubber grommets placed in both the x- and y-directions, was located on both sides to control the vibration. The interaction between the rotor and the active bearing system was considered to quantify the force and phase of this system. Furthermore, through simulation, the motion control effect was validated when an active bearing was applied in the rotor model.

P24: Mechanical Circulatory Support Device Technologies Incorporating Mechanical Pressure Regulation

Study: Mechanical circulatory support (MCS) devices perform in variable hemodynamic environments and must enable changes in speed, flow, and pressure based on performance requirements dictated by specific clinical states. In order to perform as intended, sensing of hemodynamic environment, and having a mechanism of pressure regulation, are necessary when experiencing differential pressures during operation inside a circulatory system. Herein, we report MCS devices with this pressure regulation feature. Methods and Results: By creating a passive rotor assembly through magnetic scheme and physical geometry of the housing’s interior, minimal pressure differentials upstream and downstream are able to influence the rotor’s position. In Figures 1 A and B, our universal ventricular assist device (UVAD) is depicted in open and closed positions, respectively. The rotor (shown in tan) spins about the (black) motor coils, but is also able to move axially (up and down in these figures), depending on the pressures acting on it. In Figure 1 C, flow shut off occurs when the rotor shoulder (located at the base of impeller blades) is near the corresponding internal shoulder of the (blue) housing, reducing the aperture between these features. Thus, limiting blood flow through the UVAD. Similarly, this passive rotor movement is designed into our family of continuous-flow total artificial hearts (CFTAH). Pressure differences generated by the left and right sides of the heart influence and affect the rotor’s axial position, regulating pressure and flow. Our pediatric CFTAH (P-CFTAH) is shown in Figure 1 D. Conclusion: Due to the environment, in which these devices operate, we can take advantage of the inherent differential pressures experienced, and simplify operation and control of our MCS devices. We have successfully implemented passive rotors in several developmental iterations of the UVAD, and three versions of our CFTAH (adult, pediatric, infant).

Explanation of the mechanisms of unsteady gas flow through the turbocharger seal system, including thermal and structural interactions

Gas flow in the seal system can be expected during the operation of a turbocharger and is associated with negative effects on the quality of the lubricant or turbocharger efficiency. Gas flow also affects particulate matter production due to lubricant entrainment in the compressor or turbine. The prediction of gas flow rates depends on many design parameters and the operating conditions of the turbocharger, but sufficiently accurate descriptions of the gas flow mechanisms and their quantification depending on the operating conditions have not yet been presented. The proposed computational approach simultaneously solves the gas dynamics in the seal system, the heat transfer in the turbocharger rotor-bearing system and the dynamics of the seal rings and rotor, including the bearings. The computational model for the turbocharger of a heavy-duty vehicle engine is experimentally validated. Two mechanisms have major influences on gas mass flow: the gas flow through the thin gap between the moving ring and groove and the flow through the ring gap. The results show that the importance of these mechanisms depends on several geometrical dimensions of the seal system and the operating conditions of the turbocharger, with a strong connection to the rotor dynamics and thermal load of the impellers. Influences involving rotor movement or rotor thermal conditions are crucial, and their non-inclusion limits the ability to correctly predict gas mass flow.

Laser-induced microtextured stators coupling with flexible rotors for low-voltage driving rotational piezoelectric motors

Traveling-wave ultrasonic motors promise widespread applications in precision engineering, medical, and aerospace field due to their high-power density, but suffer from low efficiency and stress gradient. In this case, the synergy effect of surface-functionalized friction regulation and interface coupling interference of wear loss/debris could effectively eliminate these deficiencies. Herein, we report a low-voltage driving rotational piezoelectric motor (PM30) that proceeds through laser-induced microtextured stators coupling with flexible rotors, which enables working at a rotational speed of 158 rpm and torque of 73 N·mm, respectively, under the condition of low-voltage (80Vp) and low-preload (40 N). Such operation parameters are far beyond the current reported results. Furthermore, FEM simulation and SEM observation demonstrated that the low-voltage driving and high-performance output are resulting from the combination of surface microtextured stators for friction enhancement and flexible rotors for displacement amplification with contact expansion, which regulates tangential friction and reshares the stresses distribution during the dynamic contact along with the rotary motion of rotors. This work provides a promising strategy to construct friction-stress regulation and energy-transformation enhancement toward energy-saving and high-efficient friction drive for piezoelectric devices.

Comparison of free vortex wake and blade element momentum results against large-eddy simulation results for highly flexible turbines under challenging inflow conditions

Abstract. Throughout wind energy development, there has been a push to increase wind turbine size due to the substantial economic benefits. However, increasing turbine size presents several challenges, both physically and computationally. Modeling large, highly flexible wind turbines requires highly accurate models to capture the complicated aeroelastic response due to large deflections and nonstraight blade geometries. Additionally, the development of floating offshore wind turbines requires modeling techniques that can predict large rotor and tower motion. Free vortex wake methods model such complex physics while remaining computationally tractable to perform key simulations necessary during the turbine design process. Recently, a free vortex wake model – cOnvecting LAgrangian Filaments (OLAF) – was added to the National Renewable Energy Laboratory's engineering tool OpenFAST to allow for the aerodynamic modeling of highly flexible turbines along with the aero-hydro-servo-elastic response capabilities of OpenFAST. In this work, free vortex wake and low-fidelity blade element momentum (BEM) results are compared to high-fidelity actuator-line computational fluid dynamics simulation results via the Simulator fOr Wind Farm Applications (SOWFA) method for a highly flexible downwind turbine for varying yaw misalignment, shear exponent, and turbulence intensity conditions. Through these comparisons, it was found that for all considered quantities of interest, SOWFA, OLAF, and BEM results compare well for steady inflow conditions with no yaw misalignment. For OLAF results, this strong agreement with the SOWFA results was consistent for all yaw misalignment values. The BEM results, however, deviated significantly more from the SOWFA results with increasing absolute yaw misalignment. Differences between OLAF and BEM results were dominated by the yaw misalignment angle, with varying shear exponent and turbulence intensity leading to more subtle differences. Overall, OLAF results were more consistent than BEM results when compared to SOWFA results under challenging inflow conditions.

Subcritical behaviour of short cylindrical journal bearings under periodic excitation

Rotating machinery supported on journal bearings is affected by forces due to rotating unbalance and pressure gradients in the oil film. The interaction of these forces can evoke nonlinear behaviour, including asynchronous motion and even chaos. This work attempts to characterise the sub-synchronous motion of the rigid rotor supported on cylindrical journal bearings due to the abovementioned interaction. The analysis focuses on the rotor behaviour at the rotor speeds lower than the threshold speed for oil whirl, associated with sub-synchronous vibration of magnitude equaling the bearing clearance. It is shown that the sub-synchronous vibration can occur well before reaching the threshold speed and that the underlying period-doubling bifurcation depends on the amount of the rotating unbalance. The rotor response and stability are analysed using a numerical continuation method employing the infinitely short journal bearing model. Continuation results are further validated by time simulations which utilise the finite difference method to compute the hydrodynamic forces. The validation process employs bifurcation diagrams, Poincaré sections and numerical estimates of the largest Lyapunov exponents.

Rolling and whip phenomenon of hollow rotor slipping on internal stator

Dynamic features of a rotor that rolls without or with whipping and slipping of own inner surface on a rigid stator are discussed. Change in the whirling direction associated with the rolling of the rotor from backward to forward was confirmed experimentally, i.e. in the case of an internal type for the stator-limiter in the direction of rotor rotation. Identification of dynamic behavior is made on the basis of eigenfrequencies and eigenmodes, motion orbits of an eccentric point (on the rotor), Campbell diagrams and AFC. The calculation of such characteristics has done using an original mathematical approach developed by the author earlier in order to describe the backward motion of common rotor on an external stator. A good agreement is obtained between the theoretical frequencies and amplitudes of vibration and the experimental ones. Therefore, the author’s technique is also suitable for the revealed forward rotor motion around the internal stator.

The stability analysis and nonlinear vibration control of shaft system for hydraulic generating set under multi-source excitation considering effects of dynamic and static eccentricities

Aiming at nonlinear vibration problems of shaft system for hydraulic generating set caused by multi-source excitation, based on the construction of unbalanced magnetic pull considering dynamic and static eccentricities, a coupled bending–torsional vibration model of shaft system and corresponding differential equations under the action of multi-vibration sources are established. Nonlinear dynamic analysis is conducted by the shooting method, and the Floquet theory is applied to investigate the stability of system periodic solution. On this basis, discrepancies of dynamic characteristics for systems whether mixed eccentricities are excluded are compared, disclosing that dynamic features of system change dramatically when composited eccentricities are taken into account, and effects from mass eccentricity, excitation current, as well as static and dynamic eccentricities on oscillation response of system are revealed thoroughly by means of numerical method. The magnetorheological fluid damper is incorporated into the system for the purpose of suppressing the nonlinear vibration during operation, and corresponding suppression laws on vibration of rotor and runner are disclosed. While reducing the amplitude of system, fixed eccentricities also increasing the probability of chaotic motion, in addition, the new dynamic phenomena including period 3, period 5 and period 6 are revealed. The rotor displacement will be altered by the fluctuation of excitation current, which affects the dynamic response of runner through stiffness item indirectly. The high dissipation capacity of magnetorheological fluid damper can effectively ameliorate the unsteady dynamic response of system, reduce the amplitude and inhibit the irregular movement of rotor and runner to a certain extent, so as to further increase the stability of unit. The relevant research results can provide references for fault diagnosis and vibration control of hydraulic generating set, as well as for the optimal design.

Dynamical modeling and experimental validation for squeeze film damper in bevel gears

Squeeze film damper (SFD) effectively reduces rotor motion amplitude while crossing critical speeds for vibration and noise reduction in a wide application of aero-engine rotor system. The squirrel cage elastic support (SCES) as an essential component of SFD, accurate modelling of SCES using component modal synthesis (CMS) to account for its flexibility, and calculation of nonlinear oil film forces for SFD using the finite difference method. The CMS method is also used to model the bevel gear wheel body and to establish a finite element nodal dynamics model of the gear-rotor-bearing-SFD system considering time-varying mesh stiffness, tooth clearance, gyroscopic effects, transmission error excitation and SFD oil film forces. The modal frequency of the gear shaft in aero-engine power transmission is exercised to verify the established bevel gear model. Moreover, a bevel gear test platform with SFD is established to study the vibration reduction effect of SFD. It is found that SFD can effectively improve the transmission of the bevel gear system, and the flexibility of the SCES makes the critical speed shift. Actually, the smaller the stiffness of SCES, the more the critical speed is moved to the left. By using CMS to determine the flexibility of bevel gear and SCES, it can show the complete phenomenon of the dynamic behaviors of the bevel gear system with SFD.

Impact of Whirl and Axial Motion on Ball Bearing Turbocharger Dynamics

Ball bearing turbochargers (TCs) incorporate an angular contact ball bearing cartridge to reduce friction and oil consumption, improving the efficiency of internal combustion engines. In this investigation, axial and radial TC rotor motion was experimentally measured and used to develop a model of the TC rotor-bearing system, allowing for a detailed analysis of the TC bearing under varying operating conditions. In order to achieve the experimental objectives of this investigation, eddy-current proximity probes were used to measure the radial motion at the turbine and compressor sides of the TC. The measured radial motion shows whirl with subharmonics at low speed. The measured axial motion of the rotor was found to increase with TC speed. In order to analytically investigate the bearing dynamics, a complete TC model was developed that includes the mass distribution and flexibility of the TC compressor, shaft and turbine, and squeeze-film dampers (SFDs) that support the bearing cartridge. The model was used to replicate the whirl and axial motion of the test rig and then to determine which model parameters could be adjusted to minimize whirl without negatively affecting the bearing dynamics. Simulation results revealed that centrifugal effects cause a change in the bearing internal geometry, with a small clearance becoming a preload at higher speeds. When this effect is coupled with less compliant SFDs, the subharmonics are reduced and the overall sliding and number of large load cycles at the ball–race contacts are minimized, contributing to lower bearing friction and improved overall life.

Physics-based recalibration method of cup anemometers

Cup anemometer is the most widely used instrument in the natural environment. However, the accuracy of cup anemometer is not robust due to their inertial structures. In this study, the equation of motion (EOM) relating rotational motion of the cup rotor to aerodynamic force is investigated to reveal the cause of measurement error of cup anemometer. A new methodology is proposed to recalibrate cup anemometer based on theoretical analysis of the dynamic response of the cup rotor and random process theory. The unknown dynamic coefficients of the EOM are quantified by the numerical method using measurement results from inertial and non-inertial anemometers. A detailed example is presented to demonstrate the efficiency of this new method in which coefficients of the EOM are quantified from laboratory and field data. Both mean wind speed and the entire time history could be recalibrated using this new method. Comparing with the non-inertial anemometer results, the improvement rate of the recalibrated cup anemometer results is 29%–99%.

Mathematical modeling of the rotor dynamics of a turbomachine on gas foil bearings subjected to vibration

BACKGROUND: The use of gas foil bearings is a promising development in the field of turbomachinery due to their economy, autonomous operation capability, and durability. However, gas foil bearings have lower load capacities than other types of bearings. However, turbomachines are complicated, dynamic systems that must meet high standards of safety, sustainability, and durability against external mechanical factors like vibration, shock, etc.
 AIM: Development of a mathematical model of rotor dynamics to predict the displacement of the rotor in foil bearings for maintaining separation between the rotor and the housing while being subjected to vibration.
 METHODS: A mathematical model of the dynamics of a stiff rotor on gas foil bearings was built and analyzed, taking into account the flexibility of the bearing bushing supports and the housing of the turbomachine. Stationary and transient modes of operation, including the transient modes combined with random vibration, are simulated. The system of ordinary derivatives equations describing the mathematical model was solved by the Rado IIA method. Random vibration was modeled using digital Fourier transformation. The modeling results were analyzed by discrete Fourier transformation and short-time Fourier transformation.
 RESULTS AND CONCLUSIONS: Rotor movement trajectories were obtained and the results were compared with authors previous experimental data. Upper bound of maximal displacements was obtained. The maximum values of rotor displacement can be used to set the optimal values of blade tip gaps.

Mitigating Rotor Movement During Estimation of Flux Saturation Model at Standstill for IPMSMs and SynRMs

This article proposes a novel method to reduce rotor movement when estimating magnetic flux models for interior permanent magnet synchronous motors (IPMSMs) and synchronous reluctance motors (SynRMs). A rotation reduction technique that considers the flux saturation effect is proposed. A hysteresis controller is used to inject voltages only into the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis and simultaneously into the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axes. The rotation of the IPMSM is reduced by calculating the current at the point where the integral of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current over time becomes zero. In the case of SynRM, the rotation is reduced by calculating the injection voltage magnitudes such that the oscillation frequency of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current is higher than that of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current. The effectiveness of the proposed method was experimentally demonstrated using an 11-kW IPMSM and 1.5-kW SynRM. The proposed technique can be used for the self-commissioning of IPMSMs and SynRMs at a standstill, without rotor locking, or position sensors.

A lightweight model for blade tip image enhancement in helicopter rotor motion parameter measurement system

The helicopter rotor torsion angle is an important motion parameter of a helicopter rotor, which is helpful for the design of helicopter rotor system. The stereoscopic vision-based method measures the torsion angle by computing the directions of the blade tips in the blade tip images. However, the captured blade tip images suffer from blurring and underexposure, which affect the measurement accuracy. To this end, a lightweight deep model is proposed to improve the image quality. In addition, a blade tip image dataset is proposed to train the network. Corresponding experiments demonstrate the effectiveness of the proposed model. Compared to competitive methods, our model stands out with fewer parameters and faster inference time.

Fractional Order Active Disturbance Rejection Control for Canned Motor Conical Active Magnetic Bearing-Supported Pumps

Active magnetic bearings (AMBs) are electromagnetic mechanism systems in which non-contact bearings support a rotating shaft using attractive forces generated by electromagnets through closed-loop control. For complete support of a five degree of freedom (DOF) rotor system, most AMB structures include two radial actuators and one for the axial direction. Conical active magnetic bearings (CAMBs) is one of the development directions of conventional magnetic bearings in which the requirement of the axial bearing can be eliminated. In this paper, we propose a structure with a CAMB integrated into a canned motor pump to eliminate the need for mechanical bearings and shaft seals. However, this system necessitates a more complicated control strategy due to a significant coupling effect between rotor motion and hydrodynamic disturbances. This paper presents a fractional order active disturbance rejection control (FOADRC) including a fractional order extend state observer (FOESO) and a proportional derivative controller (PD) to track and reject lumped disturbances actively. The proposed controller achieves better performance than the integer-type ADRC and traditional PID controller. The control performance of the proposed FOADRC is illustrated in terms of very good disturbance rejection capability that is demonstrated through MATLAB/Simulink simulation results.

Active Power Control of DFIG Wind Turbines for Transient Stability Enhancement

This paper proposes an adaptive Dynamic Power Reduction (aDPR) scheme for Type-3 Wind Turbine-Generators (WTGs) to enhance transient stability of synchronous generators (SGs), with benefits of increasing transfer limits on already fully loaded transmission paths. The scheme consists of three components to deal with a fault close to a SG. Initially, the WTG curtails its active power to a predefined level to act as a dynamic brake for the SG. Then the controller monitors the rate of change of frequency to adaptively ramp the WTG back to its original power output while minimizing the WTG pitch and rotor motion. Finally, to reduce the risk of second-swing instability, the converter uses its reactive current to damp SG power swings. The aDPR scheme can be classified as a remedial action scheme and is enabled if its action can ensure transient stability. To demonstrate the effectiveness of aDPR and to benchmark it against other WTG active current and frequency feedback control techniques, a single-machine infinite-bus system with one WTG is utilized. Next, an aDPR enabled WTG is integrated in the NPCC 68-bus system. Finally, the aDPR controller’s ability to prevent transient instability is demonstrated on the two-area system.

Galvanically Isolated On-Board Charger Fully Integrated With 6-Phase Traction Motor Drives

The rapid spread of electric vehicles is pushing for more and more compact and reliable e-axle architectures. In this scenario, the integration of the on-board battery charger with the traction drive can be a feasible way to reduce the embedded volume and number of components. Anyway, integrated chargers often present safety issues due to the absence of an isolation stage. In this work, a solution is proposed for integrating the on-board battery charger with the traction drive of road electric vehicles equipped with a 6-phase traction motor drive. The proposed charger is deeply integrated within the e-drive powertrain, to reduce the cost and volume of the e-axle with respect to non-integrated solutions, but still providing galvanic insulation, differently from all fully integrated charger in the literature. Dedicated control strategies are developed and tested for regulating the AC grid current at unitary power factor and low THD, and to avoid torque production or rotor movement during charging independently from the rotor position. Extensive simulation results show the feasibility of the proposed solution, together with a proof-of-concept validation on a commercial traction motor.

On stability of motion of unbalanced gyroscope

In this paper we consider the stability of motion of an unbalanced gyroscope with a flexible shaft in gimbal suspension.Gyroscopes are used to control the stability of boom tower cranes. First, we consider the linear Hamiltonian systems of differential equations. The Hamiltonian systems arise in transportation problems. We prove several properties of the Hamiltonian matrix. Next, we consider the normalization of Hamiltonian matrix. We solve the system of matrix equations to find the generating function of the canonical transformation. Further, we find the symmetric solution of nonlinear algebraic matrix Riccati equation in one case. We propose the analytical method for solving this equation. Further, we investigate the motion of gyroscope. We consider the system of equations of motion of the gyroscope rotor and frames in the first approximation. We consider eigenvalues of characteristic equation corresponding to the motion equations. We obtain stability criterion in several cases.

Fast rotating dipole array inducing large dielectric response in a Ruddlesden–Popper hybrid perovskite ferroelastic

A 2D RP hybrid perovskite shows dynamic rotating motion of the polar rotor which inducing ferroelasticity and a tremendous dielectric response. This study provides a new vision for the development of dynamic functional materials.