Stationary Parts Research Articles

Influence of choosing materials on 6/4 switched reluctance motor performance

The Switched Reluctance Motor (SRM) is used in many industrial applications that require high torque due to its ability to achieve high and efficient performance, simplicity, low material costs and ease of design. This motor functions on the principle of generating motion by attracting and repulsing magnetic cores. The SRM is characterized by the efficient use of energy in applications that require rapid changes in speed and has a higher resistance to shocks and vibrations. Among the essential factors that affect the performance of the SRM motors are the embrace of poles stator and rotor, dimensions, the size of the motor, the shapes of rotor geometry and the number of stator and rotor poles. This paper aims to study the effect of material selection on improving the SRM performance. First, we created a basic design of the SRM with appropriate characteristics to obtain the best operation conditions of high speed and torque. Then, we applied different materials and compared the obtained results using the ANSYS RMxprt tool. We focused on studying the effect of selecting materials in the rotor and stator parts on the SRM 6/4 performance through the efficiency, total losses, speed and rated torque. After comparing and analyzing the basic results, a two-dimensional model of the SRM was created using the ANSYS Maxwell 2D tool to evaluate the motor’s performance. The analysis includes the curves of torque, speed, current, flux linkages and voltage, in addition to the variation of flux lines and magnetic flux density. The results were analyzed using the finite element method (FEM), which is characterized by speed and accuracy in electromagnetic analysis and various data.

Analysis of longitudinal-vertical coupling vibration of four hub motors driven electric vehicle under unsteady condition

The influence of hub motor unbalanced magnetic force (UMF) on the vibration of electric vehicle under steady state conditions has been known, but under unsteady conditions, the hub motor UMF will change with the vehicle operation condition, and there would exist complex coupling vibration for the hub motors driven electric vehicle. Here, the longitudinal-vertical coupling dynamics of the four hub motors driven electric vehicle under unsteady condition is studied. Integrating the motor electromagnetic excitation and electric vehicle dynamics, a longitudinal-vertical coupling dynamics model of the four hub motors driven electric vehicle is established. Based on the variable switching frequency field-oriented control model, analytical model of the UMFs acting on the motor stator and rotor parts under unsteady condition are developed. For model validation, a four hub motors driven electric vehicle has been tested, the accuracy of the longitudinal-vertical coupling dynamics model established in this paper was verified. Then, longitudinal-vertical coupling vibration characteristics of the four hub motors driven electric vehicle under road excitation and coupling excitation are analyzed. The results show that the longitudinal and vertical movement of the four hub motors driven electric vehicle is coupled by hub motor. In addition, under unsteady condition, the motor UMFs will cause vertical vibration of the electric vehicle body and hub motor stator, the vibration shows order characteristics including low order harmonic hfc and inverter switching frequency sideband harmonic k1 fs±k2 fc ( fc = pn/60, fs is inverter switching frequency, k1 and k2 are positive integers, p is the number of pole pairs and n is motor speed.). The motor electromagnetic torque will cause longitudinal vibration of the electric vehicle body, the vibration shows order characteristics including harmonics fs±3 fc and 2 fs. The main harmonic of vehicle body pitch angle acceleration is 2 fs.

Effects of bubble content on the rotor behavior and characteristics of hydraulic pumps used for automatic transmissions

In automatic transmissions, hydraulic oil in the oil sump is strongly agitated by gears during operation; thus, the oil is mixed with great amounts of air. Air-mixed oil is sucked and discharged by a hydraulic pump to shift the gears. Although air bubbles mixed in the oil may affect the behavior of the rotors, driving torque, and discharge flow rate, they have hardly been measured. In this study, we measure them using a balanced vane pump and a gerotor pump used for automatic transmissions under varying air bubble contents and operating conditions. The experimental results revealed that the inclusion of air bubbles in the oil somewhat influenced the rotor behavior of both test pumps but it did not seem to increase the contact between the rotor and the surrounding stationary parts. Furthermore, as the bubble content increased, friction torque decreased to some degree, while discharge flow rate decreased to a great degree. This work proposed a new friction torque model, in which bubble content is included as a parameter, and the proposed model demonstrated relatively good agreement with the measured friction torque characteristics. The results also revealed that the rotor behavior and friction torque characteristic were mainly affected by bubble content and less so by bubble size.

A hierarchical modeling strategy for condition monitoring and fault diagnosis of wind turbine using SCADA data

The development and utilization of wind energy can help promote the carbon neutrality. Condition monitoring and fault diagnosis based on supervisory control and data acquisition (SCADA) can effectively improve wind turbine reliability and reduce operation and maintenance (O&M) costs. However, the complex data characteristics (e.g., time-varying and distribution-free) make it difficult to use a unified model to comprehensively evaluate the turbine state. To finely detect and analyze the turbine faulty mode, a hierarchical condition monitoring and fault diagnosis (CMFD) method is proposed, which consists of variable-level and turbine-level. First, the SCADA data is divided into two blocks: the nonstationary part with time-varying distribution, and the stationary part with time-invariant but non-Gaussian distribution. At the variable-level, this paper proposed a local monitoring unit based on sparse cointegration analysis (SCA) and independent component analysis (ICA) to detect faulty samples of different variable blocks. And the fault-related variables are isolated based on the proposed distributed reconstruction. At the turbine-level, the evaluation results from variable-level are fused: on the one hand, Bayesian inference is used to integrate monitoring statistics of stationary and nonstationary parts to comprehensively evaluate the operational state of the turbine; on the other hand, the root fault subsystem is deduced from the fault-related variables isolated from the two parts based on Gaussian process regression. The proposed method is applied in the operation and maintenance of a real wind farm, and the performance advantages are verified by the comparison with popular benchmarks.

A case study on the failure analysis of 1 hp house hold electrical submersible pump in Prayagraj India

This paper deals with the failure analysis of a 1 HP household electrical submersible pump in Prayagraj city. The city is surrounded by two rivers i.e. the Ganga and the Yamuna. Therefore, domestic submersible pumps are widely used in the region. Hard water and sand particles cause various problems with the pump. The submersible pump consists of a pump section and a motor section. The failure analysis of the motor section consists of failure of the rotor, stator, cable and other parts. Similarly, the pump section consists of failure of the impeller, diffuser and other parts. Prevention methods for all failed components have also been discussed in this paper. The failure of a submersible pump can be summarized into three major categories i.e. mechanical failure (breakage, corrosion, dislocation and leakage), electrical failure (cable failure, motor failure, and connection severances) and operational failure (high temperature, high pressure and multiphase flow).

Experimental and Numerical Investigation on Finned Vortex Reducer in a Rotating Cavity with a Radial Inflow

In aero-engines, a secondary air system is used to cool the rotor discs and seal cavities between rotor and stator parts. The pressure loss caused by bleed air can be effectively reduced by setting the finned vortex reducer. Thus, the bleed system design can be optimized by researching the flow structure and pressure loss of each section in the cavity with a finned vortex reducer. In this study, the influence of different installation positions of a finned vortex reducer on the pressure loss characteristics was investigated through experimental and numerical simulation methods, focusing on the radial inflow of the secondary air system. The results indicate that the inlet and outlet positions of the fins affect the flow structure in the cavity. The aerodynamic parameters (rotational Reynolds number ReΦ and mass flow rate coefficient Cw), together with the inlet and outlet radii of the fins, influence the pressure loss in the cavity. Considering the swirl ratio β constrained by the fins, a pressure loss model was established, which showed good agreement with the experimentally measured pressure loss. This model reflects the impact of the inlet and outlet positions of the fins on the pressure loss characteristics.

Improved BIGRU Model and Its Application in Stock Price Forecasting

In order to obtain better prediction results, this paper combines improved complete ensemble EMD (ICEEMDAN) and the whale algorithm of multi-objective optimization (MOWOA) to improve the bidirectional gated recurrent unit (BIGRU), which makes full use of original complex stock price time series data and improves the hyperparameters of the BIGRU network. To address the problem that BIGRU cannot make full use of the stationary data, the original sequence data are processed using the ICEEMDAN decomposition algorithm to derive the non-stationary and stationary parts of the data and modeled with the BIGRU and the autoregressive integrated moving average model (ARIMA), respectively. The modeling process introduces a whale algorithm for multi-objective optimization, which improves the probability of finding the best combination of parameter vectors. The R2, MAPE, MSE, MAE, and RMSE values of the BIGRU algorithm, ICEEMDAN-BIGRU algorithm, MOWOA-BIGRU algorithm, and the improved algorithm were compared. An average improvement of 14.4% over the original algorithm’s goodness-of-fit value will greatly improve the accuracy of stock price predictions.

Quasinormal modes and echo effect of a cylindrical anti–de Sitter black hole spacetime with a thin shell

This paper investigates the quasinormal mode (QNM) vibrations of a rotating cylindrical black hole (or black string) spacetime that is surrounded by a thin shell rotating synchronously with the black string's axis. The existence of the thin shell leads to a piecewise metric of the black hole spacetime beyond the horizon, which is divided into two stationary spacetime parts by the radius of the thin shell. As a result, the potential function $V(r)$ of the QNM equation is also discontinuous. To solve the QNM equation with the discontinuous potential function, we propose two methods, the matrix method and the generalized Horowitz-Hubeny method. We find that the influence of the thin shell can reduce the QNM frequency of the black string while alleviating their amplitude decay rate. Our suggested method can be easily applied to other QNM calculations of black hole spacetime with discontinuous potential function, thus facilitating investigations into more intricate and realistic black hole spacetimes, such as those with accretion disks. Additionally, the finite difference method is employed to investigate the spacetime too. This analysis discloses a substantial gap in the potential function when the thin shell's mass and charge achieve sufficiently high values, resulting in the outer spacetime nearing gravitational collapse and extreme black hole scenarios. Within this gap, the QNM wave displays oscillations, producing an echo effect. Moreover, it is established that the closeness of the spacetime to the collapse threshold and charge extremality have positive correlation with the beat interval of this echo.

Asymptotic phase-locking and synchronization in two-qubit systems

The paper concerns spontaneous asymptotic phase-locking and synchronization in two-qubit systems undergoing continuous Markovian evolution described by Lindbladian dynamics with normal Lindblad operators. Using analytic methods, all phase-locking-enforcing mechanisms within the given framework are obtained and classified. Detailed structures of their respective attractor spaces are provided and used to explore their properties from various perspectives. Amid phase-locking processes those additionally enforcing identical stationary parts of both qubits are identified, including as a special case the strictest form of synchronization conceivable. A prominent basis is presented which reveals that from a physical point of view two main types of phase-locking mechanisms exist. The ability to preserve information about the initial state is explored and an upper bound on the amplitude of oscillations of the resulting phase-locked dynamics is established. Permutation symmetry of both asymptotic states and phase-locking mechanisms is discussed. Lastly, the possibility of entanglement production playing the role of a phase-locking witness is rebutted by three analytically treatable examples.

CFD Analysis of a Transient Rotor-Stator Axial Steam Turbine Stage

An axial steam turbine stage has both stationary and rotating components, which are coupled together in a CFD model by multiple frames of reference. There are three types of interface techniques available to exchange the information between the different frames of reference namely frozen rotor, stage, transient stator rotor. Both frozen rotor and stage interfaces are used in steady state analysis. The operation of axial turbine is inherently an unsteady process. The aerodynamic interaction between the rotating part and the stationary parts are the important contributor to the unsteadiness of the flow present in the turbine. Neither of the two interfaces implemented in the steady state CFD analysis is capable of predicting the unsteady effects resulting from the rotor-stator interaction due to their relative position change. The third type of interface, the transient stator-rotor interface, is available to simulate the fluid motion caused by the relative movement between a rotor and stationary components in axial turbine. Although enormous computer resources are needed for this modelling, it simulates real flow physics best of all, while steady or quasi-steady numerical approaches only approximate the real flow, because they neglect important effects of blade row interactions. The paper presents the CFD analysis carried out for an axial steam turbine stage with three different interface techniques and compares the results.

Analysis and Experiment of a Dual Stator/Rotor PM and Winding Flux Modulated PM Machine

In this article, a high torque density flux modulated permanent magnet machine topology with dual permanent magnets and dual armature windings (DMDA-FMPM) is proposed. The most notable feature of DMDA-FMPM is that both stator and rotor parts consist of PMs and armature windings so that a single air gap and a simple structure are kept. Moreover, both the PMs can interact with both the windings to produce four torque components, and the output torque on the shaft is the superposition of these four torque components. Consequently, extremely high torque is expected. This paper firstly introduces the topology and main drive circuit of DMDA-FMPMs. Then the basic operation principle and slot/pole combination equation are illustrated, taking the proposed topology as an example. Afterward, the electromagnetic performance, including flux line distribution, flux density, back electromotive force (EMF), torque quality, and power factor, is analyzed by finite element analysis (FEA). Besides, the fault-tolerance of windings failure and PM demagnetization is discussed. A prototype is designed and tested to verify the proposed DMDA-FMPM. The experimental results match well with the FEA and theoretical analysis. DMDA-FMPM has excellent torque performance and fault-tolerant capability. Finally, the possible applications, operating modes, advantages, and drawbacks are discussed comprehensively.

Structural and Functional Diversity of Two ATP-Driven Plant Proton Pumps.

Two ATP-dependent proton pumps function in plant cells. Plasma membrane H+-ATPase (PM H+-ATPase) transfers protons from the cytoplasm to the apoplast, while vacuolar H+-ATPase (V-ATPase), located in tonoplasts and other endomembranes, is responsible for proton pumping into the organelle lumen. Both enzymes belong to two different families of proteins and, therefore, differ significantly in their structure and mechanism of action. The plasma membrane H+-ATPase is a member of the P-ATPases that undergo conformational changes, associated with two distinct E1 and E2 states, and autophosphorylation during the catalytic cycle. The vacuolar H+-ATPase represents rotary enzymes functioning as a molecular motor. The plant V-ATPase consists of thirteen different subunits organized into two subcomplexes, the peripheral V1 and the membrane-embedded V0, in which the stator and rotor parts have been distinguished. In contrast, the plant plasma membrane proton pump is a functional single polypeptide chain. However, when the enzyme is active, it transforms into a large twelve-protein complex of six H+-ATPase molecules and six 14-3-3 proteins. Despite these differences, both proton pumps can be regulated by the same mechanisms (such as reversible phosphorylation) and, in some processes, such as cytosolic pH regulation, may act in a coordinated way.

Avoiding disc collisions and nonlinear vibration of unbalanced rotors by means of position control of the rotor journal mounted in magnetorheological hydrodynamic bearings

Rotors of rotating machines are often supported by hydrodynamic bearings. Imbalance, ground vibration, assembling inaccuracies, and eccentric position of the shaft journal in the bearing hole may result in collisions between the rotors and their casings if the gap between the rotating and stationary parts is narrow. This can be avoided by controlling the position of the rotor journal in the bearing hole by changing stiffness of the oil film. This method of controlling parameters of the lubricating layer is offered by application of magnetically sensitive fluids. A new design of magnetically controllable hydrodynamic bearing was developed. The magnetic flux is generated by an electric coil. It passes through the bearing housing, and the layer of lubricant and goes back to the coil core. Magnetic induction in the bearing gap is calculated by application of the Kirchhoff and Hopkinson laws. The pressure distribution in the oil layer is obtained by solving the Reynolds equation adapted to lubricants exhibiting yielding shear stress, the magnitude of which depends on magnetic induction. Results of the computational simulations showed that application of a magnetic field acting on magnetorheological lubricant in the bearing gap makes it possible to prevent impacts between the rotor and its casing in a certain velocity interval, or at least to reduce magnitude of the impact forces if collisions occur. The principal contribution of the conducted research is the proposal of a new approach based on semiactive principle to controlling position of rotors working in limited space and obtaining more information on interaction between the rotors and magnetically controllable hydrodynamic bearings during the operating conditions when collisions between the rotor and its stationary part take place.

Transient Numerical Simulation of a Large-Sized Cement-Mill Fan for Performance Prediction

In many engineering applications, particle-laden flows are a necessary part of the conveying process, but in other situations, they could have unintended consequences that must be avoided. As a part of the exhausting process, the induced cement-mill fan (FN-280) installed in a cement plant operates under critical conditions with the presence of high content of cement particles. Over time the dragged solid particles erode the rotating and stationary parts of the fan causing their damage. If one decides on a numerical approach to predict regions most prone to erosion and track the solid particle's trajectory within the fan domain by assuming a one-way coupling regime between the continuous and discrete solid phases, a deep insight into the flows physics within the centrifugal fan is required. With this aim, a three-dimensional numerical approach for the hole unsteady flow in a large-sized industrial centrifugal fan has been carried out in this paper. A fully resolved sliding mesh approach was employed to take into account the unsteady interaction between the impeller and the discharge volute. Based on the characteristic performance curves, the numerical results of the unsteady simulation at four operating conditions are validated with the experimental data. The comparisons reveal that the results of the unsteady simulation are in an acceptable level of agreement with the experiment, demonstrating the validity of the modelling approach adopted in this study.

Topology optimization for fluid flow devices modeled through the Multiple Reference Frame approach

Fluid flow devices have been algorithmically designed through optimization methods, and this task is relatively complex for flow machines. Particularly, one recent development is the use of the topology optimization method for this task, which is capable of achieving possibly non-intuitive geometries and even auxiliary structures, such as splitter blades without ever imposing them as a condition for the design. The design of the rotating part of the rotor has already been previously considered. However, in the presence of stationary parts surrounding the rotor, such as diffuser blades, the fluid flow behavior may change, meaning that it may be interesting to consider this different dynamic in the design. One possible approach for this is the Multiple Reference Frame approach, which considers the fluid flow dynamics inside the rotor being computed in the rotating reference frame, whilst the fluid flow dynamics outside the rotor is being computed in the stationary reference frame. In particular, this implies the need for some changes in the topology optimization formulation, also impacting the choice of objective functions. Therefore, here the topology optimization method is formulated for the Multiple Reference Frame approach, and a new combination for the multi-objective function is proposed. The discrete design variable configuration from the Topology Optimization of Binary Structures approach is adopted with some adjustments to account for the Multiple Reference Frame approach. The fluid flow is chosen to be laminar or turbulent. Numerical examples are presented in 2D for the rotor-diffuser in order to consider some aspects that affect the overall topology optimization design.

Physics-Based Reduced-Order Model for Liquid Ring Pumps

Abstract Liquid-ring vacuum pumps, by not having solid-solid contacts at interfaces where moving and stationary parts meet, are efficient and robust with considerable potential for further improvements on efficiency, performance, and range of operations. In this study, a physics-based reduced order model was developed for the preliminary design of liquid-ring pumps. The model developed accounts for the dominant physical processes created by the pump's key design and operating parameters: eccentricity, impeller-tip radius, impeller-hub radius, pressure at the pump's inlet and exit, and the impeller's rotational speed. The model developed can predict the shape of the liquid ring, the amount of air ingested and discharged by the pump, the power consumed by the pump as well as the pressure of the gas and liquid in the pump between the blades of the impeller as a function of those design and operating parameters. The predictions made by the model on the flow rates of the gas ingested by the pump and the power consumed by the pump were compared with experimental data, and good agreements were found.

Nanoporous Films with Oriented Arrays of Molecular Motors for Photoswitching the Guest Adsorption and Diffusion.

Molecular motors are fascinating nanomachines. However, constructing smart materials from such functional molecules presents a severe challenge in material science. Here, we present a bottom-up layer-by-layer assembly of oriented overcrowded-alkene molecular motors forming a crystalline metal-organic framework thin film. While all stator parts of the overcrowded-alkene motors are oriented perpendicular to the substrate, the rotors point into the pores, which are large enough allowing for the light-induced molecular rotation. Taking advantage of the thin film's transparency, the motor rotation and its activation energy are determined by UV/Vis spectroscopy. As shown by gravimetric uptake experiments, molecular motors in crystalline porous materials are used, for the first time, to control the adsorption and diffusion properties of guest molecules in the pores, here, by switching with light between the (meta-)stable states. The work demonstrates the potential of designed materials with molecular motors and indicates a path for the future development of smart materials.

Analysis of Signal Processing Methods to Reject the DC Offset Contribution of Static Reflectors in FMCW Radar-Based Vital Signs Monitoring

Frequency-modulated continuous wave (FMCW) radars are currently being investigated for remote vital signs monitoring (measure of respiration and heart rates) as an innovative wireless solution for healthcare and ambient assisted living. However, static reflectors (furniture, objects, stationary body parts, etc.) within the range or range angular bin where the subject is present contribute in the Doppler signal to a direct current (DC) offset. The latter is added to the person's information, containing also a useful DC component, causing signal distortion and hence reducing the accuracy in measuring the vital sign parameters. Removing the sole contribution of the unwanted DC offset is fundamental to perform proper phase demodulation, so that accurate vital signs monitoring can be achieved. In this work, we analyzed different DC offset calibration methods to determine which one achieves the highest accuracy in measuring the physiological parameters as the transmitting frequency varies. More precisely, by using two FMCW radars, operating below 10 GHz and at millimeter wave (mmWave), we applied four DC offset calibration methods to the baseband radar signals originated by the cardiopulmonary activities. We experimentally determined the accuracy of the methods by measuring the respiration and the heart rates of different subjects in an office setting. It was found that the linear demodulation outperforms the other methods if operating below 10 GHz while the geometric fitting provides the best results at mmWave.

Analysis and Experimental Verification of Radial-Gap Two-Degree-of-Freedom Motor Based on a Magnetic Screw Structure

This article proposes a radial-gap two-degree-of-freedom motor based on a magnetic screw structure. The proposed motor is composed of stator parts, rotor parts, and a mover part, and can generate torque and thrust force simultaneously and independently. Additionally, the motor can generate a large thrust force with the magnetic screw structure. In the proposed motor, the rotor parts and mover part, which act as the nut and screw of ball screws, are coupled with each other by means of magnetic force. Therefore, there is no friction between the rotor parts and mover part. The proposed motor can not only contribute to the minimization of multidegree-of-freedom systems, such as industrial robots but also improve the energy efficiency of robots. This article examines the effectiveness of the proposed motor through analysis and experimental results.

Light-Driven Molecular Whirligig

A unidirectional light-driven rotary motor was looped in a figure-of-eight molecule by linking two polymer chains between its stator and rotor parts. By properly tuning the size of these linkers, clockwise rotation of the motor under UV light was shown to create conformationally strained twists between the polymer chains, and in this tensed conformation, the energy stored in the molecular object was sufficient to trigger the reverse rotation of the motor back to its fully relaxed state. The functioning principle of this motorized molecular device appears very similar to that of macroscopic whirligig crafts used by children for fun. In addition, we found that in its out-of-equilibrium tensed state, the fluorescence emission of the molecular motor increased by 500% due to the mechanical constraints imposed by the polymer chains on its conjugated core. Finally, by calculating the apparent thermal energies of activation for the backward rotations at different levels of twisting, we quantitatively determined a lower estimate of the work generated by this rotary motor, from which a torque and a force were extracted, thus answering a long-term open question in this field of research.