Rotor Segment Research Articles

Potential Evaluation of Twin-Screw Air Expanders with Dual-Lead Rotors Used in PEMFC Systems

The reduction in the power cost of air supply systems has emerged as a critical challenge in the development of polymer electrolyte membrane fuel cells. This study proposes the use of dual-lead rotors to improve the performance of twin-screw expanders for the purpose of boosting expanders’ recovery power and consequently lowering the power cost of the air supply subsystem, which is hardly investigated in previous publications. For this purpose, a mathematical model is built to assess the potential of improving the expander performance by means of the dual-lead rotors. And the influence of lead and length of the high-pressure rotor segment and overall rotor length are analyzed. The results demonstrate that the smaller lead and larger length of the high-pressure rotor segment result in better geometric characteristics and thus thermodynamic performance. For example, case #4 with dual-lead rotors exhibits a larger rotating angle at the suction end and a larger suction area than those of constant-lead rotors by 43° and 100%, respectively, which further lower the suction pressure loss. Compared with constant-lead rotors, the maximum increments in the mass flowrate and indicated power are observed as 45% and 25.4%, respectively. However, the dual-lead rotors could not effectively contribute to an increase in the isentropic indicated efficiency of twin-screw expanders due to the severe leakage, and hence, it becomes crucial to address the leakage issues in twin-screw expanders.

Технологія відновлення форми ротора гідрогенератора

The object of research in this article is the change in the rotor shape during the operation of hydraulic units. The subject of study in this article is the design and geometric state of the shape of a rotor with irregular geometry of hydraulic generators-engines. This study produced a three-dimensional mechanical calculation of the rotor segment for further use during strain gauge tests. Tasks: investigate the peculiarities of the rotor shape restoration technology; to describe the basic assumptions for the three-dimensional mechanical calculation of rotor deformations at the overspeed; and perform a three-dimensional calculation of rotor movements considering the main forces falling on the pole connection, which are obtained using classical methods. The methods used are: finite element method of mathematical modeling of the thermal stress state of nodes. The following results were obtained: a detailed description of the technological process of restoring the shape of the rotor using the hot wedging method is given. Three-dimensional models of the rotor segment were developed, and a three-dimensional mechanical calculation of this model was performed, as a result of which satisfactory values of the displacement of the rotor of the hydraulic generator at the overspeed were obtained, considering the recovery technology. To reconstruct the rotor rim, it is necessary to heat the rotor rim to a temperature difference between the rim and the frame of at least 60 °C. Next, the hot wedging of the rotor rim is performed with the driving of each of the driving wedges by the same amount, which ensures the creation of the necessary diametrical tension between the rim and the frame of the rotor and avoids the displacement of the rotor rim relative to the frame. The control of this process is performed using strain gauges. If necessary, it is necessary to cool the rotor rim until the temperatures of the rim and the frame of the rotor are equal. Conclusions. The scientific novelty consists of a combined approach to the evaluation of the deformation of the rotor rim after restoring its shape, which includes elements of analytical mechanical calculation and calculation in a three-dimensional setting. The presented technology for the rotor restoration process meets European requirements.

Nonlinear vibration of rotating cylindrical shell due to unilateral contact induced tip rubbing impact: Theoretical and experimental verification

This contribution addresses on the theoretical and experimental observations of nonlinear vibration performance of the aero engine drum undergoing repeated impact between the rotor and stator vane segment. By assuming the drum as a rotating thin-wall cylindrical shell, the governing equations of motion of rotating shell under tip rubbing force have been derived in frame of Lagrange equation and verified via the experiment. A fixed point rubbing force model between the clearance of elastic drum and stator vane segment is proposed based on the linear collision force relation. Particularly, an experimental scheme of rotating shell system with unilateral contact is established to simulate the rubbing process of rotating flexible drum and rigid segment. Finally, the influence of rotating speed is investigated in detail and several interesting phenomenon have been confirmed by both analysis and experiment. Overall, the present investigation may suggest an efficient guidance for design of rotating thin-wall shell structures in aero engine and turbo machines.

Segmented Rotor Mutually Coupled Switched Reluctance Machine for Low Torque Ripple Applications

Mutually coupled switched reluctance motors (MCSRMs) are alternatives in the family of reluctance machines that can overcome switched reluctance motor's (SRM's) system-level integration and control challenges by utilizing standard three-phase voltage source inverters. In this article, a novel segmented-rotor, fractional-slot, tooth-wound MCSRM with notched rotor design is presented, which has very low torque ripple compared to other machine types in the SRM family. The torque ripple is reduced to 3.6% without utilizing any current profiling techniques or torque sharing functions. The ripple minimization is achieved primarily through rotor segment shaping, which has a strong influence on stator flux densities, flux linkages, and torque harmonics. The design strategy, along with the optimization details, is presented for a 120 W, 12 slot-8 pole MCSRM. The designed MCSRM is prototyped for experimental verification and validation of the finite element analysis results and design methodology.

Rotor segment split and its optimization of axial-field dual-rotor segmented switched reluctance machine

Switched reluctance machine (SRM) produces vibration and acoustic noise due to the significant torque ripple. The widespread use of SRM is thus limited. For the discussed axial-field dual-rotor segmented switched reluctance machine (ADS-SRM), this paper describes a proposal for a new rotor profile featured by the rotor segment splits. These splits minimize the undesired torque ripple. The effects of each geometric parameter, such as split width and split offset, are investigated using finite-element method (FEM). After optimizing the rotor-segment geometry, the approximately flat-top torque profile is achieved. The motion-coupled analysis further validates the effectiveness of this novel technique. It is found that, by incorporating the optimization of the turn-on and turn-off angles, the torque-ripple coefficient decreases by about 73%, from 0.995 to 0.27. However, the average torque decreases by only 4.2%.

Optimal segmented rotor design for the embedded electrical machine for the more electric aircraft

This study presents the design and analysis of the segmented rotor design for an electrical machine embedded onto the more electric aircraft gas turbine engine shaft. The high-speed operational environment imposes high stress levels due to centrifugal forces; thus, the feasibility of this segmented rotor topology for such application is explored and a suitable design is proposed to overcome mechanical stresses. Finite element structural analysis was performed to compare the mechanical behaviour of a different rotor segment fixing structure and the proposed design. Also, electromagnetic analysis is carried out on a high-speed switched reluctance machine to study the impact of a new design on machine electromagnetic performance.

Analytical magnetic field prediction of flux switching machine with segmental rotor

To deeply study the segmental rotor flux switching machine (SRFSM), an analytical subdomain model is first developed to achieve the magnetic field distribution and electromagnetic performance such as back-electromotive force (EMF), cogging torque, electromagnetic torque, unbalanced magnetic pull, and eddy current losses in the permanent magnet (PM) and rotor support. Then, the number of rotor segments is determined according to the magnetic field modulation theory, and the effect of rotor segment number on the amplitude and total harmonic distortion of speed-normalised back-EMF is investigated as well. Using the proposed analytical model, the magnetic field regulation capacity and PM demagnetisation withstand capacity of the series and parallel hybrid excited SRFSMs are investigated and compared. The PM and parallel hybrid excited SRFSM prototype machines with 12 stator slots and 7 rotor segments are manufactured and tested to validate the proposed analytical model.

Performance analysis of segmented rotor switched reluctance motors with three types of winding connections for belt-driven starter generators of hybrid electric vehicles

PurposeInductance, torque and iron loss are the key parameters of switched reluctance motors for belt-driven starter generators. This paper aims to present the analysis of a segmented rotor switched reluctance motor (SSRM) with three types of winding connections for hybrid electric vehicle applications by using a two-dimensional finite element method.Design/methodology/approachThe rotor of the studied SSRM consists of a series of discrete segments, while the stator is made up of exciting and auxiliary teeth. First, the concept and structures of the different winding connections are introduced. Then, the magnetic flux path of the three types of winding connections for the SSRM is described. Second, the magnetic flux distributions in the three parts, i.e. the stator yoke, the stator tooth and the rotor segment, are described in detail to calculate the iron losses. Third, three SSRMs with the different winding arrangements are analyzed and compared to evaluate the distinct features of the studied SSRM. The analysis and comparison mainly include self-inductances, mutual inductances, phase currents, output torque and iron loss.FindingsIt is found that the self-inductances of the three types of winding connections are almost equal, and only the SSRM1 has a positive mutual inductance. In addition, the current waveforms of SSRM1 and SSRM2 are regular. However, it is irregular in SSRM3. It is shown that SSRM1 has better characteristics, such as higher output torque, high power density, lower torque ripple and iron loss.Originality/valueThis paper proposes and analyzes three novel winding connections for the SSRM to provide guidance for enhancing the output torque and reducing the iron loss to achieve high efficiency.

Magnetic Flux Analysis of a New Field-Excitation Flux Switching Motor Using Segmental Rotor

Recently, a three-phase field-excitation flux switching motor (FEFSM) with salient rotor structure has been introduced with their advantages of easy rotor temperature removal and controllable field excitation coil (FEC) magnetic flux particularly suitable for high torque, high power, and high-speed diverse performances. Nevertheless, the salient rotor structure is found to lead a longer magnetic flux path between stator and rotor producing weak flux linkage along with low torque performances. Besides, the overlap armature coil and FEC windings yield high coil end length, producing much high copper loss and large motor size. In this paper, a new FEFSM using segmental rotor with non-overlap armature coil and FEC windings is proposed. The shorter magnetic flux path of the proposed segmental rotor is noticeably more focused to produce much higher torque while the non-overlap armature and FEC will reduce the copper loss and motor weight. Both FEFSMs with salient and segmental rotors are designed using 2-D-FEA JMAG Designer version 14.1 for comparison. As a result, magnetic flux of the segmental rotor design is 11 times higher than the salient rotor structure mainly due to shorter magnetic flux linkage between two stator teeth and single rotor segment. The torque and power of 0.91 Nm and 293 W, respectively, are obtained from the new FEFSM which are much higher than salient rotor design. In addition, the simulation and experimental results show a good agreement in back-electromotive force amplitude and waveform at various speeds, as well as similar increment of torque versus FEC current characteristics. As the conclusion, the proposed FEFSM with non-overlap and segmental rotor structure has produced much higher flux, with significant improvement of torque and power performances compared with existing FEFSM with salient rotor.

Experimental investigation using CFD for thermal performance of ventilated disc brake rotor

In the present work, different ventilated disc brake rotor configurations were analysed to enhance the heat transfer rate and obtain the uniform temperature distribution in the rotor. CFD code used in this work was validated at using experimental results obtained by conducting experiments on a test rig. The experimental analysis was performed to calculate the mass flow rate and heat dissipation through the rotor. Further, different types of rotor configurations viz. straight radial vane (SRV), tapered radial vane (TRV), alternate long and short vane (ALSV), variable diameter circular pillars (VDCP) were considered for the analysis. A rotor segment of 20° was considered for the numerical analysis due to its rotational symmetry. CFD results were in good agreement with the experiments. The maximum deviation of the numerical results were about 12 % from the experimental results. It is found from the analysis that among the different types of rotor configurations; variable diameter circular pillars (VDCP) rotor gives better rate of heat dissipation with more uniform temperature distribution in the flow passages. Hence for modern high speed vehicles VDCP rotor may be more appropriate.

Performance Improvement in the Axial Flux-Segmented Rotor-Switched Reluctance Motor

Axial flux-segmented rotor-switched reluctance motor (SSRM) topology could be a potential candidate for in-wheel electric vehicle application. This topology has the advantage of the increased active surface area for the torque production as compared to the radial flux SSRM for a given volume. To improve the performance of axial flux SSRM (AFSSRM), various stator slot/rotor segment combinations and winding polarities are studied. It is observed that the torque ripple is high for the designed three-phase, 12/8 pole AFSSRM. Therefore, the influence of the stator pole and rotor segment arc angles on the average torque and the torque ripple is studied. In addition, the adjacent rotor segments are displaced with respect to the stator, to reduce the torque dips in the phase commutation region. The proposed arrangement is analyzed using the quasi-3-D finite-element method-based simulation study and it is found that the torque ripple can be reduced by 38%. Furthermore, the low-frequency harmonic content in the torque output is analyzed and compared. The variation of the axial electromagnetic attractive force with displaced rotor segments is discussed. The effectiveness of the proposed technique is verified experimentally.

Numerical investigation of fluid flow and heat transfer characteristics on the aerodynamics of ventilated disc brake rotor using CFD

Ventilated brake discs are used in high speed vehicles. The brake disc is an important component in the braking system which is expected to withstand and dissipate the heat generated during the braking event. In the present work, an attempt is made to study the effect of vane-shape on the flow-field and heat transfer characteristics for different configurations of vanes and at different speeds numerically. Three types of rotor configurations circular pillared, modified taper radial and diamond pillar vanes were considered for the numerical analysis. A rotor segment of 20? was considered for the numerical analysis due to its rotational symmetry. The pre processing is carried out with the help of ICEM-CFD and analysis is carried out using ANSYS CFX 12.1. The three dimensional flow through the brake rotor vanes has been simulated by solving the appropriate governing equations viz. conservation of mass, momentum and energy using the commercial CFD tool, ANSYS CFX 12. The predicted results have been validated with the results available in the literature. Circular pillar rotor vanes are found to have more uniform pressure and velocity distribution which results in more uniform temperature drop around the vanes. The effect of number and diameter of vanes in the circular pillared rotor is studied and the geometry is optimized for better mass flow and heat dissipation characteristics.

Optimized Segmental Rotor Switched Reluctance Machines With a Greater Number of Rotor Segments Than Stator Slots

Segmental rotor switched reluctance machines have been demonstrated to produce significantly more torque than conventional switched reluctance machines because each coil is able to link more magnetic flux. In previous work, the range of topologies studied has been relatively restricted; there has been no consideration of the range of stator tooth and rotor segment number options, and the designs have not been formally optimized in any way. This paper seeks to address this: Using finite-element toolsets for optimization, it describes the resulting machines-uniquely featuring a greater number of rotor segments than stator teeth. This paper assesses the credible tooth and segment options, with each option optimized to maximize torque capability. From this assessment, conclusions are drawn, which contrast each machine's performance based on criteria including torque production and loss. In order to validate this optimization process, a prototype machine is built, and its performance is compared with these predictions.

Effects of Bending Moments and Pretightening Forces on the Flexural Stiffness of Contact Interfaces in Rod-Fastened Rotors

The rod-fastened rotor (RFR) is comprised of a series of discs clamped together by a central tie rod or several tie rods on the pitch circle diameter. The equivalent flexural stiffness of contact interfaces Kc in the RFR is the key concern for accurate rotor dynamic performance analysis. Each contact interface was modeled as a bending spring with a stiffness of Kc and a hinge in this study. The contact states of the contact interfaces, which depend on the pretightening forces and bending moments (static), have effects on Kc. The approach to calculating Kc in two contact states is presented. The first contact state is that the whole zone of the contact interface is in contact; Kc is determined by the contact layer, which consists of asperities of the contact surfaces. Hertz contact theory and the Greenwood and Williamson (GW) statistical model are used to calculate the equivalent flexural stiffness of the contact layer Kcc. The second contact state is that some zones of the contact interface are separated (when the bending moment is relatively large); the equivalent flexural stiffness of the rotor segment Ksf (not including Kcc) decreases, as the material in the separated zone has no contribution to the bending load-carrying capacity of the rotor. The strain energy, which is calculated by the finite element method (FEM), is used to determine Ksf. The stiffness Ksf is equivalent to the series stiffness of the discs of the rotor segment with flexural stiffness of Kd and a spring with bending stiffness of Kcf in the location of the contact interface, so Kc is equal to the series stiffness of Kcc and Kcf in the second contact state. The results of a simplified RFR indicate that, for a fixed pretightening force, Kcc decreases with bending moments in the first contact state, whereas increases with bending moments in the second contact state. In addition, Kcf and Kc decrease abruptly with the increase of bending moments in the second contact state when the rotor is subjected to a relatively large pretightening force. Finally, the multipoint exciting method was used to measure the modal parameters of the experimental RFR. It is found that the experimental modal frequencies decrease as the pretightening force decreases.

Dynamic Behaviour Analysis of Linear Rotor-Bearing Systems using the Complex Transfer Matrix Technique

major and minor axis of elliptical whirling orbits, a,b ! respectively A area of cross-section ! bearing matrix [B] ! C bearing clearance ! cross-coupled bearing damping coefficients Cxy,Cyx ! direct bearing damping coefficient Cxx,Cyy ! direct bearing foundation damping coefficients Cfxx,Cfyy ! cross-coupled bearing foundation damping coefCfxy,Cfyx ! ficients d diameter of the shaft ! D diameter of the disk ! diameter of the bearing Db ! disk matrix [D] ! eccentricity of the disk in X and Y directions, reex#, ey# ! spectively E Young’s modulus of rotor ! EI bending stiffness ! G shear modulus ! h disk thickness ! transverse and polar mass moments of inertia of Id, Ip ! the disk, respectively j imaginary unit ! transverse and polar area moments of inertia of I,J ! the rotor, respectively form factor Ks ! cross-coupled bearing stiffness coefficients Kxy,Kyx ! direct bearing stiffness coefficients Kxx,Kyy ! direct bearing foundation stiffness coefficients Kfxx,Kfyy ! cross-coupled bearing foundation stiffness coefKfxy,Kfyx ! ficients l length of the rotor segment ! length of the bearing Lb ! m mass of the rotor segment for unit length ! mass at the supported bearing mb ! mass of the unbalance me ! mass of the disk Md ! bending moments about X and Y axes, respecMx,My ! tively shear forces along X and Y axes, respectively Qx,Qy ! radius of the whirl rw ! state vectors [S] ! transfer matrix [T] ! displacement along X and Y axis, respectively X,Y ! slopes in X-Z and Y-Z planes, respectively !, ! slopes in X-Z and Y-Z planes due to shear, re!t,t ! spectively slopes in X-Z and Y-Z planes due to bending, re!b,b ! spectively rotating and whirling speeds, respectively #,$ ! mass density % ! coefficients of viscosity & !

Effect of Compounding Conditions on Mechanical Properties of Glass Fiber-Reinforced Polyamide-6

Abstract Glass fiber-reinforced polyamide-6 (GFPA-6) was compounded using a HYPERKTX46 twin screw extruder with three different types of screw segments (rotor segments, kneading disc segments and turbine segments). Based on the ‘neural network’ regression analysis, we investigated the effects of compounding conditions, such as screw configurations, screw rotation speed, and production rate on mechanical properties, such as tensile, flexural and impact strength of GFPA-6. It was found that the mechanical properties of GFPA-6 changed in different ways with compounding conditions (screw rotation speed and production rate), depending on the type of screw segments. It was also found that the rotor segment exhibited good mechanical properties in wider ranges of compounding conditions than the kneading disc segment and the turbine segment, probably due to its mild and uniform mixing capability.

Calculation in the Field of Segmental Rotor Machines Taking into Account Winding Harmonics and Rotor Airgap Irregularities

The stator mmf over a segment of the segmental rotor reluctance machine is treated as an infinite array of generators feeding a common busbar, and the magnetic potential of the rotor segment is obtained as the potential of the equivalent busbar. The rotor potential for any airgap profile is readily obtained and it is shown how the method may be extended to axially laminated machines and those of the flux barrier type. This approach is derived from considering the flux due to a single stator conductor carrying current.