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The increase of power and speed requirement on the electric machine has imposed a concern on the high losses at high speed, especially on the winding AC losses. To deal with this, a flat rectangular wire is proposed to minimize the winding AC loss due to the skin effect and proximity effect. The impact of conventional circular wire strands on AC loss are analyzed and compared with the proposed flat rectangular wire configuration. Both open slot and semi-closed slot stator structures are evaluated. Finally, a 24 slots, 16 poles fractional slot concentrated winding (FSCW) permanent magnet (PM) synchronous machine prototype using flat rectangular wire and open slot stator is built to demonstrate the manufacturing of flat rectangular wire.

This work aims to study the design principle of hairpin winding topology with high parallel path numbers per phase. Hairpin winding offers the advantages of high slot fill factor and automated winding process, which promote its application in the traction motors. As the motor power and speed continuously going up, the large size of the conductors are prone to proximity loss and eddy current loss due to the non-uniform current distribution, and the series connected turn numbers per phase are limited by the DC voltage. Therefore, this work is to investigate the hairpin winding design approach with high parallel path numbers per phase to meet the voltage and current constraints, and to keep the front and back connections having equal coil length as much as possible, respectively. The effect of parallel path numbers on the AC loss will be analyzed using finite-element analysis. The impact of asymmetric conductor configurations has also been evaluated.

This paper presents a novel electric motor solution to tackle the increasing demand on the traction motor for electric vehicles. The proposed electric motor has a 24 slots 10 poles fractional slot two-slot pitch winding and a PM-assisted synchronous reluctance (PMaSynR) rotor with arc-shaped barriers. First, the winding layout will be introduced. Then, a comparison with other winding layouts will be detailed. The benefits of the proposed solution including low torque ripple and high reluctance torque capability will be demonstrated. All this confirms that it is a good trade-off solution for traction application.

In recent years, synchronous reluctance (Syn-Rel) machines are research hotspots in variable speed motor drives due to their robust rotor structure and wide constant power speed range (CPSR). More practically, when kVA limitation is considered, embedded permanent magnets (PMs) have been widely adopted in Syn-Rel rotors to further increase power density as well as power factor. In this paper, the authors have investigated the potential of PM-assisted Syn-Rel machine to be the next generation electrical propulsion motor topology for automotive application, with special attention put on a key geometric parameter, i.e., airgap length. In MTPA region, the influence of airgap length on different torque components has been analyzed in detail based on the frozen permeability method. In field weakening region, the variation trend of several key performance such as peak power, iron loss and torque ripple have been investigated along with airgap length. It is found that with specifically high level of electric and magnetic loading, there exists optimal value of airgap length to achieve high power density based on specific cooling and kVA limitation. Numerical FEA and experimental tests are associated to validate the conclusions.

This paper presents a five-phase permanent magnet (PM) vernier machine topology equipped with a two-slot pitch winding. The two-slot pitch winding provides a trade-off between fractional slots concentrated winding (FSCW) and integrated slot distributed winding (ISDW) PM vernier machines. First, the development and basic structure of the fivephase PM vernier machine with auxiliary teeth are depicted. Then, the PM vernier machine with proposed two-slot pitch fractional slot winding is explained. Finally, the five-phase PM vernier machines with conventional ISDW and FSCW configuration are analyzed and compared with the proposed PM vernier machines with two-slot pitch fractional slot winding. The benefits of introducing two-slot pitch windings are quantitatively analyzed and verified by finite-element analysis (FEA). This analysis confirms that a higher back EMF and torque density can be achieved in this topology while keeping a reasonable power factor.

During partial oxidation of methane (POM), the greatest challenge is to maintain the thermal stability of the catalyst at high temperatures. One of the most effective ways to improve thermal stability is to construct core-shell structure. Herein, using a microemulsion method, we synthesized a core-shell Ni/nanorod-CeO2@SiO2 catalyst, in which the Ni nanoparticles were supported on the CeO2 nanorods and encapsulated by SiO2 shells. Based on a series of characterizations, we found that the Ni particles are of nanosize (2.2 nm) and the thickness of the SiO2 shell is about 8 nm in the core-shell catalyst. Moreover, the Ni/nanorod-CeO2@SiO2 catalyst can perfectly maintain rod-like structures of the CeO2 support and enhance interaction between the metal Ni and CeO2, significantly reducing the sintering of metal Ni particles at high temperatures. Therefore, the as-prepared Ni/nanorod-CeO2@SiO2 catalyst shows high catalytic activity and good thermal stability during the POM reaction.

Polycarboxylate superplasticizers with different structural parameters were synthesized by isobutylene polyoxyethylene ether, acrylic acid and ammonium persulfate as raw materials from the perspective of molecular design. The influence of polycarboxylate superplasticizer on cement adsorption was characterized by cement adsorption capacity test and fluidity test, etc. At the same time, the adsorption change of polycarboxylate superplasticizer on the surface of cement particles was also revealed. It was found that the best adsorption and dispersion properties on cement paste were obtained under the heating synthesis process when the structure of the water reducing agent was designed to have a weight average molecular weight of 55128, a macromonomer conversion rate of 84.61%, and a side chain density of 0.1725. For the normal temperature process, when the weight average molecular weight was 103920, the macromonomer conversion rate 92.03%, and the side chain density 0.3115, the best effects in cement can be achieved.

A dandelion-like SAPO-11 with multiple branches was fabricated by seed-induced steam-assisted conversion (SISAC), which combined an in situ inoculating seed method (in this case, the initial gel was pre-crystallized at 433 K for 24 h) and steam-assisted conversion (SAC) process. The dandelion-like SAPO-11 was fully crystalline and exhibited more acidity, external surface and mesopore volume compared with conventional hydrothermally crystallized SAPO-11, confirmed by Ar adsorption–desorption, pyridine-adsorbed infrared (Py-IR), 2,6-dimethylpyridine-adsorbed infrared (2,6-DMPy-IR) and NH3 temperature-programmed desorption (NH3-TPD). After loading Pt nanoparticles by incipient wetness impregnation, the morphological modification (benefiting from smaller nanobranches and introducing more external surface active sites) leads to enhanced heptane hydroisomerization activity of the dandelion-like Pt/SAPO-11 as great as 15.4% higher in comparison with a conventional Pt/SAPO-11 catalyst.

The hierarchically structured zeolite with high surface area and a large number of mesoporosities has attracted tremendous attention. Particularly, the morphology and structural tailoring of a diverse mesoporous zeolite with a single template is regarded as a crucial step toward the realization of an environmentally friendly synthesis. Herein, crystalline silicoaluminophosphate (SAPO-5) of the AFI framework type with a bimodal pore system was hydrothermally synthesized using di-n-butylamine (DBA) as a single template. The structural and catalytic properties of the hierarchical SAPO-5 were extensively characterized and compared to those of a conventional SAPO-5 using triethylamine (TEA) as a template. After loading Pt nanoparticles by incipient wetness impregnation, due to the promoting effect of hierarchical SAPO-5 in which the reactant and product were rapidly contacted with the acidity sites and metal sites, the 0.5 wt% Pt/SAPO-5-1.0DBA catalyst exhibits an enhanced hydroisomerization performance, with heptane conversion of 76.1% and iso-C7 yields of 48.4%, compared to a conventional 0.5 wt% Pt/SAPO-5-1.0TEA catalyst. The crystallization evolution under a series of hydrothermal times was also studied here. More importantly, this green, sustainable and economical strategy will extend the application of the synthesis of a silicoaluminophosphate-based zeolite.

During partial oxidation of methane (POM), the greatest challenge is to maintain the thermal stability of the catalyst at high temperatures. One of the most effective ways to improve thermal stability is to construct core-shell structure. Herein, using a microemulsion method, we synthesized a core-shell Ni/nanorod-CeO2@SiO2 catalyst, in which the Ni nanoparticles were supported on the CeO2 nanorods and encapsulated by SiO2 shells. Based on a series of characterizations, we found that the Ni particles are of nanosize (2.2 nm) and the thickness of the SiO2 shell is about 8 nm in the core-shell catalyst. Moreover, the Ni/nanorod-CeO2@SiO2 catalyst can perfectly maintain rod-like structures of the CeO2 support and enhance interaction between the metal Ni and CeO2, significantly reducing the sintering of metal Ni particles at high temperatures. Therefore, the as-prepared Ni/nanorod-CeO2@SiO2 catalyst shows high catalytic activity and good thermal stability during the POM reaction.

A novel tubular staggered-tooth transverse-flux permanent magnet linear synchronous machine is proposed. The machine is characterized by simple structure and low flux leakage. First, the structure and the operational principle are introduced. Second, the 3-D equivalent magnetic circuit model of the machine is built, and the analytical expression of the electromagnetic force is derived. Last, the force density and the force ripple are optimized with respect to three key dimensional ratios by the 3-D finite-element method. An optimized scheme with the high force density of $2.697 \times 10^{5}$ N/ $\text{m}^{3}$ and the low force ripple of 2.78% is achieved. In addition, the characteristics of the proposed machine are compared with other topologies of linear machines.

This paper presents the comparative study and optimal design of a transverse flux linear machine with different PM configurations, viz. surface-mounted and consequent-pole, in which the consequent-pole version is firstly proposed. Firstly, the effect of variation of the main design parameters on both topologies are studied. Then, the multi-objective optimization method based on genetic algorithm combined with response surface methodology (RSM) is adopted to realize the optimal design of these two topologies and Pareto front solutions will be obtained. Finally, the characteristics of these two topologies are analyzed and compared, with particular regard to the advantages and disadvantages of the consequent pole topology.

This paper presents a novel tubular flux-reversal transverse flux permanent magnet linear machine (FR-TFPMLM), in which both magnet and armature winding are located at the short primary side whereas the secondary side is composed of only magnetic steel. This configuration is typically used in long stroke applications to save magnet material. With different configurations of phase winding, the machine can have two topologies, viz. axial three-phase and circumferential three-phase. The structure and operational principle of both topologies are firstly introduced; And then both theoretical and numerical analyses are performed. The electromagnetic characteristics of both machines, with particular focus on thrust force and force ripple, are optimized. Finally, the performances of optimal schemes of these two topologies are summarized and compared.

Parallel finite difference schemes with high-order accuracy and unconditional stability for solving parabolic equations are presented. The schemes are based on domain decomposition method, i.e., interface values between subdomains are computed by the explicit scheme; interior values are computed by the implicit scheme. The numerical stability and error are derived in the H^1 norm in one dimensional case. Numerical results of both one and two dimensions examining the stability, accuracy, and parallelism of the procedure are also presented.

A new derivation of the conservative domain decomposition procedure for solving the parabolic equation is presented. In this procedure, fluxes at subdomain interfaces are calculated from the solution at the previous time level, then these fluxes serve as Neumann boundary data for implicit, block-centered discretization in the subdomain. The unconditional stability and the second-order accuracy of solution values as well as fluxes are proved. Numerical results examining the stability, accuracy, and parallelism of the procedure are also presented.

A free-piston energy converter (FPEC) integrated by a combustion engine and a linear electric machine is suitable for series HEV or other applications stand-alone generators. The transverse-flux machine (TFM) is considered advantageous for such application because of its high specific power and force density [1]. The finite element method (FEM) is widely used in the machine analysis, which is time-consuming. The equivalent magnetic circuit analysis is a time-effective method compared with FEM.

To solve the heat equation on parallel computers, a high-order parallel finite difference algorithm is presented. In this procedure, dividing the space domain into several sub-domains, we calculate the interface values between sub-domains by the classical explicit scheme, then solve the interior values of sub-domains by the forth-order compact scheme in parallel. The stability bound of the procedure is derived to be 1+63 times that of the classical explicit scheme. And the convergence rate is proved to be of order three. Numerical examples show that this method has much better accuracy than other known methods.

In this paper, a higher-order alternating group explicit scheme for the diffusion equation is developed. The scheme has fourth-order truncation error approximately. The numerical simulations show that the new scheme can provide more accurate solutions. A discussion on the numerical stability of the scheme is also included.

A finite difference domain decomposition algorithm (DDA) for solving the heat equation in parallel is presented. In this procedure, interface values between subdomains are calculated by the group explicit formula, whereas interior values of subdomains are determined by the classical implicit scheme. The stability and convergence for this DDA are proved. The stability bound of the procedure is derived to be eight times that of the classical explicit scheme. Though the truncation error at the interface is O(τ + h), L 2-error is proved to be O(τ + h 2). Numerical examples confirm the second-order convergence and indicate that the stability condition is sharp. A comparison of the numerical errors of this procedure with other known methods is also included.

The free-piston Stirling-engine linear-generator system can make efficient use of multiple energy resources, so it has great application potential in the fields of aeronautics and astronautics including space station, human lunar exploration, space vehicle, etc. This paper investigates the control strategy of the free-piston Stirling-engine permanent-magnet (PM) linear-generator system. The mathematical models of PM linear generator and free piston Stirling engine are established. The control strategies at starting and generating stages are proposed. The system simulation and experiment verification are also made.

A single-phase oscillating permanent-magnet (PM) alternator is proposed for free-piston stirling engines. According to its sinusoidal kinetic characteristic, the design principle of this machine is proposed. On this basis, the finite-element model is built. Since the no-load back EMF and no-load thrust are two key indexes for the single-phase oscillating PM machine, the influence of PM thickness on the no-load back EMF and no-load thrust is further investigated. Then an optimal scheme of single-phase oscillating PM machine is obtain. Because this machine has two working modes, the electromagnetic performance of two working modes is analyzed. In the generator mode, no-load and load back EMF, voltage harmonics distortion ratio, the voltage regulation ratio and kinetic characteristics are deeply analyzed. Then in the motor mode, the electromagnetic force versus current is investigated. That proves the electromagnetic thrust per current can reach 35.7 N/A.

In this paper, we present the Alternating Segment Explicit-Implicit scheme for the dispersive equation. The scheme is unconditionally stable and is capable of parallelism. The numerical simulations show that it has better accuracy than that of some existing schemes.

A new difference scheme with a higher-order discrete invariant for the KdV equation is proposed. Comparisons between the scheme and several other utilized schemes show that the new scheme is more effective in restraining nonlinear numerical instability.

Here the strategy of the group explicit method is applied to the numerical solution of a linear dispersive equation. An alternating group explicit method (AGE) for the equation with the periodic boundary condition is derived. The stability of the method is discussed. A comparison of the accuracy of this method with standard known methods is also included.

In this paper the parallel difference schemes with variable time steplengths for heat equations are studied. The absolute stability of the constructed schemes are proved. The numerical results of the alternating segment explicit-implicit (ASE-I) scheme and the alternating group explicit (AGE) scheme are presented. They show that the variable time steplength scheme provides good approximate solution that is more accurate than the solution of the equal time steplength scheme, and the former can be obtained with less computational effort than the latter.

In this paper, a difference scheme for the periodic initial-boundary problem of the coupled KdV Equation is given. The scheme keeps the first two conserved quantities which the differential equation possesses. The catch-ran iterative method is used to solve the difference equations. The numerical simulation exhibits the existence of two-soliton solutions.

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a simplified one phase model is established to investigate the performance of the machine in order to save the computation time. Then, the electromagnetic characteristics, including no-load flux linkage, electromotive force (EMF), inductance, detent force and thrust force, are simulated and analyzed in detail. After that, the theoretical analysis of the detent force, thrust force, and power factor are carried out. And the theoretical analysis results are validated with 3-D finite-element method (FEM). Finally, an improved mathematical model of the machine based on d-q rotating coordinate system is proposed, in which inductance harmonics and coupling between d- and q-axis inductance is considered. The results from the proposed mathematical model are in accordance with the results from 3-D FEM, which proves the validity and effectiveness of the proposed mathematical model. This provides a powerful foundation for the control of the machine.

© 2015 AIP Publishing LLC. This paper describes a tubular dual-stator flux-switching permanent-magnet (PM) linear generator for free-piston energy converter. The operating principle, topology, and design considerations of the machine are investigated. Combining the motion characteristic of free-piston Stirling engine, a tubular dual-stator PM linear generator is designed by finite element method. Some major structural parameters, such as the outer and inner radii of the mover, PM thickness, mover tooth width, tooth width of the outer and inner stators, etc., are optimized to improve the machine performances like thrust capability and power density. In comparison with conventional single-stator PM machines like moving-magnet linear machine and flux-switching linear machine, the proposed dual-stator flux-switching PM machine shows advantages in higher mass power density, higher volume power density, and lighter mover.

In this paper, the convergence and stability of the explicit scheme and the weakly implicit scheme for a class of generalized KdV equation are proved. The sharp stability condition is obtained.

Moving towards electrification of transport including electric vehicles (EV), more electric aircraft (MEA), and electric ships offers a crucial way in dealing with global carbon emissions and climate change. Electric motors are a key enabling technique in these applications, but their increased use is associated with requirements of extreme power/torque density, excellent fault-tolerance, high efficiency, and good manufacturability.\ud The main goal of this thesis is to study permanent magnet electric machine winding theory to determine the suitable electric machine winding topologies for different applications. Two separate vehicle transport applications are investigated, including an EV traction motor and a novel modular electromechanical actuator (EMA) for MEA.\ud The study of the EV traction motor involves the investigation of methods for reducing the significant stator MMF harmonics in fractional slot concentrated winding (FSCW) electric machines, and the development of novel FSCW topologies while keeping the benefits of easy manufacturing and the non-overlapping characteristic of concentrated windings. The novel FSCW topologies can be extended to multi-phase FSCW motors. A traction motor equipped with a novel 24 slots, 14 poles FSCW topology and interior PM (IPM) rotor is developed for evaluation. The performance under normal and fault conditions is fully explored and validated with simulation and experimental results, which demonstrates the applicability and strong potential of the proposed 24 slots, 14 poles IPM motor in fault-tolerant traction motor applications.\ud The second topic focuses on modular fault-tolerant EMAs for aircraft actuation systems which can meet a diverse range of requirements. The architecture and design considerations of the actuator system are firstly determined considering reliability, fault-tolerance, and weight. The modular EMA scheme consisting of a direct-drive rotary motor and mechanical screw is identified. A dual 3-phase 24 slots, 22 poles FSCW motor with a surface-mounted permanent magnet (SPM) rotor is developed and evaluated in terms of electromagnetics, thermal management, and fault-tolerance. Experimental results of the modular EMA motor prototypes agree well with predicted results. All this confirms the applicability and satisfactory implementation of the modular EMA motor for aircraft actuation system applications.

This paper studies the concerns such as architecture and reliability in the deployment of electromechanical actuator (EMA) in the actuation system for more electric aircraft (MEA). First, the reliability of the actuation system architecture such as control surface redundancy and actuator redundancy will be studied to determine an appropriate actuator architecture, with or without considering jamming. Then, the considerations for fault-tolerance and redundancy of the prime electric motor will be discussed in terms of reliability, weight, control complexity, and cost based on a direct-drive EMA designed for MEA. The comparison results demonstrate the configuration of two anti-jamming EMAs with dual three-phase drives connected in parallel can meet the requirements of the safety-critical actuation applications, promoting the deployment of fully electric actuation system on the MEA. Finally, a fault-tolerant motor with double 3-phase system designed for EMA will be presented, with performance under normal and fault conditions validated.