Dual Halbach Array Research Articles

Multiple-degree-of-freedom damping characteristics evaluation of dual halbach array eddy current damper for turbopump in cryogenic environment

Liquid hydrogen turbopumps are used in large high-performance rockets. Stable high-speed rotation is required for rocket turbopumps. The damping mechanism of the pump must suppress vibration not only in the radial direction but also in the axial direction. However, conventional damping elements using oil or rubber cannot be used due to the cryogenic temperature of liquid hydrogen. Therefore, the application of eddy current dampers to liquid hydrogen turbopumps is focused on in this paper. Although various structures of eddy current dampers have been developed, the multi-degree-of-freedom damping characteristics of dual Halbach array type eddy current dampers for liquid hydrogen turbopumps have not yet been investigated. The variation of damping characteristics with temperature has also not yet been verified. In this paper, we propose a novel dual Halbach array type eddy current damper for liquid hydrogen turbopumps. The proposed damper can generate high damping force and can be operated maintenance-free at the cryogenic temperature. The analysis results show that the damping characteristics strongly depend on temperature and that the amplitude reduction effect is greater at low temperatures. It was also found that the proposed damper has a higher damping force density than conventional dampers.

Investigation of field free region formed by dual Halbach array for focused magnetic hyperthermia

Abstract One of the challenges with magnetic fluid hyperthermia (MFH) is the limited control of magnetic nanoparticle (MNP) oscillations. To overcome this problem new approaches such as localization of MNP oscillations are being explored. In this study, we investigated the manipulation of field free region form by dual Halbach array displacements. We used finite element method simulation to examine gradient patterns in the workspace. Then, we created an experiment platform and took point probe measurements. As a result of the research, it was found that the field free region form can be manipulated by parametric distance changes of dual Halbach array. According to the findings, the field free region can expand and its shape can change from a point-like form to an ellipse-like surface by varying the distance between the arrays. The mapping of dual Halbach array generated gradient patterns for focused MFH was investigated for the first time in this study.

Effect of the magnetic field produced by a Halbach array magnetizer on water UV absorption, removal of scale and change in calcium carbonate polymorphs

In this paper, the influence of magnetic fields on the ultraviolet (UV) absorption of water circulated within three different magnetic configurations (inside, outside, and dual Halbach array magnetizers) is presented. Permanent magnets were inserted in the designed magnetizer and magnetic flux densities were varied between 380 and 580 mT. The samples presented evident UV absorption under magnetic fields due to the change of polarization in water molecules. The effectiveness of the magnetic field to remove the scale was investigated by measuring the calcium ion concentration after magnetic treatment. The dual Halbach array configuration enhanced scale removal by 41.4% at a water flow rate of 380 ± 3 mL min-1. Different magnetic configurations were used to study the magnetic effect on calcite-aragonite CaCO3 polymorphs. The magnetic memory of the magnetizer was assessed using the percentage formation of aragonite crystals. Overall, magnetizers improved the aragonite formation. Dual Halbach array magnetizers yielded the highest aragonite percentage. Even after 24 h (memory effect) of storage, the presence of the magnetic effect indicated the superiority of the proposed method for scale removal. Thus, magnetic technology is an environmentally friendly, cost-effective, and simple treatment for scale removal.

Continuously Variable Valve Mechanism for Spark Ignition Engines Using Linear Actuator

In order to achieve higher performance in spark-ignition engines, it is required to control the intake and exhaust valves in stepless manner according to the engine speed. Our research group has been continuously studying the electromagnetic drive valve system using a linear actuator. In this report, we have designed a linear actuator with a dual Halbach array of permanent magnets in the stator to further increase the thrust of the linear actuator. The thrust characteristics of the proposed model were investigated using electromagnetic field analysis based on the finite element method. The analysis confirmed that the Halbach array concentrates the magnetic flux on the coil side, which generates Lorentz force.

Density-Based Measurement and Manipulation via Magnetic Levitation Enhanced by the Dual-Halbach Array

This work explores the design of a magnetic levitation configuration enhanced by a dual-Halbach array that enables density-based measurement and manipulation in a flexible, open-plan space. The two-parallel arranged Halbach arrays with concentrated magnetic flux allow the use of magnetic gradients parallel to the faces of the magnets to levitate samples in paramagnetic solutions. Compared to the commonly used MagLev device in which a sample container remains obscured by the magnets, the dual-Halbach array places no physical barriers to physical sampling while levitating in the magnetic field, gaining easy access to specific populations of samples in paramagnetic solutions. The strength of the linear gradient in density can be tuned by setting the gap between the two arrays, enabling accurate and convenient density measurement with tunable sensitivity. The access to manipulate specific populations of samples and ability to tune measurement sensitivity provide an operationally simple method for iterative separation and purification procedures. The design of the magnetic levitation configuration enhanced by the dual-Halbach array provides an accurate, inexpensive and easy-to-operate method that would be useful for analysis, quality control, purification in the fields of agriculture science, pharmaceutical industry and materials science.

Miniaturized springless hybrid nanogenerator for powering portable and wearable electronic devices from human-body-induced vibration

In this paper, a springless hybridized NG (nanogenerator) was newly designed to have a non-resonant behavior, in which the output power continuously increases with the input frequency and amplitude. To achieve a considerably higher output power generation at low-frequency vibrations and low amplitude, the proposed springless hybrid electromagnetic and triboelectric nanogenerator (SHEMG-TENG) utilizes a dual-Halbach array, which is fabricated with contact-separation and sliding-mode TENGs. The proposed SHEMG-TENG is fabricated and verified from a vibration exciter and human-body-induced vibration. Under the vibration exciter test (horizontal position), the fabricated SHEMG-TENG generated an output current and power of 2.04 mA and 5.41 mW, respectively, which corresponds to a volume power density of 395.4 W/m3 under a matching load resistance of 1.1 KΩ at an applied frequency and acceleration of 6 Hz and 1 g, respectively. For a number of basic human activities such as handshaking, walking, and slow running, the SHEMG-TENG was able to deliver output powers are 2.9 mW, 1.2 mW, and 1.7 mW (horizontal position), respectively, and 1.6 mW, 0.74 mW, and 2.3 mW (vertical position), respectively. This work presents an important step toward realizing SHEMG-TENG from human-body-induced vibration powered to enable wearable and portable smart electronic applications, and is expected to be widely accepted by the general public in their daily lifestyle.

Comparative Study of the Dual Layer Magnet Array in a Moving-Coil Tubular Linear PM Motor.

Conventional single-layer magnet arrays are widely utilized in electromagnetic linear machines. The objective of this paper is to analyze various types of novel dual-layer magnet arrays, either in similar or different patterns, to compare their flux field distribution and increase flux density in the machine. High flux density helps to improve the sensitivity of electromagnetic displacement sensors or actuator thrust. The design concept of magnet arrays are presented. The machine space is divided into several regions according to the magnetic properties. The corresponding magnetic field distribution is formulated based on magnetic vector potential and Laplace’s equations. Numerical computation is conducted to validate the developed magnetic field model. A systematic comparison of magnetic field of various magnet arrays is carried out. It shows that the dual Halbach magnet array can generate relatively high and constant flux density, which may help to produce strong signals. A research prototype and an experimental testbed are developed to validate the analytical model of dual Halbach array. This study provides a general framework for the design and analysis of dual-layer magnet arrays with various magnetization patterns. It can be extended to multiple-layer designs in radial direction.

A Hybrid Electromagnetic–Triboelectric Energy Harvester Using a Dual Halbach Magnet Array Powered by Human‐Body‐Induced Motion

AbstractA highly miniaturized hybridization of electromagnetic–triboelectric energy harvesters with different mechanisms in one harvester is proposed using a Halbach magnet array from human‐body‐induced motion, and it is theoretically and experimentally validated. In particular, the proposed dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a manner that produces maximum flux linkage. To obtain much higher power generation at low‐amplitude and low‐frequency vibrations, the proposed harvester is comprised of a Halbach magnet array, sandpaper‐based microstructure polydimethylsiloxane (PDMS), a triboelectric, and magnetic springs. A prototype of the hybrid energy harvester is fabricated and tested, both using a vibration exciter test, and by manual handshaking. Under vibration exciter test, the fabricated hybrid harvester prototype delivers a high output current and power of 4.5 mA and 12.51 mW, respectively, corresponding to a volume power density of 411 W m−3 under a loading resistance of 617 Ω at 6.5 Hz resonant frequency and 0.5g acceleration. The hybrid prototype is also capable of delivering output current and power of 3.55 mA and 7.35 mW, respectively, if driven by handshaking vibration. The fabricated hybridized harvester exhibits much higher power density than similar recently reported works.

Design and experiment of hybridized electromagnetic-triboelectric energy harvester using Halbach magnet array from handshaking vibration

We have proposed a new design of hybridized electromagnetic-triboelectric energy harvester using Halbach magnet array from handshaking vibration and validated it theoretically and experimentally. The Halbach array helps to enhance the magnetic flux density and reduce the overall volume as well as generate high power at low frequency. In particular, the proposed dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. To obtain much higher power generation in low amplitude and low frequency vibrations, the proposed harvester was comprised of a Halbach magnet array, sandpaper passed microstructure PDMS, TENG, and magnetic springs. A prototype of the hybridized energy harvester has been fabricated and tested both using a vibration exciter test and by manual handshaking. Under vibration exciter test, the fabricated prototype of hybridized harvester delivered a high output current and power of 2.9mA and 11.75mW, respectively, corresponding to a volume power density of 381W/m3 under a loading resistance of 1.39kΩ at 5Hz resonant frequency and 0.5g acceleration. It is also capable of delivering output current and power of 2.85mA and 8.1mW, respectively, by handshaking vibration. The fabricated hybridized harvester exhibited much higher power density than the recently reported similar works. Our proposed work takes a significant step toward hybrid energy harvesting from human-body-induced motions such as handshaking, walking, running and its potential applications in self powered portable electronics.

Design and experiment of human hand motion driven electromagnetic energy harvester using dual Halbach magnet array

We present a dual Halbach array electromagnetic energy harvester that generates significant power from hand shaking vibration. The magnetic-spring configuration is employed for generating sufficient power from the hand motion of irregular and low-frequency vibrations. However, significant power generation at low-frequency vibrations is challenging because the power flow decreases as the frequency decreases; moreover, designing a spring-mass system that is suitable for low-frequency-vibration energy harvesting is difficult. In this work, our proposed device overcomes both of these challenges by using a dual Halbach array and magnetic springs. During the experiment, vibration was applied in a horizontal direction to reduce the gravity effect on the Halbach-array structure. To achieve an increased power generation at low-amplitude and low-frequency vibrations, the magnetic structure of the dual Halbach array and the magnetic springs were optimized in terms of the operating frequency and the power density. A prototype was fabricated and tested both using a vibration exciter and by manual hand-shaking. The fabricated device showed resonant behavior during the vibration exciter test. For the vibration exciter test, the prototype device offers a maximum average power of 2.92 mW to a 62 Ω optimum load, at a 6 Hz resonance frequency and under a 0.5 g acceleration. The prototype device is capable of delivering a maximum average power of 2.27 mW from hand shaking. The fabricated device exhibited a normalized power density 0.46 mW cm−2g−2 which is very high compared to the current state-of-the-art devices, representing its ability in powering portable and wearable smart devices from extremely low frequency vibration.

A handy motion driven hybrid energy harvester: dual Halbach array based electromagnetic and triboelectric generators

In this work, we have proposed and experimentally validated of hybrid electromagnetic and triboelectric energy harvester using dual Halbach magnets array excited by human handy motion. Hybrid electromagnetic (EM) and triboelectric (TE) generator that can deliver an output performance much higher than that of the individual energy-harvesting unit due to the combination operation of EM and TE mechanisms under the same mechanical movements. A Halbach array concentrates the magnetic flux lines on one side of the array while suppressing the flux lines on the other side. Dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. When an external mechanical vibration is applied to the hybrid structure in the axial direction of the harvester, the suspended mass (two sided dual-Halbach-array frame) starts to oscillate within the magnetic springs and TEG part. Therefore, the TEG part, the Al film and microstructure PDMS film are collected into full contact with each other, generating triboelectric charges due to the various triboelectricities between them. A prototype of the hybrid harvester has been fabricated and tested. The EMG is capable of delivering maximum 11.5mW peak power at 32.5Ω matching load resistance and the TEG delivering 88μW peak power at 10MΩ load resistance.

A magnetic-spring-based, low-frequency-vibration energy harvester comprising a dual Halbach array

Energy harvesting that uses low-frequency vibrations is attractive due to the availability of such vibrations throughout the ambient environment. Significant power generation at low-frequency vibrations, however, is challenging because the power flow decreases as the frequency decreases; moreover, designing a spring-mass system that is suitable for low-frequency-vibration energy harvesting is difficult. In this work, our proposed device overcomes both of these challenges by using a dual Halbach array and magnetic springs. Each Halbach array concentrates the magnetic-flux lines on one side of the array while suppressing the flux lines on the other side; therefore, a dual Halbach array allows for an interaction between the concentrated magnetic-flux lines and the same coil so that the maximum flux linkage occurs. During the experiment, vibration was applied in a horizontal direction to reduce the gravity effect on the Halbach-array structure. To achieve an increased power generation at low-amplitude and low-frequency vibrations, the magnetic structure of the dual Halbach array and the magnetic springs were optimized in terms of the operating frequency and the power density; subsequently, a prototype was fabricated and tested. The prototype device offers a normalized power density of 133.45 μW cm−3 g−2 that is much higher than those of recently reported electromagnetic energy harvesters; furthermore, it is capable of delivering a maximum average power of 1093 μW to a 44 Ω optimum load, at an 11 Hz resonant frequency and under a 0.5 g acceleration.

A low frequency vibration energy harvester using dual Halbach array suspended in magnetic springs

An electromagnetic (EM) low frequency vibration energy harvester is newly developed based on dual Halbach array which is suspended in two magnetic springs. Each Halbach array concentrates the magnetic flux lines on one side of the array while suppressing the flux lines on the other side. Dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. With the goal of higher power generation in low amplitude and low frequency vibrations, the magnetic structures (both the dual Halbach array and the magnetic springs) were optimized in terms of operating frequency and power density. A prototype was fabricated and tested. It is capable of delivering maximum 1.09mW average power to 44Ω optimum load at 11Hz resonant frequency and 0.5g acceleration. The prototype device offers 33.4μWcm-3 average power density which is much higher than recently reported electromagnetic energy harvesters.

Armature Reaction Field and Inductance of Coreless Moving-Coil Tubular Linear Machine

Analysis of armature reaction field and inductance is extremely important for design and control implementation of electromagnetic machines. So far, most studies have focused on magnetic field generated by permanent-magnet (PM) poles, whereas less work has been done on armature reaction field. This paper proposes a novel analytical modeling method to predict the armature reaction field of a coreless PM tubular linear machine with dual Halbach array. Unlike conventional modeling approach, the proposed method formulates the armature reaction field for electromagnetic machines with finite length, so that the analytical modeling precision can be improved. In addition, winding inductance is also analytically formulated to facilitate dynamic motion control based on the reaction field solutions. Numerical result is subsequently obtained with finite-element method and employed to validate the derived analytical models. A research prototype with dual Halbach array and single phase input is developed. Experiments are conducted on the reaction field and inductance to further verify the obtained mathematical models.

A tubular linear machine with dual Halbach array

Purpose – Force output is extremely important for electromagnetic linear machines. The purpose of this study is to explore new permanent magnet (PM) array and winding patterns to increase the magnetic flux density and thus to improve the force output of electromagnetic tubular linear machines. Design/methodology/approach – Based on investigations on various PM patterns, a novel dual Halbach PM array is proposed in this paper to increase the radial component of flux density in three-dimensional machine space, which in turn can increase the force output of tubular linear machine significantly. The force outputs and force ripples for different winding patterns are formulated and analyzed, to select optimized structure parameters. Findings – The proposed dual Halbach array can increase the radial component of flux density and force output of tubular linear machines effectively. It also helps to decrease the axial component of flux density and thus to reduce the deformation and vibration of machines. By using analytical force models, the influence of winding patterns and structure parameters on the machine force output and force ripples can be analyzed. As a result, one set of optimized structure parameters are selected for the design of electromagnetic tubular linear machines. Originality/value – The proposed dual Halbach array and winding patterns are effective ways to improve the linear machine performance. It can also be implemented into rotary machines. The analyzing and design methods could be extended into the development of other electromagnetic machines.

MAGNETIC FIELD OF TUBULAR LINEAR MACHINES WITH DUAL HALBACH ARRAY

Permanent magnet (PM) array afiects ∞ux fleld distribu- tion of electromagnetic linear machines signiflcantly. A novel dual Halbach array is proposed in this paper to enhance ∞ux density in air gap, and thus to improve output performance of linear machines. Magnetic fleld in three-dimensional (3D) space of a tubular linear ma- chine with dual Halbach array is formulated based on Laplace's and Poisson's equations. Numerical result from flnite element method is employed to simulate and observe the ∞ux distribution in the machine. A research prototype and a testbed are developed, and experiments are conducted to validate the analytical models. The study is useful for analysis and design optimization of electromagnetic linear machines.