Air Gap Width Research Articles

Design of Symmetric Magnetic Lenses with Optimum Operational Conditions

In the present paper, the geometrical and optical object properties of symmetrical magnetic lens are designed and analyzed using the electron optical design (EOD) program. The effect of the axial aperture diameter (D), the air gap between the poles (s), the thickness of the poles (t), the excitation parameter NI of the lens are all studied for the best optical properties like the object focal length fo, the spherical and chromatic aberrations coefficients (Cs and Cc respectively). It was found that the optical properties of the object significantly improved with a decrease in the axial aperture diameter and width of the air gap of this lens. Upon our study, it was found that the best properties are achieved when the air gap width (S2 mm), and the axial hole diameter (D=6 mm). The effect of the electrode face thickness on the magnetic properties of the proposed magnetic lens is studied, it was found that the best magnetic properties and the highest value of magnetic flux and the lowest value of the axial magnetic field strength bandwidth were at electrode face thickness equal to (3 and 4 mm).Therefore, the best magnetic lens in our design with the best optical properties was S=2mm, D=6mm and t=3mm.

Investigation on Key Parameters of NI HTS Field Coils for High Power Density Synchronous Motors

As global environment regulations are gradually strengthened, active research has been conducted on electric propulsion applications. High power density is one of the major research interests, as well as a machine's efficiency for a high-performance propulsion system. Among various electric propulsion technologies under development, a motor incorporating the no-insulation (NI) high-temperature superconducting (HTS) winding has the advantages of high current density and robustness to external disturbances, which are suitable for high specific power. However, still, there is little research on the motor with NI HTS coil. Therefore, as basic research, we investigated the potential application of the NI HTS motor, then derived required machine parameters and NI HTS coil designs in this paper. For that, first, basic parameters of the existing propulsion motors were investigated, then the target application and performance of the NI HTS motor were determined. Based on the target performance, conceptual designs of a motor with NI HTS coil were obtained by changing key design parameters including rated power, main dimensions, operating temperature, and width of air-gap. Calculated parameters were numerically compared, and expected design requirements and challenges were suggested.

Analytical Models for Fast and Accurate Calculation of Electromagnetic Performances of Segmented Permanent Magnet Synchronous Machines with Large Angular Gaps

In this paper original analytical models to determine the electromagnetic performances of segmented permanent magnet synchronous machines (with removed active parts in the stator or the rotor) are presented. These models are adapted to PMSM with large air gap width, large diameter, a high number of poles and large angular gaps. This method based on analytical approach is validated by comparizon with a 2D Finite Element calculation (Altair FluxTM 2D) for the specifications of a large diameter, low speed tidal high power current turbine generator. The presented method allows fast and accurate evaluation of the performances of this kind of particular machine and can be used in a systematic design process.

Experimental analysis of a novel helical air gap membrane distillation system

Abstract Membrane distillation presents one of the feasible solutions to fresh water problems. The present study aims to develop an innovative helical air gap membrane distillation (HAGMD) system and to analyze its behavior under different operating conditions. In this design the condenser is made up of a cylindrical copper tube with continuous helical fins over it, that increases the total available condensation area by almost 45% and enhances the overall heat transfer throughout the module. The presence of fins in the gap also reduces the total air gap width by almost 64% and therefore improves the flux production. A detailed experimental analysis is carried out for a better understanding of the underlying phenomenon. The effect of feed water temperature, feed flow rate, cold flow rate, coolant temperature and feed salinity on the performance of HAGMD is investigated experimentally. The analysis shows that the finned condenser results in very high flux. The maximum flux obtained from the system was 20 kg/m2 hr with feed of 5 g/liter salinity and a diving force temperature difference of 45 °C.

Analysis of the influence of inductor saturation on the level of electromagnetic interference of DC/DC-converters

The results of the study on the effect of the design parameters of a nonlinear inductor on the level of electromagnetic interference generated by DC/DC converters are presented. The paper proposes models designed for the LTspice XVII environment, which allow investigating conducted interference spectra, efficiency and output voltage ripple of the converter using a nonlinear inductor model. The simulation results showed that the level of conducted interference is affected by the volume and material of the inductor core, as well as the presence of an air gap in the core. The results of measurements of conducted interference spectra at different values of the cross-sectional area of the inductor core of the DC/DC converter are presented. With the nominal cross-sectional area of the core, calculated taking into account converter output power, the study of the relationship between the level of conducted interference and the width of air gap in the inductor core is carried out. In the course of studies, using the Chan model, the influence of inductor core material on the level of interference generated by the DC/DC converter is analyzed. Analysis of the influence of the width of the air gap in the inductor core on the level of conducted interference is carried out. It is shown that air gap width should be selected taking into account inductor core material. Simulation results for a number of commonly used materials made it possible to determine the most effective one in terms of generated interference.The results obtained in the analysis of switching voltage converter operation, taking into account inductor nonlinearity, allow us to formulate recommendations to reduce the level of generated conducted interference by 4.5 to 6 dB due to the correct choice of inductor material and design parameters

Analysis of Effective Parameters on Magnetizer Using Finite Element Method

Permanent magnets due to their high energy production are widely used in a variety of electromagnetic devices. Such devices can be found in marine, aerospace, and robotic applications which require the minimization of weight and volume of the electro- magnetic devices. The coercively of some permanent magnets are high so the magnetizer is used for high magnetic field generation. Different parameters such as core shape, core material, turn number, cross section of the air gap, magnet type, etc have been known to affect the magnetizer operation. The amplitude and waveform of fixture current is obtained from PSPICE simulations and also experimental measurement. A 2D finite element analysis is developed to simulate magnetic fields and mechanical forces. The main parameters affecting optimal design of the magnetizer are discussed. Simulation results show that the core structure, air gap width, and turn numbers are the most important parameters when designing such a device.

Fast rise breakdown in dielectric filled air gap for surge protection

Electric discharge across an air gap can be self-healing, providing a unique capability for repetitive, fast, high-voltage/current switching applications through arc conduction. Furthermore, incorporating dielectric granules in the air gap stimulates gas ionization, which lowers the breakdown voltage and narrows breakdown voltage distribution, thereby enabling engineered surge protection from multiple lightning strikes on aerospace vehicles and sensitive solid-state electronics in critical systems. This study investigates the effect of the permittivity of dielectric granules, gap filling, surface roughness, and metal work function on fast-rising, high-voltage breakdowns. In addition to the air gap width, these factors play important roles in gas ionization, field concentration, and initiation of electrical discharge and arcing. Therefore, they could potentially be used to control and narrow operational breakdown voltages for practical applications. Additionally, a modified Langevin–Debye model is developed to correlate the breakdown voltage and the permittivity of the dielectric filler. These investigations identify and highlight key underpinning mechanisms governing the gas discharge behavior across a dielectric filled air gap during voltage surge events.

Model approach for electromagnetically excited mechanical vibrations in direct-drive wind turbines

In this paper a multi-physical modelling approach for calculating parasitic magnetic force excitations in wind turbine generators is presented. These parasitic excitations are dependent on the magnetic field distribution in the air gap and the air gap geometric shape, which is dependent on the external loads of the wind turbine. With this methodology mechanical multibody simulation is coupled with electromagnetic field calculation by means of finite-element calculation. First the general methodology and the calculation of the air gap width distribution is presented and subsequently the electromagnetic field and force calculation is explained.

PROBATION OF THE IMPROVED UNINTERRUPTED PASTEURIZATION SET “TUBE IN TUBE”

There have been conducted probation studies of an improved uninterrupted pasteurization set “tube in tube” that allowed to provide modern market needs of consumers in getting high-quality food products that must undergo pasteurization stages at technological production. Heat delivery by FFREHRT is used in the set for providing heat flow distribution evenness. There has been established the optimal working space of processed raw materials by studying a temperature drop in the middle of the raw material flow and at the apparatus surface. At the width of the linear ring size of the working environment as 9.5 mm and the flow speed as 0.4 m/s there is provided the least temperature drop value as 0.7 °С. At decreasing the air gap width, the temperature drop value increases and at 5.5 mm is equal to 2 °С that favors the effectiveness decrease of the pasteurization process. According to results of comparative indices of the main composition and obtained quality of pasteurized cow milk, just the experimental sample, obtained at the probation of the offered apparatus is advantageous, comparing with a traditional. It is explained by the decrease of milk temperature processing at the expanse of double pasteurization by FFREHRT, comparing with the traditional pasteurization method. The conducted studies prove the effectiveness of constructive-technological solutions for realization of pasteurization in the set “tube in tube”: the use of two-side heating by FFREHRT that due to its technical parameters is able to take any geometric form of the working chamber and at that provides the necessary evenness of heat flow distribution. We must also note the improvement of exploitation parameters of the offered set, namely facilitation of the automatic control of temperature regulation and the absence of the steam coat and correspondent armature as in the traditional apparatus that decreases metal consumption essentially. The obtained results are urgent for using the presented invention for pasteurization of different food raw materials (milk, juice, low-alcohol beverages and so on). The use of the improved pasteurizer allows to decrease resource consumption and to improve the quality of obtained products

Irreversible demagnetization mechanism of permanent magnets during electromagnetic buffering

The permanent magnets will be irreversibly demagnetized under high temperature and high velocity during the electromagnetic buffering. In this study, the magnetic field induced by eddy currents and the self-demagnetizing field of permanent magnet are taken into consideration together for demagnetization analyse. The magnetic Reynolds number is used to express the eddy currents demagnetization. The correction coefficient being expressed as the index of the air-gap width, the inner cylinder thickness, iron pole axial length and the permanent magnet demagnetization coefficient is introduced by magnetic path analysis to represent the self-demagnetization effect and the demagnetization extent. The electromagnetic buffer (EMB) prototype is tested under intensive impact loads of different strengths at room temperature. The accuracy of the nonlinear irreversible demagnetization finite element model is verified by demagnetization on damping force, velocity and displacement. Finally, high-velocity demagnetization and high-temperature demagnetization are analysed in order to obtain the distribution law of irreversible demagnetization.

High-Power Magnetoelectric Voltage Tunable Inductors

Magnetoelectric voltage tunable inductors (VTIs) offer a new paradigm for power electronics circuit design. Here, air-gapped VTIs are demonstrated exhibiting a large inductance tunability of 220% with applied fields under 20 kVcm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and operational stability up to 5 MHz that covers the full frequency range of the state-of-the-art power electronics. The design of air-gapped VTI comprises of two C-shaped ferrite cores, one permeability-variable magnetic flux valve (MFV) in between C-shaped cores, and slotted air gap between cores and MFV. The tunability of VTIs is achieved through the electric field modulation of permeability in the MFV based on the magnetoelectric effect. There is a tradeoff between the tunability and saturation current. The introduction of air gap significantly reduces the tunability but provides methodology toward increasing the saturation current and power handling capability due to the increased reluctance. The inductance and tunability reduces by 50% with increase in the air-gap width from 0.07 mm to infinity (condition with no C-shaped cores). Phase field simulations demonstrate that the air gap affects the magnetization, permeability, and tunability of VTIs by tailoring the demagnetization field that further influences the magnetic domain rotation process. VTIs with increased frequency range and saturation current will strengthen the continued development of tunable power electronics.

A CFD based approach for determining the optimum inclination angle of a roof-top solar chimney for building ventilation

A CFD based procedure is described to identify the optimum inclination angle of a small-scale roof-top solar chimney for maximum ventilation performance. The absorber wall of the chimney under consideration is 500-mm long and the air gap width is 40 mm. Firstly, CFD simulations are performed on a two-dimensional solar chimney model with inclination angles varying from 30° to 90° relative to the horizontal plane under different heat fluxes. Subsequently, a mathematical procedure using the CFD data to estimate the ventilation performance of the solar chimney at different inclination angles under real climate conditions is described. The procedure accounts for the effect of the inclination angle on receivable solar irradiance and is applied to three Australian cities, corresponding to three different latitudes. It is found that the optimum inclination angle varies from 45° to 60°, depending on the latitude and season of operation.

Terahertz Bragg Resonator Based on a Mechanical Assembly of Metal Grating and Metal Waveguide

Terahertz (THz) waveguide Bragg grating is experimentally demonstrated on the basis of a mechanical assembly that includes a metal-grating sheet and a metal parallel-plate waveguide (PPWG). Bragg frequency waves, which are also called phase-matching waves, are efficiently coupled from the free space on the basis of the designed parameters of the air gap width, the metal grating thickness, and the PPWG taper angle. These optimal parameters are critical to reflect the Bragg frequency waves with a transversely resonant field across the metal grating. For other THz waves that are not phase matching to the meal grating vector, transverse resonance simultaneously occurs. However, these waves propagate forward as waveguide modes. PPWG-assembled metal grating thus performs highly distinct Bragg frequencies in the waveguide transmittance when the noisy resonance field, not following Bragg law, is exactly constrained by the waveguide scheme. Given that all components of the waveguide Bragg grating are made of metal without dielectric perturbation, a series of strong Bragg resonant modes in a wide bandwidth and a hollow-core chamber is potentially facilitated for THz gas sensors.

A numerical investigation of combined solar chimney and water wall for building ventilation and thermal comfort

Abstracts This paper reports a numerical investigation of combined solar chimney and water wall for building ventilation and thermal comfort. The effects of major design parameters including glass panel thickness, air gap width and water column thickness are investigated with CFD simulations. The results show that the combined system is capable of providing around-the-clock ventilation with a daily average of 4.1 air changes per hour while maintaining the daily average of the room temperature 4.8 °C above that of the ambient. The overall performance of the combined system may be further improved by reducing the glass panel thickness or applying solar control tinting to the water wall assembly, and as much as 7.3% and 5.2% improvements in the ventilation rate and the averaged room temperature respectively can be achieved. Increasing the water column thickness by 0.1 m leads to 4.9% or more improvement in the ventilation rate but will cause the averaged room temperature to drop by 6.4% when the water column thickness is increased to 0.3 m. Increasing the air gap width from 0.1 m to 0.2 m leads to 13.9% improvement in the ventilation rate without affecting the averaged room temperature much. However, further increasing the air gap width only has a minor impact on the ventilation rate.

Effect of Air Gap Width on the Evaluation of the Trombe Wall Efficiency

This study examines the selection of the best air gap to a model solar passive solar system chosen for heating in a cold climate based on instantaneous efficiency. The experiments have been performed on a passive solar system, which has been constructed from insulation sandwich panels in all sides except the south facade, which has been built from insulation sandwich panels on all sides except the south facade, where Trombe wall has been built in it, which is constructed from reinforced concrete and their exterior surface has been painted with dark black color, and covered with a single transparent glass layer. Five sets of experiments have been performed on the test system by changing the width of the air gap from 30 to 10 cm under the weather conditions in January 2017 in the city of Kirkuk (Iraq). The experimental results have showed that the 33 to 36% of the absorbs energy by Trombe wall has been converted to instantaneous energy provided to the heating space during the day. In addition, the results of the energy analysis of experimental equations have been produced to assess the efficiency of the system; they show that the 15 cm air gap has a better case when applying the same parameters, this result is consistent with an experimental study conducted by R. L. Casperson and C. J. Hocever, 1979.

Reflowable optical connector with glass-ceramic ferrule for advanced pluggable transceiver packaging

Abstract We describe a new physical-contact optical fiber connector/receptacle that can withstand a solder-reflow process with a maximum temperature of 260 °C for advanced pluggable transceiver packaging such as the co-packaging of photonic and electronic chips using the reflow process. We experimentally clarify the problems that occur in the conventional simplex optical connector through the reflow process while discussing the glass-transition behavior of the adhesive used in the connector. We then present an improved receptacle structure with glass-based ferrules whose coefficients of thermal expansion are closer to that of the fiber compared to the conventional zirconia ferrule. We demonstrate through testing that our proposed receptacle results in a dramatic decrease of permanent fiber withdrawals after the reflow process. The proposed connector, which is composed of a glass-ceramic ferrule, a polyimide tube, and a mechanical clip, achieved physical-contact connection and maintained satisfactory connection and return losses of below 0.3 dB and over 45 dB, respectively, even after six reflow processes. We examined the withdrawal behaviors for both the zirconia and the glass-ceramic ferrules during reflow based on the online measurement of connection and return losses, and observed the multiple reflections caused by the change in the air-gap width between the mated connectors. We also confirmed that the developed simplex optical connectors based on the glass-ceramic ferrule yielded sufficient environmental durability even after multiple reflow processes.

Observation of self-organized honeycomb patterns by fast photography in a liquid-anode discharge

In a rod-water geometry, self-organized patterns are formed on the water surface of an atmospheric glow discharge excited by a square-wave voltage, which include a disk with an encircling ring and concentric triple rings with varying air gap widths. The diameter of these patterns slightly increases with the increasing gap width. Although a square-wave voltage is used, waveforms of voltage and current indicate that the discharge belongs to a periodical liquid-anode discharge. By fast photography, spatial and temporal evolutions of these self-organized patterns indicate that honeycomb patterns are prone to be generated with a wider gap. Moreover, these honeycomb patterns finally lead to the formation of the concentric triple rings and the disk with an encircling ring with wider gaps. Within the scope of our knowledge, this is the first observation of honeycomb patterns in a liquid-anode discharge.

The Impact of Air Well Geometry in a Malaysian Single Storey Terraced House

In Malaysia, terraced housing hardly provides thermal comfort to the occupants. More often than not, mechanical cooling, which is an energy consuming component, contributes to outdoor heat dissipation that leads to an urban heat island effect. Alternatively, encouraging natural ventilation can eliminate heat from the indoor environment. Unfortunately, with static outdoor air conditioning and lack of windows in terraced houses, the conventional ventilation technique does not work well, even for houses with an air well. Hence, this research investigated ways to maximize natural ventilation in terraced housing by exploring the air well configurations. By adopting an existing single storey terraced house with an air well, located in Kuching, Sarawak, the existing indoor environmental conditions and thermal performance were investigated and monitored using scientific equipment, namely HOBO U12 air temperature and air humidity, the HOBO U12 anemometer and the Delta Ohm HD32.3 Wet Bulb Globe Temperature meter. For this parametric study, the DesignBuilder software was utilized. The field study illustrated that there is a need to improve indoor thermal comfort. Thus, the study further proposes improvement strategies to the existing case study house. The proposition was to turn the existing air well into a solar chimney taking into account advantages of constant and available solar radiation for stack ventilation. The results suggest that the enhanced air well was able to improve the indoor room air velocity and reduce air temperature. The enhanced air well with 3.5 m height, 1.0 m air gap width, 2.0 m length was able to induce higher air velocity. During the highest air temperature hour, the indoor air velocity in existing test room increased from 0.02 m/s in the existing condition to 0.29 m/s in the hottest day with 2.06 °C air temperature reduction. The findings revealed that the proposed air well could enhance the thermal and ventilation performance under the Malaysia tropical climate.

Prediction of Indoor Air Circulation of Residential Room with Adaptation of Solar Chimney Using Numerical Technique

With the exponential increase in consumption of electrical power during the summer season by household, there is a great need for households to withhold sustainability. To maintain the temperature of the household a passive heating and cooling system is used i.e. Solar Chimney. Ventilation, through a natural convection process, is gaining a lot of attention to be an alternative technique for mechanical air conditioning ventilation because of its reduced power usage when compared to the external cooling devices used in residential buildings of hot regions. The present study, involve solar chimney of horizontal and vertical designs in comparison with different width and height. The following paper studies the effect of a solar chimney on the indoor thermal behavior using Numerical Technique for a prototype of a residential room. The performance on the ventilation velocity and air temperature operation inside the room with varying air gap width is studied based on multiple numerical analysis solutions. The present study deals with two different architectures of a two dimensional model and results have shown that the ventilation velocity has increased to 0.017626444 kg/s and operative air temperature has been decreased by 7.26ºC for the vertical model while the horizontal model has shown a mass flow rate of 0.018027636 kg/s and a temperature decrease of 9.15ºC. The most efficient chimney was found to be model 7 which is horizontal solar chimney 3 with an air gap width of 0.05625m and a height of 0.3175 m, when compared to the other models from model number one to six.

Optimising the FDM additive manufacturing process to achieve maximum tensile strength: a state-of-the-art review

PurposeAdditive manufacturing or “3D printing” is a rapidly expanding sector and is moving from a prototyping service to a manufacturing service in its own right. With a significant increase in sales, fused deposition modelling (FDM) printers are now the most prevalent 3D printer on the market. The increase in commercial manufacturing necessitates an improved understanding of how to optimise the FDM printing process for various product mechanical properties. This paper aims to identify optimum print parameters for the FDM process to achieve maximum tensile strength through a review of recent studies in this field.Design/methodology/approachThe effect of the governing printing parameters on the tensile strength of printed samples will be considered, including material selection, print orientation, raster angle, air gap and layer height.FindingsThe key findings include material recommendations, such as the use of emerging print materials like polyether-ether-ketone (PEEK), to produce samples with tensile strength over 200 per cent that of conventional materials such as acrylonitrile butadiene styrene (ABS). Amongst other parameters, it is shown that printing in the “upright” orientation should be avoided (samples can be up to 50 per cent weaker in this orientation) and air gap and raster width should be concurrently optimised to ensure good “inter-raster” bonding. The optimal choice of raster angle depends on print material; in ABS for example, selecting a 0° raster angle over a 90° angle can increase tensile strength by up to 100 per cent.Originality/valueThe paper conclusions provide researchers and practitioners with an up-to-date, single point reference, highlighting a series of robust recommendations to optimise the tensile strength of FDM-printed samples. Improving the mechanical performance of FDM-printed samples will support the continued growth of this technology as a viable production technique.