Effect Of Air Gap Research Articles

EFFECTS OF ASYMMETRICAL STATOR STRUCTURE ON BLDC MOTOR PERFORMANCE FOR HOUSEHOLD APPLIANCES

Brushless direct current motors (BLDCM) have been frequently preferred in the industry, especially in home appliances, due to their advantages such as long life, high efficiency, low maintenance costs and ease of control. In addition to these advantages, the main disadvantages of these motors are known to be high torque ripple and vibration levels. In this study, alternative asymmetric designs are realized in the stator tooth structure of the BLDCM designed for home appliances, and comparative analyses of the effects of the non-uniform air gap caused by the asymmetric tooth structure on the motor performance are presented. Two different asymmetric structures, namely the model with clockwise asymmetric design (CW) and the model with counterclockwise asymmetric design (CCW) in the stator tooth structure, are determined in the stator design. With these alternative designs, improvements are made in terms of torque ripple and cogging torque when compared with the reference motor; notably, the CCW-2 model achieves the lowest ripple at 19.4% compared to 23.1% for the reference motor, and a 42% reduction in cogging torque. The design of the motor models is made in ANSYS EDT program as two dimensional (2D) and analyzed with the Finite Element Method (FEM). In the analysis results, air gap flux density, torque, torque ripple and cogging torque are examined, and the flux density and torque spectrum obtained by Fast Fourier Transform (FFT) are presented comparatively

Research on passive adaptive wall-climbing cleaning and inspection robot of marine cylindrical steel structure based on conical magnetic adsorption wheel

The marine growth cleaning and structural defect detection of steel structures of offshore underwater facilities are essential parts of the inspection and maintenance of offshore platforms. However, a majority part of underwater structures of offshore facilities, such as offshore wind turbines, Jacket platforms, Jack-up platforms, etc., are cylindrical structures. Compared with the planar structures, cylindrical structures have large curvature, and less supporting area, and therefore put forward higher requirements for the performance of the attached surface working robot. This paper proposes a wall-climbing cleaning robot that can move freely on the wall of cylindrical steel structures and passively adapt to cylindrical structures with various curvatures and diameters. According to the structural characteristics of the robot, a static failure model is established to analyze the different instability forms of the robot and the minimum critical magnetic adsorption force is determined. To ensure the minimum mass and the maximum magnetic adsorption force of the conical magnetic adsorption wheelsets, the effects of air gap and cone angle on the performance of the conical magnetic adsorption wheelsets were analyzed parametrically, and the optimal structural size was obtained. Finally, the mobility and capability of the robot on the surface of the different diameter cylindrical structures has been validated through prototype experiments.

Effects of Air Gaps on the Output Force Density in COMSOL Simulations of Biomimetic Artificial Muscles

Effects of Air Gaps on the Output Force Density in COMSOL Simulations of Biomimetic Artificial Muscles

Examination of the effect of air gaps on impact sound insulation performance of dry-type double floor system

The dry-type double floor system is a floor finishing structure widely installed for apartments and offices in Japan. However, after installing the double floor system, it is found that the impact sound insulation performance using a heavy-weight impact source is usually reduced due to the resonance of the air layer between the floor panels and the concrete slab. To reduce this adverse effect, small air gaps are set between the floor panels and the surrounding walls. In this paper, an experimental study is conducted firstly. A small specimen including particle board, support legs and air gaps is made to examine the effect of air gaps experimentally. Then, the air gaps are built as a Maxwell model considering that the air gaps act as the orifice of air spring. The theoretical analysis is conducted to explain the mechanism of impact sound insulation of the double floor system with or without air gaps. Finally, a parametric study is conducted to investigate the effect of air gaps with different dimensions on the impact sound insulation performance of the double floor system.

A study on maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolator.

This paper aims to study the maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolators (CMIs). The maglev force and stiffness of CMIs were analytically computed based on equivalent charge theory, and the transfer function of the system was conducted. The effects of magnet geometry parameters and air gap on the maglev force, stiffness, and vibration transmission characteristics of the CMI system were revealed through parametric analyses. With the increase in magnet length and width, the maximum value of maglev force increases, but the displacement range of near-zero stiffness, amplitude, and phase of the system gradually decrease. With the increase in magnet height, the displacement range of near-zero stiffness increases, while the variation in the amplitude and phase of the system has minimal impact. Meanwhile, in the Halbach array, the height variation of the magnet at different positions has different impacts on the magnetic force. As the air gap increases, the maximum value of maglev force decreases, but the amplitude and phase gradually increase, and the displacement range of near-zero stiffness first rises and then decreases. Finally, an experimental study was carried out to test the vibration attenuation characteristics of CMIs, in which sinusoidal excitation, hammer strike excitation, and random excitation were applied.

Effect of Viscosity and Air Gap within the Spinneret on the Morphology and Mechanical Properties of Hollow-Fiber Polymer Membranes for Separation Performance.

Hollow-fiber membranes for nanofiltration were prepared from the blending of Poly (ethylene glycol) (PEG) with Poly (vinyl chloride) (PVC) with different PEG molecular weights (400 and 4000 g/mol) and PVC via a dry/wet spinning process. In the spinning process, the effects of air gap, wind-up speed, dope extrusion rate, and bore extrusion rate were examined. In addition, the different lengths of the center tube, which acted as the inner-side fiber diameter during the preparation of hollow-fiber membranes, were studied. This research was investigated in order to observe the morphological, dielectric, and dynamic mechanical thermal properties to identify a suitable preparation of a hollow-fiber membrane for feasible applications. The morphology of the PVC-580 blended PEG-400 5 weight percent hollow-fiber membrane was seen to have a dense skin on both the inner and outer fiber surface, along with a suitable dope viscosity. Moreover, it offered finger-like substructures that could provide a high applicable feed-stream permeability and selectivity. Finger-like substructures were present on the near inner fiber surface at the controlled center-tube length of 0.3 cm, more so than at the center tube of 1 cm. This was because the solvent and non-solvent in the lumen tube exchanged more quickly than they did in the coagulant bath. The effect of the wind-up speed during the spinning process was significantly influenced by an affordable hollow fiber that can be indicated by the drawing ratio (λ). It was found that the drawing ratio of 3.3 showed a thickness thinner than 2.6 and 2.0, respectively. In summary, a controlled wind-up speed, an acceptable dope viscosity, and-most importantly-an agglomerated time resulted in membrane preparation.

Electric Motor Noise Variation Study Due to Air Gap Effect in Electric Vehicles

Motor whine is a crucial factor in the design of electric motors for electric vehicles (EVs). Predicting noise in a virtual environment is challenging due to the many possible variations during sample testing. The air gap between the stator and rotor in each sample is a significant contributor to radiated noise variation in the electric drive unit (DU). A baseline is first established for radiated noise prediction, assuming a nominal uniform airgap distribution, using the front electric DU in General Motors' Hummer EV. This study explains how the sensitivity of critical motor orders changes with static offset direction when the stiffness of DU is non-uniform and varies with radial direction. It also predicts the range of motor airborne noise variation due to offset orientation. Next, the effect of tilt direction on motor noise variation is studied at different torque conditions and motor speeds. Motor noise is found to be sensitive to tilt direction and angle as the DU stiffness changes axially. Additionally, rotor dynamic offset is investigated, which generates sideband orders in addition to motor pole pass orders. A comparison study is conducted to examine various sideband orders and their central frequency.

Effect of layering outerwear on innerwear and air gap between the two layers on thermal comfort properties of knitted fabrics

PurposeIn everyday life, people generally wear two layers of clothes (a knitted vest and a knitted t-shirt) during the summer. It is essential to understand which types of innerwear and outerwear maximize comfort. The primary objective of this research is to investigate the influence of layering outerwear on innerwear, as well as the air gap between two layers, on thermal comfort properties.Design/methodology/approachIn this study, a total of 12 combinations were created from four vest fabrics and three T-shirt fabrics. The thermal properties (thermal conductivity, thermal resistance, thermal absorptivity, thermal diffusion and peak heat flow) were evaluated for the individual inner and outer layers. Each inner layer was layered with an outer layer to observe the effect of layering on the thermal properties. An air gap of 2 mm was introduced between the inner and outer layers to study the effect of air gap on thermal properties.FindingsTencel fibre exhibits higher thermal conductivity and absorptivity than cotton and polyester. Upon layering an outer layer on an inner layer, the thermal conductivity and thermal absorptivity increase to a slight extent, thermal resistance and diffusion increase drastically and the peak heat flow reduces. With an air gap between the two layers, the thermal conductivity did not improve, the difference in thermal resistance among all the combinations reduced, the thermal absorptivity of the combination textiles was lower than that of the innerwear alone, the thermal diffusion increased and the peak heat flow diminished for all the combinations.Practical implicationsIn practice, this comprehensive thermal comfort analysis provides specific combinations of inner and outer articles of clothing that are most appropriate for enhancing comfort during the summer season.Originality/valueThough there are many studies on the effect of multilayer fabrics on thermal properties, no extensive research analyses the influence of innerwear and outerwear combinations on thermal comfort properties.

Airflow and heat transfer characteristics for different cargo pallet arrangements in a heat transfer enhanced refrigerated container

Improving the performance of a refrigerated container is crucial in effectively preserving thermal-sensitive cargo. The combined effect of vertical airflow resistance and airflow short-circuiting in air gaps play a vital role in cargo cooling. This study numerically investigates the effects of cargo vertical airflow resistance and air gaps between cargo pallets using two commonly used apple packaging boxes, each stacked in six different cargo pallet arrangements. A heat transfer enhanced refrigerated container design and a numerical model developed from the present authors’ previous studies are used. The numerical model uses the porous medium model to incorporate the refrigeration unit and cargo within the refrigerated container. Additionally, the numerical domain includes the T-bar floor in the refrigerated container. Initially, the airflow characteristics based on vertical airflow resistance and air gaps are discussed. Then, the corresponding effects on cargo cooling are addressed. Results show that the air gaps between the cargo pallets have positive and negative effects on cargo cooling. In cargos with lower vertical airflow resistance, an increase in air gaps leads to reduced cargo cooling and elevated temperature non-uniformity. Conversely, cargos with higher vertical airflow resistance experience increased cooling rates and reduced temperature non-uniformity with the increase in air gaps. However, avoiding airflow short-circuiting through the air gaps between the cargo pallets and improving the vertical airflow inside the cargo pallets can provide better cargo cooling, which outweighs the positive cooling effect of the air gap.

Effect of air gap on sound absorption in layered composite structures produced of sustainable materials

Numerous materials have been produced to isolate the noise that negatively impacts people’s health and productivity at work. Some of these materials are not preferred for usage because they are expensive, inefficient, or harmful to the environment. In this study, composite materials were produced with waste chicken feathers (CF) and polyvinyl acetate (PVAC) binder in different mixture ratios. After CF was washed and cleaned, it was shredded into 2–3 mm lengths with a chopper. Then CF was mixed with PVAC binder and thermal bonding was applied. As a result of the process, composites with a thickness of 10 mm and dimensions of 15 cm × 15 cm were formed. These composite plates are supported by sandwich constructions made of various varieties of polyester-based felt (NW), knitted fabric (KF), leather (L), spacer fabric (SF), and air gap (AG5, AG10, AG15) in thicknesses of 5, 10, and 15 mm. Impedance tubes with four microphones were used to evaluate the sound absorption coefficient and sound transmission loss values of these manufactured structures, and the resulting data were analyzed. According to this; The NW + CFC1 two-layer structure is 0.33 (500 Hz), but when a 15 mm thick air gap layer is added, it is seen that it increases to 0.85 (500 Hz). Other sandwich structures produced also show similar results. The best results were achieved with layered composite structures. Adding an air gap layer between the composite layers to increase sound absorption has improved results, especially at low frequencies. The air gap layer can significantly reduce production costs because it can be used instead of a material layer. The production of textile-based sound insulation structures from the waste material CF is also of great importance in terms of sustainability.

Development and characterization of the first proton minibeam system for single-gantry proton facility.

Minibeam represents a preclinical spatially fractionated radiotherapy modality with great translational potential. The advantage lies in its high therapeutic index (compared to GRID and LATTICE) and ability to treat at greater depth (compared to microbeam). Proton minibeam radiotherapy (pMBRT) is a synergy of proton and minibeam. While the single-gantry proton facility has gained popularity due to its affordability and compact design, it often has limited beam time available for research purposes. Conversely, given the current requirement of pMBRT on specific minibeam hardware collimators, necessitates a reproducible and fast setup to minimize pMBRT treatment time and streamline the switching time between pMBRT and conventional treatment for clinically translation. The contribution of this work is the development and characterization of the first pMBRT system tailored for single-gantry proton facility. The system allows for efficient and reproducible plug-and-play setup, achievable within minutes. The single room pMBRT system is constructed based on IBA ProteusONE proton machine. The end of nozzle is attached with beam modifying accessories though an accessory drawer. A small snout is attached to the accessory drawer and used to hold apertures and range shifters. The minibeam aperture consists of two components: a fitting ring and an aperture body. Three minibeam apertures were manufactured. The first-generation apertures underwent qualitatively analysis with film, and the second generation aperture underwent more comprehensive quantitative measurement. The reproducibility of the setup is accessed, and the film measurements are performed to characterize the pMBRT system in cross validation with Monte Carlo (MC) simulations. We presented initial results of large field pMBRT aperture and the film measurements indicates the effect of source-to-isocenter distance=930cm in Y proton scanning direction. Consistent with TOPAS MC simulation, the dose uniformity of pMBRT field<2cm is demonstrated to be better than 2%, rendering its suitability for pre-clinical studies. Subsequently, we developed the second generation of aperture with five slits and characterized the aperture with film dosimetry studies and compared the results to the benchmark MC. Comprehensive film measurements were also performed to evaluate the effect of divergence, air gap and gantry-angle dependency and repeatability and revealing a consistent performance within 5%. Furthermore, the 2D gamma analysis indicated a passing rate exceeding 99% using 3% dose difference and 0.2mm distance agreement criteria. We also establish the peak valley dose ratio and the depth dose profile measurements, and the results are within 10% from MC simulation. We have developed the first pMBRT system tailored for a single-gantry proton facility, which has demonstrated accuracy in benchmark with MC simulations, and allows for efficient plug-and-play setup, emphasizing efficiency.

Self-adaptive piezoelectric vibration absorber with semi-passive tunable resonant shunts

This paper proposes a novel self-adaptive strategy to control piezoelectric vibration absorbers (PVA) using a semi-passive resonant shunt with tunable inductance for vibration attenuation of harmonically excited structures. The tunable inductor is realized using ferrite cores and its inductance is controlled by means of the air gap effect between the cores using piezoelectric stack actuators. This device allows the control of the resonance frequency of the shunt circuit. The adaptive resonant shunt leverages the effect of antiresonance resulting from the electromechanical coupling of the structure with a resonant shunt with low electrical damping to attenuate the vibration of the harmonically excited structure. A machine learning control method based on a Gaussian process regression model is used to drive the tunable inductance based on minimizing the time-averaged RMS response of the structure. The experimental application of the proposed strategy is illustrated in an application to attenuate a single-mode of a simplified aircraft fuselage structure. A reduction of about 30% in the maximum vibration amplitude is observed by comparing the self-adaptive resonant circuit and a traditional resonant circuit designed based on the equal-peaks method.

Evaluation of wind-induced turbulence around offshore platforms in different wind speeds and directions, along with safety assessment of helicopter operation and helideck’s air-gap optimization

The demand for helicopter transportation has increased as offshore activity has expanded into more remote waters. In this situation, safe takeoffs, approaches, and landings on the platform's helidecks require understanding wind behavior. This study simulates the effect of a helideck air gap on wind turbulence around an offshore platform. The simulations are carried out using a validated computational fluid dynamics model based on the Reynolds-averaged Navier-Stokes k-equations. Five wind directions (with intervals of 45°), two wind speeds (5, 15, and 35 m/s, respectively, for winds with 7-days, 1-year, and 100-year return periods), and six air gap sizes (0–6 m) were assumed to calculate the induced turbulence. The Norsok C-004 standard, two speed-base, and one energy-based criterion were used to identify the turbulence conditions that allow helicopter operations. Wind-induced turbulence was significantly generated by the interaction of the wind with the crane and equipment placed on the highest level, limiting helicopter operation, particularly in most cases where the wind blows from the southwest. According to the findings, a minimum 4-m air gap is nedded to reduce turbulence caused by wind contact with equipment. Although no upward or downward flows (with ±2 m/s) have formed on the helipad, they have formed strongly around the helipad structure and in the direction of the helicopter approach.

Total scalp irradiation: A study comparing multiple types of bolus and VMAT optimization techniques.

To investigate bolus design and VMAT optimization settings for total scalp irradiation. Three silicone bolus designs (flat, hat, and custom) from .decimal were evaluated for adherence to five anthropomorphic head phantoms. Flat bolus was cut from a silicone sheet. Generic hat bolus resembles an elongated swim cap while custom bolus is manufactured by injecting silicone into a 3D printed mold. Bolus placement time was recorded. Air gaps between bolus and scalp were quantified on CT images. The dosimetric effect of air gaps on target coverage was evaluated in a treatment planning study where the scalp was planned to 60Gy in 30 fractions. A noncoplanar VMAT technique based on gEUD penalties was investigated that explored the full range of gEUD alpha values to determine which settings achieve sufficient target coverage while minimizing brain dose. ANOVA and the t-test were used to evaluate statistically significant differences (threshold=0.05). The flat bolus took 32±5.9min to construct and place, which was significantly longer (p<0.001) compared with 0.67±0.2min for the generic hat bolus or 0.53±0.10min for the custom bolus. The air gap volumes were 38±9.3cc, 32±14cc, and 17±7.0cc for the flat, hat, and custom boluses, respectively. While the air gap differences between the flat and custom boluses were significant (p=0.011), there were no significant dosimetric differences in PTV coverage at V57Gy or V60Gy. In the VMAT optimization study, a gEUD alpha of 2 was found to minimize the mean brain dose. Two challenging aspects of total scalp irradiation were investigated: bolus design and plan optimization. Results from this study show opportunities to shorten bolus fabrication time during simulation and create high quality treatment plans using a straightforward VMAT template with simple optimization settings.

Theoretical and experimental investigation of cylindrical air gap membrane distillation system and effect of the membrane support net on its performance.

In present study a cylindrical module is studied based on air gap membrane distillation configuration and studied for desalination purpose. A complete theoretical model was developed with consideration of design and operating parameters that enabled a Cylindrical Air Gap Membrane Distillation (CAGMD) module specific performance analysis. Theoretical model was verified with the literature as well as with the experimental results carried out on a lab scale CAGMD module. The effect of support nets which supports the membrane on the air gap side is also discussed on the performance. Support nets made up of four different thermal conductivities material- copper, aluminum, brass and polypropylene (PP) are considered for this study. The effect of feed temperature and flow rate, air gap width, cold flow rate, effect of thermal conductivities of support nets and height of the module was studied on the performance of CAGMD module. Permeate flux, Specific Thermal Energy Consumption (STEC) and the Gained output ratio (GOR) was selected as the performance indicators and the results for all the resulted parameters obtained from experimental and theoretical model falls in good agreement with only 6% deviation, that suggests that the proposed model is best suitable for predicting the behavior of any cylindrical AGMD module with great effectiveness. It is suggested that for better performance of the system feed flow rate, temperature and cold flow rate should be maintained at higher level. Maximum permeate flux achieved from the CAGMD module is 9.22kg/m2h.

Effects of air gap under clothing on heat transfer from fire environment to human skin: An experimental and numerical study for firefighter safety

Effects of air gap under clothing on heat transfer from fire environment to human skin: An experimental and numerical study for firefighter safety

Effects of air gap and compression on the dual performance of multilayer thermal protective clothing under low radiant heat

An air gap in thermal protective clothing (TPC) plays an important role in determining heat transfer, but it may also increase the amount of stored thermal energy that would discharge to the skin after exposure, especially when the TPC suffers compression. To investigate the effect of air gap and compression on the dual thermal protective performance (TPP), thermal hazardous performance (THP) and overall thermal protective performance (OTPP) of TPC, nine air gap configurations with different sizes and positions and five compression levels were designed in this study. Regression models were established to explore the relationships among air gap size, compression and THP for different air gap positions. The results demonstrate that increasing the air gap size without exceeding 12 mm not only significantly enhances the TPP by impeding heat transfer from the heat source to the fabric system during exposure but also decreases the THP by reducing heat discharge from the fabric system to the sensor even when compression is applied. Although an inner air gap contributes more to increasing the TPP during exposure than an outer air gap, it may also bring about severe stored energy discharge when compression is applied. It suggests that a larger air gap size should be divided into individually separate air gaps within different fabric layers to reduce the heat transfer during exposure as well as lower the stored thermal energy discharge after exposure.

Effects of Airgaps on Parasitic Capacitance of Magnetic Components

Effects of Airgaps on Parasitic Capacitance of Magnetic Components

АВТОМАТИЗИРОВАННЫЕ ИССЛЕДОВАНИЯ ДИЭЛЕКТРИЧЕСКИХ ПАРАМЕТРОВ ПОЛИМЕРНЫХ МАТЕРИАЛОВ В СОСТАВЕ ТЕХНОЛОГИЧЕСКОЙ СМЕСИ

The use of high-quality polymer film as packaging makes it possible to maintain marketable quality and reduce losses during storage of agricultural products even without additional processing. An overview of the existing control systems for the electrophysical parameters of polymeric materials is presented, the use of which serves as the basis for selecting the correct processing modes with the use of high-frequency electrothermal processing. When measuring the electrophysical characteristics of polymeric materials in multicomponent mixtures using standard testing methods, significant errors occur. In this regard, it is necessary to improve laboratory methods and diagnostic tools to solve research problems by automating the process of accounting for air gaps and studying their influence on the process of controlling the electrophysical parameters of the technological mixture. (Research purpose) The research purpose is developing an automated control system for the installation to determine the electrophysical parameters of multicomponent polymeric materials and studying the effect on the dielectric loss and dielectric permittivity of existing air gaps. (Materials and methods) Considered a number of methods to establish the methodology for conducting experimental studies on finding the electrophysical parameters of technological systems with air. (Results and discussion) We have developed an automated installation for determining the parameters of materials, created on the basis of domestic equipment of the VM-560 model. Methods of hardware and algorithmic implementation of the developed system of automated control of the process of investigation and control of the dielectric losses and permittivity of granular polymeric materials were presented. Experimental studies of the effect of air gaps and insulating material on the electrophysical properties of polymeric materials were performed. Refined electrophysical parameters of multicomponent polymers used in the production of films for packaging materials resistant to ultraviolet radiation have been obtained. (Conclusions) It was shown that the developed control system allowed to increase the accuracy of measurement by 12 percent.

Investigation of Effect of Air Gap between Surface and Bolus on Dose Distribution for 6 MV Photon Beam

In radiotherapy, tissue equivalent boluses are frequently used in the treatment of superficially located tumors. The air gap between the patient's skin and the bolus may cause dosimetric uncertainties. This study aims to dosimetrically investigate the effect of the air gap between the surface and the bolus on dose distribution. Computed tomography (CT) images of the phantom were obtained and transferred to the treatment planning system (TPS). In the TPS, a bolus was placed on the phantom surface and then air gaps were created between the bolus and the surface. The effect of the air gaps between the surface and the 5 mm thick bolus on the dose distribution was analyzed with the point doses obtained from the TPS. For the 6 MV X-ray, it was observed that the air gap negatively affected the surface doses calculated by TPS. Accordingly, an inverse correlation was found between air gap and surface dose. It is recommended that bolus use, especially in curved anatomical regions, should be applied before CT scanning as much as possible. When using bolus material in radiotherapy, it is recommended to be careful not to leave an air gap between the surface and the bolus.