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In this experimental study mainly focused the thermal property such as thermal resistance and heat transfer analysis for the air gap variations provided in between two glasses on window for the domestic purposes. Easily available surrounding air considered as the experimental mater because of its arrangements. Thermal resistance of inside, outside and glasses (both glasses have same thermal conductivity such as 0.78 W/mK) all are maintained as constant throughout the investigation. But only air gap distance increased from 2 mm to 14 mm with gradual in-crease focused. The thermal conductivity of air considered as 0.026 W/mK. Thermal resistance and heat transfer impact with respect to the air gap between glasses were identify with the help of graphical representations.

In this article, the stator winding circulating current inside parallel branches (CCPB) of a doubly fed induction generator (DFIG) is comprehensively investigated. Different from other studies, this study not only focuses on the CCPB in radial static air-gap eccentricity (RSAGE) and radial dynamic air-gap eccentricity (RDAGE) but also takes the radial hybrid air-gap eccentricity (RHAGE) cases into account. Firstly, the detailed expressions of CCPB in normal and radial air-gap eccentricity (RAGE) are obtained. Then, the finite element analysis (FEA) and experimental studies are performed on a four-pole DFIG with a rated speed of 1470 rpm in order to verify the theoretical analysis. It is shown that the RAGE increases the amplitude of the CCPB and brings new frequency components to the CCPB. For RSAGE, the CCPB brings new frequency components, which are f1 (50) and fμ (540/640). For RDAGE, the newly generated frequency components are f1± fr (25/75), fu ± fr (515/565/615/665, and k = ±1). For RHAGE, the newly added frequency components in RSAGE and RDAGE are present at the same time. In addition, the more the RAGE degree is, the larger the amplitude of characteristic frequency components will be. The results obtained in this paper can be used as a supplementary criterion for diagnosing DFIG eccentric faults.

Investigations on static air-gap eccentricity (SAGE) faults about magnetic field variations, current/ voltage changes, and stator/ rotor vibrations have been widely carried out, while the mechanical properties of the end windings have been rarely studied, especially in 3D eccentricity cases. This article provides a detailed study on the stator end winding mechanics behavior in synchronous generators at typical rotor eccentricity running conditions. Such mechanics behavior includes not only the electromagnetic force (EF) properties, but also the end winding vibrations as well as the stress/strain/deformation responses due to the uneven EF excitation. The typical rotor eccentricity running conditions include: 1) radial static air-gap eccentricity (RSAGE), 2) axial static air-gap eccentricity (ASAGE), and 3) hybrid static air-gap eccentricity (HSAGE). The theoretical analysis, finite element analysis calculation and experimental verification are performed respectively, by taking a 5kVA synchronous generator as the research object in this paper. It is shown that in normal and SAGE cases, the end winding EF/vibration contains the DC component and even harmonics, especially the 2nd harmonic. RSAGE increases the end winding EF/vibration, whereas ASAGE increases the end winding EF/vibration at the extended end of the rotor while decreasing the EF/vibration on the retracted end. Under HSAGE, both RSAGE and ASAGE will affect the variation trend of end winding EF/vibration with the rule of single direction SAGE fault. The nose part and the joint to connect the end part and the linear sections are the most dangerous positions to afford the mechanics responses, and the occurrence of SAGE will make these parts more vulnerable.

Due to various factors such as manufacturing, assembly and operation, the motor air gap will be uneven in the circumferential direction, resulting in the air gap eccentricity having a longer air gap on one side and a shorter air gap on the other side, which affects the normal operation and service life of the motor. This paper analyzed and compared the applicability of linear and nonlinear calculation methods of unbalanced magnetic pull. Based on the method of finite element analysis, the unbalanced magnetic pull of motor rotor under static eccentricity, dynamic eccentricity and compound eccentricity faults were calculated, and the influence of eccentricity on unbalanced magnetic pull was compared, respectively. The results showed that when the motor has static eccentricity, the main components of unbalanced magnetic pull on the rotor are zero frequency and twice the electrical frequency. When the motor has dynamic eccentricity, the unbalanced magnetic tension component of the rotor is mainly frequency conversion. When the motor has two faults at the same time, the unbalanced magnetic pull has zero frequency, rotating frequency and double electric frequency components at the same time. With the increase in the relative eccentricity, the frequency components of the unbalanced magnetic pull under the three faults increase. An air gap eccentricity fault widely exists in motor equipment. When the unbalanced magnetic pull increases to a certain extent, the rotor will be pulled towards the stator, causing the occurrence of rub-impact phenomenon, and seriously threatening the safe operation of the system. In this paper, the numerical analysis method and finite meta-computing method were used for the first time to analyze and compare the unbalanced magnetic pull on the rotor of permanent magnet synchronous motor under three kinds of air gap eccentricity faults. The results showed that the characteristic frequency amplitude of the unbalanced magnetic pull calculated by the two methods is relatively close. Therefore, it is of great significance to carry out calculation and analysis of the unbalanced magnetic pull force under the air gap eccentric fault of the motor.

Finned tubular air gap membrane distillation is a new membrane distillation method, and its functional performance, characterization parameters, finned tube structures, and other studies have clear academic and practical application value. Therefore, the tubular air gap membrane distillation experiment modules composed of PTFE membrane and finned tubes were constructed in this work, and three representative air gap structures, including tapered finned tube, flat finned tube, and expanded finned tube, were designed. Membrane distillation experiments were carried out in the form of water cooling and air cooling, and the influences of air gap structures, temperature, concentration, and flow rate on the transmembrane flux were analyzed. The good water-treatment ability of the finned tubular air gap membrane distillation model and the applicability of air cooling for the finned tubular air gap membrane distillation structure were verified. The membrane distillation test results show that with the tapered finned tubular air gap structure, the finned tubular air gap membrane distillation has the best performance. The maximum transmembrane flux of the finned tubular air gap membrane distillation could reach 16.3 kg/m2/h. Strengthening the convection heat transfer between air and fin tube could increase the transmembrane flux and improve the efficiency coefficient. The efficiency coefficient (σ) could reach 0.19 under the condition of air cooling. Compared with the conventional air gap membrane distillation configuration, air cooling configuration for air gap membrane distillation is an effective way to simplify the system design and offers a potential way for the practical applications of membrane distillation on an industrial scale.

Both the physical properties of the fabric materials used in clothing and the effective design of the clothing, primarily in terms of the air gap thickness, restrict the transmission of the thermal energy from the heat source to the firefighter’s body. The air gap distribution over the body in real deployment conditions of firefighters will vary, and is likely to be different from the air gap distribution in standardised manikin tests in standing upright posture. In this study, we investigated differences in the distribution of air layers in firefighters' clothing in three postures reflecting realistic on-duty exposure conditions (crawling, hose-holding, and standing upright used in laboratory tests) using 3D body scanning technology. The body posture induced substantial changes in the air gap thickness on the upper body (chest and back) and lower body. These changes were reflected in both the thermal and evaporative resistance of the ensemble, and consequently, in their potential thermal performance in the field. Therefore, it is recommended to consider body postures during the evaluation of clothing protective performance. Secondly, the knowledge of local clothing properties in real-life exposure provides a true protection mapping and gives design inputs to improve the local protective properties of firefighters' clothing.

Purpose This paper aims to investigate and analyze the air-gap field modulation (AGFM) effect on torque contribution in a 6-slot/4-pole high-speed permanent magnet (HSPM) machine. To further illustrate the torque generation mechanism, the torque contribution is quantified using the Maxwell stress tensor (MST) method. Design/methodology/approach First, a simplified permanent magnet (PM) magnetomotive force model is established to identify the effective main-order working field harmonics. Then, the MST method is used to determine the average torque contributions of the effective main-order working field harmonics. Finally, the influences of various stator and rotor parameters on the AGFM effect are analyzed and optimized to enhance the torque density. Findings Apart from the fundamental harmonics, the AGFM harmonics contribute non-negligible average torque on the HSPM machine, and the optimized machine has higher torque density. Finally, a prototype of the 10 kW HSPM machine is manufactured and experimented with to validate the effectiveness of the theoretical analysis. Originality/value In this paper, the torque generation mechanism of the HSPM machine is investigated and analyzed. Meanwhile, the AGFM effect of the HSPM machine with different design parameters is analyzed and optimized to enhance the torque density.

The current transformer (CT)-based energy harvesting method has gained considerable attention for low-power devices. Accurate estimation of the B-H curve is essential to develop a high-performance CT, as it closely relates to the electromagnetic behavior of CT material. However, the existing estimation methods for the B-H curve face several drawbacks, which include process complexity and a high cost. This study presented an intuitive method to estimate the B-H curve based on the experimentally obtained resistance-voltage data. The performance of the CT core is obtained based on the estimated B-H curve, which exhibited an error of only 2.6% when compared to the experimental results for the most accurate case. Additionally, we analyzed split-core performance deterioration caused by the presence of an air gap. The air gap formation of the split core was closely related to the surface roughness, which significantly influenced core performance. The air gap range that minimizes the reduction in performance is predicted and validated through simulations and experiments. This research highlights a straightforward approach to obtaining the B-H curve of magnetic CT core material. We believe that this study provides the design guidelines needed to develop a high-performance CT core, including considerations for core geometry and the recommended air gap range.

The primary parametric resonance of a ferromagnetic rectangular thin plate with axial time-varying velocity in the air-gap field is researched. Through building the analytical model of air-gap field between the elastic plate and armature, the dynamic changes of air-gap field during resonance are determined. On account of electromagnetic boundary conditions, intraplate magnetic field distribution under the magnetization effect is obtained. Within the framework of magneto-electro-elastic theory and Hamilton principle, the motion governing equation of the axially moving ferromagnetic plate subjected to air-gap magnetizing force is finally deduced. For the simply supported constraint, applying the Galerkin method, the ordinary differential vibration equation of plate under parametric excitations is obtained by separating time–space variable. The multiscale method is applied to investigate the parametric vibration behavior of plate. Based on Lyapunov stability theory, the stability criterion of steady-state amplitude solutions is acquired. Through numerical methods, the correctness of analytical results is verified. The effects of armature and time-varying parameters on the static deflection, steady-state response amplitude, and the regional distribution of stable solutions are studied. The dynamic stability and bifurcation characteristics of the system are explored. Eventually, the results reveal that the static deflection caused by the air-gap magnetizing force makes the thin plate more rigid. The increase of armature and time-varying parameters causes the stable solutions to reduce and then grow by affecting the stiffness and excitation. At high magnetic potential amplitude, high velocity, and small tension, the system motion exhibits prominent chaotic characteristics.

The air-gap airflow significantly influences the performance of high-speed slotless permanent magnet synchronous motors (HSSPMSM), yet this critical factor is frequently overlooked during the design phase, resulting in performance deviations. This paper presents the design and multi-physical analysis of a 10 kW/40,000 rpm HSSPMSM, explicitly accounting for air-gap airflow effects. A comprehensive coupling model integrating electromagnetic, thermal, mechanical, and airflow fields is established to guide the motor design. Based on this analysis, the motor dimensions and parameters are determined, and a prototype is fabricated. Experimental validation demonstrates that the developed HSSPMSM successfully meets the design specifications. Considering air-gap airflow can obtain more accurate thermal design results with an accuracy improvement of 6.8% compared to not considering air-gap airflow. The close agreement between the simulated and measured performance confirms the effectiveness of the proposed design methodology that incorporates airflow effects.