Search Results (13)

Fans are essential electronic components for heat dissipation in electronic systems, with fan bearings being critical parts that determine fan performance and lifespan. This paper investigates the corrosion, wear, power consumption, temperature, and vibration characteristics of a newly designed and manufactured powder metallurgy bearing with herringbone oil grooves for fans under high-humidity and high-temperature conditions. Corrosion experiments on iron–copper powder metallurgy bearings show that a higher environmental temperature and humidity result in greater corrosion current and reduced corrosion resistance. Bearings operated under high humidity (85% RH) and a high temperature (80 °C) for 0, 3, and 8 days, respectively, revealed that wear and corrosion occur simultaneously. The longer the operating time, the more significant the wear and corrosion. After 3 and 8 days, the lubricating oil flow in the oil grooves decreased by 9.8% and 51.5%, respectively. When bearings subjected to varying degrees of corrosion were tested under the same standard operating conditions, it was found that the bearings corroded for 3 and 8 days, resulting in a significant increase in the number of wear debris particles, higher RMS vibration values, and a power consumption increase of 6.9% and 7.8%, respectively. The percentage of iron elements on the surface gradually decreased, with the copper elements being the primary wear particles during the wear process. However, due to the increased clearance between the rotating shaft and the bearing caused by wear, the fan temperature slightly decreased with increased surface wear. Full article

Direct air-cooling systems use air instead of water as a cooling medium, so they are easily affected by meteorological and hydrological conditions. In this paper, considering the complex geographic conditions around the direct air-cooling units, Gambit is used to model the direct air-cooling system, including the complex mountainous terrain, and the performance simulation of the direct air-cooling system and the complex mountainous terrain near the power plant is realized by combining the CFD method with the MATLAB mathematical model of the power plant. Through the simulation, the operation of the ACC system under various meteorological conditions is obtained, and the influence of environmental factors and complex geographic conditions on the performance of the ACC system is investigated and further analyzed for the special case of the back-furnace wind. On this basis, a clustering analysis algorithm was used to obtain the results of turbine zoning in different wind directions and to analyze the physical field shifts of the units caused by geographic factors. Full article

This study explores the integration of wind power generation into urban infrastructure via a rooftop vertical-axis wind turbine. A rigorous experimental framework was established by installing a small-scale turbine on an urban building for performance assessment under controlled conditions. Simulated environmental conditions were created using a pedestal fan and blower to evaluate mechanical interactions between the components and electrical output efficiency of the turbine. Extensive numerical modeling was conducted to analyze turbine performance, by computational fluid dynamics using ANSYS FLUENT. The results reveal that the turbine operates efficiently even at low to moderate wind speeds (0.5–6 m/s), demonstrating its feasibility for urban deployment. Performance tests indicated that, as the shaft rotational speed increased from 55 rpm to 115 rpm, the output voltage, current and power varied nonlinearly in the ranges of 3–11.9 V, 20–130 mA and 0.05–2.7 W, respectively. Vibration measurement at specified turbine locations revealed nonlinear variation in displacement, velocity, acceleration and frequency without fixed patterns. Good agreement was observed between the experimental and numerical results. The numerical model yielded interesting profiles related to velocity and turbulence distributions, apart from torque, mechanical power and electrical voltage. Important conclusions were drawn from the entire work. Full article

With the rapid growth of air travel, reducing carbon emissions in aviation is imperative. Electric aircraft play a key role in achieving sustainable aviation, especially for large civil aircraft, where reducing emissions, improving the fuel efficiency, and enabling flexible power regulation are essential. This study proposes a dual-shaft, separated-exhaust fuel cell hybrid aircraft propulsion system (HAPS), using a solid oxide fuel cell (SOFC) to replace the conventional turbine-driven compressor. The independent speed control of the high- and low-pressure spools is realized via a power distribution system. A thermodynamic model is developed, and performance evaluations, including parametric, exergy, and sensitivity analyses, are conducted. At the design point, the system delivers 36.304 kN thrust, 16.775 g/(kN·s) specific fuel consumption, 15.931 MW SOFC power, and 54.759% SOFC efficiency. The exergy analysis highlights the optimization of components like the heat exchanger and fan to reduce energy losses. The sensitivity analysis reveals that the spool speeds and fuel utilization significantly impact the performance. The findings provide valuable insights into optimizing control strategies and offer a novel, efficient, and low-carbon power solution for aviation, supporting the industry’s transition towards sustainability. Full article

To study the influence of tip clearance on the working characteristics of high-altitude fans, this paper takes the MIX-140 high-altitude fan as the research object. Five different tip clearance (TC) models are selected. The CFD method is used to analyze the changes in the working characteristics of the fan under different flow rates and TCs in ground and high-altitude environments. The reliability of the numerical method is verified through a fan test bench. The results show that the tip leakage flow caused by the TC will continuously deteriorate the working characteristics of the fan. Under the rated flow rate in the ground environment, for every doubling of the blade’s TC, the static pressure difference will decrease by 5%, the efficiency will decrease by 2%, and the power will decrease by 3%. In a high-altitude environment, the flow rate corresponding to the maximum shaft power point of the fan will continuously increase with an increase in the tip clearance, which will bring about additional energy consumption. For high-altitude fans, the deformation caused by the high-speed rotation of the impeller needs to be taken into account. Undoubtedly, it is advantageous to choose the smallest possible tip clearance value. The results of the analysis and test methods in this paper will provide a basis for designing the tip clearance of high-altitude fans. Full article

In order to study the influence of various parts of the structure of a wet dust removal fan for mining (including the number of driving impeller blades, the airfoil of the driving impeller blades, the number of driven impeller blades, the rear guide vane, the swirl guide vane, and the length of the outlet section) on dust removal performance, a wet dust removal fan for mining was modeled according to different structural parameters. The internal flow field and dust removal of the fan were then numerically simulated using the Computational Fluid Dynamics (CFD) method. The results show that after the airflow passes through the swirl guide vane of the dust removal fan, there is an obvious swirl flow in the exit section of the dust removal fan. Under the action of centrifugal force, a large amount of dust is collected on the side wall of the exit section. With the increase in the number of driving impeller blades, the total pressure efficiency, static pressure efficiency, and dust removal efficiency of the dust removal fan decrease. When the driving impeller blade adopts the C-4 airfoil, the total pressure efficiency and static pressure efficiency of the dust removal fan are higher but the dust removal efficiency is lower than that of the same thickness circular plate airfoil. With the increase in the number of driven impeller blades, the power of the driving impeller shaft of the dust removal fan gradually increases; the total pressure and static pressure values first increase and then decrease; and the driven impeller speed, total pressure efficiency, static pressure efficiency, and dust removal efficiency gradually decrease. Adding the rear guide vane structure can improve the total pressure efficiency and static pressure efficiency of the dust removal fan but will reduce the dust removal efficiency of the dust removal fan. The increase in the swirl guide vane structure will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan but the dust removal efficiency will be significantly improved. The extension of the outlet section of the dust removal fan will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan, but the dust removal efficiency will increase. In this paper, by changing the structural parameters of the dust removal fan and establishing different models for numerical simulation and analysis, the influence law of the structural parameters of the dust removal fan on the dust removal performance is obtained, providing a way to improve the performance of the dust removal fan. Full article

An energy model that correlates fan airflow, head, speed, and system power input is essential to detect device faults and optimize control strategies in fan systems. Since the application of variable-frequency drives (VFDs) makes the motor-efficiency data published by manufacturers inapplicable for VFD–motor–fan systems, the fan efficiency and drive (belt–motor–VFD) efficiency must be identified for each individual system to obtain accurate energy models. The objectives of this paper are to identify an energy model of existing VFD–motor–fan systems using available experimental data and demonstrate its applications in loose belt fault detection and virtual airflow meter development for optimal control. First, an approach is developed to identify the fan head, fan efficiency, and drive-efficiency curves using available fan head, speed, and system power input as well as temporarily measured airflow rate without measuring shaft power. Then, the energy model is identified for an existing VFD–motor–fan system. Finally, the identified model is applied to detect the slipped belt faults and develop the virtual airflow meter. The experiment results reveal that the developed approach can effectively obtain the energy model of VFD–motor–fan systems and the model can be applied to effectively detect slipped belt faults and accurately calculate the fan airflow rate. Full article

Based on the composite shaft lining structure, the research on the electromagnetic and negative pressure coupling adsorption technology of wall–climbing robots is of great significance to improve the level of safety monitoring during the construction and service of coal mine shafts. On the basis of theoretical research and computational data, the numerical simulation and simulation experiments of the coupled adsorption system of a wall–climbing robot are conducted in this research. In the ANSA software environment, of experimental models and experimental environments of electromagnetic and negative pressure adsorption devices are constructed to investigate, parameters such as air flow and the law behavior of fan pressure under different system conditions, including negative pressure and varying fan speeds. The intensity distribution of the magnetic flux inside the electromagnetic circuit under different working conditions and the law of change in the direction of movement are explored. Furthermore, the power consumption and power increment of the electromagnetic and negative pressure adsorption system under the same adsorption force output are compared and analyzed. Based on the experimental results, a series of conclusions are verified; firstly the negative pressure of the system should be formed under certain basic specific fundamental conditions; secondly, the main velocity of the negative pressure adsorption system and the full pressure of the fan are determined by the internal and external pressure difference and the fan speed, respectively; lastly, the adsorption efficiency of electromagnetic adsorption is significantly higher than that of negative pressure adsorption. These research findings are expected to introduce a new technical means approach for the safety monitoring of vertical shafts and shafts in coal mines, thereby demonstrating the theoretical significance and practical value of the application and development of an underground multi–scenario robot automation system in coal mines. Full article

Amongst various sources of renewable energy, the kinetic energy of blowing wind has environmental friendliness and easy availability, together with other benefits. The wind energy is converted into usable electrical energy by means of a robust device termed a wind turbine. To carry out a performance study of such a device, a small-scale model vertical-axis wind turbine was installed at the laboratory and was run by artificial wind energy produced by a pedestal fan for low and medium speeds and a blower for higher speeds. The variation in critical parameters such as output power and voltage with different speeds was studied. The average output power and voltage were observed to increase with average shaft speed with linear and curvilinear patterns, respectively. The vibration produced at the bearing shaft resulting from the rotating components was analyzed as well. As observed, the peak values of critical vibration parameters such as displacement, velocity, acceleration, and frequency mostly varied curvilinearly with average shaft speeds. To study the applicability of the power generation, an electronically controlled automatic drip irrigation system was allowed to run by the wind turbine and important observations were made. Theoretical analyses (numerical and analytical) of the wind flow and power generation were also performed. Full article

This paper presents an optimization method for the civil aircraft environmental control system (ECS) mainly involving two airstreams: the ram airstream for cooling and the bleed airstream for supplying the cabin. The minimum total fuel energy consumption rate (FECR), defined as the weighted sum of the shaft power extraction and propulsive power loss, is obtained under the precondition of the constant outputs in the cooling capacity and outlet pressure. A modified genetic algorithm (GA) is proposed to acquire the optimal values of the heat transfer areas, temperature ratio of bleed air, mass flow rate of ram air, and pressure ratios of the turbine, compressor, and fan. The statistical results show that the multipoint crossover and continuity improvement implemented in the modified GA improve convergence and distribution performance. The probability of reaching a satisfactory result using modified GA is 62.4% higher than standard GA. Due to the decrease of inlet parameters of bleed air and the elimination of power input in the compressor, the FECR of the optimization case can be lowered by 11.0%. In general, the evaluation method considering energy quality together with the modified optimization technique is proved effective in energy-saving design for such energy systems such as ECS with multiple inputs and outputs. Full article

The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, or generators. Identification of causalities of device failure processes with near magnetic field is one of the suitable NDT methods improving sustainability of systems. The measurements presented in the article were performed with the VEMA 04 fluxgate vector magnetometer with the DC-250 Hz bandwidth and 2 nT sensitivity. Postprocessing of the results was performed in the means of standard methods of discrete Fourier Transform, spectrogram creation and Wavelet Transform. The article presents data gathered during the measurement of a pair of extraction fans with power of 140 kW each and maximum revolutions up to 740 rev/min controlled by frequency converters and a single semi-Kaplan water power plant with 400 kW peak power at 1005 rev/min maximum generator speed. The measurements were performed before and after repairs of one of the ventilators in the ventilation system at 60% and 100% of maximal output power. The rotating magnetic fields of the fan electromotor stator, fan rotor revolutions, rotor slip frequency and ball-bearing frequencies were identified in frequency spectrums in the distance of 700 mm from fan electromotor axis in both cases. During the measurements on the semi-Kaplan turbine, the changes in states of mechanical and electrical components of the machine were monitored in the magnetic fields with increase of the power in the range of 0–95%, before and after phasing to the electrical grid. Standard processing methods, Discrete Fourier Transform, spectrograms and Discrete Wavelet Transform were used. In the spectrograms of the measured magnetic fields, the 1st–4th harmonics of the turbine shaft, generator shaft and also their side frequencies were identified. Significant changes of magnetic fields in time were identified in the area of 60–95% power. With the help of the Wavelet, transform intervals were identified where it is desirable to operate the turbine. The analyses of magnetic fields measurements performed on the power plant were compared with vibro-diagnostic principles. Full article

Due to the fast electric control of the doubly-fed induction generator (DFIG) when experiencing power grid disturbance or turbulent wind, the flexible drive chain of the wind turbine (WT) generates long-term torsional vibration, which shortens the service life of the drive chain. The torsional vibration causes fatigue damage of the gearbox and affects power generation. In this paper, a two-channel active damping control measure is proposed. The strategy forms a new WT electromagnetic torque reference value through two channels: one is a proportion integration differentiation (PID) damping term with frequency difference, which is used to reduce torsional vibration caused by frequency difference between fan and shafting; the other adopts the torsional vibration angle (θ_s) as the feedback signal, and an additional damping term is formed by bandpass filter (BPF) and trap filter (BRF). The strategy can increase the electromagnetic torque and suppress the torsional vibration of the drive chain. Finally, modeling and simulation using MATLAB/Simulink show that the method can effectively suppress the torsional vibration of the drive chain without affecting power generation. Full article

The drudgery involved in dehulling breadfruit seed by traditional methods has been highlighted as one of the major problems hindering the realization of the full potential of breadfruit as a field to food material. This paper describes a development in an African breadfruit seed dehulling machine with increased throughput of about 70% above reported machines. The machine consists of a 20 mm diameter shaft, carrying a spiral wound around its circumference (feeder). The feeder provides the required rotational motion and turns a circular disk that rotates against a fixed disk. The two disks can be adjusted to maintain a pre-determined gap for dehulling. An inbuilt drying unit reduces the moisture content of the breadfruit for easy separation of the cotyledon from the endosperm immediately after the dehulling process. The sifting unit that separates the shell from the seed is achieved in this design with an electric fan. The machine is design to run at a speed of 250 rpm with an electric motor as the prime mover. The dehulling efficiency up to 86% and breakage of less than 1.3% was obtained at a clearance setting of 12.4 mm between disks. A sifting efficiency of 100% was achieved. Based on the design diameter and clearance between the dehulling disks, the machine throughput was 216 kg/h with an electric power requirement of 1.207 kW. Full article