Fan Operation Research Articles

Sign Recognition and Voice Conversion Device for Dumb

This project proposes a comprehensive hardware setup for home automation and environmental monitoring. The system includes components such as a Bluetooth module for remote control, a voice module (APR9600) for audio feedback, an LCD for display purposes, relay modules for controlling electrical devices, bulbs with holders for lighting, a CPU fan for temperature regulation, speakers for audio output, and a 5V power supply for operation. The core functionality of the system revolves around the integration of flux sensors for environmental monitoring. When flux sensors detect specific conditions, predefined audio signals are played through the voice module. These conditions correspond to six distinct signs, facilitating real-time alerts and notifications. Moreover, the system offers remote control capabilities through Bluetooth connectivity, enabling users to manage lighting and fan operations conveniently. Additionally, temperature monitoring is implemented using a DHT11 sensor, triggering the activation of the CPU fan when temperature thresholds are exceeded. Furthermore, an LCD display enhances user interaction by providing visual feedback and status updates. The project utilizes Arduino UNO as the central processing unit and incorporates 12V 1A adapters for powering specific components. Connectors and power cables are utilized for seamless integration and electrical connectivity. Overall, this project presents an integrated solution for home automation and environmental monitoring, offering flexibility, convenience, and enhanced user experience.

Improvement and optimization of coal dust concentration detection technology: Based on the 3σ criterion and the kalman filtering composite algorithm

Due to the inherent time delay in dust concentration data transmission, dust reduction equipment is unable to respond according to the current moment's dust concentration. Hence, the focus of mine dust concentration detection technology extends beyond the current dust concentration to accurately predicting the next moment's dust concentration, allowing a response window for dust reduction equipment, leading to more optimal dust reduction effects. This necessitates the introduction of the Kalman filtering algorithm. Despite the traditional single Kalman filtering algorithm's ability to make certain dust concentration predictions, it is constrained by high-temperature, high-humidity underground environments and electromagnetic pulse signal interference from fan and coal mining machine operations, with an error rate reaching up to 40 %, seriously disrupting underground dust reduction equipment. However, the composite Kalman filtering algorithm incorporating the 3σ rule effectively eliminates bad values and removes instability from the underground environment and noise, rendering it applicable to most complex environments, providing accurate predicted concentrations for dust reduction equipment, and boosting overall universality. This study designed a fusion algorithm based on the Pauta criterion and Kalman filter to further optimize the dust concentration detection technology based on electrostatic induction. The sensor's model and measuring principle were first analyzed, and the initial calibration and precision testing of the sensor using the experimental system were completed. The dust concentration fluctuation characteristics were then modeled with Matlab, and the noise variance was estimated to process and filter the dust concentration data with the Pauta criterion, Kalman filter, and fusion algorithm respectively. The accuracy of the dust concentration sensor was tested again after applying the fusion algorithm, which proved to significantly enhance the stability and accuracy of the electrostatic induction-based dust concentration sensor. This study has critical implications for coal mine dust concentration monitoring and coal miner occupational health protection.

An Analysis of the Methane Explosion in the Area of the Return Shaft Bottom at Mine

Methane explosions are one of the greatest hazards in the coal mining industry and have caused many accidents. On 27 July 2016 at approximately 11:01 a.m., an explosion of methane occurred at the bottom of Zygmunt return shaft at the depth of 411 metres. The explosion resulted in one casualty. The article presents the results of, and the conclusions from, an in-depth analysis of the changes in the parameters of mine air, especially methane concentration, air flow and the operation of mine fans, recorded by sensors installed in the workings and in Zygmunt ventilation shaft around the time of the accident. The analysis was based on signals recorded by the monitoring system, related to the evolution of methane and fire hazards prior to and after the accident occurred. An attempt was made to identify the cause and the circumstances of the methane explosion at the bottom of the return shaft.

The impact of real-time carbon dioxide awareness on occupant behavior and ventilation rates in student dwellings

Although existing standards typically prescribe fixed ventilation rates, a large portion of the building stock lacks mechanical ventilation systems. Such buildings obtain outdoor air through unintentional infiltration, open windows, and the operation of exhaust fans, which are mainly dependent on user awareness and behavior. This study investigates whether the presence of a simple CO2 meter display can alter user behavior and improve indoor air quality (IAQ) in dwellings. We conducted a two-week monitoring of CO2 concentration, air temperature, and relative humidity in 60 student dwellings (bedrooms and living rooms) in Denmark and Switzerland. During the first week, the CO2 display was concealed, and occupants adhered to their usual routines. In the second week, occupants used the display's visual feedback to enhance IAQ when necessary. Results revealed that over 95% of dwellings witnessed a reduction in median CO2 levels during the second week, both overall and in individual rooms. Furthermore, a descriptive analysis of CO2 concentration step changes exceeding the thresholds of “normal variation” showed an increase in the number of negative step changes, indicating a shift in user behavior. These findings underscore the efficacy ofa display interface providing information on the indoor environment in triggering behavior changes and improving IAQ in dwellings.

Reducing inter-unit pollutant transfer through multifamily unit compartmentalization

Compartmentalization, which refers to air sealing each unit within a building from the exterior and other interior spaces, has been proposed as a strategy to improve indoor air quality and energy efficiency in multifamily buildings. This study collected field data on air tightness and pollutant transfer in three new-construction multifamily buildings in California, which was used to develop a model in CONTAM that simulated the impact of leakage levels, ventilation strategies, and climate zones on inter-unit pollutant transfer in multifamily buildings. Air leakage testing found an average total unit leakage of 0.8 L/s50/m2, almost twice as tight as California’s current compartmentalization requirement (1.5 L/s50/m2). Two buildings designed with balanced ventilation systems were measured to have imbalanced continuous unit ventilation flows, which were further imbalanced by intermittent exhaust fan operation. Tracer gas testing in two buildings indicated that only about 1–3% of the total air entering a unit came from each neighbouring unit. Furthermore, all particles were apparently removed along the way, as there was no observable particle matter transfer at the tested air tightness levels (0.6–0.9 L/s50/m2). Modelling results indicated that leakier units led to greater dilution of pollutants generated within the unit but increased gaseous pollutant transfer from neighbouring units. The average concentration of benzene, a proxy gas for cigarette smoke, transferred into non-smoking units from neighbours who did smoke almost doubled, surpassing acceptable exposure levels, in the leaky simulation (2.3 L/s50/m2) compared to the tight simulation (0.8 L/s50/m2). Overall, this study suggests that stricter compartmentalization requirements should be adopted in multifamily building code updates, as tighter requirements appear to be manageable for builders and beneficial for indoor air quality when combined with mechanical ventilation.

Supercritical Operation of Bearingless Cross-Flow Fan

This paper presents a decoupled bearingless cross-flow fan (CFF) that operates at a supercritical speed, thereby increasing the maximum achievable rotational speed and fluid dynamic power. In magnetically levitated CFF rotors, the rotational speed and fan performance are limited by the bending resonance frequency. This is primarily defined by the low mechanical bending stiffness of the CFF blades, which are optimised for fluid dynamic performance, and the heavy rotor magnets on both rotor sides, which add significant mass but a minimal contribution to the overall rotor stiffness. This results in detrimental deformations of the CFF blades in the vicinity of the rotor bending resonance frequency; hence, the CFF is speed-limited to subcritical rotational speeds. The novel CFF rotor presented in this study features additional mechanical decoupling elements with low bending stiffness between the fan blades and the rotor magnets. Thus, the unbalance forces primarily deform the soft decoupling elements, which enables them to pass resonances without CFF blade damage and allows rotor operation in the supercritical speed region due to the self-centring effect of the rotor. The effects of the novel rotor design on the rotor dynamic behaviour are investigated by means of a mass-spring-damper model. The influence of different decoupling elements on the magnetic bearing is experimentally tested and evaluated, from which an optimised decoupled CFF rotor is derived. The final prototype enables a stable operation at 7000 rpm in the supercritical speed region. This corresponds to a rotational speed increase of 40%, resulting in a 28% higher, validated fluid flow and a 100% higher static pressure compared to the previously presented bearingless CFF without decoupling elements.

Gated recurrent unit-based data-driven model for predicting pot temperature in induction cooking systems

On an induction cooker, accurate pot temperature monitoring can cut down on energy use and prevent overheating. It can be challenging to create a mathematical model for predicting pot temperature, though, because of the different materials and sizes of the pots and the intricate electromagnetic coupling between the induction coil and the pot. To solve this problem, this paper offered a data-driven model that forecasts pot temperature by the inverter module's measured temperature. We used thermocouples in contact with the bottom surfaces of the pots and inverters to record time-series data on the temperatures of the devices to make accurate predictions. This information was gathered under a variety of circumstances, including various pot sizes and materials, various power and temperature settings, and various water levels. We used a gated recurrent unit-based autoencoder to reduce noise in the inverter temperature that was brought on by the cooling fan operation. The data-driven model was then trained using a variety of machine learning and deep learning techniques, including support vector machines, decision trees, linear regression, artificial neural networks, and gated recurrent units. Finally, we compared the predicted and measured pot temperatures to validate the data-driven models that had been learned. According to the statistical findings, there was a 3 °C or so median temperature difference between predicted and actual temperatures.

ТЕРМО- І АЕРОМОДЕЛІ ЕНЕРГЕТИЧНОГО ОБЛАДНАННЯ ЖИТЛОВИХ КОМПЛЕКСІВ

During accidents or destruction of the infrastructure of residential complexes at low temperatures, it is necessary to restore the operation of heat supply systems in a short time. It is convenient to use gas tube boilers for this. But we need new solutions to the problems of increasing the power and energy efficiency of equipment and systems due to the reduction of resistances to the movement of liquids or gases, as well as the intensification of heat transfer. Numerous studies have shown that an increase in the heat transfer coefficient at the gas-metal wall interface by 2-5 times leads to an increase in energy consumption of boiler fans by 10 times or more. The article uses three research methods to improve the performance of boilers. Visual diagnostics of the movement of liquids and gases made it possible to identify signs of self-organization of the flow structure. Hydraulic studies in slot channels, where only the height h varied in the range h = 0.2-2.5 mm, confirmed that the distribution structure of the pulsation components of the dynamic part of the energy affects the increase or decrease in speed at a given initial pressure. The thermal experiment showed that the flow structure also affects the nature of the change in the heat transfer coefficient. For channel sizes where the pulsation components have positive values, the increase in the heat transfer coefficient is much more intense than for sizes where the pulsations have negative values. That is, visual studies of the flow structure and the correct choice of transverse channel sizes can solve the problem of increasing the flow up to 24% without additional energy costs, as well as eliminate the problem of uncertainty when solving the problem of intensifying heat transfer at the gas-metal wall boundary. Visual studies of the jet in a flooded space provide information for solving the problem of intensifying heat transfer. The use of turbulators in gas-tube boilers ensured an increase in boiler efficiency from к.1 = 0.84 to к.2 = 0.929. At the same time, the energy consumption for fan operation changed slightly. The use of visual diagnostics of the flow structure makes it possible to solve hydraulic and thermal problems when developing or improving energy equipment for housing complexes.

Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion

Axial fans may be equipped with passive flow control devices to enhance rotor efficiency or minimize noise emissions. In this regard, blade designs influenced by biomimicry, such as rotors with sinusoidal leading edges (LEs), have gained popularity in recent years. However, their design is predominantly driven by a trial-and-error approach, with limited systematic studies on the influence of rotor performance. Furthermore, their effectiveness is typically evaluated under controlled conditions that may significantly differ from operations in real installation layouts. In this work, a systematic review of the design process for sinusoidal LE axial fan rotors is provided, aiming to summarize previous design experiences. Then, a modified sinusoidal LE is designed and fitted to a 7.3 m low-speed axial fan for air-cooled condensers (ACCs). These fans operate at environmental conditions, providing a quasi-zero static pressure rise, often with inflow non-uniformities. A series of RANS computations were run to simulate the performance of the baseline fan and that of the sinusoidal leading edge, considering a real installation setup at Stellenbosh University, where the ACC is constrained between buildings and has a channel running on the ground below the fan inlet. The aim is to explore the nonbalanced inflow condition effects in both rotor geometries and to test the effect of the installation layout on fan performance. The results show that the modification to the rotor allows for a more even distribution of flow in the blade-to-blade passages with respect to the baseline geometry.

A two-level fusion model of vibro-acoustic signals for centrifugal fan blade crack detection

Blade crack detection is the key to ensuring the smooth and safe operation of centrifugal fans. However, a single vibration signal is difficult to fully reflect the health state of the blade and is susceptible to noise interference in the industrial field, which makes it difficult to detect blade cracks. Therefore, a two-level fusion model of vibro-acoustic signals is proposed for blade crack detection of centrifugal fans. Firstly, based on the designed correlated degree of cyclostationarity fusion rule, the data-level fusion of multi-source homogeneous vibro-acoustic signals is completed, and the fused signals with more obvious fault features are obtained. Then, a one-dimensional feature pyramid network is proposed to extract the vibro-acoustic features and generate initial decisions. Finally, a basic probability assignment acquisition method based on the precision of the initial classifiers and a weighted average method based on the Pignistic probability distance are proposed to minimize the conflict between multi-source evidence, and the Dempster-Shafer evidence theory method is used to obtain the blade crack detection results. The effectiveness of the proposed method is verified by the centrifugal fan blade crack detection experiments. Compared with other related methods, the proposed method has better detection performance and stronger robustness.

Mitigation of Exciton Quenching Sites in All‐Metal‐Oxide‐Based Transparent Photovoltaic

Transparent photovoltaic (TPV) devices offer the potential to generate power without being visible to the human eye, making them ideal for use in building integrated photovoltaic applications. TPV devices based on inorganic materials offer eco‐friendly frameworks with stable performances. However, their low power conversion efficiency and incapacity to produce onsite power for real‐time practical applications limit their widespread deployment. Mitigation of exciton quenching by reducing the interface and bulk recombination can significantly improve the performance of TPVs. To address this, the present study investigates the effect of passivation layers (PLs) in all‐metal‐oxide TiO2/Cu2O TPV. The TiO2/Cu2O TPV interface is passivated by depositing thin Al2O3 and Ga2O3 films. The study comprehensively analyzes how passivation controls the interfacial and bulk defects. Electrochemical impedance spectroscopy and X‐ray photoelectron spectroscopy are used to elucidate exciton quenching mechanisms. The results show that the insertion of a thin PL on top of TiO2 effectively mitigates exciton quenching by suppressing hydroxyl ions, Ti2+, and Ti3+ bulk states. Ga2O3 PL, in particular, leads to a substantial enhancement in short‐circuit current density (12.4 mA cm−2) and open‐circuit voltage (669 mV). The study also demonstrates the real‐time onsite energy production and its utilization through the operation of an electric fan.

Influence of Ventilation on Formation and Growth of 1-20 nm Particles via Ozone-Human Chemistry.

Ozone reaction with human surfaces is an important source of ultrafine particles indoors. However, 1-20 nm particles generated from ozone-human chemistry, which mark the first step of particle formation and growth, remain understudied. Ventilation and indoor air movement could have important implications for these processes. Therefore, in a controlled-climate chamber, we measured ultrafine particles initiated from ozone-human chemistry and their dependence on the air change rate (ACR, 0.5, 1.5, and 3 h-1) and operation of mixing fans (on and off). Concurrently, we measured volatile organic compounds (VOCs) and explored the correlation between particles and gas-phase products. At 25-30 ppb ozone levels, humans generated 0.2-7.7 × 1012 of 1-3 nm, 0-7.2 × 1012 of 3-10 nm, and 0-1.3 × 1012 of 10-20 nm particles per person per hour depending on the ACR and mixing fan operation. Size-dependent particle growth and formation rates increased with higher ACR. The operation of mixing fans suppressed the particle formation and growth, owing to enhanced surface deposition of the newly formed particles and their precursors. Correlation analyses revealed complex interactions between the particles and VOCs initiated by ozone-human chemistry. The results imply that ventilation and indoor air movement may have a more significant influence on particle dynamics and fate relative to indoor chemistry.

Numerical simulation of aerodynamic processes in the fan in the diesel locomotive cooling module

The article is devoted to the numerical assessment of the characteristics of the fan of the cooling module of a diesel locomotive. In the work, the authors consider modern methods and approaches to numerical modeling of fans used in cooling systems of railway diesel locomotives. The focus is on fan performance analysis. The results obtained allow us to better understand and optimize fan operation in the context of diesel locomotive cooling systems, which can help improve the efficiency and reliability of these systems as a whole. The study is important for engineers and specialists in the field of railway transport.

Design and fabrication of a system to capture ambient CO2


 
 
 
 Introduction:In the coming decades, addressing climate change necessitates substantial Carbon dioxide (CO2) emission reductions. Carbon capture and storage are vital for achieving these goals. Beyond industrial emissions, Direct Air Capture (DAC) extracts CO2 from the atmosphere, complementing point source capture and enabling the reduction of atmospheric CO2 concentrations. Our research confirms the thermodynamic feasibility of DAC with Potassium hydroxide (KOH) solution, taking into account energy and performance considerations.
 Materials and methods: To assess DAC's potential, we built a 1.2 m contactor prototype measuring CO2 absorption from the air. Operating at 100 pa with an air speed of 1.75 m/s in a cross-flow regime, we used KOH and NaOH solutions as capture mediums, implementing duty cycles for absorbent pumping and exhaust fan operation.
 Results: Our findings revealed that transitioning to intermittent operation can dramatically reduce overall energy costs by 70%. We explored various absorbent concentrations for both KOH and NaOH solutions, examining their impact. Operating temperatures ranged from 14°C to 33°C, providing insights into temperature's pivotal role in DAC performance.
 Conclusion: This study showcases the viability of DAC with a KOH solution, particularly highlighting the significant energy savings achieved through intermittent operation. These findings emphasise DAC's role as a vital tool in our collective efforts to combat climate change.
 
 
 

Design and Implementation of an Electronic Fan Regulator for Reduced Harmonics and Ripple Free Speed

Majority electronic fan regulators available in the market feed significant amounts of harmonics into the fan, which leads to fan overheating and frequent failures of fan capacitors. This paper presents a design and development of a new electronic fan regulator that feeds negligible amounts of harmonics into the fan, and hence offers more reliable fan operation with smooth control and ripple free speed.The paper first reviews different forms of power electronic based control applicable to single-phase induction motors, and then identifies six topologies suitable for ceiling fans, based on the simplicity and cost effectiveness in meeting the performance targets. Final topology for the new design was selected after simulation of each short-listed topology to assess relative performances in terms of lesser harmonics, ripple free speed, smooth control, and cost. Finally, a prototype was built of the selected topology for a 70W single phase ceiling fan and test results verified the simulation results. Details of investigations, design, simulation, and test results are given and discussed.

Surrogate modelling of the high-static-pressure fan for high-speed trains and its dynamic airtightness analysis using CFD

Pressure protection devices are installed in ventilation systems to coordinate the air quality and pressure fluctuations inside high-speed trains, wherein the active pressure protection device (APPD) that adopts high-static pressure fans (HSPFs) is superior in maintaining favourable air quality. However, it is complicated to model an actual channel of an HSPF, and its airtightness performance, which could cause ear discomfort for occupants, has been unclear until now. In this study, a surrogate model based on a porous medium is presented to simulate HSPF operations. This model is validated by reference values and field experiments, which can accurately represent its inhibition effect on pressure transmission inside and outside the vehicle. Based on the proposed model, the exterior pressure fluctuation parameters, mode of fan operation and fan performance curve were selected to analyse the dynamic sealing capability of the HSPF. The results showed that the mode of HSPF_on can effectively restrain the pressure transmission compared to the normal fan and the mode of HSPF_off, whose dynamic airtightness index (τdyn) is scarcely affected by the external pressure fluctuation, with a value between 20 s and 23 s. In addition, improving the fan performance can enhance the dynamic airtightness of the HSPF, and τdyn increases by approximately 3.5 s with the static pressure value rising by 1000 Pa. Moreover, a new method for investigating the dynamic airtightness of HSPFs is provided in this study, and this method can be used to guide the airtightness design of APPDs relying on HSPFs.

Sex-based thermal comfort zones and energy savings in spaces with joint operation of air conditioner and fan

Fan and air conditioner combined systems (FACS) have been demonstrated as a viable alternative to conventional air conditioning systems, providing thermal comfort to occupants while consuming less energy. However, few studies have quantitatively established occupant comfort zones for FACS operation and analyzed its energy saving effects. An experiment was conducted first to develop thermal comfort zone in spaces with FACS operation. As the indoor temperature rises, the upper limit of air speed accepted by occupants increases. Females exhibit an upper comfort range parameter of 29.8 °C and 1.4 m/s, while males demonstrate 29.3 °C and 1.5 m/s. There are noticeable differences in comfort ranges between males and females, especially in cooler conditions. Based on the established comfort zone, energy simulation studies were conducted for most regions of China to investigate the potential energy savings resulting from the implementation of FACS in ASHRAE standard office building. Buildings incorporating FACS demonstrate a reduction in HVAC system energy consumption by more than 16 % when compared to indoor temperature set at 26 °C. In hot summer and warm winter climates, HVAC system energy savings of over 100 GJ/year can be achieved using FACS for the standard building. Considering sex differences in FACS operation leads to additional energy savings.

Utilization and Development of Libas (Spondias Pinnata) Spray-Dried Powder

In this study, the effect of maltodextrin concentration on the physico-chemical, sensory and storage characteristics of Libas (Spondias pinnata) powder produced by spray drying was investigated. Initially, fresh Libas leaf extracts were drawn out in distilled water heated at 100°C for 30 minutes. 10, 20 and 30% maltodextrin was added to the solution prior to sieving. These solutions were then atomized in a pilot scale centrifugal spray dryer at an inlet temperature of 180°C, material cooling temperature of 70°C, fan operation frequency of 60 Hz, atomizer operation frequency of 300 Hz and mean outlet temperature of 125°C. Spray dried Libas leaf powder was analyzed for product yield, pH, moisture content, ash content and solubility time. The level of acceptability of the spray dried Libas leaf powder was also assessed in terms of appearance, taste, aroma, mouthfeel and overall acceptability using a 9-point hedonic scale conducted on thirty (30) sensory panelists. Findings of the study revealed that maltodextrin concentration significantly affected various physico-chemical, sensory and storage characteristics of spray dried Libas leaf powder. Product yield, solubility and residual moisture content were found to be significantly improved by an increase in maltodextrin concentration. However, it was also found that there is a decrease in the ash content and level of acceptability of the spray dried samples with an increase in maltodextrin concentration. Storage of the spray dried Libas leaf powder for six (6) months significantly affected pH and moisture content. No significant difference in sensory characteristics was detected among treatments indicating that powder quality is still acceptable during the six (6) months storage period.

Aerodynamics and Aeroacoustics of Leading Edge Serration in Low-Speed Axial Fans With Forward Skewed Blades

Abstract Low-speed axial fans must comply with a wide number of standards and normative restrictions, often related to the maximum noise emission levels. Among the noise control techniques in axial fans, skewed fan blades and leading edge serrations have been found to be effective in leading edge noise control, which represents one of the dominant phenomena in axial fan broadband emissions. However, these solutions are usually applied separately, and literature is scarce on systematic studies on the coupling of the two modifications. In this work, a campaign of experimental measurements was conducted on unskewed and forward-skewed axial fan blades with and without leading-edge serrations. The tests were performed in undisturbed inflow conditions. The flow field and the turbulence characteristics were measured using three-dimensional hot-wire anemometry. The suction-side sound radiation of the fans was measured with microphones in an anechoic chamber. In addition, the rotating beamforming method was used to localize the sound sources at the axial fans. It was found that, regardless of the blade skew, the leading edge serrations lead to a reduction of the sound pressure level, whereby the aerodynamic properties of the fan decrease. At the same operating points, which were achieved by adjusting the rotational speed, the sound radiation through the leading edge serrations could be reduced at high-volume flows. This effect was more pronounced with the unskewed rotor, which indicates that the positive effect of the serrations is reduced by the already optimized shape of the forward skewed fan blade. Based on the experimental results, the four geometries were further considered for numerical investigations to understand how the serrations affect the fan operations and the overall aerodynamics of the rotor. All four geometries were simulated with RANS approach at the duty point to derive a flow survey and better understand the dynamics driven by serrations and blade skewing.

Lorentzian Fans

Abstract We introduce the notion of Lorentzian fans, which form a special class of tropical fans that are particularly well-suited for proving Alexandrov–Fenchel-type inequalities. To demonstrate the utility of Lorentzian fans, we prove a practical characterization of them in terms of their two-dimensional star fans. We also show that Lorentzian fans are closed under many common tropical fan operations, and we discuss how the Lorentzian property descends to the underlying tropical variety, allowing us to deduce Alexandrov–Fenchel-type inequalities in the general setting of tropical intersection theory on tropical fan varieties.