Fan Operation Research Articles

Simple controllable foam structure NiCo2S4 for high-performance hybrid supercapacitors

In this work, to reduce the “dead volume” due to the accumulation of synthesized products, the foam-structured NiCo2S4 (FSNCS) with a specific surface area of 25.4 m2g −1 was successfully synthesized by using well-dispersed SiO2 nanospheres as the framework. The FSNCS exhibited 559.3 C g −1 at a current density of 1 A g −1, which was 173.3 C g −1 higher than the performance of the NCS synthesized without the addition of SiO2. Additionally, a hybrid supercapacitor is successfully assembled with FSNCS as the positive electrode and active carbon (AC) as the negative electrode. The FSNCS//AC displays maximum specific energy of 28.8 Wh kg−1 at a specific power of 375.0 W kg−1, together with good cyclic life with 88.9% capacity retention over 5000 cycles at 8 A g −1. It is worth noting that the hybrid supercapacitor can provide strong power for the operation of the motor fan. The simple structure design provides an innovative and effective way to develop high-performance energy storage devices.

The Relationship between Bacterial Load and Initial Run Time of a Surgical Helmet.

Periprosthetic joint infection (PJI) is a complication of arthroplasty surgery with significant morbidity and mortality. Surgical helmets are a possible source of infection. Pre-existing dust and microorganisms on its surface may be blown into the surgical field by the helmet ventilation system. Twenty surgical helmets at our institution were assessed through microscopy and polymerase chain reaction testing. Helmets were arranged with agar plates under the front and rear outflow vents. Helmets ran while plates were exchanged at different time points. Bacterial growth was assessed via colony counts and correlated with fan operating time. Gram staining and 16S sequencing were performed to identify bacterial species. The primary microbiological contaminate identified was Burkholderia. There was an inverse relationship between colony formation and fan operating time. The highest number of colonies was found within the first minute of fan operating time. There was a significant decrease in the number of colonies formed from the zero-minute to the three (27 vs 5; P = <.01), four (27 vs 3; P = <.01), and five-minute (27 vs 4; P = <.01) time points for the front outflow plates. A significant difference was also observed between the one-minute and four-minute time points (P = .046). We observed an inverse relationship between bacterial spread helmet fan operation time, which may correlate with dispersion of pre-existing contaminates. To decrease contamination risk, we recommend that helmets are run for at least 3 min prior to entering the operating room.

Multifidelity simulation of underhood thermal system for a bus engine

This study performs a combined 0-dimensional/3-dimensional modelling approach to investigate the fluid flow and heat transfer characteristics of bus thermal management systems. The 3-dimensional model is deployed to develop new correlations for the heat transfer coefficient (Colburn-j factor) and the friction factor (Fanning-f factor) at the air-side of the multi-louver radiator and charge-air cooler. The effect of the fan operation is also taken into account. The existing correlations in the literature developed for cars where the radiator and charge-air cooler are placed in the front section of the vehicle exposed to a uniform incoming air flow. While in buses, these components are placed at the vehicle rear section and in contact with a turbulent and non-uniform air flow, highlighting the need for development of new Colburn-j factor and Fanning-f factor for air flow within the louvered fins in these two components. The coefficients developed are incorporated into the 0-dimensional model to predict the thermal characteristics of the bus underhood for a range of operating conditions. The 0-dimensional model simulates the heat interaction of the multiple thermodynamic systems. Thus, a better understanding of the thermal management is achieved by investigating the energy distribution within the engine compartment and describing the performance of the thermal systems. The 0-dimensional/3-dimensional model is examined under the peak brake power condition. A coolant mass flow rate of 3.74 kg/s and fans speed of 4000 rpm are the most optimum results since the coolant’s temperature is decreased by 5 °C and the parasitic losses are kept at minimum.

Flutter of Fan Blades in the Aircraft Engine in the Three-Dimensional Subsonic Gas Flow

Aeroelasticity problems arise in the different fields of technology. The accident-free operation of the airborne machines is one of the most important factors that should be taken into account during their designing and upgrading. The solution of this problem involves the implementation of many measures to provide the system reliability on the whole, including its individual elements, in particular aircraft engine, its fan whose wide-chord blades can be exposed to the wreckage due to different reasons including the aeroelastic effects, i.e. self-excited vibrations. As a result, the origination of the aeroelastic phenomenon (flutter) in design and off-design modes should be eliminated at the stage of the design and operational development of the rotor wheel that would result in a considerable increase of the level of reliability of the aircraft engine. Based on the analysis of the available methods used for the flutter prediction we can draw a conclusion that the most promising approach to the analysis of the aeroelastic behavior of the blade ring of fan is the use of the method based on the three-dimensional model of the aerodynamics and dynamics (the method used for the solution of the coupled aeroelastic problem). By solving the coupled aeroelastic problem of the nonstationary aerodynamics and elastic vibrations of the blades we can get the amplitude –frequency blade vibration spectrum for the three-dimensional gas flow, including forced vibrations and self-excided vibrations in order to increase the reliability of the blade row of turbine machines. The developed numerical method was used for the analysis of the aeroelastic behavior of the blade ring of the fan mounted in the airborne engine for the operation mode of 3520 rmp with appropriate boundary conditions at the inlet and outlet behind the ring. The computation data confirmed the origination of self-vibrations for the given fan operation mode.

Performance and operability of an electrically driven propulsor

This manuscript discusses the operation of an electrically driven fan for a hybrid-electric propulsion system for BAe-146 aircraft. The thrust requirement is fed into an integrated cycle and aerodynamic design tool for the sizing of a ducted fan as one of the main propulsors, podded under the wing as a replacement for a turbofan engine. The electric motor design is initiated with the torque and speed requirements and with the dimensional constraints arising from the driven fan geometry. The fan operation and aerodynamic design are derived by changing the fan pressure ratio and hub-to-tip ratio to obtain a 2-D design space. Surface-mounted permanent magnet electric motor designs are mapped on the 2-D fan design space. The design and operational flexibility of the system is investigated through three scenarios. In the first scenario, the aircraft rate of climb is changed to downsize the electric motor. In the second scenario, the electric motor rated frequency is changed to increase the power density and in the third scenario the electric motor current density is changed for the same purpose. The investigated three scenarios provide design and operational guidelines for reducing the weight of the electric motor for a direct drive application.

Ceiling-fan-integrated air-conditioning: thermal comfort evaluations

Ceiling-fan-integrated air-conditioning (CFIAC) is a concept in which terminal supply ducts and diffusers are replaced by vents/nozzles that jet supply air into the vicinity of ceiling fans to be mixed and distributed within the room. CFIAC distributes the supply air within the room and convectively cools the occupants. This could allow raised thermostat set-points and reduced energy for the air-conditioning system’s supply fan and compressor. Previous work on CFIAC shows that the air temperature in the occupied zone is spatially uniform, but the air speed is not. This paper evaluates the thermal comfort performance of a CFIAC system under various ambient temperatures and fan operation modes. Human subject experiments and thermal manikin tests were conducted to characterize how subjects evaluate the thermal comfort performance across the room’s floorplate, and how CFIAC affects human body heat transfer. Despite the spatial variation in air speed across the floorplate, CFIAC created uniform thermal comfort perceptions. Comfort at 28°C was similar to that of 26°C for the overhead supply neutral reference condition. Human subjects preferred having the increased air movement over that of the reference condition. The paper evaluates thermal comfort indexes appropriate for evaluating and designing CFIAC. <em><strong>Practice relevance</strong></em> Despite the spatial variation in air speed across the floorplate, CFIAC created quite uniform thermal comfort perceptions. Conventional air-conditioning systems often create overcooling complaints because supply volumes through diffusers are kept overly high in order to disperse cold temperature dumping in the space. Ceiling fan circulation provides sufficient dispersion to eliminate this issue. However, it is important for standards writers and designers to understand that the room temperatures should not be so cold that the highest airspeeds caused by the ceiling fans will be uncomfortable for the occupants in the fan-cooling zone. To evaluate CFIAC systems, the standard effective temperature (SET) model is shown to be useful and the elevated air speed method in American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55 also provides appropriate design guidance.

Double-Ducted Fan as an Effective Lip Separation Control Concept for Vertical-Takeoff-and-Landing Vehicles

This paper describes a novel inlet flow conditioning concept that significantly improves ducted fans’ performance and controllability. High angle-of-attack operation of ducted fans is very common in vertical-takeoff-and-landing systems. The new concept named double-ducted fan (DDF) uses a secondary shroud to control inlet lip-separation-related momentum deficit at the inlet of the fan rotor during edgewise flight. The DDF is helpful in a wide edgewise flight velocity range, and its corrective aerodynamic effect becomes more pronounced with increasing flight velocity. A conventional baseline duct operating at 90 deg angle of attack is compared to other novel double-ducted fan designs via three-dimensional, viscous, and turbulent flow computations. A custom actuator-disk model replaces the zonal computation of the complex and three-dimensional rotor flowfield in the rotating frame of reference. Both hover and edgewise flight conditions are considered around the ducted fan unit and inside the ducts. Significant improvements from several novel ducted fan designs are in the areas of vertical thrust enhancement, nose-up pitching moment reduction, and recovery of fan through-flow mass flow rate in a wide horizontal flight range. A variable DDF design, a partial DDF design, and a fan-in-wing implementation of the DDF are introduced.

Research on Fan Operation Evaluation and Error State Judgment Relying on Improved Neural Network and Intelligent Computing

Fan, as the most commonly used mechanical equipment, is widely used. In order to solve the problem of fan bearing fault diagnosis, this paper analyzes the main factors affecting fan spindle speed and power generation in operation. The input and output parameters of the performance prediction model are determined. The performance prediction model of wind turbine is established by using generalized regression neural network, and the smoothing factor of GRNN is optimized by comparing the prediction accuracy of the model. Based on this model, the sliding data window method is used to calculate the residual evaluation index of wind turbine speed and power in real time. When the evaluation index continuously exceeds the pre-set threshold, the abnormal state of wind turbine can be judged. In order to obtain wind turbine blades with better aerodynamic performance, a blade aerodynamic performance optimization method based on quantum heredity is proposed. The B é zier curve control point is used as the design variable to represent the continuous chord length and torsion angle distribution of the blade, the blade shape optimization model aiming at the maximum power is established, and the quantum genetic algorithm is used to optimize the chord length and torsion angle of the blade under different constraints. The optimization results of quantum genetic algorithm and classical genetic algorithm are compared and analyzed. Under the same parameters and boundary conditions, the proposed blade aerodynamic optimization method based on quantum genetic optimization is better than the classical genetic optimization method, and can obtain better blade aerodynamic shape and higher wind energy capture efficiency. This method makes up for the shortcomings of traditional fault diagnosis methods, improves the recognition rate of fault types and the accuracy of fault diagnosis, and the diagnosis effect is good.

Analysis of Selected Operating States of the Line Start Synchronous Reluctance Motor Using the Finite Element Method

The article presents the results of work on an effective numerical study of selected transient states of a low-power electrical machine. The object of detailed research was a synchronized squirrel-cage induction motor. Its ability to work at a synchronous speed was enabled by obtaining reluctance torque, caused by an imposed asymmetry between the direct and quadrature reluctances of the rotor. The difference between the reluctances was achieved by changing the rotor geometry by milling additional deep grooves. The modifications of the rotor did not damage the continuity of the rotor cage. Imposed lots were arranged symmetrically around the rotor circumference. In order to study the performance of the modified motor, a parameterized, numerical model of the machine was developed to evaluate the impact of the geometry of the slots. The developed three dimensional (3D) model of the electromagnetic phenomena in the studied magnetic circuit employs the finite element method (FEM). The model takes into account the saturation of the machine’s magnetic circuit and the skew of the rotor cage bars as well as the mechanical equilibrium of the terrain system including the moment of inertia and frictional torque in the bearings as well as the load torque resulting from the operation of the internal fan. The simulation study concerned the starting process of the machine under different values of the load. The influence of the supply voltage phase angle at the moment of start-up and the initial position of the rotor in relation to the stator was investigated. In order to calibrate the model, tests of the physical object were performed. The corrections introduced concerned the magnetization characteristics of the magnetic circuit. The results obtained confirm the correctness of the adopted strategy of testing the operational properties of the considered engine.

Identification of Rotor Crack Faults by Vibration Analysis

According to the vibration equation of the cracked rotor, the main vibration characteristics of the cracked rotor are summarized. On this basis, combined with the field diagnosis experience, a practical method of identifying the cracked rotor through vibration analysis is proposed. Furthermore, the proposed method is illustrated by three cases of rotor crack fault identification in the operation of steam turbine and boiler primary air fan. Successful diagnosis avoids the occurrence of potential major accidents.

An alternative air distribution solution for better environmental quality in the ISS crew quarters

This article presents the study of a ventilation solution using cross-flow fans for the crew quarters (CQ) aboard the International Space Station. Currently the CQ uses two axial fans for ventilation, which occasionally generate insufficient flow rate or acoustic issues. A ventilation circuit using two cross-flow fans was designed, its acoustic performance was measured and the flow was investigated via CFD by using the measured cross-flow fan operating curves as boundary conditions. The acoustic performance of the fans was evaluated in isothermal conditions, under the assumption that the heat generated by the occupants and equipment would produce negligible thermal buoyancy effects in microgravity on the station. Future studies will investigate how the internal heat generated in the enclosure affects the thermal comfort conditions of the occupants. After a comparison between the axial and cross-flow fan systems, results indicate that the latter provides better acoustic parameters for the same flow rate with less energy consumption.

An Adaptive Early Fault Detection Model of Induced Draft Fans Based on Multivariate State Estimation Technique

The induced draft (ID) fan is an important piece of auxiliary equipment in coal-fired power plants. Early fault detection of the ID fan can provide predictive maintenance and reduce unscheduled shutdowns, thus improving the reliability of the power generation. In this study, an adaptive model was developed to achieve the early fault detection of ID fans. First, a non-parametric monitoring model was constructed to describe the normal operating characteristics with the multivariate state estimation technique (MSET). A similarity index representing operation status was defined according to the prediction deviations to produce warnings of early faults. To deal with the model accuracy degradation because of variant condition operation of the ID fan, an adaptive strategy was proposed by using the samples with a high data quality index (DQI) to manage the memory matrix and update the MSET model, thereby improving the fault detection results. The proposed method was applied to a 300 MW coal-fired power plant to achieve the early fault detection of an ID fan. In addition, fault detection by using the model without an update was also compared. Results show that the update strategy can greatly improve the MSET model accuracy when predicting normal operations of the ID fan; accordingly, the fault can be detected more than 4 h earlier by using the strategy with the adaptive update when compared to the model without an update.

Emergency responder and public health considerations for plastic sewer lining chemical waste exposures in indoor environments

The cured‐in‐place pipe (CIPP) manufacturing process is used to repair buried pipes, and its waste commonly discharged into the air can enter nearby buildings. Exposure can prompt illness and the need for medical care. A mass balance model was applied to estimate indoor styrene concentrations due to intrusion of CIPP emissions through plumbing under different bathroom ventilation conditions. To better understand building contamination and recommend emergency response actions, calculations to estimate chemical intrusion through plumbing were developed. Field reports and study calculations showed that contractor-applied external pressures during plastic manufacture have and can displace plumbing trap water seals. Modeled styrene vapor concentrations that entered the building (1, 300, 1000 ppm) were similar to those measured at CIPP worksites. Modeling revealed that in some cases, bathroom exhaust fan operation during a CIPP project may increase indoor styrene concentrations due to enhanced entrainment of styrene-laden air from the sink and toilet. However, styrene concentrations decreased with increasing air leakage across the bathroom door due to reduced suction from the plumbing system. CIPP waste discharge should be treated as a hazardous material release and can pose a threat to human health. Immediate building evacuation, respiratory protection, provision of medical assistance, source elimination, and building decontamination are recommended.

Modeling the Removal of Water-Soluble Trace Gases from Indoor Air via Air Conditioner Condensate

Water-soluble trace gas (WSTG) loss from indoor air via air conditioning (AC) units has been observed in several studies, but these results have been difficult to generalize. In the present study, we designed a box model that can be used to investigate and estimate WSTG removal due to partitioning to AC coil condensate. We compared the model output to measurements of a suite of organic acids cycling in an indoor environment and tested the model by varying the input AC parameters. These tests showed that WSTG loss via AC cycling is influenced by Henry's law constant of the compound in question, which is controlled by air and water temperatures and the condensate pH. Air conditioning unit specifications also impact WSTG loss through variations in the sensible heat ratio, the effective recirculation rate of air through the unit, and the timing of coil and fan operation. These findings have significant implications for indoor modeling. To accurately model the fate of indoor WSTGs, researchers must either measure or otherwise account for these unique environmental and operational characteristics.

Early fault detection for power plant fans based on dynamic neural network

Early fault detection is increasingly important for the reliable and secure operation of power plant fans. In this paper, we propose an early fault detection strategy for power plant fans based on dynamic neural network. First, the nonlinear autoregressive (NARX) with exogenous inputs network is utilized to predict the behavior of fans by using normal operating data, and the discrete particle swarm optimization (DPSO) is utilized to optimize the hyper-parameters of NARX network to enhance prediction accuracy. Then, the fault alarm strategy is proposed by the prediction deviations and generalized extreme value (GEV) theory. Finally, the proposed method is applied to a forced draft (FD) fan in a coal-fired power plant. Experiment results show that the proposed model has high prediction accuracy on normal operations and produces large prediction errors when a failure occurs. Furthermore, it can detect early faults accurately and timely before the failure occurs.

Improved Aerodynamics of a Hollow-Blade Axial Flow Fan by Controlling the Leakage Flow Rate by Air Injection at the Rotating Shroud.

Axial flow fans are used in many fields in order to ensure the mass and heat transfer from air, chiefly in the heating, ventilation and air conditioning industry (HVAC). A more proper understanding of the airflow behavior through the systems is necessary to manage and optimize the fan operation. Computational fluid dynamics (CFD) represents a real tool providing the ability to access flow structures in areas that measuring equipment cannot reach. Reducing the leakage flow rate, inherent in operation, by synthetic-jet techniques improves performance. This paper presents the CFD results performed on a hollow blade fan developed by our team. The leakage flow is controlled by blowing air from 16 designated circular holes and arranged on the fan shroud. We discuss the results for two rotational speeds (1000 and 2000 rpm) and two injection rates (400 and 800 L/min). The numerical results consistent with the experimental show, for the low rotation speed and high injection ratio, significant gains in power (53%), torque (80%) and leakage flow rate (80%).

Design, Development and Evaluation of Seaweed Drying Technology for Village Level Operation

A solar-type seaweed dryer was designed and developed to answer the needs of Filipino seaweed farmers for efficient and reliable drying technology. Through extensive baseline community surveys and field tests, the study was able to design a dryer prototype that is capable of drying high-grade quality seaweeds in a short amount of time. Moreover, geographical factors, natural hazard vulnerability, and farmers’ preference gave way for the development of two types of dryer: permanent and floating type. Both dryers were found to have positive effects in regards to drying time, product quality, streamlined operation, and overall economic benefits. Traditional drying practices takes around three (3) days to dry the seaweeds on good sunny days, but due to the varying weather conditions, the drying process can reach up to 7 days. The prolonged drying time, exposure to sudden downpours and contaminants greatly affects the quality of the seaweeds which in turn, compromises the market value of the dried seaweeds. The use of the drying technology remedied these problems inherent to traditional drying practices. To take full advantage on the use of the developed seaweed dryer, optimization experiments were conducted to determine the ideal settings of the dryer during daytime and nighttime conditions by varying the siding openings and operation of the exhaust fans. The optimization study resulted in a continuous and efficient drying operation under different weather conditions. Furthermore, field performance tests paved the way for the construction of a sturdier compact dryer design. Moreover, the incorporation of a solar-powered ventilation system and lighting system allowed continuous and efficient drying operation even during night time. Lastly, simple economic analysis also supported the profitability of drying technology in the long run.

Energy saving of fans in air-cooled server via deep reinforcement learning algorithm

The present paper aims at using an artificial intelligence algorithm to minimize the fan power consumption in air-cooled servers. The proposed algorithm can handle the complex thermal environments within the servers to tailor the influences and interactions amid numerous heat sources, airflow, bypass phenomenon, fan operation, and the transient operations. Modified correlations are first proposed to effectively predict the thermal-hydraulic performance of heat sinks and the corresponding predictive ability against Nusselt number and pressure drop is within 5.0% and 10%, respectively. Without the algorithm control, the maximum deviation between the prediction and the experimental data is within 2.0 °C. By introducing the deep reinforcement learning (DRL) algorithm subject to the interactions of complex thermal environments, the fan power consumption can be saved by 55.7%, 40.3% and 26.3%, respectively, in comparison with the strategy with 100% fan duty. Yet the DRL agent still offers 16.7% energy saving when compared to a fixed 40% fan duty.

Environmental impacts of implementing basket fans for heat abatement in dairy farms

Health and welfare impairments in dairy cows have been described to increase environmental impacts of milk production due to their negative effect on cow productivity. One of the welfare problems is heat stress, which is gaining importance even in temperate regions. While improving animal welfare may reduce emissions, the mitigation potential depends on the environmental costs associated with specific intervention measures. Taking abatement of heat stress as an example, the aim of the present study was to estimate the effect of implementing mechanical ventilation devices on the contribution potential of milk production to global warming (GWP), terrestrial acidification (TAP) and freshwater eutrophication (FEP). Environmental impacts of two modelled production systems located in alpine and lowland production areas of Austria were estimated before and after the implementation of basket fans, using life cycle assessment. Region-specific climate data were retrieved to determine the number of days with heat stress and to evaluate heat stress-induced productivity shortfalls in the baseline scenario (Sbasic). In the intervention scenario with increased ventilation (Svent), this decline was assumed to be eliminated due to the convective cooling effect of fans. For Sbasic, mean GWP, TAP and FEP impacts were estimated at 1.2 ± 0.09 kg CO2-, 21.1 ± 1.44 g SO2- and 0.1 ± 0.04 g P-equivalents per kg milk, respectively. Independent from the production system, in Svent, implementation of fans did not result in significant environmental impact changes, except for FEP of the alpine system (+5.9%). The latter reflects the comparatively high environmental costs of additional cooling regarding FEP (+2.3%) in contrast to GWP (+0.4%) and TAP (+0.1%). In conclusion, the estimated overall effects of mechanical ventilation on GWP, TAP and FEP of milk production were minor and the model calculations point to the potential of heat stress abatement to at least outweigh the environmental costs associated with fan production and operation. To confirm this trend, further assessments are needed, which should be based on primary data regarding the effectiveness of fan cooling to improve cow productivity, and on emission calculation schemes that are sensitive to environmental factors such as wind speed and temperature.

Cooling in Poor Air Quality Environments—Impact of Fan Operation on Particle Deposition

Environmental pollutants are a source for reliability issues across data center and telecommunications equipment. A primary driver of this is the transport and deposition of particle matter (PM$_{2.5}$, PM$_{10}$) on printed circuit boards, electronic components and heat exchange surfaces. This process is enhanced by turbulent air flows generated from cooling fans. Particle pollutants can persist after contemporary filtering, highlighting the importance of elucidating particle transport mechanisms and utilising this information to design robust equipment. This study investigates particle transport behaviour arising from axial fans operating under varied aerodynamic conditions. Transient, multi-phase numerical simulations were performed to model the flow of millions of microscale particles in air and determine their fate. Across a comprehensive range of fan operation conditions, from aerodynamic stall to free delivery, non-dimensional deposition velocities spanned an order of magnitude. Deposition profiles vary from monotonic to non-monotonic behaviour, influenced by local flow impingement, blade tip vortices, and shear velocity. A simple flow control solution that mitigates the factors influencing deposition has been demonstrated for equipment already deployed. The findings and numerical methods can be applied for the optimization of fan-cooled equipment intended for indoor and outdoor environments where air quality is poor, or pollution levels are high.