Characteristics Of Fan Research Articles

Study on the Influence of Inlet Asymmetry on Aerodynamic Noise of Cooling Fan

Abstract Experimental and numerical studies on the aerodynamic noise characteristics of a variable-speed axial fan commonly used for electronic device heat dissipation were conducted. First, the far-field noise spectrum of the fan was measured using a microphone on the contour plane of the fan axis. The spectral analysis indicated that the discrete single-tone noise energy ratio was high, which indicates that it was the dominant aerodynamic noise. Afterward, the double-uniform sampling point mode correction technique, which is based on the circumferential acoustic mode measurement method, was used to obtain the modal distribution on the inlet and outlet sides of the cooling fan. The influence of inlet unevenness on the cooling fan was identified. The traditional Tyler–Sofrin rotor–stator interaction formula was modified to account for the nonaxisymmetric shape of the fan inlet bellmouth. The validity of the modified formula was verified by measuring the circumferential acoustic modes of three cooling fans with different rotor and strut counts. Furthermore, a computational fluid dynamics (CFD) numerical study was conducted using Fluent to understand the influence of uneven inlet flow. The results showed that uneven inlet flow significantly affects the size and distribution of unsteady pulses on the rotor blades, which cause regular, periodic changes as the rotor blades rotate. Interactions between rotor blades and inlet unevenness were observed via the proper orthogonal decomposition (POD) method as well. The discussion of the circumferential modes from aerodynamic noise of an axial flow cooling fan can act as a reference for further cooling fan noise reduction measures.

Numerical study on the effect of the tip clearance of a 100 HP axial fan on the aerodynamic performance and unsteady stall characteristics

In this study, a numerical analysis was conducted to investigate the effect of the tip clearance on the aerodynamic performance, internal flow characteristics, and stall region characteristics of an axial fan. Three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes (RANS) calculations were conducted with a shear stress transport (SST) turbulence model. Tip clearance ratios of 0, 0.01, and 0.02 were applied to the impeller. As the tip clearance ratio increased, the aerodynamic performance of the axial fan decreased at both the design and the off-design conditions. The correlation between the tip leakage vortex (TLV) and the flow angle of the velocity triangle was presented for the difference in the tip clearance and flow rate. As the flow rate increased, the differences in the aerodynamic performance induced by the tip clearance ratio decreased. As the tip clearance ratio increased, the size of the TLV increased and gradually moved in the circumferential direction to interfere with the main flow at the low flow rate. Meanwhile, the size of the TLV was similar and gradually moved in the axial direction even if the tip clearance ratio increased at the high flow rate. The pressure fluctuations were observed by the fast Fourier transformation (FFT) analysis to compare and analyze internal flow characteristics at the stall region and design point. The static pressure was converted to the appropriate magnitude. The locations of the highest magnitude were shown to be different at the stall region and the design point, respectively.

Numerical Investigation of Performance and Flow Characteristics of a Tunnel Ventilation Axial Fan with Thickness Profile Treatments of NACA Airfoil

An axial flow fan, which is applied for ventilation in underground spaces such as tunnels, features a medium–large size, and most of the blades go through the casting process in consideration of mass production and cost. In the casting process, post-work related to roughness treatment is essential, and this is a final operation to determine the thickness profile of an airfoil which is designed from the empirical equation. In this study, the effect of the thickness profile of an airfoil on the performance and aerodynamic characteristics of the axial fan was examined through numerical analysis with the commercial code, ANSYS CFX. In order to conduct the sensitivity analysis on the effect of the maximum thickness position for each span on the performance at the design flow rate, the design of experiments (DOE) method was applied with a full factorial design as an additional attempt. The energy loss near the shroud span was confirmed with a quantified value for the tip leakage flow (TLF) rate through the tip clearance, and the trajectory of the TLF was observed on the two-dimensional (2D) coordinates system. The trajectory of the TLF matched well with the tendency of the calculated angle and correlated with the intensity of the turbulence kinetic energy (TKE) distribution. However, a correlation between the TLF rate and TKE could not be established. Meanwhile, the Q-criterion method was applied to specifically initiate the distribution of flow separation and inlet recirculation. The location accompanying the energy loss was mutually confirmed with the axial coordinates. Additionally, the nonuniform blade loading distribution, which was more severe as the maximum thickness position moved toward the leading edge (LE), could be improved significantly as the thickness near the trailing edge (TE) became thinner. The validation for the numerical analysis results was performed through a model-sized experimental test.

The Influence of the Blade Outlet Angle on the Flow Field and Pressure Pulsation in a Centrifugal Fan

This paper takes centrifugal fan as the research object and establishes five impeller models with different blade outlet angles. By means of computational fluid dynamics (CFD), the external characteristics of the centrifugal fan and the internal characteristics, including the velocity, pressure, and turbulent energy distribution, at the middle span plane of the impeller or fan were obtained and compared. In addition, the pressure fluctuations surrounding the impeller outlet were also analyzed. The results showed that the change of the blade outlet angle of the centrifugal fan had a great influence on the performance; the total pressure and efficiency of the fan were the highest when the outlet angle of the blade was increased to 29.5° under the design flow rate; and the influence of the outlet angle on the fan performance was different in off-design conditions. On the other hand, at different flow rates, the change of the internal flow field with the increase of the outlet angle was different. For the pressure fluctuation of the fan, by increasing the blade outlet angle properly under high flow conditions, the fluctuation amplitude of the fan at the blade frequency and its frequency multiplication could be reduced, which is conducive to decreasing the impeller noise. The research results have good guiding significance regarding the design of the pneumatic performance and noise reduction performance of centrifugal fans.

Investigation on Vortex Characteristics of a Multi-Blade Centrifugal Fan near Volute Outlet Region

The origins and effects of the complex vortex structure near the volute outlet of a multi-blade centrifugal fan are investigated in this paper. Due to the wide blade and short blade channel, the airflow maintains a large radial velocity during the blade channel. This continuous radial partial velocity causes vortices to be generated at the region of volute outlet. Then, the secondary flow close to the impeller generate from the center to the sides in volute. It is obtained that the streamlines are divided into two parts (backflow and outflow) at volute outlet. Although the vortices near volute outlet region are complex, the main features of flow behavior caused by the vortex are understandable.

The concept, characteristics and significance of fluvial fans

Abstract The concept and characteristics of fluvial fan are elucidated through literature review and case analysis. Firstly, the concept and terminology of fluvial fan are introduced. Secondly, the progress and controversy on the formation mechanism, analysis methods and sedimentary models of fluvial fan are elaborated, and fluvial fan is compared with alluvial fan, river and lacustrine delta. Finally, ten identification signs of the fluvial fan are proposed. It is found through the study that development and scale of fluvial fan are affected by external factors such as climate, tectonic, provenance and wind field. The facies and lithofacies association inside the fan are controlled by the activity of the internal channel. It is pointed that fluvial fans are widely distributed in the world not only today but also in the geological history. The occurrence of fluvial fan will change the traditional continental deposition system dominated by alluvial fan-river-lacustrine. Meanwhile, the research of fluvial fan will be of great significance in the fields of sedimentology and oil and gas exploration.

Numerical simulation of fire smoke control methods in subway stations and collaborative control system for emergency rescue

As subway fires can easily cause numerous casualties, this paper proposes the idea of active disaster relief, which involves ventilation, exhaust, smoke blocking and exhaust, and other facilities coordinating centralised control to assist passenger evacuation and firefighting. The ventilation and smoke exhaust method used in multilayer crossing complex subways is analysed, and a typical interchange transfer station is selected to build a numerical model. The combined control of fire smoke is analysed based on six ventilation modes, and fire dynamics simulator software is used to perform several numerical simulations. According to the simulation results, ventilation and smoke control is used in the cases of fire on the second and third floor in the underground, the airflow speed of the stairway reached 2 m/s, which can completely restrain the smoke on the fire floor. According to the characteristics of different fire sources and smoke control scenarios, a remote monitoring model of multielement information fusion, such as ventilation path, fan characteristics, smoke exhaust channel, and smoke blocking facilities, is established, and a multielement disaster information-fusion-based collaborative centralised emergency rescue platform for subway fire disaster relief is developed. Real-time disaster analysis is performed, and intelligent control of airflow and smoke exhaust in the complex form of subway-controlled smoke turbulence field is developed to facilitate safe escape and efficient firefighting and rescue of people during emergencies.

Electronic Constant Twist Angle Control System Suitable for Torsional Vibration Tuning of Propulsion Systems

Currently, great emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional vibration is often ignored. This article deals with a semi-active torsional vibroisolation system using pneumatic flexible shaft coupling with constant twist angle control. This system is suitable, as it is specially designed, for the tuning of mechanical systems where the load torque has fan characteristics (fans, ship propellers, pumps). The main goal of this research is to verify the ability of an electronic control system developed by us to maintain the pre-set constant twist angle of the used pneumatic flexible shaft coupling during operation. The constant twist angle control function was tested on a laboratory torsional oscillating mechanical system. Presented results show that the proposed electronic control system meets the requirements for its function, namely that it can achieve, sufficiently accurately and quickly, the desired constant twist angle of the pneumatic flexible shaft coupling. It is possible to assume that the presented system will increase the technical level of the equipment where it will be applied.

Design of fault diagnosis algorithm for electric fan based on LSSVM and Kd-Tree

Currently, the complexity of mechanical equipment is increasing rapidly together with the poor working environment. If a fault occurs, how to find the fault in time becomes a poser. Motivated by this existing problem, based on the analysis of the fault characteristics of electric fans, a fault diagnosis algorithm model based on Least Square Support Vector Machine (LSSVM) and Kd-Tree was proposed. This algorithm was based on the LSSVM optimized by the Cuckoo Search (CS). This paper used the “one-to-many” principle and the sigma threshold method to introduce k-Nearest Neighbor (kNN) which was implemented by Kd-Tree as a secondary classifier to optimize the model. In data preprocessing, the data based on time series was first processed by Empirical Mode Decomposition (EMD) and the energy ratios were calculated, and the the above results were degraded by Principal Component Analysis (PCA) and normalized. On top of that, in case of the uncertain fault types, the Fuzzy C-Means clustering algorithm (FCM) optimized by Particle Swarm Optimization (PSO) was proposed to provide a priori knowledge for the model. In this paper, the algorithm model, FCM and other parts were verified to prove that the performance and generality of the algorithm were better than those of general classification algorithms, and relevant experiments were conducted for different data processing methods to expand the universality of the algorithm.

Numerical simulation on near-field aerodynamic noise of an adjustable-blade axial-flow fan

A numerical simulation method based on the Ffowcs-Williams and Hawkings model is employed to predict the mechanisms of the near-field aerodynamic noise distribution characteristics of an adjustable-blade axial-flow fan with different installation angles of moving blades (Δβ). The simulated results reveal that with Δβ changing from −12° to 12°, the changing curves of the maximum total sound pressure level (MTSPL) at the tip clearance region (A region), the leading edge region (B region), and the trailing edge region (C region) exhibit an apparently rising trend, which increase by 4.0 dB, 5.7 dB, and 4.3 dB, respectively. Besides, the MTSPL at the C region is always smaller than that at A and B regions within the studied installation angles. Additionally, the acoustic energy ratio (Cpi) is the ratio of the sound energy density of a certain frequency to the total sound energy density, which shows the various frequency distribution characteristics under studied angles. It is found that when Δβ deflects from −12° to 0°, Cp1 (the acoustic energy ratio at the low-frequency in the range of 20–500) decreases from 0.71 to 0.59, Cp2 (the acoustic energy ratio at the intermediate-frequency in the range of 500–2000) increases from 0.18 to 0.25, and Cp3 (the acoustic energy ratio at the high-frequency in the range of 2000–3000) rises from 0.1 to 0.16. This study derives the aerodynamic distribution characteristics of the TSPL and acoustic energy in the near field of moving blades, which reveals its changing rules and frequency distribution under various installation angles. The conclusions may provide guidance for the research regarding the technology of the noise control of the adjustable-blade axial-flow fan.

Flow and Noise Characteristics of Centrifugal Fan in Low Pressure Environment

The influence of low-pressure environment on centrifugal fan’s flow and noise characteristics was studied experimentally and numerically. A testbed was established to conduct the experimental test on the performance of a centrifugal fan, and the characteristic curve and power consumption curve of the fan under different pressure were obtained. Then the simulation model of the centrifugal fan was established, which was used to simulate the working process of centrifugal fan under different negative pressures. The results showed that the total pressure and static pressure of the fan decrease with the decrease of the ambient pressure. The total and static pressures of the fan under 60 kPa pressure condition decreased by 42.3% and 38.3%, respectively, compared with those of fan under the normal pressure. The main reason for this phenomenon is that the decrease of the environmental pressure leads to the decrease of air density. Besides, with the drop of environmental pressure, the sound pressure and sound power of the fan noise decreases.

Hurricane Deposits on Carbonate Platforms: A Case Study of Hurricane Irma Deposits on Little Ambergris Cay, Turks and Caicos Islands

AbstractThe study of modern hurricane deposits is useful in both identifying ancient hurricane deposits in the rock record and predicting patterns of deposition and erosion produced by future storm events. Hurricane deposits on carbonate platforms have been studied less frequently than have been those along continental coasts. Here we present observations of the characteristics of deposition and scour caused by Hurricane Irma on Little Ambergris Cay, a small uninhabited island located near the southeastern edge of the Caicos platform in the Turks and Caicos Islands. Hurricane Irma passed directly over Little Ambergris Cay on 7 September 2017 as a Category 5 hurricane. We described and sampled multiple types of hurricane deposits and determined that the washover fans were the best sedimentological records for hurricane conditions, as they were subject to very little reworking over time. We compared different model predictions of storm tide and wave height with eyewitness reports and distributions of scour. Examining the washover fans allowed for the construction of a conceptual model for hurricane deposits formed in a high‐energy storm event on a carbonate platform. Characteristics of the washover fans were their small size, the lack of sedimentary structures, and very well sorted sediment. The size and distribution of carbonate boulders eroded and transported by the storm are consistent with depth‐averaged flow velocities in the range of 1.5–5.3 m/s. The strength of the storm and the low‐lying topography, distinct features of a carbonate platform setting, contributed to high levels of sediment bypass and high flow velocities, resulting in small, unstructured deposits.

User comfort driven time-table linked AHU scheduling for ancillary service maximization of an educational building

Thermal energy dynamics of a large building can be turned up as a substantial source of ancillary service for the grid. This paper presents that how the potential of Air Handling Unit (AHU) of Heating Ventilation and Air Conditioning (HVAC) system can be utilized as a virtual source of an ancillary service by regulating it in real time according to its thermal load. Internet of Things (IoT) enabled real time controller is proposed where the thermal comfort of occupants is used as feedback to control the AHU fans. The key challenge corresponding to the AHU is, nonlinear torque characteristics of fan with respect to required air flow rate at a thermal load on AHU. To address this problem an Adaptive Neuro Fuzzy Inference System is used to model the nonlinear property of the AHU fan. In this system it has two-part integration, IoT based controller and ANFIS based model with thermal model of building. To evaluate the algorithm, first, the reserved ancillary potential is calculated based on weekly class schedule. Secondly, it has been controlled in real time as per the thermal comfort of occupants to maximize the potential of ancillary service through the HVAC system. To analyze the response of the algorithm for a building, this set-up is scaled up at the level of AHU network installed in the lecture hall complex of an educational building in Delhi. The proposed algorithm has been tested and analyzed on an experimental set-up, synchronized with the thermal-dynamic model of building in MATLAB. It shows that there is a potential of ancillary service up to 97 kW in non-scheduled period and for the scheduled period it can be increased by 20% to 59% of available reserve power.

Holocene alluvial fan evolution, Schmidt‐hammer exposure‐age dating and paraglacial debris floods in the SE Jostedalsbreen region, southern Norway

The evolution of several sub‐alpine alluvial fans SE of the Jostedalsbreen ice cap was investigated based on their geomorphology and Schmidt‐hammer exposure‐age dating (SHD) applied to 47 boulder deposits on the fan surfaces. A debris‐flood rather than debrisflow or water‐flow origin for the deposits was inferred from their morphology, consisting of low ridges with terminal splays up to 100 m wide without lateral levees. This was supported by fan, catchment, and boulder characteristics. SHD ages ranged from 9480±765 to 1955±810 years. The greatest number of boulder deposits, peak debris‐flood activity and maximum fan aggradation occurred between ̃9.0 and 8.0 ka, following regional deglaciation at ̃9.7 ka. The high debris concentrations necessary for debris floods were attributed to paraglacial processes enhanced by unstable till deposits on steep slopes within the catchments. From ̃8.0 ka, fan aggradation became progressively less as the catchment sediment sources tended towards exhaustion, precipitation decreased during the Holocene Thermal Maximum, and tree cover increased. After ̃4.0 ka, some areas of fan surfaces stabilized, while Late‐Holocene climatic deterioration led to renewed fan aggradation in response to the neoglacial growth of glaciers, culminating in the Little Ice Age. These changes are generalized within a conceptual model of alluvial fan evolution in this recently‐deglaciated mountain region and in glacierized catchments. This study highlights the potential importance of debris floods, of which relatively little is known, especially in the context of alluvial fan evolution.

A three-dimensional body-force model for nacelle-fan systems under inlet distortions

A steady-state three-dimensional body-force model is presented for nacelle-fan system modeling. The model is based on three-dimensional averaged governing equations that are rigorously derived from three-dimensional unsteady Reynolds-Averaged Navier–Stokes equations. The three-dimensional nature of the model provides intuitive advantages, in terms of both flow physics and implementations, in modeling inlet distortion problems. One application of this model is to predict the effects of the fan system under inlet distortion upon the upstream and downstream flow field of the fan system. This is particularly useful for nacelle designers. The proposed body force model is formulated and implemented without any knowledge of the fan blade geometry. Instead, fan performance data provided by engine suppliers are fed into the body force model to replicate/predict the fan characteristics and their interactions with the upstream flow field under inlet distortions. This approach is validated with inlet distortion data to demonstrate its capability in general off-design conditions.

Effects of Bionic Volute Tongue on Aerodynamic Performance and Noise Characteristics of Centrifugal Fan Used in the Air-conditioner

The aerodynamic noise generated by the centrifugal fan used in the air conditioner is related to the comfort of human living and working, which can be controlled by using the bionic design and optimization of key components of centrifugal fan. Inspired by the non-smooth leading edge of long-eared owl wing, eight kinds of volute tongues are proposed to reduce the aerodynamic noise of a centrifugal fan. The flow and sound characteristics are numerically investigated by incorporating computational fluid dynamics and computational aero-acoustics. The optimal result exhibits a noise reduction of up to 1.5 dB with a slight increase in mass flow rate. The acoustic characteristics, with respect to the sound pressure level, power spectral density, and sound directivity are discussed. The time-domain, frequency-domain, and root mean square values of pressure fluctuation are monitored and analyzed to assess the unsteady flow interaction between the volute tongue and impeller. The intensity and scale of vortices in the centrifugal fan are suppressed in the upstream and downstream of the bionic volute tongue, and the turbulence effect on the surface of the volute tongue becomes even and weak.

Noise characterization of automotive auxiliary fan drives

The demand for low-noise auxiliary drives has been increasing in the automotive industry, as the entire noise level within the vehicle interior has been continuously decreasing over the recent years. In contrast to “larger” drives, the fractional horsepower (FHP) auxiliary drives used here are not subject to any standards. They are customized solutions and hardly anything is reported on their noise and vibration characteristics. Furthermore, their design is very much cost-driven, and noise performance is mostly treated in a retrofit approach within the final system. This article determines the noise and vibration characteristics of FHP auxiliary fan drive systems as typical for use within LED headlights for thermal management. It provides tools for further systematic analysis and eventual mitigation of potentially disturbing noise of such drives already at the development stage.

The characteristics of a Finnish metal fan: Comparative study on music festival attendees

Metal is exceptionally popular and widely approved at all levels of Finnish society. But what are the Finnish metal fans like? Even though there are studies on how metal fans relate to the metal community and how they construct their identity, studies on metal festival audiences are scarce. Here, Finnish metal festival attendees are studied to find out how they differ from the participants of other popular music festivals in demographics, live music consumption and preferences in festival experiences. This is done using a mixed methods research approach. The most interesting finding concerns sex and self-perceived gender position. So far, female metal fans have been studied qualitatively, demonstrating how they represent and perceive themselves inside the male-dominant metal community. We present a new finding, using quantitative data, where both male and female metal fans consider themselves more masculine than the participants of other festivals. The importance of the community was confirmed. In a metal festival, there is a dual community effect: the festival community forms a temporary, open-minded enclave that is common for all the festivals. In a metal festival, the audience comprises also members of the more permanent metal community. A strong sense of community originates from the shared musical preference, demonstrated by a loyal festival attendance and a common symbol system. From the organizer’s point of view, metal festival fans are a grateful audience since they are loyal and earn more than other festival attendees, being willing to invest time and money for their fandom.

CORRIGENDUM: Experimental investigations on the performance and noise characteristics of a forward-curved fan with the stepped tongue

CORRIGENDUM: Experimental investigations on the performance and noise characteristics of a forward-curved fan with the stepped tongue

Predicting Fan Behavior Through Egocentric Network Analysis: Examining Season-Ticket Holder Renewal

The purpose of this study is to utilize egocentric network analysis to predict repurchase behaviors for college football season-ticket holders. Using a research approach grounded in network theory, we included the relational and behavioral characteristics of sport fans in a binomial regression model to predict renewal decisions among college football season-ticket holders. More specifically, we developed a model that incorporates the egocentric network variables, past behavior, and behavioral intentions to empirically test which consumer characteristics predict future behavior. Building on previous research emphasizing the role of socializing agents and social connections in sport fan consumption, through the use of egocentric network analysis, we examined the effects of social structure and social context on repurchasing decisions. Moreover, the present study is positioned within the larger discourse on season-ticket holders, as we aimed to add a network theory perspective to the existing research on season-ticket holder churn and renewal.