Number Of Fan Blades Research Articles

Resonance analysis of fan blade design using Finite Element Method

Fan motors move liquids, such as air, in the gas phase from one place to another. The frequency of the fan blades, which are the main components of the fan motor, can vary. It is crucial to know the frequencies of each fan blade to avoid design failures caused by resonance. This research analyzes the effect of differences in the angle and number of blades on the natural frequency of the fan to avoid resonance with the motor rotation frequency. Modeling and simulation using the finite element method in the Solidworks application are used to determine the natural frequencies of the fan. Fans come in various configurations, with blades ranging from two to four, and blade pitch can be 25°, 30°, or 40°. Variations in the number of fan blades and changes in blade pitch show that the low mode shape does not affect the natural frequency, while the high mode has a negligible effect. The natural frequency of fan blades 2, 3, and 4 exhibits variations when operated with motors running at 25, 35, or 50 Hz. The findings imply that the fan blades' inherent frequency does not align closely with the motor rotational frequency, indicating that the design is safe.

Turbofan and turbojet engines: Working process and future development

This article is based on the fundamental thermodynamics theory to analyze the difference between the turbojet and turbofan engines. The result of this article is that the turbofan engine is suitable for commercial use since it consumes less fuel and has a higher bypass ratio than the turbojet engine. But low bypass ratio engines can serve the military since they have a smaller volume and higher speed, suitable for air combat. The turbojet engine can travel at a supersonic speed since it has extremely high jet flow from the nozzle and much higher fuel consumption, so it is for military use. This article also analyses two cases: i) How the number of fan blades and outlet guide vans affects the noise of the engine produced. ii) When airplanes fly through volcanic ash, how does the ash damage the airplane and the engine? The engineer found that 55 outlet guide vans are better than 37. To prevent airplanes from flying through volcanic ash, satellite weather photos start to show the volcanic ash area.

Reduced-order model and attractor identification for large eddy simulation of squirrel cage fan

A large eddy simulation (LES) of a squirrel cage fan (SCF) provides a precise representation of turbulent flows with different degrees of complexity. This study comprehensively analyzes the coherent structures of turbulent flows in an SCF using an LES, proper orthogonal decomposition (POD), dynamic mode decomposition (DMD), and multi-resolution dynamic mode decomposition (mrDMD). An intelligent reduced-order model is established by integrating hierarchical deep learning and the sparse identification of nonlinear dynamics. The result shows that the evolution of the global DMD modes is attenuated due to the spatial distribution variations of localized high-frequency mrDMD modes, along with the fragmented and non-steady development of modal patterns. Unlike POD, DMD quantifies the quality of the impeller inlet environment and captures the antisymmetric low-dimensional flows associated with the shedding of rotating vortex structures. The interaction strength between stationary and dynamic rotating areas is accurately represented by attractors characterized by petal-like structures. The trajectory of the attractors faithfully maps the antisymmetric structural attributes, quasi-periodic behavior, and gradual attenuation characteristics exhibited by DMD modes. The number of petal-like systems and their temporal oscillations are in good agreement with the number of fan blades and their rotational cycles. This study provides new insight into fan engineering to advance flow control strategies and improve the understanding of the underlying flow mechanisms.

Broadband noise characteristics of fans with different blades under identical working conditions

Small axis-flow fans are widely used for air cooling and ventilation systems. A common small axis-flow fan has an unshrouded rotor, structs or stator vanes and a round casing. The fans used in this work are designed based on isolated-airfoil blade design mode and simple radial equilibrium theory supplemented by three-dimensional flow simulations with steady flow. The noise radiated from the fan can be decomposed to discrete tones and broadband noise, which is mainly due to interaction between blades and structs or stators vanes and turbulence, respectively. Under the working conditions of the same pressure rise and volume flow rate, the noise spectra from different fans are analyzed. It is found that with the addition of the fan blade number, the concentration of the broadband sound energy gradually shifts from low frequency to high frequency. And the fewer the number of blades, the less the corresponding total broadband energy. Besides, the calculation results also show the fan with more blades can be absorbed more sound by the same sound absorption materials with the same volume. The findings are useful for improving the acoustic design of small axis-flow fans.

Small samples noise prediction of train electric traction system fan based on a multiple regression-fuzzy neural network

The fan noise in the train electric traction system contributes to the main noise of the train, affecting the comfort of the passengers. The prediction of fan noise can serve as a foundation for the design and fault diagnosis of the fan in the train electric traction system as well as noise reduction. This paper proposes a prediction model based on multiple regression analysis and a double-layer fuzzy neural network (MRA-2LFNN). After the multiple regression analysis of the train electric traction system fan noise is performed to determine the prediction input, a fuzzy neural network is used to predict the fan noise. Afterward, further analysis of noise influencing factors is presented based on the experimental results, and the possibility of the fan optimal design is discussed. This method can make accurate predictions using a small sample of fan noise data, reducing the need for data samples and lowering costs. The experimental results show that the proposed method can achieve better prediction results using the small sample dataset by training and verifying the actual train electric traction system fan noise data, and the average prediction accuracy rate is 94.15%, After discussion, when the number of fan blades is 16, the train electric traction system exhibits improved noise performance.

气力输送式排种器流场模拟与气流分配室结构设计

The pneumatic conveying metering technology is used to enhance the filling and clearing capacity of the seed metering device by forming a rotary air flow field inside the airflow distribution. The simulation test results show that the increase of the number of fan blades, the velocity of flow field at different outlets of the seed cleaning area decreases linearly, but the average velocity basically remains unchanged. The flow field velocity in the seed filling area decreased significantly with the increase of fan angle, and the difference between seed filling area and clearing area remains unchanged. When the blade angles in the filling area are the same, the fan blades size has no effect in flow field velocity.

Design and performance study of a rotating piezoelectric wind energy harvesting device with wind turbine structure

This paper proposes a rotating piezoelectric ambient wind energy harvesting device with wind turbine structure (R-PWEH), which mainly consists of wind turbine, support structure, excitation module, and power generation unit. This paper mainly investigates the effect of wind turbines with a different number of fan blades and units with different shapes of power generation on the performance output of R-PWEH. A series of experimental studies were conducted on the R-PWEH in the wind speed range of 0–20 m/s. In the experimental study at a wind speed of 16 m/s, the maximum voltage output of the R-PWEH was 114.24 V when the wind turbine with 11 fan blades and the rectangular cantilever beam power generation unit was installed. The optimal external load at this point is 8 kΩ and the maximum output power is 36.89 mW. The fastest charging rate for the capacitor at this parameter allows for easy powering of multiple light-emitting diodes for illumination. It has good prospects for development in practical applications, such as the ability to power micro and small sensors.

ВПЛИВ ГУСТОТИ РЕШІТКИ НА АЕРОДИНАМІЧНУ НАВАНТАЖЕНІСТЬ РОБОЧОГО КОЛЕСА ОСЬОВОГО ВЕНТИЛЯТОРА

The main requirements that apply to axial fans and axial compressors of aircraft gas turbine engines include minimum dimensions and weight; high aerodynamic load; high coefficient of performance; wide range of steady work; high reliability. For gas turbine engines, the requirements of minimum weight and dimensions are especially important, since the engines must provide flights at high velocities and altitudes. This study aims to assess the effect of the solidity of the impeller fan on the average radius on the aerodynamic loading of the impeller of an axial fan for an engine with a high bypass ratio. The object of the study is the impeller of the fan. The solidity of the impeller fan on the average radius varied in the range from 1.8 to 0.82, the number of blades of the impeller fan varied from 33 to 15, respectively. The studies in this work were carried out by the method of numerical experiment. The flow in the axial fans was simulated by solving the system of Navier-Stokes equations, which were closed by the SST turbulent viscosity model. Based on the analysis of the results of the study, an assessment is made of the influence of the solidity of the impeller fan at an average radius on the aerodynamic loading of the impeller of an axial fan for an engine with a high bypass ratio. The research results showed that with a decrease in the solidity of the impeller fan at an average radius of 1.8 to 0.82 in operating modes with an axial inlet velocity of 80 to 120 m / s, the impeller fan pressure ratio decreases by 0.11 ... 3.2 %. The maximum decrease in the fan pressure ratio increase for the fan impeller with the parameters studied is 3.2 %, with a decrease in the number of fan blades from 33 to 15, while the total weight of the blades decreases by 54.55 %. The decrease in the solidity on the average radius of the impeller of the studied fan leads to a decrease in the relative sizes of the low-velocity zones at the sleeve and on the periphery and to a decrease in the level of flow unevenness. A further reduction in the level of flow non-uniformity behind the fan is possible when using the boundary layer control in the fan - this is the task of subsequent studies.

Successive Aeroacoustic Transfer of Leading Edge Serrations From Single Airfoil to Low-Pressure Fan Application

Abstract Leading edge serrations are identified as an effective passive treatment for reducing fan broadband noise due to high turbulent inflow conditions. This paper aims to investigate the isolated effect of serrated applications in a rotating frame, covering the aerodynamic and aeroacoustic performance. With this purpose, a serration design, previously analyzed in the rigid domain, is transferred to the rotating frame, following a successive approach in form of a continuous increase of the fan blade number. This is considered as a feasible way to isolate the serration effects and to provide information on fan blade interaction and possible masking effects. Comparing blades with straight and serrated leading edges by analyzing the spectral noise reduction and the overall level result in deep insights in the underlying noise reduction mechanisms. Furthermore, analysis of phase differences by means of the wall pressure fluctuations leads to the identification of rotating flow phenomena, nonsynchronized with the rotor speed. The results obtained indicate an efficient noise reduction by the serrations in the vicinity of the design point. By use of the presented successive approach, noise reduction phenomena observed with the full rotor could be identified to be of either aeroacoustic or aerodynamic nature. A reduced noise is observed for the full rotor case, showing a reduction of blade interaction effects. At reducing flow coefficients, an improved stall margin of the serrated rotor is identified that also affects the aeroacoustic signature.

Erosion of an Axial Transonic Fan due to Dust Ingestion

This paper deals with the prediction of the particle dynamic and erosion characteristics due to dust ingestion in an axial flow fan, installed in a high bypass-ratio turbofan engine that operates in a dusty environment. Dynamic behavior comprises the particle trajectory and its impact velocity and location. While the erosion characteristics are resembled by the impact frequency, erosion rate, erosion parameter and the penetration rate. The study was carried out in two flight regimes, namely, takeoff, where the sand particles are prevailing, and cruise, where the fly ashes are dominated. In both cases, the effect of the particle size on its trajectory, impact location, and the erosion characteristics was studied. To simulate the problem in a more realistic manner, a Rosin Rambler particle diameter distribution was assumed at takeoff and cruise conditions. At takeoff, this distribution varies from 50 to 300 μm with a mean diameter of 150 μm sand particles. While at cruise, this distribution varies from 5 to 30 μm with a mean diameter of 15 μm fly ash particles. The computational domain employed was a periodic sector through both the fan and its intake bounding an angle of (360/38) where the number of fan blades is (38). The intake is a stationary domain while the fan is a rotating one and the FLUENT solver is used to solve this problem. Firstly, the flow field was solved in the computational domain using the Navier-Stokes finite- volume supported by the Spalart-Allmaras turbulence model. The governing equations, representing the particle motion through the moving stream of a compressible flow are introduced herein to calculate the particle trajectory. The solution of these equations is carried out based on the Lagrangian approach. Next, empirical equations representing the particle impact characteristics with the walls are introduced to calculate the rebound velocity, the erosion rate, erosion parameter, impact frequency and penetration rate. Moreover, a method to smoothen the irregularity in the calculated scattered data was discussed as well. During takeoff flight regime, the pressure side of fan blade experienced higher particle impact and erosion damage. The highest erosion rate was found at the corner formed by blade tip and trailing edge of pressure side. During cruise conditions, less erosion rates resulted. Maximum erosion rates are found at the leading edge of the pressure side.

Development of Electric Fan propeller Featuring Chestnut Tiger Butterfly Wing Characteristics

Sharp Corporation has been developing high-performance electric fans by applying the characteristics of wings of living creatures. This paper describes an electric fan having a propeller that mimics the shape of the wings of a Chestnut Tiger butterfly. Most electric fans generate a nonuniformly distributed wind velocity, which cause an uncomfortable feeling for the user. If the number of fan blades was increased, the wind generated would be smoother; however, the efficiency of the propeller itself would decrease. To solve these problems, we have modeled prototype electric fan propeller blades based on the shape of a Chestnut Tiger butterfly wing.

Improvement of a feed grain crusher operation

Constructional and technological configuration of a sieve-free feed grain crusher equipped with a pneumatic loading of material is suggested. Optimal diameter of limiting ring, area of annular gap between crushing chamber and disk of the rotor wheel and also number of fan blades are described.

Effect of Blade Numbers on Aerodynamic Performance and Noise of Small Axial Flow Fan

To more fully explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, some solutions are adopted to obtain the parameters’ distribution of the flow field.Firstly, the standard k-ε turbulence model is used to calculate the steady flow field of six different fan blades(such as 5,7,9,11,13,15) , and the SIMPLE algorithm is applied to couple vecolity and pressure. Secondly, the large eddy simulation in conjunction with the FH-W noise model are used to compute the unsteady flow field and noise. Finally, the experimental results verify that the calculation methods of steady flow field and unsteady flow field are correct. The conclusions show: (1)Total pressure and efficiency generally maintain the trend of firstly increasing and then decreasing with increasing the blade numbers, and it is the greatest when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With the increasing blades, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is firstly decreasing and then increasing before decreasing again 1 meter away from the central axis of the impeller along the outlet. When fan blade number is 11, overall sound pressure level of the aerodynamic noise is the greatest.

English

Subsonic wind tunnels are generally aerodynamic equipment allowing to obtain in one of their elements, namely in the experimental area where the model is placed, a uniform and stable airflow of determined speed. Wind tunnels of low subsonic speed, usually with continuous running, are plants where the air, driven by a fan, reach in the experimental area speeds up to 180 m/s (M <0,5). They look like tubes with (convergent - divergent) variable section. In our case the wind tunnel is a Prandtl type closed circuit in a horizontal plane, with a single return circuit and closed testing room. To reduce turbulence in the wind tunnel, the number of fan blades whose peripheral speed should not exceed 200 m/s should be as large as possible (which is the case of the INCAS subsonic wind tunnel with 12 blades). The present article is focused on the following topics: vertical and horizontal deflection and turbulence in the experimental area.

Fan impeller for electrical machines

The invention relates to a fan impeller (11) for electrical machines, in particular for alternators of motor vehicles. Said impeller comprises a fan plate (10), which has a number of fan blades (13, 18) arranged in a circle around the circumference of the front face that faces axially towards the exterior, said blades protruding in an axial direction from the fan plate in such a way that cooling air can be taken in axially below the fan blades and can be blown through the air channels (20, 21) formed between said blades radially towards the exterior. Only one respective part (18) of the fan blades is connected to the fan plate (10) in a fixed manner by means of a radial outlying end section (18a), so that the respective innerlying end section (18b) is pivoted progressively outwards, as the speed increases, by a centrifugal force (22) generated in this area, in order to reduce the cooling air flow. To minimise the flow noise, in addition to adapting the quantity of cooling air, dependent on the speed, to the cooling requirements of the machine, preferably only every second fan blade (18) is provided with an innerlying end section (18b) that can be pivoted outwards by centrifugal force (22), whereas the entire length of the remaining first neighbouring fan blades (13) is rigid and fixed to the fan plate (10).

1514 全閉外扇形モータのファン騒音に関する共鳴音解析(J11-3 ファン騒音,J11 流体関連の騒音と振動)

In recent years, with the rise of interest in environmental problems, noise reduction in motors has become a strigent requirement There are three kinds of motor acoustic noise: ventilation noise, electromagnetic noise and machine noise. It is assumed that ventilation noise in high speed machines consists mostly of fan noise. Fan noise, depends on the number of rotations and the number of fan blades and by the turbulence sound produced by the disturbed flow of cooling air. Many studies have been done on reduction of fan blade and turbulence noise by flow analysis based on fan blade number and shape. However, there have been no papers describing the space resonance frequency of the fan space, which is a propagation channel of the fan noise. Thus, in this paper, the space resonance frequency and resonance mode of the fan channel analyzed by Helmholts theory and experiments. The effect of rotational sound and resonance mode on noise is also described.

Active fan blade noise cancellation system

An active noise cancellation device and method for reducing fan blade noise over a broad spatial area. The device comprises a microphone, a band pass filter, and audio amplifier, and a speaker array. The microphone captures the sound produced by the fan and converts it into an electrical signal. This electrical signal is input to the band pass filter which has a center frequency equal to product of fan speed and the number of fan blades which comprise the fan. The band pass filter attenuates any signals other than the primary harmonic sound produced by the rotating fan blades. The filtered signal from the band pass filter is input to the audio amplifier. The audio amplifier conditions the signal for input to the speaker array. Accordingly, each speaker in the array receives and outputs an audio signal of equal amplitude and phase as that produced by the rotating fan blades. The speaker array is mounted on or close to the fan hub in a symmetric pattern commensurate with the fan blade geometry. In general, the number of speakers which comprise the array corresponds to the number of fan blades. The position of the speaker array is adjusted until a maximum destructive interference occurs between the sound produced by the rotating fan blades and the speaker array. With the addition of a phase shifter, the active noise cancellation device can be utilized to provide noise cancellation for variable speed fans.

Efficient sound generation in a ducted axial fan due to a rotating wavelike flow pattern

Previous investigations have shown the presence of narrow-band peaks in the acoustic spectra of ducted axial fans at frequencies other than harmonics of the blade passage frequency. This phenomenon is of practical importance because these peaks are strongest when the fan is operating near its best efficiency point. Measurements of the fan flowfield were conducted in the rotating frame using hot-wires and surface-mounted hot-film sensors in order to identify the source of the narrow-band tones. These measurements have shown a rotating wavelike motion composed of several discrete modes. The wave pattern was strongest on the pressure side of the blade in the region between the tip and the midspan. One of the modes of the rotating pattern was found to be an integer multiple of the number of fan blades, resulting in efficient sound generation at that frequency. a)Present address: Acoustics Technology, McDonnell Douglas Aerospace, Mail Code 71-35, 1510 Hughes Way, Long Beach, CA 90810-1864.