Centrifugal Fan Research Articles

Design of an instrumentation system for assessing the acoustic attenuation performance of ducted Helmholtz resonators in the presence of grazing flow

The Helmholtz resonator (HR) has been widely used as a duct silencer to reduce low-frequency noise. However, the presence of grazing flow could influence the noise attenuation performance of the HR in ductwork systems. This study aimed to design an instrumentation system for studying the acoustic attenuation performance of ducted HRs in the presence of grazing flow. The instrumentation system includes a centrifugal fan, diffusion section, anechoic termination, flow development section, test section, and sound source. In this study, a HR as a ducted silencer was installed in the test section of the instrumentation system. Transmission loss (TL) due to the HR insertion was measured in the presence of forward and reverse grazing flows. The results showed that the instrumentation system succeeded in assessing the noise attenuation performance of the HR under a high sound pressure level and different flow rates and directions.

SolidWorks Flow Simulation: Selecting the optimal mesh for conducting CFD analysis on a centrifugal fan

The accuracy of mesh use determines the suitability of simulation results with experimental test results, therefore it is necessary to study the type and number of mesh used for flow simulation. This study aims to investigate the type of mesh and the number of cells that are appropriately used in the simulation of centrifugal fans using the Solidworks Flow Simulation module. The research was conducted by comparing the simulation results with the experimental results on centrifugal fans that have been carried out by previous studies. In this research, the type of mesh used is global mesh. The parameter of determining the number of cells is done by varying the mesh level because the mesh level affects the number of cells. In this simulation study, the boundary condition is set to one flow volume of 5 m3/h and a rotation speed of 92.362 rad/s. In this study, the total pressure and efficiency of the centrifugal fan are the things that are seen from the comparison of flow simulation with the experiment. Based on the simulation results that have been carried out, mesh levels 1 to 4 show results that differ significantly from the experimental results. At machine levels 5 to 7, the results are close to the experimental results, but the closest total pressure and efficiency values are at mesh level 5. The results of this study can be a reference for research that simulates centrifugal fans.

Identification of unsteady effects in the flow through a centrifugal fan using CFD/CAA methods

Identification of unsteady effects in the flow through a centrifugal fan using CFD/CAA methods

Numerical Investigations and Artificial Neural Network-Based Performance Prediction of a Centrifugal Fan Having Innovative Hub Geometry Designs

It is a well-known fact that air approaches the eye region of the rotating impeller of a centrifugal fan with shock-less entry conditions in an ideal scenario. The flow in this region is associated with induced swirl losses, leading to cumulative performance losses. Proper flow guidance in the vicinity of the eye region is essential to minimize possible flow losses. The flow guiding structure may be in the form of a projection or extrusion connected to the rotating impeller of the turbo machines and is generally named a hub. These attachments enhance the overall flow augmentation of the turbo machines in terms of static pressure improvement by reducing a significant amount of inlet turning losses. This article attempts to highlight the efficacy of hubs of various shapes and sizes on the pressure rise of the centrifugal fan using Computational Fluid Dynamics (CFD). Simulation results revealed that the optimized hub configuration yields about an 8.4% higher head coefficient and 8.6% higher relative theoretical efficiency than that obtained for the hub-less base configuration. This improvement in these paraments therefore also commemorates the global progress in energy efficiency as per the UN’s Sustainable Development Goals, SDG 7 in particular. Simultaneously, in the Artificial Neural Network (ANN), a Multi-Layer Perceptron (MLP) model is used to forecast the performance of a centrifugal fan with an optimized hub design. The results predicted by the ANN model are found to be in close agreement with the optimized hub shape’s numerical results.

Fault Diagnosis of Centrifugal Fan Based on Grid Search Optimized Voting Weighted KNN

Fan plays the roles of the forced draft fan, induced draft fan, primary air fan, seal fan, and powder exhauster. As an important auxiliary of the fossil-fuel power station, its working environment is harsh. Timely and efficient fault diagnosis can effectively reduce equipment failure and shutdown losses, and improve the efficiency of thermal power generation. K-Nearest Neighbour (KNN) has good classification ability for non-stationary data samples. In response to the shortcomings of the traditional KNN algorithm, this paper constructs a fault diagnosis model based on the voting weighted k-nearest neighbor algorithm. The model constructs a weight voting equation that is negatively correlated with the distance value based on the first k-nearest neighbors and then conducts fault diagnosis based on the voting score. We use grid search to optimize the model and select the k value in the model, and the relationship between the k value and accuracy was verified. The grid search optimization voting weighted k-nearest neighbor is used to diagnose the faults of nine common operating states of centrifugal fans, and the diagnostic accuracy can reach 100%.

A Numerical Approach to the Design of a New Split-Type Diffuser in a Centrifugal Fan for Improved Performance

A Numerical Approach to the Design of a New Split-Type Diffuser in a Centrifugal Fan for Improved Performance

Research on operational characteristics of coal power centrifugal fans at off-design working conditions based on flap-angle adjustment

The coal power centrifugal fan (CF) is one of the most significant equipment in coal power plants, which usually works at off-design conditions according to the demand of electricity consumption. Consequently, the efficiency of CFs is far lower than the designed maximum efficiency under this condition, causing large amounts of potential energy wasted. A novel flap-angle adjustment (FAA) method is proposed to efficiently solve this problem in the CF system. This manuscript establishes a theoretical model of the flap-angle adjustable centrifugal fan (FAACF). The operating economy of FAACF at both design and off-design conditions is comprehensively studied. The internal flow mechanism of efficient operation is analyzed, which reveals the more stable flow state inside CF impellers at off-design conditions. By comparing with the traditional inlet guide vanes CF (IGVCF), the application of the FAA improves the energy efficiency of the CF system significantly. A wider high-efficiency range is obtained, which is superior to the IGVCF. The numerical results effectively reveal the mechanisms by which flow loss occurs in the FAACF at the outlet of blades. In particular, the energy-saving rate of the G4-73-11 type CF system based on the FAA can reach 20.4 % when the relative flow ratio decreases to 74 %, which proves the positive adjustment potential of energy efficiency and indicates great energy-saving benefits of the FAA application in the CF system.

Radial Centrifugal Fan Redesign and New Technologies Using CFD Applications

The purpose of this article is to redesign centrifugal radial fans used in HVAC installations, using the analysis of aerodynamic flows and velocities distributions in the fan. Numerical simulations based on the reference model from the Pumps and Fans laboratory were performed using the SolidWorks program, Flow Simulation module. Following the simulations, information regarding the fluid flow in the machine rotor and casing, the most suitable shape of the blades resulted, and redesign solutions through 3D printing technologies were proposed. Numerical simulations with Flow Simulation on three-dimensional models were carried out, for a better analysis of the volume of air passing through the fan, but also for the prediction of some negative effects: the appearance of vortices that lead to high noises/acoustic disturbances, the appearance of additional vibrations, but also sudden and uncontrolled variations in the pressure force. Following the numerical analysis, it was found that for the new blade profiles the velocities are uniform, which greatly reduces the noise and vibrations in the operation of the fan. The redesign also aims to reduce the energy consumption of these fans.

An Empirical noise model of centrifugal fans with different volute tongues based on Langevin regression

In the context of the rapidly evolving field of building ventilation, fan noise control stands out as a pivotal technology to enhance the quality of life. This study aimed to elucidate the inherent randomness, distinct characteristics, and potential low-dimensional noise structure essential for developing effective noise control methods. In this study, a stochastic dynamics model for the noise of centrifugal fans with various volute tongue structures is constructed using the Langevin regression method and experimental measurements. An empirical noise model capturing the peak characteristics of noise discrete tonal is developed through parametric mode expansion and an empirical mean-field model of turbulent wakes, facilitating accurate noise predictions. The research findings demonstrate the effectiveness of the Langevin equation employing the cubic Stuart-Landau equation and multiplicative noise to predict fan noise across different volute tongue structures. While stochastic dynamics models unavoidably lose the characteristic discrete noise peaks, predictions of the total A-weighted sound pressure level remain within a 2.2% error margin. The stochastic dynamics models applied to centrifugal fan aerodynamic noise and turbulent wakes exhibit striking resemblances, suggesting a fundamental connection between turbulence and noise generation. The extended empirical noise model maintains discrete pitch noise peaks by introducing shift modes, indicating that stronger Langevin deformations correspond to larger translational amplitudes of the shift modes. The advancement of stochastic dynamics and empirical noise models lays a foundational framework for the formulation of effective noise control strategies.

A vibro-acoustic signals hybrid fusion model for 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 vibro-acoustic signals hybrid fusion model (VAS-HFM) is proposed for blade crack detection of centrifugal fans. Firstly, the kernel cosine similarity is designed to exploit the nonlinear relationship between multi-source vibro-acoustic signals and complete the data-level fusion of homogeneous vibro-acoustic signals. Then, a one-dimensional feature pyramid network (1D-FPN) is proposed to extract the vibro-acoustic features and generate initial decisions. Finally, a basic probability assignment (BPA) acquisition method based on the precision of the initial classifiers and a weighted average method based on the Jousselme evidence distance (JED) are proposed to minimize the conflict between multi-source evidence, and the Dempster-Shafer theory of Evidence (DSE) method is used to obtain the blade crack detection results. The effectiveness of the proposed method is verified by two centrifugal fan blade crack detection experiments. Compared with other related methods, the proposed method has better detection performance and stronger robustness.

Design and characterization of a low-speed aeroacoustic wind-tunnel research facility at IIT Kanpur

This work presents the design and characterization of a state-of-the-art low-speed aeroacoustic wind-tunnel at Indian Institute of Technology Kanpur (IITK), which is a newly commissioned research facility for the experimental study of flow-induced noise generated from bodies placed in a flow field. This open-circuit, open-jet suction facility which is unique to IITK, is also the first aeroacoustic wind-tunnel in India. The facility is powered by large centrifugal fan of 75 KW rating which is controlled through a variable frequency drive. To achieve a low background noise, carefully designed parallel baffle mufflers (PBMs) are placed at the fan inlet and outlet. The inlet silencer is connected to lined diffuser and a bell-mouth collector which opens in a fully anechoic chamber made from metallic wedges, and its internal dimensions are 3.5 m × 3.5 m × 3 m. The chamber can provide a reflection-free environment beyond 250 Hz. A smooth contraction-nozzle of ratio 10:1 whose profile follows a fourth-order spline, and a settling-chamber with honeycombs and flow-screens is placed on the other side of the anechoic chamber. The test-section of size 600 mm × 600 mm is attached to the exit plane of the nozzle, and can provide flow speeds up to 45 m/s, where the maximum turbulence intensity was less than 1%.

Performance study of 1.5 kWe free piston Stirling generator emulating solar power working conditions

In this paper, solar irradiance, ambient wind speed and power load are emulated by regulating the electric heating power, the centrifugal fan speed and the load resistance to emulate the operation condition of the solar dish Stirling power generation (SDS) system. The couple effects on the generated power and thermoelectric efficiency of a free piston Stirling generator (FPSG) prototype are tested experimentally. The heat dissipation characteristics of the outer wall is analyzed. The results show that in certain start-up condition the generated power drops rapidly from 180.8 W to the lowest point of 77.1 W at 36 s, then rise gradually and stabilize at 12 min. The generated power is approximately positively linear with the heating power while the thermoelectric efficiency rises firstly followed by decline, with a peak of 20.3% at 5 kW. The wind speed reduces the generated power, thermoelectric efficiency and radiation loss, but increases the convection loss. The generated power and thermoelectric efficiency decrease with the load resistance, with the maximum values of 1364.6 W and 23.3% respectively.

Dynamical Modelling of a Centrifugal Fan Driven by an Induction Motor and Experimental Validation

The application of electrical drives in the control of centrifugal fans and pumps is a well-established area that leads to substantial energy savings. It requires electrical and automation engineers to have some knowledge relevant to drives about fan and pump modelling since ignoring or oversimplifying fan/pump modelling for the intended drive design compromises the required control quality. This paper improves the existing dynamical models of fans and pumps integrated with induction motors via neural network estimation of overall fan/pump efficiency; this estimation is based on the voltage frequency of the driving induction motor, pressure, and flow rate, followed by the separation of the fan’s or pump’s own efficiency for the motor load torque computation, enhancing the accuracy due to the correct reflection of the power balance. The model is developed with a view to being convenient for control design applications. For the first time for dynamical models, it is verified experimentally, justifying the necessity of the first-order nonlinear differential equation for the flow rate. The validation includes a direct approach based on analysis of transient behaviour caused by a small-step perturbation of the frequency of the motor voltages and an indirect approach based on the introduced concept of the dynamical flow rate and pressure estimators.

Simulation and Experimental Study on Vibrating Screen-Type Grain-Recovery Device with Upper Centrifugal Fan

To solve the problem of grain loss caused by nibbling during the working process of the maize ear and stem harvesting machine, a vibrating screen-type grain-recovery device with an upper centrifugal fan was designed. The device mainly consists of a centrifugal fan and vibrating screen. The work process of the grain-recovery device is theoretically analyzed, and it is clarified that the turning of the bracts is the key to separating the bracts from the grains, and the design criteria of the vibrating screen are obtained. The CFD–EDEM coupled single-factor simulation experiment was carried out on the size of the vibrating screen sieve hole and the number of draft bars, and the motion posture of the bracts was simulated. Based on the previous CFD–EDEM coupled simulation study, the orthogonal experiment was carried out on the fan speed, vibration screen drive-shaft speed, and operation speed of the grain-recovery device. The orthogonal experimental results show that, when the fan speed is 1000 r/min, the vibration screen drive-shaft speed is 300 r/min, and the operation speed is 3.62 km/h, the performance of the grain-recovery device reaches the optimum level, and the grain recovery rate is approximately 85%.

Noise Optimization and Experimental Verification of Voluteless Centrifugal Fan

Noise Optimization and Experimental Verification of Voluteless Centrifugal Fan

Experimental Investigation on Performance of Counter-rotating Impulse Turbine with Middle Vanes for Wave Energy Conversion

In an oscillating water column (OWC) based wave energy device, a water column that oscillates due to the sea wave motion generates a bi-directional airflow in an air chamber, and finally, air turbine driven by the bi-directional airflow converts the pneumatic energy into the mechanical energy. A counter-rotating impulse turbine for bi-directional airflow has been proposed by M. E. McCormick of the United States Naval Academy in 1978. In previous studies by using CFD analysis, the authors investigated the effect of the turbine geometry on the performance of the counter-rotating impulse turbine for bi-directional airflow, and it was clarified that the efficiency of the turbine is higher than that of an impulse turbine with a single rotor for bi-directional airflow in a range of high flow coefficient.On the other hand, this impulse turbine has a disadvantage that the efficiency in a range of low flow coefficient is remarkably low due to the deterioration of the flow between the two rotors. In a previous study, the authros proposed to installed middle vanes between the two rotors in order to overcome the above drawback. And the effect of the middle vanes the turbine performance was investigated by CFD analysis. As a result, it was found that the middle vanes installed to the turbine rectify the flow between the rotors in a range of low flow coefficient and it drastically increases the efficiency.In this study, the middle vanes was actually installed in the counter-rotating impulse turbine for bi-directional airflow, and its performance was elucidated by wind tunnel tests which has the turbine with a inner diameter of 240 mm and a centrifugal fan. It was found from the experiment result that the turbine performance at low flow coefficient is improved and the peak efficiency increases by 1.14 times, by means of the installation of middle vanes to the turbine.

Influence of the Spatial Position of the Semi-open Impeller on the Internal Flow Field in Centrifugal Fans

This paper takes as its background the study of centrifugal fans in powered air-purifying respirators. To improve the efficiency of the centrifugal fan and the uniformity of the internal flow field, a steady-state simulation based on the realizable k-ε turbulence model, using the “frozen rotor method”, was carried out to analyze the effect of the spatial position of the impeller in the centrifugal fan on the internal flow field by matching the impeller to the worm gear. The results show that varying the eccentric angle, eccentric distance, and longitudinal depth of the semi-open impeller in the volute affects the internal flow field of the centrifugal fan to varying degrees. The concentric arrangement was not found to be optimal, and when the impeller rotates slightly further away from the worm tongue, the flow field inside the centrifugal fan is more uniform and the phenomena such as “wake-jet” and boundary layer separation are significantly reduced. In addition, it was found that the pressure distribution at the inlet is approximately the same as the pressure distribution in the flow field.

NUMERICAL SIMULATION OF THE DRYING PROCESS BY ACTIVE VENTILATION OF THE PRODUCTS OF FRACTIONAL PROCESSING OF LEGUMES IN A CONVECTIVE BELT DRYER

The process of removing moisture from vegetable agricultural raw materials is a diverse, but energy-consuming stage of production, regardless of the applied methods and methods of drying. For forecasting energy consumption and designing drying equipment, analysis and generalization of the kinetics and dynamics of drying of plant raw materials is an urgent task. Based on the results of the conducted research, the technological and constructive-technological scheme of the convective belt dryer for the fractional processing of leguminous herbs was theoretically justified. The dryer is made in the form of a chamber with horizontal belt conveyors, in the middle of which there are heaters with heated steam, and in the upper part of the chamber there are centrifugal fans. With the help of the Simcenter STAR-CCM+ software package, a simulation of the technological process of drying in the developed dryer was carried out. Visualizations of the particle flow velocity distribution of products of fractional processing of legumes and air flow in the area of the convective belt dryer in the form of scalar and vector data were obtained. The temperature distribution of the air flow in the area of the convective belt dryer was also determined in a scalar form, which made it possible to detect its influence on the temperature of the alfalfa particles moving along the belt conveyors. The obtained results of numerical modeling confirmed the analytical calculations. However, for a more complete evaluation and optimization of dryer parameters, it is recommended to conduct additional experimental studies of the drying process of products of fractional processing of leguminous herbs and empirically check the rational structural and technological parameters of the convective belt dryer.

A Bearing Fault Diagnosis Method Based on Improved Mutual Dimensionless and Deep Learning

Under nonlinear and non-stationary dynamic conditions, the fault diagnosis methods based on multi-dimensional dimensionless indicators (MDI) often cannot provide effective and accurate health monitoring in the fault diagnosis of petrochemical units. In view of the above problems, this paper preprocesses the dynamic signal and reconstructs a new dimensionless indicator. The indicator combines Complementary Ensemble Empirical Mode Decomposition (CEEMD) with MDI, named as Complementary Ensemble multi-dimensionless indicators (CEMDI). By using the sequential mapping method, the CEMDI processed data can be converted into gramian angular fields (GAF). In processing sparse data, the advantages of convolutional neural networks (CNNs) were used to identify different fault types. The method is validated using three datasets, motor bearing data provided by the Case Western Reserve University, multistage centrifugal fan data and machinery failure prevention technology challenge data. Compared with the traditional dimensionless index method and the latest published dimensionless methods in the literature, the fault diagnosis methods based on CEMDI and CNN exhibits good performance in identifying fault types under different conditions, which verifies its effectiveness and superiority.

Orthogonal optimization design of a Sirocco fan and numerical analysis on the internal flow characteristics

The forward-curved multi-blade centrifugal fan, also termed as Sirocco fan, is characterized by its complex characteristics of internal flow within the impeller and volute. Currently most of the fans are designed with modifications or optimizations for certain geometric parameters which could not ensure the well compatibility of flow in the impeller and volute, thus it is difficult to improve the aerodynamic performances of the fans. In this paper, we performed a multi-parameter design of a Sirocco fan with optimizations on the geometric parameters of the impeller and volute. The geometric parameters of the volute were designed based on analysis of the internal flow patterns, and the influence from the impeller is also considered. Optimization on the geometric parameters was carried out using the steepest descent method to improve the static pressure rise and efficiency under the designed flow rate by taking into account the relevance of flow in the impeller and volute. The effect of the parametric optimization is evaluated and analyzed by large-eddy simulation (LES). It was found that the static pressure rise and efficiency of the optimized model increase by 1.8% and 5.0% compared with the baseline model, respectively. The static pressure rise fluctuates in a regularly periodic manner. The optimized model reduces the area of low-pressure recirculating flow at the center of the fan and the separated flow on the suction surface of the blades. The near-wall flow on the volute surface is more stable, and the pressure fluctuation around the volute tongue is reduced. The outflow of the volute exhibits better uniformity than the baseline model.