Fan Efficiency Research Articles

Numerical and experimental investigation into effects of winglet shape on flow and noise performances of axial-flow fans for outdoor unit of air conditioner

In this study, the effects of winglet shape on the flow performance, efficiency, and aerodynamic noise of axial-flow fans, used as cooling fans in an outdoor unit of split-type air-conditioners, are numerically and experimentally investigated. Especially, a focus is placed on the coherent flow structures of the tip and leakage vortices: the former is generated from the fan blade tip near the leading edge, and the latter forms in the gap between the blade tip and the shroud. Two types of axial-flow fans are considered: one is with a blade-tip winglet, and the other is without the blade-tip winglet. The flow fields around the fans are simulated by numerically solving the three-dimensional unsteady incompressible RANS equations, and the radiated acoustic pressure is predicted using the Ffowcs-Williams and Hawkings equation. The validity of the numerical methods is confirmed through the predicted results with the measured ones. The flow field characteristics driven by the fans with and without the winglet are analyzed by comparing the detailed structure of the tip and leakage vortices in the gap flow region. In addition, the flow performance, efficiency, and sound pressure of the axial fans are characterized in association with the vortex structures. These results reveal that the winglet shape in the gap flow region has an adverse effect on the flow and acoustic performances of axial-flow fans by increasing the gap-vortex strength.

Effects of Tip Clearance and Impeller Eccentricity on the Aerodynamic Performance of Mixed Flow Fan

The tip clearance and eccentricity of the impeller will affect the aerodynamic performance of the fan, and the impeller installation and vibration characteristics are relatively highly required if the tip clearance is too small. A reasonable tip clearance and excellent coaxially are necessary to ensure that the impeller does not rub with the shell and has superior aerodynamic performance when the fan is working. In the current study, a mixed flow fan was taken as the object and experimental explorations were performed on the C-type test rig designed according to GB/T1236 2000 Industrial fans-performance testing using standardized airways. By moving the airways to change the tip clearance, it was found that an overlarge tip clearance made the fan efficiency decrease significantly, and the efficiency change gradient was large. However, the gradient of efficiency change became smaller when reaching a certain clearance. Similarly, as the eccentricity became larger, the efficiency also decreased. To explore the influence of the optimal clearance and eccentricity of the fan on the fan’s performance, numerical simulations of the flow field inside the fan were carried out using FLUENT software corresponding to the experimental conditions. The influence of the tip clearance and eccentricity on the aerodynamic performance of the fan was revealed from the energy leakage perspective. Through theoretical and experimental analysis, we try to provide guidance on the design, installation and commissioning of fan tip clearance.

Study of the Blade Shape Impact on the Improvement of Fan Efficiency Based on State-of-the-Art Prototyping Methods

The article discusses the process of designing and testing as well as their results, carried out in order to increase the efficiency of axial fans, implemented as part of the European project INESI. Modifications of existing solutions based on rapid prototyping methods were presented. Scanning, FEM and CFD numerical calculations and 3D printing were used for that purpose. Rapid prototyping involved the use of a steel blade base and 3D-printed complex aerodynamic shapes that were bonded to create completely new blades. After their installation on the new rotor, enabling the angle of attack adjusting, a number of verifying tests of the fan were carried out. The solution was successfully tested and the results are discussed in the article.

Energy Conservation through BLDC Motor Ceiling Fan in Saranathan College of Engineering: Case Study and Recommendations

Ceiling fans constitute a significant portion of home power consumption, especially in warm-climate developing nations. This research explores a range of solutions to enhance the efficiency of ceiling fans and assesses the global potential for power savings and greenhouse gas (GHG) emission reductions. Leveraging commercially available technologies, it is feasible to achieve a remarkable 60% increase in ceiling fan efficiency. By implementing these efficiency upgrades in all ceiling fans sold by 2025, an impressive 80 TWh/year of electricity could be conserved, leading to the avoidance of 30 million metric tonnes of Carbon Di-oxide emissions worldwide. Additionally, this study investigates the effectiveness of policies and programs such as energy efficiency standards, consumer labelling, and financial incentives in expediting the adoption of energy-efficient ceiling fans. Furthermore, we delve into the advantages of integrating Brushless DC Motors (BLDC) in ceiling fans, where the linear relationships between current-to-torque and voltage-to-rpm offer enhanced energy conservation prospects.

Low pressure centrifugal fans operating with different air temperatures

For normal operating conditions of the centrifugal fan, the manufacturers provide operating curves (total pressure of the fan, static pressure of the fan, power, and efficiency) for standard air conditions. However, when a fan operates with air at different, usually elevated temperatures, their operating curves can significantly differ. As a result, the fan efficiency decreases, and the energy efficiency of the fan may be reduced. Fan operation in such air conditions also affects its acoustic characteristics. This paper investigates two types of centrifugal fans: with forward curved and backward inclined blades. The main goal was to determine how their operating and acoustic characteristics change with the change in air temperature. For this analysis, low pressure centrifugal fans are used, for which we already had measured operating and acoustic characteristics. The influence of the type of impeller and the curvature of the blades play an important role in the operation of the fan. For numerical investigation, ANSYS CFX software was used, and obtained results show excellent agreement with experimental measurements.

Numerical flow noise simulation of an axial fan with a Lattice-Boltzmann solver

In this paper, a transient and compressible solver based on the Lattice-Boltzmann Method/Very Large Eddy Simulation (LBM/VLES) approach is employed to predict unsteady flow physics and flow-induced noise generation of a low-pressure axial fan. Aerodynamic and aeroacoustic measurements provided by the European Acoustics Association (EAA) benchmark platform are used for validation purposes. Boundary and design operating conditions are applied to the numerical model to replicate the experimental setup. Simulation and experimental data are compared, showing an excellent agreement in terms of fan efficiency with less than 1% deviation, as well as broadband and tonal noise within 0.7 dBA in terms of overall sound pressure level. An advanced post-processing analysis is performed to shed light on the noise generation mechanism in tip clearance. It is observed that both fine random turbulent structures and large coherent vortices are generated in the tip gap. The continuous impingement of the fine turbulence with the following blades and the blade itself is responsible for the radiation of broadband noise, while the interaction between the large coherent tip vortices, spinning at a lower angular velocity with respect to the fan shaft, and the following blades leads to the generation of narraowband peaks at sub-harmonics of the blade-passing frequencies. Finally, a beamforming analysis further confirms that the main noise sources are located in the blade tip clearance and tip regions.

효율과 소음을 고려한 원심팬 입구형상의 수치적 최적화

The inlet geometry of the centrifugal fan has been numerically optimized to maximize the fan performance and to minimize the fan noise. For the optimization, a representative sub-model using the periodic boundary condition in the circumferential direction was constructed. The radii of the bell-mouth and the shroud at the inlet of the fan were selected as design variables. The objective functions were the fan efficiency for the fan performance and the turbulent viscosity for the noise metric. The moving reference frame (MRF) formulation was adopted for the flow analysis. The case studies were conducted and the results were analyzed using the response surface method. The optimal shapes for the maximum efficiency, minimum noise, and the combined performance were examined with the actual fan model with casing geometry. Details of the optimization process, the effects of design variables and the final optimization results were summarized in quantitative and qualitative ways.

Study on Air Cabin Ventilation System by Local Structural Optimization during Tunnel Construction

In tunnel construction, the difficulty of ventilation gradually increases with the increase of ventilation distance, which endangers construction safety and delays construction progress. This paper presents an air cabin ventilation system of the tunnel during construction. Theoretical calculations show that the energy consumption of this ventilation system is reduced by 20.7% compared with blowing ventilation, especially since the resistance loss along the air duct is reduced by 47.04%. A 3D numerical model validated with field test data was employed to discuss the air cabin structural parameters on the ventilation efficiency of the axial fan. The results show that the relative pressure on the fan’s end face increases when the air cabin’s length–width ratio is R = 1:2. The fan spacing S = 2–4 m can ensure the larger relative pressure of multiple fans. The significant difference in air demand between the left and right sides causes the disordered airflow. Set a middle diaphragm length of 1.5 D in the air cabin, which can effectively reduce the phenomenon. The middle diaphragm with a radian of 30°effectively reduced the local loss by 59.40%. The proposed ventilation system shortens the ventilation distance and has the advantages of low energy consumption and resistance loss. It improves the construction environment and is a valuable means of ventilation design for tunnel construction.

Volute Optimization Based on Self-Adaption Kriging Surrogate Model

Optimizing the volute performance can effectively improve the efficiency of a centrifugal fan by changing the volute geometric parameter, so the self-adaption Kriging surrogate model is used to optimize the volute geometric parameter. Firstly, volute radius Rd, the radius of tongue r, and outlet angle of the volute θ are selected as the optimization parameters of the volute, and latin hypercube sampling is used to configure the initial sample points, the corresponding three-dimensional aerodynamic model under each sample point configuration is constructed. CFD software is used to simulate the aerodynamic efficiency and total pressure of the centrifugal fan under each initial sample point configuration. Secondly, the Kriging surrogate model of initial sample point configuration parameters, aerodynamic efficiency, and total pressure of volute is constructed, and sample points are added by expectation improvement (EI) method to improve the fitting accuracy of Kriging surrogate model. Finally, the high-precision Kriging surrogate model is used as the fitness function of NSGA-II algorithm to find the Pareto optimal solution under multiobjective optimization, and the optimization target are aero dynamical efficiency and total pressure. The rationality of the above method is verified by optimizing the 9–19.4A type centrifugal fan volute. The efficiency of the optimized fan under working conditions is increased by 1%, and the total pressure under working conditions is not reduced. The optimized volute can effectively improve the overall performance of the centrifugal fan. This study is helpful to promote the application of numerical optimization design method in the volute of centrifugal fan. It provides reference for the optimization design of high-performance centrifugal fan.

Design and Numerical Simulation of High Performance Heat Dissipation Axial Flow Fan

The airfoil used in axial fan blades is one of the important factors that affect the efficiency of the axial fan. In this paper, the design process of the axial flow fan is realized by FORTRAN language, and then the traditional airfoil CAP2021 and the new high-performance airfoil CAP2021-Mod designed by us are applied to the design of the axial flow fan, and the impellers of two axial flow fans are designed, and the design results are compared and analyzed. Finally, the CFD numerical simulation of the two axial flow fans is carried out, and the Aerodynamic performance and flow field characteristics of the two fans are obtained. The simulation results show that the axial flow fan with a high-performance airfoil has better Aerodynamic performance, and it is verified that the high-performance airfoil can be used in the design of a high-performance axial flow fan.

Improvement for energy efficiency and control characteristics in variable air volume system using in-situ sensor calibration method based on autoencoder

The accuracy of sensor measurement has an important influence on energy efficiency and control characteristics of air conditioning systems. However, the sensor will inevitably have errors due to sensor installation location or aging in the practical system. In previous studies, the sensor virtual in-situ calibration (VIC) method is proposed to diagnose and calibrate sensor faults based on physics-based methods with plenty of sensors. However, the basic sensors are only installed due to the cost and limited installation space in the practical system, which restrains this method. To address this problem, the autoencoder (AE) based on the internal relationship between sensor variables is applied to establish the sensor model to achieve calibration. This paper studies the applicability of the AE that constructs sensor models with limited sensors, and the accuracy of the VIC method under different working conditions. The results show that the AE can well realize the sensor model construction with high accuracy, which lays a foundation for the implementation of the VIC method. Meantime, the accuracy for different scenarios of the single fault is more than 90.75% after calibration, the concurrent fault can also reach more than 88.5%. The supply air temperature calibration will make the continuous regulating valve keep the normal opening to maintain the air volume and ensure the stability of indoor temperature. The static pressure calibration will increase the energy efficiency of the supply fan by 17%, make the VAV box adjust normally, and avoid the disorder of the control loops. The differential pressure sensor calibration will increase the energy efficiency of the water pump by 21%, and ensure normal water flow. Meantime, the calibration of three sensors reduces the time to reach a stable state by more than 20.6%. The VIC method based on AE makes the application scenario of sensor fault calibration more extensive and universal.

An optimization method of mine ventilation system based on R2 index hybrid multi-objective equilibrium optimization algorithm

With the increase of mining years, the mine ventilation system becomes more and more complex, causing serious energy waste. The traditional single-objective optimization model cannot​ accurately describe the complex mine ventilation system. In order to solve this problem, this paper establishes a multi-objective optimization model for mine ventilation systems considering ventilation energy consumption, fan shaft power, and fan efficiency. Furthermore, we proposed an R2 index hybrid multi-objective equilibrium optimization algorithm(R2HMEOA). Firstly, We use R2 index to improve the sorting rules of the Pareto solution. Secondly, improve the reference point strategy, and propose an elite archiving strategy based on R2 index. We use classical test functions to test the proposed algorithm. The results show that the algorithm has obvious advantages. Furthermore, we apply the algorithm to the ventilation system optimization of Wangjialing mine of Zhongmei Huajin Energy Co. Ltd. The results show that the algorithm can effectively reduce the ventilation power consumption and improve the shaft power and efficiency of the fan, which proves the practicability of the proposed algorithm.

Nacelle intake flow separation reduction at cruise condition using active flow control

Turbofan engine intakes are designed to provide separation-free flow at the fan face over a wide range of operating conditions. But at some off-design conditions, like at high flight speeds and high angles of attack (AoA), the aero engine intake may encounter flow separation. This boundary layer separation inside the nacelle inlet of an aircraft engine can lead to a large number of undesirable outcomes like reduction in fan efficiency, engine stall and high levels of stress on the fan blades. Active flow control is a promising solution to reduce inlet boundary layer separation and the associated fan-face flow distortion at such off-design conditions. By blowing pressurized air into the intake near the separation point, the boundary layer is energized and separation can be controlled. This study investigates the applicability of lip blowing, an active flow control technique, to control intake separation and flow distortion at the fan-face. First, intake separation was triggered in a 3D CFD model based on the NASA Common Research Model (CRM) using high AoA cases at cruise condition (Mach number 0.85, Mass flow capture ratio ∼0.7) and the features of separated flow were analyzed. Thereafter, active flow control was introduce to the intake in the form of two types of lip blowing, direct and pitched blowing. The efficacy of lip blowing at achieving separation control in an ultra high bypass ratio turbofan engine intake has been established through this study. The present paper also examines the significance of blowing parameters like the type of blowing, blowing pressure ratio, and blowing slot dimension, at different angles of attack to identify the critical control parameters. Our research successfully establishes proof of concept by demonstrating the feasibility of using lip blowing for separation control in aero-intakes, via numerical modelling. Furthermore, this study also provides crucial insights regarding the important variables to be considered for future experimental studies, and also for detailed studies covering a wider range of operating and blowing conditions.

Model-based efficiency mapping and parametric analysis of low-pressure axial fans

This paper advances a methodology for axial fan efficiency mapping followed by a design optimization exercise of a low-pressure axial fan for small capacity refrigeration applications. For these purposes, a tailor-made first-principles simulation model based on the so-called blade element theory (BET) was put forward. First, the fan efficiency was deployed into two terms – namely, electric motor and blade efficiency, which in turn was split into two other terms that account not only for the irreversible losses but also for flow maldistribution – in order to identify opportunities for blade optimization. Later, a sensitivity analysis was performed to find out the optimum values of key operating and design parameters of the fan, namely motor speed, blade size and number, chord length, pitch angle, and airfoil characteristics, such as thickness and maximum camber values. Among those, the pitch angle stood out as the most influencing parameter affecting the fan characteristics, including the airflow rate, the power consumption, and the blade efficiency. Comparisons with results obtained by means of the so-called fan laws are also reported for the blade size and speed.

Sound shielding simulation by coupled discontinuous Galerkin and fast boundary element methods

ABSTRACT A code coupling has been established for performing efficient fan tone shielding simulations of aerial vehicles with unconventional engine installations. In particular, the Fast Multipole Boundary Element Method (FM-BEM) which is formulated to solve a surface integral based on the Kirchhoff-Helmholtz wave equation for large geometries is combined with a volume resolving Discontinuous Galerkin (DG) method which is well suited for the compact region around a jet engine intake where strong mean flow gradients are present. The Möhring-Howe acoustic analogy is utilised during the backward data exchange process for derivation of acoustic velocities in presence of a mean flow. The method can help to overcome a major difficulty related to computational complexity when solving fan noise shilding and scattering problems for a complete aircraft geometry.

Optimal pitch angle of jet fans based on air age evaluation for highway tunnel ventilation

The Coandă effect on jet flow can be solved effectively using the jet fan with a pitch angle in highway tunnels. In this study, the ventilation efficiency of the jet fan with a pitch angle in the range 0–12° is tested using the computational fluid dynamics (CFD) method with experimental validation. The mean air age in volume (MAA-V) is applied to evaluate the ventilation effectiveness in the full space and clearance space of tunnel. The results show that the jet fan with a pitch angle can significantly alleviate vortices caused by the jet flow. The pitch angle of 7° can provide a desirable compromise for MAA-V, found to be 13.62% and 20.67% younger than that of 0° for the full and clearance spaces, respectively. Furthermore, the pressure-rise coefficient at different pitch angles is also investigated, and the maximum is obtained at the pitch angle of 7° as well. Finally, the pitch angle of 7° is determined as the optimal angle for the jet fan, which is of great benefit for improving ventilation effectiveness and saving installed power in highway tunnels.

Performance Degradation Evaluation of Low Bypass Ratio Turbofan Engine Based on Flight Data

A low bypass ratio turbofan engine operates in a hostile environment, resulting in performance degradation. This seriously affects the security and reliability of the engine. Therefore, a performance degradation evaluation method for engines based on flight data is proposed. The method expands the equation system to solve the underdetermined problem caused by the lack of engine sensors based on multiple operating point analysis. The improved evolution algorithm is employed to solve the equation system, which relieves the problem of insufficient precision. The engine performance degradation dataset is established based on the engine performance calculation model to verify the reliability of the degradation evaluation method. The results show that the method is applicable to the dataset. Finally, the method is applied to the actual flight data to study the law of the performance degradation of the researched engine, which indicates that the engine’s fan efficiency and high-pressure compressor flow capacity have an apparent downward trend over time.

Redesign and Implementation of Big Fan Impellers for Enhancing Its Efficiency

This paper presents the effort on big fan efficiency enhancement by the modification of impeller geometry especially blades angles and radius while maintaining the other parameters such as casing geometry, entry and exit diameters, rotational speed, number of blades, flow rate, and static pressure matching to the field requirement including existing installation. The combination of numerical calculation based on the semi-empiric formulas and computational fluid dynamics (CFD) is used as the methodology. Two big fans, A and B, which are widely used in the cement industry with nominal flow capacities of 300,000 and 567,500 ㎥/h and having static pressures of 4,000 and 12,200 ㎩, were used as case studies. Theoretical performance comparison between original and modified fan design geometries as well as field measurements were also conducted in this study. The results show that modified geometry design can increase up to 4.53% of fan efficiency which contribute to reduce shaft absorbed power up to 50 ㎾ for fan A and 130 ㎾ for fan B respectively.

Design of Ducted Fan Based on Optimal Circulation Distribution

The ducted fan lift system has been widely used in vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV). According to the overall design requirements of a VTOL UAV, based on the optimal circulation distribution condition without blade element drag and combined with strip theory, the blade torsion angle distribution and chord length distribution are given. The parameters of ducted fan are designed, and the preliminary design of ducted fan lift system of this UAV is completed. The aerodynamic characteristics of the isolated fan and the ducted fan are compared by numerical simulation method, and the thrust characteristics of the ducted fan at different flight speeds are calculated. The results show that the duct increases the induced velocity at the propeller. Compared with the isolated fan, the power load and hover efficiency of the ducted fan are increased by 36.8% and 36.3% respectively. The hovering efficiency of the ducted fan designed by this method reaches 83%, which meets the design requirements and proves the effectiveness of the design method.

Aerodynamic performances and efficiency of axial flow fan placed in cooling system

Abstract One way to reduce the aerodynamic noise generated by the cooling system of construction machinery is to improve the fan efficiency and then drive the cooling fan at a lower speed. Computational Fluid Dynamics (CFD) is effective for clarifying the mechanisms of the fan efficiency, but there are few reports that capture the flow field around the axial fan blades installed in the cooling system of construction machinery, that is, in a high static pressure environment. Moreover, from the viewpoint of the three-dimensional flow field, the fan efficiency has not been sufficiently studied. In this study, the flow field of the entire cooling system including an axial cooling fan was visualized by numerical simulation using ANSYS-CFX17.0, and the effect of the flow field formed around the blades on the fan efficiency was investigated. In case of a single axial fan, increase or decrease in pressure caused by airflow collision or separation is higher than the entire cooling system. As a result, the loss becomes large. In addition, the increase in loss due to collision or separation occurs regardless of the blade span length, and its magnitude is proportional to the circumferential velocity at each point of the blade except for the blade tip.