Fan Vibration Research Articles

Evolution of flow structure and heat transfer enhancement mechanism in impinging jets excited by piezoelectric fan

While jet impingement is recognized for significantly enhancing local convective heat transfer, there remains a considerable challenge in further improving its heat transfer performance and uniformity to meet the growing demand for efficient heat transfer. To address this challenge, this study proposes a method that integrates a piezoelectric fan into a continuous jet, taking advantage of the piezoelectric fan's vibration to deliver pulsating excitation to jet impingement while preserving its continuity. An experimental study is performed to identify the roles of piezo-fan integration on improving convective heat transfer from a continuous circular jet onto a flat target surface. The tests are performed under Rej=2,500∼7,500 (circular jet), s/d = 2∼28 (non-dimensional fan-to-jet distance) and L/d = 2∼8 (non-dimensional jet-to-target distance). In addition, few numerical simulations regarding the flow fields are also made to illustrate the mutual interaction mechanism between piezo-fan and continuous jet. The findings reveal that, in the longitudinal configuration, the average values of heat transfer enhancement factor (χ) and heat transfer uniformity factor (ξ) are approximately 13% and 0.5% higher, respectively, compared to the transverse configuration. In the longitudinal arrangement, the significance of the piezoelectric fan amplifies as the circular nozzle gradually distances itself from the target surface. This fan assumes a pivotal role in augmenting both the uniformity and efficiency of heat transfer associated with the circular jet. Conversely, when the piezoelectric fan moves beyond a specific s/d value (s/d = 10), the interaction between intermittent flow and the wall-jet experiences complete cessation. Despite the existence of a fountain effect resulting from the interaction between the piezoelectric fan and the circular jet in the longitudinal configuration, its discernible impact on overall heat transfer attenuation is minimal. The insights gained from this study will be valuable in improving active strategies for jet impingement and promoting the development of piezoelectric functional devices.

Reduction of a fan vibration activity in a life support system of oil and gas stations

Relevance. Electromechanical fans are widely used in life support systems of oil and gas stations, operate in conditions of vibration, high rotational speeds and loads. Design, technological and operational reasons influence vibration activity of an electromechanical device. The greatest "contribution" to the existing vibrations, according to the frequency spectrum, is made by the imperfection of the design elements of the ball bearing. They are: separator movement, variable stiffness under the action of radial load, interaction of micro-dimensions of working surfaces, facet and waviness of working surfaces of rings and balls. In addition, the resulting vibrations negatively affect both the reliability and durability of the fan. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, it is advisable to reduce it with the help of a technical solution by introducing a damping element into a kinematic circuit of the vibration source. In this regard, the development of a damping device is an integral technical task that helps to reduce the vibration activity of technical life support systems of oil and gas stations, as well as to improve the quality of environmental conditions of human life. To reduce vibration activity, a damper design is proposed that takes into account various types of energy dissipation. However, given the dense spectrum of vibration frequencies from ball bearings, a viscous friction element is introduced into the damper design. To determine the effectiveness of reducing vibration activity, a model of the damper in question was made based on the developed 3D model. For tests in determining the effectiveness of applying a viscous friction element, two variants of the damper design were used. In the first version of the damper design, there was no viscous friction element, and in the second version there was one. According to the test results of the damper layouts, it can be seen that the developed technical solution to reduce the vibration activity of the electromechanical device has practical confirmation. The studies underlying the developed design of the damper with a viscous friction element allows for reduction in the vibration amplitude. Object. Electromechanical device in operating mode. Aim. To describe the vibration activity in the operating mode of an electromechanical device in the entire spectrum of disturbing effects acting along the axes, taking into account the imperfect geometry of ball bearing parts; to develop a damper for reducing the vibration activity level in the electromechanical device. Methods. Vibration diagnostics, computational mathematics, measuring instruments, software "Vibration recorder-F", "Vibration Recorder-M2", "Logger"-recorder and "Bearing". Results. The paper demonstrated the effectiveness of the proposed technical solution to reduce the vibration amplitude in the operating frequency range of the electromechanical device rotor up to 4 times compared with the corresponding maximum amplitude value without its use.

Numerical Simulation and Optimization of Peanut Sheller Air–Screen Cleaning Device

To improve its cleaning performance, the peanut sheller’s air–screen cleaning device was used as the research object, and a numerical simulation was carried out. A scheme was proposed to optimize the installation angle of the screen surface of the air–screen cleaning device, and the influence of the airflow velocity of the sieve surface before and after the structural improvement of the machine on the airflow distribution of the whole chamber was evaluated. At the same time, the computational fluid dynamics–discrete element method (CFD–DEM) of coupling simulation was used to carry out single-factor simulation tests on the improved air–screen cleaning device, analyze the movement trajectory, velocity, and displacement of the extrudates in the cleaning chamber, characterize the separation law of extrudates, and determine the parameter ranges for each factor. In addition, based on the central composite Box–Behnken design, an orthogonal simulation test was carried out with three factors, including fan speed, amplitude, and vibration frequency, and the influence of each factor on the kernel loss rate and impurity rate was investigated. Furthermore, the influencing factors were optimized, and the optimal parameter combination was obtained; when the fan speed was 1682.72 r/min, the amplitude was 3.74 mm, and the vibration frequency was 492.86 Hz, it was more conducive to the cleaning of kernels. Finally, the accuracy of the simulation and optimization methods was verified via the machine test, and the optimal parameter combination was obtained: at a fan speed of 1680 r/min, an amplitude of 3.7 mm and a vibration frequency of 490 Hz were achieved, and the kernel loss rate and impurity rate were 2.01% and 2.42%, 3.71 and 4.42 percentage points lower than those before optimization, respectively.

Separating method for multi-source vibration signals in ultra-weak fiber Bragg grating distributed acoustic sensors

Mixing multi-source vibration signals presents a major challenge in target recognition in distributed fiber optic acoustic sensor systems. This article proposes a deep learning method for separating ultra-weak fiber Bragg grating (UW-FBG) distributed acoustic sensor (DAS) multi-source signals. An experimental setup is constructed to create vibration environments for knocking, fan vibration, and steel pipe friction. The UW-FBG DAS system is used to collect single-source vibration signals, as well as two-source and three-source mixed vibration signals. First, a wavelet denoising algorithm is used to preprocess the data. Second, the datasets are constructed for simulated mixed signals and measured mixed signals. The Conv-TasNet deep learning network is utilized to separate DAS vibration signals. Results demonstrate that the proposed method can separate mixed signals of vibration, fan, and steel pipe friction sources, obtaining the corresponding time–frequency entropy similarity of 97.5%, 92.8% and 90.2%, and compared with commonly used multi-source signal separation methods, it has advantages in separation performance and separation time, and exhibits good robustness in different signal environments. This finding the efficacy of the separation method and provides a valuable solution for DAS multi-source signal separation problems in complex environments.

Systematic Filter Design by Convex Optimization for Disturbance Rejection in Dual-Stage Actuated Hard Disk Drives

To enhance storage capacity in hard disk drive systems (HDDs), dual-stage actuated systems employing both piezoelectric and voice coil motors (VCMs) are utilized in the positioning of magnetic heads. However, external disturbances, such as rotational vibrations and cooling fan vibrations, necessitate the design of controllers with robust disturbance rejection performance to further improve positioning precision. In this paper, we propose an auto-tuning method for a fixed-structure filter in a dual-stage actuated HDD system. The filter parameters are determined using our proposed frequency response data-based convex optimization process. Furthermore, the initial guess for the optimization is selected from the Robust Bode (RBode) plot which is a visible tool in designing robust controllers. Simulation results confirm the effectiveness of our proposed method.

Introduction to Ansys NVH solutions focusing on the Vibro Acoustics

Product validation focusing on NVH heavily relies on physical testing which put NVH focused validation on right hand side of the Product Validation Process. Due to this, lot many times design changes are not possible or expensive or time consuming which reduces overall product quality. Industries like Automotives and ground transportation, Aero and Defense, High Tech, Industrial products making huge investments on NVH validation to win over customer perception battle. Ansys geared up in providing industry leading NVH Solution with Mechanical, LS-Dyna, Motion, Sound along with other products like Maxwell, Fluent, Optislang. NVH workflows driven by highly correlated simulation models, Integration of our key industry leading technologies and Guided, Automated, DOE friendly, Cloud native NVH Solutions are our TOP 3 goals. To introduce Ansys NVH Solutions focusing on the Vibro-Acoustics to Acoustical Society of America communities, we will cover key capabilities from different products briefly and demonstrate NVH Workflows in detail. Electric Motor NVH Simulation—Excitation generated due to Electro Magnetic forces Powertrain/Driveline/Gearbox NVH Simulation—Excitation generated due to multi body dynamics simulationFan NVH Simulation—Excitation generated due to structural vibration of fan driven by flow simulation.

Effect of moving-orientation of the piezoelectric fan on thermal characteristics of the concave surfaces with different curvature

The present work aims at numerically investigating on the flow and heat transfer performances induced by vibrating piezoelectric fan for cooling heated concave surfaces. Two main relevant parameters, relative curvature (K) of concave surface and moving-orientation of the piezoelectric fan, are taken into consideration. The relative curvature (K) is varied from 0.01 to 0.25. The moving-orientations of the piezoelectric fan include transverse oscillation and axial oscillation. The influence mechanism of these parameters are analyzed in terms of the time-averaged heat transfer coefficient, instantaneous streamlines and isosurface of λ2. The heat transfer results indicate that the axial oscillation is more favorable for improving the heat transfer performance than the transverse oscillation, especially in the zone near the fan vibration envelope. Meanwhile, the flow field reveals that the relative curvature of the concave surfaces influences the flow feature under longitudinal configuration substantially.

Failure analysis on weld cracking of a centrifugal fan blade in a nuclear power plant

Abstract Abnormal sound occurred during a centrifugal fan startup in a nuclear power plant and the root welds of two blades of the fan were cracked during the maintenance. In this paper, the failure blade and weld were comprehensively analyzed by means of morphology, composition, hardness, metallography and microstructure. It was found that the T-shaped weld at the blade root was convex and poor forming. The overall welding quality of the weld was poor, and there were the defects of arc pits, slag inclusion holes, composition segregation in the weld. The blade was subjected to typical fatigue stress due to fan vibration during operation. Due to poor forming and poor quality of the weld, the stress concentration factor at the weld toe of the fillet weld was large and the fatigue resistance was poor. Finally, blade fatigue cracking occurred during long-term operation.

The Empirical Assessment of Vibration in HVAC Systems

Background and purpose: Vibration caused by ventilation systems in buildings is one of the harmful physical factors that can cause harm to residents. Therefore, measuring and controlling vibration is important.
 Materials and Methods: In the first step of the study, the vibration accelerometer was placed on the base of a fan where the vibrations were sent toward the duct wall. A vibration assessment of the building was conducted in the other steps to compare with guidelines. In the next step, isolation method was used to control vibration. By placing the isolator on the duct wall, the accelerometer was located on the body of the duct wall and the value of vibration was measured in a millimeter per second. All stages of the experiment were performed in the Faculty of Health of Isfahan University of Medical Sciences in 2018.
 Results: The maximum vibration velocity reduction in the building was related to the frequency of 68 Hz, which reached 33 mm/s after isolation. In addition, the fan vibration at 485 Hz was equal to 2.1 m /s, which decreased to 2 mm /s after isolation.
 Conclusion: Comparison of vibration after fan isolation with standard showed that this method has been effective in reducing the fan vibration resulting in the vibration to reach below the standard.

Servo Controller Design for Triple-Stage Actuator in HDD to Compensate for High-Frequency Fan Vibration

Hard disk drives (HDDs) used for data servers are exposed to various vibrations. These vibrations are mainly caused by the cooling fan that controls the temperature inside the server. The vibration affects the positioning accuracy of magnetic heads that read/write digital data. This is an obstacle to obtaining high data transfer rates. To compensate for vibration, the control system for the magnetic heads must have higher frequency control bandwidth as the spectra of these vibrations have peaks up to 10 kHz. In current HDDs, the control system is a triple-stage system consisting of a voice coil motor (VCM), a milliactuator, and a microactuator. In this article, we propose a design strategy for a triple-stage control system to compensate for vibration. The design strategy addresses unstable controllers in the control system. The gain of the feedback controllers of the VCM and milliactuators is increased to expand the control bandwidth. Although these feedback loops become an unstable system due to the increase in the controller gain, the controller for the microactuator is designed to stabilize the overall feedback loop. As a result, the control system achieves high control bandwidth. The performance of the proposed control system is calculated based on the compensation of the vibration caused by the data server. The proposed design can improve positioning accuracy by approximately 48%–58% compared with the conventional controller design.

Numerical Analysis of inlet vortex in the scaled engine

A jet engine that works near the ground and generates high thrust at low speed can experience the flow separation from the ground surface up to its inlet and, as a result, the formation of a famous vortex. This vortex extended from the ground surface to the fan inlet is known as the inlet vortex. In the present study, a jet engine model scaled down by 1/30 relative to the real jet engine with 3 million hexahedral elements is simulated using Computational Fluid Dynamics (CFD). The obtained results agree with empirical relationships, and the inlet vortex can be analyzed in scales much lower than the original prototype. Also, the inlet vortex gets weakened by increasing free stream velocity and completely degraded at higher velocities. By understanding how this phenomenon occurs and can be dealt with, the Foreign Object Damages (FOD) such as compressor surge, fan vibration, and particle ingestion into the engine core can be prevented.

Mechanical noise and vibration control

This presentation is intended to provide basic training for entry-level and early-career acoustical consultants in the area of mechanical equipment noise and vibration control in buildings. The seminar will address the following topics: (1) general design guidelines and noise and vibration criteria; (2) basics of fan, pump, and compressor noise generation and vibration isolation; (3) HVAC ductwork and piping design; (4) evaluating manufacturer sound data; (5) laboratory measurement of mechanical equipment; and (6) conducting field measurements and calculations. References to past projects from the speaker’s 40 + years of consulting experience will be included to emphasize specific points, as appropriate.

Research on fan vibration fault diagnosis based on image recognition

The conventional methods for vibration fault detection and diagnosis relies on feature extraction from the waveforms of the vibration signals. This article exploits the scope of image recognition application for the detection and diagnosis of fan vibration faults. In this paper, a novel image recognition technique is proposed for vibration-based fault diagnosis using the spectrum images of the vibration signals. 1D vibration signal spectrum is initially computed using Fast Fourier Transform (FFT) and the FFT frequencies are adjusted such that it captures a vibration spectrum diagram as 2D image representation. FFT based vibration analysis is done and the image recognition concept is utilized for feature extraction and a machine learning classification module is used for fault analysis and diagnosis. Effective feature generation is done using Principal Component Analysis (PCA) by removing the redundancy from the feature vectors and machine learning classifiers are used to obtain improved image recognition and classification performance. Artificial Neural Network (ANN) classifier yields better performance in terms of various performance parameters and percentage improvement in terms of accuracy for ANN classification methods over Support Vector Machine (SVM), k-Nearest Neighbours (kNN) and Random Forest Ensemble (RFE) methods are 10.01 %, 4.51 % and 2.01 % respectively. Comparative scenarios are considered in this work for fan vibration fault detection as well as diagnosis based on the image features for various realistic vibration fault conditions. Effectiveness of the proposed image recognition-based technique is compared with the state-of-the-art methods, justifying its outperformance for fan fault detection and diagnosis using the combination of spectrum adjustment, PCA and ANN classification method.

Industrial fan vibration signature characterization

Technique for measuring and reducing industrial fan vibration and noise is detailed. A method used to characterize the vibration signature for 100% industrial fan systems shipped is described. A fan system consists of motor, propeller and cage. We measure triax accelerometer vibration, microphone (both sound pressure level in dBA and raw signal in Pa) along with the current of three phase power for each fan shipped. Comparisons are done immediately with the ISO 14694:2003 standard and troubleshooting and design changes are implemented if vibration limits are exceeded. The method and results are provided for several cases. Troubleshooting and best practices are described for various designs. A portable system takes measurements in the field which are compared to the factory baseline characterization in real time to solve installation problems.

Using modern clustering techniques for parametric fault diagnostics of turbofan engines

The 21st century aviation and aerospace technologies have evolved and become more complex and technical. Turbofan jet engines as well as their cousins, the rocket engines (liquid/solid) have gone through several design upgrades and enhancements during the course of their design and exploitation. These technological upgrades have made engines very complex and expensive machines which need constant monitoring during their working phase. As the demand and use of such engines is growing steadily, both in the civilian and military sectors, it becomes necessary to monitor and predict the behavior of parametric data generated by these complex engines during their working phases. In this paper flight parameters such as Exhaust Gas Temperature (EGT), Engine Fan Speeds (N1 and N2), Fuel Flow (FF), Oil Temperature (OT), Oil Pressure (OP), Vibration and others where used to determine engine fault. All turbo fan engines go through several distinctly different working phases: Take-off phase, Cruise phase and Landing phase. Recording generated parametric data during these different phases leads to a massive amount of in-flight data and maintenance reports, which makes the task of designing and developing a fault diagnostic system highly challenging. It becomes imperative to use modern techniques in data analysis that can handle large volumes of generated data and provide clear visual results for determining the technical status of the engine under investigation/monitoring. These modern techniques should be able to give clear and objective assessment of the object under investigation. Cluster analysis methods based on Neural Networks such as c-means, k-means, self-organizing maps and DBSCAN algorithm have been used to build clusters. Differences in cluster groupings/patterns between healthy engine and engine with degraded performance are compared and used as the bases for defining faults. Fault diagnosis plays a crucial role in aircraft engine management. Timely and accurate detection of faults is the foundation on which maintenance turnaround times, operational costs and flight safety are based. The data used in this paper for analysis was obtained from flight data recorder during one flight cycle. The final decision on a fault is taken by an engineer.

Health Monitoring of Induced Draft Fan in an Aluminium Smelter

Maintenance is highly essential as to support the machine availability, product quality and plant safety. The timely repair at minimum coast is the basic criteria for good maintenance. Appropriate maintenance can sustain continuous and reliable operation with reduction in down time, high productivity, number of secondary failures, low inventory level and accident of the plant. In spite of high initial investment, most of the industries adopt condition based maintenance (CBM) to avoid sudden disruption in production. CBM is an important tool which includes observing, monitoring, diagnosis and prognosis for running a plant seamlessly, as this maintenance planning and actions have become an integral part of engineering investigation. In this paper, condition monitoring of Induced Draft (ID) fan in an Aluminium smelter has been done while it was in operation. The vibration of ID fan was measured and analyzed to detect the defect of its impeller and corrected subsequently.

Vibration fault diagnosis and dynamic balance processing analysis of blower in thermal power plant

The fan vibration of the forced draft fan in a power plant is too large during normal operation, which seriously affects the normal operation of the unit. Through the vibration detection, on the basis of comprehensive analysis of the fan vibration failure mechanism, the means of adjusting the balance of the fan is adopted to reduce the excessive vibration to an excellent level. This paper introduces an excessive vibration fault caused by a device imbalance problem that is treated by vibration detection and dynamic balance test. The article elaborates the diagnosis method, diagnosis process and treatment suggestions, and deeply analyses and summarizes the characteristics of rotor imbalance, and provides reference for the diagnosis and analysis of the same type of fault.

Leakage flow flutter in a low-speed axial-flow fan with shrouded blades

A large-amplitude axial vibration of a rotor fan with shrouded blades has been experimentally observed. The analysis of the Campbell diagram shows that the vibration is related to a backward-whirl vibrational mode of the rotor which is always present, with different amplitudes depending on the operating conditions and configuration. Modifications of the shroud roughness and insertion of small obstacles in the gap region have independently shown that leakage flow fluctuations constitute the excitation of the large-amplitude vibration. This indicates that the phenomenon is likely a flutter, as it is also suggested by the observed intermittency and aerodynamic stiffening. The feedback of the vibration on the flow is likely due to the variations of the gap size.

ВИБРОАКТИВНОСТЬ МАЛОШУМНЫХ ВЕНТИЛЯТОРОВ

Low-noise fans are widely used in the sphere of human life for sanitary and technological purposes. Creation of low-noise fans is currently an advanced scientific and technical area. In some fields of their application, reduced vibrations and noises are of paramount importance not only in terms of sanitation and health, but also from a scientific point of view. This work presents a comparison of the quality of low-noise fan development depending on the selected resistance type. The efficiency of the damping of mechanical system (a low-noise fan) vibrations according to the type of resistance moment used is confirmed analytically and practically. Nowadays, a number of fan types implemented in hundreds of designs have been developed and are in service. In this work, the whole variety of the produced nomenclature of low-noise fans is reduced to two basic types – axial and radial. The paper reports that to ensure minimum noise in the operating mode of the low-noise fans presented in the work, a wideband vibration damper is needed as a required functional unit, and the walls of the fan housing should be sandwich-like with layers made of sound absorbing, sound insulating, and vibration damping materials.

LBM simulation of piezo fan in square enclosure

PurposeThis paper aims to investigate the use of a piezo fan in an enclosure on wall heat transfer and thermal boundary layer profile in constant wall temperature situation.Design/methodology/approachThe governing partial differential equations of mass, momentum and energy in addition to boundary conditions are solved by lattice Boltzmann method. The problem is solved numerically using D2Q9 population's model and Bhatnagar–Gross–Krook collision model with a code written in MATLAB.FindingsThe effects of Prandtl number (Pr) and the frequency of piezo fan vibrations are critically investigated on the hydrothermal characteristics of the square cavity. The mesh independency study and the validation of the proposed model are accomplished with numerical results of Ghia et al. (1982) and analytical solution of pure conduction very good agreement is found between present results and benchmark findings. Generally, with increasing beam frequency, the heat removal from heat source increased. It is found that, for all Prandtl numbers, wall Nusselt number will increase with the increase of the beam frequency. This enhancement is more intense in higher Prandtl number.Originality/valueBased on these results, the use of piezo fan in an enclosure can be classified as standalone as well as heat sink integrated cooling solution.