Fan Vibration Research Articles

Confidence interval prediction of ANN estimated LPT parameters

Purpose With the condition monitoring system on airplanes, failures can be predicted before they occur. Performance deterioration of aircraft engines is monitored by parameters such as fuel flow, exhaust gas temperature, engine fan speeds, vibration, oil pressure and oil temperature. The vibration parameter allows us to easily detect any existing or possible faults. The purpose of this paper is to develop a new model to estimate the low pressure turbine (LPT) vibration parameter of an aircraft engine by using the data of an aircraft’s actual flight from flight data recorder (FDR). Design/methodology/approach First, statistical regression analysis is used to determine the parameters related to LPT. Then, the selected parameters were applied as an input to the developed Levenberg–Marquardt feedforward neural network and the output LPT vibration parameter was estimated with a small error. Analyses were performed on MATLAB and SPSS Statistics 22 package program. Finally, the confidence interval method is used to check the accuracy of the estimated results of artificial neural networks (ANNs). Findings This study shows that the health conditions of an aircraft engine can be evaluated in terms of this paper by using confidence interval prediction of ANN-estimated LPT vibration parameters without dismantling and expert knowledge. Practical implications With this study, it has been shown that faults that may occur during flight can be easily detected using the data of a flight without expert evaluation. Originality/value The health condition of the turbofan engine was evaluated using the confidence interval prediction of ANN-estimated LPT vibration parameters.

Thermal intensification of heat transfer characteristics on the plate‐fin heat sink with piezoelectric fan

AbstractThis study applied the computational fluid dynamic (CFD) code, ANSYS Fluent for simulating the effect a piezoelectric fan installed inside the rectangular channel by numerical simulation method for transient flow field and investigating the influence of each parameter. To remove the disorganized form of energy from the electronic components, the reversible piezoelectric effect is employed to energize the piezoelectric fan. To observe the variation of fan characteristics and to predict the convective heat transfer coefficient, CFD code ANSYS Fluent 15.0 is used. The numerical simulation parameters included are Nusselt number, number of fins (n = 12 and 14), and counter‐shift (inward and outward‐phase), and distance between the upper portion of the fan tip to the front part of the low thermal reservoir. Numerical analysis was carried out to evaluate the effect of thermal flow fields on the heat sink and piezoelectric fan employed in a flow domain. the results showed that by varying the height from channel bottom to the center of piezoelectric fan improves the performance of the piezoelectric fan, piezoelectric fan swinging in a transient phenomena and also simultaneously influences fluid flow behavior on the heat source surface, the fan vibration at counter‐phase has a better rate of heat transfer than vibration in in‐phase.

Focus on lasers, imaging, and microscopy

Focus on lasers, imaging, and microscopy

An investigation on convective heat transfer performance around piezoelectric fan vibration envelope in a forced channel flow

An experimental and numerical investigation is performed in the current study to further explore the convective heat transfer performance by a vertically-oriented piezoelectric fan in the presence of channel flow. The effects of velocity ratio and fan tip-to-heated surface clearance are taken into considerations. It is illustrated that the presence of channel flow has an innegligible influence on the vibration amplitudes of the piezoelectric fan under large channel flow velocities. In the presence of channel flow, the vortical structures at the edges of vibrating fan are certainly suppressed, especially under large velocity ratios. On the other hand, the vortical streaming flow mixes with the channel flow to form a long stripe of vortical structure downstream of the fan vibration envelope. Under small velocity ratios, the impingement role of streaming flow along fan tip is still dominated and simultaneously the channel flow passing through the vibration envelope is effectively pulsated. Therefore, combined flows generally produce heat transfer enhancement around the fan vibration envelope related to the pure vibrating fan, especially at a small non-dimensional tip-to-surface gap. While under large velocity ratios, the impingement role of streaming flow induced by a vibrating fan is seriously weakened by the strong channel flow. The convective heat transfer produced by combined flows in the fan vibration envelope is generally reduced in comparison with pure piezoelectric fan. Related to the pure channel flow, the combined flows effectively improve the convective heat transfer, especially downstream of the fan vibration envelope.

Analysis of Waveform Spectrum of Compact Fan Motor Applying MT System

The demand for compact fan motor increases for cooling use in the electronic equipment by weight saving of IT apparatus, spacing-saving now. The quality check of compact fan motor in production field is being conducted by sensory test of inspector. This sensory test requires a lot of experience to accurately examine the subtle difference the fan's noise and vibration, and dispersion occurs in judgment depending on physical condition of inspector and environmental change. Development of a measuring device for quantitatively examine the sound and vibration level and quality of a small fan motor is required in order to improve the problems in these inspection processes. In this research, we focused on improvement of discrimination inspection accuracy of abnormality / normality by extraction of feature value of waveform data and evaluation of effectiveness. As a result, by applying the MT system, it was found that appropriate discrimination test can be performed with the acoustic / vibration waveform of compact fan motor.

Axial Fan Blade Vibration Assessment under Inlet Cross-Flow Conditions Using Laser Scanning Vibrometry

In thermal power plants equipped with air-cooled condensers (ACCs), axial cooling fans operate under the influence of ambient flow fields. Under inlet cross-flow conditions, the resultant asymmetric flow field is known to introduce additional harmonic forces to the fan blades. This effect has previously only been studied numerically or by using blade-mounted strain gauges. For this study, laser scanning vibrometry (LSV) was used to assess fan blade vibration under inlet cross-flow conditions in an adapted fan test rig inside a wind tunnel test section. Two co-rotating laser beams scanned a low-pressure axial fan, resulting in spectral, phase-resolved surface vibration patterns of the fan blades. Two distinct operating points with flow coefficients of 0.17 and 0.28 were examined, with and without inlet cross-flow influence. While almost identical fan vibration patterns were found for both reference operating points, the overall blade vibration increased by 100% at the low fan flow rate as a result of cross-flow, and by 20% at the high fan flow rate. While numerically predicted natural frequency modes could be confirmed from experimental data as minor peaks in the vibration amplitude spectrum, they were not excited significantly by cross-flow. Instead, primarily higher rotation-rate harmonics were amplified; that is, a synchronous blade-tip flapping was strongly excited at the blade-pass frequency.

Experimental and numerical investigations on convective heat transfer of dual piezoelectric fans

An investigation is performed to study the convective heat transfer performance under dual piezoelectric fans. Three main aspects are involved in the current study. Firstly, vibration tests for dual specific piezoelectric fans actuating at the first-mode resonant frequency are conducted to illustrate the influence roles of vibrating phase difference and fan-to-fan pitch on the piezoelectric fan vibration amplitude. Secondly, heat transfer measurements are made to compare the heat transfer among single fan, dual fans in-phase and dual fans out-of-phase. Thirdly, three-dimensional numerical simulations are conducted to reveal the influence mechanism of dual piezoelectric fans on heat transfer. The results show that, the vibrating phase difference of dual fans has nearly no influence on the displacement velocity and amplitude of piezoelectric fan related to single fan once the dimensionless pitch (P/W) is beyond 1.2. The dual piezoelectric fans produce nearly the same peak heat transfer coefficient as that of single fan case. Of particular is that the dual fans operating in-phase produce more favorable heat transfer than the dual fans operating out-of-phase, especially in the gap zone between dual fans. Due to the interaction between dual fans, the streaming flow induced by one vibrating fan suffers the action of sweeping flow of another vibrating fan when they operate out-of-phase. While for the dual fans operating in-phase, the streaming flows induced by vibrating fans merge together to form stronger wall jet flow in the region between two fans.

Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

Experimental tests are carried out to investigate the convective heat transfer performances on a flat surface around the vibration envelope of a vertically-oriented piezoelectric fan in the presence of cross flow. Distinct behaviors of convective heat transfer are illustrated under the present conditions of piezoelectric-fan excitation voltage (U = 50, 150, 250 V) or characteristic velocity (u PF = 0.83, 1.67, 2.34 m/s) fan tip-to-heated surface gap (G = 3, 5, 7 mm) and cross flow velocity (u CH = 0.94, 1.56 m/s). In addition, three-dimensional flow field simulations are conducted to illustrate the instantaneous flow fields around the vibrating fan. By comparing with the pure piezoelectric fan, the vortex induced by the vibrating fan is pushed downward by the cross flow and a series of vortices are displayed down the vibrating fan. It is confirmed that the presence of cross flow is contributive to the improvement of convective heat transfer in the rear zone downstream fan vibration envelope. The impingement role of streaming flow induced by piezoelectric fan is reduced by the presence of cross flow in the fan vibration envelope. On the other hand, the oscillating movement of the piezoelectric fan promotes the disturbance intensity of cross flow passing through the fan vibration envelope. These two aspects make the conjugated convective heat transfer in the vicinity of fan vibration envelope complicated. In general, the convective heat transfer in the vicinity of fan vibration envelope is mostly improved by the combined action of fan-excited steaming flow and cross flow in the situation where the piezoelectric fan is placed very close to the heated surface.

벽걸이에어컨의 원심홴에 대한 과도진동 규명 및 저감

In this paper, experiment and dynamics simulations were carried out to identify and reduce the out-of-plane vibration that occurs in a centrifugal fan of an air conditioner installed to a wall. In a wall-installed air conditioner, large space between a case and heat exchanger is often required for the fan to avoid the collision with the case and exchanger. This large space hinders the slim design of the air conditioner even if air conditioner market demands a slim air conditioner. In the present study, in order to determine the cause of the vibration in the centrifugal fan, the out-of-plane vibration and the physical properties were investigated, and the dynamic characteristics of the centrifugal fan were obtained by experiments. Based on these experiments, a dynamic simulation model was established to determine the cause of the out-of-plane vibration of the centrifugal fan. It was found that the main factor of out-of-plane vibration in the centrifugal fan is the axial misalignment between the centrifugal fan and the motor shaft.

Vibration Level Improvement of Id Fan in a Cement Plant Based On CFD Study of Incoming Dust Particles Streamline

This paper presents numerical study of aerosol flow inside of the induce draft (ID) fan inlet duct of a cement plant and the field observation of the proposed guide plate implementation as vibration reducer. Since ID fan sucks the flow from the outlet of cyclone separator, that is normally swirling flow, and the geometry of the duct tends to produce unbalance fine particles distribution over the duct cross section, the vibration of ID fan increases periodically due to unbalance built-up of the fine particles over fan blades surface. Numerical result shows that, at the ID fan inlet, the distribution of fine particles is unbalance. The ratio of particles concentration in the gas entering fan side and motor side of the ID fan is 1.4 to 1 which influences on the unbalance deposition of sticky particles over related blades surface. Using proper guide plate installed in the last duct elbow before entering to the fan, the ratio of unbalance fine particles concentration reduces to 1.05 to 1 and is kept up to the fan free side and motor side inlets. The proposed guide plate has also already installed in a cement plant ID fan duct and vibration characteristic was also observed during 4 months after tie-in period. The plant vibration observation shows that its level is practically unchanged and maintained at low level (around 2 mm/s at fan side and 0.5 mm/s at motor side) which is still lower than maximum limit (11 mm/s). This condition reduces significantly vibration level and eliminates practically plant stop due to over vibration of ID fan along last 4 months operation which was normally suffered every 1.5 months before implementation of this study.

Vibration and Noise of an Axial Flow Fan

We describe a mechanical/acoustic study of a short-ducted axial flow fan. The purpose is to compare mechanical noise to that caused by flow phenomena. The eigenfrequencies of the fan are identified through measurement and finite element computations. The fan acoustics is evaluated by beamforming studies using the Phased Array Microphone technique. The acoustic measurement data is processed by the Rotating Source Identifier method. The modal analysis of the fan model and the acoustic experiments reveal that the fan noise is dominated by mechanical noise in the few hundred Hz range and rotating sources of broadband noise above.

The study of shrouded fan vibration modes and frequencies on holograph and as a part of the engine on the test rig

The article reports about application results of holographic interferometry method for the analysis ofrotating fan vibration modes. So far there are no practically the experimental works explaining behavior ofturbomachinery bladed discs as a part of the engine, on the basis of knowledge about modes and frequencies ofobservable disc in the absence of rotation. Having initially bladed disc amplitude-frequency characteristics in theform of vibration modes pictures with the corresponding frequencies, and then strain-gauging data for this diskbeing a part of the engine, makes it possible to carry out the vibration modes analysis of rotating disk. Vibrationmodes, received on holographic installation, are identified with vibration modes of a rotating disc on coincidenceof their frequencies.Vibration frequencies and modes of a fan first stage, received on holograph, and thefrequencies, received using spectral analysis method for strain-gauging data, are given in the article. Closevalues of these frequencies allowed to connect vibration modes with rotating disc frequencies. Moreover, there isthe example of turbine rotor disc research, illustrated the importance of knowledge of turbomachinery discsvibration modes, in the article. The study revealed the existence of "horizontal" connection for some vibrationmodes, when two different vibration modes accord with almost the same frequency. On the basis of the carriedoutstudy it is possible to draw a conclusion that before installation of the bladed disc in the engine it isnecessary to define natural frequencies and vibration modes of this disc using modern optical methods, inparticular a holographic interferometry; that will allow to predict more reliably any occurrence of disc vibrationsduring its working as a part of the engine.

Feature Extraction of Vibration of Centrifugal Fan Based on LLE

In order to improve classification ability and diagnostic accuracy of centrifugal fan signals, a new feature extraction method from fault signals of centrifugal fan vibration based on manifold learning method (MLM) that is a kind of reduction method of data dimension is proposed in this paper.The MLM is able to remain nonlinear information of original signal, to improve the classification and diagnostic ability of fault better than traditional reducing dimension methods. The results in this paper show that, fault feature information of centrifugal fan vibration is extracted effectively by the MLM and the fault feature information of different types are separated effectively in themselves areas. The diagnostic accuracy by feature extracted by the MLM is significantly higher than by the wavelet packet analysis method.

Fan Fault Feature Extraction Based on Wavelet Packet Transform

Fan occupies the important position in many industry, it give rise to that fault diagnosis become the new hot research topic, also is the urgent demand of many manufacturing enterprises. This paper based on the theory of wavelet packet transform, selecting wavelet packet transform and energy spectrum to wavelet de-noising and fault feature extraction the fan vibration signal. And use the MATLAB get the fan vibration signal characteristic vector, lay the foundation for the fan fault diagnosis.

True Value Estimation of Centrifugal Fan Vibration Data Based on Fusion Method

Poor information means incomplete and insufficient information, such as unknown probability distributions and trends. In this case, many statistical methods may become ineffective. So a fusion method based on the information poor theory is proposed. The fusion method contains five methods, three concepts, and one rule. The five methods include the rolling mean method, the membership function method, the maximum membership grade method, the moving bootstrap method, and the arithmetic mean method. The three concepts comprise the solution set on the estimated true value, the fusion series, and the terminal estimated true value. The rule is the range rule. The centrifugal fan vibration data is evaluated using the above methods and theory. The experimental investigation shows that the fusion method is effective in evaluating true value with small sample sizes without any prior information of the probability distribution

Application of Fruit Fly Optimization Algorithm-Least Square Support Vector Machine in Fault Diagnosis of Fans

The parameter selection problem of kernel function in support vector machine directly affects the generalization ability of support vector machine model .In order to improve the accuracy of the fault classification of centrifugal fan ,the classification method based the Drosophila algorithm optimizes least square support vector machine is proposed In this paper .First, it uses the eigenvectors based on the fan vibration frequency domain as learning samples .Then it uses the improved least square support vector machine model to recognise the patten of the energy feature of fan vibration signal .This article also uses the particle swarm and ant colony algorithm to optimize least square support vector machine .The simulation results show that the method of least square support vector machine based on Drosophila optimization has the advantages of high recognition rate and high diagnostic speed .And the method is feasible and effective.

Complex approach to the vibrodiagnostic analysis of excessive vibration of the exhaust fan

The paper deals with the analysis of causes of excessive vibration of one of the two fans that in the steelworks provide exhaustion of vapor and residues produced during melting of steel scrap. During operation, the excessive vibration of the problematic fan led to the initiation of cracks in the concrete foundation and the repeated damage to the bearings. Under such circumstances, long-time operation could cause further significant damages or collapse of the whole equipment. The solution of the given task required to apply a complex approach, including experimental and numerical modal analysis of the fan’s rotating wheel as well as a series of operational measurements to assess the actual technical condition of the problematic fan and determine possible damages. The output is a series of measures developed to ensure safe and long-time operation of the fan.

Comparison on Harmonic Response Analysis of Two Kinds of Air Cooling Fan Bridge Model

The fan bridge is the important supporting structure in the air cooling system, is mainly influenced by the fan vibration. By using ANASYS soft ware, analyzing the two different structures of Fan Bridges harmonic response, and comparing them, the conclusion is that the style that Bearing skew support is connected with the upper chord member say truss structure can effectively reduce the adverse effects of equipment vibration on the structure.

Vibration Analysis of Air Condition Unit on Subway

Subway system has many merits including large passenger carrying ability, high speed, strong controllability and reliability of driving. Nevertheless, subways also have brought many disadvantages for human. In many subway systems, noisy environments are clearly observed and passengers are exposed to higher noise levels than permissible limit. This study presents a study of noise and vibration of subway air condition system, so as to grasp the vibration distribution laws of the air condition system. By the tested of noise and vibration, the researcher find the sound distribution rule of air condition is very important Based on the consequence of the testing, the acceleration of air condition has little to do with the subway speed and more to do with the vibration of fan; When the train driving on the viaduct bridge, the acceleration of air condition is biggish in 125 Hz and In 50-1000 Hz the vibration of air condition is obviously. When the train running underground line, as a result of the resonance of body, air condition’s vibration is biggish in 630 Hz and the vibration is obviously in 125-1250 Hz. With the increase of the speed, the influence of the ground’s second radiation on body vibration is enhanced. The superfine gross wool which is used to air condition can achieve good results for noise reduction. This research has higher reference for the vibration and noise reduction of the subway air condition system.

Vibration and Noise Characteristics of Line Flow Fan for Railroad Car

Vibration and Noise Characteristics of Line Flow Fan for Railroad Car