Computational Estimation of Fan Casing Noise at Blade Passing Frequency Component Noise

2012 ◽  
Vol 184-185 ◽  
pp. 95-100
Author(s):  
Jian Cheng Cai ◽  
Yong Hai Zhang ◽  
Shuang Li Long
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Sound Radiation ◽  
Internal Flow ◽  
Neumann Boundary ◽  
Frequency Component ◽  
Dipole Source ◽  
Centrifugal Fan ◽  
Element Analysis ◽  
Blade Passing Frequency

This paper studies both vibroacoustics and aeroacoustics of a centrifugal fan casing; the aim of this study is to explore a methodology to make quantitative predictions of fan casing noise. The spectra of the fan noise and casing vibration were firstly presented; discrete components related to the rotational frequency protrude in the spectra, especially the blade passing frequency (BPF). Computational fluid dynamics (CFD) technique was used to obtain the three-dimensional unsteady turbulent internal flow. Attention was paid to the pressure fluctuations on the volute wall; the shapes of pressure fluctuation were nearly sinusoidal in nature, with the BPF as the primary frequency. On the vibroacoustic side, Fast Fourier Transform (FFT) was applied to the time series of pressure fluctuations to extract the BPF component. A finite element analysis (FEA) model of the casing structure was constructed, and was validated by experimental modal analysis. The harmonic dynamic response of the casing structure was calculated with the BPF pressure fluctuation component as the excitation. The vibration results were then taken as the velocity (Neumann) boundary condition for the noise radiation model which was built in boundary element method (BEM), and the sound radiation was calculated. On the aeroacoustic side, the BPF component of pressure fluctuations was modeled as acoustic dipole source, and sound radiation was also solved by BEM. Results show that the sound pressure level (SPL) of vibroacoustics is fairly small compared to the aeroacoustic counterpart. This study shows that CFD, FEA together with BEM can be used to numerically predict BPF casing noise of turbomachinery successfully.

A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan

2012 ◽  
Author(s):  
Jian-Cheng Cai ◽  
Da-Tong Qi ◽  
Yong-Hai Zhang
Keyword(s):  
Pressure Fluctuation ◽  
Sound Radiation ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Structural Noise ◽  
Tonal Noise ◽  
Fan Noise ◽  
Blade Passing Frequency ◽  
Dipole Sources

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

2D and 3D Unsteady Flow in Squirrel-Cage Centrifugal Fan and Aeroacoustic Behavior

2006 ◽  
Author(s):  
M. Younsi ◽  
F. Bakir ◽  
S. Kouidri ◽  
R. Rey
Keyword(s):  
Unsteady Flow ◽  
Numerical Models ◽  
Pressure Fluctuations ◽  
Internal Flow ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Geometry Modeling ◽  
3D Unsteady Flow ◽  
2D And 3D

The objective of this paper is the study and the analysis of the complex phenomena related to the internal flow in a centrifugal fan, using Computational Fluid Dynamics (CFD) tools, completed with experimental investigation in order to validate the used numerical models. The CFD analysis concerns 2D and 3D unsteady flow. The studied phenomena are the interactions and unsteadiness induced by the motion of the rotating blades relatively to the volute and their impact on the aeroacoustic behavior of the fan. Thus, 3D and 2D unsteady calculations using Unsteady Reynolds Averaged Navier Stokes (URANS) approach has been applied on a hybrid mesh grid whose refinement has been studied and adapted to the flow morphology. Turbulence has been modeled with the k-ω-Shear Stress Model (SST) model. The computational domain has been divided into two zones, a rotating zone including the impeller and stationary zone including the volute. A sliding mesh technique has been applied to the interfaces in order to allow the unsteady interactions between the two zones. The overall performances predicted by the computations have been validated at different flow rate. For each geometry modeling (2D and 3D), the unsteady part of the study is illustrated by analyzing the pressure fluctuations on different points from the lateral surface of the volute. The analysis of the wake generated by the rotation of the blower shows that the volute tongue is the main zone of unsteadiness and flow perturbations. In order to predict the acoustic pressures, the unsteady flow field variables provided by the CFD calculations have been used as inputs in the Ffowks Williams-Hawkings equations.

scholarly journals Analysis of Unsteady Pressure Fluctuation in a Semi-Open Cutting Pump

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3657
Author(s):  
Weidong Cao ◽  
Jiayu Mao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Lower Plate ◽  
Pressure Distributions ◽  
Axial Forces ◽  
Blade Frequency

In order to understand the pressure fluctuation characteristics of a semi-open cutting pump, the three-dimensional unsteady flow fields were calculated. External and internal flow characteristics of four schemes with different relative angles between the rotary cutter and the impeller were studied. The pressure fluctuations in the lower plate, the upper plate, the clearance between the rotary cutter and the fixed cutter, the first section in volute and nearby parts of the tongue were all analyzed, which are all the places that pressure distributions are greatly affected by the static and dynamic interaction, and at the same time, the force on the impeller was also analyzed. The results show that the fluctuations at different positions change periodically; the main frequency is blade frequency. The amplitude of pressure fluctuation decreases from near the rotating part to far away, from near the tongue to far from the tongue. Due to the influence of both impeller and rotary cutter, the pressure fluctuation on the lower plate is the largest. The pressure fluctuation is affected by flow rate, the larger the flow rate, the greater the pressure fluctuation. The radial and axial forces of the impeller change periodically with time, and the number of wave peaks and wave valleys is the same as the number of blades.

Experimental Investigation of Time-Frequency Characteristics of Pressure Fluctuations in a Double-Suction Centrifugal Pump

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Zhifeng Yao ◽  
Fujun Wang ◽  
Lixia Qu ◽  
Ruofu Xiao ◽  
Chenglian He ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Design Flow ◽  
Flow Rates ◽  
Time Frequency ◽  
Blade Passing Frequency ◽  
Design Flow Rate

Pressure fluctuation is the primary reason for unstable operations of double-suction centrifugal pumps. By using flush mounted pressure transducers in the semispiral suction chamber and the volute casing of a double-suction pump, the pressure fluctuation signals were obtained and recorded at various operating conditions. Spectral analyses were performed on the pressure fluctuation signals in both frequency domain and time-frequency domain based on fast Fourier transform (FFT) and an adaptive optimal-kernel time-frequency representation (AOK TFR). The results show that pressure fluctuations at the impeller rotating frequency and some lower frequencies dominated in the semispiral suction chamber. Pressure fluctuations at the blade passing frequency, the impeller rotating frequency, and their harmonic frequencies were identified in the volute casing. The amplitude of pressure fluctuation at the blade passing frequency significantly increased when the flow rate deviated from the design flow rate. At 107% of the design flow rate, the amplitude increased more than 254% than that at the design flow rate. The time-frequency characteristics of these pressure fluctuations were affected greatly by both operating conditions and measurement locations. At partial flow rates the pulsation had a great irregularity and the amplitudes at the investigated frequencies were much larger than ones at the design flow rate. An asymmetrical pressure fluctuation structure in the volute casing was observed at all flow rates. The pulsation behavior at the blade passing frequency was the most prominent near the volute tongue zone, and the pressure waves propagated in both the radial and circumferential directions.

Influence of Pressure Fluctuation on Reflux Valve in a Self-Priming Pump With Outer Recirculation

2010 ◽  
Author(s):  
Hong Li ◽  
Zhenhua Shen ◽  
Jianrui Liu ◽  
Chao Wang
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Difference ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Element Analysis ◽  
Turbulence Flow ◽  
The Finite Element Analysis ◽  
Priming Process ◽  
The Stability

The pressure fluctuation caused by impeller-volute interaction is one of the factors which affect the stability of self-priming pump with outer recirculation. Based on the RNG k–ε turbulence model, three-dimensional unsteady turbulence flow in a self-priming pump was simulated in this paper. Pressure fluctuations were obtained at 26 monitor points distributed at eight sections of the volute and on the reflux valve, and the influence on the valve was analyzed. The CFD results show that the main frequency of monitor points is blade passing frequency, and the pressure difference between maximum and average is minimal at the fifth section, which is 1.3%∼2.4%. Using pressure sensors and LabVIEW system, the pressures at third, fifth and seventh sections were tested. The experimental results show that pressure fluctuation layouts are similar as those from CFD, and the pressure difference at the fifth section is 4%, also the minimum. The position also is found with minimal influence on reflux valve. Reflux hole should be placed at 200° ∼ 220° from the tongue along the direction of the impeller rotation. Further, according to the CFD results, the Finite Element Analysis (FEA) of the reflux valve was carried out. FEA shows that the valve can close the reflux hole completely after self-priming process, which gets a good hydraulic performance when the pump runs normally.

Experimental Investigation of Relationship Between Pressure Fluctuations and Vibrations for a Double Suction Centrifugal Pump

2011 ◽  
Author(s):  
Zhifeng Yao ◽  
Fujun Wang ◽  
Ruofu Xiao ◽  
Chenglian He ◽  
Zhuqing Liu
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Pressure Fluctuations ◽  
Primary Source ◽  
Internal Flow ◽  
Rotational Frequency ◽  
High Flow ◽  
High Flow Rate ◽  
Centrifugal Pumps ◽  
Blade Passing Frequency

Double-suction centrifugal pumps are widely employed in large-scale pumping stations, which generally run in the conditions of large discharge with huge energy consumption. Pressure fluctuation caused by internal flow due to tongue-impeller interaction is the primary source of pump vibration. In this paper, pressure fluctuations and vibrations signals on volute casing wall were experimentally obtained at five flow rates ranging from 59% to 121% of nominal flow rate. Time and frequency domains of the signals were mainly analyzed by using statistical and fast Fourier transform methods. The results show that rotational frequency, blade passing frequency and their harmonic frequencies of pressure fluctuations as well as vibrations are clearly identified. The magnitude at blade passing frequency has close relationship with the measurement location related to the volute tongue, and becomes larger when the flow rate deviates from the nominal flow rate. The magnitudes at blade passing frequency can increase by 70% and 151% at high flow rate over that at the nominal flow rate for pressure fluctuations and vibrations, respectively. While the magnitude of vibration at rotational frequency keeps nearly constant at partial flow rate, and decreases at high flow rate.

Dynamic Characteristics of Centrifugal Fan Impeller Based on Fluid-Solid Coupling

2012 ◽  
Vol 580 ◽  
pp. 437-440
Author(s):  
Mei Liu
Keyword(s):  
Unsteady Flow ◽  
Modal Analysis ◽  
Fatigue Failure ◽  
Dynamic Characteristics ◽  
Pressure Fluctuation ◽  
Natural Frequencies ◽  
Air Pressure ◽  
Centrifugal Fan ◽  
Main Frequency ◽  
Blade Passing Frequency

The non pre-stressing and pre-stressing modal analysis for impeller were computed by software ANSYS, and the unsteady flow for centrifugal fan was simulated by software CFX, at the same time the air pressure around the impeller was obtained. The results show that, the pre-stressing effect will improve the values of natural frequencies of impeller, but the increased values of the natural frequencies are different, the main frequency of air pressure fluctuation around the impeller is equal to the blade passing frequency of impeller, and it will not caused the danger of fatigue failure of impeller.

Flow in a Centrifugal Fan Impeller at Off-Design Conditions

1984 ◽  
Vol 106 (4) ◽  
pp. 913-919 ◽  
Author(s):  
T. Wright ◽  
K. T. S. Tzou ◽  
S. Madhavan
Keyword(s):  
Three Dimensional ◽  
Internal Flow ◽  
Design Flow ◽  
Experimental Results ◽  
Surface Velocity ◽  
Scale Model ◽  
Valuable Insight ◽  
Centrifugal Fan ◽  
Viscous Effects ◽  
Element Analysis

Predicted and measured surface velocity and pressure distributions in the internal flow channels of a centrifugal fan impeller are presented for volume flow rates between 80 and 125 percent of design flow rate. Predictions are based on a fully three-dimensional, finite element analysis of the inviscid, incompressible blade channel flow. Additional predictions using a conventional quasi-three-dimensional analysis are presented for comparison. Experimental results were developed using extensive blade and sidewall surface pressure taps installed in a scale model of an airfoil-bladed centrifugal fan impeller designed for heavy industrial and power generation applications. The results illustrate the ability of both flow analyses to predict the dominant features of the impeller flow field, including peak blade surface velocities and adverse gradients at flows far from the design point. In addition, the experimental results provide valuable insight into the limiting channel diffusion values for typical centrifugal cascade performance, and the influence of viscous effects as seen in deviations from the ideal flow predictions.

Flow instability in a volute-free centrifugal fan subjected to non-axisymmetric pre-swirl flow from upstream bended inflow tube

2021 ◽  
pp. 095765092110626
Author(s):  
Zhengfeng Liu ◽  
Hui Yang ◽  
Haijiang He ◽  
Peiquan Yu ◽  
Yikun Wei ◽  
...  
Keyword(s):  
Static Pressure ◽  
Flow Instability ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Internal Flow ◽  
Temporal Variations ◽  
Swirl Flow ◽  
Incoming Flow ◽  
Centrifugal Fan ◽  
Local Flow

The characteristics of internal flow and performance of a centrifugal fan is greatly dependent on the inflow pattern. As the fan is subjected to incoming flow from an upstream tube, the size and geometry of the tube affect the three-dimensional motion of local flow and possibly degrades the aerodynamic performance of the fan. In this work, we performed a numerical investigation on the internal flow in a centrifugal fan subjected to incoming flow from an upstream bended inflow tube of various radii using the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) simulation approaches. The effects of the non-axisymmetric pre-swirl flow generated due to the curvature of the bended inflow tube are demonstrated by analyzing the internal flow characteristics of the fan, including the spatial distributions and temporal variations of pressure field and streamlines, pressure fluctuations in the upstream tube, the inflow and outflow sections of the impeller, and the circumferential distributions of velocity and pressure in the impeller. The numerical results reveal that as the inflow tube is curved with larger curvature (smaller radius of the bended section), the pre-swirl inflow is strong and deteriorates the static pressure rise and static pressure efficiency of the centrifugal fan more remarkably, and the circumferential non-uniformity of pressure and velocity distributions appears inside of the channels of the fan. As the radius of the bended section increases, the instability of the internal flow gets more pronounced, as represented by the stronger pressure fluctuations at the inflow and outflow sections. The prediction capabilities of RANS and URANS approaches are also analyzed based on the numerical data and we found that the latter is more reliable in predicting the performance of the fan.

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