Influence of Design Parameters on the Unsteady Flow in a Centrifugal Fan

2007 ◽  
Author(s):  
M. Younsi ◽  
F. Bakir ◽  
S. Kouidri ◽  
R. Rey
Keyword(s):  
Unsteady Flow ◽  
Acoustic Pressure ◽  
Flow Behavior ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Far Field ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations

The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental study has been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these fans. The effects on the unsteady flow behavior related to irregular blade spacing, blade number and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using Computational Fluid Dynamics tools (CFD) based on Unsteady Reynolds Averaged Navier Stokes approach (URANS). The sliding mesh technique has been applied at the interfaces between the rotating and stationary zones in order to model the blades’ motion relative to the volute casing. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations (pressure and velocity fluctuations acquired upon the surfaces of the rotating blades) have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). Using this model, the acoustic pressure has been computed at the fan exit duct. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 [1] standard. In addition to this, pressure microphones have been flush-mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.

scholarly journals Influence of Impeller Geometry on the Unsteady Flow in a Centrifugal Fan: Numerical and Experimental Analyses

2007 ◽  
Vol 2007 ◽  
pp. 1-10 ◽  
Author(s):  
M. Younsi ◽  
F. Bakir ◽  
S. Kouidri ◽  
R. Rey
Keyword(s):  
Unsteady Flow ◽  
Flow Behavior ◽  
Pressure Fluctuations ◽  
Radial Distance ◽  
Wall Pressure ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Far Field ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations

The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental studies have been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these impellers. The effects on the unsteady flow behavior related to irregular blade spacing, blade count and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using computational fluid dynamics (CFD) tools based on the unsteady Reynolds averaged Navier Stokes (URANS) approach. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 (1997) standard. In addition to this, pressure microphones have been flush mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.

An experimental investigation of turbulent flow over a two-dimensional obstacle on a flat plate

2021 ◽  
Vol 263 (2) ◽  
pp. 4459-4470
Author(s):  
Shivam Sundeep ◽  
Xin Zhang ◽  
Siyang Zhong ◽  
Huanxian Bu
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Far Field ◽  
Two Dimensional ◽  
Vortical Structures ◽  
Wall Pressure Fluctuations ◽  
Field Noise ◽  
Velocity Spectra

Aeroacoustic and aerodynamic characteristics of the turbulent boundary layer encountering a large obstacle are experimentally investigated in this paper. Two-dimensional obstacles with a square and a semi-circular cross-section mounted on a flat plate are studied in wind tunnel tests, with particular interests in the shear layer characteristics, wall pressure fluctuations, and far-field noise induced by the obstacles. Synchronized measurements of the far-field noise and the wall pressure fluctuations were conducted using microphone arrays in the far-field and flush-mounted in the plate, respectively. Additionally, the streamwise and wall-normal velocity fluctuations behind the obstacle were measured using the X-wire probe. The measured velocity profiles, spectra, and wall pressure spectra are compared, showing that the rectangular obstacle has a significant impact on both the turbulent flow and far-field noise. The large-scale vortical structures shed from the obstacles can be identified in the wall pressure spectra, the streamwise velocity spectra, and the wall pressure coherence analysis. Within the shear layer, the pairing of vortices occurs and the frequency of the broadband peak in the velocity spectra decreases as the shear layer grows downstream. Further eddy convective velocities of large-scale vortical structures inside the shear layer were analyzed based on the wall pressure fluctuations.

Numerical Calculation of Wall Pressure Fluctuations in a Centrifugal Fan

2004 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Wall Pressure ◽  
Operating Conditions ◽  
Numerical Code ◽  
Experimental Investigations ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Flow Phenomena

In this work, a numerical code has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been contrasted using previous experimental investigations carried out in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been calculated, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. The code has successfully simulated the volute pressure fluctuations due to the aerodynamic field, capturing the main flow phenomena such as the jet-wake effects and the impeller-volute interaction.

scholarly journals Influence of Design Parameters on the Global Performances of Low-Speed Counter-Rotating Axial-Flow Fans

2014 ◽  
Author(s):  
Juan Wang ◽  
Florent Ravelet ◽  
Farid Bakir
Keyword(s):  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Design Flow ◽  
Design Parameters ◽  
Speed Ratio ◽  
Axial Distance ◽  
Design Point ◽  
Static Efficiency ◽  
Rotating Systems ◽  
Wall Pressure Fluctuations

The present work aims at experimentally investigating the effects of some parameters on the performances of a counter-rotating stage, and on the instationary flow between the rotors. Three counter-rotating fans, which have the same design point, have been designed. These systems differ by the distribution of the loading and of the ratio of angular velocity between the front rotor and the rear rotor. All the configurations have been tested in a normalized test rig, where the ratio of angular velocities and the axial distance between the two rotors can be varied. The influence of these parameters are then addressed by analysing the experimental results of the static pressure rise and static efficiency, as well as of the wall pressure fluctuations registered by a microphone at the wall. The three systems achieve the design point with a high efficiency. The counter-rotating systems lead to at least a 10 percentage points gain in static efficiency at the design flow rate, compared to the typical peak efficiency of a traditional rotor-stator stage. Meanwhile, counter-rotating systems display good working stabilities at very low volume flow rates. In addition, at the design speed ratio, the overall performance decreases almost monotonically with the axial distance. Nevertheless, an optimum in axial distance can be found for higher speed ratios. Finally, the investigations of the wall pressure fluctuations show that the amplitudes of power spectral density corresponding to the blade passing frequency of the rear rotor are significantly higher than that of the front rotor. The interaction peaks are also stronger for an equal distribution of the work on the two rotors.

Numerical Investigation of Pressure Fluctuation on the Volute of a Backward Curved Blade Centrifugal Fan

2014 ◽  
Author(s):  
Jianhua Zhang ◽  
Wuli Chu ◽  
Yanhui Wu ◽  
Haoguang Zhang ◽  
Xingjie Dong
Keyword(s):  
Unsteady Flow ◽  
Large Scale ◽  
Second Harmonic ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Axial Position ◽  
Centrifugal Fan ◽  
Flow Rates ◽  
Wall Pressure Fluctuations ◽  
Blade Passing Frequency

The pressure fluctuations on the volute surface induced by internal unsteady flow are the important sources of fan casing vibration and noise generation. In this paper, a three-dimensional and unsteady flow of a whole impeller-volute structure have been carried out by using commercial CFX code in order to obtain the wall pressure fluctuations on the volute of a large scale centrifugal fan (especially in the vicinity of volute tongue). The two important different flow rates have been simulated, the best efficiency point (BEP) and 130 percent of the BEP (1.3 × BEP), multi-domain structure grids have been applied in all the domains of current simulations. The pressure fluctuations of setting locations on the volute have been obtained by this method. Characteristics of these fluctuations in time and frequency domains were mainly analyzed. The results showed that the amplitudes of these pressure fluctuations over the volute changed with the flow rates variation. The blade passing frequency and their second harmonic frequency were observed clearly, and an important peak presented at the blade passing frequency (BPF). The amplitude of BPF has related with the position of the volute. On the circumferential direction of the volute, the highest values appeared in the vicinity of volute tongue; on the axial position, the peak value was discovered near to impeller shrouds. All the calculation results have been compared to the experimental results showing a good agreement.

Numerical Simulation of Unsteady Flow and Flow Induced Sound of Airfoil and Wing/Plate Junction by LES and FW-H Acoustic Analogy

2013 ◽  
Vol 444-445 ◽  
pp. 479-485
Author(s):  
Nan Zhang ◽  
Shi Jin Lv ◽  
Hua Xie ◽  
Sheng Li Zhang
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Pressure Fluctuations ◽  
Water Channel ◽  
Wall Pressure ◽  
Acoustic Analogy ◽  
Eddy Simulation ◽  
Wall Pressure Fluctuations ◽  
Large Eddy

Numerical simulation of unsteady flow and flow-induced sound of an airfoil and a wing/plate junction are performed in the paper by large eddy simulation (LES) and FW-H acoustic analogy. The vortical flows around a NACA0015 airfoil at two angles of attack (0°and 8°) are simulated and analyzed by vortex identification. Simultaneously, the wall pressure fluctuations of the airfoil are computed. At two angles of attack, the flow induced sound of the airfoil is predicted. The computed power spectra agree well with experimental measurements. So the capability of large eddy simulation in predicting unsteady flow and flow induced sound is validated. Subsequently, the horse-shoe vortex around a wing/plate junction in water is computed. Furthermore, the calculations of wall pressure fluctuations and flow induced sound of the junction model at three velocities are accomplished. The predicted results are compared favorably with measured data in large circulation water channel. So the numerical approach for flow induced sound of wing/plate junction in water is validated. It shows that the numerical simulation method in the paper is credible.

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