Experimental and numerical investigation of the unsteady flow field and tone generation in an isolated centrifugal fan impeller

2010 ◽  
Vol 329 (21) ◽  
pp. 4380-4397 ◽  
Author(s):  
Daniel Wolfram ◽  
Thomas H. Carolus
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Investigation ◽  
Centrifugal Fan ◽  
Tone Generation

Experimental and Numerical Investigation of the Unsteady Flow Field and Tone Generation in an Isolated Centrifugal Fan Impeller

2011 ◽  
Author(s):  
Daniel Wolfram ◽  
Thomas H. Carolus
Keyword(s):  
Unsteady Flow ◽  
Numerical Investigation ◽  
Vortex Core ◽  
Large Range ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Centrifugal Fan ◽  
Helical Vortex ◽  
The One ◽  
Tone Generation

In spite of low circumferential Mach number the sound of isolated centrifugal fan impellers is sometimes dominated by distinctive tones at blade passing frequency (BPF) and integer multiples. This paper reports on an experimental and numerical investigation intended to unveil the tone generating mechanism. The sound spectra from three impellers operating at a large range of speed were measured and decomposed into Strouhal and Helmholtz number dependent functions. This led to the preliminary conclusion that the BPF related tones are exclusively flow-induced. Based on hot-wire and blade pressure fluctuation measurements and a subsequent correlation analysis, coherent flow structures different from the one associated with the principal azimuthal flow pattern due to the blades were detected. Eventually, numerical three-dimensional unsteady flow simulation and experimental flow visualization revealed an inlet vortex. It takes on a helical form, with the vortex core slowly varying its position with respect to the impeller center. As the blades cut through that quasi-stationary helical vortex they encounter blade force fluctuations producing the BPF tones. The slow spin of the vortex core and the slow variation of vortex strength were identified as the reason for the amplitude modulation of the BPF tone.

scholarly journals NUMERICAL INVESTIGATION OF A TONE NOISE OF THE FAN WITH CASING TREATMENT

2021 ◽  
pp. 24-38
Author(s):  
Yaroslav Druzhinin ◽  
◽  
Viktor Mileshin ◽  
Anton Rossikhin ◽  
◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Investigation ◽  
Significant Influence ◽  
Aerodynamic Characteristics ◽  
Operational Conditions ◽  
Casing Treatment ◽  
Harmonic Method ◽  
Surge Line ◽  
Bypass Ratio

Numerical investigation of influence of a slot-type casing treatment on acoustic and aerodynamic characteristics of the fan of ultra-high bypass ratio turbofan is presented. The investigation was performed using NUMECA FINE/Turbo solver. NLH harmonic method was used to simulate the effect of casing treatment on unsteady flow field in the turbomachine. Two operational conditions were investigated – “sideline” and “approach”. The attention for the first operational condition was paid for aerodynamic characteristics. Significant influence of casing treatment on them was found especially near the surge line. At the “approach” operational conditions the attention was paid for the proper calculation of tone noise. It was shown that the installation of casing treatment leads to decrease of power of tone noise radiated through the inlet. However the power of the tone noise, radiated through the nozzle, and also the overall power of tone noise increase.

Analysis of Stator-Stator Clocking in a Transonic Turbine

2007 ◽  
Author(s):  
N. Billiard ◽  
V. Jerez Fidalgo ◽  
R. De´nos ◽  
G. Paniagua
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Investigation ◽  
Time Resolved ◽  
Relative Pitch ◽  
Shock System ◽  
Transonic Turbine ◽  
Mechanisms Of Migration

Clocking, i.e. the relative pitch-wise positioning between two successive vanes with the same amount of airfoils, has been demonstrated to bring potential aero-thermal benefits in several recent studies. Indeed, across a vane pitch, a variation of both time-averaged and time-resolved quantities is induced. In order to advance the knowledge on clocking, this 2D numerical investigation proposes a complete description of the unsteady flow field at midspan in a one and half stage turbine at four clocking positions. Mechanisms of migration across the rotor of the first vane wake and its interaction with the second vane has been put into evidence. Additionally, the behavior of the shock system between the rotor and the second stator is assessed indicating effects due to the clocking, like the similar the shape of the shock system when rotor/2nd stator are in the same relative positions.

Numerical Model for the Unsteady Flow Features of a Squirrel Cage Fan

2009 ◽  
Author(s):  
Rafael Ballesteros-Tajadura ◽  
Francisco Israel Guerras Colo´n ◽  
Sandra Velarde-Sua´rez ◽  
Jesu´s Manuel Ferna´ndez Oro ◽  
Katia Mari´a Argu¨elles Di´az ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Flow Distribution ◽  
Experimental Tests ◽  
Centrifugal Fan ◽  
Flow Rates ◽  
Squirrel Cage ◽  
Flow Features ◽  
Separation Zones

This paper shows a numerical research on the unsteady flow field inside a squirrel cage fan. The studied features are both the instantaneous flow fields and the average fluid flow associated to the blade passage frequency. The squirrel cage fan studied is a small centrifugal fan with a twin impeller configuration, each with 23 forward curved blades. The blades chord is 0.013 m and each impeller has a diameter of 0.08 m and a width of 0.094 m. The impellers operate inside an external spiral casing with a rectangular exit, followed by the outlet duct. A first series of experimental tests were performed in order to characterize the unit. The performance curves (head, power and efficiency versus flow rate) were measured. These tests show a nominal flow rate at around 0.098 m3/s and a specific speed ωs = 1.9. From there on, three different flow rates were considered to study different flow behaviours in the impeller. In parallel with the mentioned experimental study, the unsteady 3D flow field inside the fan equipped with the same impeller was modelled for the referred flow rates, by means of the commercial CFD code FLUENT. To facilitate the modification of any geometrical feature, the mesh of the modelled fan was divided in several regions: inlet duct, impeller, volute and diffuser with outlet duct. The main goal of the paper is to show the numerical results obtained on the absolute and relative frames. Three main flow features will be analysed: the inlet flow distribution, the blade to blade field and the impeller exit flow. At the fan inlet, special care will be taken to detect possible recirculation or separation zones. On the other hand, and for each studied flow rate, the distribution of outlet flow field is also analysed. Conclusions on flow uniformity are drawn.

scholarly journals Numerical Investigation of Flow Field Near the Exhaust Opening Indoor

2019 ◽  
Vol 267 ◽  
pp. 032081
Author(s):  
Chanjun Meng ◽  
Bo Yuan ◽  
Chuan He ◽  
Chunfu Xi ◽  
Liangming Pan
Keyword(s):  
Flow Field ◽  
Numerical Investigation

Modal characteristics and fluid–structure interaction vibration response of submerged impeller

2021 ◽  
pp. 107754632110036
Author(s):  
Shihui Huo ◽  
Hong Huang ◽  
Daoqiong Huang ◽  
Zhanyi Liu ◽  
Hui Chen
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Damping Ratio ◽  
Pure Water ◽  
Vibration Response ◽  
Modal Identification ◽  
Liquid Oxygen ◽  
Modal Characteristics ◽  
Oxygen Pump ◽  
Turbo Pump

Turbo pump is one of the elements with the most complex flow of liquid rocket engine, and as an important component of turbo pump, an impeller is the weak point affecting its reliability. In this study, a noncontact modal characteristic identification technique was proposed for the liquid oxygen pump impeller. Modal characteristics of the impeller under three different submerged media, air, pure water, and brine with same density as liquid oxygen, were tested based on the noncontact modal identification technology. Submersion state directly affects the modal frequencies and damping ratio. The transient vibration response characteristics of the impeller excited by the unsteady flow field was achieved combining with unsteady flow field analysis and transient dynamic analysis in the whole flow passage of the liquid oxygen pump. Vibration responses at different positions of the impeller show 10X and 20X frequencies, and the amplitude at the root of short blade is significant, which needs to be paid more attention in structural design and fatigue evaluation.

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