Fan Impeller

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Thomas Carolus - One of the best experts on this subject based on the ideXlab platform.

  • experimental and numerical investigation of tip clearance noise of an axial Fan using a lattice boltzmann method
    2014
    Co-Authors: Michael Sturm, Thomas Carolus, Barbara Neuhierl, Franck Perot
    Abstract:

    The secondary flow through the tip clearance is one of the well-known sources contributing to the overall noise of axial Fans. Aerodynamic losses and sound radiation increase significantly as the tip clearance is increased. The objective of this study is to revisit the mechanisms for tip clearance noise from a rotating Fan Impeller. The unsteady and compressible numerical Lattice-Boltzmann-Method (LBM) is utilized which allows a direct and simultaneous prediction of both aerodynamic and acoustic field. Overall aerodynamic and acoustic Fan performance data as predicted with the LBM were validated with experimental data. The agreement was quite satisfactory which justified looking at the LBM-predicted field data in detail. The flow and acoustic field in the vicinity of an axial Fan Impeller's tip gap revealed important details of the sound generating mechanism. A large tip clearance is responsible for a complex vortex system with a considerable degree of inherent unsteadiness. The consequences are fluctuations of static pressure in the flow field in the adjacent tip region and on the blade surfaces, more pronounced on the pressure than on the suction side. Those pressure fluctuations generate sound that is then radiated away from the complete Impeller upstream into the free field with the typical hemispherical directivity pattern.

  • Experimental and Numerical Investigation of the Unsteady Flow Field and Tone Generation in an Isolated Centrifugal Fan Impeller
    Volume 4: Cycle Innovations; Fans and Blowers; Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine; Oil and Gas Applications, 2011
    Co-Authors: Daniel Wolfram, Thomas Carolus
    Abstract:

    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.Copyright © 2011 by ASME

  • Experimental and numerical investigation of the unsteady flow field and tone generation in an isolated centrifugal Fan Impeller
    Journal of Sound and Vibration, 2010
    Co-Authors: Daniel Wolfram, Thomas Carolus
    Abstract:

    In spite of a 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 those associated with the principal azimuthal flow pattern due to the blades were detected. Eventually a numerical three-dimensional unsteady flow simulation 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. Slow spin of the vortex core and slow variation of vortex strength were identified as the reasons for amplitude modulation of the BPF tone.

N. A. Popov - One of the best experts on this subject based on the ideXlab platform.

Douglas D. Reynolds - One of the best experts on this subject based on the ideXlab platform.

Ismail Calli - One of the best experts on this subject based on the ideXlab platform.

  • Tip Clearance Effects in Radial Flow Impeller Fans Under High Temperature Working Conditions
    Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001
    Co-Authors: Mesut Gur, Tahsin Engin, Ismail Calli
    Abstract:

    Three industrial-type centrifugal Fans were designed, fabricated and tested in order to investigate the effects of axial (tip) clearance between an unshrouded Impeller and stationary casing, so that the flow field behavior may differ considerable from that of a shrouded centrifugal Fan Impeller. Tests were conducted under high temperatures of gas up to 1000 °C at six different values of tip clearance each. Test results showed that the tip leakage flow due to the tip clearance is an unavoidable factor, which deteriorates the Fan performance, and therefore the Impeller geometry should be designed considering the tip clearance losses.Copyright © 2001 by ASME

Songling Wang - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of Strength in G4-73 Type Centrifugal Fan Impeller
    2016
    Co-Authors: Songling Wang, Zhe Sun
    Abstract:

    Keywords- finite element method; Impeller; stress Abstract. For the large centrifugal Fan Impeller, its working condition generally is bad, and its geometry generally is complex. So its displacements and stresses distribution are also complex. In this paper, we can obtain the Fan Impeller’s displacements and stresses distribution accurately through numerical simulation in G4-73 type centrifugal Fan Impeller using the finite element method software ANSYS. The calculation result shows that the maximum total displacement of the Impeller is 310303.0 − × m, it occurs on the position of the half of the blade near the outlet of the Impeller; and the maximum equivalent stress of the Impeller is 193 MPa, it occurs on the contacted position of the blade and the shroud near inlet of the Impeller. Furthermore, check the Impeller strength, the result shows that the strength of the Impeller can meet the requirement

  • Investigation of Strength in G4-73 Type Centrifugal Fan Impeller
    Advanced Materials Research, 2011
    Co-Authors: Songling Wang, Zhe Sun
    Abstract:

    For the large centrifugal Fan Impeller, its working condition generally is bad, and its geometry generally is complex. So its displacements and stresses distribution are also complex. In this paper, we can obtain the Fan Impeller’s displacements and stresses distribution accurately through numerical simulation in G4-73 type centrifugal Fan Impeller using the finite element method software ANSYS. The calculation result shows that the maximum total displacement of the Impeller is m, it occurs on the position of the half of the blade near the outlet of the Impeller; and the maximum equivalent stress of the Impeller is 193 MPa, it occurs on the contacted position of the blade and the shroud near inlet of the Impeller. Furthermore, check the Impeller strength, the result shows that the strength of the Impeller can meet the requirement.

  • Optimization Research of Centrifugal Fan with Different Blade Number and Outlet Blade Angle
    2009 Asia-Pacific Power and Energy Engineering Conference, 2009
    Co-Authors: Songling Wang, Zhengren Wu, Hongwei Qian
    Abstract:

    The characteristics of the three-dimension flow field of the G4-73 centrifugal Fan were numerically simulated based on the k e − turbulence model with the Fluent, and then verified the simulating result by experiment. Taking the efficiency η maximizing as a function goal, while the blade number and the angle of blade outlet as the variable quantities, the Fan Impeller parameters are optimized based on least squares method. The optimizing results showed that the performance of centrifugal Fan was improved by lowering the energy loss which caused by the secondary flow vortex, the volute tongue, the wake-jet and the angle of attack. After the optimization, the total pressure and efficiency increased 3.7% and 0.5% respectively. Total pressure and efficiency are important parameters of Fan performance. In deduction of the energy equation for centrifugal Fan, one of the assumption is that the Impeller has unlimited blade. In fact, the blade number is always limited, which results in lower total pressure. Slip factor reflect the influence of limited blade on theoretical total pressure. The results show that the slip factor relate to the number of blade, the outlet blade angle, the ratio of inside diameter to outside diameter, the dynamic viscosity of the fluid and the runner's surface roughness(2). Therefore, the number of Fan blades and the size of the outlet blade angle directly impact on the Fan performance, but it is still difficult to calculate it by theoretical methods(3-4). Cheng xinde studied the selection of the number of the forward-curved blade by experiments, and few papers did research on the impact of blade number and the size of the outlet blade angle on the performance of Fan by numerical method. This paper will use the software of Fluent to calculate the total pressure and efficiency of centrifugal Fans with different blade numbers and blade outlet angles, and optimize the Fan for a higher efficiency based on the least square method.

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