The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Jae Hyuk Jung - One of the best experts on this subject based on the ideXlab platform.
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effect of tip clearance winglets and shroud height on the tip leakage in Axial Flow Fans
International Journal of Refrigeration-revue Internationale Du Froid, 2018Co-Authors: Jae Hyuk JungAbstract:Abstract This study is concerned with the improvement in efficiency of Axial Flow Fans that are being used in numerous fields including outdoor units of air conditioners. The tip leakage Flow occurring between a blade tip and shroud is one of the major losses in the Axial Flow Fan. A well-known method used to control such tip leakage Flow is locating winglet on the suction side of blade tips. Only a few articles have studied the impact of tip clearance on the Flow structure of tip leakage Flow of Axial Flow Fans with winglet. In this study, the Flow structure occurring on the blade tip due to the location of a winglet was analyzed. We confirm the existence of an optimal tip clearance which results in the maximum efficiency for an Axial Flow Fan with a shroud height measuring 30% of the Axial chord length.
Abd A Elazim - One of the best experts on this subject based on the ideXlab platform.
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simulation of a transonic Axial Flow Fan of a high bypass ratio turboFan engine during flight conditions
International Review of Aerospace Engineering, 2014Co-Authors: H. Z. Hassan, M H Gobran, Abd A ElazimAbstract:In the present work, the three dimensional (3-D) Flow field through the transonic Axial Flow Fan and the intake of the CF6-50 high bypass ratio turboFan engine is investigated under the flight cruise conditions (11000 meter altitude and 0.85 Mach number). The Fan in concern has a large diameter, about 2.18 m. The Fan blade is tapered, highly twisted, and has a long span, about 0.65 m, with a low hub to tip ratio, about 0.4. The actual dimensions of both the Fan and its intake are used in the present simulation. Moreover, the steady, compressible, turbulent, and viscous 3-D air Flow field in both the intake and Fan is solved and investigated. The computational domain is a periodic sector of an angle (360/38) through both the Fan and the intake zones. At the design speed and pressure ratio, slight deviations of the efficiency, about 1.27%, and mass Flow rate, about 1%, compared with those listed in the engine manual are obtained by the simulation. Furthermore, results of simulation show shock waves formed in the passage at the trailing edge of the suction side and propagate towards the opposite blade pressure side for the outer third of blade span.
Thomas Carolus - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation of acoustical sources in a low pressure Axial Flow Fan encountering highly turbulent inFlow
Journal of Fluids Engineering-transactions of The Asme, 2007Co-Authors: Hauke Reese, Chisachi Kato, Thomas CarolusAbstract:A large eddy simulation (LES) was applied to predict the unsteady Flow in a low-speed Axial-Flow Fan assembly subjected to a highly “turbulent” inFlow that is generated by a turbulence grid placed upstream of the impeller. The dynamic Smagorinsky model (DSM) was used as the subgrid scale (SGS) model. A streamwise-upwind finite element method (FEM) with second-order accuracy in both time and space was applied as the discretization method together with a multi-frame of reference dynamic overset grid in order to take into account the effects of the blade-wake interactions. Based on a simple algebraic acoustical model for Axial Flow Fans, the radiated sound power was also predicted by using the computed fluctuations in the blade force. The predicted turbulence intensity and its length scale downstream of the turbulence grid quantitatively agree with the experimental data measured by a hot-wire anemometry. The response of the blade to the inFlow turbulence is also well predicted by the present LES in terms of the surface pressure fluctuations near the leading edge of the blade and the resulting sound power level. However, as soon as the effects of the turbulent boundary layer on the blades become important, the prediction tends to become inaccurate.
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Axial Flow Fan broad band noise and prediction
Journal of Sound and Vibration, 2007Co-Authors: Thomas Carolus, Marc Schneide, Hauke ReeseAbstract:Abstract Two prediction methods for broad-band noise of low-pressure Axial Fans are investigated. Emphasis is put on the interaction noise due to ingested turbulence. The numerical large eddy simulation (LES) is applied to predict the unsteady blade forces due to grid generated highly turbulent inFlow; the blade forces are then fed into an analytical two-dimensional acoustic ducted source model. A simple semi-empirical noise prediction model (SEM) is utilized for indicative comparison. Finally, to obtain a database for detailed verification, the turbulence statistics for a variety of different inFlow configurations are determined experimentally using hot wire anemometry and a correlation analysis. In the limits of the necessary assumptions the SEM predicts the noise spectra and the overall sound power surprisingly well without any further tuning of parameters; the influence of the Fan operating point and the nature of the inFlow is obtained. Naturally, the predicted spectra appear unrealistically “smooth”, since the empirical input data are averaged and modeled in the frequency domain. By way of contrast the LES yields the fluctuating forces on the blades in the time domain. Details of the source characteristics and their origin are obtained rather clearly. The predicted effects of the ingested turbulence on the fluctuating blade forces and the Fan noise compare favorably with experiments. However, the choice of the numerical grid size determines the maximal resolvable frequency and the computational cost. As contrasted with the SEM, the cost for the LES-based method are immense.
H J Myung - One of the best experts on this subject based on the ideXlab platform.
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structure of tip leakage Flow in a forward swept Axial Flow Fan
Flow Turbulence and Combustion, 2003Co-Authors: Gong Hee Lee, Je Hyu Aek, H J MyungAbstract:An experimental analysis using three-dimensional laser Dopplervelocimetery (LDV) measurements and computational analysis usingthe Reynolds stress model of the commercial code, FLUENT, wereconducted to give a clear understanding on the structure of thetip leakage Flow in a forward-swept Axial-Flow Fan operating atthe peak efficiency condition, and to emphasize the necessity ofusing an anisotropic turbulence model for the accurate predictionof the tip leakage vortex. The rolling-up of the tip leakage Flowwas initiated near the position of the maximum static pressuredifference, which was located at approximately 12% Axial tipchord downstream from the leading edge of the blade, and developedalong the centerline of the pressure trough on the casing. Areverse Flow between the blade tip and the casing due to the tipleakage vortex acted as a blockage on the through-Flow. As aresult, high momentum flux was observed below the tip leakagevortex. As the tip leakage vortex proceeded to the aft part of theblade passage, the strength of the tip leakage vortex decreaseddue to the strong interaction with the through-Flow and the casingboundary layer, and the diffusion of the tip leakage vortex byhigh turbulence. Through the comparative study of turbulencemodels, it was clearly shown that an anisotropic turbulence model,e.g., Reynolds stress model, should be used to predict reasonablyan anisotropic nature of the turbulent Flow fields inside the tipleakage vortex. In comparison with LDV measurement data, thecomputed results predicted the complex viscous Flow patternsinside the tip region in a reliable level.
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mean velocity characteristics behind a forward swept Axial Flow Fan
Jsme International Journal Series B-fluids and Thermal Engineering, 1999Co-Authors: H J Myung, J H BaekAbstract:Detailed measurements in the Flow behind a highly forward-swept Axial-Flow Fan at three operating conditions were performed using three-dimensional LDV system. Various phenomena related to the leakage Flow, leakage vortex, hub vortex and wake were investigated. At the design condition, where no distinct leakage vortex appears behind trailing edge, the leakage Flow interacts with the boundary layer of the pressure side inside the blade passage, which directly influence the wake characteristics behind the trailing edge. At the low loading condition, the leakage vortex has the characteristics of the velocity defect and this vortex induces radially inward Flows at both the suction and pressure sides in the wake near the tip region. As the loading increases, radially-outward velocity component increases and the position of the maximum value in the wake is closer to the tip region. At the design and high loading condition, hub vortex induces radially inward Flow at the pressure side and wakes near the hub region decays very quickly due to the interaction with the large hub vortex.
H. Z. Hassan - One of the best experts on this subject based on the ideXlab platform.
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simulation of a transonic Axial Flow Fan of a high bypass ratio turboFan engine during flight conditions
International Review of Aerospace Engineering, 2014Co-Authors: H. Z. Hassan, M H Gobran, Abd A ElazimAbstract:In the present work, the three dimensional (3-D) Flow field through the transonic Axial Flow Fan and the intake of the CF6-50 high bypass ratio turboFan engine is investigated under the flight cruise conditions (11000 meter altitude and 0.85 Mach number). The Fan in concern has a large diameter, about 2.18 m. The Fan blade is tapered, highly twisted, and has a long span, about 0.65 m, with a low hub to tip ratio, about 0.4. The actual dimensions of both the Fan and its intake are used in the present simulation. Moreover, the steady, compressible, turbulent, and viscous 3-D air Flow field in both the intake and Fan is solved and investigated. The computational domain is a periodic sector of an angle (360/38) through both the Fan and the intake zones. At the design speed and pressure ratio, slight deviations of the efficiency, about 1.27%, and mass Flow rate, about 1%, compared with those listed in the engine manual are obtained by the simulation. Furthermore, results of simulation show shock waves formed in the passage at the trailing edge of the suction side and propagate towards the opposite blade pressure side for the outer third of blade span.
