scholarly journals Rotor Tip Flow-Field near Inception Point of Modal Disturbance in an Axial-Flow Fan(Fluids Engineering)

2010 ◽  
Vol 76 (771) ◽  
pp. 1712-1719
Author(s):  
Takahiro NISHIOKA ◽  
Toshio KANNO
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Axial Flow Fan ◽  
Inception Point

The Design of a Large Diameter Axial Flow Fan for Air-Cooled Heat Exchanger Applications

2017 ◽  
Author(s):  
Michael B. Wilkinson ◽  
Johan van der Spuy ◽  
Theodor W. von Backström
Keyword(s):  
Flow Field ◽  
Large Diameter ◽  
Axial Flow ◽  
Pressure Rise ◽  
Design Procedure ◽  
Axial Flow Fan ◽  
Disk Model ◽  
Actuator Disk ◽  
Static Efficiency ◽  
Air Cooled Heat Exchanger

An axial flow fan design methodology is developed to design large diameter, low pressure rise, rotor-only fans for large air-cooled heat exchangers. The procedure aims to design highly efficient axial flow fans that perform well when subjected to off design conditions commonly encountered in air-cooled heat exchangers. The procedure makes use of several optimisation steps in order to achieve this. These steps include optimising the hub-tip ratio, vortex distribution, blading and aerofoil camber distributions in order to attain maximum total-to-static efficiency at the design point. In order to validate the design procedure a 24 ft, 8 bladed axial flow fan is designed to the specifications required for an air-cooled heat exchanger for a concentrated solar power (CSP) plant. The designed fan is numerically evaluated using both a modified version of the actuator disk model and a three dimensional periodic fan blade model. The results of these CFD simulations are used to evaluate the design procedure by comparing the fan performance characteristic data to the design specification and values calculated by the design code. The flow field directly down stream of the fan is also analysed in order to evaluate how closely the numerically predicted flow field matches the designed flow field, as well as determine whether the assumptions made in the design procedure are reasonable. The fan is found to meet the required pressure rise, however the fan total-to-static efficiency is found to be lower than estimated during the design process. The actuator disk model is found to under estimate the power consumption of the fan, however the actuator disk model does provide a reasonable estimate of the exit flow conditions as well as the total-to-static pressure characteristic of the fan.

scholarly journals Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

2014 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Axial Flow Fan ◽  
Free Vortex ◽  
Flow Rates

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

Experimental Investigation of Tip Clearance Flows of an Axial Flow Fan Using PDA

2002 ◽  
Author(s):  
Xiaocheng Zhu ◽  
Wanlai Lin ◽  
Zhaohui Du ◽  
Yan Zhao
Keyword(s):  
Flow Field ◽  
Reverse Flow ◽  
Axial Flow ◽  
Tip Clearance ◽  
Measurement Technology ◽  
Dynamics Modeling ◽  
Tip Leakage Flow ◽  
Axial Flow Fan ◽  
Tip Leakage Vortex ◽  
Tip Leakage

The three-dimensional flow field in the tip region of an isolated axial flow fan rotor with two different tip clearances are investigated using a three-color, dual-beam PDA system (Particle Doppler Anemometer, DANTEC Measurement Technology). The global performance is also obtained, and is compared favorably with CFD (Computational Fluid Dynamics) modeling of this fan flow at a zero tip clearance. The detailed flow field measurements are taken at 15 axial locations upstream, inside and at the exit of the rotor. In the radial direction, 15 measurement locations are arranged from 50% of the blade span to the casing wall, mainly focusing on the tip region from 90% of the blade span location to the casing wall (about 10 measurement locations). The PDA data has provided a quantitative understanding of the flow phenomena in the tip region of the fan rotor. For both tip clearances, it has been observed that the tip leakage flow rolls up into a tip leakage vortex. Due to the rotation of the rotor, this tip leakage vortex moves away from the suction surface of the fan blade. A reverse flow is induced in the main flow passage because of the tip leakage vortex. The depth and extent of the tip leakage vortex grow noticeably with the increase of the tip clearance.

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