A STUDY ON THE UNSTEADY FLOW FIELD AND AEROACOUSTIC NOISE OF AN AXIAL FLOW FAN

2017 ◽  
Vol 22 (2) ◽  
pp. 51-58
Author(s):  
W.H. Jeon ◽  
C.H. Park
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Axial Flow Fan ◽  
Aeroacoustic Noise

scholarly journals Measurements of the Unsteady Flow Field Within the Stator Row of a Transonic Axial-Flow Fan: I — Measurement and Analysis Technique

1987 ◽  
Author(s):  
K. L. Suder ◽  
T. H. Okiishi ◽  
M. D. Hathaway ◽  
A. J. Strazisar ◽  
J. J. Adamczyk
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Unsteady Flow ◽  
Stokes Equations ◽  
Axial Flow ◽  
Navier Stokes ◽  
Axial Flow Fan ◽  
Rotor Wake ◽  
Navier Stokes Equations ◽  
Measurement And Analysis

This two-part paper presents detailed laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective of this study was to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part I of this paper describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the “rotor-wake-generated” and “unresolved” unsteadiness, respectively. The term “rotor-wake-generated” unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term “unresolved” unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc. A procedure for calculating auto and cross correlations of the rotor-wake-generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

Large Eddy Simulation and Acoustical Analysis for Prediction of Aeroacoustics Noise Radiated From an Axial-Flow Fan

2006 ◽  
Author(s):  
Yoshinobu Yamade ◽  
Chisachi Kato ◽  
Hayato Shimizu ◽  
Takahiro Nishioka
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Rotor Blades ◽  
Coarse Mesh ◽  
Axial Flow Fan ◽  
Eddy Simulation ◽  
Fine Mesh ◽  
Large Eddy

A final objective of this study is to develop a tool to predict aeroacoustics noise radiated from a low-speed fan, and its reduction. Aeroacoustics noise that is radiated from a low-speed axial flow fan, with a six-blades rotor installed in a casing duct, is predicted by an one-way coupled analysis of the computation of the unsteady flow in the ducted fan and computation of the sound radiated to the ambient air. The former is performed by our original code, FrontFlow/blue, which is based on Large Eddy Simulation (LES). The latter is performed by using a commercial code, SYSNOISE, which computes the sound fields in the frequency domain. The following three cases of computations are performed for LES with different flow field configurations and/or grid resolutions: a coarse mesh without the struts located, in the actual fan, upstream of the rotor blades, a fine mesh without the struts, and a coarse mesh with the struts. The first two test cases are intended to investigate the effects of the mesh resolution on the prediction accuracy of the unsteady flow field, especially we intended to capture unsteadiness in turbulent boundary layer (TBL) in the second test case with the computational mesh composed of about 30 millions hexahedral elements. The fine mesh LES successfully reproduced the transition to TBL on the suction surface of the rotor blades and gives better, when compared with the results from the coarse mesh LES, agreements with measurements in terms of Euler’s. The final case is used for providing acoustical input data of the sound source. A reasonable agreement is obtained between the predicted and measured sound pressure level evaluated at 1.5 m upstream of the blade center.

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.

A New Approach to the Experimental Study of Turbomachinery Flow Phenomena

1977 ◽  
Vol 99 (1) ◽  
pp. 97-105 ◽  
Author(s):  
J. P. Gostelow
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Centrifugal Pumps ◽  
New Approach ◽  
Static Pressure Distribution ◽  
Compressor Rotor ◽  
Flow Phenomena ◽  
On Line ◽  
Flow Compressor

Measurements of the unsteady flow field over a rotor and within its wake are needed in the development of most turbomachines. The technique advocated is that of data acquisition by on-line computer, using the periodic passing of a blade as a phase reference. The phase-lock averaging process is described as is its use in reducing the noise of raw data traces. Measurements of the unsteady flow over a cascade and of the resulting boundary layer behavior are presented. The approach was used in interpreting the unsteady flow field of an axial-flow compressor rotor and the static pressure distribution over the rotor tip. Finally the application to centrifugal pumps is discussed, enabling the designer to obtain information on the suction pressures and the extent of any separated region.

Measurement and analysis of tip clearance unsteady flow spectrum in axial-flow fan rotor

2008 ◽  
Vol 2 (4) ◽  
pp. 448-452 ◽  
Author(s):  
Bo Liu ◽  
Weimin Hou ◽  
Changyou Ma ◽  
Yangang Wang ◽  
Qiang Zhou
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Tip Clearance ◽  
Axial Flow Fan ◽  
Measurement And Analysis

scholarly journals Unsteady Flow Field Due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part II—Rotor Exit Flow Field

1997 ◽  
Vol 119 (2) ◽  
pp. 214-224 ◽  
Author(s):  
M. A. Zaccaria ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Velocity Component ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Edge Region ◽  
Trailing Edge ◽  
Rotor Wake ◽  
Cross Correlations ◽  
Far Wake

The two-dimensional steady and unsteady flow field at midspan in a turbine rotor has been investigated experimentally using an LDV with an emphasis on the interaction of the nozzle wake with the rotor flow field. The velocity measurements are decomposed into a time-averaged velocity, a periodic velocity component, and an unresolved velocity component. The results in the rotor passage were presented in Part I. The flow field downstream of the rotor is presented in this paper. The rotor wake profiles and their decay characteristics were analyzed. Correlations are presented that match the decay of the various wake properties. The rotor wake velocity defect decays rapidly in the trailing edge region, becoming less rapid in the near and far wake regions. The rotor wake semi-wake width increases rapidly in the trailing edge region and then grows more gradually in the near and far wake regions. The decay of the maximum unresolved unsteadiness and maximum unresolved velocity cross correlations is very rapid in the trailing edge region and this trend slows in the far wake region. In the trailing edge region, the maximum periodic velocity correlations are much larger than the maximum unresolved velocity correlations. But the periodic velocity correlations decay much faster than the unresolved velocity correlations. The interactions of the nozzle and rotor wakes are also studied. While the interaction of the nozzle wake with the rotor wake does not influence the decay rate of the various wake properties, it does change the magnitude of the properties. These and other results are presented in this paper.

scholarly journals Unsteady Flow Field due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part I — Rotor Passage Flow Field

1995 ◽  
Author(s):  
Michael A. Zaccaria ◽  
Budugur Lakshminarayana
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Pressure Surface ◽  
Aerodynamic Interaction ◽  
Flow Gradients ◽  
Rotor Flow

The flow field in turbine rotor passages is complex with unsteadiness caused by the aerodynamic interaction of the nozzle and rotor flow fields. The two-dimensional steady and unsteady flow field at midspan in an axial flow turbine rotor has been investigated experimentally using an LDV with emphasis on the interaction of the nozzle wake with the rotor flow field. The flow field in the rotor passage is presented in Part I, while the flow field downstream of the rotor is presented in Part II. Measurements were acquired at 37 axial locations from just upstream of the rotor to one chord downstream of the rotor. The time average flow field and the unsteadiness caused by the wake has been captured. As the nozzle wake travels through the rotor flow field, the nozzle wake becomes distorted with the region of the nozzle wake near the rotor suction surface moving faster than the region near the rotor pressure surface, resulting in a highly distorted wake. The wake is found to be spread out along the rotor pressure surface, as it convects downstream of midchord. The magnitude of the nozzle wake velocity defect grows until close to midchord, after which it decreases. High values of unresolved unsteadiness were observed at the rotor leading edge. This is due to the large flow gradients near the leading edge and the interaction of the nozzle wake with the rotor leading edge. High values of unresolved unsteadiness were also observed near the rotor pressure surface. This increase in unresolved unsteadiness is caused by the interaction of the nozzle wake with the flow near the rotor pressure surface.

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