scholarly journals Effects of Operating Conditions on the Flow in the Moving Blade Passage of a Single Stage Axial-Flow Fan

1997 ◽  
Vol 3 (4) ◽  
pp. 269-276 ◽  
Author(s):  
Tsutomu Adachi ◽  
Yutaka Yamashita ◽  
Kennichiro Yasuhara ◽  
Tatsuo Kawai
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Hot Wire ◽  
Axial Flow Fan ◽  
Blade Passage ◽  
Operational Conditions ◽  
Flow Phenomena ◽  
Steady Velocity

Three dimensional steady and unsteady velocity distributions in the axial flow fan were measured using a hot wire probe for various operational conditions, various rotational speeds and various measuring positions. For measuring the velocity distributions in the blade passage, a specially designed and manufactured hot wire traversing apparatus was used. Steady velocity distributions, turning angles, effects of incident to the cascade, flow leakage through the tip clearance and effects of the flow separation show the flow phenomena through the blade passages. Unsteady velocity distributions show time dependent procedures of the wake flowing through the moving blade passage. Considering these results of measurements, the effects of the upstream stationary blade and the effects of Reynolds number on the flow were considered.

Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

1993 ◽  
Vol 115 (1) ◽  
pp. 128-136 ◽  
Author(s):  
J. Zeschky ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Hot Wire ◽  
Turbine Stage ◽  
Static Pressure Distribution ◽  
Inlet Conditions ◽  
Experimental Values ◽  
Rotor Flow

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data include the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The paper presents the formation of the tip clearance vortex and the passage vortices, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

Physics of Tip Clearance Flow in Turbomachinery (Keynote Paper)

2002 ◽  
Author(s):  
Masahiro Inoue ◽  
Masato Furukawa
Keyword(s):  
Flow Field ◽  
Physical Interpretation ◽  
Vortex Core ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

In a recent advanced aerodynamic design of turbomachinery, the physical interpretation of three-dimensional flow field obtained by a numerical simulation is important for iterative modifications of the blade or impeller geometry. This paper describes an approach to the physical interpretation of the tip clearance flow in turbomachinery. First, typical flow phenomena of the tip clearance flow are outlined for axial and radial compressors, pumps and turbines to help comprehensive understanding of the tip clearance flow. Then, a vortex-core identification method which enables to extract the vortical structure from the complicated flow field is introduced, since elucidation of the vortical structure is essential to the physical interpretation of the tip clearance flow. By use of the vortex-core identification, some interesting phenomena of the tip clearance flows are interpreted, especially focussing on axial flow compressors.

A Numerical Study on the Structure of Tip Clearance Flow in a Highly Forward-Swept Axial-Flow Fan

2002 ◽  
Author(s):  
Gong Hee Lee ◽  
Je Hyun Baek
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Streamwise Velocity ◽  
Tip Clearance ◽  
Wake Flow ◽  
Axial Flow Fan ◽  
Step Method ◽  
Fractional Step Method ◽  
Tip Clearance Flow

A three-dimensional Navier-Stokes analysis was performed to investigate the tip clearance flows in a highly forward-swept axial flow fan operating at design condition. The numerical solution was based on a fractional step method, and two-layer k-ε model was used to obtain the eddy viscosity. The tip leakage vortex decayed very quickly inside the blade passage and, thus, no distinct leakage vortex appeared behind trailing edge. The main reason was the severe decrease of the streamwise velocity of the vortex. Also the interaction of the vortex with the casing boundary layer and the through-flow were other possibilities of the fast decay of the vortex. Comparison between the numerical results and LDV measurements data indicated that the complex viscous flow patterns inside the tip region as well as the wake flow could be properly predicted, but more refinement in numerical aspects are needed.

Unsteady Flow Analysis of the Stator-Rotor Interaction in an Axial Flow Fan

2003 ◽  
Author(s):  
J. Ferna´ndez Oro ◽  
K. Argu¨elles Di´az ◽  
C. Santolaria Morros ◽  
R. Ballesteros Tajadura
Keyword(s):  
Unsteady Flow ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Axial Flow ◽  
3D Models ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Axial Flow Fan ◽  
Rotating Blade ◽  
Flow Phenomena

In the usual operation of turbomachinery, some unsteady flow phenomena appear due to the non uniformity of the flow inside the rotor, when observed in the fixed reference frame. These phenomena are often related to the unsteady character of the pressure and velocity fields, which produce oscillating forces on the blades, superimposed to the steady force. These oscillating forces are the main mechanism of noise generation, which appear even at a constant rotational speed and at flow rates where the performance curves are stable. In axial turbomachines, the interaction is due to relative motion between the static and rotating blade rows. Considering the case of a fixed blade row (stator) placed upstream of the rotor, the non uniform flow leaving those blades (usually referred as IGV blades) is observed as an unsteady flow by the rotor blades. The effect of this interaction is the generation of unsteady forces on the rotor blades, which generate vibrations (risk of fatigue failure) and noise, and non-uniformity and unsteadiness of the pressure field, that propagates as an acoustic wave. The first part of this work is a brief description of a URANS numerical modeling of the unsteady flow characteristics of a one-stage subsonic axial flow fan with a reaction degree greater than 1. The focus is placed on the statorrotor interaction performance. Both 2D and 3D models of the fan, with 13 IGV’s and 9 rotor blades, were developed and an unsteady simulation was achieved to carry out the main characteristics of the flow inside the turbomachine. Once the actuating forces are determined, the influence of the radial position, the operating conditions and the distance of the fixed and the rotating blade rows is also analyzed. The final part of the paper is focused over the identification, through the definition of deterministic stresses — related to the characteristic blade-passage frequency of every row — that provoke the interaction between fixed and rotating blade rows and its evolution through time. The object is to obtain, in a stress tensor form, the contribution of the velocity field, that is changing because of the sucessive relative positions between blade rows, to the pressure distribution over the blade surfaces in the interior of the stage. Finally, a map of deterministic stresses and even, deterministic kinetic energy, can be obtained to show the influence of the blade rows in the interaction, unsteady phenomena.

The Measurement of Three-Dimensional Flow Field in an Axial Flow Fan Using PDA

2002 ◽  
Author(s):  
Zhaohui Du ◽  
Wanlai Lin ◽  
Xiaocheng Zhu ◽  
Yan Zhao
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Fields ◽  
Tip Clearance ◽  
Measurement Technology ◽  
Particle Dynamic ◽  
Axial Flow Fan ◽  
Three Dimensional Flow ◽  
Dimensional Flow

In this paper, a three-color dual-beam PDA (Particle Dynamic Analyzer) system (made by DANTEC Measurement Technology) is used to measure the three-dimensional velocity of an axial flow fan. Due to the geometrical limit of fan rotor, non-orthogonal velocity components are measured first, from which the orthogonal three-dimensional components of the velocity field are computed through transformation equations. The detailed flow fields at 15 axial locations upstream, inside and at the exit of the rotor are measured, respectively. On each cross section perpendicular to the rotating axis, the flow field measurement at 15 different radial locations from 50% of the blade span to the region inside the tip clearance (between the tip blade and the casing wall) are taken. The experimental technique is described, and the three dimensional flow fields (including the tip clearance flow) are presented and analyzed.

Three-Dimensional Flow and Mixing in an Axial Flow Compressor With Different Rotor Tip Clearances

1991 ◽  
Author(s):  
Akira Goto
Keyword(s):  
Velocity Fluctuation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Small Scale ◽  
Hot Wire ◽  
Three Dimensional Flow ◽  
Axial Flow Compressor ◽  
Dimensional Flow ◽  
Flow Compressor

The effect of difference in rotor tip clearance on the mean flow fields and unsteadiness and mixing across a stator blade row were investigated using hot-wire anemometry, pressure probes, flow visualization and the ethylene tracer-gas technique on a single stage axial flow compressor. The structure of the three-dimensional flow fields was discussed based on results of experiments using the 12-orientation single slanted hot-wire technique and spectrum analysis of velocity fluctuation. High-pass filtered measurements of turbulence were also carried out in order to confirm small-scale velocity fluctuation which is more realistically referred to as turbulence. The spanwise distribution of ethylene gas spreading, estimated by the measured small-scale velocity fluctuation at the rotor exit, agreed quite well with that which was experimentally measured. This fact suggests the significant role of turbulence, generated within the rotor, in the mixing process across the downstream stator. The value of the maximum mixing coefficient in the tip region was found to increase linearly as the tip clearance became enlarged, starting from the value at midspan.

Axial-Slot Casing Treatments Improve the Efficiency of Axial Flow Compressors: Aerodynamic Effects of a Rotor Redesign

2013 ◽  
Author(s):  
J. Anton Streit ◽  
Frank Heinichen ◽  
Hans-Peter Kau
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Negative Effects ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Flow Phenomena ◽  
Casing Treatments

A state-of-the-art transonic compressor rotor has a distinct potential for increased efficiency if modified for improved interaction with an axial-slot type casing treatment. Reducing the number of blades and thus the surface lowers friction losses but increases tip clearance effects and deteriorates the stall margin due to the higher aerodynamic blade loading. The latter two negative effects can be compensated for by the casing treatment, thus restoring the required stall margin and gaining an overall reduction of losses. For the specific compressor rotor under investigation, the potential in polytropic efficiency is as high as 0.7%. The present study was performed using time-accurate CFD (URANS) simulations. Both the reference rotor as well as the modified design are analyzed regarding their interaction with the casing treatment. The traceability of the conclusions is assured by interpreting the detailed flow phenomena. The newly designed rotor is found to be favorably influenced by the casing treatment at design operating conditions whilst the reference only benefits at throttled operating points. Casing treatments are commonly used to broaden the operating range of existing compressors without changing the design of the compressor rotor itself. This study aims to show the possible transformation of this potential in the stall margin into efficiency at design operating conditions by implementing an appropriate rotor design.

Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

1991 ◽  
Author(s):  
J. Zeschky ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Hot Wire ◽  
Turbine Stage ◽  
Static Pressure Distribution ◽  
Inlet Conditions ◽  
Experimental Values ◽  
Rotor Flow

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data includes the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The formation of the tip clearance vortex and the passage vortices is presented, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

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