Tip-clearance and other three-dimensional effects in axial flow fans

1958 ◽  
Vol 9 (5-6) ◽  
pp. 357-371 ◽  
Author(s):  
Stanley P. Hutton
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Dimensional Effects

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.

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

1992 ◽  
Vol 114 (3) ◽  
pp. 675-685 ◽  
Author(s):  
A. Goto
Keyword(s):  
Velocity Fluctuation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Fields ◽  
Tip Clearance ◽  
Small Scale ◽  
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 hotwire 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 span-wise 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.

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.

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.

scholarly journals Inner Workings of Aerodynamic Sweep

1997 ◽  
Author(s):  
A. R. Wadia ◽  
P. N. Szucs ◽  
D. W. Crall
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Stall Margin ◽  
Design Speed ◽  
The Impact

The recent trend in using aerodynamic sweep to improve the performance of transonic blading has been one of the more significant technological evolutions for compression components in turbomachinery. This paper reports on the experimental and analytical assessment of the pay-off derived from both aft and forward sweep technology with respect to aerodynamic performance and stability. The single stage experimental investigation includes two aft-swept rotors with varying degree and type of aerodynamic sweep and one swept forward rotor. On a back-to-back test basis, the results are compared with an unswept rotor with excellent performance and adequate stall margin. Although designed to satisfy identical design speed requirements as the unswept rotor, the experimental results reveal significant variations in efficiency and stall margin with the swept rotors. At design speed, all the swept rotors demonstrated a peak stage efficiency level that was equal to that of the unswept rotor. However, the forward-swept rotor achieved the highest rotor-alone peak efficiency. At the same time, the forward-swept rotor demonstrated a significant improvement in stall margin relative to the already satisfactory level achieved by the unswept rotor. Increasing the level of aft sweep adversely affected the stall margin. A three-dimensional viscous flow analysis was used to assist in the interpretation of the data. The reduced shock/boundary layer interaction, resulting from reduced axial flow diffusion and less accumulation of centrifuged blade surface boundary layer at the up, was identified as the prime contributor to the enhanced performance with forward sweep. The impact of tip clearance on the performance and stability for one of the aft-swept rotors was also assessed.

Numerical Studies on Effect of Stepped Tip Clearance Height on the Performance of Single Stage Transonic Axial Flow Compressor

2013 ◽  
Author(s):  
Pritam Batabyal ◽  
Dilipkumar B. Alone ◽  
S. K. Maharana
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Flow ◽  
Single Stage ◽  
Tip Clearance ◽  
Baseline Model ◽  
Axial Flow Compressor ◽  
Design Speed ◽  
Flow Compressor

This paper presents a numerical case study of various stepped tip clearances and their effect on the performance of a single stage transonic axial flow compressor, using commercially available software ANSYS FLUENT 14.0. A steady state, implicit, three dimensional, pressure based flow solver with SST k-Ω turbulence model has been selected for the numerical study. The stepped tip clearances have been compared with the baseline model of zero tip clearance at 70% and 100 % design speed. It has been observed that the compressor peak stage efficiency and maximum stage pressure ratio decreases as the tip clearances in the rear part are increased. The stall margin also increases with increase in tip clearance compared to the baseline model. An ‘optimum’ value of stepped tip clearance has been obtained giving peak stage compressor performance. The CFD results have been validated with the earlier published experimental data on the same compressor at 70% design speed.

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.

scholarly journals Three-Dimensional Performance Prediction of Multistage Axial Flow Compressors With a Repeating Stage Model

1999 ◽  
Author(s):  
Y. G. Li ◽  
A. Tourlidakis ◽  
R. L. Elder
Keyword(s):  
Performance Prediction ◽  
Static Pressure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Correction Method ◽  
Tip Clearance ◽  
Stage Model ◽  
Inlet Velocity ◽  
Average Value ◽  
Axial Flow Compressors

In this paper, a method for the performance prediction of multistage axial flow compressors through a steady, three-dimensional, multi-block Navier-Stokes solver is presented. A repeating stage model has been developed aiming at the simplification of the required global aerodynamic boundary conditions for the simulation of the rear stages of multistage axial compressors where only mass flow rate and exit average static pressure are required. The stage inlet velocity distribution is fixed to be equal to the one calculated at the stage exit and the exit static pressure distribution is fixed to have the same shape to that at inlet but maintain its own average value. A mixing plane approach is used to exchange information between neighbouring blade rows which allows both radial and circumferential variations at both sides of the interface. A pressure correction method with the standard k–ε turbulence model is used in combination with Stone’s two step procedure for the solution of the algebraic system of the discretised equations. A global iteration is carried out in order to establish the physical consistency between the blade rows. A combination of two structured grid blocks for the rotor blade row, one for the main passage and a second for the modelling of the tip clearance, is used for a detailed representation of the leakage flows. Computational results from two methods, the first by using the repeating stage model and the second by setting stage inlet velocity profile, are presented from the analysis of the third stage of the four-stage Cranfield Low Speed Research Compressor (LSRC). Good agreements with the experimental data are obtained in terms of total pressure, static pressure and velocity distributions at the inlet, exit and interface planes proving that the repeating stage model is a very economical and accurate alternative to the very expensive complete multistage simulations.

Assessment of Three-Dimensional Inviscid Effects in Turbomachinery Using Simple Models

1976 ◽  
Vol 98 (2) ◽  
pp. 163-172 ◽  
Author(s):  
A. Tamura ◽  
B. Lakshminarayana
Keyword(s):  
Radial Direction ◽  
Three Dimensional ◽  
Axial Flow ◽  
Velocity Fields ◽  
Dimensional Effects ◽  
Vortex Lines ◽  
Source Line ◽  
Constant Strength ◽  
Stagger Angle ◽  
Modified Theory

The general objective of the investigation reported in this paper is to obtain a reliable understanding of the three-dimensional inviscid effects in axial flow turbomachinery. The calculation is based on the method of distributed singularities. The baldes are represented by a series of line vortices and line sources which have their axes along the radial direction and are arranged along the blade mean camber surface. The basic perturbed velocity fields due to radial vortex lines of constant strength and radial source lines of variable strength are computed from a modified theory based on Tyson’s and Rossow’s formulation. Examples illustrating the three-dimensional effects due to hub/tip ratio, stagger angle, and number of blades are carried out. The effects of the radial variation of the strength of the radial source line are examined. The three-dimensional effects are found to be appreciable for a low hub/tip configuration with small number of blades.

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