Experimental Aeroacoustic Studies on Improved Tip Configurations for Passive Control of Noise Signatures in Low-Speed Axial Fans

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Stefano Bianchi ◽  
Alessandro Corsini ◽  
Franco Rispoli ◽  
Anthony G. Sheard
Keyword(s):  
Passive Control ◽  
Flow Behavior ◽  
Near Field ◽  
Acoustic Emissions ◽  
Direct Consequence ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Noise Sources ◽  
Tip Leakage ◽  
Blade Tip

This paper presents the findings of an investigation on the use of several blade-tip configurations (modified by the addition of various end plates at the blade tip) for passive noise control in industrial fans. Utilizing an experimental technique developed to investigate noise sources along the radius of the blades, together with cross-correlation and coherence analyses of the near field and far field, the modified blade-tip configurations are shown to reduce the rotor-only aeroacoustic signature of the fan as a direct consequence of changes induced in tip-leakage flow behavior. These changes in the nature of flow mechanisms in the region of the blade tip are correlated with the spanwise noise sources, and their role in the creation of overall acoustic emissions is thus clarified. The tip-leakage flow structures are analyzed to identify their contribution to overall noise and interaction with other noise sources. Coherence spectra are also analyzed to investigate the relevance of the noise sources. The cross-correlations reveal distinctive acoustic signatures that are described in detail. The methodology has been demonstrated to be effective in identifying (i) the blade-tip configuration with the best acoustic performance, and (ii) other significant noise sources along the blade span. The modified tip configurations are shown to have a significant effect on the multiple vortex behavior of leakage flow, especially with respect to the near-wall fluid-flow paths on both blade surfaces. The reduction in fan acoustic emissions is assessed and correlated with the control of tip-leakage flows achieved by the modified blade tips.

Aerodynamic Performance of Blade Tip End-Plates Designed for Low-Noise Operation in Axial Flow Fans

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Alessandro Corsini ◽  
Franco Rispoli ◽  
A. G. Sheard
Keyword(s):  
Flow Behavior ◽  
Acoustic Emissions ◽  
Axial Flow ◽  
Low Noise ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Blade Tip ◽  
Tip Leakage Flows

This study assesses the effectiveness of modified blade-tip configurations in achieving passive noise control in industrial fans. The concepts developed here, which are based on the addition of end-plates at the fan-blade tip, are shown to have a beneficial effect on the fan aeroacoustic signature as a result of the changes they induce in tip-leakage-flow behavior. The aerodynamic merits of the proposed blade-tip concepts are investigated by experimental and computational studies in a fully ducted configuration. The flow mechanisms in the blade-tip region are correlated with the specific end-plate design features, and their role in the creation of overall acoustic emissions is clarified. The tip-leakage flows of the fans are analyzed in terms of vortex structure, chordwise leakage flow, and loading distribution. Rotor losses are also investigated. The modifications to blade-tip geometry are found to have marked effects on the multiple vortex behaviors of leakage flow as a result of changes in the near-wall fluid flow paths on both blade surfaces. The improvements in rotor efficiency are assessed and correlated with the control of tip-leakage flows produced by the modified tip end-plates.

Detection of aerodynamic noise sources in low-speed axial fans with tip end-plates

2009 ◽  
Vol 223 (6) ◽  
pp. 1379-1392 ◽  
Author(s):  
S Bianchi ◽  
A Corsini ◽  
F Rispoli ◽  
A G Sheard
Keyword(s):  
Near Field ◽  
Acoustic Emissions ◽  
Aerodynamic Noise ◽  
Correlation Technique ◽  
Tip Leakage Flow ◽  
Noise Emission ◽  
Noise Sources ◽  
Low Speed ◽  
Tip Leakage ◽  
Blade Tip

This article reports on the use of modified blade-tip configurations designed with a view to passive noise control in low-speed fans for compact cooling units. The addition of end-plates at the tip of a datum fan blade is shown to have a positive influence on the fan's rotor-only aero-acoustic signature. The aerodynamic effects of the modified blade tips are experimentally tested in a fully ducted configuration in the near field and far field using a correlation technique. The nature of the flow mechanisms in the blade-tip region are correlated with the specific end-plate design features and their role in the creation of overall acoustic emissions is clarified. The noise emitted by the fans is analysed in terms of coherent vortex structures, tip-leakage flow, and noise sources. Differences in human perception of the noise emitted to the environment are also investigated using a dot-pattern visualization. The study concludes that the modified tip configurations have a marked effect on tip-leakage vortex formation by altering the near-wall fluid paths on blade surfaces. The reduction in rotor noise emission is correlated with the control of tip-leakage flows produced by the tip end-plates.

Aerodynamic Workings of Blade Tip End-Plates Designed for Low-Noise Operation in Axial Flow Fans

2007 ◽  
Author(s):  
Alessandro Corsini ◽  
Bruno Perugini ◽  
Franco Rispoli ◽  
A. G. Sheard ◽  
Iain R. Kinghorn
Keyword(s):  
Acoustic Emissions ◽  
Axial Flow ◽  
Low Noise ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Acoustic Signature ◽  
Flow Mechanisms ◽  
Blade Tip ◽  
Rotor Losses

The use of improved blade tip geometries is addressed as an effective design concept for passive noise control in industrial fans. These concepts, based on geometrical implementations of datum blade by means of end-plates at the tip, are shown to influence effectively the fan rotor-only aero acoustic signature because of the modifications of tip leakage flow behaviour. The aerodynamic merits of the proposed blade tip concepts are investigated by experimental and computational studies in fully-ducted configuration. The nature of the flow mechanisms in the blade tip region is correlated to the specific end-plate design features, and their role in creation of overall stage acoustic emissions clarified. By means of such tools, the tip leakage flow structures of the fans are analysed in terms of vortical structure detection, chordwise leakage flow evaluation, and loading distribution. Rotor losses are also investigated within the passage and invoking classical tip loss model. It was found that the tip geometrical modification markedly affects the multiple vortex behaviour of leakage flow, by altering the near-wall fluid flow paths on both blade surfaces. The improvement of rotor efficiency curves were assessed and correlated to the control of tip leakage flows exploited by the tip end-plates.

Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

2008 ◽  
Author(s):  
Dianliang Yang ◽  
Xiaobing Yu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Relative Motion ◽  
Turbulence Models ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blade Height ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Rotation ◽  
Blade Tip

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.

Numerical Simulation of Tip Clearance Control in Axial Turbine Rotor: Part 2—Passive Control of Five Different Tip Platforms

2008 ◽  
Author(s):  
Wei Li ◽  
Wei-Yang Qiao ◽  
Kai-Fu Xu ◽  
Hua-Ling Luo
Keyword(s):  
Flow Control ◽  
Passive Control ◽  
Suction Side ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow

The tip leakage flow has significant effects on turbine in loss production, aerodynamic efficiency, etc. Then it’s important to minimize these effects for a better performance by adopting corresponding flow control. The active turbine tip clearance flow control with injection from the tip platform is given in Part-1 of this paper. This paper is Part-2 of the two-part papers focusing on the effect of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip (Partial SS Squealer), a double squealer tip (Double Side Squealer), a pressure side tip shelf with inclined squealer tip on a double squealer tip (Improved PS Squealer), a tip platform extension edge in pressure side (PS Extension) and in suction side (SS Extension) respectively. Combined with the turbine rotor and the numerical method mentioned in Part 1, the effects of passive turbine tip clearance flow controls on the tip clearance flow were sequentially simulated. The detailed tip clearance flow fields with different squealer rims were described with the streamline and the velocity vector in various planes parallel to the tip platform or normal to the tip leakage vortex core. Accordingly, the mechanisms of five passive controls were put in evidence; the effects of the passive controls on the turbine efficiency and the tip clearance flow field were highlighted. The results show that the secondary flow loss near the outer casing including the tip leakage flow and the casing boundary layer can be reduced in all the five passive control methods. Comparing the active control with the passive control, the effect brought by the active injection control on the tip leakage flow is evident. The turbine rotor efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine rotor efficiency, and it increased by 0.215%.

On the Recessed Blade Tip With and Without a Porous Material in an Axial Compressor

2014 ◽  
Author(s):  
Young-Jin Jung ◽  
Tae-Gon Kim ◽  
Minsuk Choi
Keyword(s):  
Porous Material ◽  
Axial Compressor ◽  
Internal Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Flow Solver ◽  
Stall Margin ◽  
Tip Leakage ◽  
Blade Tip ◽  
Strong Vortex

This paper addresses the effect of the recessed blade tip with and without a porous material on the performance of a transonic axial compressor. A commercial flow solver was employed to analyze the performance and the internal flow of the axial compressor with three different tip configurations: reference tip, recessed tip and recessed tip filled with a porous material. It was confirmed that the recessed blade tip is an effective method to increase the stall margin in an axial compressor. It was also found in the present study that the strong vortex formed in the recess cavity on the tip pushed the tip leakage flow backward and weakened the tip leakage flow itself, consequently increasing the stall margin without any penalty of the efficiency in comparison to the reference tip. The recessed blade tip filled with a porous material was suggested with hope to obtain the larger stall margin and the higher efficiency. However, it was found that a porous material in the recess cavity is unfavorable to the performance in both the stall margin and the efficiency. An attempt has been made to explain the effect of the recess cavity with and without a porous material on the flow in an axial compressor.

Tip Leakage Flow Reduction of a Linear Turbine Cascade Using String-Type DBD Plasma Actuators

2018 ◽  
Author(s):  
Takayuki Matsunuma ◽  
Takehiko Segawa
Keyword(s):  
Reynolds Number ◽  
Plasma Actuators ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Dbd Plasma ◽  
Tip Leakage ◽  
String Type ◽  
Displacement Thickness ◽  
Blade Tip

Tip leakage flow through the small gap between the blade tip of a turbine and the casing endwall reduces the aerodynamic performance. String-type dielectric barrier discharge (DBD) plasma actuators made of silicone printed-circuit board were used for the active control of the tip leakage flow of a linear turbine cascade. Sinusoidal voltage excitation with amplitude varying from 4 kV to 6 kV (peak-to-peak voltage: 8 kVp-p to 12 kVp-p) and fixed frequency of 10 kHz was applied to the plasma actuators. The two-dimensional velocity field in the blade passage was estimated by particle image velocimetry (PIV) under the very low Reynolds number conditions of Re = 7.1 × 103 and 1.42 × 104. The tip leakage flow was reduced by the flow control using plasma actuators. The high turbulence intensity region caused by the tip leakage flow was also reduced. For the quantitative comparisons, the displacement thickness of the absolute velocity distributions was examined. By the flow control of the plasma actuators, the displacement thickness at tip-side gradually decreased as the input voltage increased. Although three types of plasma actuators were used, with thin, thick, and flat electrodes and different ratios of discharge area, the differences in their effect were negligible. The reason for these very small differences in effect is the wide spread of the plasma discharge from the encapsulated electrode in the plasma actuator to the exposed electrode of the blade tip. At the relatively high Reynolds number condition of Re = 1.42 × 104, the effect of the plasma actuator was smaller than that at the lower Reynolds number condition of Re = 7.1 × 103.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

Comparison of Turbine Tip Leakage Flow for Flat Tip and Squealer Tip Geometries at High-Speed Conditions

2004 ◽  
Vol 128 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Nicole L. Key ◽  
Tony Arts
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Cascade Arrangement ◽  
Oil Flow ◽  
Blade Tip ◽  
Tip Velocity

The tip leakage flow characteristics for flat and squealer turbine tip geometries are studied in the von Karman Institute Isentropic Light Piston Compression Tube facility, CT-2, at different Reynolds and Mach number conditions for a fixed value of the tip gap in a nonrotating, linear cascade arrangement. To the best knowledge of the authors, these are among the very few high-speed tip flow data for the flat tip and squealer tip geometries. Oil flow visualizations and static pressure measurements on the blade tip, blade surface, and corresponding endwall provide insight to the structure of the two different tip flows. Aerodynamic losses are measured for the different tip arrangements, also. The squealer tip provides a significant decrease in velocity through the tip gap with respect to the flat tip blade. For the flat tip, an increase in Reynolds number causes an increase in tip velocity levels, but the squealer tip is relatively insensitive to changes in Reynolds number.

scholarly journals Wavelet Analysis of a Blade Tip-Leakage Flow

AIAA Journal ◽  
2018 ◽  
Vol 56 (8) ◽  
pp. 3332-3336
Author(s):  
Jérôme Boudet ◽  
Marc C. Jacob ◽  
Joëlle Caro ◽  
Emmanuel Jondeau ◽  
Bo Li
Keyword(s):  
Wavelet Analysis ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip
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