Combined Aerodynamic and Phased Array Microphone Studies on Basic Models of Low-Speed Axial Fan Blade Sections

2018 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Reynolds Number ◽  
Phased Array ◽  
High Efficiency ◽  
Low Reynolds Number ◽  
Low Noise ◽  
Axial Fan ◽  
Noise Sources ◽  
Low Speed ◽  
Axial Fans ◽  
Low Reynolds

The paper presents comparative aerodynamic and aeroacoustic studies on basic models of blade sections of low-speed, low-Reynolds-number axial fans. The wind tunnel experiments incorporated representative cambered plate and airfoil blade profiles. The aerodynamic measurements revealed that, for low Reynolds numbers, cambered plate blade sections may perform aerodynamically better than airfoil sections. A phased array microphone system, combined with a dipole beamforming and spatial filtering technique, offered a potential for localizing the noise sources in both streamwise and transversal direction. The acoustic studies focused on the profile vortex shedding noise. The results were qualitatively evaluated and compared with the semi-empirical noise prediction model developed by Brooks, Pope, and Marcolini. The measurements are considered as preparation of a dataset contributing to the background for designing high-efficiency, low-noise axial fans operating at low Reynolds number.

Active control of high-speed and high-Reynolds-number jets using plasma actuators

2007 ◽  
Vol 578 ◽  
pp. 305-330 ◽  
Author(s):  
M. SAMIMY ◽  
J.-H. KIM ◽  
J. KASTNER ◽  
I. ADAMOVICH ◽  
Y. UTKIN
Keyword(s):  
Reynolds Number ◽  
Nozzle Exit ◽  
High Speed ◽  
Low Reynolds Number ◽  
Plasma Actuators ◽  
Mixing Enhancement ◽  
Azimuthal Mode ◽  
Potential Core ◽  
Low Speed ◽  
Low Reynolds

Localized arc filament plasma actuators are used to control an axisymmetric Mach 1.3 ideally expanded jet of 2.54 cm exit diameter and a Reynolds number based on the nozzle exit diameter of about 1.1×106. Measurements of growth and decay of perturbations seeded in the flow by the actuators, laser-based planar flow visualizations, and particle imaging velocimetry measurements are used to evaluate the effects of control. Eight actuators distributed azimuthally inside the nozzle, approximately 1 mm upstream of the nozzle exit, are used to force various azimuthal modes over a large frequency range (StDF of 0.13 to 1.3). The jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of the development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.33 (f = 5 kHz), in good agreement with the results in the literature for low-speed and low-Reynolds-number jets. The jet (with a thin boundary layer, D/θ ∼ 250) also responded to forcing with various azimuthal modes (m = 0 to 3 and m = ±1, ±2, ±4), again in agreement with instability analysis and experimental results in the literature for low-speed and low-Reynolds-number jets. Forcing the jet with the azimuthal mode m = ±1 at the jet preferred-mode frequency provided the maximum mixing enhancement, with a significant reduction in the jet potential core length and a significant increase in the jet centreline velocity decay rate beyond the end of the potential core.

Aerodynamic Characteristics and Noise Analysis of a Low-Speed Axial Fan

2018 ◽  
Author(s):  
Bo Luo ◽  
Wuli Chu ◽  
Wei Dong ◽  
Xiangyi Chen
Keyword(s):  
Noise Analysis ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Low Noise ◽  
Axial Fan ◽  
Tonal Noise ◽  
Low Speed ◽  
Optimum Choice ◽  
Aerodynamic Performances ◽  
Axial Fans

Axial fans are widely used in modern industry and new regulations and stringent environmental concerns are prompting manufacturer to design efficient low-noise axial fans. This paper is focused on improving the aerodynamic performances and reducing the tonal noise at BPF and its harmonics by the optimum choice of lean-swept blade and the stacking line for the low-speed axial fan. The aerodynamic characteristics of the axial fan with a shroud are explored by CFD with ANASYS CFX. A hybrid method, SST turbulence model for flow and FW-H equation for acoustics, is chosen to predict the radiated noise. The accuracy and reliability of predicted aerodynamic and aeroacoustics results are verified by comparing both computation and experimental data. A number of modified blades with different leaned angle, swept angle and the stacking lines are modeled and analyzed, and the investigation into the optimum choice of lean-swept blade and the stacking line is conducted according to aerodynamic performances and tonal noise. Q-criterion which can visualize the major flow disturbances is applied for the purpose of identification of acoustic sources. The turbulent flow structures on the leading edge, tip and suction side of the blade are main noise sources. An optimal modification is determined through the analysis of the aerodynamic performances and noise, which is to achieve the desired performances by blade sweep and lean and adjusting the stacking line. The results show that aerodynamic and acoustic performances of the optimized fan are better than that of the original fan and the improvement is more obvious to change the stacking line with centre of gravity compare to blade sweep and lean for the low-speed axial fan.

Low Reynolds Number Response of High Efficiency, Intermediate Pressure Compressor Profiles

2017 ◽  
Author(s):  
Benigno J. Lázaro ◽  
Ezequiel González ◽  
David Cadrecha ◽  
Antonio Antoranz ◽  
Jorge Parra
Keyword(s):  
Reynolds Number ◽  
Scaling Laws ◽  
High Efficiency ◽  
Low Reynolds Number ◽  
Design Flow ◽  
Intermediate Pressure ◽  
Flow Evolution ◽  
Low Reynolds ◽  
Profile Loss ◽  
Pressure Compressor

Current trends on intermediate pressure, axial compressors designs for aeroengine applications demand to extend their operation envelope into low Reynolds number regimes, of the order of 105 based on the real chord and inlet velocity (Re). In this range, a very limited open experimental database on profile performance can be found. Furthermore, in order to propose high efficiency designs for this regime, it is critical to determine and to understand the profile behaviour with respect to different operating parameters. In this work, a detailed experimental study of a proposed high efficiency, intermediate pressure compressor aerofoil has been carried out, both for design and off-design flow incidences, in the range 1.5 · 105 < Re < 3.5 · 105,. The experimental facility is a low-speed linear cascade where different boundary suction strategies have been implemented to optimize the flow periodicity and to minimize pressure gradient perturbations induced by end-wall secondary flow development, in an effort to ensure high quality, 2D passage flow evolution both at design and significant off-design incidences. High resolution total pressure loss and LDV traverses performed at different streamwise locations have been carried out to describe the flow evolution. The characterizations performed at close to nominal incidence give a profile loss dependence on the Reynolds number that exhibits two clearly differentiated ranges, with the lower one exhibiting a higher profile loss dependence on the Reynolds number. At large off-design incidences, the profile loss coefficient practically becomes independent of the Reynolds number, rapidly increasing as the incidence is increased. In both cases physical arguments and scaling laws based on the experimental evidence are proposed to explain the profile behavior. RANS and URANS based CDF simulations have been also conducted, showing their ability and limitations to capture the experimentally observed aerofoil behavior.

Experimental Investigation of the Effect of Reynolds Number on the Efficiency of Single-Stage Axial Fans

2018 ◽  
Author(s):  
Massimo Masi ◽  
Stefano Castegnaro ◽  
Andrea Lazzaretto
Keyword(s):  
Reynolds Number ◽  
Axial Flow ◽  
Operating Conditions ◽  
Single Stage ◽  
Axial Fan ◽  
Low Speed ◽  
Surface Finishes ◽  
Axial Fans ◽  
The Many ◽  
Testing Standards

Uncertainties surrounding the influence of Reynolds number on the performance of air handling turbomachines are as old as the study of turbomachinery fluid dynamics. In particular, all low-speed turbomachines and most axial-flow fans feature Reynolds numbers that are often lower than the critical value, above which the literature states a limited dependency of blades cascade aerodynamics on Reynolds number. Testing standards already account for this well-known issue, which arises mainly in the case of geometrically similar fans of different size and/or operating conditions. On the other hand, one of the main practical issues in the design of low-speed machines is the disagreement among the most authoritative sources on the value of the critical Reynolds number for axial fans. The many definitions of Reynolds number, which are suited to either fan design purposes or fan performance assessment, introduce additional problems, as the corresponding values may differ by orders of magnitude depending on the chosen definition. A less debated issue deals with the effect of Reynolds number on global performance and efficiency parameters for different axial-flow fan configurations. This paper reports pressure and efficiency data measured at several rotational speeds of four axial fans that feature different configurations, hub-to-tip ratios, sizes and surface finishes. In particular, the tests consider two 315mm and one 630mm tube-axial fans, and one 800mm vane-axial fan with preswirler blading. Data on two vane-axial fans with straightener, and one preswirler-rotor-stator stage, available in the literature, widen the discussion on the Reynolds number effect on the entire category of single-stage axial fans.

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds
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