The Influence of Blade Number Ratio and Blade Row Spacing on Axial-Flow Compressor Stator Blade Dynamic Load and Stage Sound Pressure Level

1982 ◽  
Vol 104 (3) ◽  
pp. 633-641 ◽  
Author(s):  
H. E. Gallus ◽  
H. Grollius ◽  
J. Lambertz
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Dynamic Pressure ◽  
Axial Flow ◽  
Fixed Number ◽  
Pressure Level ◽  
Wake Flow ◽  
Pressure Probe ◽  
Blade Row ◽  
Stator Blade

In axial-flow turbomachines considerable dynamic blade loads and noise production occur as a result of the unsteady blade row interaction between rotor and stator blades. This paper presents results of midspan measurements of the dynamic pressure distribution on the stator blade surface (fixed number of blades) for various rotor-blade numbers and various axial clearances between rotor and stator. For this purpose, one stator blade had been provided with eleven semiconductor pressure transducers in the midspan section. Simultaneously, the sound pressure level was measured at two axial distances downstream of the stator by four condensator microphones distributed along the circumference in each of the two sections and mounted flush with the wall surface. The wake-flow distribution downstream of the rotor could be obtained by a rotating three-hole pressure probe. The results of the corresponding dynamic pressure-measurements and noise measurements are discussed and compared with results from theory.

Analysis of the Noise Level Generated by Axial Flow Fan Composed of Radial-Bladed Centrifugal Rotor

2014 ◽  
Author(s):  
S. S. Borges ◽  
R. Barbieri ◽  
P. S. B. Zdanski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Axial Flow ◽  
Acoustic Resonance ◽  
Pressure Level ◽  
Resonance Mode ◽  
Numerical Techniques ◽  
Cooling Systems ◽  
Centrifugal Fans ◽  
Motor Cooling

The objective of this work is to present, by means of experimental, analytical and numerical techniques that sound pressure level generated by radial-bladed centrifugal fans of electric motor cooling systems may be expressed by a logarithmical ratio of the peripheral velocity of rotor, volumetric flow and efficiency of the fan. The proposed methodology proved to be efficient and simple in the prediction of generated noise by radial-bladed centrifugal fans of TEFC motors with accuracy of ± 3 dB. In addition, the acoustic resonance mode of the fan cavity were determined by means of numerical simulations, which its results were validated through experiments using waterfall spectrum.

Noise Reduction Analysis of Electronic Device Cooling Fan With Duct and Its Application Under Variable Working Conditions

2021 ◽  
Author(s):  
Zonghan Sun ◽  
Jie Tian ◽  
Grzegorz Liśkiewicz ◽  
Zhaohui Du ◽  
Hua Ouyang
Keyword(s):  
Noise Reduction ◽  
Working Conditions ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Reduction Method ◽  
Axial Flow ◽  
Pressure Level ◽  
Inlet Flow ◽  
Cooling Fan ◽  
Inlet Duct

Abstract A noise reduction method for axial flow fans using a short inlet duct is proposed. The pattern of noise reduction imposed by the short inlet duct on the axial flow cooling fan under variable working conditions was experimentally and numerically examined. A 2-cm inlet duct was found to reduce tonal noise. As the tip Mach number of the fan increased from 0.049 to 0.156, the reduction in the total average sound pressure level at 1 m from the fan increased from 0.8 dB(A) to 4.3 dB(A), and further achieved 4.8 dB(A) when a 1-cm inlet duct was used. The steady computational fluid dynamics (CFD) showed that the inlet duct has little effect on the aerodynamic performance of the fan. The results of the full passage unsteady calculation at the maximum flow rate showed that the duct has a significant influence on the suction vortexes caused by the inlet flow non-uniformity. The suction vortexes move upstream to weaken the interaction with the rotor blades, which significantly reduces the pulsating pressure on the blades. The sound pressure level (SPL) at the blade passing frequency (BPF) contributed by the thrust force was calculated to reduce by 36 dB at a 135° observer angle, reflecting the rectification effect of the duct on the non-uniform inlet flow and the improvement in characteristics of the noise source. The proper orthogonal decomposition (POD) of the static pressure field on the blades verified that the main spatial mode is more uniformly distributed due to the duct, and energy owing to the rotor-inlet interaction decreases. A speed regulation strategy for the cooling fan with short inlet duct is proposed, which provides guidance for the application of this noise reduction method.

Experimental and Numerical Investigation of Blades Effect on Aerodynamic Performance of Small Axial Flow Fan

2011 ◽  
Author(s):  
Li Zhang ◽  
Yingzi Jin ◽  
Yi Zhao ◽  
Pin Liu
Keyword(s):  
Flow Field ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Blade Number ◽  
Small Axial Flow Fan ◽  
Fan Blade

To explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, the steady flow field and the unsteady flow field of fan models with 6 different blade numbers (such as 5, 7, 9, 11, 13, 15) are numerically calculated. Then the internal flow distribution, static characteristic and aerodynamic noise are analyzed among six different fan models. The analysis results show: (1)Total pressure and efficiency generally maintain the trend of first increasing and then decreasing with increasing blade numbers, and it is the maximum when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With increasing blade numbers, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is first decreasing and then increasing before decreasing again at 1 meter away from the central axis of the impeller along the outlet. When fan blade number is 11, overall sound pressure level of the aerodynamic noise is the greatest. Furthermore, the aerodynamic performance tests of fan models with 6 different blade numbers are carried out, the results of between the tests and the numerical calculations are roughly consistent. The research results will provide the proof of the parameter optimization and the structure design for high performance and low noise small axial fans.

Effect of Blade Numbers on Aerodynamic Performance and Noise of Small Axial Flow Fan

2011 ◽  
Vol 199-200 ◽  
pp. 796-800
Author(s):  
Li Zhang ◽  
Ying Zi Jin
Keyword(s):  
Flow Field ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Blade Number ◽  
Small Axial Flow Fan ◽  
Fan Blade

To more fully explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, some solutions are adopted to obtain the parameters’ distribution of the flow field.Firstly, the standard k-ε turbulence model is used to calculate the steady flow field of six different fan blades(such as 5,7,9,11,13,15) , and the SIMPLE algorithm is applied to couple vecolity and pressure. Secondly, the large eddy simulation in conjunction with the FH-W noise model are used to compute the unsteady flow field and noise. Finally, the experimental results verify that the calculation methods of steady flow field and unsteady flow field are correct. The conclusions show: (1)Total pressure and efficiency generally maintain the trend of firstly increasing and then decreasing with increasing the blade numbers, and it is the greatest when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With the increasing blades, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is firstly decreasing and then increasing before decreasing again 1 meter away from the central axis of the impeller along the outlet. When fan blade number is 11, overall sound pressure level of the aerodynamic noise is the greatest.

scholarly journals Effect of Airfoil Concavity on Wind Turbine Blade Performances

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Jianlong Ma ◽  
Yafan Duan ◽  
Ming Zhao ◽  
Wenchun Lv ◽  
Jianwen Wang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Aerodynamic Performance ◽  
Pressure Level ◽  
Wind Turbine Blade ◽  
Wake Flow ◽  
Suction Surface ◽  
Horizontal Axis Wind Turbine

Although the optimization of wind turbine blade aerodynamic performance has achieved fruitful results, whether airfoil concavity, an important method for preventing flow separation, is also feasible for improving the aerodynamic performance has not been confirmed scientifically. Thus, we selected the blade of a small horizontal-axis wind turbine as a research model and proposed an optimization method based on airfoil concavity near the trailing edge of the blade suction surface. The experimental results showed that airfoil concavity improved blade aerodynamic performance by 3–15%. Subsequently, its effects on the sound pressure level within the wake flow field were investigated using an acoustic array, and the results suggested that the sound pressure level was reduced by 9.6–15.8%. Lastly, a modal test of the rotor blade was conducted. Although the natural frequencies of the 1st and 2nd order vibrations had hardly changed, their vibrational stiffness were increased by 7 and 4.9%, respectively, which indicated that airfoil concavity significantly improved structural robustness.

The Effect of Interaction Between Wakes From Blade Rows in an Axial Flow Compressor on the Noise Generated by Blade Interaction

1972 ◽  
Vol 94 (4) ◽  
pp. 241-248 ◽  
Author(s):  
G. J. Walker ◽  
A. R. Oliver
Keyword(s):  
Sound Pressure Level ◽  
Rotor Blade ◽  
Sound Pressure ◽  
Axial Flow ◽  
Pressure Level ◽  
Rotor Blades ◽  
Hot Wire ◽  
Velocity Defect ◽  
Axial Flow Compressor ◽  
Flow Compressor

The effect of interaction between the wakes from one row of blades and the boundary layers and wakes of the next row of blades downstream has been measured in an axial flow compressor by hot wire signals displayed on a CRO screen synchronized with the rotor. It is shown that the two sets of wakes can be made to mutually cancel the greater part of the velocity defect in each at certain points. Proper choice of axial and circumferential position of alternate rows of stationary blades so that the downstream row is in the middle of the wake street from the upstream row allows the velocity defect normally in the rotor wakes to be thus cancelled at the position of the stator and considerably reduces the noise produced at the rotor blade passing frequency by the rotor wakes on the stator. The effect of stator wakes on rotor blades downstream of the first can be similarly reduced by lining up blades in successive rotor rows. The deductions are confirmed by measurements of sound pressure level.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

2020 ◽  
Vol 63 (4) ◽  
pp. 931-947
Author(s):  
Teresa L. D. Hardy ◽  
Carol A. Boliek ◽  
Daniel Aalto ◽  
Justin Lewicke ◽  
Kristopher Wells ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Vocal Tract ◽  
Presentation Mode ◽  
Pressure Level ◽  
Presentation Modes ◽  
Audiovisual Stimuli ◽  
Vocal Tract Resonance ◽  
Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

Case study: Theoretical calculation model and variable condition analysis research on the water-splashing noise for natural draft wet cooling towers

2020 ◽  
Vol 68 (2) ◽  
pp. 137-145
Author(s):  
Yang Zhouo ◽  
Ming Gao ◽  
Suoying He ◽  
Yuetao Shi ◽  
Fengzhong Sun
Keyword(s):  
Theoretical Model ◽  
Sound Pressure Level ◽  
Water Droplet ◽  
Water Distribution ◽  
Sound Pressure ◽  
Cooling Tower ◽  
Distribution Patterns ◽  
Calculation Model ◽  
Pressure Level ◽  
Cooling Towers

Based on the basic theory of water droplets impact noise, the generation mechanism and calculation model of the water-splashing noise for natural draft wet cooling towers were established in this study, and then by means of the custom software, the water-splashing noise was studied under different water droplet diameters and water-spraying densities as well as partition water distribution patterns conditions. Comparedwith the water-splashing noise of the field test, the average difference of the theoretical and the measured value is 0.82 dB, which validates the accuracy of the established theoretical model. The results based on theoretical model showed that, when the water droplet diameters are smaller in cooling tower, the attenuation of total sound pressure level of the water-splashing noise is greater. From 0 m to 8 m away from the cooling tower, the sound pressure level of the watersplashing noise of 3 mm and 6 mm water droplets decreases by 8.20 dB and 4.36 dB, respectively. Additionally, when the water-spraying density becomes twice of the designed value, the sound pressure level of water-splashing noise all increases by 3.01 dB for the cooling towers of 300 MW, 600 MW and 1000 MW units. Finally, under the partition water distribution patterns, the change of the sound pressure level is small. For the R s/2 and Rs/3 partition radius (Rs is the radius of water-spraying area), when the water-spraying density ratio between the outer and inner zone increases from 1 to 3, the sound pressure level of water-splashing noise increases by 0.7 dB and 0.3 dB, respectively.

Sign in / Sign up

Export Citation Format

Share Document