Proof of existence of monopole‐type sound generation mechanism in a centrifugal blower

2001 ◽  
Vol 109 (5) ◽  
pp. 2306-2306
Author(s):  
Ashnapreet Nagi ◽  
Sean Wu
Keyword(s):  
Generation Mechanism ◽  
Sound Generation ◽  
Centrifugal Blower

Sound generation mechanism in low speed axial fans.

2010 ◽  
Vol 127 (3) ◽  
pp. 1837-1837 ◽  
Author(s):  
Stefano Bianchi ◽  
Alessandro Corsini ◽  
Anthony G. Sheard
Keyword(s):  
Generation Mechanism ◽  
Sound Generation ◽  
Low Speed ◽  
Axial Fans

Modeling and linear analysis of sound generation mechanism in sonic soot blowers

2019 ◽  
Vol 25 (17) ◽  
pp. 2305-2315
Author(s):  
A. Najafi ◽  
M. Asayesh ◽  
A. Siami
Keyword(s):  
Sound Wave ◽  
Parametric Study ◽  
Low Frequency ◽  
Linear Analysis ◽  
Generation Mechanism ◽  
Frequency Content ◽  
Sound Generation ◽  
Governing Equations ◽  
High Level ◽  
Frequency Sound Wave

Sonic soot blowers (SSBs) are nondestructive tools to prevent ashes and particle build-up on the surfaces of boilers or other similar instruments. For higher performance, sonic soot cleaners should generate a high level-low frequency sound wave. In this article, the sound generation mechanism in these tools has been modeled. Firstly, the governing equations of the diaphragm and the horn and coupling between them are derived. By linearization, a parametric study is performed to find the optimum design points. Based on the eigenvalue analysis, it is shown that the sound generation in sonic soot cleaners is due to instability of the interaction between the diaphragm and the horn. Moreover, it is found that the sound wave frequency is approximately equal to the lowest fundamental frequency of the horn or diaphragm. Finally, the frequency content of an SSB voice is investigated.

Investigation on Pressure Fluctuation Related to Mild Surge in Multistage Centrifugal Blower With Inlet Guide Vane

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Satoshi Joukou ◽  
Kiyohide Sakamoto ◽  
Yasushi Shinkawa ◽  
Takeshi Uchiyama
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Generation Mechanism ◽  
System Dynamic ◽  
Total System ◽  
Positive Slope ◽  
Centrifugal Blower ◽  
Operating Range ◽  
Last Stage

Centrifugal blowers are widely used for gas compression in a variety of industrial fields; however, a wider operating range is required in these machines. Investigations on the generation mechanism of unsteady flow (i.e., surge) are very important to improve the operating range. The purpose of this study is to clarify the generation mechanism of pressure fluctuations in a multistage centrifugal blower equipped with inlet guide vanes (IGVs) upstream during the first stage under the IGVs partially open condition. These pressure fluctuations occur at flowrates when the slope of the total system head curve is steeply negative. According to our previous study on the detailed unsteady pressure measurements, this pressure oscillation is supposed to be the mild surge caused by the positive slope of the head curves at the second to the last stages. The slope of the total system head curve was kept negative due to the steeply negative slope of the head curve during the first stage. Thus, the whole compression system seemed to be stable. To confirm the validity of this hypothesis, system dynamic simulations based on Greitzer's lumped-parameter model were conducted using newly measured static pressure-rise characteristic curves of each stage in a four-stage centrifugal blower. In these simulations, the pressure-rise characteristic curves of the first stage and the second to last stages were modeled as two different actuator disks, and the stabilization/destabilization effects of each stage on the system dynamic characteristics were separately taken into account under the IGVs partially open condition. The system dynamic simulation reproduced the mild surge behavior of the system under the IGVs partially open condition when the slope of the total system head curve was still kept steeply negative. The calculated amplitude and frequency of the pressure fluctuations caused by the mild surge showed satisfactory agreement with the measured ones. However, the inception flowrate of the system instability in the simulation was approximately 7% smaller than that in the measurement. From these results, we confirmed that the pressure fluctuation occurred under the IGVs partially open condition was caused by the mild surge due to the positive slope of the pressure-rise characteristic during the second to last stage. In addition, we found that this mild surge was caused by the stall of the vaned diffusers during the second to last stage.

Sound generation mechanism radiated from bubble

2016 ◽  
Vol 2016 (0) ◽  
pp. 0722
Author(s):  
Takao OKU ◽  
Hiroyuki HIRAHARA ◽  
Syoh YOSHIZAKI
Keyword(s):  
Generation Mechanism ◽  
Sound Generation

Investigation on Pressure Fluctuation Related to Mild Surge in Multi-Stage Centrifugal Blower With Inlet Guide Vane

2015 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Kiyohide Sakamoto ◽  
Yasushi Shinkawa ◽  
Satoshi Joukou ◽  
Takeshi Uchiyama
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Generation Mechanism ◽  
System Dynamic ◽  
Total System ◽  
Positive Slope ◽  
Centrifugal Blower ◽  
Operating Range ◽  
Multi Stage

Centrifugal blowers are widely used for gas compression in various industrial fields. Wider operating range is required in these machines. Investigations on the generation mechanism of unsteady flow (i.e., surge) are very important to improve the operating range of these machines. Purpose of this study is to clarify the generation mechanism of pressure fluctuations in a multi-stage centrifugal blower equipped with inlet guide vanes (IGVs) upstream of the first stage under the IGVs partially open condition. These pressure fluctuations occur at flowrates when the slope of total system head curve is steeply negative. According to our previous study on the detailed unsteady pressure measurements, this pressure oscillation is supposed to be the mild surge caused by the positive slope of the head curves at the second to the last stages. The slope of the total system head curve was kept negative due to the steeply negative slope of the head curve at the first stage. Thus, the whole compression system seemed to be stable. To confirm the validity of this hypothesis, system dynamic simulations based on Greitzer’s lumped-parameter model were conducted using newly measured static-pressure-rise characteristic curves of each stage in a four-stage centrifugal blower. In these simulations, the pressure-rise characteristic curves of the first stage and the second to last stages were modeled as two different actuator disks, and the stabilization/destabilization effects of each stage on the system dynamic characteristics were separately taken into account under the IGVs partially open condition. The system dynamic simulation reproduced the mild surge behavior of the system under the IGVs partially open condition when the slope of the total system head curve was still kept steeply negative. The calculated amplitude and frequency of the pressure fluctuations caused by the mild surge showed satisfactory agreement with the measured ones. However, the inception flowrate of the system instability in the simulation was approximately 7% smaller than that in the measurement. From these results, we confirmed that the pressure fluctuation occurred under the IGVs partially open condition was caused by the mild surge due to the positive slope of the pressure-rise characteristic at the second to the last stages. In addition, we found that this mild surge was caused by the stall of the vaned diffusers at the second to the last stage.

Sound generation mechanism of compressible vortex reconnection

2021 ◽  
Vol 933 ◽  
Author(s):  
Hamid Daryan ◽  
Fazle Hussain ◽  
Jean-Pierre Hickey
Keyword(s):  
Sound Pressure ◽  
Source Term ◽  
Near Field ◽  
Generation Mechanism ◽  
Sound Generation ◽  
Source Terms ◽  
Acoustic Source ◽  
Spatial Gradients ◽  
Delayed Onset ◽  
Vortex Reconnection

We study the sound generation mechanism of initially subsonic viscous vortex reconnection at vortex Reynolds number $Re~(\equiv \text {circulation}/\text {kinematic viscosity})=1500$ through decomposition of Lighthill's acoustic source term. The Laplacian of the kinetic energy, flexion product, enstrophy and deviation from the isentropic condition provide the dominant contributions to the acoustic source term. The overall (all time) extrema of the total source term and its dominant hydrodynamic components scale linearly with the reference Mach number $M_o$ ; the deviation from the isentropic condition shows a quadratic scaling. The significant sound arising from the flexion product occurs due to the coiling and uncoiling of the twisted vortex filaments wrapping around the bridges, when a rapid strain is induced on the filaments by the repulsion of the bridges. The spatial distributions of the various acoustic source terms reveal the importance of mutual cancellations among most of the terms; this also highlights the importance of symmetry breaking in the sound generation during reconnection. Compressibility acts to delay the start of the sequence of reconnection events, as long as shocklets, if formed, are sufficiently weak to not affect the reconnection. The delayed onset has direct ramifications for the sound generation by enhancing the velocity of the entrained jet between the vortices and increasing the spatial gradients of the acoustic source terms. Consistent with the near-field pressure, the overall maximum instantaneous sound pressure level in the far field has a quadratic dependence on $M_o$ . Thus, reconnection becomes an even more dominant sound-generating event at higher $M_o$ .

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