scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Effect of the rotor blade installation angle on the structure-borne noise generated by adjustable-blade axial-flow fans

Lihui Sun1, Chunguo An, Nini Wang, Chuntian Zhe1, Lin Wang1, Suoying He1, Ming Gao1 
01 Sep 2021-Physics of Fluids (AIP Publishing)-Vol. 33, Iss: 9, pp 095107
About: This article is published in Physics of Fluids.The article was published on 2021-09-01. It has received 4 citations till now. The article focuses on the topics: Noise & Rotor (electric).
Citations
More filters
Posted ContentDOI
24 Oct 2018
TL;DR: In this article, a low-vibrational noise optimization method for the volute casing is proposed that considers the influence of vibro-acoustic coupling, taking the panel thickness of the volutes (front panel thickness [FT], side-panel thickness [ST], and back panel thickness[BT]) as design variables, and the acoustical power of volutes surface and the total mass of volute as the optimal target function.
Abstract: Concerning fan systems with an air pipe connecting air intake and a closed outlet, aerodynamic noise cannot be directly transmitted from the fan inlet and outlet to the outside. At this moment, the volute vibrational radiation noise induced casing surface vibration is the major noise component. The main factors affecting the fan vibrational noise are analyzed through theoretical derivation, then a vibrational noise optimization control method for the volute casing is proposed that considered the influence of vibro-acoustic coupling, taking the panel thickness of the volute (front-panel thickness [FT], side-panel thickness [ST], and back-panel thickness [BT]) as design variables, and the acoustical power of the volute surface and the total mass of the volute as the optimal target function. The optimization method is mainly divided into three main parts: the first was based on the simulation of unsteady flow of the fan to obtain the vibrational noise source; the second, using the design of experimental (DOE) method and the proposed numerical simulation of fluid-structure-acoustic coupling method to obtain the designing space, then the radical-based function (RBF) method is used to construct the approximate surrogate model instead of the simulation model previously mentioned, which was used to provide the basic mathematical model for the optimization of the next part; the third part, implementing the low vibrational noise optimization for the fan volute, applied the single-target (taking volute radiated acoustical power as the target function) and the multi-target (taking the volute radiated acoustical power and volute total mass as the target function) methods. In addition, the fan aerodynamic performance, volute casing surface fluctuations, and vibration response were validated by experiments, showing good agreement. It is of utmost importance that the dynamic pressure measurements and vibrational tests on the volute casing verify the accuracy of the numerical calculation. The optimization results showed that the vibrational noise optimization method proposed in this study can effectively reduce the vibration noise of the fan, obtaining a maximum value of noise reduction of 7.3 dB. The optimization identified in this paper provides a significant reference for the design of a low-vibrational-noise volute.

19 citations

Journal ArticleDOI
01 Aug 2022-Energy
TL;DR: In this paper , a serrated Gurney flap (SGF) was proposed to reduce high-frequency noise, and the noise reduction gradually improves with decreasing serration height. But the effect of the SGF on the aerodynamic performance, sound characteristics and internal dynamics of the fan was examined, and possible mechanism for noise reduction and vortex structure were investigated.

2 citations

Journal ArticleDOI
TL;DR: In this article , a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy, and the pressure distribution and sound power level distribution characteristics of the blade surface are explored with variable blade installation angles.
Abstract: In this paper, a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy. The pressure distribution and sound power level distribution characteristics of the blade surface are explored with variable blade installation angles. Based on the Q-criterion, the study reveals the spatial distribution of the channel and trailing edge shedding and channel vortexes in the flow field. Then, the evolution laws of the fan's aerodynamic noise sound pressure level are also investigated, and its frequency domain characteristics with variable blade installation angles are obtained. The results show that when the rotor blade installation angle is -5{degree sign}, the front-guide vane matches the installation angle of the first-stage impeller. The upper limit of sound power level is the smallest with variable blade installation angles, which is 123.56 dB. Meanwhile, the number and size of vortex structures in the front-guide vane area are the smallest, and the turbulent flow in the flow field is moderate. As the moving blade installation angle is deflected from -10{degree sign} to 10{degree sign}, the total sound pressure level of aerodynamic noise at each component of the fan first decreases and then increases. The minimum value is 121.40 dB and 128.40 dB at the inlet and outlet when the blade installation angle is -5{degree sign}. In addition, the number of eddies periodically shed in the fan flow field is the least. This research can supply technical support for the noise reduction of the two-stage adjustable blade axial fan.

1 citations

Journal ArticleDOI
TL;DR: In this paper , the authors employed a numerical simulation method based on the volume of fluid model and evaporation-condensation model to investigate the noise generated by gas-liquid two-phase flow within capillary tubes in refrigeration systems.
Abstract: In order to research the noise generated by gas–liquid two-phase flow within capillary tubes in refrigeration systems, this study employs a numerical simulation method based on the volume of fluid model and evaporation-condensation model. The noise of gas–liquid two-phase flows is generated by refrigerant vaporization in capillary tubes under different inlet temperatures and diameters. The results of this study showed that two-phase flow noise in capillary tubes predominantly exists in the frequency range of 0–200 Hz, corresponding to low-frequency noise. Under different inlet temperature and diameter conditions, the total sound pressure level (TSPL) of a two-phase flow noise increased with the increase in the capillary tube diameter. Moreover, when the inlet temperature was 316.6 K, as the diameter increased from 1 to 1.9 mm, TSPL increased from 32.02 to 34.36 dB. In addition, as the inlet temperature gradually decreased, TSPL increased. Furthermore, it was found that the lower the inlet temperature, the greater the increase in TSPL. When the inlet temperatures were 316.6, 313.6, 310.6, and 307.6 K, and the diameter increased from 1 to 1.9 mm, TSPL increased by 2.34, 3.41, 4.1, and 5.38 dB, respectively, corresponding to the relative increase of 7.31%, 10.23%, 11.85%, and 15.34%. Finally, using an orthogonal analysis, a criterion relationship was obtained for predicting the TSPL of gas–liquid two-phase flow noises in capillary tubes under different conditions. This study provides guidance for noise control and structural optimization of capillary tubes considering the gas–liquid two-phase flow.
References
More filters
Journal ArticleDOI
TL;DR: In this paper, a finite-volume flow solver in an unstructured hierarchical Cartesian setup for the compressible Navier-Stokes equations is used to analyze the turbulent low Mach number flow through an axial fan at a Reynolds number of 9.36 × 105 based on the outer casing diameter.
Abstract: The turbulent low Mach number flow through an axial fan at a Reynolds number of 9.36 × 105 based on the outer casing diameter is investigated by large-eddy simulation. A finite-volume flow solver in an unstructured hierarchical Cartesian setup for the compressible Navier-Stokes equations is used. To account for sharp edges, a fully conservative cut-cell approach is applied. A newly developed rotational periodic boundary condition for Cartesian meshes is introduced such that the simulations are performed just for a 72° segment, i.e., the flow field over one out of five axial blades is resolved. The focus of this numerical analysis is on the development of the vortical flow structures in the tip-gap region. A detailed grid convergence study is performed on four computational grids with 50 × 106, 250 × 106, 1 × 109, and 1.6 × 109 cells. Results of the instantaneous and the mean fan flow field are thoroughly analyzed based on the solution with 1 × 109 cells. High levels of turbulent kinetic energy and pressure fluctuations are generated by a tip-gap vortex upstream of the blade, the separating vortices inside the tip gap, and a counter-rotating vortex on the outer casing wall. An intermittent interaction of the turbulent wake, generated by the tip-gap vortex, with the downstream blade, leads to a cyclic transition with high pressure fluctuations on the suction side of the blade and a decay of the tip-gap vortex. The disturbance of the tip-gap vortex results in an unsteady behavior of the turbulent wake causing the intermittent interaction. For this interaction and the cyclic transition, two dominant frequencies are identified which perfectly match with the characteristic frequencies in the experimental sound power level and therefore explain their physical origin.

44 citations

Journal ArticleDOI
TL;DR: In this article, the authors conducted a systematic investigation of airborne transmission in a classroom equipped with a single horizontal unit ventilator (HUV) and evaluated the performance of a low-cost box fan air cleaner for risk mitigation.
Abstract: Many indoor places, including aged classrooms and offices, prisons, homeless shelters, etc., are poorly ventilated but resource-limited to afford expensive ventilation upgrades or commercial air purification systems, raising concerns on the safety of opening activities in these places in the era of the COVID-19 pandemic. To address this challenge, using computational fluid dynamics, we conducted a systematic investigation of airborne transmission in a classroom equipped with a single horizontal unit ventilator (HUV) and evaluate the performance of a low-cost box fan air cleaner for risk mitigation. Our study shows that placing box fan air cleaners in the classroom results in a substantial reduction of airborne transmission risk across the entire space. The air cleaner can achieve optimal performance when placed near the asymptomatic patient. However, without knowing the location of the patient, the performance of the cleaner is optimal near the HUV with the air flowing downwards. In addition, we find that it is more efficient in reducing aerosol concentration and spread in the classroom by adding air cleaners in comparison with raising the flow rate of HUV alone. The number and placement of air cleaners need to be adjusted to maintain their efficacy for larger classrooms and to account for the thermal gradient associated with a human thermal plume and hot ventilation air during cold seasons. Overall, our study shows that box fan air cleaners can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces.

42 citations

Journal ArticleDOI
TL;DR: In this article, the suitability of the normalized Langevin stochastic equation with appropriate drift correction for simulation of instantaneous fluctuation velocities in inhomogeneous turbulent flows was studied.
Abstract: The suitability of the normalized Langevin stochastic equation with appropriate drift correction for simulation of instantaneous fluctuation velocities in inhomogeneous turbulent flows was studied. The Reynolds Stress Transport turbulence model of the ANSYS-Fluent code was used to evaluate the inhomogeneous turbulent flow properties in a two-dimensional duct flow. The simulation results were then used in an in-house Matlab particle tracking code and the trajectories of about 2 × 105 randomly distributed particles in the channel were evaluated by solving the particle equation of motion including the drag and Brownian forces under the one-way coupling assumption. The performance of the Continuous Random Walk (CRW) stochastic model using the conventional nonnormalized, as well as the normalized Langevin equations without and with the drift term for predicting a uniform distribution for the fluid-tracer particles in an inhomogeneous turbulent flow was examined. The accuracy of these models in predicting the deposition velocities and distribution of solid particles with diameters ranging from 10 nm to 30 μm was also carefully examined. In addition, the effects of including the finite-inertia coefficient in the drift term and using the corrected root mean square normal velocity in the near-wall region on the accuracy of the results were emphasized. By exploring the concentration profiles and deposition velocities of particles resulting from different CRW models, it was concluded that the Normalized-CRW model including the appropriate drift term leads to the most accurate results.

35 citations

Journal ArticleDOI
TL;DR: In this paper, numerical simulation has been performed to assess the effects of jet fans on the spreading of viruses inside underground car parks, and the results showed that jet fans are increasingly preferred over traditional ducted systems as a means of ventilating pollutants in large environments such as underground car park.
Abstract: Jet fans are increasingly preferred over traditional ducted systems as a means of ventilating pollutants in large environments such as underground car parks. The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)—which causes the novel coronavirus disease—through the jet fans in underground car parks has been considered a matter of key concern. A quantitative understanding of the propagation of respiratory droplets/particles/aerosols containing the virus is important. However, to date, studies have yet to demonstrate viral (e.g., SARS-CoV-2) transmission in underground car parks equipped with jet fans. In this paper, numerical simulation has been performed to assess the effects of jet fans on the spreading of viruses inside underground car parks.

34 citations

Journal ArticleDOI
TL;DR: In this article, an experimental and numerical study is conducted on a rectangular open cavity with a length to depth ratio of 2 at Mach number 1.71 by placing a subcavity at different locations.
Abstract: An experimental and numerical study is conducted on a rectangular open cavity with a length to depth ratio of 2 at Mach number 1.71 by placing a subcavity at different locations. The subcavity at the front wall has already been established as a passive control device experimentally. In addition, it has been observed that it can act as a passive resonator. However, in the current study, it is found that the location of the subcavity and its dimensions play a crucial role in determining the types of oscillations existing inside the cavity. Cavity models with a subcavity length to main cavity length of 0.2 (l/L = 0.20) were investigated by placing the subcavity at the front wall, aft wall, and simultaneously at both front and aft walls. High speed schlieren visualization revealed the presence of different shock features associated with the cavity flow field. Statistical techniques such as fast Fourier transform, spectrogram, coherence, and correlation are employed to analyze the unsteady pressure data. Numerical computations are carried out to validate the experimental results and also to explore the flow physics. The front wall subcavity acts as a passive control device with a maximum reduction of 34.1 dB in the sound pressure level for the most dominant tone, and there is also a notable reduction in the overall sound pressure level by 11.7 dB. In the case of front wall subcavity, the acoustic wave gets inclined as it interacts with the subcavity, thereby displacing the shear layer to form a dome-shaped structure. The aft wall subcavity acts as a passive resonator with distinct fluid-resonant oscillations and the respective modal frequencies differ widely from those predicted using Rossiter’s expression. The shear layer interacts with a recirculation region formed inside the subcavity at the aft wall, thereby mitigating the effect due to direct impingement of the shear layer on the aft wall. The subcavity at both walls acts as a passive suppression device with a reduction of 34.9 dB in the sound pressure level for the most dominant mode and also with a reduction of 14.5 dB in the overall sound pressure level.

33 citations