Journal of the Korean Society for Precision Engineering

Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery: Jihun Song, Chang Ho Son, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2025;42(9):763-770.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.088

Abstract
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Centrifugal compressor is a device that converts kinetic energy to increase the air pressure. It rotates at a high speed of up to 200,000 RPM and directly affects aerodynamic noise. Various studies have already been conducted, but the direct calculation method of acoustics based on the unsteady solution is inefficient because it requires a lot of resources and time. Therefore, flow characteristics and numerical comparison according to various aerodynamic factors predicted as a cause of noise generation were analyzed in this study based on the steady solution. High-frequency noise was calculated locally near the asymmetric flow properties. Vortex and turbulent kinetic energy were generated at similar locations. Among static components, a large-sized vortex of 3.48×10⁷ s^-1 was distributed at the location where the rotational flow around the compressor wheel combined with the inlet suction flow. In addition, a locally high vortex of 8.16×10⁵ s^-1 was distributed around the balancing cutting configurations that cause asymmetric flow characteristics. Analysis of these factors and causes that directly affect noise can be efficiently improved in the pre-design stage. Therefore, the efficient design methodology for centrifugal compressors that considers both performance and noise is expected based on the results of this study.

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An Aeroacoustics Study on AAM Blade in Duct with Different Strut Shapes: Sang Hyun Kim, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(9):751-758.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.060

Abstract
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Lately, due to the concentration of population in metropolitan areas, traffic congestion in the hub city has occurred, and future mobility AAM development is undergoing active progress to solve this situation. Accordingly, reducing noise pollution, which is pointed out as one of the problems of AAM, is an essential technical issue for urban operation. In this study, a duct, which is a representative aerodynamic noise reduction method, was used, and numerical analysis was performed using ANSYS FLUENT, a CFD software, according to the shape of struts in the duct. The FW-H of the transient-state LES model was used, and the steady-state analysis value was used as the initial value to save analysis time. Case 1 without strut, Case 2 with strut of an airfoil section, and Case 3 with strut of a rectangle section were designed and compared at a rotational speed of 6,000 RPM. Compared to Case 1, Case 2 and Case 3 showed improved thrust by about 7% and 2%, respectively. Compared to Case 2, Case 3 showed reduced OASPL from a minimum of 0.0793 dB to a maximum of 1.0072 dB. It was found that shapes of strut in the duct significantly affect thrust and aerodynamic noise.

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A Study on Aerodynamic Noise Reduction Depending on UAM Main Propeller Lay-out: Chang Ho Son, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(9):741-750.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.059

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Recently, as UAM has been in the spotlight worldwide, the issue of aerodynamic noise generated from propellers has emerged. Therefore, changes in thrust and aerodynamic noise were compared while changing the propeller lay-out distance. The designed propeller model was analyzed using ANSYS Fluent, a CFD software. Based on steady-state analysis, transient analysis was performed, and SPL was calculated using the FW-H noise model. Based on the standard propeller lay-out distance of 0.1 R (0.12 mm), 5 cases from 0.2 R to 0.6 R were compared with the reference model at equal intervals of 0.1 R. The thrust increased by up to 3.5% as the propeller distance increased. In most listeners positioned to measure SPL, noise was reduced by 0.07-0.7% in the improved model compared to the reference model due to reduction in local vorticity. However, because pressure fluctuation due to the increase in thrust and high SPL in the low-frequency region were measured, noise increased by 0.6% to 3.5% in some listeners. Increasing the propeller distance enhances thrust performance, but inevitably increases noise due to pressure fluctuations and SPL in the low-frequency region. Therefore, strict analysis of noise prediction according to a specific frequency and various design shapes are needed.

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A Study on Aerodynamic and Acoustic Characteristics of Blades by Biomimetic Design for UAM: Chang Ho Son, Sang Hyun Kim, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(7):571-580.
Published online July 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.018

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Urban air mobility (UAM) is rapidly growing as a new means of transportation. As a result, noise pollution is emerging as a new technical challenge. Therefore, the sawtooth-shaped biomimetic designs were incorporated on the trailing edge of the blade to reduce flow-induced noise. The biomimetic virtual design was analyzed using the CFD software, ANSYS FLUENT V20.2. Based on the steady-state RANS flow solution, the acoustic power was calculated using the broadband noise source model to evaluate acoustic radiation. Four different cases with cutting lengths of 3.1 mm, 3.7 mm, 4.3 mm, and 4.9 mm of blades were compared with the base model at the rotational blade speed of 6,000 RPM. The maximum acoustic power level of the biomimetic blades ranged from 37.24 dB to 39.88 dB, resulting in a 10% reduction compared to the original blade (42.02 dB). The novel design affected the blade area, which inevitably reduced the slight thrust performance. However, the thrust was reduced to approximately less than 5% compared with the base blade in case 1. The biomimetic blade reduced the thrust due to its aerodynamic characteristics. However, the design of a blade with an appropriate cutting length has a greater effect in reducing noise rather than thrust.

Citations

Citations to this article as recorded by

Propeller Modification with Groove Structure on Thrust Performance
Duygu Özyurt, Hürrem Akbıyık
Celal Bayar Üniversitesi Fen Bilimleri Dergisi.2025; 21(1): 27. CrossRef