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진동 신호를 이용한 블로워 모터 틱/클릭과 톤 소음의 진단 지수 개발
이송준,정철웅,이인혁,Lee, Songjune,Cheong, Cheolung,Lee, In-Hyuk 한국음향학회 2019 韓國音響學會誌 Vol.38 No.3
복잡한 회전 기계의 소음 상태 진단을 위한 다양한 연구가 수행되고 있다. 본 연구에서는 진동신호를 이용하여 블로워 모터의 효율적이고 객관적인 소음 상태진단을 위한 지수를 개발하였다. 블로워 모터의 이상 시 가장 흔히 나타나는 소음으로 틱/클릭 소음과 톤 소음이 있다. 발생 원인과 소음 특성에 따라 틱/클릭 소음의 상태 진단에는 시간-주파수 분석법을 그리고 톤 소음 상태 진단에는 주파수 영역에서의 평활화 기법을 이용하였다. 개발한 지수를 이용하여 블로워 모터의 소음 상태 진단을 수행하고 이를 전문가에 의한 진단 결과와 비교하였다. 그 결과 약 95 %의 일치율을 보였다. Various studies have been conducted for the diagnosis of noise condition of complex rotary machines. In this study, diagnosis index using vibration signal is developed for the efficient and objective assessment of noise condition of a blower motor. The noise most commonly caused by the abnormal blower motor are Tick/Click noise and Tone noise. According to cause and noise characteristics, time-frequency analysis is used to diagnose Tick/Click noise, and smoothing in frequency domain is used to diagnose tone noise condition. The noise condition of the blower motors were diagnosed using the developed index and these results are compared with the diagnostic results by the experts. As a result, the agreement rate was about 95 %.
격자 볼츠만 방법을 이용한 덕트 내 쌍둥이 직렬배열 사각 실린더에 의한 Aeolian 순음소음 고찰
이송준(Songjune Lee),정철웅(Cheolung Cheong) 한국소음진동공학회 2014 한국소음진동공학회 논문집 Vol.24 No.12
The lattice Boltzmann method(LBM) has attracted attention as an alternative numerical algorithm for solving fluid mechanics since the end of the 90’s. In these days, its intrinsic unsteadiness and rapid increase in computing power make the LBM be more applicable for computing flow-induced noise as well as fluid dynamics. The lattice Boltzmann method is a weakly compressible scheme, so we can get information about both aerodynamics and aeroacoustics from single simulation. In this paper, numerical analysis on Aeolian tone noise generated by tandem-twin square cylinders in duct is performed using the LBM. For simplicity, laminar two-dimensional fluid models are used. To verify the validity and accuracy of the current numerical techniques, numerical results for the laminar duct and the cylinder flows are compared with the analytical solution and the measurement, respectively. Then, aerodynamic noise of the twin tandem square cylinders is investigated. It is shown that the aerodynamic noise from the twin tandem square cylinders can be reduced by controlling the distance between the cylinders.
파수-주파수 분석을 이용한 자동차 옆 창문 표면 압력 섭동의 비압축성/압축성 성분 분해
이송준(Songjune Lee ),정철웅(Cheolung Cheong) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.7
The vehicle interior noise caused by exterior fluid flow field is one of critical issues for product developers in a design stage. Especially, turbulence and vortex flow around A-pillar and side mirror affect vehicle interior noise through a side window. The reliable numerical prediction of the noise in a vehicle cabin due to exterior flow requires distinguishing between the aerodynamic (incompressible) and the acoustic (compressible) surface pressures as well as accurate computation of surface pressure due to this flow, since the transmission characteristics of incompressible and compressible pressure waves are quite different from each other. In this paper, effective signal processing technique is proposed to separate them. First, the exterior flow field is computed by applying computational aeroacoustics techniques based on the Lattice Boltzmann method. Then, the wavenumber-frequency analysis is performed for the time-space pressure signals in order to characterize pressure fluctuations on the surface of a vehicle side window. The wavenumber-frequency diagrams of the power spectral density shows clearly two distinct regions corresponding to the hydrodynamic and the acoustic components of the surface pressure fluctuations. Lastly, decomposition of surface pressure fluctuation into incompressible and compressible ones is successfully accomplished by taking the inverse Fourier transform on the wavenumber-frequency diagrams.
고속열차의 바람소리에 따른 실내소음 예측을 위한 표면압력 섭동의 파수-주파수 분석
이송준(Songjune Lee),정철웅(Cheolung Cheong),김재환(Jaehwan Kim),김병희(Byung-hee Kim) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.1
Several contemporary studies have been carried on the challenge of predicting or reducing the exterior aerodynamic noise and interior noise induced by exterior air flow around high-speed trains. The achievement of reliable numerical prediction of noise in a passenger cabin due to exterior flow requires decomposition of the surface pressure fluctuations into hydrodynamic (incompressible) and the acoustic (compressible) fluctuation types, as well as the accurate computation of the near aeroacoustic field. This can be done because the transmission characteristics of each type of pressure wave through the cabin wall panels differ significantly. In this paper, wavenumber-frequency analysis is performed to accurately predict interior noise due to exterior aerodynamic noise from surface pressure fluctuations. First, large eddy simulation (LES) techniques were employed to predict the exterior flow field including an accurate near acoustic field around a high-speed train running at a speed of 300 ㎞/h in an open field. Then, pressure fluctuations on the train surface were decomposed and categorized as incompressible/compressible, and power spectral density spectra were obtained using wavenumber-frequency analysis. Finally, the separated incompressible and compressible surface pressure fields in the time-space domain were obtained from the inverse Fourier transform of each incompressible/compressible wavenumber-frequency spectrum.