• 제목/요약/키워드: Aerodynamic noises

검색결과 21건 처리시간 0.023초

차량용 터보차져의 컴프레서 BPF 소음 저감 (Compressor BPF noise reduction for an automotive turbocharger)

  • 박호일;엄상봉;서주봉;이승현
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2012년도 춘계학술대회 논문집
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    • pp.851-856
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    • 2012
  • Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. The mechanical noises are whine and howling noises, and the aerodynamic noises are BPF (blade-passing frequency), pulsation, surge, some special frequency noises. These noises are bothering passengers because their levels are higher or their frequencies are clearly separated from engine or vehicle noises. The noise investigated in this paper is a BPF noise induced by compressor wheels, whose frequency is the multiplication of the number of compressor wheel blades and its rotational speed. The noise is strongly dependent upon the geometry of wheels and the number of blades. This study tried to apply a groove close to the inlet side of compressor wheels in order to reduce the BPF noise. The groove has successfully reduced the noise of narrow band frequency of a turbocharger. It shows that the groove could reduce the wide band frequency noise, the compressor BPF noise with a best shape of the groove.

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CADET를 이용한 가로방향 힘의 Saturation에 대한 미사일의 성능해석 (Covariance analysis describing function technique for missile performance)

  • 김진호
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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    • pp.456-459
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    • 1993
  • CADET is used to analyze the performance of the missile. Miss distance is calculated for a given lateral fin force saturation level due to the aerodynamic characteristics, target acceleration, and glint and fading noises which is assumed as Gaussian noises. As .alpha.-.betha. filter is studied to attenuate the noises, the results are compared with those of without filter. For the easy simulation, the transfer function of a discrete .alpha.-.betha. filter is converted into the continuous model. Simulation results show that the results of CADET simulation is similar to those of Monte-Carlo simulation. Moreover CADET is the better in computing time demand.

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빔형성 기법을 이용한 고속철도차량의 공력소음특성 도출 연구 (Aerodynamic Noise Characteristics of High-speed Trains by the Beamforming Method)

  • 노희민;최성훈;고효인;홍석윤
    • 한국철도학회논문집
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    • 제15권3호
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    • pp.231-236
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    • 2012
  • 본 논문에서는 고속철도의 주행 시 발생하는 공력소음에 대한 특성을 도출하는 연구를 수행하였다. 우선, 마이크로폰 어레이 시스템을 이용하여 고속철도 차량의 주행 소음을 측정을 통해서, 주요 공력소음원이 고속철도 차량의 전두부, 팬토그래프, 차간 부위임을 확인하였다. 또한 측정한 데이터를 바탕으로 빔형성 방법을 이용하여 빔출력을 구하였으며, 푸리에 변환을 통해서 주파수 영역에서의 빔파워 스펙트럼을 도출하였다. 본 연구를 통해서 고속철도의 주요 공력 소음원인 전두부, 팬토그래프, 차간 부위에 대한 음압 특성이 빔형성 방법을 이용하여 도출되었다.

COMPUTATION OF AERODYNAMIC SOUNDS AT LOW MACH NUMBERS USING FINITE DIFFERENCE LATTICE BOLTZMANN METHOD

  • Kang H. K;Tsutahara M;Shikata K;Kim E. R;Kim Y. T;Lee Y. H
    • 한국전산유체공학회지
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    • 제10권1호
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    • pp.8-15
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    • 2005
  • Aerodynamic sounds generated by a uniform flow around a two-dimensional circular cylinder at Re=150 are simulated by applying the finite difference lattice Boltzmann method. Thethird-order-accurate up-wind scheme (UTOPIA) is used for the spatial derivatives, and the second-order-accurate Runge-Kutta scheme is applied for the time marching. We have succeed in capturing very small pressure fluctuations with the same frequency of the Karman vortex street compared with the pressure fluctuation around a circular cylinder. The propagation velocity of the acoustic waves shows that the points of peak pressure are biased upstream due to the Doppler effect in the uniform flow. For the downstream, on the other hand, it is faster. It is also apparent that the amplitude of sound pressure is proportional to r /sup -1/2/,r being the distance from the center of the circular cylinder. To investigate the effect of the lattice dependence, furthermore, 2D computations of the tone noises radiated by a square cylinder and NACA0012 with a blunt trailing edge at high incidence and low Reynolds number are also investigate.

에어컨 팬 BLDC 전동기의 음향공진에 관한 연구 (Study on Acoustic Resonance of Air-Conditioner Fan BLDC Motor)

  • 이홍주;김광석;권중학;방기창;황상문
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.212-217
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    • 2008
  • Acoustic noises generated during motor operation in mechanical system are from electromagnetic, mechanical, aerodynamic, and electrical sources. For identification of mechanical noise origins, misalignment, unbalance, fan shape, resonance, and vibration modes have been extensively considered to describe noise behavior. An experiment-based approach as well as a mathematical approach needs to be adopted for a realistic study into noise and vibration of the motor, because motor noise characteristics differ from type to type due to various noise sources. In this paper, a brushless DC motor for air-conditioner fan is analyzed by finite element method to identify noise source, and the analysis results are verified by experiments, and sensitivity analysis is performed by design of experiments.

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자동차 뒷 창문 개방에 의한 공명소음 전산해석 연구 (COMPUTATIONAL ANALYSIS ON DRONE NOISE OF AN AUTOMOBILE WITH OPENED REAR WINDOW)

  • 배익현;문영준
    • 한국전산유체공학회지
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    • 제18권2호
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    • pp.26-34
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    • 2013
  • In modern days, automobiles are the most important means of transportation. With the development of automobiles, noises generated during operation has been recognized as a significant factor of performance to provide drivers with better driving environment along with other passengers. In this study, drone noise(pulsating noise), generated at the rear window when its opened, is predicted to understand the physics of its phenomenon at various velocities. The compressible Navier-stokes equation will be used with $6^{th}$ order compact finite difference scheme to analyze the characteristics.

고속철도KTX(Korea Train Express)의 역구내진입 제동시 브레이크슈 사이의 마찰소음에 관한 연구 (Study on the Squeal Noise Between the Barake Shoes of the High Speed Railway(KTX))

  • 배원식;정인수;이동훈;유원희
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2007년도 추계학술대회 논문집
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    • pp.115-122
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    • 2007
  • The noises which occurs from the rolling stock can be divided largely into three classes and they are Rolling noise, Traction noise and Aerodynamic noise. In the event of braking the rolling stock which enter into the station, Brake shoes cause Fraction noise (braking noise) and excessive braking noise makes passengers and operators uncomfortable. This study is to reduce squeal noise and minimize displeasure by measuring the braking noise and defining the major noise sources and noise mechanism

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에어컨 홴 BLDC 전동기의 음향공진에 관한 연구 (Study on Acoustic Resonance of Air-conditioner Fan BLDC Motor)

  • 이홍주;권중학;이창민;황건용;황상문
    • 한국소음진동공학회논문집
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    • 제19권9호
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    • pp.863-869
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    • 2009
  • Acoustic noises generated during motor operation in mechanical system are from electromagnetic, mechanical, aerodynamic and electrical sources. For identification of mechanical noise origins, misalignment, unbalance, fan shape, resonance, and vibration modes have been extensively considered to describe noise behavior. An experiment-based approach as well as a mathematical approach needs to be adopted for a realistic study into noise and vibration of the motor, because motor noise characteristics differ from type to type due to various noise sources. This paper analyzes noise characteristics of a brushless DC motor for air-conditioner fan, and proves that the test motor noise originates from acoustic modes of airspace in the motor. The motor noise sensitivity analysis by design of experiments reveals that the noise characteristics are closely related to switching frequency and frame thickness.

경량전철 교량 상부구조의 열차주행에 대한 진동 및 소음 분석 (The Estimation of Structural-Borne Noise and Vibration of the Bridge under the Passage of the Light Rail Transit)

  • 여인호;정원석;김성춘;김성일
    • 한국철도학회논문집
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    • 제10권1호
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    • pp.22-28
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    • 2007
  • During the passage of the train, the railway bridge undergoes vibration and noise. The noise of railway bridge can be occurred from various sources. The wheel-rail contact, noise from machinery parts, structural-borne noise, pantagraph noise and aerodynamic noise of the train work in combination. Running train is one of the most important factors for railway bridge vibration. The repeated forces with equidistant axles cause the magnification of dynamic responses which relates with maintenance of the track structure and structure-borne noises. The noise problem is one of the most important issues in services of light rail transit system which usually passes through towns. In the present study, The vibration and noise of the LRT bridge will be investigated with utilizing dynamics responses from moving train as input data for noise analysis.

소형 전술급 무인항공기 프로펠러의 이산소음 수치해석 (Discrete Noise Prediction of Small-Scale Propeller for a Tactical Unmanned Aerial Vehicle)

  • 유기완
    • 한국군사과학기술학회지
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    • 제21권6호
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    • pp.790-798
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    • 2018
  • Discrete noise signals from a small scale tactical unmanned aerial vehicle(UAV) propeller were predicted numerically using time domain approach. Two-bladed 29 inch propeller in diameter and 150 kgf in gross weight were used for main parameters of the UAV based on the actual size of the similar scale vehicle. Panel method and Farassat formula A1 were adopted for aerodynamic and aeroacoustic analysis respectively. Time domain signals of both thickness and loading noises were transformed into frequency domain to analyze the discrete noise characteristics. Directivity pattern in a plane perpendicular to the rotating disc plane and attenuation of noise intensity according to double distance were also presented.