• Title/Summary/Keyword: cavity vibration

Search Result 242, Processing Time 0.022 seconds

Estimation of Cavity Vibration Frequency Using Adaptive Filters for Gas Flow Measurement (적응 필터를 이용한 공동진동주파수 추정에 의한 기체 유량측정)

  • 남현도
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.17 no.5
    • /
    • pp.134-140
    • /
    • 2003
  • In this paper, a hardware implementation of gas flow meter for accuracy improvement and saving repair costs at a field is investigated. An adaptive filter using LMS algorithms for estimating cavity vibration frequencies in noisy environments is also studied. The proposed cavity gas flow meter measures cavity sound signals in gas flow tube using microphone and signal processing systems estimate the cavity vibration frequency from the measured signal. The flow velocity and flow quantity can be calculated using the estimated cavity vibration frequency. Since cavity vibration frequency is corrupted by the environmental noise, an adaptive filter using NLMS algorithms is used for cancelling the environmental noise. Experiments using 1MS32OC32 digital signal processor are performed to show the effectiveness of the proposed system.

Study on Interior Noise Transfer Path Analysis by Tire Cavity Resonance (타이어 공동의 공명에 의한 차량 실내음 전달경로 연구)

  • Lee, Sang-Ju;Kang, Byun-Seok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2005.11b
    • /
    • pp.129-133
    • /
    • 2005
  • Vibration transmitted through rolling tire is a major source of road noise in vehicle interior noise on the range of low frequency.($0{\sim}500Hz$) Among various road noises, tire cavity noise has very peak on $200{\sim}250Hz$. And generally it is generated by cavity resonance of tire. In this paper, tire cut-sample is used to calculate the tire cavity frequency. Cavity resonance frequency of tire is measured through vertical/tangential forces at load cell of axle using drum cleat impact. This method is useful to find cavity peak because measured forces do not have complex peaks. And changing the test conditions (air inflation, loads), tire cavity resonance characteristics are identified. Finally, vehicle interior noise is measured as tire/vehicle are changing. As difference of tire vertical force is bigger, interior noise level is higher at cavity frequency. Also we can assume that vehicle sensitivity is important factor at tire cavity noise.

  • PDF

The Study of Reduction Technologies of Tire Cavity Resonance Noise (타이어 공명 소음(Tire Cavity Resonance Noise) 저감에 관한 연구)

  • Bang, M.J.;Choi, S.I.;Choo, K.C.;Lee, H.J.;Son, C.E.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2008.11a
    • /
    • pp.596-599
    • /
    • 2008
  • Traditionally, tire made a role of function, which is supporting vehicle load, making brake, transferring traction, etc. But tire is a part of vehicle design, nowadays. In accordance with this market trend, customers need a wide tread design tire (i.e. low series tire). Generally low Series Tire means stiffer than general tire. That brings out increasing road noise. (Especially tire cavity resonance noise) Tire noise is divided in structure home noise and air borne noise. Tire cavity resonance noise (structure home noise) come from vibration between tire and vehicle. In the study, we investigated that tire cavity resonance noise is affected by stiffness of tread and sidewall.

  • PDF

Noise and vibration reductions in exhaust duct system of cogeneration power plants (열병합발전소 배기 덕트 시스템의 소음 진동 저감)

  • Kim, W.H.;Joo, W.H.;Bae, J.G.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.11a
    • /
    • pp.641-646
    • /
    • 2004
  • Noise and vibration was encountered in exhaust duct system which is connected with a gas turbine and a heat recovery steam generator(HRSG) of a cogeneration power plants. Especially, these problems occurred when water was added to the fuel injection to reduce NOx contents of the exhaust gas. Through the cavity mode analysis and measurements, It was concluded that these problems occurred due to the acoustic resonance between the duct cavity mode and the excitation force induced by turbulent gas flow during water injection. To reduce the noise and vibration, optimal baffle plate to change the cavity mode was installed inside of duct and noise levels of about 8 dB(A) are reduced in duct system. The effects of baffle plate and guide vane to the HRSG or inlet duct vibration were also evaluated and it was verified that there is no relation to the resonance phenomena. So, vibration of inlet duct was easily reduced by the reinforcement of structures.

  • PDF

Numerical Investigation of the Cover-Plates Effects on the Rectangular Open Cavity (직사격형 공동에서 덮개 효과에 대한 수치적 연구)

  • 허대녕;이덕주
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2001.05a
    • /
    • pp.457-464
    • /
    • 2001
  • The aeroacoustic phenomena in the simple rectangular open cavity are well published by many researchers. But the geometry shapes of aircraft landing gear wells, weapon bays, etc. are more complicate than that of the simple retangular cavity. They are more similar to the cavity having cover-plates at adges, or Helmholtz resonator. Therefore, the effects of cover-plates existing on edges of rectangular open cavity are numerically investigated in this paper. The compressible Navier-Stokes equations are solved for two-dimensional cavities with laminar boundary layers upstream. The high-order and high-resolution numerical schemes are used for the evaluation of spatial derivatives and the time integration. Physically correct numerical boundary conditions and buffer zone techniques are implemented to produce time-accurate solutions in the whole computation domain. The computational domain is large enough to directly resolve a portion of the radiated acoustic field. Results show that the cover-plates existing on edges of cavity reduce the noise convected from cavity, make the frequency of noise become higher, and change the directivity pattern. So these results can be used in the design of a low noise cavity.

  • PDF

3-D Vibration Characteristics of Radial Tire for Passenger Car under Fixed Axle (축으로 고정된 승용차용 레디얼 타이어의 3차원 진동특성)

  • 김용우;남진영
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.12 no.3
    • /
    • pp.228-235
    • /
    • 2002
  • Two kinds of experimental modal analyses have been performed on a radial tire for passenger car under fixed axle. One is the modal analysis to obtain three-dimensional modes of tire using accelerometers and the other is the one to identify cavity resonance frequency using a pressure sensor. From the first analysis, we have obtained three-dimensional natural modes and their decomposed 3-D modes in each direction, which make it possible to grasp the features of the modes that cannot be identified in the conventional 2-D modes and to classify the vibrationall modes into symmetric, non-symmetric, and antisymmetric modes in a simple way by using the experimental results. From the second experimental analysis, the cavity resonance frequency is found. Coomparing the results of the two analyses, we have Identified the three-dimensional mode of the cavity resonance. We also haute shown that natural frequencies of structural vibration depends on inflation Pressure while the cavity resonance does not.

Experiments for the Acoustic Source Localization in 2D Cavity Flow (2차원 공동 유동에서의 소음원 위치 판별을 위한 실험적 연구)

  • Lee, Jaehyung;Park, Kyu-Chol;Choi, Jong-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.14 no.12
    • /
    • pp.1241-1248
    • /
    • 2004
  • This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone array. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in an anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures and their spectral contents are affected by the cavity parameter L/D.

Acoustic Source Localization in 2D Cavity Flow using a Phased Microphone Array (마이크로폰 어레이를 이용한 2차원 공동 유동에 대한 소음원 규명)

  • 이재형;최종수;박규철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2003.05a
    • /
    • pp.701-708
    • /
    • 2003
  • This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone way. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures. It is also shown that their spectral contents are affected by the cavity parameter L/D.

  • PDF

Optimal design of a piezoelectric smart structure for cabin noise control (실내소음제어를 위한 압전지능구조물의 최적 설계)

  • 고범진;김재환;최승복
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 1997.10a
    • /
    • pp.445-450
    • /
    • 1997
  • Optimal design of a piezoelectric smart structure is studied for cabin noise control. A cubic shaped acoustic cavity with a flat plate which covers one side is taken as the problem. The sensor signal is returned to the actuator through a negative gain. The acoustic cavity is modeled using the modal approach which represents the pressure fields in the cavity as a sum of mode shapes of the cavity with unknown coefficients. By using orthogonality of the mode shapes of the cavity, finite element equation for the structure with the influence of the acoustic cavity is derived. The objective function is the average pressure at a certain region, so-called silent zone, in the cavity and the design variables are the locations and sizes of the piezoelectric actuator and sensor. The optimal design is performed at several frequencies and the results show a remarkable noise reduction.

  • PDF

Real-time Subtle Vibration Sensing of Optical Fiber Cable based on External-cavity Frequency-swept Laser (외부공진형 광주파수가변 레이저를 이용한 실시간 광섬유 케이블의 미세 진동 측정 연구)

  • Jang, Hansol;Kim, Chang-Seok
    • Journal of the Korean Society of Industry Convergence
    • /
    • v.23 no.6_2
    • /
    • pp.943-948
    • /
    • 2020
  • In this paper, we developed a fiber optic interferometer system based on frequency-swept laser. This frequency-swept laser with an external-cavity structure can generate a high coherent light with a linewidth of 132 kHz at 1552 nm. It also shows a superior swept linearity of R2 = 0.99995 under repetition rate of 200 kHz due to absence of mechanical moving parts in the laser cavity. By using a piezoelectric fiber optic stretcher, various vibration experiments were implemented, such as 0.5 to 2.0 kHz vibration signals with intervals of 0.5 kHz, with a sampling rate of 7 kHz. Real-time peak tracking can be successfully recovered according to the applied vibration frequency with high linearity of R2 = 0.99983.