• Title, Summary, Keyword: Resonance Frequency Analysis

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FEM acoustic modal analysis due to location of acoustic baffles to avoid acoustic resonance in the tube bank of boiler for power plant (보일러 튜브군의 음향공진 회피를 위한 음향배플의 위치에 따른 FEM 음향모드해석)

  • Ahn, Sung-Jong;Ju, Young-Ho;Kim, Cheol-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.150-154
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    • 2012
  • A flow induced mechanical vibration and acoustic resonance should be considered at design stage because they are mainly occurred in the tube bank of boiler. Acoustic resonance is occurred when the vortex shedding frequency of tube bank coincides with the acoustic natural frequency of the cavity. Effective solution to avoid acoustic resonance is installing acoustic baffles in the tube banks parallelly inside of the flow cavity. Thus, location and number of acoustic baffles should be exactly calculated to eliminate the acoustic resonance. This paper presents case study of acoustic resonance due to inappropriate number and location of acoustic baffles. Measured frequency and mode in the study is verified by FEM acoustic modal analysis. The number and location of acoustic baffles to avoid acoustic resonance are calculated by using FEM acoustic modal analysis.

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Fluid-Structure Interaction (FSI) Modal Analysis to Avoid Resonance of Cylinder Type Vertical Pump at Power Plant (원통형 수직 펌프의 공진회피를 위한 접수진동해석)

  • Lee, Jae-Hwan;Wang, Ji-Teng;Maring, Kothilngam
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.4
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    • pp.321-329
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    • 2018
  • Resonance phenomena occurs at large vertical pump which is operating to cool down the hot steam using sea water in the power plant. To avoid the resonance, the natural frequency needs to be isolated about 20% from motor operating speed. Yet, excessive vibration occurs especially at low tide. At first, natural frequency of the whole pump system and each part is calculated using ANSYS. As it is revealed in the previous journal papers that only circular pipe part is related to resonance, the FSI technique is applied for free vibration analysis. The natural frequency is reduced to 60% (compared to that) of the frequency measured in air as it is similar to other published results. And the frequency obtained by finite element analysis is almost same to that obtained from modal test. Based on the accurate finite element model and analysis, design change is tried to avoid the resonance by changing the thickness of pipe and base supporting plate. In stead of doing optimization process, design sensitivity is computed and used to find such designs to avoid resonance.

Resonance Frequency Extraction of Full-scale Radar Targets Using Time-Frequency Analysis (시간-주파수 해석법을 이용한 실스케일 레이더 표적의 공진주파수 추출)

  • Kim, In-Ha;Choi, In-Sik
    • 한국정보기술학회논문지
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    • v.15 no.6
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    • pp.87-94
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    • 2017
  • The resonance frequency is observed in the late-time response of radar signal, and it is a unique frequency determined by the physical length of the target. In this paper, we conducted a simulation in the HF band of 0.2 ~ 28 MHz to observe the resonance frequency. First, the RCS(radar cross section) of four full-scale targets were obtained using RCS analysis tool FEKO. Then, results for resonance frequency extraction were compared and analyzed using the time-frequency analysis methods such as CWT(Continuous Wavelet Transform) and AWT(Adaptive Wavelet Transform). The radar structure was considered in the monostatic and bistatic $150^{\circ}$. By the comparison of the results, we can see that the resonance frequencies extracted from the two techniques are almost same, but the resolution in the time and frequency domain is better in the case of the AWT.

Analysis of Current Control Stability using PI Control in Synchronous Reference Frame for Grid-Connected Inverter with LCL Filter (LCL 필터를 사용하는 계통연계형 인버터의 동기좌표계 PI 전류제어 안정도 해석)

  • Jo, Jongmin;Lee, Taejin;Yun, Donghyun;Cha, Hanju
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.2
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    • pp.168-174
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    • 2016
  • In this paper, current control using PI controller in the synchronous reference frame is analyzed through the relationship among bandwidth, resonance frequency, and sampling frequency in the grid-connected inverter with LCL filter. Stability is investigated by using bode plot in frequency domain and root locus in discrete domain. The feedback variable is the grid current, which is regulated by the PI controller in the synchronous reference frame. System delay is modeled as 1.5Ts, which contains computational and PWM modulator delay. Two resonance frequencies are given at 815 Hz and 3.16 kHz from LCL filter parameters. Sufficient phase and gain margins can be obtained to guarantee stable current control, in case that resonance frequency is above one-sixth of the sampling frequency. Unstable current control is performed when resonance frequency is below one-sixth of the sampling frequency. Analysis results of stability from frequency response and discrete response is the same regardless of resonance frequency. Finally, stability of current control based on theoretical analysis is clearly verified through simulation and experiment in grid-connected inverters with LCL filter.

Relationship Between the Resonance Frequency and QTS for Microspeaker (마이크로스피커에서 공명진동수와 QTS 사이의 연관성)

  • Oh, Sei-Jin
    • Korean Journal of Materials Research
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    • v.21 no.7
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    • pp.403-409
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    • 2011
  • Micro speakers are used to reproduce sound in small electric and information and communications devices, such as cellular phones, PMPs, and MP3 players. The acoustical properties and sound quality, which are changed due to the decreased size of the speaker, are often adjusted varying the type and thickness of the diaphragm. The most widely used diaphragm material is thin polymer. It was previously reported by the author of this paper that the resonance frequency of a micro speaker is changed by the type and thickness of a polymer diaphragm. In this paper, the frequency response near the resonance frequency of a micro speaker was studied as functions of the type and thickness of the polymer diaphragm. While $R_{max}$ and $R_{DC}$ were affected by the type and thickness, an analysis of the electrical impedance curve revealed that $R_o(= R_{max}/R_{DC})$ and ${\Delta}f$ were not changed. Thus, $Q_{TS}$ which was function of $R_o$, ${\Delta}f$, and the resonance frequency, is only related to the resonance frequency. The increase of the resonance frequency led to a proportional rise of $Q_{TS}$. The change of the frequency response near the resonance frequency was not dependent on the type or thickness of the polymer diaphragm, but was affected by the resonance frequency.

A Study on the Subsynchronous Resonance by Flexible Frequency Operation (주파수 유연화 운영에 따른 발전기 축 비틀림에 관한 연구)

  • Cho, Yoon-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.29 no.4
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    • pp.62-68
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    • 2015
  • Subsynchronous Resonance is a condition where the electrical power systems composed of generator and transmission line exchange energy with mechanical turbine-generator system at the frequency of the combined below the subsynchronous frequency. Therefore, the frequency of power systems should be associated with the subsynchronous resonance. This paper describes subsynchronous resonance by flexible frequency operation. It focuses on the characteristics and behavior of subsynchronous resonance. The subsynchronous resonance is being conducted by real-time digital simulator and the IEEE benchmark model for subsynchronous resonance have been utilized for the test systems.

Fatigue Analysis of Vehicle Chassis Component Considering Resonance Frequency (공진 주파수를 고려한 차량 섀시 부품의 피로해석)

  • Lee Sang Beom;Yim Hong Jae
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.6
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    • pp.94-101
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    • 2004
  • The purpose of this raper is to assess the benefits of frequency domain fatigue analysis and compare it with more conventional time domain techniques. The multi-body dynamic analysis, FE analysis and fatigue life prediction technique are applied for the frequency domain fatigue analysis. To obtain the dynamic load history used in the frequency domain fatigue analysis, the computer simulations running over typical road Profiles are carried out by utilizing vehicle dynamic model. The fatigue life estimation for the rear suspension system of small-sized passenger car is performed by using resonance durability analysis technique, and the estimation results are compared with the conventional quasi-static durability analysis results. For the pothole simulation, the percent changes, of the fatigue life between the two durability analysis techniques don't exceed 10%. But for the Belgian road simulation because of the resonance effect, the fatigue life using the resonance durability analysis technique are much smaller estimated than the quasi-static durability analysis results.

Frequency Characteristics Variation of a Class I Flextensional Transducer (Class I Flextensional 변환기의 주파수 특성 변화)

  • Kang, Kook-Jin;Paik, Jong-Hoo;Lee, Young-Jin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.2
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    • pp.142-150
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    • 2009
  • We constructed a Class I flextensional transducer, and analyzed the variation of the resonance frequency of the transducer in relation to its structural and material variables. We used the FEM for the analysis. Total length of the transducer, thickness and material properties of the shell have large effects on the resonance frequency. While outer radius of the ceramic stack and material properties of the ceramic stack have no effect on the resonance frequency. In addition, the validation of the FE model was verified by manufacturing and comparison of the impedance analysis. Results of the present work can be utilized to design a Class I flextensional transducers of various resonance frequency.

Study on Moonpool Resonance Effect on Motion of Modern Compact Drillship

  • Yang, Seung Ho;Yang, Young Jun;Lee, Sang Beom;Do, Jitae;Kwon, Sun Hong
    • Journal of Ocean Engineering and Technology
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    • v.27 no.3
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    • pp.53-60
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    • 2013
  • A drillship is a representative floating offshore installation. The boom in oil and gas field development has dramatically increased the demands for drillships. Drillships have a moonpool in the center area of the ship for the purpose of drilling. This moonpool has an effect on the seakeeping performance of a drillship in the vicinity of the resonance frequency. Because of the moonpool, drillships act in different resonance modes, called the sloshing mode and piston mode. The objective of this study was to find the moonpool effect on the motion of a drillship through the motion analysis of a currently operating modern compact drillship. The predicted resonance frequencies based on Molin's theoretical formula, Fukuda's empirical formula, and BEM-based numerical analysis are compared. The accuracy of the predictions using the theoretical and empirical formulas is compared with the numerical analysis and evaluated. In the case of the piston mode, the difference between the resonance frequency from theoretical formula and the resonance frequency from the numerical analysis is analyzed. The resonance frequency formula for more a complex moonpool geometry such as a moonpool with a cofferdam is necessarily emphasized.

Resonance Characteristics of Fruits in Packaging System for Parcel Delivery Service (택배용 포장시스템이 적용된 과실의 공진특성)

  • Jung, Hyun Mo;Kim, Su Il
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.21 no.3
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    • pp.91-96
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    • 2015
  • Fruit and vegetables are subjected to complex dynamic stresses in the transportation environment. During a long journey from the production area to customers using parcel delivery service, there is always some degree of vibration present. Vibration inputs are transmitted from the vehicle through the packaging to the fruit. Inside, these cause sustained bouncing of fruits against each other and container wall. These steady state vibration input may cause serous fruit injury, and this damage is particularly severe whenever the fruit inside the package is free to bounce, and is vibrated at its resonance frequency. The determination of the resonance frequencies of the fruit and vegetables may help the packaging designer to determine the proper packaging system providing adequate protection for the fruit, and to understand the complex interaction between the components of fruit when they relate to expected transportation vibration inputs. Instrumentation and technologies are described for determining the vibration response characteristics of the fruits with frequency range 3 to 150 Hz. The resonance frequency of the pear ranged from 53 to 102 Hz and the amplitude at resonance was between 1.08 and 2.48 G. The resonance frequency and amplitude at resonance decreased with the increase of the sample mass, and they were slightly affected by mechanical properties such as bioyield deformation and rupture deformation. Regression analysis was performed among the relatively high correlated parameters from the results of correlation coefficient analysis.