• Title/Summary/Keyword: 흡수 감쇠

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A Study on the Acoustic Damping Characteristics of Acoustic Cavities in a Liquid Rocket Engine (로켓엔진에서 음향공의 음향학적 감쇠능력에 대한 고찰)

  • Kim Hong Jip;Kim Seong-Ku;Choi Hwan Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.291-298
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    • 2005
  • Linear acoustic analysis has been performed to elucidate damping characteristics of acoustic cavities. Results have shown that resonant frequencies of acoustic cavity obtained by classical theoretic approach and present linear analysis are somewhat different from each other. This difference is due to the limitation of classical theory. To quantify the damping characteristics, acoustic impedance has been introduced and resultant absorption and conductance have been evaluated. Satisfactory agreement has been achieved with previous experiment. Finally the design procedure for optimal tuning of acoustic cavity has been established

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Study on a cavity ring-down spectrometer with continuous wave laser sources (연속발진 레이저를 이용한 공동 광자감쇠 분광기 연구)

  • 유용심;한재원;김재완;이재용;이해웅
    • Korean Journal of Optics and Photonics
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    • v.9 no.4
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    • pp.240-244
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    • 1998
  • Cavity ring-down spectroscopy (CRDS) is a high-sensitive laser spectroscopic technique capable of measuring concentrations of trace gases. We have demonstrated a new design of the CRDS spectrometer with a continuous wave (CW) laser. The ring-dwon signal is produced through blocking the incident CW laser by scanning the cavity length fast toward off-resonance iwth PZT (piezoelectric transducer). We have also measured an absorption spectrum of acetylene overtone transitions near 570 nm at the pressure of 2700 Pa, and the minimum detectable absorption coefficient has been found to be about $3{\times}10^{-9}\cm^{-1}$.

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Effect of Swirl Injector with Variable Backhole on Acoustic Damping in Liquid Rocket Engine (액체로켓 스월인젝터의 음향학적 감쇠기능)

  • ;;;;;;Bazarov, V. G.
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.8
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    • pp.79-86
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    • 2006
  • Swirl injector with adjustable backhole length was analyzed to suppress high-frequency combustion instability in Liquid Rocket Engines. In order to analyze the effect of variable backhole injector as an acoustic absorber, backhole injector was regarded as a quarter-wave resonator. As a result of theoretical approaches and acoustic tests, backhole injector with adjustable length could decrease the unstable modes of combustion chamber. And the damping efficiency was estimated by measuring damping rates experimentally.

CFD Analysis on the Continuous and Variable Damping Characteristics of a Semi-Active Shock Absorber (반능동형 충격흡수기의 연속가변 감쇠특성에 대한 CFD 해석)

  • 윤준원
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.101-108
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    • 2004
  • Recently, a semi-active shock absorber has been taking interest because of its low cost and simple structure than the active one. CFD analysis has been conducted to investigate the continuous and variable damping characteristics of the semi-active shock absorber. Also, the flow resistance characteristics of a spool valve has been examined to identify individual parameters(namely, exponent and discharge coefficient) of pressure-flow rate relation needed for the accurate valve modeling. The flow field in the damping valve was simulated using the commercial code, CFX-5.3. The numerical results showed reasonable agreement with the experimental outputs. The pressure distribution with the variation of spool opening length and volume flow rate were discussed in detail. And the continuous and variable damping performance was found clearly. The individual parameters of spool valve were obtained as a function of orifice area. The exponent and discharge coefficient were fitted in with the first and the third polynomial respectively.

A Study on the Stroke Sensitive Shock Absorber (변위 감응형 충격흡수기에 관한 연구)

  • 박재우;주동우;김영호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.85-90
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    • 1997
  • In the stroke sensitive shock absorber, the oil path is formed along the internal cylinder surface to make the eli flow during piston's upper-lower reciprocation movement. With constraint to the conventional shock absorbers which show one dynamic characteristic curve, stroke sensitive shock absorber shows two kins of dynamic characteristic according to the stroke, In the study, analysis on the damping force generation process and dynamic behaviour characteristics of stroke sensitive shock absorber is performed, the valve characteristics being considered more precise information about design and damping performance analysis.

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The Effect of Impact Absorbing System Deformation According to the Variation of Cylinder Wall Dimensions on Damping Coefficient (실린더 벽면 치수변화에 따른 변형이 충격흡수장치 감쇠계수에 미치는 영향)

  • 한근조;안찬우;안성찬;심재준;김성윤
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.765-768
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    • 1997
  • Many malfunctions take place in container crane spreader due to impact. So we designed a hydraulic impact absorbing equipment to absorb the impact and we studied the change of damping coefficient with respect to the variation of dimensions of oil-cylinder wall. When we design the dimension of hydraulic cylinder wall considering the displacement on the wall, the value of it over 20mm didn't affect the damping coefficient.

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Damping Force Modeling of Shock Absorbers Using Hyperbolic tangent (Hyperbolic tangent를 이용한 충격 흡수기 감쇠력 모델 연구)

  • 서정원;한형석;노규석;허승진;김기훈
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1479-1482
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    • 2003
  • The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber. and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model. the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

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Impact Analysis For a 2-DOF Shock Absorbing System with Multi-Step Damping Coefficient (다단계 감쇠계수를 갖는 2자유도계 충격흡수장치의 충격해석)

  • 김성윤;심재준;한동섭;안성찬;한근조;안찬우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.871-874
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    • 2002
  • Many malfunctions take place in container crane spreader due to impact. So we designed a 2DOF hydraulic impact absorbing system with multi-step damping coefficient and studied the effect of orifice's interval and damping coefficient. The damping coefficient of upper piston was found to be 180 N.s/m, and the orifice's interval to be 9mm, the max reaction force and the average reaction force might be lowest. Compared with a general 2-DOF impact absorbing system, the max reaction force reduced by 46%., and average reaction force reduced by 5%.

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A Study on the Nonlinear Dynamic Modeling and Analysis of Damping Force Characteristics of Automotive Shock Absorber (차량용 충격흡수기의 비선형 동적거동 모델링 및 감쇠력 특성해석에 대한 연구)

  • 이춘태;곽동훈;정봉호;이지걸
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.1
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    • pp.104-111
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    • 2003
  • The performance of shock absorber is directly related to the car behaviour and performance, both for handling and comfort. In this study, a mathematical nonlinear dynamic model and computational method are introduced to study the flow and performance of shock absorber. The flow characteristics of components(piston and body valve) are investigated and applied to dynamic modeling of shock absorber to predict the damping force. The simulation results agree with the test data well. The shock absorber model proposed in this paper is applicable as a part of a full vehicle suspension simulation.

Study on Damping Coefficient of Shock Absorber with Magnetic Effects (자기효과를 이용한 충격흡수장치의 감쇠계수에 관한 연구)

  • Yi, Mi-Seon;Bae, Jae-Sung;Hwang, Jae-Hyuk;Hwang, Do-Sun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.9
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    • pp.832-838
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    • 2011
  • The shock absorber with magnetic effect is suggested for a lunar lander. The shock absorber consists of a metal tube, a piston rod, and several permanent magnets moved by a piston rod in the tube, and the shock energy can be dispersed and dissipated by magnetic effects such as the magnetic force existed between a metal and magnets and the eddy current effect generated by a relative motion with a conductor and magnets. Besides, the shock-absorbing effect similar to that of a coil spring can be obtained by arranging the magnets in line, which are facing the same polar each other. The device has a very simple structure and is usable in space due to the unnecessariness of any oil or gas. The shock absorber was designed and manufactured for experiments and its spring and damping characteristics were studied by the theoretical, analytical and experimental methods.