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  • Title/Summary/Keyword: Fluid pipeline

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Dynamic Respeonse of Hydraulic Pipe Lines with a Relative Small Diameter (직경이 작은 유압관로에서의 동특성)

  • 유영태
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.8 no.4
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    • pp.38-44
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    • 1999
  • This paper primarily directed toward analyzing the frequency response in hydraulic pipe lines with a small diameter. The exact solution to the frequency response is obtained by using the complicated transfer function. The discrepancy with the exact and the approximate is small so the approximation solution is adopted to compare the experimental results with the theoretical analysis. In this experiment the input frequency was generated by the frequency generator with the ball valve and speed controller. In order to compare the theoretical were forms with the experimental ones the trace obtained from the oscilloscope is photographed, The diameter the length of lines and input pressure amplitude are varied to investigate their effects,. the experiment results show that th values of dimensionless parameter are very affected to the phase delay and guide response time in the design of pressure manifold to measure the pressure of hydraulic pipelines.

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AN INVERSTIGATION OF THE DYNAMIC ERRORS OF THE REMOTE-INSTANTANEOUS FLOWRATE MEASUREMENT DUE TO PARAMETER CHANGES

  • Kim, Do-Tae;Yokota, Shinichi;Nakano, Kazuo
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10b
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    • pp.1712-1717
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    • 1991
  • The paper describes estimation errors of unsteady flowrate measurements due to parameter changes in a quasi-remote instantaneous flowrate measurement method (abbreviate as QIFM) and an instantaneous flowrate measurement method using two points pressure measurements (abbreviate as TPFM). By introducing error performance index, the influence of parameter changes on the accuracy, and dynamic response of the estimated unsteady flowrate are evaluated. Of four parameters, the variation of the length of the pipeline and speed of sound produce large errors in the estimated unsteady flowrate during transient periods. The effect of kinematic viscosity of the working fluid(oil) is relatively insensitive in unsteady flowrate estimation.

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Vibrational Characteristics of the Gas Pipelines Conveying Flow (유체가 흐르는 가스파이프의 진동 특성)

  • Kim, Kyung-Tae;Lee, Sung-Soo;Lee, Seong-Woo
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.2
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    • pp.337-343
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    • 2012
  • This work investigates the vibrational characteristics of the underground gas pipelines. Experiments were conducted to analyze the effects of various parameters on the vibrational characteristics from the emergency detection point of view. Influences of the various types of impact exerted on the pipe, height of free fall and measuring locations were analyzed. Especially, the difference between the vibrational signal generated by the direct impact on the pipe and the ambient noise was successfully identified. To validate the experimental observation, computer simulation was also performed with constant properties(elasticity, fluid velocity and internal pressure) which are directly conjectured from the accompanying experiment with a real pipe system.

The Characteristics of Pulsating Flow in a Hydraulic Pipe (유압관로에서 맥동유동 특성에 관한 연구)

  • 모양우;유영태;김지화
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.7
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    • pp.653-665
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    • 2001
  • The characteristics of the pulsating flow in a hydraulic pipe have been investigated. It is necessary to study the power control of the power transmission system in the landing gear system of aircraft and the design of robots. In this system, the power transmission pipeline is composed of a hydraulic system, and the operating flow is unsteady flow. The wave equation varying with frequency is analyzed in order to investigate the characteristics of unsteady flow in such a pipe. This wave equation involves the propagation coefficient in terns of frequency and viscosity. The theoretical result of this wave equation are compared with experimental result. Each wave equation, varying with the propagation coefficient, is analyzed theoretically. then, a sinusoidal wave generator is built in order to make better sinusoidal waves, and a rectifier is built to eliminate the noise from the hydraulic pump. The theoretical results of the wave equation in the flow of viscous fluid agree well with experimental results.

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The Vibration Characteristic of Large Main Steam Pipelines in Power Plant (발전소의 대형 주증기배관의 진동 특성)

  • Kim, Yeon-Whan;Lee, Hyun
    • Journal of KSNVE
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    • v.6 no.6
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    • pp.709-715
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    • 1996
  • In recent years, the piping vibration in many Power Plants is being increased by the aged generating facilities due to a long time use. Generally, the pressure fluctuations associated with the flow-induced excitations in this case are broadband in nature. Mainly, the dominant sources of vibration are a vortex-shedding, plane waves and boundary layer turbulence. The peak level of the spectrum is proportional to the dynamic head. A severe disturbance in pipeline results in the generation of intense broadband internal sound waves which can propagate through the piping system. The characteristic frequencies of operating loads of 20%, 57%, 70%, 100% are 4 - 6 Hz and coincide with the results from impact hammering test and FEM analysis. We chose the wire energy absorbing rope restraint as a vibration reduction method after reviewing the various conditions such as site, installing space and economic cost etc. After installation, the vibration level was reduced about 54% in velocity.

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Pinpointing of Leakage Location Using Pipe-fluid Coupled Vibration (파이프-유체의 연성진동을 이용한 누수위치 식별연구)

  • 이영섭;윤동진
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.2
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    • pp.95-104
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    • 2004
  • Leaks in underground pipelines can cause social, environmental and economical problems. One of relevant countermeasures against leaks is to find and repair of leak points of the pipes. Leak noise is a good source to identify the location of leak points of the pipelines. Although there have been several methods to detect the leak location with leak noise, such as listening rods, hydrophones or ground microphones, they have not been so efficient tools. In this paper, accelermeters aroused to detect leak locations which could provide an easier and more efficient method. Filtering, signal processing and algorithm of raw input data from sensors for the detection of leak location are described. A 120m-long and a 70m-long experimental pipeline systems are installed and the results with the systems show that the algorithm with the accelerometers offers accurate pinpointing for leaks location detection. Theoretical analysis of sound wave propagation speed of water in underground pipes, which is critically important in leak locating, is also described.

Pressure Ripple Reduction in Hydrostatic Transmissions by Using a Hydraulic Filter (맥동흡수용 유압필터에 의한 유압전동장치의 압력맥동 감쇠)

  • 김도태
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.11 no.3
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    • pp.33-38
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    • 2002
  • This paper deals with pressure ripple attenuation far separated-type Hydrostatic Transmission (HST) consisting ova variable axial piston pump connected in an open loop to a fried displacement axial piston motor. Pressure ripples in HST is major source of vibration which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube tripe hydraulic filter is proposed to attenuate pressure ripples with the high frequencies components to achieve better noise reduction in HST. The basic principle of a hydraulic filter is allied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimentally shown that the hydraulic filter attenuates about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and provide a means of designing a quieter HST.

The Numerical Analysis about the Hunting Factors of the Orifice Meter (오리피스 유량계의 헌팅 원인과 영향인자에 관한 해석적 연구)

  • Shin, Chang-Hoon;Ahn, Seung-Hee;Chung, Jong-Tae;Her, Jae-Young;Kim, Woo-Sik
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.150-157
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    • 2005
  • Generally, the flow hunting is observed in almost all of the orifice meters but the intensity of the flow hunting is different at each metering system. So, we were getting some Questions as follows; why such a difference occurs and whether it influence to metering error rate or not. To investigate the flow hunting characteristics, we are trying to examine the flow characteristics around the orifice meter when the transient flow or pressure is generated at after the PCV(Pressure Control Valve) by 3D CFD method. And we have compared numerical results with experimental results at M - PCV station in order to clarify the relations with both the metering-pipeline diameter and flow rate. Finally, we can show some major factors influencing to the flow hunting and propose some correcting scheme of the flow hunting equation.

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Pressure Ripple Reduction of Hydraulic Pump-Motor in HST (HST용 유압폄프.모터의 압력맥동 저감 특성)

    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.04a
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    • pp.117-123
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    • 2003
  • This paper deals with pressure ripple and noise reduction characteristics for a hydrostatic transmission(HST) consisting of a variable axial piston pump connected in an open loop to a fixed displacement axial piston motor. Pressure ripples in HST is major source of vibration, which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube type hydraulic filter proposes to absorb pressure ripples with the high frequencies components to achieve better noise attenuation in HST. The basic principle tube is applied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimently confirmed that a hydraulic filter is absorbed to be about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and here, should provide a means of designing a quieter HST.

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Water-hammer in the Pump Pipeline System with and without an Air-Chamber (에어챔버 설치에 따른 펌프관로계의 수격현상)

  • Lee, Sun-Kon;Yang, Cheol-Soo
    • Journal of the Korean Society of Safety
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    • v.26 no.1
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    • pp.1-7
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    • 2011
  • When the pumps stopped in the operation by the power failure, the hydraulic transients take place in the sudden change of a velocity of pipe line. Each and every water hammer problem shows the critical stage to be greatly affected the facts of safety and reliability in case of power failure. The field tests of the water hammer executed at Cheong-Yang booster pump station having an air chamber. The effects were studied by both the practical experiments and the CFD(Computational Fluid Dynamics : Surge 2008). The result states that the system with water hammering protection equipment was much safer when power failure happens. The following data by a computational fluid dynamic analysis are to be shown below, securing the system stability and integrity. (1) With water hammering protection equipment. (1) Change of pressure : Up to 15.5kg/cm2 in contrary to estimating 16.88kg/cm2. (2) Change rate of water level : 52~33% in contrary to estimating 55~27%. (3) Note that the operational pressure of pump runs approx. 145 m, lowering 155 m of the regularity head of pump. (4) Note that the cycle of water hammering delays from 80 second to 100 second, together with easing the function of air value at the pneumatic lines. (2) Change of pressure without water hammering protection equipment : Approximate 22.86kg/cm2. The comprehensive result says that the computational fluid dynamics analysis would match well with the practical field-test. It was able to predict Max. or Min. water hammering time in a piping system. This study aims effectively to alleviate water hammering in a pipe line to be installed with air chamber at the pumping station and results in making the stability of pump system in the end.