학술논문
다중관망 내에서 밸브의 급폐쇄에 따른 수격현상에 관한 수치적 연구 / A Numerical Study on Water Hammer due to Rapid Closing of Valves in a Multi-pipe Network
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
정수장에서 생산된 용수를 송수펌프와 송수관로를 통하여 배수지로 공급할 경우 장거리 송수관로에서 발생하는 수격현상은 중요한 문제로 대두된다. 수격(Water Hammer)현상이란 유체가 이동 중에 급격한 유속변화가 생길 때 발생하며 이때 유체의 운동에너지는 압력에너지로 변화되고 큰 압력이 발생되어 관로를 확장시키려고 한다. 관로 내에서 수격현상은 압력이 일정한 값으로 유지될 때까지 왕복을 하며, 이 과정에서 소음 및 배관의 파손 등으로 이어져 배관시스템을 위험한 상황에 놓이게 한다. 본 연구에서는 다중관망에서 발생할 수 있는 수격현상에 대한 압력변화 양상을 수치적 방법을 이용하여 비교 분석하였다. 본 연구에서는 밸브 급폐쇄에 따른 수격작용현상을 분석하기 위해 Joukowsky's 이론식과 초기 입구의 압력 변화(1bar, 3bar, 5bar, 7bar)와 유속변화(0.5m/s, 1.0m/s, 1.5m/s, 2.0m/s, 2.5m/s, 3.0m/s, 3.5m/s)를 통하여 시간 변화에 따른 압력변화의 양상과 전파속도를 비교하여 본 연구에 사용되어진 유동해석 수치모형의 타당성을 확인하였다. 또한 다중 관망에서 파이프 직관 끝에 설치된 밸브의 급폐쇄에 의한 밸브의 작동 조건에 따른 수격현상에 대해 모의 및 분석을 수행하였다. 다중관망 내 밸브의 개폐조건에 따라 총 6개의 시나리오를 조건으로 하였으며, 입구의 압력 1bar, 유속 1m/s, 유량 7.83kg/s등을 초기조건으로 하여 수치모의 하였다. 대체로 밸브 Middle, Lower에서 최대 압력 값이 발생하였다. 급폐쇄가 일어나는 밸브를 제외한 나머지 밸브에서는 일정한 유량이 유출 될 경우, 유량이 유출되지 않을 때보다 최대 압력 값이 약 두배로 발생되었다.
In the case of the supply water produced in a water treatment plant to a water reservoir through a water supply pump and water supply pipeline, phenomenon the water hammer occurring in the long-distance water supply pipeline becomes an important issue. The phenomenon of water hammer occurs when the velocity of a moving fluid changes sharply while the fluid moves. And at that time, the kinetic energy of fluid converts into pressure energy. And high pressure occurs. So, it will expand the pipeline. The water hammer phenomenon repeats inside the pipeline until pressure is kept at a constant value. This process leads to noise, pipe damage, and so on. Consequently, the pipe system will be put in a dangerous situation. This study analyzed the patterns of change in pressure for water hammer phenomenon that might occur in the multiple pipe by using a numerical method. In this study, in order to analyze the water hammer phenomenon according to the sudden closure of valve, in the multiple pipe system the validity of numerical model for fluid analysis was verified by comparing the pattern of change in pressure and propagation speed over time through Joukowsky's theoretical formula, a change in pressure at the inlet in the early stages (1bar, 3bar, 5bar, 7bar), and a change in the velocity of a fluid (0.5m/s, 1.0m/s, 1.5m/s, 2.0m/s, 2.5m/s, 3.0m/s, 3.5m/s). Moreover, this study was simulated and analyzed the water hammer phenomenon according to the operation condition of valve due to the sudden closure of valve installed at the end of straight pipe in the multiple pipe systems. A total of 6 scenarios according to the closure condition of valve inside the multiple pipe systems were considered. And the inlet pressure of 1bar, fluid velocity of 1m/s, the flow rate of 7.83kg/s, were considered to be initial conditions. In general, the maximum pressure occurred at valve middle and lower. In the rest of valves except the suddenly closed valve, in the case of flowing out at a certain flow rate, the maximum pressure occurred, which was approximately two time higher than in the case of flowing in.
In the case of the supply water produced in a water treatment plant to a water reservoir through a water supply pump and water supply pipeline, phenomenon the water hammer occurring in the long-distance water supply pipeline becomes an important issue. The phenomenon of water hammer occurs when the velocity of a moving fluid changes sharply while the fluid moves. And at that time, the kinetic energy of fluid converts into pressure energy. And high pressure occurs. So, it will expand the pipeline. The water hammer phenomenon repeats inside the pipeline until pressure is kept at a constant value. This process leads to noise, pipe damage, and so on. Consequently, the pipe system will be put in a dangerous situation. This study analyzed the patterns of change in pressure for water hammer phenomenon that might occur in the multiple pipe by using a numerical method. In this study, in order to analyze the water hammer phenomenon according to the sudden closure of valve, in the multiple pipe system the validity of numerical model for fluid analysis was verified by comparing the pattern of change in pressure and propagation speed over time through Joukowsky's theoretical formula, a change in pressure at the inlet in the early stages (1bar, 3bar, 5bar, 7bar), and a change in the velocity of a fluid (0.5m/s, 1.0m/s, 1.5m/s, 2.0m/s, 2.5m/s, 3.0m/s, 3.5m/s). Moreover, this study was simulated and analyzed the water hammer phenomenon according to the operation condition of valve due to the sudden closure of valve installed at the end of straight pipe in the multiple pipe systems. A total of 6 scenarios according to the closure condition of valve inside the multiple pipe systems were considered. And the inlet pressure of 1bar, fluid velocity of 1m/s, the flow rate of 7.83kg/s, were considered to be initial conditions. In general, the maximum pressure occurred at valve middle and lower. In the rest of valves except the suddenly closed valve, in the case of flowing out at a certain flow rate, the maximum pressure occurred, which was approximately two time higher than in the case of flowing in.