The Transient Characteristics of Fluid Pipes including Mechanical Load : 2nd Report, Theoretical Analysis on Effects of Valve Closure

Abstract

This paper presents a theoretical study of the transient characteristics for a system consisting of hydraulic actuator, fluid pipe and operation valve. In this analysis fluid motion in pipe is treated as a two-dimensional unsteady laminar flow, and non-linear characteristics of the flow through a valve is considered exactly. The solution for pressure variations at arbitrary pipe section and actuator displacement are obtained in terms of convolution integral and their numerical results are presented. The effects of system parameters and operating parameters, especially, valve orifice shape, valve movement (e.g., instantaneous closure, partial closure, gradual closure, exponential gradual closure, etc.) on the transient response of the system are discussed. Two approximate solutions, one obtained by treating a fluid in pipe as a one-dimensional steady laminar flow, and the other obtained by considering only the compressibility of the fluid in pie are also presented and compared with an exact solution.