Long Pipelin Effect Of The Shield Machine Based On Fluid-Structure Interaction

Abstract:Fluid pipe is one of the most important components of hydraulic system which works as to carry material flow, energy flow and information flow. The design of the pipeline system, to some extent, affects the function of the hydraulic control system.As for the hydraulic system of the shield tunneling machine, the change of sudden load or operating conditions can cause mutation in the fluid state of the system, resulting in fluid pressure pulsation which induces pipe vi-bration by the fluid-structure interaction, generates noise pollution, and even leads to pipeline damage or failure of the machine. The complex fluid-structure interaction effect is one of the most important factors which de-termine the dynamic characteristics of the hydraulic piping system. More-over, taking into account the long length pipeline, high oil-pressure and rapid mutation of work conditions and load, coupling effect is very com-plicated in the hydraulic system of the shield tunneling machine. With re-gard to the complex fluid-structure interaction, the conventional dynamic performance analysis of hydraulic pipeline system analysis is insufficient. In a word, the pipeline dynamic characteristics forecasted by the traditional methods have much error, especially when the pipeline is long and weakly constrained. It makes the safety of piping system greatly reduced which is designed according to the traditional method. To get excellent power trans-mission performance, in-depth study of long pipeline effect of the shield machine based on fluid-structure interaction is very necessary.With length of pipeline could be up to100meters, fluid-structure inter-action effect is very prominent in the long pipeline hydraulic system of shield machine. The formation of long pipeline effect of the shield machine is the comprehensive result of the oil strike, the pressure loss or energy loss along long pipeline, the pipeline vibration induced by fluid-structure inter-action. It is clear the fluid and the pipe cannot work individually regarding the three components of long pipeline effect. Long pipeline FSI effects se-riously affect flow characteristics of pipeline and control characteristics of hydraulic system, and fluid-structure interaction is one of the basic ele- ments which must be included in to inhibit fluid oscillations and pipe vi-bration, so the study of vibration of the fluid-structure interaction is the key to the design and operational control of such pipeline system. Around this core, this dissertation carried out the following studies and made some rel-evant new knowledge:1. Study of Dynamic Response Characteristics of the Long Pipeline Hydraulic Control System. The pipeline of shield hydraulic system is long, and it causes the high loss of pressure and energy, even causes re-sponse lag. To improve the speed of response, this dissertation proposed the modeling method of the impact of factors on the dynamic performance of shield hydraulic control system in which long pipe interaction effect was considered and conducted simulation respectively from the perspective of the pipeline structure parameters and the accumulator, then influence law of the two on hydraulic system was pointed out; furthermore, the quantita-tive relationship was obtained by the corresponding experimental study. On the condition of minimal loss of pipeline pressure, this dissertation opti-mized the pipeline structure design. In this way the parametric space of pipeline structure based on pressure loss was established.2. Study of Vibration Characteristics resulted from Fluid-Struc-ture Interaction Effect in Long Hydraulic Pipeline. A single span pipe-line transfer matrix was established according to the wave theory. For the characteristics of long length and multi-span attached to the hydraulic pipe-line of shield machine, multi-span pipeline field transfer matrix was finally derived from displacement boundary conditions, fluctuation transmission theory and continuity theory of fluid. Accordingly, the field transfer matrix of any cross could be recursive. Based on this understanding, a recursive method was put forward to model fluid-structure interaction in long multi-span pipeline. The method could quickly deduce the field transfer matrix of any cross, which would provide a good theoretical basis and methods for the analysis of complex multi-span pipeline system. A long pipe vibra-tion criterion was established. Based on avoiding the fluid-structure inter-action resonance, a calculation method of counts of clamped support and following optimization model were provided with which the shortage of selecting counts of clamped support based on experience in the past has been overcome.3. Design and Construction of Hydraulic Experimental Table of Long Pipeline. A dedicated research experimental table was independently designed and developed. The main functions of the table are as follows:to simulate the hydraulic behavior of shield propulsion system; to calibrate and correct the mathematical model related to fluid-structure interaction effect in long pipeline hydraulic system; to study the dynamic and static characteristics of valve control system with long pipe under the condition of different length of pipe, different constraints situation, different external load, non-steady-state operation. In order to achieve a variety of functions, hydraulic integration design proposed and implemented a number of dis-tinctive technology modules:paired cylinders device were designed to act as power and load respectively, with which large load could be applied in experiments; serpentine arrangement, movable columns and detachable support applied to the design of long multi-span pipeline system facilitate the layout of long pipeline in limited space and improve the flexibility of changing the structural parameters of pipeline; control system was devel-oped by the concept of modularization and parameterization, so that the experiment could be completed automatically according to preset programs; By configuring reasonable sensors, data acquisition system, and vibration analysis system, a test method and apparatus was invented to study vibra-tion effects in hydraulic system with long pipeline4. Experimental Study of Vibration in Hydraulic System with Long Pipeline. Modal analysis, operating deflection test and excitation source frequency characteristic test were carried out on the hydraulic experi-mental table with long pipeline. The tests showed:firstly, the natural fre-quency of the hydraulic long-straight pipeline was densely distributed mainly in the low frequency; secondly, pipeline span regularly affected the modal parameters. With the span increased, beam model features of pipe-line became obvious and the natural frequencies of pipeline were reduced which made it easy to resonance with the external excitation for pipeline under the dynamic load; in addition, pipeline span could be reduced and the natural frequencies of pipeline could be significantly increased by in- creasing the number of supports, but this would make the regularity of vi-bration mode change hard to be discovered which was not conducive for vibration suppression.The innovation of this dissertation is summarized as follows:1. Aiming at the features of valve control hydraulic system of shield machine:long pipeline, sophisticated response of hydraulic system and ob-vious response lag, this dissertation studied the influence law of the pipe-line structural parameters and accumulator on response lag by the ways of simulation and experiment, and proposed a Energy saving optimization method with the objective of minimizing pressure loss.2. Based on the established transfer matrix model of fluid structure in-teraction effect in conveying fluid pipes simply supported, a recursive transfer matrix modeling method for multi-span conveying fluid pipes and a long pipe vibration criteria were proposed. Furthermore, a calculation model of counts of clamped support was formed. Combining with simula-tion analysis, this dissertation tried to conclude some basic theories and principles for optimizing the counts of clamped support.3. The innovation of experimental table could be reflected in:a) the design of a large thrust device consisting of two opposite oil cylinders which could simulate70tons of power and a variety of load (mutation load, program-controlled load and inertia load); b) the development of the test sets which would be competent for vibration effect test of the visual reality complex piping system composed of multi-combination pipes.The above research results provided some basic theories, key technol-ogy and experimental platform support for study on the characteristics of long hydraulic pipeline included in fluid structure interaction effect and optimization of structure parameters of pipeline system.