Research On Curved Pipe Of Dircetly Buried Hot-water Heating Pipeline With Large Diameter

During the "period of the twelfth-five-year plan'',people's living standards rise steadily,and happiness index increase high.The requirements for living environment is more stringent,so that district heating has become a city's municipal construction indispensable part.Respect to district heating for the city,use hot-water heating has many advantages,such as fuel economy,convenient maintenance,wide heating service range and the indoor temperature stable.Therefore,the main way of heating is hot-water heating in present stage.For district heating hot-water pipeline laying engineering,buried with low capital investment,low heat loss along the way,corrosion insulation performance,small footprint,fast construction and other characteristics,is rapidly becoming a mainstream laying way.When laying directly buried hot-water heating pipeline,it will encounter obstacles inevitably,so it is necessary to use curved pipe.Different rotation angle curved pipe stress situation is different.When the rotation angle range of 80 °-120 °,the curved pipe has a good ability to compensate,and corresponding engineering approach is very mature.However,curved pipe's stress distribution for other angles has a smattering of understanding.In order to ensure the reliability of Pipeline operation,anchor blocks or compensation will be used,then it increases the construction costs of pipeline and the system's danger point.the paper against curved pipe of directly buried hot-water heating pipeline with large diameter completed the following work:Chapter one introduces the background and significance of this thesis.Summarized different rotation angle curved pipe for a variety of research results and major practice,indicating the main research methods and main content.Chapter tow stress Analysis of directly buried hot-water heating pipeline,and explain pressure load,displacement load and pressure-displacement load characteristics,provide a theoretical basis for the finite element analysis.Failure mode of the pipeline into the following categories:plastic deformation,fatigue failure and loss of stability.Chapter three analysis of the various sectors curved pipe stress calculation method,concluded that stress analysis of curved pipe main considerate the loop stress affect,while ignoring the axial stress.When the compensation effect of the curved pipe is well,this method has a high accuracy;When the compensation effect of the curved pipe is poor,this method has low accuracy;When the rotation angle is very small,this method is wrong.Then,Cite several processing method of curved pipe and explain their characteristics.Finally,analysis of the curved pipe defects,and preventive measures.Chapter four briefly introduces the method of using finite element analysis software and the unit employed in this article.Firstly make modeling and mesh of directly buried heating curved pipe.Secondly test the independence of mesh.Then exert pressure load and temperature load on the model and define the boundary conditions.Lastly make calculation of the finite element model to get the results.From the results we can see that,though both sides of the straight arms in different length combinations,as long as the sum of the two calculation arm length be the same,the maximum stress value of the curved pipe will not change.The stress cloud shows that,during the gradually increasing of the corner angle,the maximum stress area on the curved pipe moves from the inside surface of the inner arc to the stress neutral plane.Chapter five makes analysis of the engineering cases,which applied two kinds of angular at the same time.What's more,it analyzes the same rotation and the reverse rotation to determine the appropriate radius of curvature of the project.Chapter six summarizes the conclusions and results of this paper,and makes vision and recommendations to the unfinished place of directly buried heating curved pipe.