The Finite Element Stduy Of Z-Shape And ?-shape Compensation Elbow With Large Diameter Of The Directly Buried Heating Pipeline

The central heating is necessary infrastructure of urban economic development and life,the directly buried installation is the main way of heating pipeline installation,the development of the directly buried installation is faster.Compensators are used in directly buried installation without compensation and directly buried installation with compensation,compensators can reduce the stress of the pipeline and the force acting on the fixed pier or valve parts.When compared to other compensators,the Z-shape and ?-shape compensation elbow have many advantages,such as simple manufacture,convenient installation,low initial cost,maintenance free,long service life,low heat loss and so on,the Z-shape and ?-shape compensation elbow should be preferable to use.In addition,Z-shape and ?-shape compensation elbow would be used in actual engineering of the directly buried heating pipeline,when the the tube position is changed,and the pipeline position is blocked.Technical specification for directly buried hot-water heating pipeline in city CJJ/T81-2013 has the following provisions:Z-shape compensation elbow's compensable arm length should be greater than or equal to 2 times of the elastic arm length,?-shape compensation elbow's compensable arm length should be greater than or equal to the elastic arm length.The elastic arm length is longer,up to 10 meter of Z-shape and ?-shape compensation elbow with large diameter,and pipeline changes is limited by planning route in practical engineering,So the provisions largely limits the use of Z-shape and ?-shape compensation elbow with large diameter.At present,the study on Z-shape and ?-shape compensation elbow with large diameter and short compensable arm is relatively rare,most of the studies only for Z-shape and ?-shape compensation elbow with small diameter and long compensable arm.the horizontally symmetrical Z-shape and?-shape compensation elbow with large diameter of the directly buried heating pipeline is simulated and analyzed by the finite element analysis software ANSYS,the compensable arm length of Z-shape and ?-shape compensation elbow is from two elbow directly connected to 2 times of the elastic arm length;the bend radius of curvature includes 1.5DN,3DN and 6DN;the pipe diameter is DN600?DN1200.In this paper,the main research contents and results are as follows:(1)The grid is encrypted and the soil spring exerting location is optimized by improving the previous Z-shape compensation elbow model,finally,the optimized Z-shape compensation elbow model is get in this paper by comparing the improved several models,the accuracy of the simulation is improved.(2)Analyzing the effect of the compensable arm length and the bend radius of curvature on the bend stress of Z-shape compensation elbow,under the same conditions,with the increasing of the compensable arm length,the bend stress of Z-shape compensation elbow decreases first and then increases,with the increasing of the bend radius of curvature,the bend stress's overall trend is reduced.(3)The maximum compensated arm length of Z-shape compensation elbow with various compensable arm can be directly used for directly buried heating pipeline engineering design,filling the blank in the discipline.(4)Analyzing the effect of the pipe diameter,the compensable arm length and the bend radius of curvature on the maximum compensated arm length of Z-shape compensation elbow,under the same conditions,with the increasing of the pipe diameter,the maximum compensated arm length of Z-shape compensation elbow increases,with the increasing of the compensable arm length,the maximum compensated arm length increases first and then decreases,the maximum compensated arm length is not always better with the increasing of the bend radius of curvature.(5)?-shape compensation elbow model is established based on the model of Z-shape compensation elbow model,Analyzing the effect of the compensable arm length and the bend radius of curvature on the bend stress of ?-shape compensation elbow,under the same conditions,with the increasing of the compensable arm length,the bend stress of ?-shape compensation elbow decreases first and then increases,with the increasing of the bend radius of curvature,the bend stress decreases.(6)The maximum compensated arm length of ?-shape compensation elbow with various compensable arm can be directly used for directly buried heating pipeline engineering design,filling the blank in the discipline.(7)Analyzing the effect of the pipe diameter,the compensable arm length and the bend radius of curvature on the maximum compensated arm length of?-shape compensation elbow,under the same conditions,with the increasing of the pipe diameter,the maximum compensated arm length of ?-shape compensation elbow increases,with the increasing of the compensable arm length,the maximum compensated arm length increases first and then decreases,the maximum compensated arm length is not always better with the increasing of the bend radius of curvature.(8)The engineering treatment methods are gived when Z-shape compensation elbow and ?-shape compensation elbow does not satisfy the bend strength calculation.