Research On Flow Characteristics Of Perforated Pipe Along The Pipeline Under Gravity

The perforated pipe is a device for distributing fluid in a main pipeline,it is widely used in various industries.The uniformity of perforated pipe is one of the important indicators for evaluating the system's fineness.The pressure distribution along the perforated pipe is one of the research contents of the perforated pipe outflow characteristics.It directly affects the uniformity of the perforated pipe.In this paper,the pressure distribution of the perforated pipe with slope gradient was studied.At the same time,the changes of the pressure curve of the perforated pipe were analyzed based on the previous research results.From the flow deviation rate,the variation of the maximum laying length and the optimal laying slope of the perforated pipe was studied.The results of flow and pressure changes in perforated pipes were simulated by computer software.The main results as follows:(1)The pressure head formula of perforated pipe with slope was established based on the energy equation.For the perforated pipe that can be ignore the flow velocity head,the pressure head formula of the perforated pipe was deduced,and the variation of the pressure head curve was analyzed.Combining the experimental data of three kinds of perforated pipes with different length-to-diameter ratios,the pressure head curve can be roughly divided into three types.The first type:the monotonic decreasing curve,the maximum value of the pressure head of the perforated pipe was at the head of the pipeline,and the minimum pressure head was at the end of the pipeline.The second type:the monotonic increasing curve,the maximum value of the pressure head of the perforated pipe was at the end of the pipeline,and the minimum pressure head was at the head of pipeline.The third type:the concave curve,the pressure head curve drops first and then rises,the minimum pressure head was located in the middle of the pipeline,and the maximum pressure head was located at the end or the head of the pipeline.(2)By analyzing the positions of the maximum pressure head and the minimum pressure head,the pressure curves of the perforated pipe were classified into five types.Type ? curve:??0,I L[H f? 0,the pressure head decreases along the length of the perforated pipe,the value of pressure head at the tail end is the lowest,and the value of pressure head at the first outlet is the greatest.Type ?-a curve:I>0,0<I L/Hf<1,the value of pressure head at the tail-end outlet is less than the value of pressure head at the first outlet,and pressure head first decreases and then increases to a small extent along the length of the perforated pipe.Type ?-b curve:I>0,I L/Hf=1,the value of pressure head at the tail-end outlet equals the value of pressure head at the first outlet,both of which are the maximum pressure head,and pressure head first decreases and then increases along the length of the perforated pipe.Type ?-c curve:I>0,1<I L/Hf f<(m·z +1),pressure head first decreases to a small extent and then increases to a large extent along the length of the perforated pipe,and the value of pressure head at the tail-end outlet is the greatest.Type ? curve:I>0,I L/Hf>(m· z+1),pressure head increases along the length of the perforated pipe,and the value of pressure head at the tail end is the greatest.(3)By studying the flow rate deviation and working head deviation rate,the maximum laying length and the optimal laying slope of the perforated pipe were analyzed.The influence of laying slope,pressure head and orifice spacing on laying length and laying slope were analyzed,which can be used for the design of perforated pipe system.(4)The pressure field and flow field of the perforated pipe were simulated by Fluent software,and the pressure variation and flow field variation of the perforated pipe were analyzed.Compared with the previous theoretical analysis and experimental results,the results were consistent and reasonable.