Pipeline Flow Analysis And Structure Optimization Based On Flow Field Synergy Principle

The phenomenon of fluid flow in pipes is widely existing in industry and daily life.Due to the unreasonable design of the tube structure and the viscous dissipation characteristics of the fluid,the energy consumption and waste in the fluid flow process are unavoidable.Therefore,the research on the optimization of the pipe flow field is an important task to solve the energy shortage problem.At present,most of the optimization cases of the pipeline structure are based on engineering experience,or comparison with experiments,lack of theoretical guidance.To solve this problem in this thesis,the field synergy principle combined with minimum mechanical energy dissipation principle are used to analyze the fluid flow in the pipeline,the mechanism of flow resistance variation in the pipeline is revealed from the aspect of local field synergy,and the ideas of theoretical guidance to optimize the pipeline structure and specific optimization schemes are achieved in consideration of the overall structure of case,which verified and applied further in the actual project cases.In the first part of the thesis,the mathematical theories of field synergy applied to heat transfer and flow field are deduced respectively.By volume integration for the turbulent flow governing equations of the whole basin,the turbulent flow field synergy equation is rederived,considering that the effective viscosity coefficient μeff is related to the coordinates.Compared to the synergy principle of laminar flow,it is found that the flow resistance in turbulent flow is not only related to the field synergy number FSm,but also related to the effective viscosity coefficient μeff.Based on the irreversibility of flow process and the principle of minimum mechanical energy dissipation,the field synergy equation of turbulent flow is further deduced,which lays a theoretical foundation for guiding pipeline structure optimization.The second part of the thesis verifies the reliability and validity of using the field synergy principle of turbulent flow in simple pipeline structure optimization.Taking a parallel flow pipeline for example,the pipeline structure was optimized,and concrete methods using field synergy principle as the theoretical guidance are proposed.The streamline obtained by the field synergy equation is the optimal result,which the internal structure of pipeline need to be changed to fit,so that the flow drag can be reduced;the structure to be optimized can be found and located according to the distribution map of the field synergy angle cosine square mean.The third part of the thesis studies the structure optimization of complex single pipe.Taking the internal structure of axial flow check valve as an example,a comparative study of the flow field before and after optimization is made,which further deepens the understanding of the physical meaning of the flow field synergy.It is found that the pressure drop of the valve before and after the optimization is 5857.1 Pa and 1024.6 Pa respectively.The flow resistance and energy consumption of the optimized valve are greatly reduced In addition,it is also suggested that the turbulent viscosity coefficient can be used as a standard to evaluate the synergy degree of the flow field.The flow resistance can be effectively reduced by decreasing the mean value of the turbulent viscosity coefficient or increasing the turbulent viscosity coefficient gradient.The fourth part of the thesis applies the flow field synergy principle to the multi-pipe system,taking the primary air pipe system of the boiler power plant as an example.From the overall view of the field synergy degree,the position of pipeline to be optimized is determined,and the structure is improved.By comparing the inlet and outlet pressure of primary air duct system,it was shown that in 50%and 100%load conditions,the pressure drop of other parts of pipeline except air preheater reduced at 10.937%and 16.957%respectively,which reaches an obvious optimization effect.