| Porous media as a class of important pneumatic components,in many industrial fields have a wide range of applications.Due to the existence of numerous micro-pores inside the porous media,which makes the fluid flow through,will produce a certain pressure drop at both ends of the porous media.The relationship between pressure drop and flow rate(i.e.,flow characteristics)is the basic characteristics of porous media as pneumatic components,only a quick and accurate description of this relationship,in order to better porous media in different industrial applications,improve production efficiency and reduce energy consumption.In order to fully study the flow characteristics of porous media and the factors affecting them,this thesis utilizes a combination of numerical simulation,theoretical analysis,mathematical model construction and experimental analysis,and its main research contents are as follows:(1)The flow principle of porous media is introduced by CFD numerical simulation method and the trend of the flow characteristic curve of porous media under positive and negative pressure conditions is analyzed.The influence of porous media geometry size and porosity on its flow characteristic is further studied by changing the size and porosity of porous media.(2)By analyzing the size,porosity and internal flow law of porous media,a flow characteristic model based on Darcy-Forchheimer law is constructed;36 different sizes of sintered metal porous media are designed and flow test experiments under positive and negative pressure conditions are conducted,and finally the flow characteristic model parameters under two pressure conditions(permeability coefficient and inertia coefficient)based on the experimental results.(3)The identification method of the flow characteristics model parameters under positive and negative pressure conditions is proposed.And on the basis of the characterization accuracy of the method,the effects of temperature,wall effect,gas compressibility and dynamic response factors on the flow characteristics of porous media are analyzed.In particular,the effects of constant power heating,different heating powers and different pressures under constant power conditions on the flow characteristics of porous media are analyzed in terms of temperature effects.(4)For the shortcomings of the steady-state flow test method in terms of energy consumption and time,a flow test method combining one large and one small fixed volume chamber is proposed.Firstly,the feasibility of the test method is verified,secondly,the parameters of the flow characteristics model are identified using the test method and GaussNewton iterative algorithm,and finally,the volume of the fixed volume chamber is changed and the degree of accuracy of the test method in obtaining flow is evaluated by studying different volumes. |
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