Research On Analytical Analysis And Optimization Method Of Velocity Distribution Of Complex Porous Fibrous Carrier

The catalyst support of methanol steam reforming(MSR)micro-reactor is a critical component affecting the hydrogen production performance,so different types of catalyst support and corresponding structure optimization methods have been continually emerging,among them,porous copper fiber sintered felt(PCFSF)demonstrate a series of properties that are highly expected for MSR hydrogen production.In recent years,the PCFSF with gradient porosities structure has been prepared,and better performance of hydrogen production based on MSR was observed.However,as for carrier consist of complex random fiber(fiber carrier),there is a lack of approach to optimize their gradient porosities structure due to their random fiber structure.Furthermore,the analytical optimization method widely used in other types of carrier is difficult to apply to the fiber carrier,causing no quantifiable criterion has been developed to guide the optimization of the gradient porosities of PCFSFs.In this thesis,an analytical model of the velocity distribution of fiber carrier is established.By analyzing the influence of the structural characteristics of fiber carrier on the velocity distribution,the evaluation index of the uniformity of the velocity distribution of fiber carrier is preliminarily formed,and then an analytical optimization method of the velocity field of fiber carrier is proposed.The main work of this thesis includes:(1)An equivalent resistance network model for the velocity distribution of fiber carriers with uniform porosities structure is established.The channel model of fiber carrier is constructed by simplifying the complex random fiber distribution structure,and the equivalent resistance network model is established through the mass transfer characteristics in the channel model.The analysis and verification results of Computational Fluid Dynamics(CFD)show that the equivalent resistance network model can quickly and accurately reduce the flow distribution characteristics of the fiber carrier.(2)An equivalent resistance network model for the velocity distribution of fiber carriers with different gradient porosities structure(gradient porosities fiber carrier)is established.The equivalent resistance network model of the gradient porosities fiber carrier is constructed by coupling the channel models on both sides of the porosity interface with different shapes of the fiber carrier and considering the accuracy of the solution.The verification results of CFD show that the equivalent resistance network model of the flow distribution of the gradient porosities fiber carrier can be used to quickly solve any gradient porosities structure fiber carrier with constant calculation amount,and the velocity field distribution of the vector is more consistent.(3)The comprehensive evaluation method of velocity distribution uniformity of fiber carrier is analyzed and formed.According to the uniformity of flow distribution and the peak value of flow velocity,the evaluation method of flow distribution is established,the flow resistance and contact area of fiber carrier are quantified,on this basis,the preliminary comprehensive evaluation method for the velocity distribution is established to preliminarily evaluate the uniformity of velocity distribution of gradient porosities fiber carrier which is compared with the hydrogen production experiment.(4)The structure optimization design method of fiber carrier is established.According to the comprehensive evaluation method of fiber carrier,the optimal gradient porosities structure of fiber carrier is solved through genetic algorithm.The optimized fiber carrier is compared with the existing fiber carrier to analyze the influence of gradient porosity structure on the structure parameters.Finally,a relatively complete analytical optimization method of fiber carrier is formed.