Study On Structure And Characteristics Of Thermoelectric Power Generation System Based On Porous Media Burner

Energy and environmental issues have gradually become important factors restricting China’s social and economic development.Making full and efficient use of unconventional energy such as low calorific value gas can not only effectively alleviate the problem of energy shortage,but also help to curb the emission of greenhouse gases such as methane.The inherent characteristics of low calorific value gas,such as low calorific value,wide dispersion,and changeable properties,bring great obstacles to its large-scale collection and application.It is urgent to develop high-efficiency energy conversion technology for low calorific value gas.In this thesis,the mechanism and method of stable and efficient combustion of low calorific value fuel with porous media burner are studied by means of numerical simulation and experiment.Based on the analysis of the dynamic characteristics of equipment and system,the structure of thermoelectric power generation system based on porous media burner is proposed.The main work and achievements of this thesis are as follows:First,to obtain the high-precision dynamic and static characteristics of thermoelectric power generation system and analyze the detailed combustion process of fuel in porous media,a three-dimensional transient solver TEGFoam for the whole working condition of thermoelectric power generation(TEG)process and a transient and heterogeneous solver Porous Combustion Foam for porous media combustion(PMC)are constructed respectively.Based on the Open FOAM fluid-solid heat exchanger solver cht Multi Region Foam,TEGFoam adds combustion dynamics model and TEG dynamic characteristic model and realizes the collaborative simulation of reaction flow and TEG through the coupling of reaction flow source term and TEG thermal effect source terms.The availability and accuracy of the solver are fully verified by the experimental results of module static power generation and flue gas heat recovery TEG system.Based on the fluid-solid heat exchanger solver coupled with rho Combustion Model,Porous Combustion Foam constructs the volume average model of PMC.By extending the single parameter model to the field model and modifying the mesh interface flux(phi)by using the minimum neighbouring mesh porosity coefficient,the heterogeneous simulation of PMC process is realized.The accuracy of the solver is fully verified by the comparison with the existing simulation results of segmented porous media combustion.The three-dimensional transient solver TEGFoam provides a powerful analysis tool for the design and regulation analysis of TEG system,and the three-dimensional heterogeneous transient solver Porous Combustion Foam provides a powerful analysis tool for PMC burner design,fault analysis and operation regulation.Then,to find a stable and efficient PMC burner and TEG structure,the threedimensional dynamic characteristics are analyzed based on typical PMC and TEG objects,and the key factors affecting the performance of the equipment are identified.Aiming at the problem that PMC burner is prone to combustion instability,the process of burner flame inclination is analyzed by using the developed Porous Combustion Foam.The calculation results show that the skeleton blocking defect in the burner is an important inducement for the instability of PMC process.Based on the Porous Combustion Foam solver,based on introducing the automatic generation algorithm of porous media skeleton,the pore level micro simulation of PMC process is carried out with the help of supercomputer Archer2.The calculation results show that the local blockage of porous media will not only lead to the distortion of flame surface,but also produce local high temperature zone and further lead to the melting of materials.Based on the TEGFoam,the full three-dimensional simulation of the key components of the TEG system is carried out,and the hot side etched fin structure is optimized.Finally,to improve the power generation efficiency of TEG system,a heat source cascaded TEG system(CTEG)coupled with PMC burner is designed and constructed.Based on the idea of hierarchical utilization of heat sources,a new structure of TEG system is proposed.Based on optimizing the structure of burners,heat exchangers and other equipment,the CTEG experimental system is constructed.The experimental results show that compared with the single-stage TEG system,the power generation efficiency of CTEG is improved by 21.56% to about 5.92%.Based on the heat transfer parameter identification model and dynamic analysis model,the dynamic and static characteristics of TEG system are analyzed.The results show that the heat transfer resistance at the cold side is an important bottleneck restricting the power generation performance,and the low-temperature power generation stage has little impact on the power generation efficiency of the whole system.To simplify the system structure and improve the anti-interference ability of the system,an improved CTEG system based on Si C foam PMC burner is designed and constructed.The experimental results show that the system has better fuel adaptability and larger disturbance on the fuel side under the premise of small increase in efficiency.To sum up,the open-source solvers TEGFoam and Porous Combustion Foam constructed in this thesis provide effective analysis tools for CTEG system structure and operation optimization;The obtained dynamic characteristics and instability mechanism of PMC burner provide theoretical and technical support for burner design and regulation;The proposed CTEG system based on PMC burner provides a new idea for the efficient and clean utilization of low calorific value gas.