Matching Method And Integration Design Research On Thermoelectric Generator System For Engine Exhaust Waste Heat Recovery

As one of the major sources of petroleum consumption and environmental pollution,energy saving of internal combustion engines(ICEs)is of great significance to energy security and environmental protection.Among various engine energy-saving technologies,waste heat recovery(WHR)has the greatest potential.Thermoelectric generators(TEGs),which can convert thermal energy into electric power directly,have many advantages like simple structure,stable operation,high reliability and so on.As a result,TEGs have broad development and application prospects in engine exhaust waste heat recovery.This paper conducted theoretical and experimental studies of exhaust-based TEG system based on the matching method of thermoelectric modules(TEMs)with large temperature gradient exhaust gas and integration design of TEG system,aiming at developing high-efficiency power output system with lightweight structure and high integration.Based on the characteristics of thermoelectric material physical parameters,this paper proposed stepped structure of TEM to match the large temperature gradient waste heat in radial direction.The strengths of each thermoelectric material appropriate for different temperature ranges can be leveraged to the full extent.The effects of structural parameters and boundary conditions of cold and heat source on the stepped TEM output performance under isometric and non-isometric length ratio of p-n type semiconductor are investigated.Optimal length ratio are determined to evaluate the performance promotion potential.The output properties of stepped thermoelectric modules are measured based on the performance test platform.Results show that stepped structure matches the large temperature gradient waste heat in radial direction effectively.Based on the stepped structure of TEM,a matching method of large temperature gradient waste heat in axial-radial direction is proposed.Thermoelectric materials will recovery the multi-gradient and multidimensional exhaust energy more efficiently by composite layout form of stepped-single TEMs.The effects of heat collection and non-isometric length ratio of p-n type semiconductor on the output power of TEG system and optimal layout form of TEMs are investigated to further optimize the overall performance.Results indicate that compared with single form,TEG system with composite TEM layout performs better and achieves higher power output.Heat collection and dissipation coupling design research is conducted based on the technical requirements of light weight and efficient power output of TEG system.The performance improvement potential is investigated by collaborative design and optimization of heat exchanger and heat sink structure.The components structures are determined combined with the flow characteristics of heat and cold source using traditional design method.The effects of fins height,length ratio and engine conditions on the performance of TEG system are investigated by the area ratio of heat collection and dissipation adopting coupling design method.The optimal structure of TEG system is obtained under the restricted conditions of weight and dimension.Design results indicate that heat collection and dissipation coupling design improves the maximum output power of TEG system by 23.1%.Besides,the corresponding system meets the requirements of light weight,which indicates great power promotion potential.Based on the heat collection and dissipation coupling design method,a TEG system with the optimal area ratio of 0.48 combined with test conditions is proposed and the corresponding prototype is developed.The effects of cold and heat source boundary conditions on thermodynamic properties and electrical parameters are measured by test platform to evaluate the overall performance of the TEG system.The optimal operation conditions of selected TEMs are tested based on simulation results to improve the thermoelectric conversion efficiency.Results show that the output performance of TEG system improves distinctly with higher heat source flux and cold source velocity,which is more significant with higher heat source temperature.The maximum output power of TEG system is 16.4 W under test conditions.An integration design of thermoelectric generator is put forward based on the fundamental principles and structure features of engine muffler to replace the original muffler in exhaust system,which aims at improving the compatibility and integration.Based on the three-dimensional integrated acoustic thermoelectric generator system model,the effects of porous position,perforation rate and vacuum structure on the output and acoustic performance of TEG system are discussed to determine the optimal integration design.Novel heat transfer structure is proposed to improve the flow characteristics according to the uneven heat transfer and poor acoustic behavior of the integrated system above.The excellent characteristics of high thermal conductivity and noise elimination of porous material are conductive to higher output power and transmission loss,which contributes to highly integrated acoustic TEG system.