Study On Micro Combustion Thermoelectric Power Generation System With Heat-Recirculation

Micro combustion thermoelectric power generation system is a device which is based on Seebeck effect of thermoelectric material to transform thermal energy released in the micro combustor into electricity directly. Because of some merits such as simple structure, flexible arrangement, no moving parts, micro combustion thermoelectric power generation system is much easier to be applied in the micro aerial vehicle, portable electronic devices and other equipments of military and civil domain. Based on heat-recirculation technology and heat-recirculation via thermoelectric modules, a micro combustion thermoelectric power generation system is designed and some research work on combustion characteristics and thermoelectric characteristics of the system is done through numerical simulation and experimental methods in the present dissertation.The numerical simulation of the designed micro combustor is investigated with CFD. The results show that because of the structure of regenerative combustion, the micro combustor can realize high efficient combustion in a wider operating range, combustion efficiency remains above0.94, and heat loss ratio is very low. The micro combustor with heat-recirculation via thermoelectric modules can realize stable and efficient combustion, and the heat loss is reduced as much as possible. More importantly, the micro combustor can be used as a heat source of intermediate and low temperature thermoelectric modules, especially when the excess air ratio is greater than8, the temperature and temperature uniformity of the thin brass slice is below600K and40K, respectively, and it is able to ensure the safe and efficient operation of low temperature thermoelectric modules.The numerical simulation of the designed thermoelectric power generation system is investigated and the effects of excess air ratio, combustion power, width d of the air-shunted slit on combustion efficiency, heat loss and temperature field are studied. The study results show that when the air excess ratio is from8to12and the width d of the air-shunted slit is0.5mm, combustion efficiency of the system is relatively high and hence the width of0.5mm is an optimal design of the air-shunted slit. With the increase of air excess ratio, the mean temperature difference between hot and cold side of thermoelectric modules decreases. When the air excess ratio is greater than8.5, which can keep thermoelectric modules safe, the maximum mean temperature difference between hot and cold side of thermoelectric modules is62K. In addition, the analysis result indicates greater heat loss of the side wall of combustor and heat transfer resistance in the flue gas channel influence the mean temperature difference between hot and cold side of thermoelectric modules. On this basis, the effects of wall materials and enhancement of heat transfer in the flue gas channel on system performance are studied by utilizing numerical simulation method. The research results show that after the side wall and posterior diaphragm use quartz material, the heat loss of the system reduced and the mean temperature difference between the hot and cold side of thermoelectric modules increases. When the air excess ratio for the safe operation is greater than7.8and the maximum mean temperature difference between hot and cold side of thermoelectric modules is70K at this time. That porous media material is inserted in the flue gas channel is able to reduce heat transfer resistance, and increase the heat flux and the mean temperature difference between the hot and cold side of thermoelectric modules. In this case, the maximum mean temperature difference is88K and the air excess ratio for the safe operation is greater than11.6.The experiment of the micro combustion thermoelectric power generation system with heat-recirculation is performed. The experimental results show that the overall thermoelectric conversion efficiency of the thermoelectric power generation system is low. With the increase of excess air ratio, the open-circuit voltage of the system drops. When the excess air ratio is26, the open circuit voltage of the system can reach up to1.9V. The reason why the system efficiency is low is analyzed, and some further improvements are put forward.