Characteristics Of Micro Porous Media Combustor With Heat-recirculation

Due to the characteristics of high energy density and flexible way of energy output, micro gas turbine power generation system can not only provide power for micro aerial vehicles as micro power systems but also supply electricity for portable electronic devices as micro electric power. Thus, it will be applied in a variety of micro devices. Micro combustor is one of the core components of micro gas turbine power generation system. With the decrease of the scale, the ratio of surface area to the volume of micro combustor and heat loss of micro combustor increase, resulting in the conversion efficiency of thermoelectric of micro combustion turbine power generation system is very low. Consequently, the design of micro combustors which have higher thermal efficiency and smaller heat loss is very important to develop the micro gas turbine power generation system. With the consideration of super adiabatic combustion, a micro porous media combustor with heat-recirculation is designed based on heat-recirculation technology and porous media combustion technology and some research work on combustion characteristics of the micro porous media combustor with heat-recirculation is done by experimental and numerical simulation in the present dissertation.The experiment of the micro homogeneous porous media combustor with heat-recirculation is performed. The experimental results show that combustion efficiency of combustor is above70%and outlet temperature is greater than800K while excess air ratio is from1.0to3.0. The combustion phenomenon of heat-recirculation interlayer is appeared in certain operating conditions, resulting in high wall temperature and high heat loss ratio. The flow fields and temperature fields of the micro homogeneous porous media combustor with heat-recirculation are studied with numerical simulation. The numerical analysis shows that some premixed gas of heat-recirculation interlayer through the center area of porous media plate into the combustion chamber, therefore the residence time of the premixed gas in the combustion chamber is decreased and this results in the lower combustion efficiency. In order to overcome the defects in the performance of the micro homogeneous porous media combustor with heat-recirculation, the micro variable porosity porous media combustor with heat-recirculation is designed and experimental investigation on the H2/Air premixed and diffusion combustion is carried out. The experimental results show that combustion operation ranges of the improved combustor in the way of diffusion combustion is wider than that of the way of premixed combustion, and it can be up to8.0. Higher combustion efficiency and higher exhaust gas temperature can be obtained from diffusion combustion in the wider combustion operation ranges. Combustion efficiency of combustor is above98%and exhaust gas temperature is greater than1000K while excess air ratio is from0.8to4.0and combustion power is100W. Moreover, lower wall temperature and lower heat loss can be got, the heat loss ratio of the micro combustor decreases with the increasing of combustion thermal power and excess air ratio. Especially in the combustion power of100W and excess ratio of4.0, exhaust gas temperature of combustor is close to1000K and corresponding external wall temperature and heat loss ratio is only512K,9.24%, respectively, this is the optimal operating conditions for the micro gas turbine power generation system.The numerical simulation of combustion process of micro variable porosity porous media combustor with heat-recirculation is investigated in a different way of combustion with CFD. It is concluded that interior temperature gradient in the combustor in the way of diffusion combustion is greater than that of the way of premixed combustion. Heat-recirculation interlayer and both sides of porous media plate have a significant temperature difference in both combustion modes. The structure of micro variable porosity porous media combustor with heat-recirculation has been optimized by numerical simulation. Conclusions are reached that the combustion performance of micro combustor is the best while the diameter ration of porous medium plates (P1, P2) is10to9.In general, it is indicated that heat loss from the micro porous media combustor to the external environment can be efficiently absorbed by the incoming gas, which exist in heat-recirculation interlayer and micro porous media, adopting the special structure of heat-recirculation interlayer and opposite direction inlet mode of reaction gas through porous media plates. The heat enthalpy and temperature of the incoming gas are improved. The combustion reaction rate is accelerated, and reaction intensity is strengthened. Therefore, combustion stability, thermal efficiency and exhaust gas temperature are efficiently improved in micro combustor. Heat loss of micro combustor is reduced, and thermal performance of micro combustor is raised. The micro variable porosity porous media combustor with heat-recirculation is a kind of low heat loss of micro combustor, and it has a very important application value in developing the Micro gas turbine power generation system.