Research On Combustion Characteristics And Performance Optimization Based On Micro-thermophotovoltaic Syste

The development of micro-mechanical manufacturing technology has promoted the rapid progress of micro-electromechanical systems,enabling it to play an important role in many fields,and also intensifying people’s demand for portable,compact and higher energy density power supplies.The micro-thermophotovoltaic（TPV）system is expected to be an alternative to portable energy supply for high-load continuous working scenarios due to its characteristics with no moving parts,simple structure and fast energy replenishment.Micro-combustor is the core component of the system.In the case of the same heat flux density per unit surface,the heat flux density per unit volume through the wall increase sharply and the power density of the system also enhance with the size decreases.However,as the combustion space shrinks,it also leads to a series of problems,resulting in reduced flame stability and thermal radiation performance of the combustor.In this paper,the combustion characteristics and thermal performance of micro-combustor in micro-TPV system are studied in four aspects by combining experiment and numerical simulation,aiming at improving the energy conversion efficiency of the system.The main innovations and mainline of this paper are listed in following.（1）A micro-scale combustion experiment bench and a micro-TPV system calculation model have established and the experimental and three-dimensional numerical simulations of H₂/Air premixed combustion have carried out on the combustor with bluff-body and the rearward-step structure.The impact laws of structural parameters such as the position and size of the blunt body,the length of the step,and operational parameters on combustion characteristics,flow field distribution,heat transfer processes,and other characteristic parameters have investigated.According to the In Ga As Sb PV cell energy conversion model,the effects of the above parameters on radiation efficiency,system efficiency and electrical output power have calculated and analyzed.（2）The premixed combustion characteristic of H₂/CO/Air has simulated and calculated.The effects of CO addition ratio on combustion process and reaction path have analyzed and the influence mechanism of adding CO to H₂/Air premixed combustion on flame anchoring and stretching has clarified.In addition,the orthogonal experimental design method has been used to investigate the influence laws of combustor structural parameter optimization on thermal performance,and the effect of each parameter on the thermal radiation performance of burner has been analyzed by combining the gray correlation method,which provided technical support for optimizing the design of micro-combustor with high radiation performance and flame stability.（3）Based on the experimental comparative study,the numerical model of porous media combustion with CH₄ blending has established,and the combustion characteristics of H₂/CH₄ mixed fuel in porous media have studied.The effects of the porosity,length of porous media and CH₄mixing ratio on the outer wall temperature of combustor have experimentally studied and analyzed.The power output and system efficiency of the micro-TPV system have compared.It is found that addition 25%CH₄ could promote combustion heat release and flame stability;porous media combustion is conducive to flame anchoring and enhanced gas-solid heat transfer,thus obtaining higher wall radiation temperature;the porosity has a dual effect on flame propagation and heat conduction.（4）Combined with the above results of fuel blending and porous media combustion,a porous media catalytic combustion model has established.The experimental comparison and analysis of different porous matrix materials and length supported Pt catalysts have carried out.The results show that the nickel-based porous media supported catalyst has stable and efficient thermal performance.In the global porous media catalytic combustion,the wall catalytic reaction plays a dominant role in inhibiting the gas phase combustion reaction,which reduces the flame temperature in the combustion chamber.The inhibition effect of wall catalytic reaction on gas phase reaction could be balanced by using locally supported catalyst,which changes the anchoring of the flame and promotes thermal recirculation in the combustion chamber,thereby improving H₂/CH₄/Air combustion stability and enhancing burner radiation performance.