| With the rapid development and extensive application of Micro Electro Mechanical Systems（MEMS）,the demand for portable micro power sources with high energy density,small volume,and stable output power is urgent.The micro power system based on hydrocarbon fuel combustion is currently a reliable solution.Among them,micro thermo-photovoltaic system is one of the most promising micro power systems with no moving parts and stable working for a long time.However,the poor flame stability,low combustion efficiency and low energy conversion efficiency caused by the short residence time and high thermal loss of hydrocarbon fuel combustion under microscale conditions pose significant challenges to the working performance and application of micro thermo-photovoltaic systems.To address these issues,the investigation on combustion characteristics and heat transfer of hydrocarbon fuels is carried out in this study,which combines experiment and numerical simulation.The influence of C0-C3 and oxygen-containing fuel DME on the premixed H2/Air combustion is summarized,providing theoretical guidance for the optimization design of micro thermo-photovoltaic systems.The main work is as follows:（1）The combustion characteristics of premixed H2/Air in micro-combustor are studied by micro-scale combustion experiment and numerical simulation.The mathematical model of In Ga As Sb PV cell is established.Effects of fuel rate and structural parameters on the flow field distribution,component concentration,combustion efficiency and thermal performance of the micro combustor are studied.The maximum energy density,electrical energy output and system efficiency of the micro thermo-photovoltaic system are calculated.When the H2 mass flow rate is m H2=1.00×10-6 kg/s,the optimized micro combustor-based thermo-photovoltaic system achieves an output power of 1.36 W.（2）Based on the findings of H2/Air combustion characteristics,the combustion stability and reaction kinetics of H2/C3H8/Air mixture under microscale conditions are investigated.The effects of the C3H8 mixing ratio,fuel/air equivalence ratio,total fuel flow rate and microcombustor structural parameters on flame stability are investigated through experimentes.The changes in combustion characteristics,such as temperature and concentration fields within the combustion chamber,as well as the high-temperature reaction pathways are analyzed and summarized.The study concludes that appropriate C3H8 mixing can effectively alter the flame position and temperature of the H2/Air mixture,as well as the reaction pathways,thereby adjusting the temperature distribution on the outer wall of the microcombustor and enhancing radiative performance of system.The findings of this study provide valuable insights into the combustion characteristics of microscale systems and have implications for the design and optimization of microcombustors.（3）Effects of CH4 and C3H8 blended fuels on H2/Air combustion at the microscale are compared.This study investigates the changes in combustion characteristics such as gas temperature distribution,component concentration,and OH radical generation rate caused by the blending of CH4 and C3H8.It is found that adding CH4 and C3H8 in pure H2combustion can adjust the flame height of H2/Air in the microcombustor,reduce waste gas heat loss,and expand the reaction zone thickness,thereby improving the thermal radiation performance of the system.The blending of CH4 and C3H8 alters the pathways of OH generation and consumption,as well as the sensitivity of OH,O,and H in the mixture.Under the same blending ratio,the OH-related reaction rate of H2/CH4/Air premixed fuel is higher,resulting in an increase in heat release rate and flame stability.（4）To further investigate the effects of hydrocarbon fuel components on the H2/Air combustion process and regulation of the microcombustor load range,a detailed reaction mechanism of the oxygenated fuel H2/DME is simplified using the DRGEPSA method.A kinetic model suitable for H2/DME combustion at the microscale is developed and the ignition delay and laminar flame velocity of H2/DME at different blending ratios are verified.Using three-dimensional numerical simulations,the combustion characteristics of H2/DME/Air at different blending ratios are studied in the micro combustor,and it is found that moderate blending of DME optimizes flow field distribution and forms secondary flames in the combustor,thereby enhancing gas-solid heat transfer performance.When the output chemical energy is Ec=74.9 W,40%H2/60%DME obtains 33.29 W of radiation power and 44.44%of radiation efficiency. |
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