Study On Catalytic Combustion Characteristics Of Hydrogen In The Micro Nozzle-jet Combustor

Recently,with the development of miniaturization in mechanical and electronic devices,a variety of micro-electromechanical systems have emerged,such as micro-sensors,micro-aircrafts and micro-pumps.However,due to the large volume,high pollution and low energy density of conventional electrochemical batteries,even lithium batteries with high energy density cannot provide continuous and reliable power for various micro-electromechanical systems.However,it has been found that the energy density of hydrocarbon fuel is almost 100 times that of lithium batteries,and the energy density of hydrogen fuel can even reach 300 times that of lithium batteries.Therefore,the micro combustion technology based on hydrogen and hydrocarbon fuels has become a viable solution.In the micro combustion process,the surface-area-to-volume ratio will be increased when the combustor is scaled down,which will cause a great heat loss.In addition,the reduction in scale will also lead to a shortened residence time of the high-velocity gaseous mixture in the micro combustor,thereby reducing the combustion efficiency.Therefore,it has been a key issue to be solved urgently to improve the combustion stability in micro combustors,and catalytic combustion has been proved to be an efficient method to stabilize combustion.In this paper,supported by the National Natural Science Foundation of China“Study on the stable combustion mechanism and performance synergistic optimization of micro nozzle-jet combustors with Pt catalytic coating” [51976054],the numerical simulation method is employed to investigate and analyze the progress of catalytic combustion,flow and heat transfer in the micro nozzle-jet combustor.The main research work and its innovations are summarized as follows:(1)The numerical model for the catalytic combustion of a micro nozzle-jet combustor was established,and the validity of the numerical model was v erified.The effects of different inlet velocities of hydrogen and air on the mass fraction of hydrogen,oxygen and water vapor in the micro nozzle-jet combustor were explored and obtained.(2)The chemical reaction characteristics of key gas phase compon ents such as hydrogen and OH radicals during the catalytic combustion process of the micro nozzle-jet combustor were studied,and the effects of hydrogen and air inlet velocity,inlet temperature,hydrogen/oxygen equivalent ratio and wall material on the catalytic combustion characteristics of hydrogen in the micro nozzle-jet combustor were analyzed.(3)The flow characteristics and heat transfer characteristics of the catalytic and non-catalytic combustion process in the micro nozzle-jet combustor were compared and analyzed.The results show that the catalytic combust or has a lower gaseous mixture flow velocity,a higher reaction heat generation rate at the gas-solid interface,and a higher catalytic combustion efficiency.