Numerical Study On Multi-dimensional Fluid- Solid-heat Coupling In Micro Swing Energy Power System

With the development of science and technology,the portable electromechanical equipment is widely applied.However,because of the higher requirements for battery life,the conventional battery technology can no longer meet the requirements.Due to the high energy density of hydrocarbon fuel and the high energy conversion efficiency of internal combustion engine,micro combustion engine has become an important research direction,and is expected to become an alternative energy type of battery.However,as the size of internal combustion engine decreases,the coupling law of flow,combustion and heat transfer gets complicated.In particular,the internal heat transfer laws have not been thoroughly studied.In this paper,numerical study on multi-dimensional fluid-solid-heat coupling in MICSE is simulated by using homemade program and commercial software.Based on the structure and working process of MICSE,multi-dimensional fluid-solid-heat coupling model is established,and the distribution of the transient temperature field of the multidimensional process of the working quality and the body are obtained.The numerical simulation of the body temperature field shows that the fluctuation of the temperature field of the body is only limited to the shallow surface of the combustion chamber.It is feasible to use equivalent steady state calculation instead of transient calculation,and it can save a lot of computation time.In order to study the influence of the change of heat transfer characteristics of MICSE on the strength and interference properties of the material,a thermal-structure coupling model of the MICSE is established.It is found that materials with larger thermal diffusivity,smaller thermal expansion coefficient and higher strength should be selected.They can make proper heat dissipation on the outside and increase the thermal barrier coating on the wall of the combustion chamber to reduce the overall temperature and ensure the stable operation and start-up of MICSE.Based on the multi-dimensional fluid-solid-heat coupling model of MICSE,the multi scale multidimensional working process is studied.The influence of the size of the MICSE on the coupling law of flow,combustion and heat transfer and the law of heat transfer is investigated.Results show that as the size of the MICSE decreases,the intake volume decreases,and the intake volume is further reduced owing to the enhanced internal heat transfer of the MICSE.With a larger specific surface area,the flow resistance increases,the eddy current was inhibited obviously,which is not conducive to the combustion organization,but the specific surface area increases,heat transfer enhancement and heat transfer heat up the working fluid in the intake and compression process,which improves the temperature of the working fluid before combustion,and accelerates the burning rate,which is beneficial for combustion.In the process of expansion and work,the intensification of heat dissipation is unfavorable to the efficiency.According to the data of multiple scale operation conditions,the empirical formula of heat transfer coefficient is corrected by statistical method,and the heat transfer law between the wall and the working medium is obtained.The heat transfer coefficient increases with the decrease of the scale and increases with the swing speed of the swing arm.So it means that in a certain range,the frequency increases,and the faster the engine runs,the higher the heat transfer.