Analysis Of Loss And Optimization On A Four Stroke Micro Internal Combustion Swing Engine

At present,with the development of mechanical and electrical equipment in miniaturization and portability,the energy supply system with long-term energy supply and high energy density is demanded.However,the chemical batteries are poor in energy density so that can not meet the requirements of mechanical and electrical equipment.Besides,the chemical batteries have other disadvantages like large mass and volume,low energy density,short power supply time and environment pollution.Due to the high energy density of hydrocarbon fuels and the high energy conversion efficiency of internal combustion engines,the miniature engines become an important direction for the energy power systems in miniaturization.In this paper,micro internal combustion swing engine is the research object.Based on numerical calculations,we study the effects of losses on the thermodynamic cycle process and performance of the system and learn how to control the losses on the micro internal combustion swing engine.The work and results are summarized below:(1)The physical and mathematical models of micro internal combustion swing engine /generator were established.The calculation method and convergence basis of the engine were given.The thermodynamic cycle process and operating characteristics of a engine were investigated via numerical simulations.The results show that the engine can start by itself and can quickly reach the steady-state operation,and there is no “dead point” in the operating process.(2)The effects of combustion loss,leakage loss,friction loss and heat loss on the thermodynamic process and performance of the engine were investigated.With regard to the thermodynamic cycle,the non-ideal combustion mainly deviates the cycle from the ideal OTTO cycle,while the other losses such as leakage,friction and heat transfer mainly reduce the compression ratio.The coupling of losses on the engine is non-linearly and complicated.The indicated power and thermal efficiency of the swing engine can be improved by reducing the burning time,leakage gap,inner wall temperature and friction torque.(3)The mechanisms of combustion loss,leakage loss and heat loss are strengthened with the reduction of the engine size that were analyzed.With regard to the size effect,the combustion loss and leakage loss are the most sensitive factors,the heat transfer is the second sensitive factor,and the friction loss is the smallest sensitive factor.(4)The optimal parameters,such as mass load,electromagnetic load,inlet and outlet diameter,flow coefficient and equivalence ratio on the thermodynamic process and performance of the engine were investigated.The larger mass load is,the larger compression ratio is,the less frequency is,the larger leakage loss is and the less combustion loss is.The larger electromagnetic load is,the less compression ratio is,the less frequency is,the less combustion loss is and the less leakage loss is.The larger mass load is,the higher the capacity of electromagnetic load is.The best of inlet and outlet diameter are between 3 ~ 5mm that was obtained.The best of equivalence ratio should be controlled between 0.8 ~ 1 that was obtained.In the given optimization algorithm,the actual machining accuracy was considered to simulate the real operating condition of the engine with basic size,the maximum thermal efficiency was obtained as 16.7% and the maximum indicated power was obtained as 243.3W.