| Micro electric vehicles are widely used in rural areas,towns,small cities and other areas as vehicles for daily use,cargo distribution,and security patrols.However,its own cruising range is extremely limited.If the battery capacity is increased,the weight and volume of the miniature electric vehicle will increase,which is not in line with the design and use of the miniature electric vehicle.Adding a range extender can effectively solve the cruising range problem of micro electric vehicles,but when the range extender starts running,it will destroy the good NVH performance of electric vehicles.Therefore,this paper takes the miniature range extender electric vehicle as the research object,and proposes a method to cover the range extender with a sound insulation cover to control its noise in view of the prominent noise problem when the range extender starts and runs,and uses sound insulation and sound absorption.It focuses on key issues such as the positional layout of the range extender and the sound insulation cover,the shape and structure of the sound insulation cover and the design of the internal heat dissipation pipeline,and conducts research on the sound insulation performance and heat dissipation performance of the sound insulation cover.Based on the principle of ensuring the heat dissipation performance,an air-cooled range extender sound insulation cover with better sound insulation performance is designed;at the same time,in order to meet the design requirements of the sound insulation cover for different models,a liquid-cooled range extender The design ideas of the sound insulation cover of the sound insulation cover were carried out,and the simulation analysis and verification of the acoustics and thermals were carried out for the two schemes.Considering the practical application of the sound insulation cover,the optimization scheme of the air-cooled range extender sound insulation cover was proposed,and the simulation verification of the optimization scheme was carried out.The optimized scheme was processed into a physical prototype,and the experimental verification of the optimization scheme was completed.(1)The arrangement and design of the range extender and sound insulation cover.The front cabin space of the miniature electric vehicle is narrow.The range extender unit is placed inside the sound insulation cover,and the exhaust muffler is led out of the sound insulation cover through the exhaust pipe and placed at the bottom of the car to save space and facilitate the design of the sound insulation cover.The air inlet of the sound insulation cover is facing the windward side of the car,and the relative movement of the car moving forward can be used to make cold air enter the inside of the sound insulation cover to take away the heat emitted by the range extender unit.Then a simplified three-dimensional model of the sound insulation cover and the range extender was constructed.The air-cooled scheme completely uses cooling air for heat dissipation,the liquid-cooled scheme uses liquid cooling for the cylinder body,and other parts use small pipes to pass cold air into it to dissipate heat.(2)Simulation analysis of sound insulation performance of sound insulation cover.The structural modes of the two schemes are analyzed,and the acoustic-vibration coupling method based on the structural mode is used to simulate and analyze the sound insulation performance of the sound insulation cover..Both schemes meet the technical requirements of the sound insulation cover and have good sound insulation performance.The sound insulation performance of the liquid-cooled scheme is better than that of the air-cooled scheme,and the sound insulation is increased by about 6d B(A).(3)Simulation analysis of the heat dissipation performance of the sound insulation cover.The cavity models of the two schemes are extracted as the fluid domain,and the mesh of the fluid domain is divided.The boundary conditions and simulation physical models are set according to the actual parameter data when the range extender of the micro electric vehicle is started and operated,and the CFD numerical calculation method is used.StarCCM+ software carried out the numerical simulation analysis of the air flow and temperature inside the sound insulation cover,and obtained the internal flow field and temperature field of the sound insulation cover for two schemes.Among them,the overall heat dissipation performance of the air-cooled solution is better than that of the liquid-cooled solution.The surface temperature of the generator,crankcase,cylinder head,inverter controller and other components and the air temperature inside the sound insulation cover are lower and better cooling effect.(4)Performance optimization and verification of the air-cooled scheme.Considering the processing problem of the sound insulation cover,an optimized scheme design is carried out based on the air-cooled scheme.A deflector was installed above the sound insulation cover to limit the air circulation space above the sound insulation cover,and the acoustic and thermal simulation analysis and verification of the optimized scheme were carried out.The optimized structure basically has no effect on the sound insulation performance,but improves the internal flow field of the sound insulation cover,so that the heat dissipation performance of the sound insulation cover becomes better.The optimized plan was processed into a physical prototype,and the prototype test and experiment were completed.It has been verified that the sound insulation performance and heat dissipation performance of the sound insulation cover meet the design requirements.It is proved that the simulation analysis of the sound insulation performance and heat dissipation performance of the sound insulation cover has a good reference.In this paper,according to the ideas of structure design,simulation analysis and optimization and improvement,a sound insulation cover with good sound insulation,sound absorption and heat dissipation performance is designed. |
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