Flow Field Analysis And Optimization Of Defroster Air Duct System For Electric Vehicles

The defrost system of vehicle air conditioners has an important impact on the driving safety of the vehicle and the comfort of the occupants in the passenger compartment.In the winter of northern China,when the vehicle is exposed to a cold outdoor environment,frost on the outer layer of the windshield will affect the driver’s field of vision,and how to effectively remove the frost layer from the outer layer of the front windshield.At the same time,it is an important research subject with theoretical significance and engineering value to consider the thermal comfort of the passengers in the passenger cabin under defrosting condition.In this paper,an electric vehicle air conditioning defrosting system as the research object,the front windshield defrosting performance as the research objective,combined with numerical simulation analysis and optimization algorithm to complete the defrosting performance optimization of the front windshield.Firstly,the accuracy of the turbulence model used in the defrosting performance analysis is verified by a similar model method,which lays a foundation for subsequent numerical simulation analysis.Secondly,establish a defrosting analysis physical model of an electric vehicle air conditioning defrosting system,according to the national standard GB 1 1555-2009,through the use of computational fluid dynamics method,analyze the defrosting of the vehicle at an ambient temperature of-18℃ performance.Firstly,the steady-state analysis is used to obtain the flow velocity distribution of the near-wall surface of the windshield and the airflow inside the passenger compartment.Then,through the transient analysis,the frost layer thickness distribution and the temperature distribution cloud map of the outer surface of the windshield are obtained.The analysis results show that the velocity distribution of the near wall of the windshield is uneven,and there are some low-speed regions between the A and A’ regions of the windshield near the wall.These regions affect the overall defrosting effect of the field of view.Make the defrost efficiency slower.Thirdly,according to the above problem,the influence of the deflection angle of the defrosting style grille on the defrosting performance is mainly studied.The deflection angle of the style grid is set as the design variable,and the average velocity of the near wall of the partial region in the segment A is defined as an approximate model.The multi-island genetic algorithm is used to optimize the approximate model.Good grid deflection angle.Substituting the best position parameters into the model and verifying the defrosting performance of the electric vehicle.The research results show that the velocity distribution of the windshield near the wall surface can be effectively improved by optimizing the deflection angle of the style grille,and the defrosting efficiency is improved,so that the defrosting performance of the vehicle can meet the requirements.Finally,based on the preferred deflection angle of the defroster grille,considering the complex and unstable internal thermal environment of the car,the equivalent temperature index EQT is used to evaluate the thermal comfort of the driver in the car.Using the single factor analysis method,by studying the influence of different intake air flow rates in the defroster duct on the thermal comfort of the driver in the vehicle,comprehensively comparing the thermal comfort results of the driver under several working conditions,thereby making the car The air conditioning defrost system has good defrost performance and occupant thermal comfort.