| In recent years,with the rapid development of science and technology,the world situation has changed rapidly.The development of UAV has become the focus of all countries in the world.UAV has a very important strategic position in both military and civil fields.At the same time,higher requirements are put forward for the energy and power structure layout of the UAV.However,with the improvement of the power demand and maneuverability of the UAV propulsion device,the thermal load in the power cabin is aggravated.In order to optimize the structure layout of the power cabin and solve the heat source heat dissipation in the cabin,this thesis is based on the series hybrid UAV.Through theoretical analysis,numerical simulation and heat dissipation test,the thermal simulation analysis and air cooling optimization design of the power cabin are carried out to improve the heat dissipation performance of the power cabin.The main research contents include the following aspects.(1)Firstly,the numerical simulation method is used to simulate and analyze the flow field and heat source heat dissipation in the typical " down feed tail row " ventilation layout of the power cabin,and the parameters such as air distribution and heat source heat dissipation temperature at different speeds are obtained.Before that,the engine was subjected to different wind speed heat dissipation tests.Secondly,combined with the flow field,the heat source heat dissipation is analyzed and the engine heat dissipation simulation is verified and compared.It is concluded that the engine heat dissipation temperature error is within 5%,which verifies the accuracy of the simulation method.Finally,taking the average temperature of heat source heat dissipation as the thermodynamic boundary condition,the temperature field simulation analysis of the power cabin is carried out in combination with the flow field,and the heat dissipation performance in the cabin is discussed based on the heat dissipation performance evaluation method.(2)Through analyzing the influencing factors of heat dissipation performance,the power cabin is optimized,and the engine room is set as two parts : task cabin and power cabin.Secondly,according to the design requirements of the power cabin,the size range of the vent is divided,and based on the orthogonal test design method,9 different test combination schemes are calculated according to the heat dissipation evaluation standard.To obtain the optimal combination scheme,which is the ambient temperature of 25℃,the inlet wind speed of 30m/s,the inlet size of 150mm×150mm,and the outlet size of 170mm×170mm.Finally,the influence curve of engine heat dissipation temperature on the temperature of lithium battery and controller is obtained by simulation,and then the influence relationship between multiple heat sources is explored.(3)To analyzing the influencing factors of airflow organization,four ventilation layout forms are designed,and the best layout form of ’’ side supply and side row ’ is obtained.Secondly,according to the comprehensive factors such as the structural size of the power cabin,the position structure of the vent is parameterized and the parameter variation range is constrained.Finally,based on the response surface optimization method and the heat dissipation performance evaluation method,the optimal ventilation position and the best heat dissipation performance are obtained by calculation.Compared with the two schemes before optimization,the optimized heat dissipation efficiency is increased by 21% and 8% respectively,and the temperature standard deviation is decreased by 1.15℃ and 0.87℃ respectively.Compared with the typical layout,the optimized heat dissipation efficiency and standard deviation have been significantly improved.The research work of this thesis provides guidance basis and reference value for the field of thermal simulation and ventilation and heat dissipation. |
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