Design And Performance Study Of Surface Air-Oil Heat Exchanger

With the progress and development of the times,people have put forward higher requirements for the comprehensive performance of aircraft.With the increasing number and variety of airborne electronic equipment and the increase of integration,the heat load and heat flux of the whole machine are increasing sharply.Improving the aircraft cooling system and increasing its heat dissipation have gradually became the focus of attention.A surface air-oil heat exchanger is designed to improve the cooling capability and cooling efficiency of lubricant system of aeroengine in this paper.It can be applied to commercial aircraft,and it can effectively cope with the problem of large heat generated by aircraft at low speed sliding near the ground.The main works of this paper are divided into the following parts:Firstly,the lubricating oil cooling method of aircraft engine is briefly introduced.Then,the advantages and disadvantages of different types of heat exchanger are compared.The working principle,installation location and structural design of the surface air-oil heat exchanger are described in detail,and the process of heat transfer is analyzed in detail.Secondly,theoretical calculation and numerical simulation are used to analyze the variation of heat resistance,air pressure drop and incoming air velocity under the condition of air side flow.A small and low speed wind tunnel test bed is set up,the experimental results show that the experimental and theoretical errors are less than 25%under the conditions of air side flow,which proves that the boundary conditions of the numerical simulation are reasonable and the numerical simulation results are reliable.The heat transfer and flow pattern of the heat exchanger under actual working conditions are studied,and the optimum parameters of the fin under actual working conditions are obtained,the parameter of fin is N=44/t=1.0.Thirdly,three different runner structures are selected:cavity,S type and parallel runner,and the flow characteristics,pressure drop,flow uniformity are compared.Aiming at the problem of large pressure drop of S type and the problem of the poor flow uniformity of parallel runner,the design and structure optimization of flow path are carried out based on S flow channel.The separation runner is designed and optimized based on S type runner.The improved scheme is evaluated by orthogonal experiment and range analysis.The sensitivity of the structural parameters to the flow state is analyzed,which provides a theoretical basis for the design of the runner of heat exchanger.Finaly,based on the unit model,the calculation of the whole heat exchanger is carried out by using different computing domain division methods.The error of the two method is less than 2%,which verifies the difference between the computation domain partition method and the numerical calculation reliability.Calculate the heat dissipation and oil pressure drop of the surface air-oil heat exchanger under the actual working condition,which based on the optimal runner scheme is combined with the best fin parameter.The final optimized heat dissipation is 23.072KW,and the oil pressure drop is 298.522Kpa under the actual working condition.