Study On Structural Optimization Of Air Ductsystem For Aircraft

The air duct system of the aircraft, throughout the important parts of the fuselage, is one of the most significant components of the environment control system, and it is the bridge and the link that connect the air supply with air systems. The air duct system will be subjected to a variety of loads and constraints when work. Fatigue failure and large deformation of the air duct system caused by stress concentration not only have significant influence on the environment control system, but also lead the potential safety hazard to other systems around it. Therefore, the air duct system is required to have high reliability. This thesis takes bleed system of the air duct system as an example, based on the heat transfer analysis, the stress analysis, the compensation for piping and through these three parts to make structure optimization research for the bleed system. The main contents are as follows:(1)Making the calculation and analysis the characteristics of flow and heat transfer for bleed system, and determining the pressure and the temperature changes in the air ducts during operation, namely, besides valves and precooler, the pressure and temperature changes of air can be neglected.(2)Ensuring the loads and constraints that the air ducts suffered during operation and establishing the beam element calculation model of bleed system. Then, based on the finite element method, make static analysis to bleed system. Determine that the areas with stress concentration are bending parts in bleed system and the areas with large deformation are the end of pipes with refrigeration package.(3) Modeling the areas with stress concentration alone in bleed system and do static analysis, research the influence of related parameters of bends on the stress characteristics in stress concentration areas. Then modeling the part of bend with the bellow compensator and the temperature compensator and do the static analysis. Do the research of two kinds of compensator about compensation effect and influencing factors and compare the compensation effect of two methods.(4) After making structural optimization for bleed system by adding temperature compensator and tie rod, do the static analysis and determine the optimization effect by verifying components and operating conditions.The results show that can complete the structural optimization for the air duct system effectively by reducing the thickness of pipe, the ratio of the bend radius of curvature to the diameter of pipe, increasing the bending angle of bend and decreasing the diameter of pipe at the beginning of the piping design or adding temperature compensator and tie rod in the later.