| Due to the ability to flexibly control the inlet and outlet positions for easy installation and debugging,S-shaped ducts have been widely used in fluid mechanical engineering practice.However,the complex structure of S-shaped ducts imposes higher requirements on the design.In particular,in high flow rate suction conditions,the lip of the S-shaped duct is prone to large separation and induces strong flow vortices inside the duct,seriously affecting the duct’s flow capacity,outlet total pressure,distortion,and other performance characteristics,resulting in significant economic losses and even safety issues.Therefore,the suppression of lip separation in S-shaped flow channels has always been one of the key points in fluid transportation pipeline design.This article conducts an in-depth analysis of the S-bend flow channel in the intake system of aircraft with more complex flow,and explores the improvement direction to suppress the lip separation of the S-bend flow channel.The main work includes the following aspects.Firstly,the parametric design and optimization technology of S-shaped ducts were analyzed.The basic configuration of the S-shaped duct was determined based on the flow characteristics inside the lip of the S-shaped duct,and a parametric design technology was developed on this basis,laying the foundation for the subsequent optimization of the intake duct lip and the analysis of the impact of design parameters.In addition,the application technology of Isight platform in the optimization design of intake ducts was analyzed,laying the foundation for the subsequent optimization of the intake duct lip design.Secondly,the flow mechanism inside the S-shaped duct was analyzed through numerical simulation.To address the issue of flow separation at the lip of the S-shaped duct under ground conditions,a parametric design technology for the intake duct lip was used to determine the lip profile,and the flow mechanism of typical lip profiles causing separation was analyzed through numerical simulation to identify the key areas affecting flow separation,narrowing the scope of parameter selection for subsequent use of the Isight platform.At the same time,the intake duct lip profile was optimized to improve the performance of the intake duct.The results showed that a certain degree of blunting radius was needed at the leading edge of the lip to eliminate the separation vortex,and the downstream wall of the lip bottom corner area should be slightly convex inward and avoid the occurrence of large expansion and backflow area on the leeward side.Based on this,the Isight automatic parameter selection points and range were given,and the optimized lip profile improved the total pressure recovery coefficient by 1.8% and reduced the total pressure standard deviation by 13% compared to the original model.Finally,the optimization design of the intake lip on the Isight platform.The parameter optimization range was narrowed down based on the key areas identified in the study of the S-shaped duct lip flow mechanism.The Isight platform was then used to determine the optimal lip profile for the S-shaped duct that maximizes its performance.Furthermore,the study analyzed the impact mechanism of these design parameters on the performance of the intake lip.The results show that the optimized intake lip increases the total pressure recovery coefficient from 0.973 to 0.991 and reduces the standard deviation of the exit total pressure from 0.130 to 0.122.Moreover,it was demonstrated that the fully automated multi-objective optimization design method for the intake lip established in this study effectively suppresses the flow separation of the intake lip under ground conditions,providing important reference for the subsequent design of the S-shaped duct lip. |
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