Integrated Analysis And Optimization In Conceptual Design Of Airliners With Truss-braced Wing Configuration

In response to the increasing competition in civil transport market,a novel truss-braced wing(TBW)configuration has potential to be developed in the next generation single-aisle commercial aircraft.The significant features of truss-braced wing configuration are high wing aspect ratio,small wing sweep and thin wing thickness.The truss-braced wing configuration uses additional members(strut and jury)connecting the main wing and fuselage to reduce the wing bending moment,which leads to reducation of wing weight.One of key tasks during TBW aircraft conceptual design is multidisciplinary analysis such as aerodynamic and weight analysis,and benefit evaluation of fuel saving.To deal with this issue,a multidisciplinary analysis and optimization tool is established,by which comprehensive analysis and optimization for single-aisle TBW airliner conceptual design can be conducted.This tool can provide an effective way for integrated analysis and evaluation in TBW airliner conceptual design.The main contents of the thesis are as follows:1)A baseline design for single-aisle TBW airliner is proposed using the aircraft conceptual design method.A geometric model of the baseline TBW airliner is generated,which is used as a specific example for the multidisciplinary analysis and optimization in the conceptual design of TBW configuration aircraft.2)The optimization for natural laminar airfoil and design for laminar flow wing are studied.An in-house CFD software based on the Navier-Stokes equations and transition model is used for the boundary layer transition prediction of airfoil and wing.A two-step optimization strategy for the supercritical laminar flow airfoil design is proposed.The first step of optimization is to increase the ratio of the laminar flow region.The second step of optimization is to reduce shock wave and further increase the lift-to-drag ratio of the airfoil.A supercritical airfoil could be robustly optimized into laminar airfoil by the method.Based on the optimal airfoil,a supercritical laminar flow wing of TBW configuration aircraft is designed,and laminar region of the wing is obtained.3)The wing weight estimation method for TBW airliner is established by using the methods of parametric geometric modeling,parametric structural finite element modeling,flutter analysis and structural optimization.Based on the method,the influences of flutter constraints on wing weight are investigated,and also the influences of differents joints between the main wing and the truss(strut and jury)on wing weight are are analyzed.The surrogate model for truss braced wing weight predication is built using the wing weight estimation method,which can be used in multidisciplinary analysis of TBW airline conceptual design.4)A truss-braced wing multidisciplinary analysis tool(TBW-MAT)is developed for TBW airliner conceptual design,which includes modules of geometric,aerodynamic,mass,performance,engine,stability and economy anlyses.The integration of various analysis modules and user-friendly interface are implemented via MATLAB programming.The tool could reflect the aerodynamic and wing weight characteristics of the TBW aircraft.The baseline design of TBW airliner is analyzed by the tool(TBW-MAT).The analysis results show that the baseline TBW airliner has the characteristics of high lift-drag ratio,low fuel consumption and short take-off distance.5)Based on the multidisciplinary analysis tool,an optimization environment(platform)for the TBW airliner conceptual design is created in the software of iSIGHT-FD.The design variables include wing area,wing sweep,wing aspect ratio and the thrust of engine.The design targets can be the block fuel,maximum take off weight and direct operating costs,respectively.The baseline TBW airliner design is optimized in the optimization environment.The optimized results show that the fuel consumption of the optimal TBW airliner can be reduced by 23.3% compared to the conventional airliner.