Configuration Design And Performance Research For An Airframe/Scramjet Integrated Hypersonic Vehicle

The configuration design and performance analysis of an airframe/scramjet integrated hypersonic lifting body vehicle was researched by using the method of numerical simulation and wind tunnel experiments.A baseline vehicle configuration based on the current research of scramjets was designed, the cowl-closed and cowl-open subscale test models have been built and tested in the wind tunnel, and numerical study was performed on the two configurations to examine the flow-field characteristics and longitudinal aerodynamic performance. A reasonable match between the computed and the test data showed that the CFD methodology may be used for further research at flow conditions where no experimental data was available with confidence. The CFD results were used to access effects of model scale and air flow conditions on the vehicle overall aerodynamic performance. It was indicated that the difference of friction drag coefficient of the wall surface was great, which was the main difference of the drag coefficient between full scale model and subscale model and that between wind tunnel test condition and flight test condition when the cowl door was opened.A computational code ChemTur3D was developed to simulate the reacting flows in scramjet engine combustors. To accurately compute the flow of a hydrogen/air mixture and combustion at high temperature, the turbulent and chemical nonequilibrium effects must be taken into account. The 3D Reynolds averaged Navier-Stokes equations and species conservation equations were solved using a finite volume, cell vertex scheme on three-dimension structured grids. Chemical reactions were modeled using finite rate chemistry between hydrogen and air consisting of seven species and eight reactions, and turbulent mixing was modeled using the Menter's Shear-Stress Transport (SST) approach. The AUSM+ scheme with the Monotone Upwind Scheme in Conservation Law (MUSCL) interpolation and second order central difference scheme were employed for the convection terms and the viscous terms, respectively. The LU-SGS implicit algorithm was used for the time integration, to eliminate the stiffness problem due to chemical reactions and turbulence, a point implicit method was implemented into the LU-SGS method. The code's implementation of parallel multi-blocking was realized in MPICH environment, and the numerical accuracy was evaluated by applying the program to compute several test cases.The analysis of flow field characteristics of scramjet combustor in direct-connect test and the integration of scramjet combustor/nozzle of baseline vehicle were carried out by using the code ChemTur3D. The performance of the baseline vehicle working at powered mode was evaluated by integrating the data of aerodynamic and that of propulsion accounting to the force accounting system. Results showed that positive thrust of the powered baseline vehicle was obtained at the angle of attack less than three degree, but the trimmed angle of attack was too high.Numerical simulations of different part configurations under cold flow condition have been performed, and the influence of each configuration design on the overall aerodynamic characteristics was analyzed. It was found that the airframe upper surface geometry featured Von Karman curve could provide a nose down pitch moment, which may be propitious to trim the large nose up pitch moment generated by the forebody. The effects of variation fuel mixing enhancement, distribution of fuel injection and equivalence ratio on the combustor performance were studied by numerical simulation under combustion flow condition.Based on these results, several enhancements to the baseline vehicle was adopted and the optimized vehicle was designed and analyzed, the optimized vehicle has a 16% larger capacity than the baseline one. Numerical simulation results showed that the optimized vehicle has a reduced trim angle of attack than the baseline one, and a better overall aerodynamic performance.This work has established a foundation for increasing the knowledge of the aerodynamics and propulsion performance associated with the different working mode of the hypersonic integrated vehicle free flight as well as supporting the highly airframe/scramjet integrated vehicle configuration design.