Research On Design And Aerodynamic Characteristics Of Wide-range TBCC Variable Combined Inlet

TBCC engine can not only take off and land from ground horizontally,but also sustain hypersonic cruise.It has broad development prospects in the fields of TSTO and hypersonic planes.Now the pain of the current TBCC research is that the upper working limit of the traditional turbine engine is about Ma2.5,but the lower working limit of the traditional ramjet engine is about Ma3,which leads to the problem of insufficient thrust in the Ma2.5-Ma3.Considering the problems of the traditional TBCC combined intake system,such as complex variable geometry mechanism,high aerodynamic drag,and large turbine modal loss,the design scheme of the translation and umbrella-shaped variable TBCC inlet were proposed in this paper,and the specific aerodynamic design research was carried out.The main contents are as follows:Firstly,a scheme of TBCC inlet with translational variable geometry was studied from the perspective of the system,and the overall design of the scheme was completed.The study found that compared with the others,the scheme of translational bottom compression surface had significant advantages in overflow resistance,complexity and thermal load of variable geometry mechanism,aerodynamic characteristics of turbine channel,flow characteristics ramjet channel,etc.Through zero-dimensional aerodynamic analysis of the scheme,the influence law of external compression parameters on inlet performance was studied.It was found that the combined compression of "single wedge plus isentropy" has excellent performance in both mass flow coefficient and total pressure recovery,before and after variable geometry;A design method of external compression based on geometric and aerodynamic matching rules was proposed,which could avoid the bad phenomenon of "compression-expansion-recompression" in the inlet;And the translational distance design was completed by studying the dual channel flow distribution law.Secondly,a ramjet channel with real-time shock wave elimination was studied and designed for the translation TBCC inlet.The influence rule of the self-starting boundary of the inlet was studied by combining the model with CFD method.It was found that the larger Mach number of the internal contraction section,the more error of the empirical formula of self-starting.In addition,it was found that using multi-stage lip and appropriately increasing shock distance could improve the self-starting performance.On this basis,a variable geometry inlet with convex shoulder was designed,which could effectively reduce the influence of flow separation and the total pressure loss.The 3D study of the inlet found that sweeping shock wave-boundary layer interference would bring significant negative effects,which can be avoided by designing boundary layer compartments.Thirdly,the parametric design of the turbine diffuser was studied for the translational TBCC inlet.The influence laws of expansion angle and centerline on anti-backpressure characteristics,total pressure recovery and total pressure distortion were analyzed by using CFD method.Founding the performance of the diffuser segment worked better when the the center line followed the slow first and then sharp law,and expansion angle with 6°.Based on Q criterion,the influence of section gradient on the vortex structure was studied.Combined with the analysis of total circumaxial pressure distortion,it was found that the hyperelliptic curve section gradient with slow first and then sharp law(nx =1.6),had the best comprehensive performance.Based on the above research,the 3D design of the turbine channel was completed and the characteristics of transonic velocity were studied.Finally,considering the translation variable geometry and other traditional TBCC turbine channel were long and usually designed with transition process from rectangle to circle,which leads to a large flow loss,the design and aerodynamic characteristics of the axisymmetric TBCC inlet with umbrella-shaped variable geometry were studied.Under the actual design background,the turbine mode,ramjet mode,transitional mode and modal conversion process were completed studied,then the 3D characteristics were also verified.The results showed that the designed inlet with variable geometry adjustment law had excellent performance,which met the design specifications of all working conditions,and verified the engineering feasibility of the scheme.