Numerical Simulation Research For Variable Geometry Inlet Of TBCC

Currently, as the requirement of aircraft’s speed and altitude is increasing,integrating the advantages of different types of engines becomes a trend, amongwhich TBCC (Turbine Based Combined Cycle) engine is one of the most promisingin combined propulsion system. As an air-breathing propulsion system, the inlet is oneof the important components. There is a crucial role in the inlet performance researchof TBCC engine.Firstly, the geometry structure of an over/under TBCC variable geometry inletis introduced. An inlet with the multi-wedge plate diffuser is designed to improve theoperating characteristics. It is simulated by FLUENT software and the calculationmethod used in the numerical simulation is validated through the reliable test. Theturbulence model of this article is S-A (Spalart-Allmaras) model which is suitable forthe aviation domain. DBCS (Density-Based coupled solver), AUSM+format andsecond-order upwind are adopted as well. Also, for FLUENT solving conditions inthis article, Sutherland formula is chosen as the laminar viscosity coefficient, andideal gas is assumed.Secondly, under the different flow conditions, investigation about the flow-fieldcharacteristic and the performance parameters is carried out through numericalsimulation, and characteristic comparison is done between the two-dimensional inletwith the multi-wedge plate diffuser and the conventional. The results indicate thattwo-dimensional inlet with the multi-wedge plate diffuser is slightly influenced bynon-uniform flow. In addition, it has a stronger ability to resist disturbance and theoutlet flow field in diffuser can be improved significantly. Under the non-uniformflow, compared with the conventional inlet, the total pressure distortion indicator (D)and the outlet temperature ratio (ψ) are decreased. Also, the outlet Mach number ofthe ramjet diffuser is smaller and the total pressure recovery ratio () is increased by10%. All that makes the engine thrust increased and the specific fuel consumptionreduced. Similarly, under the uniform flow, the flow-field characteristic of the inletwith the multi-wedge plate diffuser is more stable than the conventional and theaerodynamic performance parameters are better. Therefore, TBCC engine performan-ce is improved.Finally, at mode transition, the performances of TBCC variable geometry inletwith different angle of attack are studied in this paper. The flow-field characteristic and aerodynamic performance with different angle of attack are compared andanalyzed between the conventional inlet and the improved under different incomingflow. Results show that the internal flow-field of the inlet has been influenced withthe change of angle of attack. As the angle of attack increasing, the external pressureshock wave intensity has the same change. Either the angle of attack in positive ornegative, the total pressure recovery ratio will be reduced. The total pressuredistortion indicator and the outlet temperature ratio increase with the angle of attack,but the outlet Mach number decreases. Besides, the flow-field characteristic and theaerodynamic performance parameters are discussed in the modified inlet. And theyshow better performance compared with the conventional along with the unceasingchange of angle of attack. In light of this, the improved inlet has more superioradaptability to the change of angle of attack.