Aerodynamic Performance Evaluation And Improved Design Of An Adjustable Inlet

In this paper,the aerodynamic characteristics of the original adjustable inlet are evaluated by numerical simulation method,and the aerodynamic characteristics of the inlet at design point and non-design points are obtained.On this basis,the improved design of the inlet is carried out,and the aerodynamic characteristics of the it are obtained by numerical simulation analysis.Firstly,the throat height of the original inlet is adjusted according to the throat regulation law in different inflow Mach numbers.Then the three-dimensional meshing and simulation calculation are carried out respectively.The results of numerical simulation show that the inlet satisfies the requirement of external oblique shock sealing on the top of the lip,and the reflection shock wave of the lip is eliminated at the entrance of the discharge chute.But there is a problem that the area of expansion section increases first and then decreases.The starting performance of the inlet is poor at low Mach number and high flight angle of attack under the non-designed inlet Mach numbers,especially at the angle of attack from-2 to 8 degrees at the inflow Mach number of 2.5,the inlet can not start.The starting performance of the inlet can be improved obviously by enlarging the throat properly or adopting suction measures.Secondly,according to the basic size and performance requirements of the original inlet,the two-dimensional aerodynamical improvement design of the external and internal compression sections is carried out,of which the result is calculated by numerical simulation method.The external compression section is still composed of two oblique and one positive waves.When the Mach number of incoming flow decreases to less than 2.5,the second stage external compression surface is rotated to change the inlet from a mixed-pressure inlet to an external-pressure one,during which the total turning angle of the air flow decreases by 6.2 degrees.The numerical simulation results show that the inlet achieves the external oblique shock sealing on the top of the lip at the design point and can start at the non-design Mach numbers.Thirdly,based on the aerodynamical two-dimensional design,the aerodynamical three-dimensional design is carried out,which shows a big difference between the numerical results of the three-dimensional model and that of the two-dimensional one.That is mainly because of the transverse overflow in the three-dimensional model.On this basis,the position of the Lip and the external compression surface as well as the position and opening size of the drain groove are adjusted accordingly.Ultimately,the three-dimensional model of the inlet which can meet the requirements of aerodynamic performance and starting performance is obtained.Finally,the numerical simulation analysis of the three-dimensional model of the inlet is carried out,which shows that the inlet performs well at the design point and the captured flow meets the design requirements.It's anti-pressure capability under the design Mach number is improved from 60 to 64 compared with the original model.The starting performance of the inlet is improved significantly under the non-suction circumstance.In detail,the inlet can start when the inflow Mach number is less than 2.5,and the range of flight angle of attack is enlarged.The anti-pressure capability of the inlet is obviously improved in typical unsigned inflow Mach numbers.