Research On Active Control Of S-shaped Inlet Flow Separation

Due to its unique structure,the S-shaped air inlet makes the radar waves experience a series of reflections between the walls of large curvature after entering the air inlet,which reduces the radar’s scattering area and improves the invisibility.However,the Sshaped intake duct also makes the air flow more complicated.In the curved section with large curvature,the strong reverse pressure gradient will cause flow separation and complex secondary flow of the airflow,which will cause the total pressure of the inlet outlet section to be distorted,which will affect the working state of the compressor.For this reason,this article takes active control of the complex flow problem in the S-shaped inlet as the background,and uses two active flow control methods:DBD(Dielectric Barrier Discharge)plasma and plasma synthetic jet to improve the outlet pressure distortion of the inlet,and explore the two The best control scheme and control mechanism in this way.First,design and manufacture the S-shaped inlet wind tunnel test piece to study the characteristics of the flow field in the inlet.The PIV flow field test technology and pressure scanning valve were used to measure the flow field and pressure distribution along the inlet and the outlet section respectively,and the separation point position(x/L=0.27)and the separation area were clarified,and the outlet section was obtained at different wind speeds.The total pressure distribution and flow field characteristics.Then,the active control experiment of the flow separation of the S-shaped inlet by the DBD plasma was carried out.According to the principle of DBD plasma flow control,four plasma exciters with different induced airflow directions are designed.According to the position of the inlet flow separation point,a plasma exciter was arranged on the proximal wall of the inlet,and the effect of the position and layout of the exciter on the control effect of the steady-state pressure distortion at the inlet outlet was examined,and the DBD plasma The best solution to control the inlet flow field,when the incoming flow V=10m/s,the outlet steady-state pressure distortion index drops by 4.58%at the highest.At the same time,the control effect of different wind speeds is compared,and it is found that the dielectric barrier discharge plasma is suitable for the control of the inlet flow below 15m/s.Finally,the active control experiment of the flow separation of the S-shaped inlet by the plasma synthesis jet was carried out.Plasma synthesis jet exciters with different cavity volumes were designed,and the influence of electrical and structural parameters on the average exit velocity was investigated.Plasma synthetic jet actuators are placed on the proximal wall of the inlet,and the effects of the layout position,layout form,excitation frequency and jet aperture on the control effect of inlet pressure distortion are investigated.The experimental results show that:only in the S-shaped inlet A"Vshaped" plasma jet exciter is arranged near the separation point of the proximal wall.When the incoming wind speed is 15 m/s,the steady-state pressure distortion index at the outlet drops by up to 13.1%.And through the orthogonal experiment method,the order of the influence of various factors on the control effect of inlet pressure distortion is obtained as follows:layout position>jet aperture>excitation frequency>layout form.The research results of this paper provide a new active control technology for solving the problem of S-shaped inlet outlet pressure distortion.