Abstract:This paper gives a summary on curved shock compression research in the last decade. The new concept of curved shock compression system is proposed, in which specially designed 2D or 3D curved compression surface is applied. The leading shock wave would be curved due to its interaction with isentropic compression waves near the compression surface, and free stream is compressed by the curved shock wave together with the isentropic waves. Based on this concept, methods of: inverse designing supersonic internal f… Show more
“…The appropriateness of these computational method and mesh generation strategies has been validated for inward-turning inlets through several wind tunnel tests in Refs. 9, 24, and 25Figure 13.Schematic of structured mesh and boundary conditions.…”
Section: Irregular-shaped Inlet Design Based On Supersonic Nagic Flow...mentioning
Fighters have increasingly demanding performance on both aerodynamic and stealth. To adapt the design requirement of various irregular-shaped supersonic inlets integrated with flat fuselages, a design method for non-axisymmetric generalized internal conical (NAGIC) flowfield is discussed and then developed. By osculating axisymmetric flow concept and method of characteristics, the developed supersonic NAGIC flowfield can be inversely designed with arbitrary capture curves, controllable incident/terminal shock wave geometries, and post terminal shock wave pressure. Employing the streamline tracing technique, a set of external-compression inward-turning inlets with triangle-like flat capture shapes for supersonic stealth fighters are obtained to verify the design method. The study find that the internal contraction ratio and flow distortion of the inlet are reduced significantly by replacing the weak reflected shock wave in the original hypersonic NAGIC flowfield with a strong one. Thus, the compatibility between inlet and engine is improved in a relatively wide range. In addition, the irregular-shaped curved-compression inlet has high mass ratio and total pressure recovery ratio with negligible cross flow and uniform flow at throat. The performance of inlets with complex configurations can be further improved by matching the entrance geometries of basic flowfields and inlets.
“…The appropriateness of these computational method and mesh generation strategies has been validated for inward-turning inlets through several wind tunnel tests in Refs. 9, 24, and 25Figure 13.Schematic of structured mesh and boundary conditions.…”
Section: Irregular-shaped Inlet Design Based On Supersonic Nagic Flow...mentioning
Fighters have increasingly demanding performance on both aerodynamic and stealth. To adapt the design requirement of various irregular-shaped supersonic inlets integrated with flat fuselages, a design method for non-axisymmetric generalized internal conical (NAGIC) flowfield is discussed and then developed. By osculating axisymmetric flow concept and method of characteristics, the developed supersonic NAGIC flowfield can be inversely designed with arbitrary capture curves, controllable incident/terminal shock wave geometries, and post terminal shock wave pressure. Employing the streamline tracing technique, a set of external-compression inward-turning inlets with triangle-like flat capture shapes for supersonic stealth fighters are obtained to verify the design method. The study find that the internal contraction ratio and flow distortion of the inlet are reduced significantly by replacing the weak reflected shock wave in the original hypersonic NAGIC flowfield with a strong one. Thus, the compatibility between inlet and engine is improved in a relatively wide range. In addition, the irregular-shaped curved-compression inlet has high mass ratio and total pressure recovery ratio with negligible cross flow and uniform flow at throat. The performance of inlets with complex configurations can be further improved by matching the entrance geometries of basic flowfields and inlets.
“…The two-dimensional supersonic inlet is divided into conventional multi-stage wedge compression inlet and curved surface compression [13][14][15] inlet according to the external compression forms. Here we call them Case A and Case B, respectively.…”
Section: External Compression Configuration and Diffuser Designmentioning
confidence: 99%
“…According to the specific geometric constraints (length of the external compression wall, capture height, etc. ), the mathematical expression of the curved shock wave is given and then the mathematical expression of the curved compression wall is inversely designed using the method of characteristics (MOC) [16,17]. Compared with traditional wedge compression wall, the designed curved compression wall has shorter length and higher compression efficiency [18].…”
Section: External Compression Configuration and Diffuser Designmentioning
The design of a two-dimensional supersonic inlet with large bleed window at low Mach number was developed. Numerical simulation and wind tunnel experiments were carried out to investigate the aerodynamic performance and variable geometric rules of the inlet. The result indicates that the single-degree-of-freedom variable geometry scheme adopted in this paper guarantees the steady work of the inlet over a wide speed range. The large bleed window caused by rotation of the compression ramp appears near the throat at low Mach number. Low-pressure airflow near the bleed window neutralises the original high-pressure airflow behind the shock train, which decreases the overall pressure of the downstream region of the internal contraction section. To match the lower pressure, the structure of the shock train changes from strong
$\lambda$
-type to weak
$\lambda$
-type, and finally to a normal shock wave as backpressure increases at Mach number 2.5. Herein, the total pressure recovery coefficient of the inlet near the critical condition improves by 8.5% as the backpressure ratio (Pe/P0) adds from 13 to 14.6 at Mach number 2.5. It proves that the scheme is effective on terminal shock wave control and inlet performance improvement. In addition, due to the background wave and the bleed window, two kinds of shock wave oscillation occur when the backpressure ratio is 13.1.
“…), the mathematical expression of the curved shock wave is given, and then, the mathematical expression of the curved compression wall is inversely designed using the method of characteristics (MOC). 28 Compared with traditional wedge compression, curved compression 29 has shorter length and higher compression efficiency which ensures the slower velocity of airflow at the throat. Then, the wedge compression is utilized as the second compression wall which is constructed artificially after the curved compression wall based on the oblique shock wave theory.…”
Section: Numerical Simulation and Wind Tunnel Experimentsmentioning
Design of a supersonic inlet with double S-bend diffuser was developed. Numerical simulation and wind tunnel experiment were carried out to investigate the aerodynamic performance and variable geometric rules of the inlet. The result indicates that the variable geometry scheme adopted solves the contradiction between starting performance at low Mach number and aerodynamic performance at high Mach number. The inlet works normally and stably over a wide speed range. At design point, the total pressure recovery coefficient reaches 0.47. In addition, two different kinds of inlets with double S-bend diffuser and single S-bend diffuser were studied. Compared with the double S-bend diffuser, the total pressure recovery coefficient of the single S-bend diffuser is higher at low Mach number (Ma0 < 3) and lower at high Mach number (Ma0 > 3). With the increase of backpressure, shock train mainly moves upstream along the low-energy flow region in the diffuser. For the double S-bend diffuser, shock train will first move along the lower corner and then along the upper corner. For the single S-bend diffuser, it will only move along the upper corner. The strong secondary flow of the double S-bend is the main reason for the above phenomenon.
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