V-shaped lip blunt de-heat reduction counter-design method based on bending shock wave theory

Abstract

The application relates to a V-shaped lip blunt deheat reverse design method based on a curved shock wave theory, and relates to a near-space hypersonic aircraft. Given a flow Mach number and a V-shaped lip expansion angle, the position of a leading edge detached shock wave is obtained according to a two-dimensional shock wave distance prediction method; given the geometric shape of a curved shock wave and a secondary transmission shock wave, the wall surface shape of the hypersonic section is reversely solved through a curved streamline / characteristic line method (MOCC) method; a five-order equation is used to fit the curve between the two points to reversely design the hypersonic- subsonic mixed section profile; according to the obtained profile of the hypersonic section and the hypersonic- subsonic mixed section profile, the profile of a straight leading edge section, a leading edge rounding radius and an expansion angle sweep are given to generate a three-dimensional internal turning inlet lip. The three-dimensional inlet lip blunt surface is reversely designed, so that the safety and stability of the three-dimensional internal turning inlet are improved.

Description

Technical Field

[0001] This invention relates to near-space hypersonic vehicles, and in particular to a V-shaped lip passivation and heat reduction reverse design method based on bending shock wave theory. Background Technology

[0002] In the field of aircraft design, the pursuit of high speed and long endurance is endless. Hypersonic vehicles, capable of cruising at speeds exceeding Mach 5, occupy a crucial position in aerospace strategy and interstellar exploration, possessing significant civilian value and strategic importance for a nation. During the development of hypersonic vehicles, the three-dimensional internal rotating inlet has attracted extensive research due to its advantages such as high flow capture coefficient, good compression characteristics, and low size and external drag. However, during hypersonic flight, the incoming airflow is drastically compressed, resulting in shock wave structures at different locations within the vehicle. Furthermore, the complex shock wave interference at the aerodynamic components of hypersonic vehicles restricts their endurance and affects their airframe safety. Shock wave interference alters the flow characteristics of the internal and external airflows and causes a surge in local aerodynamic / thermal loads, severely impacting safe flight and service life. This makes shock wave interference a critical research topic in the design and development of hypersonic vehicles. The lip shape of a three-dimensional internal rotating inlet is generally determined by the intersection of the capture inlet shape and the conical shock wave surface within the reference flow field. This results in a V-shaped lip structure. Passivation treatment of the V-shape, considering aerodynamic and thermal protection issues, causes the shock wave to detach and intersect at the leading edge stagnation region, resulting in complex shock wave interference. Therefore, addressing the shock wave interference phenomenon in the V-shaped passivated leading edge has extremely high engineering application and academic research value.

[0003] For typical V-shaped configurations, represented by the inward-rotating inlet lip (overflow port), the University of Science and Technology of China, the National University of Defense Technology, and other institutions have conducted in-depth research on the classification of shock wave interference types, aerodynamic / thermal / mechanical characteristics, and unsteady oscillations (Zhang Zhiyu. Research on shock wave interference and aerodynamic / thermal / mechanical characteristics of V-shaped blunt leading edge [D]. University of Science and Technology of China, 2020; Gao Wenzhi, Li Zhufei, Cao Rao, et al. Numerical simulation and analysis of the influence of V-shaped leading edge on the boundary layer flow of shock wave incident [J]. Propulsion Technology, 2019, 40(11):2488-2497). To facilitate parametric research, highlight key aspects, and ignore the influence of secondary factors, Xiao Fengshou et al. (Xiao F, Li Z, Zhang Z, et al. Hyperpersonic shock wave interactions on a V-shaped bluntleading edge[J]. AIAA Journal, 2018, 56(1):356-367) first refined a simplified V-shaped bluntleading edge configuration. The main parameters of the model are the leading edge expansion angle β, the leading edge blunting radius r, and the radius of the rounded corner at the root intersection R. Through experimental and numerical simulation studies, Xiao Fengshou et al. found that the special geometric contraction effect of the V-shaped bluntleading edge makes its shock wave interference phenomenon extremely complex, exhibiting three types of shock wave interference: regular reflection (RR), Mach reflection (MR), and same-side regular reflection (SRR). The complex shock wave interference structure will generate shock waves, shear layers, and supersonic airflow that impact the wall, and the wall heat flux will rise rapidly. Unexpectedly, simply increasing the leading edge blunting radius does not necessarily reduce the thermal load; on the contrary, it may lead to a higher thermal load. In particular, under high Mach number conditions, the peak wall heat flux even exceeds that of the classic Edney type 1 shock wave interference (Edney B E. The effects of shock impingement on the heat transfer around blunt bodies at M equal 4.6 and 7[J]. AIAA Journal, 1968, 6(1): 15-21). Under incoming flow Mach 4 conditions, Meng Zewei et al. (Meng Zewei, Fan Xiaoqiang, Tao Yuan, et al. Calculation and analysis of heat flux of V-shaped overflow port of three-dimensional internal contraction inlet[J]. Propulsion Technology, 2018, 39(8): 1001-4055) tracked and studied the aerodynamic thermal trend of shock wave interference at the V-shaped passivation leading edge with configuration parameters, which also revealed the severe thermal load characteristics. Therefore, it is particularly necessary to fully understand the characteristics of the flow field of various shock wave interferences at the V-shaped passivation leading edge, theoretically establish the correspondence between configuration parameters and shock wave reflection type and wall heat load, and reveal its transformation mechanism for the aerodynamic thermal protection design of the leading edge.Based on the above studies, there is still a lack of a reverse design method for the basic flow mechanism of V-shaped lips. Therefore, it is of great significance to study a heat reduction reverse design method for V-shaped lip passivation, taking into account the characteristics of the shock wave interference flow field at the V-shaped passivation leading edge. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing a V-shaped lip passivation heat reduction reverse design method based on bending shock wave theory, which can significantly reduce the shock wave boundary layer interference intensity of the passivated wall at the three-dimensional internal intake duct lip, weaken boundary layer separation, and thus reduce peak pressure and heat flux.

[0005] This invention includes the following steps:

[0006] 1) Given the incoming Mach number and the expansion angle of the V-shaped lip, the position of the leading edge detached shock wave is obtained according to the two-dimensional shock wave distance theory prediction method;

[0007] 2) Given the location of the intersection point of the detached shock wave, the Mach rod, and the reflected shock wave (i.e., the three-wave point), and based on the three-shock wave theory, obtain the location information and shock wave angle of the reflected shock wave in the primary shock wave interference zone, given the detached shock wave.

[0008] 3) Given the detached shock wave, the supersonic airflow is continuously compressed by the blunted lip curved wall, forming a series of isentropic compression waves. The compression waves gradually converge downstream to form a curved shock wave. Given the geometry of the curved shock wave and the secondary transmitted shock wave, the profile of the supersonic section wall of the curved wall is solved in reverse by the curved streamline / characteristic line method (MOCC).

[0009] 4) Based on step 2), the position information of the intersection of the V-shaped blunt leading edge profile and the V-shaped lip symmetry line is determined in reverse. By knowing the position information of the intersection point and the intersection point of the profile obtained in the supersonic segment, the curve between the two points is fitted with a quintic equation to design the supersonic-subsonic hybrid segment profile.

[0010] 5) Based on the known supersonic section profile and the supersonic-subsonic mixed section profile, a three-dimensional inward-rotating V-shaped blunt lip of the intake is generated by sweeping the given straight leading edge section profile, leading edge rounding radius and expansion angle.

[0011] This invention has the following advantages: This method realizes the inversion design of the passivation profile of the three-dimensional inlet lip. By reducing the shock wave intensity, adjusting the curvature of the curved shock wave, the curvature of the secondary transmitted shock wave, and the position of the three wave points, the shock wave boundary layer interference intensity of the passivation wall at the lip of the three-dimensional inward rotating inlet can be significantly reduced, the boundary layer separation is weakened, and thus the peak pressure and heat flux are reduced. At the same time, this inversion design method improves the safety and stability of the three-dimensional inward rotating inlet. Attached Figure Description

[0012] Figure 1 Heat flow and pressure distribution diagrams of the wall surface of the reverse-designed heat reduction model for V-shaped lip passivation and heat reduction, compared with the original model;

[0013] Figure 2 Diagram of the V-shaped passivated leading edge configuration;

[0014] Figure 3 A half-section side view of the V-shaped blunt leading edge configuration;

[0015] Figure 4 A schematic diagram of the wave system structure of the V-shaped leading edge Mach reflection flow field;

[0016] Figure 5 A schematic diagram of a V-shaped blunt-headed body with a straight leading edge and a detached shock wave in supersonic flow;

[0017] Figure 6 This is a schematic diagram of the three-dimensional intake duct lip passivation profile inversion design method.

[0018] The markings in the figure are as follows: 1 represents a V-shaped blunt straight leading edge blunt body; 2 represents a V-shaped blunt curved leading edge; 3 represents a detached shock wave generated at the leading edge; 4 represents the Mach bar in the primary shock wave interference zone; 5 represents the shear layer formed by the incoming flow in the rounded region; 6 represents the transmitted shock wave in the secondary shock wave interference zone formed by the curved shock wave 9 and the transmitted shock wave 11 near the wall; 7 represents the leading edge profile of the supersonic-subsonic mixed region; 8 represents the leading edge profile of the supersonic region; 9 represents the curved shock wave formed by the continuous compression of the supersonic airflow by the rounded curved wall; 10 represents the Mach bar in the secondary shock wave interference zone formed by the curved shock wave 9 and the transmitted shock wave 11 near the wall; 11 represents the transmitted shock wave in the primary shock wave interference zone near the wall; 12 represents the intersection of the three shock waves in the primary shock wave interference zone in the Mach reflection structure flow field; and 13 represents the center point of symmetry at the leading edge. Detailed Implementation

[0019] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] First, the basic design mechanism is introduced regarding the design methodology, establishing, for example... Figure 2 The simplified basic model of the V-shaped leading edge configuration shown is combined with Figure 2 and 3 The entire basic model consists of a V-shaped blunt straight leading edge blunt body 1 and a V-shaped blunt curved leading edge 2. The geometric properties of the V-shaped blunt curved leading edge 2 are represented by the curved leading edge radius R, such as... Figure 4In the schematic diagram of the Mach-reflecting flow structure, the airflow direction is from left to right. The detached shock wave is generated first at the straight leading edge, determined by the expansion angle β. The detached shock wave 3 generated at the leading edge meets the Mach rod 4 of the primary shock wave interference zone within the rounded region, forming the Mach-reflecting structure. The transmitted shock wave 11 and shear layer 5 of the primary shock wave interference zone originate from the intersection point 12 of the three shock waves in the primary shock wave interference zone and form a supersonic jet surrounded by the shear layer on both sides of the rounded region. The jet moves downstream along the wall, converging and colliding near the stagnation point, causing a large-scale reverse vortex pair to form downstream of the Mach rod, making the middle of the Mach rod bulge upstream. The supersonic airflow following the detached shock wave 3 generated at the leading edge is continuously compressed by the curved wall, forming a curved shock wave 9. The curved shock wave 9 and the transmitted shock wave 11 from the primary shock wave interference zone experience secondary shock wave interference near the wall, resulting in secondary Mach reflection and the formation of a Mach rod 10 and a transmitted shock wave 6 from the secondary shock wave interference zone. The transmitted shock wave 6 from the secondary shock wave interference zone incident on the wall, causing small-scale boundary layer separation. This shock wave / boundary layer interference significantly increases the wall load on both sides of the flow field, forming peak thermal / mechanical loads. By controlling the shock wave boundary layer interference, boundary layer separation can be effectively reduced, thus decreasing the peak heat flux.

[0021] like Figures 2-6 As shown, the V-shaped lip passivation and heat reduction reverse design method includes the following steps:

[0022] 1) Given the incoming Mach number Ma and the spreading angle β, such as Figure 2 and 3 The straight leading edge of the V-shaped leading edge model shown is essentially a swept-back cylinder. In a hypersonic flow field, the airflow and the straight leading edge first generate a detached shock wave 3. This detached shock wave will gradually develop along the flow direction and eventually reach a fully developed state, that is, the detachment height of the shock wave reaches a constant value. At this time, the detached shock wave DS on the plane of symmetry can be regarded as a two-dimensional oblique shock wave with a shock wave angle of β. The airflow perpendicular to the wave surface can be equivalent to the flow around a cylinder with a radius of r under supersonic conditions.

[0023] 2) The location of the leading-edge detached shock wave is obtained by introducing a two-dimensional shock wave distance theory prediction method based on modified Newton's law, such as... Figure 5 As shown, a detached shock wave 3 generated at the leading edge exists in front of the V-shaped blunt-edged straight-leading body 1. Points S and B correspond to the sound velocity points on the shock wave and the object surface, respectively, and the airflow direction is δ. S and δ B The dashed line SB represents the velocity of sound. These characteristics can be represented by the hyperbola shown in the following equation;

[0024]

[0025] Where x and y are coordinates, k = cosα, α represents the Mach angle, and the shock angle θ can be expressed as:

[0026]

[0027] To determine the detachment distance OD, we first need to establish the positional relationship between the shock wave and the object surface using the geometric relationship between point S and point B. The coordinates of point S are given as follows:

[0028]

[0029] Where, θ S The coordinates of point B represent the shock angle at point S, and the coordinates of point B depend on the shape of the object surface. Specifically, when the object surface is an arc:

[0030]

[0031] δ B δ s Both can be determined based on the corrected Newtonian rate. Assuming the sound velocity line is perpendicular to the flow direction, points S and B have the following geometric relationship:

[0032] x S =x B +(y B -y S )tanη (5)

[0033] in, Substituting equation (3) into equation (5), we get:

[0034]

[0035] Solving for:

[0036]

[0037] At this time, in equation (1), x D All external parameters have been determined, that is, the position of the leading edge detached shock wave can be obtained according to equation (1).

[0038] 3) such as Figure 6 As shown, by knowing the position of the detached shock wave 3 generated at the leading edge and the position of the intersection point 12 of the three shock waves in the given primary shock wave interference area, and combining the fact that the detached shock wave 3 generated at the leading edge is parallel to the V-shaped blunt straight leading edge blunt body 1, the shock wave angle can be known. Then, based on the three shock wave theory, the position and angle of the transmitted shock wave 11 in the primary shock wave interference area can be obtained.

[0039] 4) Given the geometry of the curved shock wave 9 and the transmitted shock wave 6 in the secondary shock wave interference zone, the structure type of the secondary shock wave interference and the shape of the leading edge profile 8 of the supersonic region before intersecting with the secondary transmitted shock wave are solved using the MOCC curved characteristic line method.

[0040] 5) Since the position of the three shock wave intersection point 12 in the primary shock wave interference zone has been given, the position information of the leading edge symmetry center point 13 on the leading edge profile 7 of the supersonic-subsonic mixed region is obtained by back-calculating the theoretical prediction method based on the position of the three shock wave intersection point. Using the end point of the supersonic region leading edge profile 8 and the leading edge symmetry center point 13 that have been obtained, the fifth-order equation is used for fitting, and the leading edge profile 7 of the supersonic-subsonic mixed region is obtained by smoothing the curve through the control point.

[0041] 6) Given the leading edge profile 8 of the supersonic region and the leading edge profile 7 of the supersonic-subsonic mixed region, the V-shaped blunt lip of the complete three-dimensional inward rotating air intake is generated by sweeping the straight leading edge segment 1 of the lip and the blunt radius of the lip.

[0042] Figure 1 A comparison of the wall heat flux and pressure distribution diagrams of the V-lip passivation heat reduction inverse design model and the original model is presented. Figure 1 It can be seen that the V-shaped lip model designed by the V-shaped lip passivation and heat reduction reverse design method based on bending shock waves shows a significant reduction in pressure and heat flow after simulation, with the magnitude reaching more than 20%.

Claims

1. A V-shaped lip passivation and heat reduction inverse design method based on bending shock wave theory, characterized in that... Includes the following steps: 1) Given the incoming Mach number and the expansion angle of the V-shaped lip, the position of the leading edge detached shock wave is obtained according to the two-dimensional shock wave distance theory prediction method; The specific steps for obtaining the location of the leading edge detached shock wave are as follows: The location of the leading-edge detached shock wave is predicted using a two-dimensional shock wave distance theory based on modified Newton's law. A detached shock wave generated at the leading edge exists in front of the V-shaped blunt-headed straight leading edge. Points S and B represent the sound velocity points on the shock wave and the object surface, respectively, with the airflow direction being δ. S and δ B These characteristics are represented by the hyperbola shown in the following equation; Where x and y are coordinates, α represents the Mach angle and shock angle. Represented as: To obtain the separation distance OD, the positional relationship between the shock wave and the object surface is determined by the geometric relationship between points S and B; the coordinates of point S are known to be: in, The coordinates of point B represent the shock angle at point S, and the coordinates of point B are related to the shape of the object surface; when the object surface is an arc: , Based on the corrected Newtonian rate, assuming the sound velocity line is perpendicular to the flow direction, points S and B have the following geometric relationship: in, Substituting equation (3) into equation (5), we get: Solving for: At this time, in equation (1) except All external parameters have been determined, that is, the position of the leading edge detached shock wave is obtained according to equation (1); 2) Given the location of the intersection point of the detached shock wave, the Mach rod, and the reflected shock wave (i.e., the three-wave point), and based on the three-shock wave theory, obtain the location information and shock wave angle of the reflected shock wave in the primary shock wave interference zone, given the detached shock wave. 3) Given the detached shock wave, the supersonic airflow is continuously compressed by the blunted lip curved wall, forming a series of isentropic compression waves. The compression waves gradually converge downstream into a curved shock wave. Given the geometry of the curved shock wave and the secondary transmitted shock wave, the profile of the supersonic section of the curved wall is solved in reverse by the curved streamline / characteristic line method. 4) Based on step 2), the position information of the intersection of the V-shaped blunt leading edge profile and the V-shaped lip symmetry line is determined in reverse. By knowing the position information of the intersection point and the intersection point of the profile obtained in the supersonic segment, the curve between the two points is fitted with a quintic equation to design the supersonic-subsonic hybrid segment profile. 5) Based on the known supersonic section profile and the supersonic-subsonic mixed section profile, a three-dimensional inward-rotating V-shaped blunt lip of the intake is generated by sweeping the given straight leading edge section profile, leading edge rounding radius and expansion angle.

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