A parametric design method for axisymmetric precooling inlet

Abstract

The present invention discloses a parameterized design method for an axisymmetric precooling inlet. For the design of an axisymmetric precooling inlet, a parameterized design method is proposed based on the existing experience in designing an inlet. The design method can determine the inner profile of the inlet through a series of control parameters. The method can quickly obtain the inner profile of the precooling inlet corresponding to different control parameters, which is beneficial to the rapid design and performance evaluation of the axisymmetric inlet.

Description

Technical Field

[0001] The invention relates to the field of air intake duct design, and specifically designs a parameterized design of an axisymmetric precooling air intake duct. Background Art

[0002] When operating at high Mach numbers, ordinary aircraft engines will encounter the problem of high stagnation temperature of incoming flow and low thermal efficiency. The precooling engine scheme with a precooler upstream of the engine has become an effective solution to this problem. A large amount of research has proved that this scheme can effectively improve the engine's operating speed range and improve thermal efficiency. The air inlet is one of the important components of an air-breathing engine, and the perfection of its design is related to the performance of the entire propulsion system. The operating Mach number of the precooler-type air inlet is generally 0-6. In order to be able to fly in a wide speed range, high requirements are placed on the design method of the air inlet. The existing design methods are generally based on trial and error based on past experience, and there is a lack of a rapid design method. This parametric design method combined with a computer program can quickly generate a precooling inlet profile, providing a basis for subsequent optimization design. Summary of the invention

[0003] In order to quickly obtain the profile of an axisymmetric pre-cooling inlet duct and facilitate subsequent inlet duct performance evaluation, the present invention provides a parameterized design method for an axisymmetric pre-cooling inlet duct.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A parameterized design method for an axisymmetric precooling inlet duct, the axisymmetric precooling inlet duct comprises a compression surface tip point of the inlet duct, an end point of an outer compression surface, an end point of a first inner contraction section on the compression surface side, an end point of a meridian straight section on the compression surface side, an end point of a second contraction section on the compression surface side, a tail cone starting point, an end point of a tail cone, an end point of an inlet duct on the compression surface side, a lip mask tip point, an end point of a first inner contraction section on the lip mask side, an end point of a meridian straight section on the lip mask side, an end point of a second inner contraction section on the lip mask side, an end point of a precooler domain, an end point of an inlet duct on the lip mask side, a starting point of a deflation seam, and an outer lip mask angle point; the design method comprises the following steps:

[0006] The first step is to determine the overall size of the air intake duct;

[0007] Given the total length of the inlet duct L1, the inlet duct outlet radius R1, and the inlet duct capture radius R2, the compression surface tip is taken as the coordinate origin (0,0), and the direction of the airflow without an angle of attack is the positive direction of the x-axis; the total length of the inlet duct L1 is equal to the x-axis coordinate value of the end point of the inlet duct on the compression surface side; the inlet duct outlet radius R1 is equal to the y-direction distance between the end point of the inlet duct on the compression surface side and the end point of the inlet duct on the lip mask side; the inlet duct capture radius R2 is equal to the y-axis coordinate value of the lip mask tip;

[0008] The second step is to determine the tip position of the lip mask and the outer compression surface;

[0009] Given the compression surface semi-cone angle θ1 and the shock seal Mach number Ma0, the conical shock wave is solved to determine the length of the external compression surface L2, which is equal to the x-axis coordinate value x9 of the lip mask tip; and the x-axis coordinate value x2 of the end point of the external compression surface is the same as the lip mask tip:

[0010] The third step is to determine the profile of the first inner contraction section; the inner contraction section profile is composed of the first inner contraction section, the meridian straight section and the second inner contraction section; first determine the profile of the first inner contraction section on the lip mask side, and give the length of the first inner contraction section L3 and the lip mask angle θ2; the starting point of the first inner contraction section on the lip mask side is the lip mask tip, and the profile of the first inner contraction section on the lip mask side is a straight line. According to L3 and θ2, the coordinates (x 10 ,y 10 ), which is determined by the first inner contraction section profile on the lip mask side;

[0011] Next, determine the profile of the first inner contraction section on the compression surface side, give the inner contraction ratio ICR1 of the first inner contraction section, and for the axisymmetric inlet duct, calculate the annular area to obtain the y coordinate of the end point of the first inner contraction section on the compression surface side, and the x coordinate x3 of the end point of the first inner contraction section on the compression surface side and the x coordinate x1 of the end point of the first inner contraction section on the lip mask side. 10 The same, thus the coordinates of the end point of the first inner contraction section on the compression surface side are determined;

[0012] The starting point of the first inner contraction section on the compression surface side is the end point of the outer compression surface. The profile of the first inner contraction section on the compression surface side is determined by a cubic curve and is tangent to the profile of the outer compression surface at the starting point and tangent to the horizontal line at the end point.

[0013] The fourth step is to determine the meridian plane straight segment profile; the meridian plane straight segment is a horizontal straight segment. Given the meridian plane straight segment length L4, the coordinates (x4, y4) of the end point of the meridian plane straight segment on the compression side and the coordinates (x 11 ,y 11 ) and determine the straight section profile of the meridian plane;

[0014] Step 5: Determine the second inner contraction section profile; the second inner shortening section profile approaches from the outside to the inlet duct axis; given the second inner contraction section length L5, the equal annular contraction ratio ICR2 and the meridian contraction ratio ICR3; determine the x coordinates x of the second contraction section end point on the compression surface side and the second contraction section end point on the lip mask side by the second inner contraction section length L5 12 ; The distance H1 between the end point of the meridian equal straight segment on the compression side and the end point of the meridian equal straight segment on the lip mask side is the same as the distance H2 between the end point of the second contraction segment on the compression side and the end point of the second inner contraction segment on the lip mask side; after ICR2 is given, the y coordinate y of the end point of the second contraction segment on the compression side is preliminarily determined 5aand the y coordinate y of the end point of the second inner contraction section on the lip mask side 12a ;

[0015] The internal contraction ratio of the second internal contraction segment is further adjusted, and the meridian contraction ratio ICR3 is given. ICR3 is defined as the internal contraction effect caused by the decrease of H2 relative to H1, which is manifested as the y coordinate of the end point of the second internal contraction segment on the lip mask side further decreasing; the y coordinate y5 of the end point of the second contraction segment on the compression surface side and the y coordinate y of the end point of the second internal contraction segment on the lip mask side are determined by the equal annular contraction ratio ICR2 and the meridian contraction ratio ICR3. 12 ;

[0016] The second inner contraction section profile is generated by a cubic curve and is tangent to the upstream meridian plane straight section and the downstream expansion section curve; thus, the second inner contraction section profile is determined;

[0017] The sixth step is to determine the profile of the expansion section of the inlet duct; there is a tail cone in the axisymmetric inlet duct, and the coordinates of the starting point of the tail cone are determined by the relative position of the starting point of the tail cone between the end point of the second contraction section on the compression surface side and the end point of the inlet duct on the compression surface side; with the end point of the second contraction section on the compression surface side as the starting point and the end point of the inlet duct on the compression surface side as the end point, the relative position percentage a1 in the x direction between the end point of the second contraction section on the compression surface side and the end point of the inlet duct on the compression surface side and the relative position percentage a2 in the y direction are given to determine the coordinates (x6, y6) of the starting point of the tail cone; since the y coordinate of the end point of the tail cone is 0, the relative position percentage a3 in the x direction between the end point of the second contraction section on the compression surface side and the end point of the inlet duct on the compression surface side is given to determine the coordinates (x7, y7) of the end point of the tail cone;

[0018] The coordinates of the end point of the precooler domain are determined by the relative position between the end point of the air inlet duct on the compression surface side and the end point of the air inlet duct on the lip mask side; the y coordinate of the end point of the precooler domain is the same as the end point of the air inlet duct on the lip mask side. Given the x-axis relative position percentage a4 between the end point of the air inlet duct on the compression surface side and the end point of the air inlet duct on the lip mask side, the x coordinate x of the end point of the precooler domain is determined. 13 ;

[0019] Step 7: Determine the profile of the precooler;

[0020] The precooler configuration is set to a multi-stage ladder type; the precooler area is located between the starting point of the tail cone and the end point of the precooler domain. After determining the number of precooler steps b, each stage is evenly distributed between the starting point of the tail cone and the end point of the precooler domain; there is no overlap between the stages in the y direction, and there is an overlap of 1 / 4 of the stage width between the stages in the x direction;

[0021] Step 8: Determine the location and form of the venting seam;

[0022] The x-direction position of the venting seam is determined by the relative position of the venting seam between the tip of the compression surface and the starting point of the tail cone. The position of the venting seam on the compression surface of the inlet duct is determined by the relative position percentage a5 between the tip of the compression surface and the starting point of the tail cone in the x-direction. After the number of venting seams c, the width of the venting seams L6, the interval of the venting seams L7 and the width of the venting cavity outlet L8 are given, the form of the venting seam can be determined.

[0023] The ninth step is to determine the outer lip cover profile; the outer lip cover length L9 is the x-direction distance from the outer lip cover corner point to the lip cover tip point.

[0024] Furthermore, in the second step,

[0025] L2=x9=x2=R2 / tanβ

[0026] y9=R2

[0027] y2=L2*tanθ1

[0028] y9 is the y coordinate of the tip of the lip mask.

[0029] Furthermore, in the third step,

[0030] x 10 =x9+L3

[0031] y 10 =y9+L3*tan(θ1-θ2)

[0032]

[0033] x3=x 10 .

[0034] Furthermore, in the fourth step,

[0035] x4=x 11 =x3+L4

[0036] y4=y3

[0037] y 11 =y 10 .

[0038] Furthermore, in the fifth step,

[0039] x5=x 12 =x4+L5

[0040]

[0041] y5=y 5a

[0042]

[0043] Furthermore, in the sixth step,

[0044] x6=(L1-x5)·a1+x5

[0045] y6=y5-y5·a2

[0046] x7=(L1-x5)·a3+x5

[0047] x 13 =(L1-x5)·a4+x5

[0048] Furthermore, in the third step, the relationship between the lip mask angle θ2 and the compression surface semi-cone angle θ1 is:

[0049] θ2≤θ1.

[0050] Furthermore, in step 8, the flow direction of the venting seam is:

[0051] 30%≤a5≤80%.

[0052] The width of the vent cavity outlet is smaller than the sum of the widths of the vent slit inlets, that is,

[0053] L8≤c*L6.

[0054] Furthermore, in the ninth step, the lip mask structural angle θ3 is:

[0055] θ3≥6°.

[0056] Furthermore, in the third, fourth and fifth steps, the inner contraction section of the air inlet is designed in stages, including a first inner contraction section, a meridian straight section and a second inner contraction section.

[0057] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: (1) it can quickly provide an initial profile for a pre-cooling axisymmetric air inlet, facilitating subsequent air inlet performance evaluation; (2) it can quickly obtain different air inlet profiles by modifying air inlet parameters, thereby eliminating unreasonable factors in the air inlet design at the initial stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is the number of each key point of the air intake duct.

[0059] Figure 2 It is a schematic diagram of intake duct parameters.

[0060] Figure 3 It is a local enlarged view of the venting seam and a schematic diagram of the venting seam area parameters.

[0061] Figure 4 It is a parametrically designed three-dimensional model of the air intake. DETAILED DESCRIPTION

[0062] In order to make the technical method and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings. Specific values ​​of various parameters of the air intake duct are given below, and the designed three-dimensional profile is shown in the figure.

[0063] 1. Determine the overall size of the intake duct

[0064] Given the total length of the inlet duct L1 = 7200mm, the inlet duct outlet radius R1 = 450mm, and the inlet duct capture radius R2 = 500mm. With the compression surface tip as the coordinate origin (0,0), the direction of the airflow without an angle of attack is the positive direction of the x-axis; the total length of the inlet duct L1 is equal to the x-axis coordinate value of the inlet duct end point (8) on the compression surface side; the outlet diameter R1 is equal to the y-direction distance between the inlet duct end point (8) on the compression surface side and the inlet duct end point (14) on the lip mask side; the inlet duct capture radius R2 is equal to the y-axis coordinate value of the lip mask tip (9). After the total length of the inlet duct L1, the inlet duct outlet radius R1, and the inlet duct capture radius R2 are given, the overall size of the inlet duct is determined, which also provides a magnitude reference for the size of the detailed parts of the inlet duct.

[0065] 2. Determine the tip position and external compression surface of the lip mask

[0066] Given the compression surface semi-cone angle θ1 = 14°, the shock seal Mach number Ma0 = 5, and solving the conical shock wave (the conical shock wave solution requires the use of program iteration calculation), it can be determined that the length of the external compression surface L2 = 1400.8 mm, the length of the external compression surface L2 is equal to the x-axis coordinate value of the lip mask tip (9), and the x-axis coordinate value of the external compression surface end point (2) is the same as the lip mask tip (9). The lip mask tip (9) and the external compression surface end point (2) are determined, the inlet duct external compression surface is a conical surface, and the inlet duct external compression surface profile is determined.

[0067] L2=x9=x2=R2 / tanβ

[0068] y9=R2=500mm

[0069] y2=L2*tanθ1=349.25mm

[0070] 3. Determine the profile of the first inner contraction section

[0071] The inner contraction section profile is composed of the first inner contraction section, the meridian plane straight section and the second inner contraction section. This step gives a method for determining the first inner contraction section profile. First, the first inner contraction section profile on the lip mask side is determined, given the first inner contraction section length L3 = 495 mm, and the lip mask angle θ2 = 12°. The starting point of the first inner contraction section on the lip mask side is the lip mask tip (9), and the profile of the first inner contraction section on the lip mask side is a straight line. According to L3 and θ2, the coordinates of the end point (10) of the first inner contraction section on the lip mask side can be obtained, and thus the profile of the first inner contraction section on the lip mask side is determined.

[0072] x 10 =x9+L3=1895.77mm

[0073] y 10 =y9+L3*tan(θ1-θ2)=517.24mm

[0074] Next, the profile of the first inner contraction section on the compression surface side is determined. It is necessary to give the first inner contraction section inner contraction ratio ICR1=1.44. For the axisymmetric air inlet duct, the annular area calculation is performed to obtain the y coordinate of the end point (3) of the first inner contraction section on the compression surface side, and the x coordinate of the end point (3) of the first inner contraction section on the compression surface side is the same as the x coordinate of the end point (10) of the first inner contraction section on the lip mask side, thereby determining the coordinate of the end point (3) of the first inner contraction section on the compression surface side.

[0075]

[0076] x3=x 10 =1895.77mm

[0077] The starting point of the first inner contraction section on the compression surface side is the end point of the outer compression surface (2), and the profile of the first inner contraction section on the compression surface side is determined by a cubic curve (here the cubic curve needs to ensure that one end is tangent to the outer compression surface and the other end is tangent to the meridian plane and the same straight segment, and the specific curve form is a cubic curve), and is tangent to the outer compression surface profile at the starting point and tangent to the horizontal line at the end point.

[0078] 4. Determine the straight section profile of the meridian plane

[0079] The meridian plane iso-straight segment is a horizontal iso-straight segment. Given the meridian plane iso-straight segment length L4=324 mm, the coordinates of the end point (4) of the meridian plane iso-straight segment on the compression surface side and the end point (11) of the meridian plane iso-straight segment on the lip mask side can be determined, and the meridian plane iso-straight segment profile can be determined.

[0080] x4=x 11 =x3+L4=2345.77mm

[0081] y4=y3=424.74mm

[0082] y 11 =y 10 =517.24mm

[0083] 5. Determine the profile of the second inner contraction section

[0084] The second inner shortening section profile approaches from the outside to the axis of the air inlet duct. To determine the second inner shortening section profile, the second inner shortening section length L5 = 1080 mm, the equal annular shrinkage ratio ICR2 = 1.75 and the meridian shrinkage ratio ICR3 = 1.24 are given. The second inner shortening section length L5 can determine the x-coordinates of the second shortening section end point (5) on the compression surface side and the second inner shortening section end point (12) on the lip mask side. Since the second inner shortening section profile approaches from the outside to the axis of the air inlet duct, when the distance H1 between point (4) and point (11) and the distance H2 between point (5) and point (12) are the same, the flow channel shrinkage already exists, and this inner shrinkage ratio is recorded as the equal annular shrinkage ratio ICR2. After ICR2 is given, the y-coordinates of the second shortening section end point (5) on the compression surface side and the second inner shortening section end point (12) on the lip mask side are preliminarily determined, recorded as y 5a and 12a .

[0085] x5=x 12 =x4+L5=3425.77mm

[0086]

[0087] After the y coordinates of the end point (5) of the second contraction section on the compression surface side and the end point (12) of the second inner contraction section on the lip mask side are preliminarily determined, if the inner contraction ratio of the second inner contraction section needs to be further adjusted, the meridian contraction ratio ICR3 needs to be given. ICR3 is defined as the inner contraction effect caused by the decrease of H2 relative to H1, which is manifested as the y coordinate of the end point (12) of the second inner contraction section on the lip mask side can be further reduced. In summary, the y coordinates of the end point (5) of the second contraction section on the compression surface side and the end point (12) of the second inner contraction section on the lip mask side can be determined by the equal annular contraction ratio ICR2 and the meridian contraction ratio ICR3.

[0088] y5=y 5a =222.89mm

[0089]

[0090] The second inner contraction section profile is generated by a cubic curve and is tangent to the upstream meridian plane straight section and the downstream expansion section curve. Thus, the second inner contraction section profile is determined.

[0091] 6. Determine the profile of the inlet expansion section

[0092] From the previous step, it can be known that the coordinates of the end point (5) of the second contraction section on the compression surface side and the end point (12) of the second inner contraction section on the lip mask side are known, and the coordinates of the end point (8) of the air inlet on the compression surface side and the end point (14) of the air inlet on the lip mask side are known. There is a tail cone in the axisymmetric air inlet, and the coordinates of the starting point (6) of the tail cone are determined by its relative position between point (5) and point (8). Specifically, with point (5) as the starting point and point (8) as the end point, the relative position percentage in the x direction a1=65.56% and the relative position percentage in the y direction a2=85% are given (given the percentage a1, an x ​​coordinate can be determined between (5) and (8), which is the x coordinate of the starting point of the tail cone, and the y coordinate can be determined by a2 in the same way), and the coordinates of the starting point (6) of the tail cone can be determined. Since the y coordinate of the end point (7) of the tail cone is 0, the relative position percentage in the x direction a3=76.8% is given, and the coordinates of the end point (7) of the tail cone can be determined.

[0093] x6=(L1-x5)·a1+x5=5900.16mm

[0094] y6=y5-y5·a2=189.46mm

[0095] x7=(L1-x5)·a3+x5=6324.38mm

[0096] Similarly, for the end point (13) of the precooler domain, its coordinates are determined by its relative position between point (8) and point (14). Since the y coordinate of the end point (13) of the precooler domain is the same as that of point (14), the coordinates of the end point (13) of the precooler domain can be determined by giving the x-direction relative position percentage a4=86.14%.

[0097] x 13 =(L1-x5)·a4+x5=6676.78mm

[0098] 7. Determine the profile of the precooler

[0099] In this design method, the precooler is configured as a multi-stage ladder. Given the number of precooler stages b, the precooler profile can be determined. Specifically, the precooler region is located between the tail cone starting point (6) and the end point (13) of the precooler region. From the previous step, the coordinates of these two points are known. After determining the number of precooler stages b = 4, each stage is evenly distributed between point (6) and point (13). There is no overlap between the stages in the y direction, and in the x direction, there is an overlap of 1 / 4 of the stage width between the stages (e.g. Figure 1 The precooler indicated by the end point (13) of the precooler domain and Figure 4 The precooler (100) has a stepped cross-section and the number of stages is b=4, and there is an overlap of 1 / 4 of the stage width between the stages).

[0100] 8. Determine the location and form of the venting seam

[0101] In order to ensure that the air inlet can work efficiently, a venting seam is generally arranged on the compression surface of the air inlet. First, determine the x-direction position of the venting seam, which is determined by its relative position between the compression surface tip (1) and the tail cone starting point (6). Given the x-direction relative position percentage a5=30%, the position of the venting seam on the compression surface of the air inlet can be determined. After the number of venting seams c=5, the venting seam width L6=6mm, the venting seam interval L7=6 and the venting cavity outlet width L8=21mm are given, the form of the venting seam can be determined.

[0102] 9. Determine the outer lip mask surface

[0103] The outer lip mask profile can be determined by giving a lip mask structural angle θ3 = 8° and an outer lip mask length L9 = 886.3 mm, wherein the outer lip mask length L9 is the x-direction distance from the outer lip mask corner point (16) to the lip mask tip point (9).

[0104] After the above steps, the specific parameters of the axisymmetric pre-cooling air inlet are finally obtained, and an initial profile is quickly provided for the pre-cooling axisymmetric air inlet, which is convenient for the subsequent performance evaluation of the air inlet.

Claims

1. A parameterized design method for an axisymmetric precooling inlet, characterized by: The axisymmetric pre-cooling type air inlet comprises a compression surface tip (1) of the air inlet, an end point of an outer compression surface (2), an end point of a first inner contraction section on the compression surface side (3), an end point of a meridian straight section on the compression surface side (4), an end point of a second contraction section on the compression surface side (5), a tail cone starting point (6), an end point of a tail cone (7), an end point of the air inlet on the compression surface side (8), a lip cover tip point (9), an end point of a first inner contraction section on the lip cover side (10), an end point of a meridian straight section on the lip cover side (11), an end point of a second inner contraction section on the lip cover side (12), an end point of a pre-cooler domain (13), an end point of an air inlet on the lip cover side (14), an air release seam starting point (15), and an outer lip cover folding angle point (16); the design method comprises the following steps: The first step is to determine the overall size of the air intake duct; Given the total length of the inlet duct L1, the inlet duct outlet radius R1, and the inlet duct capture radius R2, the compression surface cusp is taken as the coordinate origin (0,0), and the direction of the airflow without an angle of attack is the positive direction of the x-axis; the total length of the inlet duct L1 is equal to the x-axis coordinate value of the inlet duct end point (8) on the compression surface side; the inlet duct outlet radius R1 is equal to the y-direction distance between the inlet duct end point (8) on the compression surface side and the inlet duct end point (14) on the lip mask side; the inlet duct capture radius R2 is equal to the y-axis coordinate value of the lip mask cusp (9); The second step is to determine the tip position of the lip mask and the outer compression surface; Given the compression surface semi-cone angle θ1 and the shock seal Mach number Ma0, the conical shock wave is solved to determine the length L2 of the external compression surface, which is equal to the x-axis coordinate value x9 of the lip mask tip (9); and the x-axis coordinate value x2 of the end point (2) of the external compression surface is the same as the lip mask tip (9): The third step is to determine the profile of the first inner contraction section; the inner contraction section profile is composed of the first inner contraction section, the meridian plane straight section and the second inner contraction section; first determine the profile of the first inner contraction section on the lip mask side, and give the length L3 of the first inner contraction section and the lip mask angle θ2; the starting point of the first inner contraction section on the lip mask side is the lip mask tip (9), and the profile of the first inner contraction section on the lip mask side is a straight line. According to L3 and θ2, the coordinates (x) of the end point (10) of the first inner contraction section on the lip mask side are obtained. 10 ,y 10 ), which is determined by the first inner contraction section profile on the lip mask side; Next, the profile of the first inner contraction section on the compression surface side is determined, and the inner contraction ratio ICR1 of the first inner contraction section is given. For the axisymmetric air intake duct, the annular area is calculated to obtain the y coordinate of the end point (3) of the first inner contraction section on the compression surface side, and the x coordinate x3 of the end point (3) of the first inner contraction section on the compression surface side and the x coordinate x1 of the end point (10) of the first inner contraction section on the lip mask side. 10 The same, thereby the coordinates of the end point (3) of the first inner contraction section on the compression surface side are determined; The starting point of the first inner contraction section on the compression surface side is the end point of the outer compression surface (2), and the profile of the first inner contraction section on the compression surface side is determined by a cubic curve and is tangent to the profile of the outer compression surface at the starting point and tangent to the horizontal line at the end point; The fourth step is to determine the meridian plane straight segment profile; the meridian plane straight segment is a horizontal straight segment. Given the meridian plane straight segment length L4, the coordinates (x4, y4) of the end point (4) of the meridian plane straight segment on the compression side and the coordinates (x4, y4) of the end point (11) of the meridian plane straight segment on the lip mask side can be determined. 11 ,y 11 ) and determine the straight section profile of the meridian plane; Step 5: determine the second inner contraction section profile; the second inner shortening section profile approaches from the outside to the inlet duct axis; given the second inner contraction section length L5, the equal annular contraction ratio ICR2 and the meridian contraction ratio ICR3; determine the x coordinates x of the second contraction section end point (5) on the compression surface side and the second contraction section end point (12) on the lip mask side by the second inner contraction section length L5. 12 ; The distance H1 between the end point (4) of the meridian equal straight segment on the compression side and the end point (11) of the meridian equal straight segment on the lip mask side is the same as the distance H2 between the end point (5) of the second contraction segment on the compression side and the end point (12) of the second inner contraction segment on the lip mask side; after ICR2 is given, the y coordinate y of the end point (5) of the second contraction segment on the compression side is preliminarily determined 5a and the y coordinate y of the end point (12) of the second inner contraction section on the lip mask side 12a ; The internal contraction ratio of the second internal contraction segment is further adjusted, and the meridian contraction ratio ICR3 is given. ICR3 is defined as the internal contraction effect caused by the decrease of H2 relative to H1, which is manifested as the y coordinate of the end point (12) of the second internal contraction segment on the lip mask side further decreases; the y coordinate y5 of the end point (5) of the second contraction segment on the compression side and the y coordinate y of the end point (12) of the second internal contraction segment on the lip mask side are determined by the equal annular contraction ratio ICR2 and the meridian contraction ratio ICR3. 12 ; The second inner contraction section profile is generated by a cubic curve and is tangent to the upstream meridian plane straight section and the downstream expansion section curve; thus, the second inner contraction section profile is determined; The sixth step is to determine the profile of the expansion section of the air inlet duct; there is a tail cone in the axisymmetric air inlet duct, and the coordinates of the starting point (6) of the tail cone are determined by the relative position of the starting point (6) of the tail cone between the end point (5) of the second contraction section on the compression surface side and the end point (8) of the air inlet duct on the compression surface side; with the end point (5) of the second contraction section on the compression surface side as the starting point and the end point (8) of the air inlet duct on the compression surface side as the end point, the relative position percentage a1 in the x direction between the end point (5) of the second contraction section on the compression surface side and the end point (8) of the air inlet duct on the compression surface side and the relative position percentage a2 in the y direction are given to determine the coordinates (x6, y6) of the starting point (6) of the tail cone; since the y coordinate of the end point (7) of the tail cone is 0, the relative position percentage a3 in the x direction between the end point (5) of the second contraction section on the compression surface side and the end point (8) of the air inlet duct on the compression surface side is given to determine the coordinates (x7, y7) of the end point (7); The coordinates of the end point (13) of the precooler domain are determined by its relative position between the end point (8) of the air inlet duct on the compression surface side and the end point (14) of the air inlet duct on the lip mask side. The y coordinate of the end point (13) of the precooler domain is the same as the end point (14) of the air inlet duct on the lip mask side. Given the x-axis relative position percentage a4 between the end point (8) of the air inlet duct on the compression surface side and the end point (14) of the air inlet duct on the lip mask side, the x coordinate x of the end point (13) of the precooler domain is determined. 13 ; Step 7: Determine the profile of the precooler; The precooler configuration is set to a multi-stage ladder type; the precooler area is located between the tail cone starting point (6) and the precooler domain end point (13); after determining the number of precooler steps b, each stage is evenly distributed between the tail cone starting point (6) and the precooler domain end point (13); there is no overlap between the stages in the y direction, and there is an overlap of 1 / 4 of the stage width between the stages in the x direction; Step 8: Determine the location and form of the venting seam; The x-direction position of the venting seam is determined by the relative position of the venting seam between the compression surface apex (1) and the tail cone starting point (6). The relative position percentage a5 between the x-direction compression surface apex (1) and the tail cone starting point (6) is given by Determine the position of the venting seam on the compression surface of the air inlet; after the number of venting seams c, the width of the venting seams L6, the interval of the venting seams L7 and the width of the venting cavity outlet L8 are given, the form of the venting seam can be determined; The ninth step is to determine the outer lip mask profile; the outer lip mask length L9 is the x-direction distance from the outer lip mask corner point (16) to the lip mask tip point (9).

2. The design method according to claim 1, characterized in that: In the second step, L2=x9=x2=R2 / tanβ y9=R2 y2=L2*tanθ1 y9 is the y coordinate of the lip mask tip point (9).

3. The design method according to claim 1, characterized in that: In the third step, x 10 =x9+L3 <h2 style=";text-align:left;direction:ltr">y<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> = y9+L3*tan(θ1-θ2) x3=x 10 。 4. The design method according to claim 1, characterized in that: In the fourth step, x4=x 11 =x3+L4 y4=y3 and 11 =and 10 。 5. The design method according to claim 1, characterized in that: In the fifth step, x5=x 12 =x4+L5 y5=y 5a 6. The design method according to claim 1, characterized in that: In the sixth step, x6=(L1-x5)·a1+x5 y6=y5-y5·a2 x7=(L1-x5)·a3+x5 <h2 style=";text-align:left;direction:ltr">x<h2 style=";text-align:left;direction:ltr"> 13 <h2 style=";text-align:left;direction:ltr"> (L1-x5) a4+x5.

7. The design method according to claim 1 or 3, characterized in that: In the third step, the relationship between the lip mask angle θ2 and the compression surface semi-cone angle θ1 is θ2≤θ1.

8. The design method according to claim 1, characterized in that: In step 8, the flow direction of the venting seam is: 30％≤a5≤80％ The width of the vent cavity outlet is smaller than the sum of the widths of the vent slit inlets, that is, L8≤c*L6.

9. The design method according to claim 1, characterized in that: In the ninth step, the lip mask structural angle θ3 is: θ3≥6°.

10. The design method according to claim 1, characterized in that: In the third, fourth and fifth steps, the inner contraction section of the air intake duct is designed in stages, including a first inner contraction section, a straight section of the meridian plane and a second inner contraction section.

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