An axisymmetric double-s-bend ramjet inlet and its design method

Abstract

The application discloses a shaft symmetry double-S-bend stamping engine air inlet channel, which comprises an air inlet channel center body and an air inlet channel lip cover installed outside the air inlet channel center body; an air inlet channel inner passage is arranged between the air inlet channel center body and the air inlet channel lip cover, the air inlet channel inner passage is in a double-S-bend shape and comprises an S1 section and an S2 section which are smoothly and transitionally connected, the starting point and the ending point of the center line of the S1 section and the S2 section are both tangentially horizontal, the S1 section and the S2 section have different areas and different center line change rules, and the air inlet channel throat is always located at the S2 section when the air inlet channel lip cover moves forward and backward. The air inlet channel lip cover is moved to improve the flow capture capacity of the air inlet channel under the low Mach number condition on the premise of ensuring the high-efficiency compression and stable work of the air inlet channel, the required adjusting mechanism is simple, and the air inlet channel has high realizability and operability. The air inlet channel can effectively enhance the anti-back pressure capacity, reduce the self-starting Mach number of the air inlet channel and meet the aerodynamic performance requirements of the engine on the air inlet channel under the wide-speed-range flight working condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hypersonic vehicle design, in particular to a kind of axisymmetric double S-bend ramjet inlet and its design method. BACKGROUND

[0002] Air-breathing hypersonic power system has simple structure, high specific impulse and good economy, and is one of the most ideal power system devices for hypersonic flight. As the main air flow compression component of hypersonic power device, the total pressure recovery coefficient, anti-back pressure capability and self-starting Mach number of the inlet directly affect the performance of the propulsion system. The compression capacity requirements of the engine combustion chamber to the inlet are quite different under different working conditions. The traditional engine inlet is optimized based on a single design point, which cannot meet the requirements of wide-range high-performance operation. Secondly, the starting problem of the inlet limits the size of the contraction ratio, and there is a contradiction between the inconsistent compression amount at high and low Mach numbers and the self-starting of the inlet. In addition, the flow coefficient of the inlet directly determines the thrust of the engine, and the problem of flow capture of the inlet under low Mach number conditions needs to be solved. Therefore, in order to meet the aerodynamic high-performance requirements of the inlet under wide-speed flight conditions, adjustable design of the inlet becomes inevitable.

[0003] For axisymmetric variable geometry inlets, existing adjustment schemes have many problems. For example, in the prior art, a telescopic step type center body axisymmetric adjustable inlet scheme is provided, the length of the center body of the inlet can be adjusted within a certain range, i.e. elongated at high Mach number and shortened at low Mach number, so as to adjust the compression wave system of the front cone, increase the flow coefficient at low Mach number, and the inlet has the following disadvantages: the throat area of the inlet cannot be adjusted, and the working Mach number range is narrow; for another example, in the prior art, a variable geometry inlet design scheme with axially translatable center cone is provided, the geometric model is divided into a center cone and a lip cover, the relative position of the lip cover is adjusted by moving the center cone forward and backward, and the disadvantages are as follows: when the incoming flow Mach number increases, the center cone moves backward and the throat area increases, which cannot guarantee the efficient compression requirement of the air flow; for another example, in the prior art, an axisymmetric multi-stage adjustable inlet scheme based on a center body with openable and closable slots is provided, a plurality of hinged openable and closable slots are arranged on the center body, and the center body is combined with a translation measure, so as to form a plurality of additional flow passages on the center body according to requirements, so as to meet the large flow capacity requirement of the inlet throat at low Mach number, but the overly complex adjustment mechanism makes the practical application of the adjustable inlet very difficult. SUMMARY

[0004] The present application provides an axisymmetric double S-bend ramjet inlet which meets the requirements of increasing the flow capture of the ramjet inlet and efficient compression of the air flow under low Mach number conditions.

[0005] The application also provides a design method of the axisymmetric double-S-shaped ramjet engine inlet.

[0006] Technical scheme: To solve the above problems, the application adopts an axisymmetric double-S-shaped ramjet engine inlet, which comprises an inlet center body and an inlet lip cover installed outside the inlet center body.

[0007] Further, the variation law of the area of the S1 segment perpendicular to the center line is that the area is relatively slow at the inlet and relatively fast at the outlet of the S1 segment.

[0008] Further, the variation law of the area of the S2 segment perpendicular to the center line is that the area is relatively slow at the inlet and relatively fast at the outlet of the S2 segment.

[0009] Further, the outer compression segment at the front end of the inlet center body adopts a first-order compression cone and an isentropic compression surface.

[0010] Further, the outlet of the S2 segment is connected to an inlet expansion segment, and the inlet expansion segment adopts a quintic curve spline design.

[0011] The application also adopts a design method of the axisymmetric double-S-shaped ramjet engine inlet, which comprises the following steps:

[0012] (1) The initial position of the inlet lip cover is determined according to the minimum working Mach number condition and the flow capture amount of the inlet, and the throat area of the inlet under the minimum working Mach number condition is determined according to the contraction ratio of the inlet; the S1 segment of the inlet inner passage is designed, the starting point and the ending point of the center line of the S1 segment are tangentially horizontal, the variation law is relatively fast at the front and relatively slow at the back, and the variation law of the area of the S1 segment is relatively slow at the front and relatively fast at the back; the inner surface of the S1 segment and the minimum working Mach number throat position are determined, and the outlet of the S1 segment is the minimum working Mach number throat position;

[0013] (2) move the lip cover rearward to the design state position of the inlet duct, determine the throat area of the inlet duct under the maximum working Mach number condition according to the contraction ratio of the inlet duct, design the S-bend of S2 section of the inlet duct, the tangent of the starting point and the ending point of the center line of S2 section is horizontal, and the change law adopts slow and fast equivalence, the area change law of S2 section adopts slow and fast equivalence; determine the inner surface of S2 section and the maximum working Mach number throat position according to the requirements of the throat and the Mach number of the outlet of the inlet duct;

[0014] (3) design the expansion section of the inlet duct at the rear end of S2 section by using a quintic curve spline;

[0015] (4) connect the outlet of S1 section and the inlet of S2 section, the outlet of S1 section and the inlet of S2 section are located on the same horizontal plane, and the cross-sectional areas are the same.

[0016] Further, the outer compression section of the inlet duct adopts the design form of a first-order compression cone + an isentropic compression surface. In order to simplify the adjustable mechanism, the realizability and operability are considered, and the lip cover throat integration design is adopted. The inlet duct adopts the double S-bend and lip cover throat integration design, which synchronously realizes the forward movement of the lip cover and the increase of the throat area, and meets the requirements of increasing the flow capture of the ramjet inlet duct and the efficient compression of the airflow under the low Mach number condition.

[0017] Beneficial effects: compared with the prior art, the present application has the remarkable advantages that the flow capture capacity of the inlet duct under the low Mach number condition is improved under the premise of ensuring the efficient compression and stable work of the inlet duct, the required adjusting mechanism is simple, the realizability and operability are strong, the anti-back pressure capacity of the inlet duct can be effectively enhanced, the self-starting Mach number of the inlet duct is reduced, and the aerodynamic performance requirements of the engine on the inlet duct under the wide speed domain flight working condition are met. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the axisymmetric double S-bend ramjet inlet duct of the present application.

[0019] Figure 2 It is a structural schematic diagram of the outer compression section of the inlet duct in the present application.

[0020] Figure 3 It is a structural schematic diagram of the front edge of the inlet duct center cone and the lip cover front edge in the present application; Figure 3 (a) is a structural schematic diagram of the front edge of the inlet duct center cone; Figure 3 (b) is a structural schematic diagram of the lip cover front edge.

[0021] Figure 4 It is a schematic diagram of the adjusting form of the forward and rearward movement of the lip cover in the present application.

[0022] Figure 5 It is a schematic diagram of the cross-sectional position of the double S-bend inner flow passage of the inlet duct in the present application. DETAILED DESCRIPTION

[0023] As Figure 1 shown in the embodiment, the axisymmetric double S-bend ramjet engine inlet and the design method thereof include an inlet center body, an inlet lip cover installed outside the inlet center body, and an inlet adjusting mechanism for driving the inlet lip cover to move forward and backward; an inlet inner passage is between the inlet center body and the inlet lip cover, the inlet inner passage is in a double S-bend shape, including an S1 segment and an S2 segment connected smoothly, the starting point and the ending point of the center line of the S1 segment and the S2 segment are tangential to the horizontal, the S1 segment and the S2 segment have different areas and different center line change rules, the area change rule of the S1 segment perpendicular to the center line is that the inlet and the outlet of the S1 segment are relatively sharp, the change rule of the center line of the S1 segment is that the inlet of the S1 segment is relatively sharp and the outlet is relatively slow, the area change rule of the S2 segment perpendicular to the center line is that the inlet and the outlet of the S2 segment are relatively sharp, the change rule of the center line of the S2 segment is that the inlet and the outlet of the S2 segment are relatively sharp, and the inlet throat of the inlet lip cover is always located in the S2 segment during the forward and backward movement of the inlet lip cover.

[0024] The design method includes the following parts:

[0025] 1. As Figure 2 shown, the outer compression segment 2 of the inlet adopts the design form of a first-stage compression cone + an isentropic compression surface. The design Mach number of the reference inlet is the maximum Mach number in the working range of the inlet, as Figure 3 shown, the leading edge of the center cone 1 adopts a circular arc bluntness, and the leading edge of the lip cover 3 adopts an asymmetric bluntness form.

[0026] 2. As Figure 4 shown, the adjustable inlet adopts a lip cover throat integrated adjustment design. The inlet adjusting mechanism drives the inlet lip cover 4 to move forward and backward, the forward movement of the inlet lip cover 4 is adjusted synchronously with the increase of the throat area, so as to increase the flow capture of the inlet under the premise of ensuring the efficient and stable working of the inlet, that is, the working Mach number of the inlet is reduced, the forward movement of the lip cover 4 causes the forward movement of the throat position and the increase of the throat area; on the contrary, the working Mach number of the inlet is increased, the backward movement of the lip cover 4 causes the backward movement of the throat position and the decrease of the throat area.

[0027] 3. The inner flow passage of the inlet adopts a double S-bend design. In order to meet the requirements of synchronous adjustment of the forward movement of the inlet lip cover 4 and the increase of the throat area and efficient compression of the airflow, the inner flow passage of the inlet adopts a double S-bend design, the S-bend flow passage design needs to comprehensively consider the inlet and outlet cross-sectional area, the center line change rule, and the area change rule, and the S1 segment 5 and the S2 segment 6 of the ramjet double S-bend flow passage are designed respectively. Figure 5 The sectional design diagram of the ramjet double S-bend flow passage is as follows:

[0028] (1) According to the minimum working Mach number condition, the initial position of the air inlet lip 4 is determined, and the air inlet throat area under the minimum working Mach number condition is determined. The S-bend design is adopted for the S1 section 5, and the area of the S1 section 5 is changed according to the slow-to-fast equivalent change rule, so that the flow field in the air inlet is relatively uniform. The S1 section 5 center line change rule is selected to be fast in the front and slow in the back, so that the expansion section formed by the lower contour can weaken the compression wave system generated on the lip side, thereby reducing the flow separation induced. The inner contour surface of the S1 section 5 and the minimum working Mach number throat position are determined, and the minimum working Mach number throat position is located at the outlet 9 of the S1 section of the double S-bend flow passage.

[0029] (2) The air inlet lip is moved to the maximum working Mach number condition, and the air inlet design state position is determined. At the same time, the cross section 10 is established as the inlet of the S2 section 6, and the air inlet throat area under the maximum working Mach number condition is determined. The S2 section 6 is the area from the cross section 10 to the cross section 12, and the S-bend design is adopted for the S2 section 6. The area of the S2 section 6 is changed according to the slow-to-fast equivalent change rule, so that the flow field in the air inlet is relatively uniform. The S2 section 6 is selected to have a slow-to-fast equivalent center line change rule, which can better improve the flow field quality of the air inlet, so that the total pressure recovery at the air inlet outlet is high, and the throat and outlet Mach numbers meet the requirements. The inner contour surface of the S2 section 6 and the maximum working Mach number throat position 11 are determined.

[0030] (3) The area from the cross section 12 to the cross section 13 is the air inlet expansion section 7, which is designed by using a quintic curve spline. The lower contour surfaces of the S1 section 5 and the S2 section 6 are connected, and the double S-bend flow passage design is completed.

[0031] The air inlet ramjet flow passage adopts a double S-bend design to meet the demand for efficient compression of air flow in a wide Mach number working range, and ensures that the air inlet throat is located in the S2 section 6 in the double S-bend flow passage, so that it is possible to move the adjustable form lip forward and simultaneously adjust the throat area.

[0032] The S1 section 5 and the S2 section 6 are designed respectively. The area of the S1 section 5 is changed according to the slow-to-fast equivalent change rule, so that the flow field in the air inlet is relatively uniform. The S1 section 5 center line change rule is selected to be fast in the front and slow in the back, so that the expansion section formed by the lower contour can weaken the compression wave system generated on the lip side, thereby reducing the flow separation induced. The area of the S2 section 6 is changed according to the slow-to-fast equivalent change rule, so that the flow field in the air inlet is relatively uniform. The S2 section 6 is selected to have a slow-to-fast equivalent center line change rule, which can better improve the flow field quality of the air inlet, so that the total pressure recovery at the air inlet outlet is high, and the throat and outlet Mach numbers meet the requirements.

[0033] The adjustable air inlet channel adopts the integrated design of lip cover throat. The air inlet channel adjusting mechanism adjusts the air inlet channel lip and throat at the same time through adjusting the air inlet channel lip, is based on the double S bend design of ram flow channel, adopts the integrated adjusting design of lip cover throat to ensure that the throat is always located in the S2 section 6 in the double S bend flow channel in any working condition, makes the adjusting mechanism simple, has strong realizability and operability, realizes the synchronous adjustment of the forward movement of the lip cover and the increase of the throat area, and ensures that the air inlet channel improves the flow capture capacity of the air inlet channel under the premise of high efficient compression and stable work under low Mach number condition.

Claims

1. An axisymmetric double S-bend ramjet inlet comprising an inlet center body, an inlet lip shroud mounted outside the inlet center body, and an inlet internal passage between the inlet center body and the inlet lip shroud, characterized in that, The inner passage of the air inlet channel is double S-shaped, including a smoothly connected S1 section and an S2 section, the starting point and the ending point of the center line of the S1 section and the S2 section are tangentially horizontal, the S1 section and the S2 section have different area variation laws, when the air inlet channel lip cover moves forward and backward, the throat of the air inlet channel is always located in the S2 section.

2. The axisymmetric double-S-duct ramjet inlet according to claim 1, wherein, The area variation law of the S1 section perpendicular to the center line is that the area changes from the entrance to the exit of the S1 section, and the change law of the center line of the S1 section is that the center line changes from the entrance to the exit of the S1 section.

3. The axisymmetric dual-S-duct ramjet inlet according to claim 2, wherein, The area variation law of the S2 section perpendicular to the center line is that the area changes from the entrance to the exit of the S2 section, and the change law of the center line of the S2 section is that the center line changes from the entrance to the exit of the S2 section.

4. The axisymmetric double-S-duct ramjet inlet according to claim 1, wherein, The outer compression section of the front end of the air inlet channel center body adopts a first-order compression cone + isentropic compression surface.

5. The axisymmetric double-S-duct ramjet engine inlet according to claim 1, wherein, The front edge of the center cone of the front end of the air inlet channel center body adopts a circular arc blunting.

6. The axisymmetric dual-S-duct ramjet engine inlet according to claim 1, wherein, The front edge of the air inlet channel lip cover adopts an asymmetric blunting.

7. The axisymmetric dual-S-duct ramjet engine inlet according to claim 1, wherein, The outlet of the S2 section is connected to the air inlet channel expansion section, and the air inlet channel expansion section adopts a quintic curve spline design.

8. The axisymmetric dual-S-duct ramjet engine inlet according to claim 1, wherein, It also includes an air inlet channel adjusting mechanism for driving the air inlet channel lip cover to move forward and backward.

9. A method of designing an axisymmetric double S-bend ramjet inlet, characterized in that, The axisymmetric double S-shaped stamping engine air inlet channel includes an air inlet channel center body and an air inlet channel lip cover installed on the outside of the air inlet channel center body; the air inlet channel center body and the air inlet channel lip cover are connected by an air inlet channel inner passage, and the design method includes the following steps: (1) determining the initial position of the air inlet channel lip cover according to the minimum working Mach number condition flow capture amount of the air inlet channel, determining the throat area of the air inlet channel under the minimum working Mach number condition according to the air inlet channel contraction ratio, designing the S1 section of the air inlet channel inner passage, the starting point and the ending point of the center line of the S1 section are tangentially horizontal, and the change law is that the center line changes from the entrance to the exit of the S1 section, and the area variation law of the S1 section is that the area changes from the entrance to the exit of the S1 section; determining the S1 section inner surface and the minimum working Mach number throat position, and the S1 section outlet is the minimum working Mach number throat position; (2) moving the air inlet channel lip cover to the maximum working Mach number condition air inlet channel design state position, determining the throat area of the air inlet channel under the maximum working Mach number condition according to the air inlet channel contraction ratio, designing the S2 section of the air inlet channel inner passage, the starting point and the ending point of the center line of the S2 section are tangentially horizontal, and the change law is that the center line changes from the entrance to the exit of the S2 section, and the area variation law of the S2 section is that the area changes from the entrance to the exit of the S2 section; determining the S2 section inner surface and the maximum working Mach number throat position according to the throat and the air inlet channel outlet Mach number requirements; (3) designing the air inlet channel expansion section at the rear end of the S2 section by using a quintic curve spline; (4) connecting the S1 section outlet and the S2 section inlet, the S1 section outlet and the S2 section inlet are located on the same horizontal plane, and the cross-sectional areas are the same.

10. The method of claim 9, wherein, The outer compression section of the front end of the air inlet channel center body adopts a first-order compression cone + isentropic compression surface design form.

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