CN110552786B - Supersonic axisymmetric inlet with serrated lip and design method - Google Patents

Abstract

The invention discloses a supersonic axisymmetric air inlet with a serrated lip and a design method thereof. Under the action of the zigzag lip, when the Mach number of incoming flow is low, the air inlet channel is easy to realize self-starting; when the Mach number of incoming flow is high, redundant flow can be overflowed by using the sawtooth-shaped cuts, and the flow separation phenomenon caused by the fact that precursor shock waves are incident into the lip under an over-rated state is effectively improved. The design scheme can effectively reduce the self-starting Mach number of the air inlet, improve the total pressure recovery coefficient and widen the working Mach number range of the air inlet. The invention has simple structure, does not introduce a movable mechanism and is easy to realize.

Description

Supersonic axisymmetric inlet with serrated lip and design method

technical field

The invention relates to the design field of air-breathing supersonic/hypersonic aircraft, in particular to a supersonic axisymmetric air inlet.

Background technique

The supersonic/hypersonic vehicle flies in the atmosphere, mainly using the ramjet as the power. The intake port, as an important part of the ramjet, is responsible for the task of introducing sufficient flow of air from the atmosphere for the engine, and also plays the role of bringing the low-pressure supersonic to the air. The flow is pre-compressed, and the speed of the air entering the combustion chamber is adapted to the speed of the flame. Its performance and the quality of the flow field provided have a significant impact on the performance of the engine and the entire aircraft. Therefore, the design of the intake port is very critical to the performance improvement of the ramjet.

Axisymmetric intake port is a typical configuration of ramjet, which has the advantages of simple structure, high utilization rate of windward surface, easy manufacture, easy portability and launch. Lips are widely used in missile weapons and aircraft. Supersonic/hypersonic vehicles require the intake port to have good starting characteristics, high total pressure recovery coefficient and flow coefficient, low drag coefficient, anti-backpressure capability, and good Due to the quality of the outlet flow field, the existing ordinary unit flat lip air intake will have difficulty in starting at a low flight Mach number, resulting in a large area of flow separation inside, resulting in insufficient engine thrust or even flameout; on the other hand , under high Mach number, the precursor shock wave is incident on the inside of the lip, which is easy to cause the flow separation of the boundary layer near the lip cover, resulting in the reduction of the total pressure recovery coefficient of the intake port, and even destroying the flow of the entire intake port in severe cases. field. In order to widen the working Mach number range of the intake port and improve the working performance of the intake port, many scholars have adopted a variable geometry scheme to improve the intake port lip, such as the design of expansion and rotation of the lip. However, the variable geometry design scheme will increase the complexity of the intake port processing technology and the weight and complexity of the engine to a certain extent, and at the same time cause structural connection, sealing, cooling, control and other problems, and the reliability is poor.

SUMMARY OF THE INVENTION

Purpose of the invention: The present invention provides a supersonic axisymmetric intake port with a serrated lip, which can reduce the self-starting Mach number of the intake port, improve the total pressure recovery coefficient of the intake port, improve the quality of the flow field, and widen the intake port. the scope of work.

Technical scheme: In order to achieve the above purpose of the invention, the present invention adopts the following technical scheme.

A supersonic axisymmetric air inlet with a serrated lip, comprising an axisymmetric air inlet main body, an air inlet lip cover mounted on the outside of the air inlet main body, the lip cover and the air inlet main body being coaxial and the same In order to be axially symmetrical, between the main body of the air inlet and the lip cover of the air inlet is the front edge of the lip cover of the inner channel of the air inlet is a serrated lip; Distributed in a continuous array at equal intervals along the lip on the lip.

Beneficial effect: the present invention makes a number of zigzag incisions arranged in the circumferential direction at the front end of the lip on the basis that other basic configuration parameters and geometric characteristics of the original air intake port that have been designed remain unchanged, and the lip acts on the lip When the inflow Mach number is low, the intake port is easy to realize self-start; when the inflow Mach number is high, the excess flow can be overflowed by using the zigzag incision, which can effectively improve the incidence of the precursor shock wave into the lip under the super-rated state. caused by flow separation. The design scheme can reduce the shock wave intensity of the intake port during the deceleration and diffusion process through the increased overflow at the lip, thereby effectively improving the total pressure recovery coefficient and reducing the total pressure loss.

Further, the serrated cut and the lips at the same distance on both sides together form a module, and 16 modules are distributed around the entire circumference, and each module occupies 22.5°.

Further, the intake port is an axisymmetric structure with a three-stage compression cone surface, and the sawtooth cuts on the lip are evenly spaced around the axis of rotation.

The present invention also provides a design method for the supersonic axisymmetric air inlet, including the following solutions:

A method for designing the supersonic axisymmetric air inlet, wherein the zigzag incision is made by drawing an isosceles-like triangle with two sides of 13.1 cm in length and an interior angle of 54° along the surface of revolution on the edge of the lip of the original air inlet. To the normal plane of the lower lip mask, a quasi-isosceles plane triangle with a waist length of 13cm, an internal angle of 54.5°, and a rounded vertex angle of R=1cm is obtained. After the draft is 70° in the direction of the lip mask, the Boolean difference operation is performed with the main body of the lip mask. owned.

Further, the zigzag cut forms a slope surface based on an isosceles triangle by cutting a part of the original inlet lip, and the normal vector of the lip section and the normal vector of the lower lip obtained after cutting are on the left and right sides and The three orientations at the top form an included angle of 25°, 25°, and 26°, respectively, which is smaller than the corresponding shock angle at the starting Mach number of the original intake port.

The invention is easy to implement by cutting and modifying the lip on the basis of the other basic configuration parameters and geometric characteristics of the original air inlet that has been designed and completed, without introducing a new movable mechanism.

Description of drawings

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a three-dimensional structural diagram of an air intake port with a serrated lip.

FIG. 2 is a top view of the original intake port according to the present invention.

FIG. 3 is a top view of an air inlet with a serrated lip according to the present invention.

Figure 4(a) is a flow field structure diagram of an arbitrary symmetrical section of the original intake port when the incoming Mach number is Ma6.0.

Figure 4(b) is a cross-sectional flow field structure diagram of an intake port with a serrated lip passing through a serrated cut when the incoming Mach number is Ma6.0.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figures 1 and 3 below, the present invention discloses a supersonic axisymmetric air inlet with a serrated lip, which comprises an air inlet main body 1 and an air inlet lip cover installed on the outside of the air inlet main body 1 2. The lip cover includes a serrated lip 3 . Between the main body 1 of the air inlet 1 and the lip cover 2 is an air inlet channel 4 , and the serrated lip 3 includes a plurality of serrated cuts 5 . As shown in FIG. 1 and FIG. 3 , the intake port is an axisymmetric structure with a three-stage compression conical surface, and the sawtooth notches 5 on the lip 3 are evenly spaced around the axis of rotation on the lip.

The intake port is formed by constructing a zigzag cut 5 at the front end of the lip after the design of the original intake port is completed, on the basis of keeping other basic configuration parameters and geometric characteristics unchanged. As shown in Figure 2, the original intake port is an axisymmetric structure with a three-stage compression cone, the three-stage half cone angles are 10°, 7.4°, and 12.6°, respectively, and the flight Mach number is Ma3.5. Based on the aerodynamic relationship formula, the wave system is designed according to the seal, and its starting Mach number is Ma3.2. The zigzag incision 5 draws an isosceles-like triangle with a waist length of 13.1 cm and an interior angle of 54° along the surface of revolution on the edge of the original air inlet lip, and projects it to the normal plane of the lower lip mask to obtain a waist length of 13 cm and an interior angle of 54.5. °, a quasi-isosceles plane triangle with rounded apex angle R=1cm, the triangular plane is stretched and drafted 70° in the direction of the lip mask, and then the zigzag incision 5 can be obtained by performing Boolean difference operation with the surface of the lip mask.

The cross-section of the serrated incision 5 is a sloped surface at a certain angle, and the normal vector of the sloped surface and the normal vector of the lower lip surface respectively form 25°, 25°, 26° clips at the left and right sides and the top three directions. The included angle is smaller than the corresponding shock angle at the starting Mach number of the original intake port, so as to avoid the generation of off-body shock waves on these three sections and affect the normal operation of the intake port. The serrated cut 5 and the lips at the same distance on both sides together form a module, and 16 modules are distributed over the entire circumference, and each module occupies 22.5°.

Under the action of the serrated cutout 5, the intake port can effectively reduce the starting Mach number through the additional overflow at the cutout during the starting process; when the flight Mach number is higher than the design Mach number, the precursor shock wave is incident on the lip cover 2 The boundary layer interference between the inner and lower lip causes flow separation, and the evenly distributed sawtooth notches along the lip rotary array can overflow the incident shock to a certain extent, and can reduce the separation packets caused by shock/boundary layer interference. Therefore, it is easy to realize the self-starting of the intake port under the low incoming Mach number, and the flow separation phenomenon in the lip cover of the intake port in the over-rated state can be improved under the high incoming Mach number. On the other hand, the increased overflow at the serrated lip 3 reduces the shock intensity of the intake port during the deceleration and diffusion process, thereby effectively improving the total pressure recovery coefficient and reducing the total pressure loss.

Applications

(1) The flight Mach number in the design air inlet working state is Ma3.5, and the flight Mach number in the over-rated state is Ma6.0.

(2) Program introduction:

A supersonic axisymmetric inlet with three-stage compression cone surface is designed, and the three half cone angles are 10°, 7.4°, and 12.6°, respectively. When the incoming Mach number is Ma3.5, the throat Mach number is Ma1. 58. According to the aerodynamic relationship, the precursor shock just meets the lips. As described above, a supersonic axisymmetric air inlet with a serrated lip is obtained by shearing the lip of the air inlet. Through numerical simulation, the starting capacity, total pressure recovery coefficient and the flow field in the over-rated state of the original intake port and the intake port with serrated lip are obtained.

(3) Comparison of starting ability

As shown in Table 1, when the incoming Mach number is Ma3.5, the original intake port starts at Ma3.2, while the intake port with the serrated lip starts at Ma2.7, and the starting Mach number is reduced by 15.63% . It can be seen that due to the change of the lip shape, that is, the reduction of the lip area, the additional overflow at the lip area increases, so that the starting ability of the intake port is effectively improved, and the working Mach number range of the intake port is significantly broadened.

original intake Air intake with serrated lip Self-starting Mach number 3.2 2.7

Table 1 Comparison of self-starting Mach numbers of intake ports (4) Comparison of total pressure recovery coefficients

As shown in Table 2, when the incoming Mach number is Ma3.5, the intake port with serrated lip improves the total pressure recovery coefficient at the throat of the original intake port by 2.49%, and the total pressure recovery coefficient at the outlet An increase of 2.15%. This shows that the increased overflow at the lip reduces the shock intensity of the intake port during the deceleration and diffusion process, and reduces the loss caused by flow separation, thereby effectively improving the total pressure recovery coefficient and reducing the total pressure loss.

throat Export original intake 0.6571 0.5989 Air intake with serrated lip 0.6735 0.6118

Table 2 Comparison of the total pressure recovery coefficient of the intake port (5) Comparison of the flow field when the incoming Mach number is Ma6.0

When the incoming Mach number reaches Ma6.0, the flight Mach number is higher than the design Mach number, the precursor shock wave is incident inside the lip cover, and the intake port is in an over-rated working state. As shown in Figures 4(a) and 4(b), the interference between the shock wave and the lower lip boundary layer causes flow separation, and the evenly distributed sawtooth-like cuts along the lip rotating array can overflow the incident shock wave to a certain extent, and It can reduce the separation packet caused by the shock wave/boundary layer interference, thereby improving the flow separation caused by the shock wave/boundary layer interference and improving the quality of the flow field.

To sum up, the intake port with serrated lip can reduce the self-starting Mach number of the intake port, improve the total pressure recovery coefficient of the intake port, improve the quality of the flow field, and widen the working range of the intake port. Therefore, this design The plan is feasible.

The above are only the preferred embodiments of the present invention, and it should be pointed out that some deductions or substitutions can be made without departing from the concept of the present invention, and these deductions or substitutions should be regarded as the protection scope of the present invention.

Claims (4)

1. A design method for a supersonic axisymmetric air inlet with a serrated lip, the supersonic axisymmetric air inlet comprises an axisymmetric air inlet main body, an air inlet lip cover installed on the outside of the air inlet main body, the The lip cover is coaxial with the main body of the air inlet and is also axially symmetrical, the inner channel of the air inlet is between the main body of the air inlet and the lip cover of the air inlet, and the front edge of the lip cover is a serrated lip; The lip-like lip includes a number of zigzag incisions, and the incisions are distributed in a continuous array at equal intervals along the lip; it is characterized in that: the zigzag incisions are drawn by drawing two waist lengths along the curved surface of revolution on the edge of the original air inlet lip. A quasi-isosceles triangle with a 13.1cm and an interior angle of 54° is projected onto the normal plane of the lower lip mask to obtain a quasi-isosceles plane triangle with a waist length of 13cm, an interior angle of 54.5°, and a rounded vertex angle of R=1cm. It is obtained by performing a Boolean difference operation with the lip mask body after the mold is 70°. 2. The design method according to claim 1, wherein the serrated cut forms a slope surface based on an isosceles triangle by cutting a part of the original inlet lip, and the lip cross-section method obtained after cutting The direction vector and the lower lip normal vector form an included angle of 25°, 25°, and 26° on the left and right sides and the top, respectively, which is smaller than the corresponding shock angle at the starting Mach number of the original intake port. 3 . The design method according to claim 1 , wherein the serrated cut and the lips at the same distance on both sides together form a module, and 16 modules are distributed around the entire circumference, and each module occupies 22.5°. 4 . 4. The design method according to claim 1, characterized in that: the intake port is an axisymmetric structure with a three-stage compression conical surface, the front end of the intake port main body is an axisymmetric cone, and the sawtooth cut on the lip surrounds The rotary shafts are evenly spaced and arranged.

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