CN108301926B - A hypersonic convex-to-circular inwardly contracting air inlet and design method thereof - Google Patents

Abstract

The invention discloses a hypersonic convex-to-circular inner contraction air inlet channel and a design method thereof, wherein the design method comprises the following steps: the middle part of a lip plate of the convex-to-circular inlet channel is provided with an upper convex part, the shape of an inlet of the convex-to-circular inlet channel is convex, the convex part gradually shrinks towards an outlet and becomes circular, and then the convex part is connected with a circular section equal-straight isolation section with equal area; obtaining an inner conical surface with controllable compression surface Mach number, a central body with variable flow angle cross section and a reference flow field by a characteristic line method, and tracking a reverse flow line according to a circular outlet of an air inlet; the inlet is added with an upper convex part on the basis of the original rectangle and extends to the central body, and then the areas of the natural outlets traced by the streamline of the convex inlet are matched to obtain a circular outlet with the same area; and (5) carrying out streamline fitting and boundary layer correction to obtain the final convex-to-circular air inlet channel. The invention greatly improves the starting problem of the inner contraction air inlet channel by an upper convex overflow design means designed by a streamline tracing technology on the premise of ensuring the shock wave seal of a design point.

Description

A hypersonic convex-to-circular inwardly contracting air inlet and design method thereof

technical field

The invention relates to a hypersonic convex-to-circular inwardly contracting air inlet and a design method thereof, belonging to the technical field of hypersonic air inlets.

Background technique

The scramjet technology is the third revolution in the history of human aviation after the Wright brothers' aircraft and jet propulsion. This propulsion device or the combined propulsion device based on this propulsion device utilizes the intake port to compress the air to provide sufficient air and qualified flow field for the engine combustion.

The pros and cons of the performance of the hypersonic intake port are crucial to the normal operation of the scramjet and the entire aircraft. A well-designed hypersonic intake port should not only meet the requirements of light structure, high compression efficiency, low resistance, and high-quality airflow to the combustion chamber, but also require reliable starting. Once the air intake fails to start, the engine will lose thrust and even cause the aircraft to crash. Therefore, starting performance is the premise and basis for the safe and reliable operation of the hypersonic intake port and even the entire engine.

Hypersonic intake ports include two-dimensional plane compression intake ports, two-dimensional axisymmetric intake ports, and three-dimensional side pressure intake ports. Among them, the compression efficiency of the internal rotation intake port is recognized as the highest. However, at present, the internal rotation intake port is hindered from further application due to poor starting performance.

In order to solve the starting problem of the intake port, various technical solutions have been explored at home and abroad to solve the starting problem of the intake port.

(1) Geometric adjustment technology

The geometric adjustment technology can realize the starting and restarting of the intake port by changing the internal contraction ratio. The main problem is that the geometric adjustment mechanism is too complicated and bulky. Increased the dead weight of the aircraft. For hypersonic vehicles, the thermal protection and geometric sealing of the adjustment mechanism are also involved.

(2) Flow control

Flow control includes methods such as boundary layer passive removal, active blow-off, suction removal, and jet control. Among them, the blowing type flow control requires a special high-pressure air compressor and a control pipeline, and the boundary layer suction type control method loses the flow. The biggest problem with these two types of flow control is that the position of the flow control is fixed. Once the intake port is caught in the non-start, the position of the flow control may be extremely inefficient.

(3) Geometric design

The root cause of supersonic/hypersonic inlet non-start is the conflict between the incoming flow captured by the inlet and the flow capacity of the inlet throat. Therefore, through some clever designs, it can not only ensure the flow capture and compression performance of the intake port at high Mach number, but also improve the starting characteristics of the intake port on the basis of reasonable overflow. The key to this design idea is to overflow the "excess" flow that cannot be circulated in the intake port in theory, and coordinate the capture and flow capacity of the intake port scientifically and reasonably. Compared with geometrically adjustable, this method does not require any adjustment mechanism.

SUMMARY OF THE INVENTION

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a hypersonic convex-to-circular inwardly contracting air inlet and a design method thereof. The technical design of the convex overflow design method greatly improves the starting problem of the inner retracted intake port, and achieves the goal of self-starting at a lower Mach number.

Technical scheme: In order to realize the above-mentioned purpose, the technical scheme adopted in the present invention is:

A hypersonic convex-to-circular inwardly contracting air intake comprises a convex-to-circular air intake and a circular iso-straight isolation section;

Wherein, the convex-turned-round air inlet includes an air-inlet lip plate, an air-intake side plate and an air-intake top plate, and an upper convex part is arranged in the middle of the air-intake lip; The shape of the inlet of the circular air inlet is similar to a convex shape, and it shrinks to a circular shape at the outlet, and then connects with a circular and equal straight isolation section of equal area.

A method for designing a hypersonic convex-to-circular inwardly constricting intake duct, comprising: after obtaining an inner conical surface with a controllable Mach number of a compression surface, a central body configuration with a variable cross-section and a reference flow field, according to the intake duct The circular outlet conducts reverse streamline tracing; at the inlet, an upward convex part is added to the original rectangular capture surface, and extends to the center body to form a convex inlet, and then streamline tracing is performed on the convex inlet to obtain natural The outlet area is matched, and a circle of equal area is obtained as the final outlet shape; after streamline fitting and boundary layer correction, the final aerodynamic profile of the convex-to-circular intake port is obtained.

Further, the inner cone surface with controllable Mach number of the compression surface, the central body configuration and the reference flow field of the constant flow angle and variable section design are obtained by the characteristic line method. Among them, the design of the constant flow angle variable center body can make the incident shock wave hit the lip to realize the dispersion of the reflected shock wave, thereby improving the total pressure recovery caused by the shock wave loss.

Since it is an inwardly contracting air inlet directly traced in the reference flow field, the present invention can seal the incident shock wave under the design state, and the incident shock wave just hits the lip at the top of the convex part, and there is no flow coefficient. Due to the existence of the convex shape on the inlet, the effect is equivalent to the lip slotting, which increases the degree of overflow and reduces the self-starting Mach number.

Beneficial effects: Compared with the prior art, the hypersonic convex-to-circular inwardly contracting air intake provided by the present invention has the following advantages. In the design state of high Mach number, the shock wave can achieve sealing, and in the non-design state of low Mach number, the overflow degree is increased to prevent the throat from being blocked. The overflow design method reduces the self-starting Mach number of the retracted intake port, and at the same time ensures that the flow coefficient meets the requirements, and achieves the goal of solving the problem of starting the retracted intake port.

Description of drawings

1 is a schematic structural diagram of a hypersonic convex-to-circular inwardly contracting air intake of the present invention;

FIG. 2 is a front view of a hypersonic convex-turned-circular inwardly contracting air inlet of the present invention;

Fig. 3 is a top view of a hypersonic convex-turned-circular inner-shrinking air inlet of the present invention;

FIG. 4 is a side view of a hypersonic convex-turned-circular inwardly contracted air inlet of the present invention;

Fig. 5 is the left side view of the gradient reference flow field of the inlet and outlet convex-to-circular section in the present invention;

Fig. 6 is the perspective view of the gradient reference flow field of the inlet and outlet convex-to-circular section in the present invention;

The figure includes: 1. Convex-to-circular intake duct, 2. Straight isolating section of circular shape, 3. Convex inlet, 4. Circular outlet of intake duct, 5. Inlet lip plate, 6. Side plate of intake port, 7. Top plate of intake port, 8. Center body of reference flow field, 9. Section of center body at the inlet of reference flow field, 10. Section of center body at outlet of reference flow field, 11. Section of inlet of reference flow field , 12, the reference flow field outlet section, 13, the circular outlet of the isolation section, 14, the reference flow field incident shock surface, 15, the reference flow field reflection shock surface.

Detailed ways

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

As shown in Figures 1, 2, 3, and 4, it is a hypersonic convex-to-circular inner-shrinking air inlet, including a convex-to-circular air inlet 1 and a circular iso-straight isolation section 2;

Wherein, the convex-to-circular air intake 1 includes an air intake lip plate 5, an air intake side plate 6 and an air intake top plate 7, and an upper convex portion is provided in the middle of the air intake lip plate 5; The shape of the inlet of the convex-to-circular air inlet 1 is similar to that of a convex shape, and it shrinks to a circular shape toward the outlet, and then connects with a circular and equal-straight isolation section 2 of equal area.

As shown in Figures 5 and 6, it is a design method of a hypersonic convex-to-circular inwardly contracting intake port, and the intake port capturing surface is a convex shape composed of "rectangle + upper convex slot". As can be seen from FIG. 5 , the convex inlet 3 at the inlet extends to the central body 9 . The convex shape formed by "rectangle + upper convex slot" intersects with the curved shock surface of the reference flow field along the flow direction projection to obtain the convex inlet profile of the inlet including the convex inlet 3;

A series of streamline families are obtained by performing streamline tracing on the convex inlet 3, and another streamline family is obtained by performing reverse streamline tracing on the circular outlet 4 of the intake port. The transition function f(x)=x is used to re-fit the two groups of streamline families using the section gradient technique to obtain the inviscid configuration of the hypersonic inlet with a convex inlet section and a circular outlet section. Due to the existence of the boundary layer, it is necessary to correct the viscosity of the boundary layer. On the basis of the non-viscous profile, the distance of the thickness of the boundary layer is retreated outward, and finally a convex-to-circular hypersonic inlet aerodynamic profile 1 is obtained. .

Among them, the inner cone can be designed by the characteristic line method with controllable Mach number distribution along the path, and the center body can be obtained by the inverse design of equal flow angle. Through the characteristic line method, not only the inner cone and the central body configuration, but also the reference flow field results are obtained. The wall surface of the upper convex part of the convex capturing section gradually turns round along the flow direction, and finally develops into the upper arc shape of the circular outlet, realizing the gradual process of the section from convex to circular.

The shape of the convex inlet 3 and the circular outlet 4 of the air inlet is fully controllable, including the convex inlet area, the width and height of the upper convex portion, and the outlet area. These parameters can be captured according to the specific flow of the specific air intake. needs to be determined. The shape of the inlet and outlet can be flexibly adjusted according to the needs, to minimize the error caused by the gradual change of the profile, and to obtain the convex inlet and circular outlet sizes that meet the requirements. Through the ingenious design of the convex overflow window, the minimum cost of flow loss can be achieved in a wide working range, and the intake port can be reliably and safely started at low Mach number.

Because the sealing design is adopted in the design of the design point, the present invention can realize shock sealing under the design state, that is, the incident shock wave just hits the lip of the top of the convex shape, thereby ensuring the maximum air intake. Traffic capture effects at the design point. In the low Mach number non-design state, since the shock angle increases with the decrease of Mach number, the upper convex part of the convex trapping section and the intersection of the reference process shock wave (the overflow after the lip in Figures 1 and 3) The effect is equivalent to lip grooving, which reasonably overflows the excess flow that cannot pass through the intake duct throat, and achieves the effect of reducing the self-starting Mach number and improving the starting performance.

The above is only the preferred embodiment of the present invention, it should be pointed out that: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (2)

1. A hypersonic convex-to-circular inner contraction air inlet channel is characterized by comprising a convex-to-circular air inlet channel (1) and a circular equal-straight isolation section (2);

the convex-to-circular air inlet (1) comprises an air inlet lip plate (5), an air inlet side plate (6) and an air inlet top plate (7), and an upper convex part is arranged in the middle of the air inlet lip plate (5); the shape of the capture surface of the convex-to-circular air inlet (1) is convex, and the capture surface shrinks gradually to be circular towards the outlet, and then the capture surface is connected with the circular equal-straight isolation section (2) with equal area.

2. The method for designing a hypersonic convex-to-circular inner contraction inlet according to claim 1, wherein the integrated matching design of the inner contraction inlet and the convex overflow window specifically comprises: after an inner conical surface with controllable compression surface Mach number, a central body structure with a variable cross section and a reference flow field are obtained by a characteristic line method, reverse streamline tracing is carried out according to a circular outlet (4) of an air inlet; the inlet is added with an upper convex part on the basis of the rectangular capture surface and extends to the central body to form a convex inlet (3), and then the convex inlet (3) is subjected to streamline tracing to obtain the natural outlet area for matching, so that a circle with the same area is obtained and used as the final outlet shape; and (3) obtaining the final convex-to-circular pneumatic profile of the air inlet channel (1) after streamline fitting and boundary layer correction.

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