阅读说明：本技术 具有锯齿状唇口的超声速轴对称进气道及设计方法 (Supersonic axisymmetric air inlet with serrated lip and design method ) 是由 谢旅荣 郭金默 李晓驰 汪昆 张兵 赵有喜 于 2019-09-18 设计创作，主要内容包括：本发明公开了一种具有锯齿状唇口的超声速轴对称进气道及设计方法,该进气道是在保持原始进气道其他基本构型参数和几何特征不变的基础上,对其唇口前端构造出锯齿形切口,其中,切口沿唇口绕回转轴等间距环形阵列分布。在该锯齿状唇口作用下,低来流马赫数时,进气道易于实现自起动；高来流马赫数时,可以利用锯齿形切口将多余流量溢出,有效改善超额定状态下前体激波入射至唇口内所引起的流动分离现象。该设计方案可以有效地降低进气道自起动马赫数,提高总压恢复系数,拓宽进气道工作马赫数范围。本发明结构简单,未引入活动机构,易于实现。(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.)

1. A supersonic speed axisymmetric air inlet with a serrated lip comprises an axisymmetric air inlet main body and an air inlet lip cover arranged on the outer side of the air inlet main body, wherein the lip cover is coaxial with the air inlet main body and is also axisymmetric, and an air inlet inner channel is arranged between the air inlet main body and the air inlet lip cover; the serrated lip comprises a plurality of serrated notches, and the notches are distributed on the lip along the lip in an equidistant and continuous array.

2. The supersonic axisymmetric intake duct of claim 1, characterized in that: the serrated cut-out, together with the lips on both sides at the same distance, forms a module with 16 modules distributed over the circumference, each module occupying 22.5 °.

3. The supersonic axisymmetric intake duct of claim 1, characterized in that: the air inlet is of an axisymmetric structure with a three-stage compression conical surface, the front end of a main body of the air inlet is of an axisymmetric cone, and saw-tooth notches on a lip are uniformly distributed around a rotating shaft at equal intervals.

4. A method of designing a supersonic axisymmetric intake duct according to any of claims 1-3, characterized in that: the zigzag incision is obtained by drawing an isosceles-curved-surface-like triangle with the waist length of 13.1cm and the inner angle of 54 degrees along a revolution surface at the edge of an original inlet lip, projecting the isosceles-curved-surface-like triangle to a lower lip normal plane to obtain an isosceles-curved-surface-like triangle with the waist length of 13cm, the inner angle of 54.5 degrees and the apex angle radius R of 1cm, stretching and drawing the die in the direction of the lip cover for 70 degrees, and then performing Boolean difference calculation with the lip cover main body.

5. The design method according to claim 4, wherein: the serrated notch forms a slope surface based on an isosceles triangle by shearing a part of the lip of the original air inlet channel, and the normal vector of the cross section of the lip obtained after shearing and the normal vector of the lower lip form included angles of 25 degrees, 25 degrees and 26 degrees respectively in the left side, the right side and the top, and the included angles are smaller than the corresponding shock wave angle of the original air inlet channel under the starting Mach number.

Technical Field

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

Background

The supersonic/hypersonic aircraft flies in the atmosphere, mainly adopts a ramjet engine as power, an air inlet channel is an important part of the ramjet engine, the ramjet engine is responsible for introducing air with enough flow from the atmosphere, and the hypersonic/hypersonic aircraft also plays a role in precompressing low-pressure supersonic incoming flow, and decelerating and pressurizing to enable the flow speed of the air entering a combustion chamber to be adaptive to the flame propagation speed. 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 air inlet passage is critical to the performance improvement of the stamping engine.

The axisymmetric air inlet is a typical configuration of a ramjet engine, has the advantages of simple structure, high utilization rate of a windward side, easy manufacture, convenient carrying and launching and the like, and the lip of the conventional axisymmetric air inlet generally adopts a unit flat lip and is widely applied to missile weapons and airplanes. The supersonic/hypersonic aircraft requires that an air inlet channel has good starting characteristics, higher total pressure recovery coefficient and flow coefficient, lower resistance coefficient, anti-back pressure capability and good outlet flow field quality in a wide range of flight altitude and working Mach number, and the existing ordinary unit flat lip air inlet channel has the problem of difficult starting at the lower flight Mach number, so that the phenomenon of large-area flow separation inside the air inlet channel is caused to cause insufficient thrust of an engine and even flameout; on the other hand, under a high mach number, because the precursor shock wave is incident to the inner side of the lip, the flow separation of a boundary layer near the lip cover is easily caused, the total pressure recovery coefficient of the air inlet channel is reduced, and even the flow field of the whole air inlet channel is damaged in a serious condition. In order to widen the working Mach number range of the air inlet and improve the working performance of the air inlet, a plurality of scholars improve the lip of the air inlet by adopting a variable geometry scheme, such as scheme design of stretching and rotating the lip and the like. However, the variable geometry design scheme may increase the complexity of the air intake duct machining process and the weight and complexity of the engine to some extent, and cause problems of structural connection, sealing, cooling, control and the like, and the reliability is poor.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a supersonic axisymmetric air inlet with a serrated lip, which can reduce the self-starting Mach number of the air inlet, improve the total pressure recovery coefficient of the air inlet, improve the flow field quality and widen the working range of the air inlet.

the technical scheme is as follows: in order to achieve the purpose, the invention adopts the following technical scheme.

A supersonic speed axisymmetric air inlet with a serrated lip comprises an axisymmetric air inlet main body and an air inlet lip cover arranged on the outer side of the air inlet main body, wherein the lip cover is coaxial with the air inlet main body and is also axisymmetric, and the serrated lip is arranged at the front edge of an inner channel lip cover of the air inlet between the air inlet main body and the air inlet lip cover; the serrated lip comprises a plurality of serrated notches, and the notches are distributed on the lip along the lip in an equidistant and continuous array.

Has the advantages that: on the basis that other basic configuration parameters and geometric characteristics of the designed original air inlet are not changed, a plurality of circumferentially arranged saw-tooth-shaped notches are formed at the front end of the lip, and the air inlet is easy to self-start under the action of the lip when the incoming flow Mach number is low; when the Mach number of incoming flow is high, the saw-tooth-shaped notch can be used for overflowing redundant flow, and the flow separation phenomenon caused by the fact that precursor shock waves are incident into the lip in an over-rated state can be effectively improved. According to the design scheme, the increased overflow of the lip part can reduce the shock wave intensity of the air inlet in the process of speed reduction and diffusion, so that the total pressure recovery coefficient is effectively improved, and the total pressure loss is reduced.

Further, the saw-tooth cut and the lips on both sides of the saw-tooth cut are at the same distance to form a module, 16 modules are distributed in the whole circle, and each module occupies 22.5 degrees.

Furthermore, the air inlet channel is of an axisymmetric structure with a three-stage compression conical surface, and saw-tooth notches on the lip are uniformly distributed around the rotating shaft at equal intervals.

The invention also provides a design method of the supersonic axisymmetric air inlet channel, which comprises the following scheme:

The utility model provides a supersonic speed axisymmetric intake duct's design method, the zigzag incision is through drawing the class isosceles curved surface triangle of two waist length 13.1cm, interior angle 54 along surface of revolution at original intake duct lip edge, and the projection obtains waist length 13cm, interior angle 54.5, class isosceles plane triangle that apex angle radius R equals 1cm to lower lip cover normal plane, and through carrying out boolean arithmetic of seeking difference with the lip cover main part after drawing the drawing die 70 to the lip cover direction.

Furthermore, the saw-toothed notch forms a slope surface based on an isosceles triangle by cutting a part of the lip of the original air inlet, and included angles of 25 degrees, 25 degrees and 26 degrees are respectively formed between the normal vector of the cross section of the lip obtained after cutting and the normal vector of the lower lip at the left side, the right side and the top, and the included angles are smaller than the corresponding shock wave angle of the original air inlet under the starting Mach number.

The lip of the original air inlet channel is cut and changed on the basis of unchanged other basic configuration parameters and geometric characteristics of the original air inlet channel, a new movable mechanism is not required to be introduced, and the method is easy to realize.

Drawings

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

Fig. 1 is a three-dimensional structural view of an intake duct having a serrated lip.

FIG. 2 is a top view of the original air scoop of the present invention.

FIG. 3 is a top view of an inlet of the present invention having a serrated lip.

Fig. 4(a) is a flow field structure diagram of an arbitrary symmetric cross section of an original air inlet when the incoming flow mach number is ma 6.0.

Fig. 4(b) is a cross-sectional flow field structure diagram of an inlet having a serrated lip passing through a serrated slit when the incoming flow mach number is ma 6.0.

Detailed Description

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

The invention discloses a supersonic axisymmetric air inlet with a serrated lip, which comprises an air inlet main body 1, an air inlet lip cover 2 arranged on the outer side of the air inlet main body 1, an air inlet inner channel 4 arranged between the air inlet main body 1 and the air inlet lip cover 2 and a serrated lip 3, wherein the serrated lip 3 comprises a plurality of serrated notches 5. As shown in fig. 1 and 3, the inlet has an axisymmetric structure with three-stage compression conical surfaces, and the sawtooth cuts 5 on the lip 3 are uniformly arranged around the rotary shaft at equal intervals on the lip.

The air inlet is formed by constructing a zigzag cut 5 at the front end of the lip opening of the air inlet on the basis of keeping other basic configuration parameters and geometric characteristics unchanged after the design of the original air inlet is finished. As shown in fig. 2, the original inlet duct has an axisymmetric structure with three stages of compression cones, the three-stage half-cone angles are respectively 10 °, 7.4 ° and 12.6 °, the flight mach number is ma3.5, based on the aerodynamic relation, the wave system is designed according to the sealing, and the starting mach number is ma 3.2. The zigzag notch 5 is obtained by drawing an isosceles-curved-surface-like triangle with the waist length of 13.1cm and the inner angle of 54 degrees along a revolution surface at the edge of the original inlet lip, projecting the isosceles-curved-surface-like triangle to a lower lip normal plane to obtain an isosceles-curved-surface-like triangle with the waist length of 13cm, the inner angle of 54.5 degrees and the apex angle radius R of 1cm, stretching the triangle plane towards the lip direction, drawing the die for 70 degrees, and then performing Boolean difference calculation on the surface of the lip.

The section of the sawtooth-shaped notch 5 is a slope surface with a certain angle, the normal vector of the slope surface and the normal vector of the lower lip surface form included angles of 25 degrees, 25 degrees and 26 degrees respectively at the left side, the right side and the top, and the included angle is smaller than the corresponding shock wave angle under the starting Mach number of the original air inlet channel, so that the influence of the shock wave of the falling body generated on the three sections on the normal operation of the air inlet channel is avoided. The serrated cut 5, together with the lips on both sides at the same distance, forms a module with 16 modules distributed over the entire circumference, each module occupying 22.5 °.

Under the action of the zigzag cut 5, the starting Mach number of the air inlet channel can be effectively reduced through extra overflow at the cut in the starting process; when the flight Mach number is higher than the design Mach number, the precursor shock waves are incident into the lip cover 2 and interfere with the lower lip boundary layer to cause flow separation, and the zigzag notches uniformly distributed along the lip rotating array can enable the incident shock waves to overflow to a certain extent, and can reduce separation packets caused by shock wave/boundary layer interference. Therefore, at a low incoming flow mach number, self-starting of the intake duct is easily achieved, and at a high incoming flow mach number, the phenomenon of flow separation in the lip shroud in an over-rated state of the intake duct can be improved. On the other hand, the increased overflow of the 3 parts of the serrated lip mouth reduces the shock wave intensity of the air inlet in the process of deceleration and diffusion, thereby effectively improving the total pressure recovery coefficient and reducing the total pressure loss.

Examples of the applications

(1) The flying Mach number of the air inlet channel in the working state is designed to be Ma3.5, and the flying Mach number of the air inlet channel in the over-rated state is designed to be Ma6.0.

(2) Introduction of the scheme:

A supersonic axisymmetric air inlet with three stages of compression conical surfaces is designed, three half cone angles are respectively 10 degrees, 7.4 degrees and 12.6 degrees, when the incoming flow Mach number is Ma3.5, the throat Mach number is Ma1.58. According to the pneumatic relation, the precursor shock just meets the lip. As described above, a supersonic axisymmetric inlet with a serrated lip is obtained by shearing the inlet lip. And obtaining the starting capability, total pressure recovery coefficient and flow field comparative analysis in an over-rated state of the original air inlet and the air inlet with the serrated lip through numerical simulation.

(3) Starting capability comparison

As shown in table 1, when the incoming mach number is ma3.5, the original inlet starts at ma3.2, while the inlet with a serrated lip starts at ma2.7, the starting mach number is reduced by 15.63%. It can be seen that the starting capability of the air inlet is effectively improved and the working Mach number range of the air inlet is remarkably widened due to the change of the lip shape, namely the reduction of the lip area and the increase of the extra overflow amount at the lip part.

	Original air inlet channel	Air inlet with zigzag lip
			Self-starting Mach number	3.2	2.7

TABLE 1 auto-Start Mach number comparison of intake ports (4) Total pressure recovery coefficient comparison

As shown in table 2, when the incoming flow mach number is ma3.5, the total pressure recovery coefficient at the exit of the inlet channel with the serrated lip is increased by 2.15% compared with the total pressure recovery coefficient at the original inlet channel throat. The increased overflow of the lip part reduces the shock wave intensity of the air inlet in the process of speed reduction and diffusion, and reduces the loss caused by flow separation, thereby effectively improving the total pressure recovery coefficient and reducing the total pressure loss.

	Throat canal	An outlet
			Original air inlet channel	0.6571	0.5989
Air inlet with zigzag lip	0.6735	0.6118

TABLE 2 comparison of total pressure recovery coefficient of inlet channel (5) flow field comparison when incoming flow Mach number is Ma6.0

When the incoming flow Mach number reaches Ma6.0, the flight Mach number is higher than the design Mach number at the moment, the precursor shock wave is incident into the lip cover, and the air inlet channel is in an over-rated working state. As shown in fig. 4(a) and 4(b), the interference of the shock wave and the lower lip boundary layer causes flow separation, and the saw-toothed notches uniformly distributed along the lip rotation array can enable the incident shock wave to overflow to a certain extent, and 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 flow field quality.

In conclusion, the air inlet with the zigzag lip can reduce the self-starting Mach number of the air inlet, improve the total pressure recovery coefficient of the air inlet, improve the flow field quality and widen the working range of the air inlet, so that the design scheme is feasible.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that several deductions or substitutions can be made without departing from the spirit of the present invention, and all such deductions or substitutions should be considered as the protection scope of the present invention.