Throat offset pneumatic vectoring nozzle of small-hole jet flow
Technical Field
The invention relates to the technical field of thrust vectoring nozzles of aeroengines, in particular to a throat offset pneumatic vectoring nozzle of small-hole jet flow.
Background
The next generation of fighters requires that the aircraft have 4S capability, namely super stealth, supersonic cruise, super maneuver and super information advantage; the requirements placed on the aircraft exhaust system are therefore also greatly increased, i.e. the use of a thrust vector exhaust system that merges with the rear fuselage height becomes a necessary option.
The integration of flying and flying is the key technology and development trend of the future fighter, and the core of the integration of flying and flying is the integration of aircraft-engine pneumatics, structure integration and control integration. In terms of pneumatic integration, the rear body of an airplane flying at high speed has a complex expansion wave/shock wave system, so that shock wave boundary layers interfere with each other, and complex flow phenomena such as flow separation and the like are generated, so that the rear body resistance of the airplane is increased. Meanwhile, the thrust vectoring nozzle has large bottom resistance in a complex external flow environment of the rear body, because the external flow expands and accelerates on the outer wall surface of the convergence section and then forms shock waves due to the retardation of the tail part to form a low-pressure area, so that the pressure difference resistance is caused, and the bottleneck that the thrust vectoring nozzle is applied to the next generation of high-maneuvering high-stealth fighter is limited. Therefore, for future high-maneuverability and high-stealth aircrafts, an integrated design technology of compatibility of an engine, particularly an exhaust system and a rear body of a fuselage, which has both aerodynamic performance and stealth performance is a key technology to be broken through urgently.
The fluid thrust vectoring nozzle has the advantages of simple structure, light weight and the like, and is a research hotspot of various countries. The throat offset type pneumatic thrust vectoring nozzle is taken as a new type of pneumatic thrust vectoring nozzle, has the characteristics of simple overall structure and prominent vector performance, and is increasingly paid more attention. The traditional throat offset type pneumatic vectoring nozzle is in a double-throat form, and has a specific structure comprising a nozzle inlet, an equal straight section, a throat front convergence section, a throat, two throat front expansion convergence sections (concave cavities) and two throats. However, due to the double-throat structure of the throat offset pneumatic vectoring nozzle, a special concave cavity exists between the first throat and the second throat, and a large convergence angle exists between the highest point of the concave cavity and the outlet, so that the aircraft afterbody and the outlet section are inevitably converged, and the convergence angle is obviously larger than that of the common laval nozzle, thereby causing large afterbody resistance, and the problem of resistance reduction of the throat offset pneumatic vectoring nozzle needs to be solved urgently.
Disclosure of Invention
In view of the above, the present invention provides a throat offset pneumatic vectoring nozzle of a small-bore jet, which forms a small-bore jet by using a pressure difference between a high-pressure backflow region in a cavity and a low-pressure backflow region outside the cavity, wherein the small-bore jet changes an external backflow region structure, divides the external low-pressure backflow region into two parts, and the swirl directions of the backflow regions on two sides of the small-bore jet are opposite, so that the pressure of the low-pressure backflow region is effectively compensated, the pressure difference resistance of the outer wall surface of the nozzle is reduced, and the small-bore jet can generate a certain thrust, thereby improving the thrust coefficient of the nozzle.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a pneumatic thrust vectoring nozzle of throat skew formula of aperture efflux, includes the nozzle body, the nozzle body including link up in proper order and along nozzle body central cross-section symmetry: the nozzle comprises a nozzle inlet, an equal straight section, a throat front convergence section, a throat, two throat front expansion sections, two throat front convergence sections and two throats;
the throat comprises a throat body, a throat front expansion section, a throat front convergence section and two throats, wherein the throat, the throat front expansion section, the throat front convergence section and the two throats form a concave cavity together.
Further, L is defined as the distance from the central axis of the small jet hole to the central section of the nozzle body, H is defined as the distance from the vertex of the concave cavity to the central section of the nozzle body, and H is definedth2Half the height of the two throats, L satisfies: 0.6Hth2≤L≤0.8H。
Further, the cross-sectional shape of the fluidic orifice is at least one of: circular, square, trapezoidal or oval.
Further, when the number of the jet flow small holes arranged at the upper part and the lower part of the front convergent section of the two throats exceeds one, the orifice area of the outlet of each jet flow small hole is the same, and A is defined2nDefining n number of said fluidic apertures for the orifice area of a single said fluidic aperture outlet, said A2nSatisfies the following conditions: nA2n=A2。
Further, when the number of the jet small holes arranged at the upper part and the lower part of the front converging section of the two throats is one, the area of the hole opening of each jet small hole is the same.
Further, an installation angle theta is defined as an included angle between the central axis of the small jet hole and the central section of the nozzle body, and the installation angle theta satisfies the following conditions: theta is more than or equal to 0 and less than or equal to 30 degrees.
Furthermore, the cross section of the jet flow small hole is circular or square, and can also be a special-shaped cross section such as trapezoid, ellipse and the like.
Further, the jet orifice profile may be an equal straight, converging, diverging, or converging-diverging profile.
Further, if the jet flow small holes are straight lines, the spray pipe compensates the pressure of the external low-pressure backflow area through the jet flow small holes, and meanwhile the jet flow small holes provide certain thrust.
Furthermore, if the jet flow small hole is a contraction molded line, a condition that no backflow region occurs when the jet flow small hole flows is required, and a Wittonsiss curve can be adopted, so that the thrust provided by the jet flow small hole is increased, the capability of compensating the pressure of a low-pressure backflow region is reduced, and the resistance of a rear body is further reduced.
Further, the jet orifice may be designed as a converging-diverging laval nozzle, wherein the thrust provided by the jet orifice is further increased, but the ability to compensate for the pressure in the low pressure recirculation zone is further reduced
Further, if the small jet hole is an expansion type line, the expansion type line can have a multi-time curve, a spline curve and the like, or can be designed by using a characteristic line method. It is essentially a small diffuser, at which time the ability of the small hole to compensate for the pressure in the low pressure return region is increased and the back body resistance is further reduced.
Preferably, because the backflow zone in the cavity flows more complexly, in order to ensure stable flow in the jet flow small holes and no backflow zone, the equal-diameter flow small holes are generally selected to ensure comprehensive drag reduction and thrust increasing functions under different working conditions. Further, the number of the jet flow holes may be one or more. When the number of the jet flow small holes is multiple, the outlet area of each jet flow small hole is ensured to be equal, and the number n of the jet flow small holes and the outlet area A of the small holes are ensured to be equal2nSatisfy the relation nA2n=A2By adopting the arrangement scheme of the small holes, the area of the low-pressure area can be further reduced, the average pressure of the low-pressure area can be increased, and the pressure of the low-pressure area can be more uniformly compensated.
The invention has the beneficial effects that:
1. according to the invention, through the pressure difference between the inside and the outside of the concave cavity, the fluid in the small hole flows in a self-adaptive manner, the low-pressure area of the outer wall surface is effectively compensated, the pressure difference resistance is reduced, and external air introduction is not required.
2. The present invention may be combined with other types of line drag reduction methods, such as rounding, multiple curves, vortex generators, and the like.
Drawings
Fig. 1 is a schematic structural view of a throat offset pneumatic vectoring nozzle of an orifice jet provided in embodiment 1.
Fig. 2 is a schematic structural view of a throat offset pneumatic vectoring nozzle of an orifice jet provided in embodiment 1.
FIG. 3 is a Mach cloud of a throat offset aerodynamic vectoring nozzle for an orifice jet of example 1.
FIG. 4 is a graph of the resistance change of a throat offset aerodynamic vectoring nozzle for an orifice jet according to example 1.
FIG. 5 is a graph showing the variation of the thrust-rejection ratio of the throat offset aerodynamic vectoring nozzle of an orifice jet according to example 1.
FIG. 6 is a schematic view of a throat offset aerodynamic vectoring nozzle of an orifice jet according to embodiment 2
FIG. 7 is a Mach cloud of a throat offset aerodynamic vectoring nozzle for an orifice jet of example 2.
FIG. 8 is a graph of the resistance change of a throat offset aerodynamic vectoring nozzle for an orifice jet according to example 2.
FIG. 9 is a graph showing the variation of the thrust-rejection ratio of the throat offset aerodynamic vectoring nozzle of an orifice jet according to example 2.
FIG. 10 is a schematic view of the throat offset aerodynamic vectoring nozzle of an orifice jet according to example 3.
Wherein: 1-nozzle inlet, 2-equal straight section, 3-throat front convergent section, 4-throat, 5-two throat front expansion section, 6-two throat front convergent section, 7-two throat, 8-nozzle outer wall surface, 9-jet orifice and 10-concave cavity.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1 and 2, the present embodiment provides a throat offset pneumatic thrust vectoring nozzle of a small-bore jet, including a nozzle body, where the nozzle body includes a through hole and is symmetrical along a central section of the nozzle body: the device comprises a nozzle inlet 1, an equal straight section 2, a throat front convergence section 3, a throat 4, two throat front expansion sections 5, two throat front convergence sections 6 and two throats 7;
the first throat 4, the second throat front expansion section 5, the second throat front convergence section 6 and the second throat 7 jointly form a cavity 10, the upper part and the lower part of the second throat front convergence section 6 are respectively provided with a small jet hole 9, the central axis of the small jet hole 9 is parallel to the central section of the nozzle body, the small jet hole 9 is communicated with the cavity 10 and an external reflux area, and the cavity 10 is also communicated with the outer wall surface 8 of the nozzle, so that gas can flow out of the cavity 10 in a self-adaptive manner.
By utilizing the pressure difference of the internal and external reflux areas of the concave cavity 10, the internal part of the jet flow pore 9 forms self-adaptive flow, the jet flow in the jet flow pore 9 changes the structure of the external reflux area, the external low-pressure reflux area is divided into two parts, and the vortex directions of the reflux areas at the two sides of the jet flow are opposite. The jet orifice 8 is symmetrical along the central section of the nozzle body.
Specifically, in the present embodiment, L is defined as the distance from the central axis of the orifice 9 to the central cross-section of the nozzle body, H is defined as the distance from the vertex of the cavity 10 to the central cross-section of the nozzle body, and H is defined asth2Half the height of the two throats 7, L satisfies: 0.6Hth2L is not less than 0.8H, the height of L is limited, and the L is used for ensuring that the small jet holes 9 are positioned in the reflux zoneSo that there is sufficient pressure difference between the inlet and outlet of the jet orifice 9 to form adaptive flow.
Specifically, in this embodiment, the cross-sectional shape of the small jet hole 9 may be selected from various shapes, including: circular, square, trapezoidal, oval or profiled cross-sections. In this embodiment, the profile of the small jet hole 9 may also be a variety of profiles, which specifically include: equal straight lines, contracted lines, expanded lines or contracted and expanded lines.
More specifically, if the jet flow small holes 9 select equal straight lines, the spray pipe compensates the pressure of the external low-pressure backflow area through the jet flow small holes 9, and meanwhile, the jet flow small holes 9 provide certain thrust; if the contraction type line is selected for the jet flow small hole 9, a backflow area does not appear in the jet flow small hole 9, therefore, a Wittonsiss curve is preferably adopted, so that the thrust provided by the jet flow small hole 9 is increased, the capability of compensating the pressure of a low-pressure backflow area is reduced, and the resistance of a rear body is further reduced; if the jet orifice 9 selects to adopt a Wittonsisky curve, the jet orifice can be specifically designed as a Laval nozzle which is contracted and then expanded, at the moment, the thrust provided by the jet orifice 9 is further increased, but the capability of compensating the pressure of a low-pressure reflux area is further reduced.
If the small jet hole 9 is selected as an expansion type line, the expansion type line 9 can have a multi-time curve, a spline curve and the like, or can be designed by using a characteristic line method. It is essentially a small diffuser, at which time the ability of the small hole to compensate for the pressure in the low pressure return region is increased and the back body resistance is further reduced.
As the flow of the backflow area in the concave cavity 10 is complex, in order to ensure stable flow in the jet flow small holes 9 and no backflow area, the equal-straight small holes are generally selected to ensure the comprehensive resistance reduction and thrust augmentation functions under different working conditions.
In this embodiment, define A2A is the total orifice area of the outlet of the jet orifice 9th2Is half of the area of the two throats 7, A2Satisfies the following conditions: 0.1Ath2≤A2≤0.15Ath2. Total orifice area a for the exit of the jet orifice 92The size of the jet pipe is limited, so as to ensure that the outer wall surface 8 of the jet pipe is effectively reduced without losing excessive main flow energyAnd the low-pressure backflow area can effectively reduce drag.
Referring to fig. 3, 4 and 5, fig. 3 is a mach number cloud chart, fig. 4 is a resistance variation chart, fig. 5 is a resistance-thrust ratio variation chart, wherein the numbers 9, 10, 11 and 12 represent 4 special flight conditions, it can be seen that after the jet flow is ejected from the jet flow small hole 9, the fluid expands and accelerates outside the pipe, and the jet flow finally converges into the main flow, it can be seen that, because the reflux area is reduced by the jet flow small hole 9, the jet flow small hole 9 can obviously reduce the pressure difference resistance of the nozzle, specifically: the pressure difference resistance of the working condition 9 is reduced by 10.6 percent, the pressure difference resistance of the working condition 10 is reduced by 19.16 percent, the pressure difference resistance of the working condition 11 is reduced by 51 percent, and the pressure difference resistance of the working condition 12 is reduced by 60.99 percent. The viscous resistance does not change much under various working conditions. And examining the change rule of the rejection-push ratio (Xb/F). As can be seen from the graph, the resistance-thrust ratio of each working condition is reduced, the resistance-thrust ratio of the working condition 9 is reduced by 8.6%, the resistance-thrust ratio of the working condition 10 is reduced by 17%, the resistance-thrust ratio of the working condition 11 is reduced by 43%, and the resistance-thrust ratio of the working condition 12 is reduced by 42%. (Note: hole1 represents that both the upper and lower portions are provided with a small jet hole 9)
Example 2
Referring to fig. 6, 7, 8 and 9, the present embodiment provides a throat offset aerodynamic vectoring nozzle of an orifice jet, and the aerodynamic vectoring nozzle provided in the present embodiment differs from the aerodynamic vectoring nozzle provided in embodiment 1 in that: the upper part and the lower part of the throat front convergence section 6 are respectively provided with two jet flow small holes 9, in particular, when the number of the jet flow small holes 9 arranged on the upper part or the lower part of the throat front convergence section 6 is more than one, namely, a plurality of small hole arrangement schemes are adopted, the area of a low-pressure area can be further reduced, the average pressure of the low-pressure area is improved, the pressure of the low-pressure area is more uniformly compensated, and the total orifice area A of the outlets of the jet flow small holes 9 is noted no matter the number of the jet flow small holes 9 arranged on the upper part or the lower part is several2There remains a need to satisfy: 0.1Ath2≤A2≤0.15Ath2And the number of upper jet apertures 9 is the same as the number of lower jet apertures 9.
More specifically, in the present embodiment, the orifice area of the outlet of each jet orifice 9 is the same.
Fig. 7 is a mach number cloud chart for the aerodynamic vectoring nozzle provided in embodiment 2, fig. 8 is a resistance variation chart for the aerodynamic vectoring nozzle provided in embodiment 2, fig. 9 is a resistance-to-thrust ratio variation chart for the aerodynamic vectoring nozzle provided in embodiment 2, specifically, for the design of the dual jet orifices 9 in embodiment 2, under the condition that the total area of the jet orifices 9 is ensured to be the same as the total area of the jet orifices 9 in embodiment 1, the simulation working condition is the same as that in embodiment 1, four transonic and supersonic working conditions of working conditions 9, 10, 11 and 12 are selected, numerical simulation is performed, and the BDTN performance and the drag reduction capability of the orifice jet are analyzed.
It can be seen that the overall flow field structure of the double-orifice jet flow is similar to that of the single-orifice jet flow, and the air flow ejected by the two jet flow orifices 9 expands outside the pipe and finally converges into the main flow. Compared with single-pore jet flow, the thrust coefficient of the double-pore jet flow BDTN is reduced to some extent under the working conditions of 9 and 10, the thrust coefficients of the working conditions of 11 and 12 are almost unchanged, and the thrust resistance ratio of the jet pipe is considered, so that the diagram shows that compared with single-pore jet flow BDTN, the thrust resistance ratio of the double-pore jet flow BDTN is further reduced, compared with BDTN of a basic configuration, the thrust resistance ratio of the working condition of 9 is reduced by 10%, the thrust resistance ratio of the working condition of 10 is reduced by 26%, the thrust resistance ratio of the working condition of 11 is reduced by 51%, and the thrust resistance ratio of the working condition of 12 is reduced by 53%. (Note: hole2 stands for the representation that both the upper and lower parts are provided with two jet apertures 9)
Example 3
Referring to fig. 10, the present embodiment provides a throat offset aerodynamic vectoring nozzle for small bore jet, which differs from the aerodynamic vectoring nozzle of embodiment 1 in that: in this embodiment, an installation angle θ needs to be limited, where the installation angle θ is an included angle between the central axis of the small jet hole 9 and the central section of the nozzle body, and the installation angle θ satisfies the following requirements: theta is more than or equal to 0 and less than or equal to 30 degrees, and the aim is to form small-hole jet flows with different angles by changing the installation angle of the jet flow small holes 9, further improve the flow field structure of a low-pressure reflux area outside the jet pipe and further reduce resistance.
In conclusion, the small jet holes 9 are arranged to communicate the cavity of the spray pipe with the external backflow area, the pressure difference between the internal backflow area and the external backflow area of the cavity is utilized to form the self-adaptive small jet flow, the small jet flow can effectively compensate the pressure of the low-pressure backflow area, the pressure difference resistance of the outer wall surface of the spray pipe is reduced, the small holes can generate certain thrust, and the thrust coefficient of the spray pipe is improved. The throat offset type pneumatic vector nozzle of the small-hole jet flow, provided by the invention, can be applied to a binary double-throat nozzle, an axisymmetric double-throat nozzle and other nozzles with similar outer wall surfaces, such as a convergent nozzle and a Laval nozzle with the outer wall surface having a convergent angle.
The invention is not described in detail, but is well known to those skilled in the art.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.