Design method of internal shrinkage hypersonic inlet channel integrated with forebody
Technical Field
The invention relates to a ramjet engine, in particular to a design method of an inner contraction hypersonic inlet channel integrated with a forebody.
Background
In the hypersonic flight, because the aircraft forebody is strongly coupled with the air inlet flow field, the shape, the flow field uniformity and the boundary layer characteristics of the aircraft forebody have direct influence on the performance and the starting performance of the air inlet, and thus, the hypersonic aircraft mostly adopts the integrated design of an inner contraction air inlet and the forebody.
At present, the integrated design of an inner contraction air inlet and a front body is mainly divided into two types, one type is the inner contraction air inlet as a wave-multiplying front body, for example, a three-module and four-module Busemann air inlet is directly adopted by a 20 th century 60-year Johns Hopkins university SCRAM missile to form a circular section configuration, and a four-module inner contraction air inlet is also adopted by a scramjet engine developed in England in the United kingdom in the Hyshot plan; the other is that the forebody and the inner contraction inlet are directly integrated, such as the SR-72 hypersonic scout concept issued by Rockschid Martin company in the United states and the newly-introduced high-speed percussion weapon (HSSW) concept, which adopt the integration design of the projectile body and the inner contraction inlet, but detailed design details are not published yet; for the hypersonic flight vehicle with a long forebody and a thick boundary layer, the integral design of the forebody and the inner contraction air inlet channel is not disclosed, and a perfect solution is not provided because the former cannot be effectively applied and the latter is not disclosed.
Disclosure of Invention
The invention aims to solve the problem that the prior hypersonic aerocraft with a longer forebody and a thicker boundary layer has the defects that the integral design and manufacture of the forebody and an inner contraction air inlet channel still has no perfect solution, and provides a design method of the inner contraction hypersonic air inlet channel integrated with the forebody.
In order to solve the defects of the prior art, the invention provides the following technical solutions:
a design method of an inner contraction hypersonic inlet channel integrated with a forebody is characterized by comprising the following steps:
step (1): designing an aircraft forebody
The aircraft forebody is a revolution body or a revolution body-like structure, a generatrix of the aircraft forebody consists of a cubic curve and a flat straight line, and coefficients of the cubic curve are determined according to preset starting point coordinates, preset end point coordinates, a starting cone angle and a preset end point slope;
step (2): design of reference flow field
The reference flow field is of an axisymmetric structure and comprises an external compression flow field, an internal compression flow field and a lip reflection shock wave; the outer compression flow field comprises an outer compression conical surface and an outer compression shock wave surface positioned on the periphery of the outer compression conical surface, and an outer compression area is formed between the outer compression conical surface and the outer compression shock wave surface; the inner compression flow field comprises an inner compression conical surface and a lip cover compression surface, the lip cover compression surface is positioned at the periphery of the inner compression conical surface, the intersection point of the lip cover compression surface and the outer compression shock wave surface is a lip opening point B, an inner compression area is formed between the inner compression conical surface and the lip cover compression surface, and the lip cover compression surface generates an initial compression wave and a tail compression wave in the inner compression area; the lip reflected shock wave is positioned between the inner compression area and the outer compression area;
(2.1) obtaining flow field parameters of the aircraft forebody through numerical simulation calculation according to the inflow parameters of the aircraft forebody, and extracting the non-uniform flow field parameters at the inlet section of the air inlet channel as inflow parameters of a reference flow field;
(2.2) giving pressure distribution on the outer compression conical surface according to the inflow parameters of the reference flow field, so as to determine the outer compression conical surface and determine an outer compression shock wave surface;
(2.3) interpolating and determining a lip point B on the outer compression shock wave surface according to the capture radius of the reference flow field, and giving out pressure distribution on the lip cover compression surface so as to determine the lip cover compression surface, thereby determining a lip reflection shock wave, an initial compression wave and an end compression wave;
(2.4) determining an internal compression conical surface according to the incoming flow mass conservation principle;
and (3): determining inlet profile of inlet duct
The reference flow field and the aircraft forebody flow field are partially overlapped, the symmetry axes of the reference flow field and the aircraft forebody flow field are mutually parallel, and the inlet molded line of the air inlet channel comprises an intersecting line of the aircraft forebody and an external compression shock wave surface, a reference flow field lip molded line located at a lip point B, and two side straight lines forming a sector with the intersecting line and the reference flow field lip molded line;
and (4): determining three-dimensional aerodynamic profile of air inlet duct
Dispersing inlet molded lines of an air inlet, and tracking flow lines in a reference flow field to obtain a three-dimensional pneumatic molded surface of the air inlet, wherein the three-dimensional pneumatic molded surface of the air inlet comprises an outer compression surface of the air inlet and a lip cover compression surface of the air inlet;
and (5): and according to the matching relation between the profile of the air inlet and the front body of the aircraft, the integrated design of the air inlet and the front body of the aircraft is completed through geometric modification.
Further, in step (4), the specific step of determining the three-dimensional aerodynamic profile of the air inlet channel includes: dispersing the inlet profile of the air inlet, and slicing the sector formed by the inlet profile of the air inlet by taking the symmetry axis of the reference flow field as the center; taking the intersection point of each slice and the intersecting line as a starting point, and carrying out streamline tracing in a reference flow field to obtain an external compression surface of the air inlet; and tracking the flow line in the reference flow field by taking the intersection point of each slice and the lip-shaped line of the reference flow field as a starting point to obtain the compression surface of the inlet lip cover.
Further, in the step (5), the concrete step of completing the integrated design of the air inlet and the aircraft forebody through geometric modification according to the matching relationship between the profile of the air inlet and the aircraft forebody comprises: the smooth transition between the outer compression surface of the air inlet channel and the aircraft precursor is realized through geometric model modification on two sides, and the compression surface of the lip cover of the air inlet channel and the outlet of the air inlet channel form an air inlet channel throat diffusion section through geometric model modification smooth transition, so that the integrated design of the air inlet channel and the aircraft precursor is realized.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a design method of an internal and external cone mixed compression reference flow field based on a Bump compression surface, realizes the integrated design of a three-dimensional internal contraction air inlet channel and an aircraft forebody, realizes the automatic drainage overflow of a forebody incoming flow boundary layer on the external compression surface of the air inlet channel through a transverse pressure gradient, improves the starting capacity of the air inlet channel, widens the working range of the air inlet channel, does not need additional systems such as boundary layer channels, air discharging devices and the like, reduces the aerodynamic resistance of the aircraft, and has the remarkable characteristics of high integration degree, good performance, high volume ratio, simple structure and the like.
Drawings
FIG. 1 is a schematic structural diagram of an aircraft precursor;
FIG. 2 is a schematic diagram of a reference flow field;
FIG. 3 is a schematic view of a configuration in which the aircraft forebody partially coincides with the reference flow field;
FIG. 4 is a schematic view of inlet profile of the inlet duct;
FIG. 5 is a schematic view of an integrated internal contracting hypersonic inlet with a forebody.
The reference numerals are explained below: 1-an aircraft precursor; 2-reference flow field, 21-outer compression flow field, 211-outer compression conical surface, 212-outer compression shock wave surface, 213-outer compression area, 22-inner compression flow field, 221-inner compression conical surface, 222-lip cover compression surface, 223-inner compression area, 224-initial compression wave, 225-end compression wave, 23-lip reflection shock wave; 3-intersecting line; 4-a reference flow field lip molded line; 5-an external compression surface of the air inlet; 6-inlet lip cover compression surface; 7-boundary layer; 8-outlet of air inlet channel.
Detailed Description
The invention will be further described with reference to the drawings and exemplary embodiments.
A design method of an inner contraction hypersonic inlet channel integrated with a precursor comprises the following steps:
step (1): designing an aircraft forebody 1
Referring to fig. 1, the aircraft forebody 1 is a revolution body or revolution body-like structure, the head half-cone angle of the aircraft forebody is 15 degrees, the generatrix of the aircraft forebody is composed of a cubic curve and a flat straight line, and the coefficient of the cubic curve is determined according to the preset coordinates of a starting point and an end point, the slope of the starting cone angle and the slope of the end point;
step (2): design reference flow field 2
Referring to fig. 2, the reference flow field 2 is an axisymmetric structure, and includes an external compression flow field 21, an internal compression flow field 22, and a lip reflection shock wave 23; the outer compression flow field 21 comprises an outer compression conical surface 211 and an outer compression shock wave surface 212 positioned at the periphery of the outer compression conical surface 211, and an outer compression area 213 is formed between the outer compression conical surface 211 and the outer compression shock wave surface 212; the inner compression flow field 22 comprises an inner compression conical surface 221 and a lip cover compression surface 222, the lip cover compression surface 222 is positioned on the periphery of the inner compression conical surface 221, the intersection point of the lip cover compression surface 222 and the outer compression shock wave surface 212 is a lip opening point B, an inner compression area 223 is formed between the inner compression conical surface 221 and the lip cover compression surface 222, and the lip cover compression surface 222 generates an initial compression wave 224 and a tail compression wave 225 in the inner compression area 223; the lip reflected shock wave 23 is located between the inner compression zone 223 and the outer compression zone 213;
(2.1) obtaining flow field parameters of the aircraft forebody 1 through numerical simulation calculation according to the inflow parameters of the aircraft forebody 1, and extracting the non-uniform flow field parameters at the inlet section of the air inlet channel as inflow parameters of the reference flow field 2;
(2.2) according to the inflow parameters of the reference flow field 2, giving pressure distribution on the outer compression conical surface 211, so as to determine the outer compression conical surface 211, and thus determine the outer compression shock wave surface 212;
(2.3) interpolating and determining a lip point B on the outer compression shock wave surface 212 according to the capture radius of the reference flow field 2, giving a pressure distribution on the lip cover compression surface 222, thereby determining the lip cover compression surface 222, and thereby determining the lip reflected shock wave 23, the initial compression wave 224 and the trailing compression wave 225;
(2.4) determining the inner compression conical surface 221 according to the incoming flow mass conservation principle;
and (3): determining inlet profile of inlet duct
Referring to fig. 3 and 4, the reference flow field 2 and the flow field of the aircraft forebody 1 are partially overlapped, the symmetry axes of the reference flow field and the flow field of the aircraft forebody 1 are parallel to each other, and the inlet molded line of the air inlet channel comprises an intersecting line 3 of the aircraft forebody 1 and the external compression shock wave surface 212, a reference flow field lip molded line 4 located at a lip point B, and two side straight lines ac and nh which form a sector with the intersecting line 3 and the reference flow field lip molded line 4;
and (4): determining three-dimensional aerodynamic profile of air inlet duct
With reference to fig. 4 and 5, dispersing the inlet profile of the air inlet, and slicing the sector formed by the inlet profile of the air inlet by taking the symmetry axis of the reference flow field 2 as the center; taking the intersection point of each slice and the intersecting line 3 as a starting point, carrying out streamline tracing in the reference flow field 2, and circumferentially distributing the streamlines to obtain an external compression surface 5 of the air inlet; taking the intersection point of each slice and the reference flow field lip molded line 4 as a starting point, tracking flow lines in the reference flow field 2, and circumferentially distributing the flow lines to obtain an air inlet lip cover compression surface 6; after supersonic air flow passes through the outer compression surface 5 of the air inlet, the incoming flow boundary layer 7 is discharged to two sides on the outer compression surface 5 of the air inlet due to the action of transverse pressure gradient, the low-energy flow ratio entering the air inlet is reduced, and the performance of the air inlet is improved;
and (5): referring to fig. 5, smooth transition between the two sides of the external compression surface 5 of the inlet channel and the aircraft forebody 1 is realized through geometric modification, and the inlet channel lip compression surface 6 and the inlet channel outlet 8 form an inlet channel throat diffusion section through geometric modification smooth transition, so that the integrated design of the inlet channel and the aircraft forebody 1 is realized.
The above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and it is obvious for a person skilled in the art to modify the specific technical solutions described in the foregoing embodiments or to substitute part of the technical features, and these modifications or substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions protected by the present invention.