Wide-area self-starting internal contraction air inlet channel reverse design method based on bending shock waves

Abstract

The invention discloses an inverse design method for a wide-area self-starting inward-contraction air inlet channel based on bending shock waves, and relates to design of air inlet channels of hypersonic flight vehicles. On the basis of the bending shock wave theory and the double-design-point concept, the total shrinkage ratio is used as the constraint, a wall face generatrix is defined through a segmented Bezier curve, and a basic flow field meeting the low-Mach-number self-starting and high / low-Mach-number flow requirements is constructed by adjusting control point parameters of the Bezier curve; dispersing the inlet shape into a plurality of osculating planes by applying an osculating theory, and constructing a primary-secondary basic flow field group (a primary flow field is a plane flow field with the maximum curvature radius, and a secondary flow field is generated through streamline tracking of the primary flow field) in each plane; the upper wall face and the lower wall face of the air inlet are formed by circumferentially splicing the wall face generatrix, the side wall face is generated through streamline tracking, and the three-dimensional internal contraction air inlet compression molded face is obtained. The controllable design of the wide-range self-starting capacity of the air inlet channel is achieved, high compression efficiency and wide-speed-range stability are both considered, and the wide-speed-range self-starting air inlet channel is suitable for the wide-speed-range flight requirement of a hypersonic aircraft.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hypersonic vehicle inlet design, in particular to a wide-range self-starting internal contraction inlet reverse design method based on curved shock wave combining controllable flow field design method and tangent theory of high and low Mach number design points, which is especially suitable for wide-speed range flight requirements of hypersonic vehicles. BACKGROUND

[0002] As the core aerodynamic component of air-breathing propulsion system, hypersonic inlet plays a key role in reducing the speed of the incoming air and increasing the pressure, and its performance directly determines the combustion efficiency and thrust output of the engine. With the widening of the flight speed range, the inlet configuration has developed from the initial Pitot-drag configuration and axisymmetric configuration for subsonic and transonic flight design to the two-dimensional configuration suitable for supersonic and hypersonic flight, and further to the three-dimensional internal contraction configuration. Among them, the three-dimensional internal contraction inlet has the advantages of strong flow capture capacity, high compression efficiency, and small frontal area, and is widely recognized and applied in the field of hypersonic wide-range flight.

[0003] During the wide-speed range operation of a hypersonic vehicle, the inlet needs to meet two core requirements: first, it needs to achieve stable operation in a wide speed range and maintain sufficient flow capture capacity; second, it needs to efficiently compress the incoming flow to meet the engine operation requirements. However, the high flow compression capacity and the wide-range starting capacity are conflicting requirements for the inlet, and excessive compression capacity can lead to the inlet not starting at low Mach number conditions. This contradiction is particularly prominent in three-dimensional internal contraction inlets facing wide-range flight requirements.

[0004] Starting capacity analysis is usually based on Kantrowitz limit and isentropic limit. Van extended these theories to inlet starting analysis, using the inner contraction Mach number (Ma-inner) and internal contraction ratio (ICR) to evaluate the starting state of the inlet. At the same time, Van's research shows that the Kantrowitz limit is conservative: the inlet can start self-starting at a lower Kantrowitz limit [Van Wie, D., F. Kwok, and R. Walsh. "Starting characteristics of supersonic inlets." 32nd joint propulsion conference and exhibit . 1996]. Therefore, Sun fitted a self-starting boundary based on wind tunnel test data of internal contraction inlets and proposed a more valuable self-starting boundary [Sun, Bo, and Kun-yuan Zhang. "Empirical equation for self-starting limit of supersonic inlets."Journal of Propulsion and Power 26.4 (2010): 874-875].

[0005] It can be found that although domestic and foreign scholars carry out theoretical research on starting and self-starting, the combination of these theoretical work and design method is less, the main reason is that the traditional design method is based on single working condition to carry out the design of the inlet, which cannot obtain and control the low Mach number performance in the design stage, resulting in that it cannot obtain the aerodynamic characteristics of other flight conditions, thereby leading to that these methods cannot design and control the wide range starting ability of the inlet. The double design point counter design concept inversely constructs the basic flow field based on the flow demand of high and low Mach number, so that the inlet has controllable performance in a wide Mach number range, effectively matches the wide range working characteristic demand and realizes the controllable design of starting ability. Therefore, the double design point concept is applied to the wide range self-starting basic flow field counter design, and the three-dimensional inlet compression profile is generated based on the tangent theory, so as to realize the counter design of the wide range self-starting internal contraction inlet. SUMMARY

[0006] The purpose of the present application is to solve the problems of the existing internal contraction inlet, such as difficulty in self-starting in a wide range of Mach number, poor high / low Mach number flow matching, and inability to realize controllable design of wide range self-starting ability of the inlet, and to provide a wide range self-starting internal contraction inlet counter design method based on curved shock wave.

[0007] To achieve the above-mentioned purpose of the application, the present application provides the following technical solutions.

[0008] The present application constructs a wide range self-starting basic flow field based on curved shock wave theory and double design point concept, which can realize low Mach number self-starting of the basic flow field; and applies the tangent theory to construct a sub-mother basic flow field group in a series of tangent planes according to the high / low Mach number flow demand, so as to obtain a three-dimensional internal contraction inlet compression profile of wide range self-starting. The following core parameters and characteristics are involved in the design process: high / low Mach number incoming flow conditions of the internal contraction inlet, center body height of the high / low Mach number basic flow field, internal contraction ratio (ICR), internal contraction cross section Mach number (Ma-inner), target flow coefficient of low Mach number ( ), high Mach number incident shock wave shape, and expected total contraction ratio (CR).

[0009] The wide range self-starting internal contraction inlet counter design method based on curved shock wave provided by the present application comprises the following steps:

[0010] 1) Design a wide range self-starting basic flow field, under the constraint condition of a given total contraction ratio CR (in the range of 4-6), based on the high Mach number incident shock wave shape, apply the curved characteristic line method to calculate the flow field region determined by the high Mach number incident shock wave, and obtain the corresponding wall mother line; the wall mother line is used as the first wall mother line of the basic flow field;

[0011] 2) According to the given low Mach number flow condition and the first section wall surface generatrix generated in step 1), obtain the corresponding low Mach number flow field; according to the initial low Mach number capture flow coefficient, generate the first section lip line in the low Mach number flow field region by the stream line tracking method;

[0012] 3) Define the second section wall surface generatrix by Bezier curve, obtain the high Mach number flow field region corresponding to the second section wall surface generatrix by the curved characteristic line method, solve the low Mach number flow field region corresponding to the second section wall surface generatrix based on the low Mach number flow field region in step 2), obtain the second section lip line in the low Mach number flow field region by the stream line tracking method, and take the distance between the second section lip line and the lip point of the parent flow field as the convergence criterion to iteratively adjust the control points of the defined Bezier curve until the flow coefficient reaches the target flow coefficient ; At the same time, determine the inner contraction section Mach number Ma-inner and the inner contraction ratio ICR corresponding to the total contraction ratio CR;

[0013] 4) Define the third section wall surface generatrix by Bezier curve, solve the high Mach number flow field region corresponding to the three section wall surface generatrix, and make the reflected shock wave of the high Mach number design point intersect with the third section wall surface generatrix at the throat under the constraint condition that the following wall surface generatrix is a horizontal straight line, and iteratively adjust the control points of the Bezier curve until the error of the inner contraction ratio and the ICR in step 3) meets the accuracy requirement;

[0014] 5) Construct a starting state point composed of the current Ma-inner of the inlet and 1 / ICR, compare the starting state point with the self-starting boundary, if the point is located inside the self-starting boundary, it is determined that the self-starting requirement is met; otherwise, return to adjust the design parameters;

[0015] 6) Repeat steps 3) to 5) for the second section wall surface generatrix and the third section wall surface generatrix until the basic flow field meets the CR requirement and the self-starting requirement at the same time; at this time, the foregoing first section wall surface generatrix, second section wall surface generatrix, third section wall surface generatrix and lower wall surface generatrix constitute a complete wide-range self-starting basic flow field;

[0016] 7) Constructing the parent-child basic flow field group by using the theory of the tangent ogive; the upper wall surface profile of the inlet shape with continuously changing curvature, the lower wall surface profile of the inlet shape and the two side wall surface profiles are given; the upper surface curve of the inlet shape is discretized, the curvature center of each discrete point is determined, and each discrete point is taken as the origin of the local coordinate system, the local inlet curvature radius is taken as the height of the incident shock wave and the flow direction is taken as the coordinate axis, and the tangent plane corresponding to each discrete point is constructed; the curvature radius of each discrete point is dimensionless according to the maximum curvature radius value corresponding to the inlet shape, and after dimensionless, the maximum curvature radius R of the parent flow field is 1, and the remaining tangent planes are the dimensionless curvature radius R of the child flow field i ∈[0, 1];

[0017] 8) After a series of dimensionless tangent planes are obtained, the curvature center of each discrete point is taken as the origin of the local coordinate system, and the local inlet curvature radius (the maximum dimensionless curvature radius R of the parent flow field and the dimensionless curvature radius R of the child flow field i ) is taken as the height of the incident shock wave, and the child and parent basic flow fields are constructed respectively; wherein the basic flow field constructed in the tangent plane corresponding to the maximum dimensionless curvature radius R of the parent flow field is the parent basic flow field, and the height of the leading point of the incident shock wave is the dimensionless curvature radius R of the basic flow field of the child flow field i ;

[0018] 9) The height of the center body in the local tangent plane is determined according to the radius of the lower leading point in the local tangent plane of the inlet shape;

[0019] 10) The parent basic flow field is designed by the above-mentioned wide-range self-starting basic flow field design method, the first wall generatrix of the child basic flow field is obtained by streamline tracing in the parent basic flow field, so that the shape of the incident shock wave generated is consistent with the shape of the incident shock wave in the same radius range of the parent basic flow field, the second wall generatrix, the third wall generatrix and the lower wall are obtained according to the method of steps 3) to 6); at this time, the parent-child basic flow field group is constructed;

[0020] 11) Wide-range self-starting internal contraction inlet is designed; the side wall of the inlet is obtained by the streamline tracing method in the non-tangent region, and the wall generatrix of each tangent basic flow field is circumferentially spliced to obtain the basic compression profile of the wide-range self-starting three-dimensional internal contraction inlet; at this time, the wide-range self-starting internal contraction inlet is designed.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] The method of the application combines the double design point concept of high and low Mach number flow field performance and the self-starting ability of internal contraction inlet, and ensures the self-starting ability of the inlet at a low Mach number working condition by changing the internal and external compression strength of the inlet with a total contraction ratio as a constraint; the inlet shape is discretized into a plurality of points to construct a tangent plane, a self-starting basic flow field is designed in the plurality of tangent planes, wide-range self-starting three-dimensional internal contraction inlet counter design is carried out in different tangent planes according to the high / low Mach number flow demand, and the wide-range adaptability of the three-dimensional configuration is improved; the Bezier curve is iteratively optimized to balance the smoothness of the profile and the flow field performance, the design process is quantifiable and controllable, and the engineering practicability is strong. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The theoretical analysis curve diagram of the self-starting ability of the internal contraction inlet of an embodiment of the application.

[0024] Figure 2 The principle diagram of the wide-range self-starting basic flow field of the application.

[0025] Figure 3 The first part structure schematic diagram of the wide-range self-starting basic flow field of the application.

[0026] Figure 4 The second part structure schematic diagram of the wide-range self-starting basic flow field of the application.

[0027] Figure 5 The third part structure schematic diagram of the wide-range self-starting basic flow field of the application.

[0028] Figure 6 The schematic diagram of the wide-range three-dimensional internal contraction inlet shape curve of the application.

[0029] Figure 7 The wide-range self-starting tangent sub-basic flow field structure schematic diagram of the application.

[0030] Figure 8 The three-dimensional internal contraction inlet basic compression profile schematic diagram of the application obtained according to the wide-range self-starting basic flow field.

[0031] Figure 9 The self-starting process schematic diagram of the inlet. Wherein, (a) is the flow field at Ma3.8; (b) is the flow field at Ma3.9; (c) is the flow field at Ma4.0; (d) is the flow field at Ma4.1; (e) is the flow field at Ma4.2; (f) is the flow field at Ma4.3; (g) is the flow field at Ma4.4; (h) is the flow field at Ma4.5.

[0032] Figure 10 The flow characteristic schematic diagram of the inlet at a low Mach number design point.

[0033] The meanings of the various marks in the figures are as follows: 1 represents the start region of the theoretical analysis curve of the start ability of the inwardly converging inlet channel, 2 represents the non-start region, 3 represents the double solution region of the theoretical analysis curve of the start ability of the inwardly converging inlet channel, 4 represents the Isentropic curve, 5 represents the Kantrowitz limit curve, 6 represents the self-start boundary, 7 represents the double design points, 8 represents the low Mach number center body height, 9 represents the high Mach number center body height, 10 represents the parent flow field lip point, 11 represents the high Mach number incoming flow, 12 represents the high Mach number incident shock wave, 13 represents the wall generatrix determined by the high Mach number incident shock wave, 14 represents the flow field region determined by the high Mach number incident shock wave, 15 represents the low Mach number incoming flow, 16 represents the low Mach number incident shock wave, 17 represents the flow field region determined by the low Mach number incident shock wave, 18 represents the lip streamline determined by the low Mach number incident shock wave, 19 represents the second section wall generatrix, 20 represents the high Mach number flow field region corresponding to the second section wall generatrix, 21 represents the low Mach number flow field region corresponding to the second section wall generatrix, 22 represents the second section lip streamline determined by the second section wall generatrix, 23 represents the wall generatrix determined by the self-start flow field, 24 represents the height of the inwardly converging section, 25 represents the expected total contraction ratio, 26 represents the parent basic flow field high Mach number reflected shock wave, 27 represents the third section wall generatrix constructed by a Bezier curve, 28 represents the flow field region determined by the parent basic flow field high Mach number reflected shock wave 26, 29 represents the inlet channel throat height, 30 represents the post-wave flow field region determined by the parent basic flow field high Mach number reflected shock wave 26, 31 represents the lower wall generatrix of the wide-range self-start basic flow field, 32 represents the upper wall profile of the entry shape with continuously changing curvature, 33 represents the lower wall profile of the entry shape, 34 represents the side wall profile of the entry shape, 35 represents the curvature center of the tangent plane, 36 represents the curvature radius R of the parent basic flow field, 37 represents the curvature radius R of the sub-basic flow field i , 38 represents the center body height of the tangent basic flow field, 39 represents the non-tangent region of the inlet channel side wall generated by the streamline tracing method, 40 represents the sub-basic flow field high Mach number incident shock wave, 41 represents the sub-basic flow field wall generatrix, 42 represents the sub-basic flow field low Mach number incident shock wave, 43 represents the flow field region determined by the sub-basic flow field low Mach number incident shock wave, 44 represents the starting coordinate point of the lip streamline in the sub-basic flow field, 45 represents the lip streamline of the sub-basic flow field, 46 represents the lip point of the sub-basic flow field, 47 represents the sub-basic flow field high Mach number reflected shock wave, 48 represents the flow field region determined by the sub-basic flow field high Mach number reflected shock wave, 49 represents the lower wall generatrix of the sub-basic flow field, 50 represents the side wall of the three-dimensional inwardly converging inlet channel generated by the streamline tracing, and 51 represents the basic compression profile of the three-dimensional inwardly converging inlet channel. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application more clear, the following embodiments will be further described in combination with the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0035] As shown in Figure 1 , in the Ma-inner-1 / ICR coordinate system, the Isentropic curve 4 divides the coordinate system into a start region 1 of the inner convergent inlet duct start capability theoretical analysis curve and a non-start region 2, and there is a double solution region 3 between the start region 1 and the non-start region 2 (whether the inlet duct in the region starts or not is related to its pre-state, in other words, the inlet duct in the region has start capability, but not necessarily has self-start capability); the double design point 7 is located between the Kantrowitz limit curve 5 and the self-start boundary 6, so as to ensure that the design point working condition meets the self-start.

[0036] As shown in Figures 2-5 , the inverse design method of the wide-range self-start basic flow field includes the following steps:

[0037] 1) As shown in Figure 2 , the high Mach number input conditions (high Mach number center body height 9, high Mach number incoming flow 11, high Mach number incident shock wave 12, and expected total contraction ratio 25) and the low Mach number input conditions (low Mach number center body height 8, low Mach number incoming flow 15, low Mach number incident shock wave 16, and initial low Mach number capture flow coefficient) are given.

[0038] 2) As shown in Figure 3 , under the constraint condition of the expected total contraction ratio 25 (CR), the curved characteristic line method is applied to the high Mach number incident shock wave 12 as the initial boundary condition, the compatibility equation is solved along the normal direction of the shock wave, and the flow field region 14 determined by the high Mach number incident shock wave (including the spatial distribution of parameters such as pressure, Mach number and flow angle) is gradually calculated. Based on the parameter distribution of the flow field, the wall generatrix 13 determined by the high Mach number incident shock wave is generated (i.e. the first segment wall generatrix of the basic flow field).

[0039] 3) The flow field region 17 determined by the low Mach number incident shock wave is calculated according to the low Mach number incoming flow 15 condition and the wall generatrix 13 determined by the high Mach number incident shock wave, and the lip streamline 18 determined by the low Mach number incident shock wave is obtained by streamline tracing according to the starting point position of the lip streamline corresponding to the low Mach number capture flow coefficient. The downstream end point of the lip streamline 18 points to the lip point 10 of the parent flow field, and the lip point 10 of the parent flow field is the physical end point of the inlet lip and is located at the most front end of the inlet contour.

[0040] 4) As shown in Figure 4As shown, the second wall generatrix 19 is constructed using the Bezier curve, and the high Mach number flow field region 20 corresponding to the second wall generatrix is ​​calculated using the bending characteristic line method. Based on the second wall generatrix 19 and the flow field region 17 determined by the low Mach number incident shock wave, the low Mach number flow field region 21 corresponding to the second wall generatrix is ​​solved using the principle of flow field superposition. The shape of the second wall generatrix 19 is adjusted by controlling the Bezier curve, changing the position of the second lip line 22 determined by the second wall generatrix intersecting the horizontal line corresponding to the height 9 of the high Mach number center body, thereby changing the height 24 of the inner contraction section. The distance between the second lip line 22 and the lip point 10 of the parent flow field is used as the convergence criterion until the target flow coefficient is met. The expected shrinkage ratio and Ma-inner were calculated with the expected total shrinkage ratio of 25 (CR) as a constraint.

[0041] 5) such as Figure 5 As shown, the third wall generatrix 27 constructed by the Bezier curve is used to calculate the flow field region 28 determined by the high Mach number reflected shock wave 26 of the parent basic flow field using the bending characteristic line method. The Bezier curve control points are iteratively adjusted to change the shape of the third wall generatrix 27 constructed by the Bezier curve, resulting in different ICR values, until the design point determined by Ma-inner and 1 / ICR is located at... Figure 1 Above the self-starting boundary 6, the self-starting criterion is satisfied. The self-starting boundary 6 can be expressed as follows:

[0042]

[0043] In the formula, Ma is Ma-inner.

[0044] 6) Iterate the Bezier curves of the second wall generatrix 19 and the third wall generatrix 27 constructed from the Bezier curves until the error between the internal contraction ratio and the expected internal contraction ratio in step 4) meets the accuracy requirement (≤0.03). Apply the bending characteristic line method to obtain the flow field region 28 determined by the high Mach number reflected shock wave 26 of the parent basic flow field. Calculate the backflow field region 30 determined by the high Mach number reflected shock wave 26 of the parent basic flow field based on the aerodynamic parameters of the flow field region 28. Combined with the inlet throat height 29, obtain the lower wall generatrix 31 of the wide-area self-starting basic flow field through the logic of "flow field parameters at the throat → lower wall tangent direction → lower wall profile".

[0045] At this point, the construction of the basic flow field for wide-area self-starting is complete.

[0046] Subsequently, the shape of the wide-range self-starting internal contraction air intake and the design of the cutting plane were carried out. The specific design steps are as follows:

[0047] 1) such as Figure 6As shown, given the continuously varying curvature of the inlet shape's upper wall profile 32, lower wall profile 33, and two side wall profiles 34, the continuously varying curvature of the inlet shape's upper wall profile 32 is discretized (the discretization interval is 1 / 20 to 1 / 30 of the total profile length to ensure curvature calculation accuracy). The curvature center 35 of the tangent plane at each discrete point is determined. The curvature center 35 of the tangent plane at each discrete point, and the curvature radius R of the sub-basic flow field are then used to determine the curvature. i 37 and the direction of the incoming flow (consistent with the direction of the high Mach number incoming flow 11) form a cutting plane.

[0048] 2) Taking the curvature center 35 of the tangent plane at each discrete point as the origin of the local coordinate system, and the local inlet curvature radius (the mother basic flow field corresponds to the mother basic flow field curvature radius R36, and the child basic flow field corresponds to the child basic flow field curvature radius R) i 37) Given the incident shock wave height, construct the primary and secondary flow fields; where the primary flow field constructed within the tangent plane of the maximum curvature radius R36 of the primary flow field is the primary flow field, and the secondary flow field constructed within the tangent plane of the maximum curvature radius R36 of the primary flow field is the primary flow field. i The fundamental flow field constructed within the tangent plane corresponding to point 37 is the sub-fundamental flow field. The radius of curvature R of the sub-fundamental flow field at each discrete point... i 37 intersects with the lower wall profile 33 of the inlet shape, and the distance from the intersection point to the curvature center 35 of the kissing plane is the central body height 38 of each kissing basic flow field.

[0049] 3) such as Figure 7 As shown, among several kissing planes obtained by introducing the kissing theory, given the high Mach number incident shock wave shape 12 of the parent fundamental flow field with an incident shock wave leading edge height of R=1, a portion of the high Mach number incident shock wave at the corresponding dimensionless maximum curvature radius R of the parent flow field is taken as the dimensionless sub-fundamental flow field curvature radius R. i The incident shock wave 40 in the parent fundamental flow field is analyzed using the streamline tracing method (tracing the shock wave in the parent fundamental flow field that is related to R). i The corresponding streamlines) are used to obtain the first segment of the wall generatrix of the sub-basic flow field (i.e., the sub-basic flow field wall generatrix 41).

[0050] 4) At the radius of curvature R of the sub-basic flow field i Within the tangent plane corresponding to 37, taking the shape 42 of the low Mach number incident shock wave of the sub-basic flow field as the initial boundary, the flow field region 43 determined by the low Mach number incident shock wave of the sub-basic flow field and the generatrix of the low Mach number wall tangent to the basic flow field are calculated using the bending characteristic line method. Based on the flow field region 43 determined by the low Mach number incident shock wave of the sub-basic flow field and the given low Mach number flow capture coefficient ( ) Determine the coordinate of the starting point of the lip line 44 in the local kisser basic flow field, and obtain the lip line 45 of the partial sub-basic flow field by the stream line tracing method in the flow field area 43. The downstream endpoint of the lip line 45 of the sub-basic flow field coincides with the sub-basic flow field lip point 46, which is used as a convergence auxiliary criterion for the sub-flow field lip line. The sub-basic flow field lip point 46 is the physical endpoint of the sub-flow field lip, which maintains the same coaxial position as the parent flow field lip point 10 in the circumferential direction. Similarly, the Bezier curve control points are iteratively adjusted to change the shape of the sub-basic flow field wall generatrix 41, thereby changing the lip line 45 of the sub-basic flow field and the internal contraction cross-sectional height of the sub-basic flow field, until the flow coefficient requirement is met.

[0051] 5) Apply the inverse design wide-range self-starting basic flow field step 6) to solve the flow field area 48 determined by the high Mach number reflected shock wave 47, and finally obtain the lower wall generatrix 49 of the sub-basic flow field.

[0052] At this point, the wide-range self-starting internal contraction inlet shape division and kisser plane design are completed.

[0053] Next, the flow field can be applied to the design of a wide-range self-starting internal contraction inlet, as shown in Figure 8 The specific steps of the wide-range self-starting internal contraction inlet design are as follows:

[0054] 1) The curvature-continuously-varying upper wall surface profile 32 of the inlet shape is fitted to the outer contour of the parent basic flow field (composed of the wall generatrix 13 determined by the high Mach number incident shock wave, the second segment wall generatrix 19, and the third segment wall generatrix 27 constructed by the Bezier curve), the lower wall surface profile 33 of the inlet shape is fitted to the high Mach number central body contour, and three-dimensional stream line tracing is performed along the stream line direction of the sub-parent basic flow field in the non-kisser area 39 of the inlet side wall generated by the stream line tracing method, generating the side wall 50 of the three-dimensional internal contraction inlet generated by stream line tracing, which ensures smooth connection of the side wall with the upper and lower wall surface profiles (the curvature is continuous at the connection point to avoid airflow separation).

[0055] 2) The wall generatrix 13 of several kisser planes on the inlet shape curve, determined by the high Mach number incident shock wave and the wall generatrix 23 determined by the self-starting flow field, are circumferentially spliced to form the basic compression surface 51 of the wide-range dual-design-point three-dimensional internal contraction inlet. At this point, the wide-range self-starting internal contraction inlet design is completed.

[0056] To verify the technical effect of the present application, the following simulation experiment is performed:

[0057] The self-starting process includes two stages: in the first stage, the bubble enters the internal contraction section at a Mach number of 3.9, and the mass flow rate is recovered; in the second stage, the bubble is stabilized at the throat at a Mach number of 4.5, and the total pressure recovery is realized.

[0058] Figure 9 A schematic diagram of the self-starting process of the inlet is shown. In order to determine the self-starting critical Mach number, the inlet Mach number is gradually increased. Figure 9 (a) in FIG. 1 is Ma3.8: unstarted state, large shock wave boundary layer interference (Large SWBLI) dominates the internal contraction section; this separation phenomenon also induces a separation zone on the lower surface, which weakens the mass flow capture capability. With the increase of the Mach number, the flow structure changes slightly: both separation zones are reduced and migrate to the throat. Figure 9 (b) in FIG. 1 is Ma3.9: the flow structure starts to change, and the separation zones are reduced and migrate to the throat; Figure 9 (c) in FIG. 1 is Ma4.0: the separation zones continue to shrink, and the migration trend to the throat is obvious; Figure 9 (d) in FIG. 1 is Ma4.1: the separation zones are further reduced and migrate to the throat; Figure 9 (e) in FIG. 1 is Ma4.2: the separation zones continue to shrink and migrate to the throat; Figure 9 (f) in FIG. 1 is Ma4.3: the separation zones are reduced in size and develop downstream of the throat; Figure 9 (g) in FIG. 1 is Ma4.4: the lower surface separation zone almost disappears, and the upper surface separation zone propagates downstream of the throat, while maintaining a large scale, and a significant morphological change occurs; Figure 10 (h) in FIG. 1 is Ma4.5: the separation phenomenon is significantly weakened, self-starting is realized, and regular shock wave boundary layer interference (Regular SWBLI) is presented, which is consistent with the low Mach number design point (Ma4.5) in FIG. 2. ​ The observation results are consistent, which confirms that self-starting has been realized.

[0059] In summary, the effectiveness of the method of the present application and the self-starting characteristics of the self-starting inlet designed based on the double design point concept are evaluated by numerical simulation. The results show that the basic flow field is consistent with the inviscid axisymmetric flow field. When applied to inlet design, the inlet realizes the working characteristics consistent with the design target. At the high Mach number design point (Ma6), the incident shock wave reaches the lip, and full flow capture is realized. At the low Mach number design point (Ma4.5), the inlet exhibits the expected self-starting capability.

[0060] The present application reversely designs a wide-range self-starting basic flow field based on the curved shock wave theory, which can realize low Mach number self-starting; the tangent cutting theory is applied to construct a sub-mother basic flow field group in a series of tangent cutting planes according to the high / low Mach number flow requirements, to obtain a compression profile in the tangent cutting area; the side wall profile in the non-tangent cutting area is obtained through streamline tracing, to realize the design of a wide-range self-starting three-dimensional internal contraction inlet.

[0061] The above embodiments are merely preferred embodiments of the present application, and should not be considered as limiting the scope of the present application. Any equivalent changes and improvements made to the present application within the scope of the present application should still be considered as falling within the scope of the present application.

Claims

1. A wide-range self-starting inward contraction inlet reverse design method based on curved shock waves, characterized in that... Includes the following steps: 1) Based on the bending shock wave theory and the dual design point concept, a wide-area self-starting basic flow field is constructed with the total contraction ratio as a constraint; The dual design point concept is a high Mach number design point with a Mach number of 4+ and a low Mach number design point with a Mach number of 2+. 2) Divide the inlet shape of the air intake into a tangent region and a non-tangent region by the radius of curvature of the discrete points along the upper wall profile; 3) Apply the kissing theory to discretize the inlet shape of the kissing region and construct the kissing plane; in each kissing plane, design a wide-area self-starting primary and secondary flow fields. The primary flow field is a plane flow field with the maximum radius of curvature, and the secondary flow fields are generated by tracing the streamlines of the primary flow field. A series of kissing planes are merged to form the upper and lower walls of the kissing region of the air intake. 4) Obtain the side wall profile of the intake duct by streamline tracing method in the non-cutting area, and splice the side wall profile with the upper and lower walls of the cutting area obtained in step 3) to form the basic compression profile of the wide-area self-starting three-dimensional internal contraction intake duct.

2. The wide-range self-starting inward contraction inlet reverse design method based on curved shock waves as described in claim 1, characterized in that... In step 1), the wide-area self-starting basic flow field is constructed based on the bending shock wave theory and the dual design point concept. The specific method is as follows: (1) By applying the dual design point concept, the ratio of external pressure intensity and internal pressure intensity of the intake is controlled by the flow coefficient, thereby controlling the self-starting capability of the basic flow field. (2) Given the total contraction ratio (CR) constraint and the incident shock wave shape at the high Mach number design point, the first wall generatrix is ​​constructed using the bending characteristic line method, and the corresponding high Mach number flow field region is generated. (3) Based on the first wall generatrix and the inflow conditions at the low Mach number design point, solve the flow field region at the low Mach number design point, and obtain the initial lip streamline by streamline tracing based on the initial capture flow coefficient. (4) Based on the low Mach number design point flow field and initial lip streamline in step (3), control the Bezier curve to adjust the shape of the second wall generatrix so that the low Mach number capture flow coefficient of the basic flow field matches the target capture flow coefficient; at the same time, obtain the Mach number of the inner contraction section of the basic flow field, and calculate the expected inner contraction ratio based on CR as a constraint. (5) Define the third wall generatrix by the Bezier curve. Use the lower wall generatrix as a horizontal straight line as a constraint to make the reflected shock wave at the high Mach number design point intersect with the third wall generatrix at the throat. Iteratively adjust the control points of the Bezier curve until the error between the inner contraction ratio and the ICR in step (4) meets the accuracy requirements. (6) In a coordinate system with Ma-inner as the horizontal axis and 1 / ICR as the vertical axis, draw a starting state point based on the Ma-inner and 1 / ICR of the basic flow field. If the point is located above the self-starting boundary, the self-starting requirement is met and the basic flow field achieves self-starting under this condition. If the self-starting requirement is not met, adjust the initial flow coefficient and execute steps (3) to (5) again until the basic flow field meets the self-starting criterion. (7) When the total contraction ratio constraint and the self-starting requirement are met at the same time, the output is the basic flow field composed of the first wall generatrix, the second wall generatrix, the third wall generatrix and the horizontal lower wall.

3. The wide-range self-starting inward contraction inlet reverse design method based on curved shock waves as described in claim 1, characterized in that... In step 2), the specific method for dividing the radius of curvature of the discrete points along the upper wall profile of the intake duct inlet shape into a tangent region and a non-tangent region is as follows: The upper wall profile, lower wall profile, and side wall profile of the entrance shape are divided into several planes along the radius of curvature of the discrete points of the upper wall profile; among them, the intersecting plane at the junction of the upper wall profile and the side wall profile divides the entrance shape into the intersecting region in the middle and the non-intersecting regions on both sides.

4. The wide-range self-starting inward contraction inlet reverse design method based on curved shock waves as described in claim 1, characterized in that... In step 3), the inlet shape of the kissing region is discretized using the kissing theory to construct the kissing plane. Within each kissing plane, a wide-area self-starting mother-daughter basic flow field set is designed, and the upper and lower walls of the kissing region of the inlet are constructed. The specific method is as follows: (1) Within the tangent region, the curvature center of each discrete point is taken as the origin of the local coordinate system. The x-axis of the local coordinate system is along the incoming flow direction, and the y-axis points to the inside of the inlet. The curvature radius of the local inlet is the height of the incident shock wave, and a tangent plane is constructed. The inlet shape is dimensionless based on the maximum curvature radius value as the reference scale. After dimensionless scaling, the maximum curvature radius value R=1. The curvature radii of the remaining tangent planes are dimensionless proportionally, and the curvature radii corresponding to the remaining tangent planes are R. i ∈[0,1]; where the fundamental flow field constructed in the tangent plane corresponding to the dimensionless maximum curvature radius R is the parent fundamental flow field, and the height of the incident shock wave leading edge is the dimensionless curvature radius R. i The basic flow field is the sub-basic flow field; (2) The radius of curvature of each cutting plane intersects with the lower wall profile of the inlet shape, and the distance from the intersection point to the corresponding curvature center is defined as the central body height of each basic flow field of the cutting plane; (3) The parent basic flow field is generated using the method described in claim 2 for constructing a wide-area self-starting basic flow field; (4) The first wall generatrix of each sub-basic flow field is generated by streamline tracing in the parent basic flow field, and the incident shock wave of the sub-basic flow field is constrained to have the same shape as the incident shock wave of the parent basic flow field within the same radius range; the second wall generatrix, the third wall generatrix and the lower wall of the sub-flow field are constructed according to the iterative rules of steps (4) to (6) of claim 2.

5. The wide-range self-starting inward contraction inlet reverse design method based on curved shock waves as described in claim 1, characterized in that... In step 4), points are taken along the streamline direction of the basic flow fields in the non-cutting region. The side wall of the intake is obtained by the streamline tracing method. Then, the side wall profile is circumferentially spliced ​​with the generatrix of the wall of each cut basic flow field to obtain the basic compression profile of the three-dimensional internal contraction intake, thus realizing the design of the wide-area self-starting three-dimensional internal contraction intake.

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