Aircraft engine jet pipe design method

Abstract

The invention belongs to the technical field of aircraft engine jet pipe design, and particularly relates to an aircraft engine jet pipe design method which designs a short-distance jet pipe, considers the problems of aerodynamic performance, low detectability performance and the like of an S-shaped jet pipe, and can effectively reduce aerodynamic loss on the premise of meeting the low detectability omnidirectional shielding requirement.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft engine nozzle design, and specifically relates to an aircraft engine nozzle design method. Background Art

[0002] The S-bend nozzle of an aircraft engine is the strongest heat source toward the rear of the aircraft. The traditional axisymmetric nozzle is difficult to meet the low detectability requirements of the aircraft, and a special-shaped S-bend nozzle solution with good low detectability performance must be considered.

[0003] It is difficult to design an internal engine with high thrust and low bypass ratio. In order to control the center of gravity of the aircraft and other factors, the design space of the special-shaped S-bend nozzle (such as the nozzle) is compressed to a limited extent. In order to achieve omnidirectional shielding of the engine turbine end face in an ultra-short design space, the curvature will inevitably increase, and the aerodynamic loss will also increase, thereby causing thrust loss. Excessive thrust loss will lead to a reduction in many flight performances of the aircraft such as takeoff, landing, climb, and cruising.

[0004] Therefore, how to minimize aerodynamic losses while meeting low detectable design indicators within a limited design space is a difficulty in the aerodynamic design of ultra-short-range S-bend nozzles. In view of this, the present application is proposed. Summary of the invention

[0005] The purpose of the present application is to provide an aircraft engine nozzle design method to overcome or alleviate at least one of the known technical deficiencies.

[0006] The technical solution of this application is:

[0007] A method for designing an aircraft engine nozzle, comprising:

[0008] Step 1: Determine the center point of the S-bend nozzle outlet;

[0009] Step 2: Determine the center line of the inner tube of the S-bend nozzle;

[0010] Step 3: Determine the exit area of ​​the S-bend nozzle;

[0011] Step 4: Determine the S-bend nozzle outlet shape;

[0012] Step 5: Determine the area of ​​the middle control surface of the S-bend nozzle;

[0013] Step 6: Determine the middle control surface curve of the S-bend nozzle;

[0014] Step 7: Design the inner tube control line of the S-bend nozzle;

[0015] Step 8: Generate the S-bend nozzle profile.

[0016] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in step one, it is determined that y1 in the S-bend nozzle outlet center point O1 (x1, y1, z1) and y0 in the S-bend nozzle inlet center point O0 (x0, y0, z0) form a certain spanwise eccentricity, and the spanwise eccentricity should be controlled within 0.7D, where D is the engine outlet diameter.

[0017] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step 2 is specifically as follows:

[0018] S21, connect the center points O0, O1, of the inlet and outlet of the S-bend nozzle, tangent to the inlet and outlet planes, and draw a spline l0;

[0019] S22, a station point at 50% to 60% on the sampling line l0 is longitudinally offset. The offset of this point from the center point O0 of the S-bend nozzle inlet is controlled within 0.7D and recorded as the intermediate control surface reference design point O mid-0 ;

[0020] S23, connect the S-bend nozzle inlet center point O0, the intermediate control surface reference design point O mid-0 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and a spline l is drawn 1-0 , as the center line of the inner tube of the S-bend nozzle.

[0021] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in S21, the coordinates (x, y, z) of any point on the spline l0 meet:

[0022]

[0023] in,

[0024] η1 is the position ratio.

[0025] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in S21, η1 takes a value of 0 to 1.

[0026] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step three is specifically:

[0027] A out =A yuan ×(2-σ) / cosθ;

[0028] in,

[0029] A out is the exit area of ​​the S-bend nozzle;

[0030] A yuanis the original axisymmetric nozzle exit area of ​​the engine;

[0031] σ is the estimated total pressure recovery coefficient of the S-bend nozzle;

[0032] θ is the bevel angle of the S-bend nozzle outlet.

[0033] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in step four, the S-bend nozzle outlet shape is designed to be a multi-segment circular arc shape, and the transition radius thereof is not less than 120 mm.

[0034] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step five is specifically:

[0035] A(x)=(A out -A in )×(-3×η2 4 +4×η2 3 )+(1+k×η2)×A in ;

[0036] x0+0.5(x1-x0)≤x≤x0+0.6(x1-x0);

[0037] in,

[0038] A in is the inlet area of ​​the S-bend nozzle;

[0039] A out is the exit area of ​​the S-bend nozzle;

[0040] η2 is the position ratio of the center point of the middle surface of the S-bend spray;

[0041] k is the correction coefficient.

[0042] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in step 5, η2 is taken as 0.5 to 0.6;

[0043] The value of k is 0.02~0.05.

[0044] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step six includes:

[0045] S61, passing the intermediate control surface reference design point O mid-0 Make the center line of the inner tube of the S-bend nozzle l 1-0 The normal plane intersects with the upper surface of the fuselage to obtain curve l2;

[0046] S62, in the normal plane, take the middle control surface as the reference design point O mid-0With point as the center, draw a rectangle with a length of 2H and a width of 2W, where H is the height of the nozzle outlet and W is the width of the nozzle outlet;

[0047] S63. Make points P1, P2, and P3 on the normal plane to control the upper edge line l3 of the middle control surface of the S-bend nozzle, where:

[0048] The distance between point P1 and the upper edge of the rectangle is D1, and the center point O of the middle control surface mid-0 The distance to the left is L1;

[0049] Point P2 is at a distance D2 below the upper edge of the rectangle, and at the center point O of the middle control surface mid-0 The distance to the left is L2;

[0050] Point P3 is at a distance D3 above the upper edge of the rectangle and at the center point O of the middle control surface. mid-0 The distance to the right is L3;

[0051] L1 is W, D1 is 0.9H, L2 is 0.5W, D2 is 0.2H, L3 is 0.9W, D3 is 0.4H;

[0052] S64. Make points P4, P5, and P6 on the normal plane to control the lower edge line l4 of the middle control surface of the S-bend nozzle, where:

[0053] Point P4 is at a distance D4 above the lower edge of the rectangle, and is at the center point O of the middle control surface. mid-0 The distance to the left is L4;

[0054] The distance between point P5 and the lower edge of the rectangle is D5, and the center point O of the middle control surface mid-0 The distance to the left is L5;

[0055] The distance between point P6 and the lower edge of the rectangle is D6, and the center point O of the middle control surface mid-0 The distance to the right is L6;

[0056] The value of L4 is 0.7W, the value of D4 is 0.3H, the value of L5 is 0.1W, the value of D5 is 0.35H,

[0056] The value of L6 is 0.8W, and the value of D6 is 0.3H;

[0057] S65, connecting points P3 and P6, as control line l5, draw an arc line l6, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the control line l5, and draw an arc line l7, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the lower edge line l4 of the middle control surface of the S-bend nozzle;

[0058] The point where the arc line l6 is tangent to the upper edge line l3 is between points P2 and P3;

[0059] The point where the arc line l7 is tangent to the upper edge line l3 is between points P1 and P2, and the point where the arc line l7 is tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle is between points P4 and P5;

[0060] S66, take point P7 on the lower edge line l4 of the middle control surface of the S-bend nozzle and point P8 on the arc line l6 as control elements, connect points P7 and P8 to make a spline, and make it tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle and the arc line l6 to obtain a spline l8;

[0061] Points P7 and P8 are intercepted on the lower edge line l4 and arc line l6 of the middle control surface of the S-bend nozzle through the curve length ratio, and the curve length ratio is specifically 0.92l4 and 0.8l6;

[0062] S67, counterclockwise connect the upper line l3, arc line l7, lower line of the middle control surface of the S-bend nozzle, spline l8, arc line l6, and get the middle control surface curve l mid .

[0063] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in S63, the curve l2 is offset by D0 along the normal plane as a verification line of the upper edge line l3 of the middle control surface of the S-curve nozzle, wherein D0 is 1.2H.

[0064] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step seven includes:

[0065] S71. Design seven control points at the inlet, middle control surface and outlet of the S-bend nozzle. Draw splines from the inlet of the S-bend nozzle to the middle control surface and the outlet of the S-bend nozzle. The splines are tangent to the inlet and outlet of the S-bend nozzle. Seven control lines τ are obtained. n (n=1-7);

[0066] S72, on each control line τ n Take a control point at the 80% position and divide the control line into three segments, namely ab segment, bc segment and cd segment;

[0067] S73, on the seven control lines τ n Take N measuring points on the three sections, measure the curvature radius at each measuring point, and calculate the average curvature radius δ of the inner tube of the S-bend nozzle in the three sections a-b , δ b-c , δ c-d , calculate the radius ratio of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d ;

[0068] S74, for seven control lines τ n Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is smaller than ε a-b Not less than 2, in order to meet the actual rapid bending of the front section of the inner tube, the radius of the curved surface in the bc section is greater than ε b-c Not less than 2, the radius ratio of the surface in the cd segment is ε c-d Not more than 6;

[0069] S75, take the center O of the middle control surface area mid-1 , connect the S-bend nozzle inlet center point O0, the middle control surface area center point O mid-1 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and the center line l of the inner tube of the S-bend nozzle is drawn 1-1 ;

[0070] S76, on the center line of the inner tube of the S-bend nozzle 1-1 Take m measuring points on the top, construct normal planes at each measuring point, intersect with the inner tube to obtain the cross section of the inner tube along the flow direction, and calculate the seven control lines τ n Adjustments are made so that the contraction ratio of the cross-sectional area of ​​the inner tube of the S-bend nozzle does not exceed ≤5% in the ab section, does not exceed 5% in the bc section, and is not less than 18% in the cd section.

[0071] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in S73, the average curvature radius δ of the inner tube of the S-bend nozzle in three sections is calculated. a-b , δ b-c , δ c-d Specifically:

[0072]

[0073] in,

[0074] δ is the average curvature radius of the inner tube of the S-bend nozzle in three sections;

[0075] r ni is the nth control line τ n , the radius of curvature at the i-th measurement point on the three segments.

[0076] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, in S73, the surface radius ratio ε of the inner tube of the S-bend nozzle in the three sections is calculated. a-b , ε b-c , ε c-d Specifically:

[0077]

[0078] in,

[0079] ε is the ratio of the curvature radius of the inner tube of the S-bend nozzle in the three sections;

[0080] D in is the inlet diameter of the S-bend nozzle.

[0081] According to at least one embodiment of the present application, in the above-mentioned aircraft engine nozzle design method, step eight is specifically:

[0082] The seven control lines τ of the inner tube of the S-bend nozzle n (n=1~7) is used as a guide line to generate an S-bend nozzle profile through the multi-section curved surface forming function.

[0083] This application has at least the following beneficial technical effects:

[0084] The invention provides an aircraft engine nozzle design method, and designs an ultra-short-range nozzle, taking into account the aerodynamic performance and low-detectability performance of the S-bend nozzle, and can effectively reduce aerodynamic losses while meeting the low-detectability omnidirectional shielding requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 is a schematic diagram of an aircraft engine nozzle design method provided in an embodiment of the present application;

[0086] Figure 2 is a schematic diagram of determining the middle control surface curve of the S-bend nozzle provided in an embodiment of the present application;

[0087] Figure 3 is a schematic diagram of determining the left and right side lines of the middle control surface of the S-bend nozzle provided in an embodiment of the present application;

[0088] Figure 4 Schematic diagram of the middle control surface curve of the S-bend nozzle provided in the embodiment of the present application;

[0089] Figure 5 It is a schematic diagram provided in an embodiment of the present application of taking a control point on a control line, dividing the control line into three sections, taking measurement points, measuring the curvature radius at each measurement point, and calculating the average curvature radius.

[0090] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be construed as limitations on the present application. DETAILED DESCRIPTION

[0091] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be described in further detail in detail and in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design.

[0092] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application shall have the usual meanings understood by those of ordinary skill in the art to which this application belongs. The words used in the description of this application to indicate orientation are only used to indicate relative directions or positional relationships. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application indicates that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0093] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installation", "connection" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Technical personnel in the field can understand its specific meaning in this application according to the specific circumstances.

[0094] Comprehensive design of the engine S-bend nozzle by controlling the middle special-shaped surface, segmented curvature control of the surface, and segmented contraction control of the cross-sectional area along the flow direction is a feasible way to resolve the contradiction between the aerodynamic requirements of the ultra-short-range S-bend nozzle and the low detectability requirements of the aircraft. Based on this, the embodiment of the present application provides an aircraft engine nozzle design method. In view of the problem that the ultra-short-range S-bend nozzle is difficult to take into account the aerodynamic characteristics while meeting the omnidirectional shielding of the engine outlet, the middle control surface is segmented and profiled to reduce the bending degree of the inner tube, and then supplemented by the control of the inner tube curvature and cross-sectional area, the aerodynamic loss of the low-detectable ultra-short-range nozzle can be reduced and the thrust can be improved. Figure 1 shown.

[0095] Step 1: Determine the center point of the S-bend nozzle outlet.

[0096] If the S-bend nozzle only relies on the longitudinal or spanwise S-bend design, it is difficult to reduce the degree of curvature of the inner tube within an ultra-short distance. Both are required. Therefore, y1 in the center point O1 (x1, y1, z1) of the S-bend nozzle outlet needs to form a certain spanwise eccentricity with y0 in the center point O0 (x0, y0, z0) of the S-bend nozzle inlet. In order to control the curvature of the inner tube, the spanwise eccentricity should be controlled within 0.7D, where D is the engine outlet diameter.

[0097] Step 2: Determine the center line of the inner tube of the S-bend nozzle.

[0098] S21. Connect the center points O0, O1, of the inlet and outlet of the S-bend nozzle, make them tangent to the inlet and outlet planes, and draw a spline l0.

[0099] The coordinates (x, y, z) of any point on the spline l0 meet the following requirements:

[0100]

[0101] in,

[0102] η1 is the position ratio, ranging from 0 to 1.

[0103] S22, a station point at 50% to 60% on the sampling line l0 is longitudinally offset. The offset of this point from the center point O0 of the S-bend nozzle inlet is controlled within 0.7D and recorded as the intermediate control surface reference design point O mid-0 .

[0104] S23, connect the S-bend nozzle inlet center point O0, the intermediate control surface reference design point O mid-0 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and a spline l is drawn 1-0 , as the center line of the inner tube of the S-bend nozzle.

[0105] Step 3: Determine the S-bend nozzle outlet area.

[0106] In order to improve the low detectability performance, the S-bend nozzle outlet is designed to be reverse beveled. Its outlet area is related to the outlet area of ​​the original axisymmetric nozzle of the engine, the bevel angle, and the total pressure loss of the nozzle. The specific calculation is as follows:

[0107] A out =A yuan ×(2-σ) / cosθ;

[0108] in,

[0109] A out is the exit area of ​​the S-bend nozzle;

[0110] A yuan is the original axisymmetric nozzle exit area of ​​the engine;

[0111] σ is the estimated total pressure recovery coefficient of the S-bend nozzle;

[0112] θ is the bevel angle of the S-bend nozzle outlet.

[0113] Step 4: Determine the shape of the S-bend nozzle outlet.

[0114] The S-bend nozzle outlet shape is designed as a multi-segment arc shape according to the low detectability requirements, and is designed based on the principle of facilitating integration with the fuselage. In order to make the rear section of the S-bend nozzle have a significant straightening effect, the transition radius should be no less than 120mm.

[0115] Step 5: Determine the area of ​​the middle control surface of the S-bend nozzle.

[0116] The area of ​​the middle control surface is related to the area distribution of the S-bend nozzle pipe. The shape of the curved surface at this position changes more dramatically, so the curved surface area should be larger. Its area can be calculated according to the following formula:

[0117] A(x)=(A out -A in )×(-3×η2 4 +4×η2 3 )+(1+k×η2)×A in ;

[0118] x0+0.5(x1-x0)≤x≤x0+0.6(x1-x0);

[0119] in,

[0120] A in is the inlet area of ​​the S-bend nozzle;

[0121] A out is the exit area of ​​the S-bend nozzle;

[0122] η2 is the ratio of the center point position of the middle curved surface of the S-bend spray, and its value is 0.5~0.6;

[0123] k is the correction coefficient, and its value ranges from 0.02 to 0.05.

[0124] Step 6: Determine the middle control surface curve of the S-bend nozzle, such as Figure 2 shown.

[0125] S61, passing the intermediate control surface reference design point O mid-0 Make the center line of the inner tube of the S-bend nozzle l 1-0 The normal plane intersects with the upper surface of the fuselage to obtain curve l2.

[0126] S62, in the normal plane, take the middle control surface as the reference design point O mid-0 With point as the center, draw a rectangle with a length of 2H and a width of 2W, where H is the height of the nozzle outlet and W is the width of the nozzle outlet.

[0127] S63. Make points P1, P2, and P3 on the normal plane to control the upper edge line l3 of the middle control surface of the S-bend nozzle, where:

[0128] The distance between point P1 and the upper edge of the rectangle is D1, and the center point O of the middle control surfacemid-0 The distance to the left is L1;

[0129] Point P2 is at a distance D2 below the upper edge of the rectangle, and at the center point O of the middle control surface mid-0 The distance to the left is L2;

[0130] Point P3 is at a distance D3 above the upper edge of the rectangle and at the center point O of the middle control surface. mid-0 The distance to the right is L3;

[0131] L1 is W, D1 is 0.9H, L2 is 0.5W, D2 is 0.2H,

[0132] The value of L3 is 0.9W and the value of D3 is 0.4H.

[0134] The curve l2 is offset by D0 along the normal plane as the verification line of the edge line l3 on the middle control surface of the S-bend nozzle. The edge line l3 on the middle control surface of the S-bend nozzle should not exceed the verification line to meet the space layout requirements, where D0 is 1.2H.

[0135] S64. Make points P4, P5, and P6 on the normal plane to control the lower edge line l4 of the middle control surface of the S-bend nozzle, where:

[0136] Point P4 is at a distance D4 above the lower edge of the rectangle, and is at the center point O of the middle control surface. mid-0 The distance to the left is L4;

[0137] The distance between point P5 and the lower edge of the rectangle is D5, and the center point O of the middle control surface mid-0 The distance to the left is L5;

[0138] The distance between point P6 and the lower edge of the rectangle is D6, and the center point O of the middle control surface mid-0 The distance to the right is L6;

[0139] The value of L4 is 0.7W, the value of D4 is 0.3H, the value of L5 is 0.1W, the value of D5 is 0.35H, the value of L6 is 0.8W, and the value of D6 is 0.3H.

[0141] The inner tube of the S-bend nozzle is designed in an upper S-bend form, and low-detectability omnidirectional shielding is mainly ensured by the lower edge line. Among them, the position of point P5 is the most important, which is the inflection point of the concave shape of the middle control surface.

[0142] S65, connecting points P3 and P6, as control line l5, make an arc line l6, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the control line l5, and make an arc line l7, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the lower edge line l4 of the middle control surface of the S-bend nozzle.

[0143] The point where the arc line l6 is tangent to the upper edge line l3 is between points P2 and P3.

[0144] The point where the arc line l7 is tangent to the upper edge line l3 is between points P1 and P2, and the point where the arc line l7 is tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle is between points P4 and P5.

[0145] S66, take point P7 on the lower edge line l4 of the middle control surface of the S-bend nozzle, and take point P8 on the arc line l6 as control elements, connect points P7 and P8 to make a spline, and make it tangent to the lower edge line l4 and arc line l6 of the middle control surface of the S-bend nozzle, and get spline l8, as shown in Figure 3 shown.

[0146] Points P7 and P8 are intercepted on the lower edge line l4 and arc line l6 of the middle control surface of the S-bend nozzle through the curve length ratio, and the curve length ratio is specifically 0.92l4 and 0.8l6.

[0147] S67, counterclockwise connect the upper line l3, arc line l7, lower line of the middle control surface of the S-bend nozzle, spline l8, arc line l6, and get the middle control surface curve l mid ,like Figure 4 shown.

[0148] The area of ​​the middle control surface is not greater than 5% of the inlet area of ​​the S-bend nozzle. The curved surface shape is designed to reduce the bending degree of the inner tube and can be appropriately concave with an arc of no more than 2°.

[0149] Step 7: Design the inner tube control line of the S-bend nozzle.

[0150] S71. Design seven control points at the inlet, middle control surface and outlet of the S-bend nozzle. Draw splines from the inlet of the S-bend nozzle to the middle control surface and the outlet of the S-bend nozzle. The splines are tangent to the inlet and outlet of the S-bend nozzle. Seven control lines τ are obtained. n (n=1~7).

[0151] S72, on each control line τ n Take a control point at the 80% position and divide the control line into three sections, namely ab section, bc section, and cd section, where a, b, c, and d are the control points on the S-bend nozzle inlet, the middle control surface, the 80% position of the control line, and the S-bend nozzle outlet, respectively. Figure 5 shown.

[0152] S73, on the seven control lines τ n Take N measuring points on the three sections, measure the curvature radius at each measuring point, and calculate the average curvature radius δ of the inner tube of the S-bend nozzle in the three sections a-b , δ b-c , δ c-d , calculate the radius ratio of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d .

[0153]

[0154] in,

[0155] δ is the average curvature radius of the inner tube of the S-bend nozzle in three sections;

[0156] r ni is the nth control line τ n , the curvature radius at the i-th measuring point on the three segments, taking the three adjacent measuring points q i-1 ,q i ,q i+1 Draw an arc and measure its radius.

[0157]

[0158] in,

[0159] ε is the ratio of the curvature radius of the inner tube of the S-bend nozzle in the three sections;

[0160] D in is the inlet diameter of the S-bend nozzle.

[0161] Taking the first control line τ1 as an example, the line segment is divided into a1-b1 segment, b1-c1 segment, and c1-d1 segment. a1, b1, c1, and d1 are the control points on the S-bend nozzle inlet, the middle control surface, the 80% position of the control line, and the S-bend nozzle outlet, respectively. N measurement points are taken in the a1-b1 segment, denoted as q 1N , take any three adjacent points q 1i-1 ,q 1i ,q 1i+1 Draw an arc and measure the radius of curvature r of this section 1i , the rest of the second to seventh control lines τ2, τ3, τ4, τ5, τ6, τ7, and so on, can be deduced, the curvature radius of each control line at any three points in the ab segment can be obtained, and the average curvature radius δ of the inner tube of the S-bend nozzle in the ab segment can be calculated a-b , surface radius ratio ε a-b ,as follows:

[0162]

[0163]

[0164] S74, for seven control lines τ n Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is smaller than ε a-b Not less than 2, in order to meet the actual rapid bending of the front section of the inner tube, the radius of the curved surface in the bc section is greater than ε b-c Not less than 2, the radius ratio of the surface in the cd segment is ε c-d Not more than 6.

[0165] S75, take the center O of the middle control surface area mid-1 , connect the S-bend nozzle inlet center point O0, the middle control surface area center point O mid-1 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and the center line l of the inner tube of the S-bend nozzle is drawn 1-1 .

[0166] S76, on the center line of the inner tube of the S-bend nozzle 1-1 Take m measuring points on the top, construct normal planes at each measuring point, intersect with the inner tube to obtain the cross section of the inner tube along the flow direction, and calculate the seven control lines τ n Adjustments are made so that the contraction ratio of the cross-sectional area of ​​the inner tube of the S-bend nozzle does not exceed ≤5% in the ab section, does not exceed 5% in the bc section, and is not less than 18% in the cd section.

[0167] Step 8: Generate the S-bend nozzle profile.

[0168] The seven control lines τ of the inner tube of the S-bend nozzle n (n=1~7) is used as a guide line to generate an S-bend nozzle profile through the multi-section curved surface forming function.

[0169] The above embodiment discloses a method for designing an aircraft engine nozzle. First, the intermediate control surface is used as a core design element, which has three effects on the ultra-short-range nozzle. First, the number of bounces of the electromagnetic incident wave in the cavity is increased to improve the rearward low detectability performance of the S-bend nozzle. Second, the degree of inner tube bending is reduced and the inner tube curvature and area control are involved to reduce aerodynamic losses. Third, the S-bend offset is reduced to achieve low detectability shielding of the ultra-short-range S-bend nozzle while increasing the distance from the fuselage surface to solve the problem of inner tube arrangement of the S-bend nozzle. Secondly, the S-bend nozzle is divided into three sections: the head, middle and tail sections from the middle control surface and the 80% centerline station section. The curvature change and area distribution of the pipe are controlled section by section. The head section aims to quickly achieve partial shielding, and the cross-sectional shape and surface curvature are designed to transition quickly. Therefore, the excessive flow rate in this section will cause adverse phenomena such as airflow separation and swirl, and it is necessary to control the area to change gently to reduce the flow rate; the middle section is a transition section that connects the previous and the next, with the goal of strengthening shielding and presetting accelerated expansion, and the surface curvature needs to transition quickly, but the area begins to converge rapidly; the tail section aims to accelerate expansion and generate strong thrust, and the area needs to converge rapidly, but in order to avoid high-speed airflow separation, the surface curvature needs to transition slowly. Finally, the S-bend nozzle outlet is designed as a reverse bevel form to further improve the radar scattering characteristics of the S-bend nozzle. It should be noted that the reverse bevel outlet should not cut off the throat position of the S-bend nozzle to ensure that the aerodynamic performance of the S-bend nozzle is not affected.

[0170] The above embodiment discloses a method for designing an aircraft engine nozzle, which designs an intermediate control surface from the S-bend nozzle inlet along the normal plane at the 50% to 60% position of the S-bend nozzle centerline, and realizes omnidirectional and full shielding of the engine turbine end face through the curved surface and the direction of the S-bend centerline, and divides the S-bend nozzle into three sections based on the intermediate control surface, the S-bend nozzle inlet-intermediate control surface is the head part, the cross-sectional area decreases slowly, and the cross-sectional shape transitions quickly, the intermediate control surface-80% centerline position cross section is the middle part, the cross-sectional area decreases at a medium speed, and the cross-sectional shape transitions quickly, and the 80% centerline position cross section-S-bend nozzle outlet is the tail part, the cross-sectional area decreases rapidly, and the cross-sectional shape transitions slowly.

[0171] The head part of the S-bend nozzle is responsible for the rapid bending of the inner tube and the slow reduction of the area, and its curvature radius ratio is not less than 2, and the area shrinkage is not more than 5%; the middle part of the S-bend nozzle is responsible for the rapid bending of the inner tube and the medium-speed reduction of the area, and its curvature radius ratio is not less than 2, and the area shrinkage is not more than 10%; the tail part of the S-bend nozzle is responsible for the slow bending of the inner tube and the rapid reduction of the area, and its curvature radius ratio is not more than 6, and the area shrinkage is not less than 18%.

[0172] The above-mentioned embodiment discloses a method for designing an aircraft engine nozzle, which can reduce the overall curvature of the inner tube to 0.7D (0.9D in conventional design) in a space with a length-to-diameter ratio of less than 3.5D through segmented special-shaped design of the shape of the intermediate control surface, gentle convergence control of the curved surface area, segmented control of the curved surface radius ratio and control of the cross-sectional area along the flow direction. This can not only achieve omnidirectional shielding of the engine outlet to meet the low detectability requirements, but also reduce the curvature of the inner tube, effectively reducing the aerodynamic loss of the S-bend nozzle, thereby reducing the thrust loss of the S-bend nozzle.

[0173] The above-mentioned embodiment discloses a method for designing an aircraft engine nozzle, in which the shape of the intermediate control surface is segmentedly designed as a "wing blade concave shape" according to the results of aerodynamic and low detectability evaluations, which can reduce the degree of bending of the inner tube. At the same time, considering that the curved surface transition caused by the profiling of the intermediate control surface is relatively complex, the cross-sectional area along the flow direction of the S-bend nozzle inlet-intermediate control surface-80% centerline station cross-sectional area is segmented to reduce aerodynamic losses.

[0174] The above embodiment discloses a method for designing an aircraft engine nozzle, which achieves moderate control of the degree of curvature of the inner tube by controlling the parameters of the position, cross-sectional shape, and cross-sectional area of ​​the intermediate control surface, in conjunction with the law of change of the cross-sectional area along the flow direction in the pipeline, the transition form of the center line, etc., so as to reduce the aerodynamic loss caused by excessive curvature.

[0175] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A method for designing an aircraft engine nozzle, characterized in that: include: Step 1: Determine the center point of the S-bend nozzle outlet; Step 2: Determine the center line of the inner tube of the S-bend nozzle; Step 3: Determine the exit area of ​​the S-bend nozzle; Step 4: Determine the S-bend nozzle outlet shape; Step 5: Determine the area of ​​the middle control surface of the S-bend nozzle; Step 6: Determine the middle control surface curve of the S-bend nozzle; Step 7: Design the inner tube control line of the S-bend nozzle; Step 8: Generate the S-bend nozzle profile.

2. The aircraft engine nozzle design method according to claim 1, characterized in that: In step 1, it is determined that y1 of the S-bend nozzle outlet center point O1 (x1, y1, z1) and y0 of the S-bend nozzle inlet center point O0 (x0, y0, z0) form a certain spanwise eccentricity, and the spanwise eccentricity should be controlled within 0.7D, where D is the engine outlet diameter.

3. The aircraft engine nozzle design method according to claim 2, characterized in that: Step 2 is as follows: S21, connect the center points O0, O1, of the inlet and outlet of the S-bend nozzle, tangent to the inlet and outlet planes, and draw a spline l0; S22, a station point at 50% to 60% on the sampling line l0 is longitudinally offset. The offset of this point from the center point O0 of the S-bend nozzle inlet is controlled within 0.7D and recorded as the intermediate control surface reference design point O mid-0 ; S23, connect the S-bend nozzle inlet center point O0, the intermediate control surface reference design point O mid-0 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and a spline l is drawn 1-0 , as the center line of the inner tube of the S-bend nozzle.

4. The method for designing an aircraft engine nozzle according to claim 3, characterized in that: In S21, the coordinates (x, y, z) of any point on the spline l0 meet the following conditions: η1=(x-x0) / (x1-x0) y=(y1-y0)×(3×η1 2 -2×η1 3 )+y0 z=(z1-z0)×(3×η1 2 -2×η1 3 )+z0; in, η1 is the position ratio.

5. The aircraft engine nozzle design method according to claim 4, characterized in that: In S21, η1 takes a value between 0 and 1.

6. The aircraft engine nozzle design method according to claim 5, characterized in that: Step three is as follows: A out =A yuan ×(2-σ) / cosθ; in, A out is the exit area of ​​the S-bend nozzle; A yuan is the original axisymmetric nozzle exit area of ​​the engine; σ is the estimated total pressure recovery coefficient of the S-bend nozzle; θ is the bevel angle of the S-bend nozzle outlet.

7. The method for designing an aircraft engine nozzle according to claim 6, characterized in that: In step 4, the S-bend nozzle outlet is designed to have a multi-segment arc shape, and the transition radius is not less than 120 mm.

8. The method for designing an aircraft engine nozzle according to claim 7, characterized in that: Step 5 is as follows: A(x)=(A out -A in )×(-3×η2 4 +4×η2 3 )+(1+k×η2)×A in ; x0+0.5(x1-x0)≤x≤x0+0.6(x1-x0); in, A in is the inlet area of ​​the S-bend nozzle; A out is the exit area of ​​the S-bend nozzle; η2 is the position ratio of the center point of the middle surface of the S-bend spray; k is the correction coefficient.

9. The method for designing an aircraft engine nozzle according to claim 8, characterized in that: In step 5, η2 is set to 0.5 to 0.6; The value of k is 0.02~0.

05.

10. The aircraft engine nozzle design method according to claim 9, characterized in that: Step six includes: S61, passing the intermediate control surface reference design point O mid-0 Make the center line of the inner tube of the S-bend nozzle l 1-0 The normal plane intersects with the upper surface of the fuselage to obtain curve l2; S62, in the normal plane, take the middle control surface as the reference design point O mid-0 With point as the center, draw a rectangle with a length of 2H and a width of 2W, where H is the height of the nozzle outlet and W is the width of the nozzle outlet; S63. Make points P1, P2, and P3 on the normal plane to control the upper edge line l3 of the middle control surface of the S-bend nozzle, where: The distance between point P1 and the upper edge of the rectangle is D1, and the center point O of the middle control surface mid-0 The distance to the left is L1; Point P2 is at a distance D2 below the upper edge of the rectangle, and at the center point O of the middle control surface mid-0 The distance to the left is L2; Point P3 is at a distance D3 above the upper edge of the rectangle and at the center point O of the middle control surface. mid-0 The distance to the right is L3; L1 is W, D1 is 0.9H, L2 is 0.5W, D2 is 0.2H, L3 is 0.9W, D3 is 0.4H; S64. Make points P4, P5, and P6 on the normal plane to control the lower edge line l4 of the middle control surface of the S-bend nozzle, where: Point P4 is at a distance D4 above the lower edge of the rectangle, and is at the center point O of the middle control surface. mid-0 The distance to the left is L4; The distance between point P5 and the lower edge of the rectangle is D5, and the center point O of the middle control surface mid-0 The distance to the left is L5; The distance between point P6 and the lower edge of the rectangle is D6, and the center point O of the middle control surface mid-0 The distance to the right is L6; The value of L4 is 0.7W, the value of D4 is 0.3H, the value of L5 is 0.1W, the value of D5 is 0.35H, the value of L6 is 0.8W, and the value of D6 is 0.3H; S65, connecting points P3 and P6, as control line l5, draw an arc line l6, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the control line l5, and draw an arc line l7, tangent to the upper edge line l3 of the middle control surface of the S-bend nozzle and the lower edge line l4 of the middle control surface of the S-bend nozzle; The point where the arc line l6 is tangent to the upper edge line l3 is between points P2 and P3; The point where the arc line l7 is tangent to the upper edge line l3 is between points P1 and P2, and the point where the arc line l7 is tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle is between points P4 and P5; S66, take point P7 on the lower edge line l4 of the middle control surface of the S-bend nozzle and point P8 on the arc line l6 as control elements, connect points P7 and P8 to make a spline, and make it tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle and the arc line l6 to obtain a spline l8; Points P7 and P8 are intercepted on the lower edge line l4 and arc line l6 of the middle control surface of the S-bend nozzle through the curve length ratio, and the curve length ratio is specifically 0.92l4 and 0.8l6; S67, counterclockwise connect the upper edge line l3, arc line l7, lower edge line of the middle control surface of the S-bend nozzle, spline l8, arc line l6, and get the middle control surface curve l mid .

11. The aircraft engine nozzle design method according to claim 10, characterized in that: In S63, the curve l2 is offset by D0 along the normal plane to serve as the verification line of the upper edge line l3 of the middle control surface of the S-bend nozzle, wherein D0 is 1.2H.

12. The aircraft engine nozzle design method according to claim 11, characterized in that: Step seven includes: S71. Design seven control points at the inlet, middle control surface and outlet of the S-bend nozzle. Draw splines from the inlet of the S-bend nozzle to the middle control surface and the outlet of the S-bend nozzle. The splines are tangent to the inlet and outlet of the S-bend nozzle. Seven control lines τ are obtained. n (n=1-7); S72, on each control line τ n Take a control point at the 80% position and divide the control line into three segments, namely ab segment, bc segment and cd segment; S73, on the seven control lines τ n Take N measuring points on the three sections, measure the curvature radius at each measuring point, and calculate the average curvature radius δ of the inner tube of the S-bend nozzle in the three sections a-b ,δ b-c ,δ c-d , calculate the radius ratio of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d ; S74, for seven control lines τ n Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is smaller than ε a-b Not less than 2, in order to meet the actual rapid bending of the front section of the inner tube, the radius of the curved surface in the bc section is greater than ε b-c Not less than 2, the radius ratio of the surface in the cd segment is ε c-d Not more than 6; S75, take the center O of the middle control surface area mid-1 , connect the S-bend nozzle inlet center point O0, the middle control surface area center point O mid-1 , the center point O1 of the S-bend nozzle outlet is tangent to the inlet and outlet planes of the S-bend nozzle, and the center line l of the inner tube of the S-bend nozzle is drawn 1-1 ; S76, on the center line of the inner tube of the S-bend nozzle 1-1 Take m measuring points on the top, construct normal planes at each measuring point, intersect with the inner tube to obtain the cross section of the inner tube along the flow direction, and calculate the seven control lines τ n Adjustments are made so that the contraction ratio of the cross-sectional area of ​​the inner tube of the S-bend nozzle does not exceed ≤5% in the ab section, does not exceed 5% in the bc section, and is not less than 18% in the cd section.

13. The method for designing an aircraft engine nozzle according to claim 12, characterized in that: In S73, calculate the average curvature radius δ of the inner tube of the S-bend nozzle in three sections a-b ,δ b-c ,δ c-d Specifically: in, δ is the average curvature radius of the inner tube of the S-bend nozzle in three sections; is the nth control line τ n , the radius of curvature at the i-th measurement point on the three segments.

14. The aircraft engine nozzle design method according to claim 13, characterized in that: In S73, calculate the radius ratio ε of the inner tube of the S-bend nozzle in three sections. a-b , ε b-c , ε c-d Specifically: in, ε is the ratio of the curvature radius of the inner tube of the S-bend nozzle in the three sections; D in is the inlet diameter of the S-bend nozzle.

15. The aircraft engine nozzle design method according to claim 14, characterized in that: Step 8 is as follows: The seven control lines τ of the inner tube of the S-bend nozzle n (n=1~7) is used as a guide line to generate an S-bend nozzle profile through the multi-section curved surface forming function.

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