A method of designing an aircraft engine nozzle

Abstract

The application belongs to the technical field of aircraft engine nozzle design, and particularly relates to a kind of aircraft engine nozzle design method, designs short-range nozzle, and considers the aerodynamic performance, low detectability performance and other aspects of S-bend nozzle, which can effectively reduce aerodynamic loss under the premise of meeting the low detectability omnidirectional shielding requirements.

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. Traditional axisymmetric nozzles are difficult to meet the low-detectability requirements of aircraft, so it is necessary to consider special-shaped S-bend nozzle solutions with good low-detectability performance.

[0003] The design of an internal engine with high thrust and low bypass ratio is difficult, and 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, its curvature is bound to increase, and the aerodynamic loss will also increase, which will cause thrust loss. Excessive thrust loss will lead to a reduction in many flight performances of the aircraft such as takeoff, landing, climbing, and cruising.

[0004] Therefore, how to minimize aerodynamic losses while meeting low-detectability 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, this application is proposed. Summary of the Invention

[0005] The purpose of this 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 centerline of the inner tube of the S-bend nozzle;

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

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

[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 is 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 and O1 of the inlet and outlet of the S-bend nozzle, draw a spline l0 tangent to the inlet and outlet planes;

[0019] S22, a station point 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 the following conditions:

[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 as follows:

[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 engine's original axisymmetric nozzle outlet area;

[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 as follows:

[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 ratio of the center point position of the S-bend spray middle surface;

[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 five, η2 is set to a value of 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. Construct 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 is mid-0 The distance to the left is L1;

[0049] The distance between point P2 and the upper edge of the rectangle is D2, and the center point O of the middle control surface is 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] The value of L1 is W, the value of D1 is 0.9H, the value of L2 is 0.5W, the value of D2 is 0.2H, the value of L3 is 0.9W, and the value of 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 is mid-0 The distance to the left is L5;

[0055] Point P6 is at a distance D6 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 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, the value of L6 is 0.8W, and the value of D6 is 0.3H;

[0057] S65, connecting points P3 and P6, as the control line l5, draw an arc line l6, which is 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, which is 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 form a spline, which is tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle and the arc line l6 to obtain 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 edge line l3, arc line l7, lower edge line of the middle control surface of the S-bend nozzle, spline l8, arc line l6 to obtain 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 the verification line of the upper edge line l3 of the middle control surface of the S-curved nozzle, where 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 S-bend nozzle inlet, the middle control surface, and the S-bend nozzle outlet. Draw splines from the S-bend nozzle inlet-middle control surface-S-bend nozzle outlet in sequence. The splines are tangent to the S-bend nozzle inlet and outlet, and 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 ratio of the radius of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d ;

[0068] S74, seven control lines τn Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is greater 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 surface in the bc section is greater than ε b-c Not less than 2, the radius 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 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, make a normal plane at each measuring point, intersect with the inner tube to get 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 the three sections;

[0075] is the nth control line τ n , the curvature radius 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 as follows:

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

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

[0084] A method for designing an aircraft engine nozzle is provided. The ultra-short-range nozzle is designed, and the aerodynamic performance and low-observability performance of the S-bend nozzle are taken into consideration. The method can effectively reduce aerodynamic losses while meeting the low-observability 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 Schematic diagram of determining the middle control surface curve of an S-bend nozzle provided in an embodiment of the present application;

[0087] Figure 3 This is a schematic diagram of determining the left and right edges of the middle control surface of an 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 an embodiment of the present application;

[0089] Figure 5 This is a schematic diagram provided by an embodiment of the present application, which takes a control point on a control line, divides the control line into three segments, takes measurement points, measures the curvature radius at each measurement point, and calculates the average curvature radius.

[0090] In order to better illustrate this 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 understood as limiting this application. DETAILED DESCRIPTION

[0091] To make the technical solution and its advantages of this application more clear, the technical solution of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only some of the embodiments of this application and are only used to explain this application, not to limit this application. It should be noted that for ease of description, only the parts relevant to this application are shown in the accompanying drawings, and other relevant 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 should have the usual meanings understood by those skilled in the art in the field to which this application belongs. The words indicating orientation used in the description of this application 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 means 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 stipulated 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] The comprehensive design of the engine S-bend nozzle by controlling the middle special-shaped surface, controlling the segmented curvature of the surface, and controlling the segmented contraction of the cross-sectional area along the flow direction is a feasible approach 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 order to solve 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 special-shaped to reduce the degree of bending of the inner tube. The curvature and cross-sectional area of ​​the inner tube are then controlled to reduce the aerodynamic loss of the low-detectability ultra-short-range nozzle and improve the thrust. Figure 1 shown.

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

[0096] If the S-bend nozzle relies solely on longitudinal or spanwise S-bend design, it is difficult to reduce the degree of inner tube curvature 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 and O1 of the inlet and outlet of the S-bend nozzle, draw a spline l0 tangent to the inlet and outlet planes.

[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 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] To improve low-observability performance, the S-bend nozzle outlet is designed to be reverse-beveled. Its outlet area is related to the engine's original axisymmetric nozzle outlet area, bevel angle, and nozzle total pressure loss. 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 engine's original axisymmetric nozzle outlet area;

[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 based on 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 rectifying 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 S-bend spray surface, 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 φ 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. Construct 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 surface ismid-0 The distance to the left is L1;

[0129] The distance between point P2 and the upper edge of the rectangle is D2, and the center point O of the middle control surface is 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 set to W, D1 is set to 0.9H, L2 is set to 0.5W, D2 is set to 0.2H,

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

[0133] The curve l2 is offset by D0 along the normal plane as the check line of the upper edge line l3 of the middle control surface of the S-bend nozzle. The upper edge line l3 of the middle control surface of the S-bend nozzle should not exceed the check line to meet the space layout requirements, where D0 is 1.2H.

[0134] 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:

[0135] 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;

[0136] The distance between point P5 and the lower edge of the rectangle is D5, and the center point O of the middle control surface is mid-0 The distance to the left is L5;

[0137] Point P6 is at a distance D6 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 right is L6;

[0138] 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.

[0139] 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.

[0140] S65, connecting points P3 and P6, as the control line l5, draw an arc line l6, which is 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, which is 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.

[0141] The point where the arc line l6 is tangent to the upper edge line l3 is between points P2 and P3.

[0142] 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.

[0143] 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 spline l8, as shown in Figure 3 shown.

[0144] 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.

[0145] 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 to obtain the middle control surface curve l mid ,like Figure 4 shown.

[0146] The area of ​​the intermediate control surface shall not exceed 5% of the inlet area of ​​the S-bend nozzle. The curved surface shape shall be moderately concave to reduce the degree of bending of the inner tube, and the concave arc shall not exceed 2°.

[0147] Step 7: Design the inner tube control line of the S-bend nozzle.

[0148] S71. Design seven control points at the S-bend nozzle inlet, the middle control surface, and the S-bend nozzle outlet. Draw splines from the S-bend nozzle inlet-middle control surface-S-bend nozzle outlet in sequence. The splines are tangent to the S-bend nozzle inlet and outlet, and seven control lines τ are obtained. n (n=1~7).

[0149] S72, on each control line τ n Take a control point at the 80% position of the control line and divide the control line into three segments, namely ab segment, bc segment, and cd segment, 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.

[0150] 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 , δc-d , calculate the ratio of the radius of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d .

[0151]

[0152] in,

[0153] δ is the average curvature radius of the inner tube of the S-bend nozzle in the three sections;

[0154] is the nth control line τ n , the curvature radius at the i-th measuring point on the three segments, take the three adjacent measuring points q i-1 ,q i ,q i+1 Draw an arc and measure its radius.

[0155]

[0156] in,

[0157] ε is the ratio of the curvature radius of the inner tube of the S-bend nozzle in the three sections;

[0158] D in is the inlet diameter of the S-bend nozzle.

[0159] 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 and recorded as Take any three adjacent points Draw an arc and measure the curvature radius of the arc The rest of the second to seventh control lines τ2, τ3, τ4, τ5, τ6, τ7, and so on, can be deduced to obtain the curvature radius of any three points of each control line in the ab segment, 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:

[0160]

[0161]

[0162] S74, seven control lines τ n Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is greater 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 surface in the bc section is greater than εb-c Not less than 2, the radius of the surface in the cd segment is ε c-d Not more than 6.

[0163] 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 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 .

[0164] S76, on the center line of the inner tube of the S-bend nozzle 1-1 Take m measuring points on the top, make a normal plane at each measuring point, intersect with the inner tube to get 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.

[0165] Step 8: Generate the S-bend nozzle profile.

[0166] The seven control lines τ in the inner tube of the S-bend nozzle n (n=1~7) is used as a guide line to generate the S-bend nozzle profile through the multi-section surface forming function.

[0167] The above embodiment discloses a method for designing an aircraft engine nozzle. First, the intermediate control surface is used as a core design element. This method has three effects on ultra-short-range nozzles: first, it increases the number of bounces of the electromagnetic incident wave in the cavity to improve the rearward low-detectability performance of the S-bend nozzle; second, it reduces the degree of inner tube bending and participates in the control of the inner tube curvature and area to reduce aerodynamic losses; and third, it reduces the S-bend offset, thereby achieving low-detectability shielding of the ultra-short-range S-bend nozzle and increasing the distance from the fuselage surface, thereby solving the problem of inner tube layout of the S-bend nozzle. Secondly, the S-bend nozzle is divided into three sections: bow, middle, and tail, starting from the middle control surface and the 80% centerline cross-section. The curvature and area distribution of the pipe are controlled in each section. The bow section is designed to achieve rapid partial shielding, with a rapid transition in cross-sectional shape and surface curvature. Excessive flow velocity in this section can lead to adverse phenomena such as flow separation and swirl, requiring a gradual change in controlled area to reduce the flow velocity. The middle section is a transitional section connecting the preceding and following sections, aiming to enhance shielding and pre-set accelerated expansion. This requires a rapid transition in surface curvature, but the area begins to converge rapidly. The tail section, with accelerated expansion and strong thrust as its primary goals, requires a rapid convergence in area, but a slow transition in surface curvature is required to avoid high-speed flow separation. Finally, designing the S-bend nozzle outlet with a reverse bevel can further improve the S-bend nozzle's radar scattering characteristics. It is important to note that the reverse bevel outlet should not cut off the S-bend nozzle throat to ensure that the S-bend nozzle's aerodynamic performance is not affected.

[0168] 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. The curved surface and the direction of the S-bend centerline are used to achieve full omnidirectional shielding of the engine turbine end face, and the S-bend nozzle is divided into three sections based on the intermediate control surface. The S-bend nozzle inlet-intermediate control surface is the head section, and the cross-sectional area decreases slowly and the cross-sectional shape transitions rapidly. The intermediate control surface-80% centerline position section is the middle section, and the cross-sectional area decreases at a moderate speed and the cross-sectional shape transitions rapidly. The 80% centerline position section-S-bend nozzle outlet is the tail section, and the cross-sectional area decreases rapidly and the cross-sectional shape transitions slowly.

[0169] The head of the S-bend nozzle is responsible for the rapid bending of the inner tube and the slow reduction of the area. Its curved surface 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. Its curved surface 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. Its curved surface radius ratio is not more than 6, and the area shrinkage is not less than 18%.

[0170] The above 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) within a space with an aspect ratio of less than 3.5D through segmented special-shaped design 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 low detectability requirements, but also reduce the curvature of the inner tube, effectively reducing the aerodynamic loss of the S-bend nozzle, and thus reducing the thrust loss of the S-bend nozzle.

[0171] The above 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" based on 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 surface transition caused by the special shape of the intermediate control surface is relatively complex, the cross-sectional area along the flow direction from the S-bend nozzle inlet-intermediate control surface-80% centerline position cross-sectional area is segmented to reduce aerodynamic losses.

[0172] 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 flow direction cross-sectional area variation pattern and the centerline transition form within the tube, thereby reducing aerodynamic losses caused by excessive curvature.

[0173] 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 replacements to the relevant technical features, and the technical solutions after these changes or replacements 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 centerline of the inner tube of the S-bend nozzle; Step 3: Determine the outlet area of ​​the S-bend nozzle; Step 4: Determine the shape of the S-bend nozzle outlet; 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 S-bend nozzle profile; Step seven includes: S71. Design seven control points at the S-bend nozzle inlet, the middle control surface, and the S-bend nozzle outlet. Draw splines from the S-bend nozzle inlet-middle control surface-S-bend nozzle outlet in sequence. The splines are tangent to the S-bend nozzle inlet and outlet, and 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 ratio of the radius of the inner tube of the S-bend nozzle in the three sections ε a-b , ε b-c , ε c-d ; S74, seven control lines τ n Adjust so that the radius of the inner tube of the S-bend nozzle in the ab section is greater 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 surface in the bc section is greater than ε b-c Not less than 2, the radius 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 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, make a normal plane at each measuring point, intersect with the inner tube to get 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.

2. The aircraft engine nozzle design method according to claim 1, characterized in that: In step 1, 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 is 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 and O1 of the inlet and outlet of the S-bend nozzle, draw a spline l0 tangent to the inlet and outlet planes; S22, a station point 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 aircraft engine nozzle design method 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 of 0 to 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 engine's original axisymmetric nozzle outlet area; 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 aircraft engine nozzle design method according to claim 6, characterized in that: In step 4, the outlet shape of the S-bend nozzle is designed to be a multi-segment arc shape, and the transition radius is not less than 120 mm.

8. The aircraft engine nozzle design method 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 ratio of the center point position of the S-bend spray middle surface; k is the correction coefficient.

9. The aircraft engine nozzle design method according to claim 8, characterized in that: In step 5, η2 is set to 0.5-0.6; 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. Construct 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 is mid-0 The distance to the left is L1; The distance between point P2 and the upper edge of the rectangle is D2, and the center point O of the middle control surface is 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; The value of L1 is W, the value of D1 is 0.9H, the value of L2 is 0.5W, the value of D2 is 0.2H, the value of L3 is 0.9W, and the value of 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 is mid-0 The distance to the left is L5; Point P6 is at a distance D6 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 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 the control line l5, draw an arc line l6, which is 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, which is 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 form a spline, which is tangent to the lower edge line l4 of the middle control surface of the S-bend nozzle and the arc line l6 to obtain 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 to obtain 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 along the normal plane by D0 to serve as the verification line of the upper edge line l3 of the middle control surface of the S-bend nozzle, where D0 is 1.2H.

12. The aircraft engine nozzle design method according to claim 11, 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 the three sections; is the nth control line τ n , the curvature radius at the i-th measurement point on the three segments.

13. The aircraft engine nozzle design method according to claim 12, characterized in that: In S73, calculate the radius ratio ε of the inner tube of the S-bend nozzle in the 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.

14. The aircraft engine nozzle design method according to claim 13, characterized in that: Step 8 is as follows: The seven control lines τ in the inner tube of the S-bend nozzle n (n=1~7) is used as a guide line to generate the S-bend nozzle profile through the multi-section surface forming function.

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