Helicopter particle separator parameterization design method

Abstract

The invention discloses a parameterization design method for a helicopter particle separator, which comprises the following steps of: firstly, setting a control point at a key position, and constructing a central body contour of the separator by using a cubic Hermite interpolation polynomial with a weight addition item; thirdly, reversely deducing partial molded lines of the outer wall surface of the core area and the fork according to the sectional areas of the key positions such as the inlet, the fork and the throat of the separator; then, control points are added again, a complete outer wall face contour curve is generated in combination with a cubic Hermite interpolation polynomial with weight items, and meanwhile design of a fork curve is completed in combination with an arc and a tangent. According to the method, the structural design requirement of the particle separator can be met, the change trend of the internal pressure gradient of the particle separator can be accurately controlled, flexible adjustment of key geometric parameters is supported, and therefore efficient parameterization design and optimization of the particle separator are achieved.

Description

Technical Field

[0001] The present invention relates to the field of aircraft design, and particularly to a parametric design method for a helicopter particle separator. Background Art

[0002] As a vertical take-off and landing aircraft, a helicopter often operates in various complex environments. When a helicopter operates in an environment rich in particles such as deserts and seas, especially when the engine takes off and lands near full power, a large amount of high-inertia particle flow is usually inhaled. If no protection measures are taken for the engine, these particles will cause very serious damage to the engine. For example, the compressor blades will be corroded, resulting in a decrease in engine power. In severe cases, the engine blades will stall; the cooling channels of the turbine blades are easily blocked by particles, posing a danger of overheating of the turbine blades; and even an in-flight engine shutdown may occur. Therefore, in order to better protect the helicopter engine, it is particularly important to develop an effective intake system protection device.

[0003] Due to the advantages of high air flow rate per unit area, low resistance, easy integration with the engine, and small pressure distortion, inertial particle separators are expected to be widely used in the field of helicopter intake protection. At present, there is a lack of research on efficient design methods for particle separators, and existing methods often have difficulty taking into account the requirements of structural constraints, aerodynamic performance, and parametric adjustment. Therefore, it is particularly important to develop an efficient design method for helicopter particle separators. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a parametric design method for a helicopter particle separator. This method realizes the parametric design of the helicopter particle separator by reasonably arranging control points, optimizing the angles of the profiles at key positions, and controlling the areas of key cross-sections, and can take into account the requirements of structural constraints, aerodynamic performance, and parametric adjustment of the helicopter particle separator.

[0005] Technical Solution: To achieve the above object, a parametric design method for a helicopter particle separator provided by the present invention includes the following steps:

[0006] 1) According to the structural constraints and dimensional specifications of the particle separator, establish the control points of the central body and preset the slopes of the central body contour curves at each control point;

[0007] 2) Construct a cubic Hermite interpolation polynomial curve and introduce a weight term; adjust the curve shape by adjusting the weight factor in the weight term;

[0008] 3) Use the cubic Hermite interpolation polynomial with the weight term constructed in step 2) to connect the control points determined in step 1) and draw the contour of the central body of the helicopter particle separator;

[0009] 4) Locate the positions of the outer wall surfaces at the inlet and outlet of the particle separator, and determine the cross-sectional area at the throat position; following the predetermined area change law, inversely deduce the outer wall profile at the key positions; subsequently, use the cubic Hermite interpolation polynomial with weight terms constructed in step 2) to smoothly connect the outer wall profile at the key positions with the positions at the inlet and outlet, and finally complete the overall design of the outer wall of the helicopter particle separator;

[0010] 5) Based on the geometric characteristics of the outlet of the particle separator, determine the endpoint positions of the main flow channel outlet, and design the cross-sectional area at the bifurcation according to the flow parameters; according to the corresponding relationship between the outlet area and the bifurcation area, inversely deduce the lower wall profile of the particle separator; a circular arc and a tangent are used at the front end of the bifurcation for smooth transition, and at the same time, the control points of the upper wall endpoints of the bifurcation are determined according to the dimensions of the throat and the outlet of the swept flow channel, and smooth connection is carried out through the cubic Hermite interpolation polynomial with weight terms in step 2), and finally complete the profile design of the bifurcation;

[0011] 6) Splice the profiles of the central body, the outer wall and the bifurcation to complete the design of the meridian plane of the particle separator, and construct the three-dimensional geometric model of the helicopter particle separator by rotating to generate a rotational body structure, and finally realize the overall design of the particle separator.

[0012] Further, in step 2), establish a cubic Hermite interpolation polynomial curve, and the functional form of the cubic Hermite interpolation polynomial curve is:

[0013]

[0014] where \(x_0,y_0\) represent the coordinates of the starting point, \(x_1,y_1\) represent the coordinates of the ending point, \(m_0\) is the slope at the starting point, and \(m_1\) is the slope at the ending point; add a weight term \(t\) is the weight parameter; the final functional form is \(F(x)=H_3(x)+W(x)\).

[0015] Further, in step 1), according to the structural constraints and dimensional specifications of the particle separator, establish the control points \([P_0,P_1,P_2,P_3,P_4,P_5,P_6]\) for designing the central body, where \(P_0\) is the starting point of the central body, \(P_1\) is the starting point of the first area transition region of the central body, \(P_2\) is the position point of the central body at the throat of the particle separator, \(P_3\) is the vertex of the central body, \(P_4\) is the end point of the third area transition region, \(P_5\) is the control point of the central body at the main flow channel bifurcation, \(P_6\) is the end point of the central body, and determine the slopes \([K_0,K_1,K_2,K_3,K_4,K_5,K_6]\) of the central body contour curve at each control point.

[0016] Further, in step 3), according to the cubic Hermite interpolation polynomial function relationship with weight terms established in step 2), the control points [P0, P1, P2, P3, P4, P5, P6] determined in step 1) are combined with their corresponding slopes [K0, K1, K2, K3, K4, K5, K6]; for smooth connection, the weight parameter t of each curve segment is adjusted to change the shape of that curve segment; subsequently, each generated curve segment L P0P1 , L P1P2 , L P2P3 , L P3P4 , L P4P5 , L P5P6 are spliced to finally form a complete central body contour curve L_ZXT = [L P0P1 , L P1P2 , L P2P3 , L P3P4 , L P4P5 , L P5P6 ; thus, the geometric design of the central body is completed.

[0017] Further, in step 4), according to the geometric structure constraints of the outer wall surface of the particle separator, the coordinates at the starting position W0 of the outer wall surface and the slope of its profile line are determined, and the areas at the key sections P1_W1, P3_3, P4_W4, and the throat P2_W2 are determined according to the aerodynamic performance requirements; where W1, W2, W3, and W4 are the intersection points of the lines perpendicular to the tangents at the points on the central body curve where P1, P2, P3, and P4 are located with the outer wall surface respectively. Subsequently, according to the specified area change law, the areas at the intermediate section positions between the four sections are smoothly transitioned, and the outer wall surface curves L W1W2 , L W2W3 , L W3W4 are obtained by inverse calculation using the area formula; according to the size of the downstream scavenging volute of the particle separator, the outer contour end point P6 is designed, and a transition point P5 that fits the outer contour shape is provided between P4 and P6. The other parts are smoothly connected using the cubic Hermite interpolation polynomial method with weight terms in step 2) to generate curves L W0W1 , L W4W5 , L W5W6 ; finally, the curves are connected in sequence to generate the outer wall surface curve L_WZ = [L W0W1 , L W1W2 , L W2W3 , L W3W4 , L W4W5 , L W5W6 , thus completing the geometric design of the outer wall surface.

[0018] Further, in step 5), according to the flow information, the cross-sectional area of the particle separator at the bifurcation is designed, and in combination with the relationship between the outlet area and the bifurcation area, the profile line L of the lower wall surface of the bifurcation of the particle separator is deduced inversely. F0F1 The leading edge position of the bifurcation is designed with a smooth connection using an arc and its tangent to generate the curve L. F2F3 Meanwhile, according to the dimensions of the throat of the particle separator and the scavenging volute, the control point F5 of the upper wall surface of the bifurcation is determined, the control point F4 is added between points F3 and F5, and through the cubic Hermite interpolation polynomial method with a weight term in step 2), the control points are smoothly connected to generate the curve L. F1F2 , L F3F4 , L F4F5 , finally, the curves are connected in sequence to generate the outer wall surface curve L_FZK = [L F0F1 , L F1F2 , L F2F3 , L F3F4 , L F4F5 , thus completing the geometric design of the bifurcation.

[0019] Further, in step 6), the profile lines of the central body, the outer wall surface and the bifurcation are spliced to complete the design of the meridian plane of the particle separator; and a rotary body structure is generated by rotating around the central axis, thereby completely constructing the three-dimensional geometric model of the helicopter particle separator and finally realizing the overall design of the particle separator.

[0020] Further, in step 4), the process of inversely obtaining the outer wall surface curves L W1W2 , L W2W3 , L W3W4 is as follows:

[0021] Establish the relationship between the cross-sectional area and the flow channel height L:

[0022] S(i) = π * L(i)(Y zxt (i) + L(i) * cos(theta(i))

[0023] where Y zxt (i) is the ordinate of the i-th point on the specified curve on the central body; theta(i) is the slope at the i-th point on the specified curve on the central body, S(i) is the area of the i-th cross-section, and L(i) is the flow channel height of the i-th cross-section;

[0024] Perform iterative calculation on L(i) by the Newton iteration method;

[0025] Calculate the points on the corresponding profile line of the outer wall surface, and the calculation formula is as follows:

[0026] X W (i) = Xzxt (i) + L(i) * cos(90 - theta(i))

[0027] Y W (i) = Y zxt (i) + L(i) * sin(90 - theta(i))

[0028] Where X W (i) is the abscissa of the i-th point on the specified curve of the outer wall surface, and Y W (i) is the ordinate of the i-th point on the specified curve of the outer wall surface.

[0029] Furthermore, in step 5), the specific method for designing the leading edge position of the bifurcation using an arc and a tangent is as follows:

[0030] According to the specific requirements of the particle separator design, determine the center position (x c , y c ) of the arc; and the positions of the two tangent points (x t1 , y t1 ), (x t2 , y t2 ); the positions of the two tangent points are expressed as

[0031] x t1 = x c + Rcos(theta1)

[0032] y t1 = y c + Rcos(theta1)

[0033] x t2 = x c + Rcos(theta2)

[0034] y t2 = y c + Rcos(theta2)

[0035] Where R is the radius of the circle, and theta1 and theta2 are the angular values of the positions on the circle where the tangent points are located;

[0036] Calculate the coordinates of the other endpoints (x t11 , y t11 ) and (x t22 , y t22 ) of the two tangents corresponding to the two tangent points. The calculation formula is:

[0037] x t11 = x t1 - n1cos(theta1 + 90)

[0038] yt11 = y t1 -n1sin(theta1 + 90)

[0039] x t22 = x t2 -n2cos(theta2 + 90)

[0040] y t22 = y t2 -n2sin(theta2 + 90)

[0041] where n1 and n2 are the lengths of two tangent lines respectively; generating curve L stc1 [(x t1 , y t1 ), (x t11 , y t11 )] and curve L stc2 [(x t2 , y t2 ), (x t22 , y t22 )];

[0042] The points on the circular arc curve are generated using the following formula:

[0043] theta(j) = theta1 + (theta(2) - theta(1)) * C(j)

[0044] where theta(j) is the angle of the j-th point on the circular arc on the circle, C is a function with a value range of [0, 1] and evenly distributed, and C(j) is the j-th value of this function; x cir (j) is the abscissa of the j-th point on the circular arc, and y cir (j) is the ordinate of the j-th point on the circular arc; generating curve L stc2 [x cir , y cir ;

[0045] These three curves are spliced to generate the leading edge curve L F2F3 of the bifurcation, and the two endpoints of this curve are named F2 and F3 respectively.

[0046] Furthermore, in step 5), the method of smoothly connecting the control points using the cubic Hermite interpolation polynomial method with weight terms in step 2) is as follows:

[0047] Connect F1 and F2 to generate a curve Subsequently, the control point F5 of the bifurcation at the outlet position of the scavenging air flow passage is confirmed according to the size and position of the outlet of the scavenging air flow passage. To enable more flexible design, a control point F4 is added between F3 and F5, and its specific position can be determined according to specific design requirements. Subsequently, points F3 and F4 are connected. At this time, the abscissa and ordinate at F3 are substituted into x0 and y0 in the formula F(x) in step 2), the abscissa and ordinate at F4 are substituted into x1 and y1 in F(x), and the slope at F3 is substituted into m0 in F(x), and the slope at F4 is substituted into m1 in F(x), obtaining the curve L connecting F3 and F4 F3F4 Connect points F4 and F5 to generate a curve using the same method Finally are spliced to complete the generation of the bifurcation curve

[0048] Beneficial effects: The parametric design method proposed by the present invention, by introducing a cubic Hermite interpolation polynomial with a weight term and combining the inverse deduction of key geometric parameters and smooth connection technology, can not only meet the structural design requirements of the particle separator, but also precisely control its internal flow field characteristics (such as the pressure gradient change trend), and support flexible adjustment of key geometric parameters, taking into account the structural constraints, aerodynamic performance, and parametric adjustment requirements of the helicopter particle separator. This method provides an efficient solution for the design and optimization of helicopter particle separators Brief Description of the Drawings

[0049] Figure 1 is a schematic diagram of the flow passage structure of a typical particle separator

[0050] Figure 2 is the cubic interpolation polynomial curve with weights adopted by the present invention

[0051] Figure 3 is the curve for controlling the area change law adopted by the present invention

[0052] Figure 4 is a schematic diagram of the generation of the leading edge of the bifurcation of the particle separator of the present invention

[0053] Figure 5 is a schematic diagram of the generation of the meridian plane of the particle separator of the present invention

[0054] Figure 6 is a schematic diagram of the three-dimensional model of the particle separator finally generated by the present invention Detailed Embodiment

[0055] The present invention will be further described in detail below with reference to the drawings and specific embodiments

[0056] The structure of a typical particle separator flow channel is as follows Figure 1 shown (for intuitive display, the main body of the particle separator is shown in cross-section). It includes a central body, an outer wall surface, and a bifurcation port. Among them, the main flow channel area between the bifurcation port and the central body is connected to the engine at the back, and the scavenging flow channel formed between the bifurcation port and the outer wall surface is connected to the scavenging volute at the back.

[0057] Based on the basic configuration of this particle separator, the present invention provides a parametric design method for a helicopter particle separator, which can adjust the local shape of the particle separator on the basis of this basic configuration to meet the required design requirements. The design method of the present invention includes the following steps:

[0058] 1). According to the structural constraints and dimensional specifications of the particle separator, establish the control points [P0, P1, P2, P3, P4, P5, P6] for designing the central body, where P0 is the starting point of the central body of the particle separator, P1 is the starting point of the first area transition region of the central body, P2 is the point where the central body is located at the throat position of the particle separator, P3 is the vertex of the central body, P4 is the end point of the third area transition region of the central body, P5 is the control point of the central body at the position of the main flow channel bifurcation port, and P6 is the end point of the central body of the particle separator. And pre-determine the slopes [K0, K1, K2, K3, K4, K5, K6] of the central body contour curve at each control point according to the actual design requirements and experience in advance; provide accurate initial conditions for the subsequent geometric design of the central body.

[0059] 2). Establish a cubic Hermite interpolation polynomial curve, and its function form is:

[0060]

[0061] where x0, y0 represent the coordinates of the starting point of the curve, x1, y1 represent the coordinates of the end point of the curve, m0 is the slope of the starting point, m1 is the slope of the end point, x is the abscissa of the cubic Hermite interpolation polynomial curve. In addition, add a weight term after this curve function where t is the weight parameter; the final function form of the curve is F(x) = H3(x) + W(x). This function can smoothly connect them under the condition of knowing the two end points and their slopes, and change the trend of the curve by adjusting the weight parameter, as Figure 2 shown.

[0062] 3). Using the cubic Hermite interpolation polynomial function relationship with weight terms established in step 2), smooth connection is performed on the control points [P0, P1, P2, P3, P4, P5, P6] determined in step 1), combined with their corresponding slopes [K0, K1, K2, K3, K4, K5, K6]. Taking the P0, P1 segment as an example, at this time, the abscissa and ordinate at P0 are substituted into x0 and y0 in the formula F(x) in step 2), the abscissa and ordinate at P1 are substituted into x1 and y1 in F(x), the slope K1 at P1 is substituted into m0 in F(x), and the slope K2 at P2 is substituted into m1 in F(x), then the curve L connecting P0 and P1 can be obtained. P0P1 According to the actual design requirements, the weight parameter t of the curve is adjusted to achieve flexible control of the curve shape. Subsequently, each segment of the curve L generated successively through the above steps P0P1 , L P1P2 , L P2P3 , L P3P4 , L P4P5 , L P5P6 are spliced, and finally the complete central body contour curve L_ZXT = [L P0P1 , L P1P2 , L P2P3 , L P3P4 , L P4P5 , L P5P6 is formed.

[0063] 4). According to the geometric and structural limitations of the outer wall surface of the particle separator, determine the coordinates of the starting position W0 of the outer wall surface and the slope K of the profile line W0 , and according to the pneumatic requirements, determine the areas of the key sections P1W1, P3W3, P4W4 and the throat P2W2; where W1, W2, W3 and W4 are the intersection points of the straight lines perpendicular to the tangents at the points where P1, P2, P3 and P4 are located on the central body curve and the outer wall surface respectively. Subsequently, according to the specified area change rule, the areas at the middle section positions of the four sections are smoothly transitioned, and the area transition curve is selected as:

[0064] y = (-1 - 0.5n)x 4 +nx 3 +(2 - 0.5n)x 2

[0065] where x is the abscissa and y is the ordinate, as Figure 3 shown; n is a parameter that controls the trend of the curve, which can make the curve change from steep first and then gentle, transition to gentle and steep equally, and then gentle first and then steep, and its value range is [0, 1], as Figure 3 shown.

[0066] The area transition formula between two adjacent transition cross-sections is as follows:

[0067] S j = S s + (S s - S e ) * y(j)

[0068] where S s is the area of the starting cross-section, S e is the area of the terminating cross-section, S j is the area of the j-th cross-section between the two cross-sections, and y(j) is the ordinate of the j-th point on the transition curve.

[0069] Subsequently, based on the areas of each cross-section and the curves L2, L3, and L4 on the central body, the outer wall curves L W1W2 , L W2W3 , and L W3W4 are inversely calculated, and the solution method is as follows:

[0070] The process of inversely calculating the outer wall curve is as follows:

[0071] 1. Establish the relationship between the cross-sectional area and the flow channel height L:

[0072] S(i) = π * L(i)(Y zxt (i) + L(i) * cos(theta(i))

[0073] where Y zxt (i) is the ordinate of the i-th point on the specified curve on the central body (such as the curve from P0 to P1); theta(i) is the slope at the i-th point on the specified curve on the central body, S(i) is the area of the i-th cross-section, and L(i) is the flow channel height of the i-th cross-section.

[0074] 2. Iteratively calculate L(i) by the Newton iteration method

[0075] 3. Calculate the points on the profile of the corresponding outer wall, and the calculation formula is as follows:

[0076] X W (i) = X zxt (i) + L(i) * cos(90 - theta(i))

[0077] Y W (i) = Y zxt (i) + L(i) * sin(90 - theta(i))

[0078] where X W (i) is the abscissa of the point on the specified curve of the outer wall (such as the curve from W1 to W2), and Y W(i) Specify the ordinate of the point on the curve for the outer wall surface.

[0079] Generate the curves L W1W2 , L W2W3 , L W3W4 respectively by the above method; Connect between W0 and W1 by the method in step 2). At this time, substitute the abscissa and ordinate at W0 into x0 and y0 in the formula F(x) in step 2), substitute the abscissa and ordinate at W1 into x1 and y1 in F(x), and substitute the slope at W0 into m0 in F(x), substitute the slope at W1 into m1 in F(x), then the curve L connecting W0 and W1 can be obtained W0W1 , and adjust the weight parameter t of the curve according to the actual design requirements to achieve flexible control of the curve shape. Then, design the end point W6 of the outer wall surface according to the size of the scavenging volute downstream of the particle separator, and design the transition point W5 between W4 and W6. Connect between W4 and W5, and between W5 and W6 by the same method as connecting W0 and W1 to generate the curves L W4W5 , L W5W6 ; Finally, connect the curves in sequence to generate the outer wall surface curve L_WZ = [L W0W1 , L W1W2 , L W2W3 , L W3W4 , L W4W5 , L W5W6 .

[0080] 5). Set the control point F0 at the outlet position of the bifurcation according to the size of the mainstream channel outlet of the particle separator, design the cross-sectional area of the particle separator at the bifurcation according to the flow rate information (i.e., the cross-sectional area of the particle separator between the point P5 on the central body and the point F1 on the bifurcation), and back-calculate the first curve from the mainstream channel outlet of the particle separator to the bifurcation according to the outlet area and the area at this place and name the other end point of this curve F1. The method of generating the curve is the same as the method of inversely calculating the outer wall surface profile according to the area in step 4); Then design the leading edge position of the bifurcation by using an arc and a tangent line, as Figure 4 shown. The specific method is as follows:

[0081] 1. Determine the center position (x c , y c ) of the arc according to the specific requirements of the particle separator design; and the positions of the two tangent points (x t1 , y t1 ), (x t2 , y t2 ); The positions of the two tangent points can be expressed as

[0082] x t1 = xc +Rcos(theta1)

[0083] y t1 =y c +Rcos(theta1)

[0084] x t2 =x c +Rcos(theta2)

[0085] y t2 =y c +Rcos(theta2)

[0086] where R is the radius of the circle, and theta1 and theta2 are the angular values of the positions on the circle where the tangent points are located, respectively.

[0087] 2. Calculate the coordinate calculation formulas for the other endpoints (x t11 , y t11 ) and (x t22 , y t22 ) of tangent 1 and tangent 2 as follows:

[0088] x t11 =x t1 -n1cos(theta1 + 90)

[0089] y t11 =y t1 -n1sin(theta1 + 90)

[0090] x t22 =x t2 -n2cos(theta2 + 90)

[0091] y t22 =y t2 -n2sin(theta2 + 90)

[0092] where n1 and n2 are the lengths of tangent 1 and tangent 2, respectively; generate curve L stc1 [(x t1 , y t1 ), (x t11 , y t11 )] and curve L stc2 [(x t2 , y t2 ), (x t22 , y t22 )].

[0093] 3. Generate the points on the circular arc curve using the following formula:

[0094] theta(j) = theta1 + (theta(2) - theta(1)) * C(j)

[0095] where theta(j) is the angle of the j-th point on the circular arc on the circle, C is a function with a value range of [0, 1] and uniformly distributed, and C(j) is the j-th value of this function; x cir (j) is the abscissa of the j-th point on the circular arc, and y cir (j) is the ordinate of the j-th point on the circular arc; generate the curve L stc2 [x cir , y cir .

[0096] 4. splice these three curves to generate the leading edge curve of the bifurcation The two endpoints of this curve are named F2 and F3 respectively.

[0097] Connect F1 and F2 using the formula in step 2) to generate the curve L F1F2 ; then confirm the control point F5 of the bifurcation position at the outlet of the swept air flow channel according to the size and position of the outlet of the swept air flow channel. In order to enable more flexible design, add a control point F4 between F3 and F5, and its specific position can be determined according to specific design requirements. Then use the method in step 2) to connect the points F3 and F4. At this time, substitute the abscissa and ordinate at F3 into x0 and y0 in the formula F(x) in step 2), substitute the abscissa and ordinate at F4 into x1 and y1 in F(x), and substitute the slope at F3 into m0 in F(x), substitute the slope at F4 into m1 in F(x), then the curve L connecting F3 and F4 can be obtained F3F4 , use the same method to connect the points F4 and F5 to generate the curve Finally splice them to complete the generation of the bifurcation curve

[0098] 6) splice the profile lines of the central body, outer wall surface and bifurcation to complete the design of the meridian plane of the particle separator; its schematic diagram is as Figure 5 shown and rotate it around the central axis to generate a rotary body structure, thus completely constructing the three-dimensional geometric model of the helicopter particle separator, and finally realizing the overall design of the particle separator. The three-dimensional model of the particle separator is as Figure 6 shown.

Claims

1. A parametric design method for a helicopter particle separator, characterized in that: The following steps are involved: 1) According to the structural constraints and size specifications of the particle separator, the control points of the central body are established, and the slope of the central body contour curve at each control point is preset; 2) Construct a cubic Hermite interpolation polynomial curve and introduce a weight term; adjust the curve shape by adjusting the weight factor in the weight term; 3) using the cubic Hermite interpolation polynomial with weight terms constructed in step 2), connecting the control points determined in step 1) in series to draw the outline of the helicopter particle separator center body; 4) Locate the positions of the outer wall at the inlet and outlet of the particle separator, and determine the cross-sectional area at the throat position; follow the predetermined area change law to reversely deduce the outer wall profile at the key position; then, use the cubic Hermite interpolation polynomial with weight terms constructed in step 2) to smoothly connect the outer wall profile at the key position with the positions at the inlet and outlet, and finally complete the overall design of the outer wall of the helicopter particle separator; 5) Based on the geometric characteristics of the particle separator outlet, determine the endpoint position of the main channel outlet, and design the cross-sectional area at the bifurcation in combination with the flow parameters; according to the corresponding relationship between the outlet area and the bifurcation area, inversely deduce the lower wall profile of the particle separator; The front end of the bifurcation uses arcs and tangents to achieve smooth transition. At the same time, the control points of the upper wall endpoints of the bifurcation are determined according to the size of the throat and the scavenging flow channel outlet, and are smoothly connected through the cubic Hermite interpolation polynomial with weight terms in step 2), and finally the bifurcation profile design is completed; 6) The three parts of the center body, outer wall and bifurcation are spliced ​​together to complete the design of the meridian plane of the particle separator, and the three-dimensional geometric model of the helicopter particle separator is constructed by rotating the generated rotating body structure to finally realize the overall design of the particle separator.

2. The helicopter particle separator parameter design method according to claim 1, characterized in that: In step 2), a cubic Hermite interpolation polynomial curve is established, and the function form of the cubic Hermite interpolation polynomial curve is: Where x0, y0 represent the coordinates of the starting point, x1, y1 represent the coordinates of the end point, m0 is the slope of the starting point, and m1 is the slope of the end point; add weight items t is the weight parameter; the final function is in the form of F(x)=H3(x)+W(x).

3. The helicopter particle separator parameterized design method according to claim 2, characterized in that: In step 1), according to the structural constraints and size specifications of the particle separator, the control points of the design center body [P0, P1, P2, P3, P4, P5, P6] are established, where P0 is the starting point of the center body, P1 is the starting point of the first area transition area of ​​the center body, P2 is the position point of the center body at the throat of the particle separator, P3 is the vertex of the center body, P4 is the end point of the third area transition area, P5 is the control point of the center body at the bifurcation of the main channel, P6 is the end point of the center body, and the slope of the center body contour curve at each control point is determined [K0, K1, K2, K3, K4, K5, K6].

4. The helicopter particle separator parameterized design method according to claim 3, characterized in that: In step 3), according to the cubic Hermite interpolation polynomial function relationship with weight terms established in step 2), the control points [P0, P1, P2, P3, P4, P5, P6] determined in step 1) are smoothly connected in combination with their corresponding slopes [K0, K1, K2, K3, K4, K5, K6], and the weight parameter t of each curve segment is adjusted to change the shape of the curve segment; then, the generated curve segments L P0P1 ,L P1P2 ,L P2P3 ,L P3P4 ,L P4P5 ,L P5P6 Splicing is performed to finally form a complete central body contour curve L_ZXT=[L P0P1 ,L P1P2 ,L P2P3 ,L P3P4 ,L P4P5 ,L P5P6 ]; Complete the geometric design of the central body.

5. The helicopter particle separator parameterized design method according to claim 4, characterized in that: Step 4) According to the geometric structure limitation of the outer wall of the particle separator, determine the coordinates of the starting position W0 of the outer wall and the slope of its profile, and determine the areas of the key sections P1_W1, P3_3, P4_W4 and the throat P2_W2 according to the aerodynamic performance requirements; wherein W1, W2, W3 and W4 are the intersection points of the straight lines of the tangents to the points P1, P2, P3 and P4 on the vertical center body curve and the outer wall surface, and then, according to the specified area change law, the areas at the middle section positions of the four sections are smoothly transitioned, and the outer wall curve L is inversely calculated by the area formula. W1W2 , L W2W3 , L W3W4 According to the size of the scavenging volute downstream of the particle separator, the end point P6 of the outer contour is designed, and a transition point P5 that adapts to the outer contour shape is provided between P4 and P6. The other parts are smoothly connected using the cubic Hermite interpolation polynomial method with weight terms in step 2) to generate a curve L W0W1 , L W4W5 , L W5W6 ; Finally, connect the curves in order to generate the outer wall curve L_WZ = [L W0W1 , L W1W2 , L W2W3 , L W3W4 , L W4W5 , L W5W6 ] to complete the geometric design of the outer wall.

6. The helicopter particle separator parameterized design method according to claim 5, characterized in that: In step 5), the cross-sectional area of ​​the particle separator at the fork is designed according to the flow information, and the profile L of the lower wall of the fork of the particle separator is inferred by combining the relationship between the outlet area and the fork area. F0F1 ; The front edge of the fork is designed to achieve smooth connection using an arc and its tangent to generate a curve L F2F3 At the same time, the control point F5 on the upper wall of the bifurcation is determined according to the size of the particle separator throat and the scavenging volute, and the control point F4 is added at points F3 and F5. The control points are smoothly connected by the cubic Hermite interpolation polynomial method with weight terms in step 2) to generate the curve L F1F2 ,L F3F4 ,L F4F5 Finally, connect the curves in order to generate the outer wall curve L_FZK = [L F0F1 , L F1F2 , L F2F3 , L F3F4 , L F4F5 ], completing the geometric design of the bifurcation.

7. The helicopter particle separator parameterized design method according to claim 6, characterized in that: In step 6), the three parts of the center body, the outer wall and the bifurcation are spliced ​​to complete the design of the meridian plane of the particle separator; and the rotating body structure is generated around the central axis, thereby completely constructing the three-dimensional geometric model of the helicopter particle separator, and finally realizing the overall design of the particle separator.

8. The helicopter particle separator parameterized design method according to claim 5, characterized in that: In step 4), the outer wall curve L is obtained by inversely calculating the area formula W1W2 , L W2W3 , L W3W4 The process is: Establish the relationship between the cross-sectional area and the flow channel height L: S(i)=π*L(i)(Y zxt (i)+L(i)*cos(theta(i)) where Y zxt (i) is the ordinate of the i-th point on the specified curve on the center body; theta(i) is the slope of the i-th point on the specified curve on the center body, S(i) is the area of ​​the i-th section, and L(i) is the flow channel height of the i-th section; Iterate the calculation of L(i) by Newton iteration method; Calculate the points on the corresponding outer wall surface, where the calculation formula is as follows: X W (i)=X zxt (i)+L(i)*cos(90-theta(i)) Y W (i)=Y zxt (i)+L(i)*sin(90-theta(i)) Where X W (i) is the horizontal coordinate of point i on the specified curve of the outer wall, Y W (i) is the ordinate of point i on the specified curve of the outer wall.

9. The helicopter particle separator parameterized design method according to claim 6, characterized in that: In step 5), the front edge position of the fork is then designed using arcs and tangents. The specific method is as follows: According to the specific requirements of the particle separator design, determine the center position of the arc (x c ,y c ); and the locations of the two tangent points The two tangent points are represented as Where R is the radius of the circle, theta1 and theta2 are the angle values ​​of the position of the tangent point on the circle; Calculate the other endpoints of the two tangent lines corresponding to the two tangent points and The coordinate calculation formula is: Where n1 and n2 are the lengths of the two tangent lines respectively; the resulting curve and curve The following formula is used to generate points on the arc curve: theta(j)=theta1+(theta(2)-theta(1))*C(j) where theta(j) is the angle of the jth point on the arc on the circle, C is a function with a range of [0,1] and uniform distribution, and C(j) is the jth value of the function; x cir (j) is the horizontal coordinate of the jth point on the arc, y cir (j) is the ordinate of the jth point on the arc; the generated curve L stc2 [x cir ,y cir ]; The three curves are spliced ​​to generate the fork front curve The two endpoints of the curve are named F2 and F3.

10. The helicopter particle separator parameterized design method according to claim 9, characterized in that: In step 5), the method of smoothly connecting the control points is as follows: Connect F1 and F2 to generate a curve Then, according to the size and position of the scavenging flow channel outlet, the control point F5 of the fork in the scavenging flow channel outlet is confirmed. In order to make the design more flexible, a control point F4 is added between F3 and F5. Its specific position can be determined according to the specific design requirements. Then, points F3 and F4 are connected. At this time, the horizontal coordinate and vertical coordinate at F3 are substituted into x0, y0 in the formula F(x) in step 2), and the horizontal coordinate and vertical coordinate at F4 are substituted into x1, y1 in F(x). The slope at F3 is substituted into m0 in F(x), and the slope at F4 is substituted into m1 in F(x). The curve L connecting F3 and F4 is obtained. F3F4 , connect points F4 and F5 in the same way to generate the curve Finally Splice to complete the generation of the bifurcation curve

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