Blade capable of reducing stall and design method

Abstract

The invention relates to a blade capable of reducing stall and a design method, and relates to the technical field of impellers, the blade comprises a front edge section and a main body section, and the front edge section and the main body section are connected through an elastic piece. The impeller has the advantages that the flow separation phenomenon under the large-flow working condition is effectively restrained, and the working stability and efficiency of the blades are improved.

Description

Technical Field

[0001] This application relates to the technical field of impellers, and in particular to a blade and design method for reducing stall. Background Technology

[0002] Centrifugal pumps commonly face flow stall problems when operating at high flow rates, manifesting as a sharp drop in efficiency, increased pressure pulsation, and intensified vibration and noise; in severe cases, it can even cause structural damage to the pump body. Traditional centrifugal pump impellers are designed specifically for the target operating conditions, and when the flow rate increases, stall and vortex phenomena can occur. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, one of the purposes of this application is to provide a blade and design method to reduce stall, which has the advantages of effectively suppressing flow separation under high flow conditions and improving the blade's working stability and efficiency.

[0004] The above-mentioned objective of this application is achieved through the following technical solution:

[0005] A blade for reducing stall includes a leading edge section and a main body section, the leading edge section and the main body section being connected by an elastic element.

[0006] By adopting the above technical solution, the flow resultant force on the leading edge of the blade changes under high flow conditions, causing the leading edge section of the blade to automatically increase the inlet placement angle, effectively suppressing the flow separation phenomenon under high flow conditions, and improving the working stability and efficiency of the blade.

[0007] In a preferred embodiment, the present application may be further configured such that the elastic element includes an elastic body one and an elastic body two, the elastic body one being located on the pressure surface and the elastic body two being located on the suction surface, and the elastic modulus of the elastic body two being greater than the elastic modulus of the elastic body one.

[0008] By adopting the above technical solution, and through the different deformation amounts of the pressure surface elastomer one and the suction surface elastomer two, the inlet placement angle of the blade leading edge section can be adjusted to better adapt to the working conditions, thereby optimizing the flow characteristics under different working conditions and achieving the goal of reducing stall.

[0009] In a preferred embodiment, this application may be further configured such that the leading edge segment and the main body segment are hinged together, with one elastic body located on one side of the hinge point and the other elastic body located on the other side of the hinge point.

[0010] By adopting the above technical solution, the existence of the hinge point allows the leading edge segment to rotate around the point at a certain angle, resulting in better stability of the leading edge segment.

[0011] This application also discloses a blade design method to reduce stall, comprising the following steps:

[0012] Step 1: Calculate the force F2 applied by the elastic body 1 on the pressure surface and the force applied by the elastic body 2 on the suction surface.

[0013] The applied force is F3;

[0014] Step Two: Select the materials of elastomer one and elastomer two. Combining the force F2 applied by elastomer one on the pressure surface and the force F3 applied by elastomer two on the suction surface from Step One, apply the force at the design flow rate.

[0015] The elongation Δt1 of elastic body one and the elongation Δt2 of elastic body two were calculated.

[0016] Step 3: Calculate the force F5 applied by the elastic body 1 on the pressure surface and the force F6 applied by the elastic body 2 on the suction surface at high flow rates.

[0017] Step 4: Calculate the elongation Δt3 of elastomer one and the elongation Δt4 of elastomer two at high flow rates;

[0018] Step 5: Compare the elongation Δt at the design flow rate and at the large flow rate; if 0 < Δt1 < Δt3 and Δt2 > Δt4 > 0, it indicates that the leading edge of the blade has rotated towards the suction surface, and the verification is successful; otherwise, return to step 2 to reselect the elastomer.

[0019] 6. In a preferred example, this application can be further configured to include the following steps in step one:

[0020] S11: Calculate the resultant force F1 exerted by the fluid on the leading edge of the blade using the integral formula:

[0021] F1=∫∫p1dA

[0022] Where p1 is the pressure of the fluid on the leading edge of the blade at the design flow rate; A is the surface area of ​​the leading edge of the blade.

[0023] S12: Based on the pressure F1 of the fluid acting on the leading edge of the blade calculated in step S2, calculate F2 and F3 using the force balance equation:

[0024] ∑F i =0

[0025] Where i takes values ​​ranging from 1, 2, to 3; F2 is the force applied by the elastic body near the pressure surface; F3 is the force applied by the elastic body near the pressure surface.

[0026] The force exerted by the elastic body near the suction surface;

[0027] S13: Let the width of the leading edge of the blade be D. h The lever arm length of the elastic body near the pressure surface is L2, and the value of L2 is in the range of 0 ≤ L2 ≤ D. hLet the lever arm length of the elastic body near the suction surface be L3, and let the value of L3 be in the range of 0 ≤ L3 ≤ D. h When designing the flow rate, the moment at the hinge point is calculated, and F2 and F3 are calculated using the moment balance equation:

[0028] ∑M0=0

[0029] Where M1 is the torque generated by the fluid on the hinge point; M2 is the torque exerted by the elastic body near the pressure surface on the hinge point.

[0030] The torque generated; M3 is the torque generated by the elastic body near the suction surface about the hinge point 0;

[0031] S14: Combine the two equations from steps S12 and S13 to calculate the force F2 applied by the elastic body near the pressure surface and the force F3 applied by the elastic body near the suction surface.

[0032] In a preferred example, this application can be further configured such that step two includes the following steps:

[0033] S21: Given forces F2 and F3, and assuming the length l and area S of the two elastic bodies, select the elastic bodies and obtain E1 and E2. Calculate the elongation Δt using the axial tensile-compressive deformation formula.

[0034]

[0035] Where Δt is the elongation, F is the force applied by the elastic body, l is the length of the elastic body, E is the elastic modulus, and S is the area.

[0036] In a preferred embodiment, this application can be further configured to include the following steps: In step three,

[0037] Includes the following steps:

[0038] S31: At high flow rates, CFD technology is used to obtain the pressure of the fluid on the leading edge of the blade and the location of its point of action, i.e., the distance from the point of action to the hinge point is L4, and the value of L4 is in the range of 0≤L4≤D. h The resultant force F4 exerted by the fluid on the leading edge of the blade is calculated using the integral formula:

[0039] F4=∫∫p2dA

[0040] Where p2 is the pressure of the fluid on the leading edge of the blade under high flow conditions; A is the surface pressure of the leading edge of the blade.

[0041] area;

[0042] S32: At high flow rates, based on the fluid pressure F4 on the leading edge of the blade in step S31, calculate F5 and F6 using the force balance equation:

[0043] ∑Fx =0

[0044] Where F5 is the force applied by the elastic body near the pressure surface at high flow rates; F6 is the force applied by the elastic body near the suction surface at high flow rates.

[0045] The force applied by the elastic body of the force surface;

[0046] S33: Let the lever arm length of the elastic body near the pressure surface be L2, and the range of L2 is 0 ≤ L2 ≤ D. h The lever arm length of the elastic body near the suction surface is L3; the value of L3 is 0 ≤ L3 ≤ D. h At high flow rates, the moments at the hinge points are calculated using the moment balance equations to determine F5 and F6:

[0047] ∑M0=0

[0048] Where M4 is the torque generated by the fluid on the hinge point; M5 is the torque exerted by the elastic body near the pressure surface on the hinge point.

[0049] The torque generated; M6 is the torque generated by the elastic body near the suction surface on the hinge point;

[0050] S34: By combining the equations from steps S32 and S33, the force F5 exerted by the elastic body near the pressure surface and the force F6 exerted by the elastic body near the suction surface can be calculated.

[0051] In a preferred example, this application can be further configured to include the following steps in step four:

[0052] S41: Given forces F5, F6, E1, and E2, the elongation Δt of the two elastic bodies under high flow rate can be calculated using the axial tension-compression deformation formula.

[0053]

[0054] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0055] This application has the following advantages:

[0056] 1. Effectively regulates the interaction between the leading edge of the blade and the fluid, significantly reducing the flow separation area, enabling the centrifugal pump to maintain stable flow characteristics under high flow conditions, thereby ensuring high-efficiency operation of the pump and preventing energy loss and component damage caused by stall.

[0057] 2. The blades adopt movable leading edges, which can automatically adjust the blade leading edges according to the flow rate changes, meet the flow state requirements under high flow conditions, and meet the high efficiency operation requirements over a wide range of operating conditions, adapting to various complex operating scenarios. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the impeller cross-section structure of this application.

[0059] Figure 2 This application Figure 1 Enlarged diagram of part A in the middle.

[0060] Reference numerals: 1. Blade; 2. Leading edge section; 3. Elastomer one; 4. Hinge shaft; 5. Elastomer two; 6. Main body section. Detailed Implementation

[0061] The present application will be further described in detail below with reference to the accompanying drawings.

[0062] Reference Figure 1 and Figure 2 The blade 1 disclosed in this application for reducing stall includes a leading edge section 2 and a main body section 6. The leading edge section 2 and the main body section 6 are hinged together by a hinge shaft 4. The hinge joint of the leading edge section 2 and the main body section 6 is also connected by an elastic element. The elastic element includes an elastic body 1 3 and an elastic body 2 5. The elastic body 1 3 is located on the pressure surface, and the elastic body 2 5 is located on the suction surface. The elastic modulus of the elastic body 2 5 is greater than that of the elastic body 1 3. The elastic body 1 3 is located on one side of the hinge point, and the elastic body 2 5 is located on the other side of the hinge point.

[0063] This application also discloses a blade design method for reducing stall, characterized by the following steps:

[0064] Step 1: Calculate the force F2 applied by the elastic body 3 on the pressure surface and the force F3 applied by the elastic body 5 on the suction surface;

[0065] Step 2: Select the materials of elastomer 1 3 and elastomer 2 5. Combine the force F2 applied by elastomer 1 3 on the pressure surface and the force F3 applied by elastomer 2 5 on the suction surface in Step 1, and calculate the elongation Δt1 of elastomer 1 3 and the elongation Δt2 of elastomer 2 5 under the design flow rate.

[0066] Step 3: Calculate the force F5 applied by the elastic body 3 on the pressure surface and the force F6 applied by the elastic body 5 on the suction surface at high flow rates.

[0067] Step 4: Calculate the elongation Δt3 of elastomer 1 and the elongation Δt4 of elastomer 2 at high flow rates;

[0068] Step 5: Compare the elongation Δt at the design flow rate and at the large flow rate; if 0 < Δt1 < Δt3 and Δt2 > Δt4 > 0, it indicates that the leading edge segment 2 of blade 1 has rotated towards the suction surface, and the verification is successful; if not, return to step 2 to reselect the elastomer.

[0069] Step one includes the following steps:

[0070] S11: Calculate the resultant force F1 exerted by the fluid on the leading edge segment 2 of blade 1 using the integral formula:

[0071] F1=∫∫p1dA

[0072] Where p1 is the pressure of the fluid on the leading edge section 2 of blade 1 at the design flow rate; A is the surface area of ​​the leading edge section 2 of blade 1;

[0073] S12: Based on the pressure F1 of the fluid acting on the leading edge section 2 of blade 1 calculated in step S2, calculate F2 and F3 using the force balance equation:

[0074] ∑F i =0

[0075] Where i takes values ​​ranging from 1, 2, to 3; F2 is the force applied by the elastic body near the pressure surface; F3 is the force applied by the elastic body near the pressure surface.

[0076] The force exerted by the elastic body near the suction surface;

[0077] S13: Let the width of the leading edge of blade 1 be D. h The lever arm length of the elastic body near the pressure surface is L2, and the value of L2 is in the range of 0 ≤ L2 ≤ D. h Let the lever arm length of the elastic body near the suction surface be L3, and let the value of L3 be in the range of 0 ≤ L3 ≤ D. h When designing the flow rate, the moment at the hinge point is calculated, and F2 and F3 are calculated using the moment balance equation:

[0078] ∑M0=0

[0079] Where M1 is the torque generated by the fluid on the hinge point; M2 is the torque exerted by the elastic body near the pressure surface on the hinge point.

[0080] The torque generated; M3 is the torque generated by the elastic body near the suction surface about the hinge point 0;

[0081] S14: Combine the two equations from steps S12 and S13 to calculate the force F2 applied by the elastic body near the pressure surface and the force F3 applied by the elastic body near the suction surface.

[0082] Step two includes the following steps:

[0083] S21: Given forces F2 and F3, and assuming the length l and area S of the two elastic bodies, select the elastic bodies and obtain E1 and E2. Calculate the elongation Δt using the axial tensile-compressive deformation formula.

[0084]

[0085] Where Δt is the elongation, F is the force applied by the elastic body, l is the length of the elastic body, E is the elastic modulus, and S is the area.

[0086] Step three includes the following steps:

[0087] S31: At high flow rates, CFD technology is used to obtain the pressure of the fluid on the leading edge section 2 of blade 1 and the position of its point of action, i.e., the distance from the point of action to the hinge point is L4, and the value of L4 is in the range of 0≤L4≤D. h The resultant force F4 exerted by the fluid on the leading edge segment 2 of blade 1 is calculated using the integral formula:

[0088] F4=∫∫p2dA

[0089] Where p2 is the pressure exerted by the fluid on the leading edge section 2 of blade 1 under high flow conditions; A is the pressure of the leading edge of blade 1.

[0090] Surface area of ​​segment 2;

[0091] S32: At high flow rates, based on the pressure F4 exerted by the fluid on the leading edge section 2 of blade 1 in step S31, calculate F5 and F6 using the force balance equation:

[0092] ∑F x =0

[0093] Wherein, F5 is the force applied by the elastic body near the pressure surface when the flow rate is high; F6 is the force applied by the elastic body near the suction surface when the flow rate is high.

[0094] S33: Let the lever arm length of the elastic body near the pressure surface be L2, and the range of L2 is 0 ≤ L2 ≤ D. h The lever arm length of the elastic body near the suction surface is L3; the value of L3 is 0 ≤ L3 ≤ D. h At high flow rates, the moments at the hinge points are calculated using the moment balance equations to determine F5 and F6:

[0095] ∑M0=0

[0096] Where M4 is the torque generated by the fluid on the hinge point; M5 is the torque generated by the elastic body near the pressure surface on the hinge point; and M6 is the torque generated by the elastic body near the suction surface on the hinge point.

[0097] S34: By combining the equations from steps S32 and S33, the force F5 exerted by the elastic body near the pressure surface and the force F6 exerted by the elastic body near the suction surface can be calculated.

[0098] Step four includes the following steps:

[0099] S41: Given forces F5, F6, E1, and E2, the elongation Δt of the two elastic bodies under high flow rate can be calculated using the axial tension-compression deformation formula.

[0100]

[0101] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0102] The following examples further illustrate this point:

[0103] S1: Select an existing centrifugal pump and impeller. In this embodiment, a single-stage centrifugal pump is selected as an example to obtain the parameters of a single blade 11.

[0104] S2: Based on the known geometry and parameters of blade 1 from step S1, the leading edge width of blade 1 is known to be D. h Under the design flow rate, CFD technology is used to obtain the pressure p1 of the fluid on the leading edge section 2 of blade 1 and the position of its point of action. The distance from the point of action to the hinge point is set as L1, and the value of L1 is in the range of 0≤L1≤D. h The resultant force F1 exerted by the fluid on the leading edge segment 2 of blade 1 is calculated using the integral formula:

[0105] F1=∫∫p1dA

[0106] Where p1 is the pressure of the fluid on the leading edge section 2 of blade 1 at the design flow rate; A is the surface area of ​​the leading edge section 2 of blade 1;

[0107] Therefore, the resultant force F1 of the fluid on the leading edge section 2 of blade 1 at the design flow rate can be calculated.

[0108] S3: Based on the resultant force F1 of the fluid acting on the leading edge section 2 of blade 1 calculated in step S2, calculate F2 and F3 using the force balance equation:

[0109] ∑F i =0

[0110] Where i takes values ​​of 1, 2, and 3; F2 is the force applied by the elastic body near the pressure surface; F3 is the force applied by the elastic body near the suction surface;

[0111] It can be calculated that F1 + F2 + F3 = 0;

[0112] S4: Let the lever arm length of the elastic body 3 near the pressure surface be L2, and the range of L2 is 0 ≤ L2 ≤ D. h Let the lever arm length of the elastic body 25 near the suction surface be L3, and let the value of L3 be in the range of 0 ≤ L3 ≤ D. h Under the design flow rate, the moments at the hinge point are calculated, and F2 and F3 are calculated using the moment balance equation:

[0113] ∑M i =0;

[0114] Where i takes values ​​of 1, 2, and 3. M1 is the torque generated by the fluid on the hinge point, M2 is the torque generated by the elastic body 3 near the pressure surface on the hinge point, and M3 is the torque generated by the elastic body 5 near the suction surface on the hinge point.

[0115] It can be calculated that F1L1+F2L2+F3L3=0;

[0116] S5: Combine the equations from steps S3 and S4 to calculate the force F2 applied by the elastic body 3 near the pressure surface and the force F3 applied by the elastic body 5 near the suction surface.

[0117] S6: Based on the forces F2 and F3 applied by elastic body 1 (3) and elastic body 2 (5) in step S5, the length l and area S of the two elastic bodies are initially determined. The materials of the elastic bodies can then be preliminarily selected to obtain E1 and E2. The elongation Δt is calculated using the axial tensile-compressive deformation formula.

[0118]

[0119] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0120] The elongation Δt1 of the two elastic bodies under the design flow conditions can be calculated separately, where the elongation Δt1 of the elastic body near the pressure surface and the elongation Δt2 of the elastic body near the suction surface are calculated separately.

[0121] S7: At high flow rates, CFD technology is used to obtain the pressure p2 of the fluid on the leading edge section 2 of blade 1 and the position of its point of action, i.e., the distance from the point of action to the hinge point is L4, and the value of L4 is in the range of 0≤L4≤D. h The resultant force F4 exerted by the fluid on the leading edge segment 2 of blade 1 is calculated using the integral formula:

[0122] F4=∫∫p2dA

[0123] Where p2 is the pressure exerted by the fluid on the leading edge section 2 of blade 1 at a high flow rate; A is the surface area of ​​the leading edge section 2 of blade 1.

[0124] The resultant force F4 exerted by the fluid on the leading edge section 2 of blade 1 at the design flow rate can be calculated.

[0125] S8: At high flow rates, based on the pressure F4 exerted by the fluid on the leading edge section 2 of blade 1 in step S7, calculate F5 and F6 using the force balance equation:

[0126] ∑F x =0

[0127] Where x takes the values ​​4, 5, and 6; F5 is the force applied by the elastic body 3 near the pressure surface when the flow rate is high; F6 is the force applied by the elastic body 5 near the suction surface when the flow rate is high.

[0128] It can be calculated that F4 + F5 + F6 = 0;

[0129] S9: Given L2 and L3 from step S4; calculate the moment about the hinge point at high flow rates, and use the moment balance equation to calculate F5 and F6:

[0130] ∑M i =0;

[0131] Where i takes values ​​of 4, 5, and 6. M4 is the torque generated by the fluid on the hinge point when the flow rate is high, M5 is the torque generated by the elastic body 3 near the pressure surface on the hinge point, and M6 is the torque generated by the elastic body 5 near the suction surface on the hinge point.

[0132] It can be calculated that F4L4+F5L2+F6L3=0;

[0133] S10: Combine the equations from steps S8 and S9 to finally calculate the force F5 applied by the elastic body 3 near the pressure surface and the force F6 applied by the elastic body 3 near the suction surface.

[0134] S11: Based on the forces F5 and F6 applied by the two elastic bodies 3 and 5 in step S10, and given E1 and E2 of S6, calculate the elongation Δt using the axial tensile-compressive deformation formula:

[0135]

[0136] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0137] The elongation Δt3 of the elastic body 3 near the pressure surface and the elongation Δt4 of the elastic body 5 near the suction surface can be calculated separately when the flow rate is high.

[0138] S12: Compare the elongation Δt at the design flow rate and at the large flow rate; if 0 < Δt1 < Δt3 and Δt2 > Δt4 > 0, it indicates that the leading edge segment 2 of blade 1 has rotated in the direction of suction, the verification is passed, and the design ends; otherwise, return to step S6 to reselect the elastomer.

[0139] For example: a centrifugal pump with an impeller diameter of 100mm, a blade leading edge width of 5mm, and a leading edge height of 15mm.

[0140] S1: In this embodiment, a single-stage centrifugal pump is selected as an example to obtain the parameters of a single blade 11; the leading edge width D of blade 1. h The initial length of the elastic body is l = 3 mm, and the cross-sectional area of ​​the elastic body is S = 5 mm². The hinge point is located on the geometric center line of the leading edge segment 2. The pressure surface elastic body L2 = 2 mm², and the suction surface elastic body L3 = 2 mm². 2The conventions for sign and direction are as follows: force and torque increase the angle of placement by positive and decrease it by negative; for an elastic body, tension is positive and compression is negative. For an elastic body, elongation is positive and compression is negative.

[0141] S2: Based on the known geometry and parameters of blade 11 in step S1, the leading edge width D of blade 1 is... h With a diameter of 5 mm, at the design flow rate, the pressure p1 of the fluid on the leading edge section 2 of blade 1 was obtained using CFD technology, which is p1 = 120 kN / m. 2 And the position of its point of action, set the distance from the point of action to the hinge point as L1 = 1.5mm, the value of L1 is in the range of 0≤L1≤5mm, and the pressure F1 of the fluid on the leading edge section 2 of blade 1 is calculated by integral formula:

[0142] F1=∫∫p1dA

[0143] Where p1 is the pressure of the fluid on the leading edge section 2 of blade 1 at the design flow rate; A is the surface area of ​​the leading edge section 2 of blade 1;

[0144] Obtain the surface area A = 100 mm² of the leading edge portion of blade 1 in the impeller model. 2 The pressure of the fluid on the leading edge section 2 of blade 1 at the design flow rate can be calculated as F1 = -12N;

[0145] S3: Based on the pressure F1 of the fluid acting on the leading edge section 2 of blade 1 calculated in step S2, calculate F2 and F3 using the force balance equation:

[0146] ∑F i =0

[0147] Where i takes values ​​of 1, 2, and 3; F2 is the force applied by the elastic body near the pressure surface; F3 is the force applied by the elastic body near the suction surface;

[0148] Based on the known pressure F1 of the fluid on the leading edge 2 of blade 1 in step S2, we can conclude that F1+F2+F3=0;

[0149] F2 + F3 = 12N

[0150] S4: Set the lever arm length of the elastic body 3 near the pressure surface to L2, where L2 ranges from 0 to 0 and from 0 to D. h The lever arm length of the elastic body 25 near the suction surface is set to L3, and the value of L3 is in the range of 0 ≤ L3 ≤ D. h Under the design flow rate, the moments at the hinge point are calculated, and F2 and F3 are calculated using the moment balance equation:

[0151] ∑M i =0;

[0152] Where M1 is the torque generated by the fluid on the hinge point, M2 is the torque generated by the elastic body 3 near the pressure surface on the hinge point, and M3 is the torque generated by the elastic body 5 near the suction surface on the hinge point.

[0153] From M1+M2+M3=0, we can deduce that F1L1+F2L2+F3L3=0

[0154] F1L1+F2L2+F3L3=-12N*1.5mm+F2*2mm-F3*2mm=0

[0155] S5: Combine the two equations from steps S3 and S4 to calculate the force F2 applied by the elastic body 3 near the pressure surface and the force F3 applied by the elastic body 5 near the suction surface.

[0156] F2 + F3 = 12N

[0157] F2-F3=9N

[0158] We can solve for F2 = 10.5 N and F3 = 1.5 N.

[0159] S6: Based on the forces F2 and F3 applied by the elastic bodies 3 and 5 in step S5, the length l and area A are initially determined. The elastic body material is selected, and E1 and E2 are obtained. The elongation Δt is calculated using the axial tensile-compressive deformation formula.

[0160]

[0161] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0162] The elongation of the two elastic bodies under the design flow conditions can be calculated separately. Δt1 is the elongation of the elastic body on the pressure surface, and Δt2 is the elongation of the elastic body on the suction surface. The preliminary design is now complete.

[0163] The initial elastic modulus of the elastic body near the pressure surface is set to E1 = 10 (MPa).

[0164] Depend on

[0165] According to E2 = α1E1, α1 is taken as 0.5, E2 = 5 (MPa);

[0166] Similarly,

[0167] The elongation of the elastic body near the suction surface was found to be Δt1 = 0.63 (mm); Δt2 = 0.18 (mm).

[0168] S7: At high flow rates, the pressure p2 of the fluid on the leading edge section 2 of blade 1 is obtained using CFD technology, which is p2 = 100 kN / m. 2The location of its point of action is set as follows: the distance from the point of action to the hinge point is L4 = 2.5mm, and the value of L4 is in the range of 0 ≤ L4 ≤ D. h The pressure F4 exerted by the fluid on the leading edge section 2 of blade 1 is calculated using the integral formula:

[0169] F4=∫∫p2dA

[0170] Where p2 is the pressure exerted by the fluid on the leading edge section 2 of blade 1 at a high flow rate; A is the surface area of ​​the leading edge section 2 of blade 1.

[0171] Therefore, the pressure of the fluid on the leading edge section 2 of blade 1 at the design flow rate can be calculated as F4 = -10N;

[0172] S8: Under high flow rate conditions, based on the pressure F4 of the fluid on the leading edge section 2 of blade 1 in step S7, calculate F5 and F6 using the force balance equation:

[0173] ∑F x =0

[0174] Where x takes the values ​​4, 5, and 6; F5 is the force applied by the elastic body 3 near the pressure surface when the flow rate is high; F6 is the force applied by the elastic body 5 near the suction surface when the flow rate is high.

[0175] Based on the known pressure F4 of the fluid acting on the leading edge section 2 of blade 1 during the high flow rate in step S7, we can conclude that F4+F5+F6=0;

[0176] F4+F5+F6=0, therefore F5+F6=10N can be calculated.

[0177] S9: Given that the lever arm length of elastic body 3 near the pressure surface in step S4 is L2, and the lever arm length of elastic body 5 near the suction surface is L2; ​​calculate the moments about the hinge point at high flow rates, and calculate F5 and F6 using the moment balance equation:

[0178] ∑M i =0;

[0179] Where i takes values ​​of 4, 5, and 6. M4 is the torque generated by the fluid on the hinge point when the flow rate is high, M5 is the torque generated by the elastic body 3 near the pressure surface on the hinge point, and M6 is the torque generated by the elastic body 5 near the suction surface on the hinge point.

[0180] From M4+M5+M6=0, we can deduce F4L4+F5L2+F6L3=0;

[0181] -10N*2.5mm+F5*2mm-F6*2mm=0; F5-F6=12.5N

[0182] S10: By combining the two equations from steps S8 and S9, the force F5 applied by the elastic body 3 near the pressure surface and the force F6 applied by the elastic body 3 near the suction surface are finally calculated.

[0183] F5 + F6 = 10N

[0184] F5-F6=12.5N

[0185] We can solve for F5 = 11.25 N and F6 = -1.25 N.

[0186] S11: Based on the forces F5 and F6 applied by the two elastic bodies 3 and 5 in step S10, and E1 and E2 obtained in step S6, calculate the elongation Δt using the axial tensile-compressive deformation formula:

[0187]

[0188] Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the area.

[0189] The elongation of the elastomer at high flow rate can be calculated separately. Δt3 is the elongation of elastomer 3 near the pressure surface at high flow rate, and Δt4 is the elongation of elastomer 5 near the suction surface at high flow rate.

[0190]

[0191] The elongation of the elastic body near the pressure surface at high flow rates can be calculated as Δt3 = 0.675 mm (elongation increases); the elongation of the elastic body near the suction surface at high flow rates is Δt4 = -0.15 mm (elongation decreases).

[0192] S12: Compare the elongation Δt at the design flow rate and at the large flow rate; if Δt1 < Δt3 and Δt2 > Δt4, it indicates that the leading edge section 2 of blade 1 has rotated in the direction of suction, the verification is passed, and the design ends; otherwise, return to step S6 to reselect the elastomer material.

[0193] Compare deformation amounts:

[0194] For an elastomer located near the pressure surface, Δt1 = 0.63 mm at the design flow rate; Δt3 = 0.675 mm at a large flow rate. Δt1 < Δt3 (elongation increases).

[0195] For the elastomer near the suction surface, Δt2 = 0.18 mm at the design flow rate and Δt4 = -0.15 mm at a large flow rate. Δt2 > Δt4 (elongation decreases), which meets the requirements, and the design verification is successful.

[0196] The implementation principle of this embodiment is as follows: Under high flow conditions, the resultant flow force on the leading edge section 2 of blade 1 changes. Through the different deformation amounts of the pressure surface elastomer 3 and the suction surface elastomer 5, the leading edge section 2 of blade 1 automatically increases its inlet placement angle, thereby optimizing the flow characteristics under different operating conditions and reducing stall. When the flow rate returns to the design value, the leading edge section 2 of blade 1 returns to the design placement angle position under the action of the pressure surface elastomer 3 and the suction surface elastomer 5.

[0197] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A blade for reducing stall, characterized in that: It includes a leading edge segment (2) and a main body segment (6), which are connected by an elastic element.

2. The blade for reducing stall according to claim 1, characterized in that: The elastic element includes an elastic body one (3) and an elastic body two (5). The elastic body one (3) is located on the pressure surface, and the elastic body two (5) is located on the suction surface. The elastic modulus of the elastic body two (5) is greater than that of the elastic modulus of the elastic body one (3).

3. A blade for reducing stall according to claim 2, characterized in that: The leading edge segment (2) and the main body segment (6) are hinged together. Elastic body one (3) is located on one side of the hinge point, and elastic body two (5) is located on the other side of the hinge point.

4. A method for designing blades to reduce stall, characterized in that: Includes the following steps: Step 1: Calculate the force F2 applied by the elastic body 1 (3) on the pressure surface and the force F3 applied by the elastic body 2 (5) on the suction surface; Step 2: Select the materials of elastic body one (3) and elastic body two (5), and combine the force F2 applied by elastic body one (3) on the pressure surface and the force F3 applied by elastic body two (5) on the suction surface in Step 1. The elongation Δt1 of elastomer one (3) and the elongation Δt2 of elastomer two (5) were calculated under the design flow rate. Step 3: Calculate the force F5 applied by the elastic body 1 (3) on the pressure surface and the force F6 applied by the elastic body 2 (5) on the suction surface at high flow rates. Step 4: Calculate the elongation Δt3 of elastomer one (3) and the elongation Δt4 of elastomer two (5) at high flow rates; Step 5: Compare the elongation Δt at the design flow rate and at the large flow rate; if 0 < Δt1 < Δt3 and Δt2 > Δt4 > 0, it indicates that the leading edge section (2) of the blade has rotated towards the suction surface, and the verification is successful; if not, Then return to step two to select an elastomer again.

5. The blade design method for reducing stall according to claim 4, characterized in that: Step one includes the following steps: S11: Calculate the resultant force F1 exerted by the fluid on the leading edge section (2) of the blade using the integral formula: F1=∫∫p1dA Where p1 is the pressure of the fluid on the leading edge section (2) of the blade at the design flow rate; A is the surface area of ​​the leading edge section (2) of the blade. S12: Based on the pressure F1 of the fluid acting on the leading edge section (2) of the blade calculated in step S2, calculate F2 and F3 using the force balance equation: ∑F i ＝0 Where i takes values ​​of 1, 2, and 3; F2 is the force applied by the elastic body near the pressure surface; F3 is the force applied by the elastic body near the suction surface; S13: Let the width of the leading edge of the blade be D. h The lever arm length of the elastic body near the pressure surface is L2, and the value of L2 is in the range of 0 ≤ L2 ≤ D. h Let the lever arm length of the elastic body near the suction surface be L3, and let the value of L3 be in the range of 0 ≤ L3 ≤ D. h When designing the flow rate, the moment at the hinge point is calculated, and F2 and F3 are calculated using the moment balance equation: ∑M0＝0 Where M1 is the torque generated by the fluid on the hinge point; M2 is the torque generated by the elastic body near the pressure surface on the hinge point; M3 is the torque generated by the elastic body near the suction surface on the hinge point 0. S14: Combine the two equations from steps S12 and S13 to calculate the force F2 applied by the elastic body near the pressure surface and the force F3 applied by the elastic body near the suction surface.

6. The blade design method for reducing stall according to claim 4, characterized in that: Step two includes the following steps: S21: Given forces F2 and F3, and assuming the length l and cross-sectional area S of the two elastic bodies, select the elastic bodies and obtain E1 and E2. Calculate the elongation Δt using the axial tensile-compressive deformation formula. Where Δt is the elongation, F is the force applied by the elastic body, l is the length of the elastic body, E is the elastic modulus, and S is the cross-sectional area.

7. The blade design method for reducing stall according to claim 4, characterized in that: Step three includes the following steps: S31: At high flow rates, the pressure of the fluid on the leading edge section (2) of the blade and the position of its point of action are obtained through CFD technology. That is, the distance from the point of action to the hinge point is L4, and the value of L4 is 0≤L4≤D. h The resultant force F4 exerted by the fluid on the leading edge section (2) of the blade is calculated using the integral formula: F4=∫∫p2dA Where p2 is the pressure of the fluid on the leading edge section (2) of the blade under high flow conditions; A is the surface area of ​​the leading edge section (2) of the blade. S32: At high flow rates, based on the pressure F4 exerted by the fluid on the leading edge section (2) of the blade in step S31, calculate F5 and F6 using the force balance equation: ∑F x ＝0 Wherein, F5 is the force applied by the elastic body near the pressure surface when the flow rate is high; F6 is the force applied by the elastic body near the suction surface when the flow rate is high. S33: Let the lever arm length of the elastic body near the pressure surface be L2, and the range of L2 is 0 ≤ L2 ≤ D. h The lever arm length of the elastic body near the suction surface is L3; the value of L3 is 0 ≤ L3 ≤ D. h At high flow rates, the moments at the hinge points are calculated using the moment balance equations to determine F5 and F6: ∑M0＝0 Where M4 is the torque generated by the fluid on the hinge point; M5 is the torque generated by the elastic body near the pressure surface on the hinge point; and M6 is the torque generated by the elastic body near the suction surface on the hinge point. S34: By combining the equations from steps S32 and S33, the force F5 exerted by the elastic body near the pressure surface and the force F6 exerted by the elastic body near the suction surface can be calculated.

8. The blade design method for reducing stall according to claim 4, characterized in that: Step four includes the following steps: S41: Given forces F5, F6, E1, and E2, the elongation Δt of the two elastic bodies under high flow rate can be calculated using the axial tension-compression deformation formula. Where Δt is the elongation, F is the pressure, l is the original length, E is the elastic modulus, and S is the cross-sectional area.

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