Design method of large turning angle variable camber guide vane

Abstract

The present disclosure relates to the technical field of aero-engine, and particularly provides a design method of a large deflection angle variable camber guide vane. The design method comprises the following steps: S1, determining a design index, and determining a total chord length and a maximum thickness of the guide vane height according to the design index; S2, uniformly dividing the guide vane from a blade root to a blade tip into a plurality of elements, and projecting into a two-dimensional plane; S3, determining a bending angle of an after vane camber line; S4, determining an after vane solidity and a slotting position of each element; S5, calculating a narrow gap outlet width of each element in a first deflection angle state; S6, determining a contraction ratio of the narrow gap in the first deflection angle state; S7, determining an after vane profile of each element; S8, determining a narrow gap; S9, determining a narrow gap in a third deflection angle; S10, determining a rotation center position of the after vane of each element; and S11, inversely transforming the element designed in the two-dimensional plane back to the element uniformly divided from the blade root to the blade tip, and performing radial stacking. The present disclosure can increase a usable deflection angle range of the variable camber guide vane.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of aero-engines, and particularly relates to a design method of a variable-camber vane with a large turning angle. BACKGROUND

[0002] In the field of aero-engine design, an aero-compressor needs to ensure a certain efficiency and margin, and requires that the compressor rotor blade works within a usable angle of attack range. Under conditions such as changes in inlet conditions and changes in engine speed, the rotor blade angle of attack may exceed the usable angle of attack range, resulting in a decrease in compressor efficiency or even engine surge. To address this problem, adjustable vanes are often used in engine design, and by adjusting the installation angle of the adjustable vane, the inlet absolute flow angle and the angle of attack of the moving blade are changed, so that the rotor blade works within the usable angle of attack range, ensuring the efficiency and margin of the compressor.

[0003] The available adjustment range is an important technical indicator of the adjustable vane, and the larger the available adjustment range, the more beneficial it is to ensure the margin and high-efficiency working range of the compressor, and the higher the degree of freedom of engine design. In addition, in a variable cycle engine, the compressor needs to work stably in a wider range, and the available adjustment range of the adjustable vane as a regulation technology is crucial to the working range of the engine.

[0004] Variable-camber vanes have a wider available adjustment range than integral adjustable vanes. Variable-camber vanes are vanes in aero-engines that can change their camber, and are generally divided into front and rear parts, and the rear part can rotate around a rotating shaft 6 to change the camber. In the low-pressure compressor and high-pressure compressor of an aero-engine, variable-camber vanes mainly have the following functions: preventing compressor surge, expanding the stable working boundary of the compressor, and adjusting the working state of the compressor.

[0005] Variable-camber vanes have high design freedom and many design parameters. Current design methods mainly involve modifying a single adjustable vane or improving the local geometry of a variable-camber vane, and there is a lack of a complete design process that covers the overall design of the blade, resulting in a long design cycle and limited design effect.

[0006] The main problem of existing variable-camber vanes is that the available adjustment range is insufficient, and there is a lack of design guidelines that can be referred to in the design, and there is no design method that can effectively improve the available adjustment range.

[0007] As the rear blade angle increases from the minimum loss angle, the airflow deflection angle increases, and the total pressure loss coefficient of the variable camber guide vane increases. Especially when the rear blade angle reaches a certain value, the suction surface of the rear blade undergoes open separation, resulting in a significant increase in losses. The usable adjustment range of a two-dimensional variable camber guide vane with a circular leading edge and a circular trailing edge at Mach 0.3 is approximately below an outlet airflow angle of 25 degrees.

[0008] The design parameters of the slit between the front and rear blades, such as the slit shape, slit width, and leading edge shape of the rear blade, can alter the jet state through the slit, thus affecting the total pressure loss coefficient and the available adjustment range of the variable camber guide vane. However, current variable camber guide vanes do not optimize the design of the slit and the rear blade profile. Existing design methods for variable camber guide vanes do not address how to design the trailing edge profile of the front blade, the leading edge profile of the rear blade, and the rear blade profile at the slit to increase the available adjustment range of the variable camber guide vane. Summary of the Invention

[0009] This disclosure is made in view of the above-mentioned problems. This disclosure provides a design method for a large-angle variable camber guide vane.

[0010] According to one aspect of this disclosure, a design method for a large-angle variable camber guide vane is provided, comprising the following steps:

[0011] S1, determine the design parameters, and determine the total chord length and maximum thickness of the guide vane height based on the design parameters;

[0012] S2, the guide vane is evenly divided into multiple basic units from the leaf root to the leaf tip, and projected onto a two-dimensional plane;

[0013] S3, determine the curvature angle of the arc line in the back leaf of each basic element;

[0014] S4, determine the back leaf consistency of each basic unit, and determine the slot opening position based on the back leaf consistency; the criterion for back leaf consistency is:

[0015] σ≥2sin(β out ) / q;

[0016] Where σ is the posterior leaf consistency, β out It is the design exit geometry angle of the blade height under the first turning angle state, and q is a constant coefficient;

[0017] S5, calculate the exit width of each basic element slit under the first turning angle state;

[0018] S6, determine the contraction ratio of the slit in the first turning angle state;

[0019] S7 generates the leaf shape of each primitive leaf;

[0020] S8, define the slit;

[0021] S9, determine the third corner under the slit;

[0022] S10, determine the center position of each element rear vane rotation;

[0023] S11, the two-dimensional plane in the design of the element inverse transform back to the uniform division of the element from the blade root to the blade tip, radial accumulation.

[0024] According to the design method of the large fold corner variable camber guide vane of one aspect of the present disclosure, in step S3, the camber angle of the rear vane is determined by the following formula,

[0025] θ = 0.5 * (β min + β max ) - s * (β max - β min );

[0026] Wherein, θ is the camber angle of the rear vane, β min is the minimum outlet geometric angle of the design requirement corresponding to the blade height position, β max is the maximum outlet geometric angle of the design requirement, and s is a constant coefficient.

[0027] According to the design method of the large fold corner variable camber guide vane of one aspect of the present disclosure, in step S5, the outlet width of each element slit in the first corner state is calculated by the following formula:

[0028]

[0029] Wherein, W out is the outlet width of the slit selected at the blade height, TH is the maximum thickness of the blade at the blade height determined according to the design index, ρ is the density of the incoming flow in the first corner state, U is the airflow velocity in the main flow area in the first corner state, ν is the air viscosity, and Re is a constant coefficient.

[0030] According to the design method of the large fold corner variable camber guide vane of one aspect of the present disclosure, in step S6, the method for determining the contraction ratio of the slit in the first corner state is to control the ratio of the outlet velocity of the slit to the main flow velocity between 1.0 and 1.1, and to select the contraction ratio according to the Mach number, Reynolds number and the first corner.

[0031] According to the design method of the large fold corner variable camber guide vane of one aspect of the present disclosure, in step S7, the determination of the rear vane profile of each element includes,

[0032] The curvature distribution form of the rear vane suction surface 7 is strong front loading, and the peak curvature position is located at the outlet of the slit. The element profile of the rear vane at each blade height is generated by parameterized modeling, and the selection criterion of the peak curvature is that the included angle between the jet flow at the outlet of the slit and the horizontal direction is less than 15 degrees.

[0033] According to the design method of the large deflection angle variable camber guide vane, in step S8, the method for determining the slit is that the slit inlet width and the slit outlet width at the first deflection angle of the unit are calculated, the positions of the slit inlet point and the slit outlet point on the front vane tail edge profile are calculated, a rear half of the front wall surface profile of the slit is formed by using a circular arc parallel to the slit outlet, and a front half of the slit is formed by using a smooth curve connecting the slit inlet and the front vane pressure surface.

[0034] According to the design method of the large deflection angle variable camber guide vane, the calculation formula of the radius of the circular arc is

[0035]

[0036] wherein R is the radius of the circular arc, T ∥ is the horizontal distance between the highest point and the most forward point at the first deflection angle of the rear vane leading edge, and is the vertical distance between the highest point and the most forward point at the first deflection angle of the rear vane leading edge.

[0037] According to the design method of the large deflection angle variable camber guide vane, step S9 comprises judging whether there is a third deflection angle commonly used in addition to the maximum deflection angle and the minimum deflection angle.

[0038] If there is a third deflection angle, the slit inlet width and the slit outlet width at the commonly used deflection angle are calculated according to step S4 and step S5.

[0039] According to the design method of the large deflection angle variable camber guide vane, step S10 comprises

[0040] The positions satisfying the slit inlet width and the slit outlet width at the first deflection angle state and the third deflection angle state are taken as the rotation center positions of the rear vane.

[0041] According to the design method of the large deflection angle variable camber guide vane, the method further comprises

[0042] S12, evaluating whether there is open separation at the first deflection angle, if there is, adjusting the rear vane solidity and the slit geometric parameters according to the evaluation result, and repeating steps S1 to S11 until there is no open separation at the first deflection angle.

[0043] As will be described in detail below, the design method of the large turning angle variable camber guide vane according to the embodiments of the present disclosure divides the vane from the root to the tip into a plurality of elements uniformly, projects to a two-dimensional plane, and proposes a calculation formula of the back vane solidity, then determines the slit outlet width, the contraction ratio of the slit in the first turning angle state, the back vane profile of each element, the front vane tail edge, the slit in the third turning angle and the position of the rotation center of each back vane, and then reversely transforms the element designed in the two-dimensional plane back to the element divided from the root to the tip uniformly, and performs radial stacking. In some implementations, the two-dimensional plane is perpendicular to the radial direction. The present disclosure can finely control the flow field in the key areas such as the variable camber guide vane slit and the slit outlet, and consider the radial stacking of the slit geometry in different vane heights and different turning angles, so as to achieve the beneficial effects of suppressing open separation of the airflow, controlling the loss and improving the available turning angle range of the variable camber guide vane in multiple different turning angles, especially in large turning angles.

[0044] It is to be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further explanation of the subject technology. BRIEF DESCRIPTION OF DRAWINGS

[0045] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[0046] Figure 1 is a front view of the variable guide vane proposed by the present disclosure;

[0047] Figure 2 is a top view of the variable guide vane proposed by the present disclosure at a certain turning angle;

[0048] Figure 3 is a top view of the variable guide vane proposed by the present disclosure at another turning angle;

[0049] Figure 4 is a step flow chart of the design method proposed by the present disclosure;

[0050] Figure 5 is a whole modeling parameter diagram of the variable camber guide vane proposed by the present disclosure;

[0051] Figure 6 is a two-dimensional projection diagram of the slit at the i-th vane height position of the variable camber guide vane;

[0052] Figure 7 is a characteristic diagram of the outlet flow angle and total pressure loss in the preferred example 1 of the present disclosure;

[0053] Figure 8 is a comparison of the preferred embodiment 1 with the circular variable camber vane at 30° turning angle of the midspan Mach number contours;

[0054] Figure 9 is a comparison of the preferred embodiment 2 with the circular variable camber vane at 30° turning angle of the total pressure loss coefficient distribution at 25% chord length from the trailing edge;

[0055] Figure 10 is a schematic of the 50% span slot local geometry of the preferred example 2 of the present disclosure;

[0056] Figure 11 is a total pressure loss spanwise distribution plot of the preferred example 2 and the circular slot variable camber vane at 40° turning angle;

[0057] Figure 12a is a total pressure loss contours of the circular slot variable camber vane at 40° turning angle at the slot streamline and 50% chord length from the trailing edge;

[0058] Figure 12b is a total pressure loss contours of the preferred example 2 of the present disclosure at 40° turning angle at the slot streamline and 50% chord length from the trailing edge;

[0059] Figure 13 is the blade profile plot of the preferred example 3 of the present disclosure at 0° turning angle;

[0060] Figure 14 is the blade profile plot of the preferred example 3 of the present disclosure at 47° turning angle;

[0061] Figure 15 is the total pressure loss characteristics of the preferred example 3 and the circular slot variable camber vane;

[0062] Figure 16 is the Mach number contours of the preferred example 3 at 57° turning angle of the rear blade at the limit condition.

[0063] BRIEF DESCRIPTION OF DRAWINGS

[0064] 1 - front blade, 2 - rear blade, 3 - slot, 4 - slot exit, 5 - slot entry, 6 - pivot, 7 - rear blade suction surface, 8 - front blade trailing edge, 9 - rear blade leading edge, 10 - rear blade camber line. DETAILED DESCRIPTION

[0065] In order to make the objectives, technical solutions and advantages of the present disclosure more obvious, the following will describe the example embodiments according to the present disclosure in detail with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure, and it should be understood that the present disclosure is not limited by the example embodiments described herein.

[0066] To solve the problems raised in the background art, the present disclosure proposes a design method of a large deflection angle variable camber guide vane, please refer to Figures 1 to 3 The variable camber guide vane in the present disclosure includes two components, i.e., a front vane 1 and a rear vane 2, wherein the front vane 1 is fixed, the rear vane 2 can rotate around a rotation shaft 6, and a gap 3 is formed between the front vane 1 and the rear vane 2. The geometric shapes of the front vane 1 and the rear vane 2 are determined by a plurality of modeling parameters of parameterized modeling, the modeling parameters are selected according to design criteria, and a suitable radial stacking mode is selected to control the geometric shapes of the gap at different vane heights and different rotation angles, so as to improve the flow structure and achieve the beneficial effects of low loss and wide adjustment range. Key modeling parameters include chord length of the rear vane 2 at a plurality of vane height elements from 0% to 100% of the vane height position, width of the gap outlet 4, width of the gap inlet 5, curvature distribution form of the rear vane suction surface 7, peak curvature of the rear vane suction surface, etc.

[0067] Please refer to Figures 1 to 6 The method proposed in the present disclosure includes the following steps,

[0068] S1, determining a design index, and determining the total chord length and the maximum thickness of the guide vane height according to the design index; in specific implementation, parameters directly related to the design index are specified. The design index includes the maximum adjustment angle of the whole blade, the total chord length and the maximum thickness of each vane height, and the required outlet geometric angle distribution of the rear vane from 0% to 100% of the vane height position in the first rotation angle state. According to the design index, the total chord length and the maximum thickness of each vane height of the variable camber guide vane are specified.

[0069] S2, uniformly dividing the guide vane from the vane root to the vane tip into a plurality of elements, and projecting into a two-dimensional plane; according to the meridian profile of the engine hub and the casing, the variable camber guide vane is divided into n elements uniformly from the vane root to the vane tip, and each element is projected into a two-dimensional plane for subsequent design of each element. In specific implementation, the two-dimensional plane is a two-dimensional plane perpendicular to the radial direction of the blade.

[0070] S3, determining the bending angle of the arc line 10 in the rear vane; according to the required outlet flow angle range of the design requirement, the bending angle of the rear vane is selected. In this step, the bending angle of the arc line 10 in the rear vane is determined by the following formula,

[0071] θ=0.5*(β min +β max )-s*(β max -β min );

[0072] wherein θ is the bending angle of the rear vane, β min is the minimum outlet geometric angle required by the design requirement at the corresponding vane height position, and β maxis the maximum outlet geometric angle of the leaf height position design requirement, and s is a constant coefficient. The distribution form of the rear leaf camber angle designed by the formula is consistent with the distribution form of the outlet geometric angle of the design index. The value range of the parameter s is 0.15-0.25.

[0073] S4, determine the rear leaf solidity and the slot position of each element; the criterion for the rear leaf solidity is:

[0074] σ≥2sin(β out ) / q;

[0075] wherein σ is the rear leaf solidity, β out is the design outlet geometric angle of the leaf height in the first corner state, and q is a constant coefficient; the value range of the parameter q is 0.8-1.3. According to the formula, the rear leaf solidity is determined, and then the rear leaf chord length of each leaf height is obtained, and then the relative position of the slot between the front leaf and the rear leaf is obtained, and the maximum thickness of the variable camber guide vane is set as the position.

[0076] S5, calculate the slot outlet width of each element in the first corner state; in this step, the slot outlet width of each element in the first corner state is calculated by the following formula:

[0077]

[0078] wherein W out is the slot outlet width to be selected at the leaf height, TH is the maximum thickness of the blade at the leaf height determined according to the design index, ρ is the density of the incoming flow in the first corner state, U is the main flow velocity in the first corner state, v is the air viscosity, and Re is a constant coefficient. The value of the parameter Re is greater than 125.

[0079] S6, determine the contraction ratio of the slot in the first corner state; the method for determining the contraction ratio of the slot in the first corner state is to control the ratio of the slot outlet velocity to the main flow velocity to be between 1.0 and 1.1, and to select the contraction ratio according to the incoming flow Mach number, the Reynolds number and the first corner. For the evaluation of the initial value of the contraction ratio before the outlet velocity or the design scene requiring a shorter design period, the recommended slot contraction ratio selection range is between 0.4 and 0.6. According to the contraction ratio, the slot inlet width W in is calculated.

[0080] S7, determine the rear leaf airfoil of each element; the curvature distribution form of the rear leaf suction surface 7 is strong front loading, and the peak curvature position is located at the slot outlet 4. The element airfoils of the rear leaf at each leaf height are generated by parameterization modeling, and the selection criterion of the peak curvature is that the included angle between the jet flow at the slot outlet 4 and the horizontal direction is less than 15 degrees. To ensure that the slot outlet 4 has a relatively strong Coanda effect locally, the flow can flow along the wall, and the rear leaf suction surface 7 is not easy to separate.

[0081] S8, determining the slot; in this step, one of the keys to determine the slot is to determine the leading edge tail edge first, wherein the method for determining the leading edge tail edge is that the slot inlet width and the slot outlet width at the first corner of the base element are used to calculate the position of the slot inlet point and the position of the slot outlet point on the leading edge tail edge 8 profile line, a circular arc horizontal to the slot outlet 4 is used to connect the slot inlet and outlet points on the leading edge tail edge 8 to form the rear half of the front wall surface profile line of the slot, and a smooth curve is used to connect the slot inlet 5 and the leading edge pressure surface to form the front half of the slot.

[0082] wherein the calculation formula of the radius of the circular arc is,

[0083]

[0084] wherein R is the radius of the circular arc, T ∥ is the horizontal distance between the highest point and the most forward point at the first corner of the trailing edge leading edge 9, and is the vertical distance between the highest point and the most forward point at the first corner of the trailing edge leading edge 9.

[0085] S9, determining the slot at the third corner; in this step, it is determined whether there is a third corner in addition to the maximum corner and the minimum corner; if there is a third corner, the slot inlet width and the slot outlet width at the third corner are calculated according to steps S4 and S5.

[0086] Specifically, if the variable camber guide vane has a third corner Δθ2 in addition to the first corner position and the second corner position in the engine design requirement, the slot geometry also needs to meet the design criteria, and the slot inlet width and the outlet width of each blade height base element at Δθ2 are calculated according to steps S4 and S5.

[0087] If the variable camber guide vane has only the first corner and the second corner as two common working modes, Δθ2 is selected to be equal to the minimum design corner, that is, Δθ2=β min , and the slot outlet width at this time is specified to be 0, so as to ensure that the leading edge and the trailing edge do not interfere with each other in the full corner range from opening to closing of the trailing edge.

[0088] S10, determining the position of the trailing edge rotation center of each base element; the positions satisfying the slot inlet width and the slot outlet width at the first corner state and the third corner state are taken as the rotation center positions of the trailing edge.

[0089] S11, the designed element in the two-dimensional plane is inversely transformed back to the element uniformly divided from the blade root to the blade tip, and radial stacking is performed. First, the optimal slot geometry of each blade height element at two corners is determined to determine two virtual rear blade positions. Then, the fixed point of the two virtual rear blade positions is used as the pivot 6 position. Finally, the blade height elements are translated so that the pivot 6 positions of different blade heights are on a straight line. The slot profile of each blade height element and the rear blade are translated as a whole in the blade height plane, and the rear blade rotation center positions of each blade height are aligned. The designed blade height element in the two-dimensional plane is inversely transformed back to the n elements uniformly divided from the blade root to the blade tip, and radial stacking is performed. Whether the blade meets the processing technology requirements is checked, and the design is completed.

[0090] In the specific implementation, step S12 is further included. In step S12, whether the first corner has open separation is evaluated. If the first corner has open separation, the rear blade solidity and the slot geometry parameters are adjusted according to the evaluation result, and steps S1 to S11 are repeated until the first corner does not have open separation.

[0091] The following is further described in combination with specific examples.

[0092] In preferred example 1, the design method of the application is used for variable camber guide vane design in an aero-engine, and the available range is 0 to 30 degrees. In this example, in the real engine flow passage, the design index gives the total chord length of the blade root as 64 mm, the total chord length of the blade tip as 88 mm, and the maximum thickness design index as: the maximum thickness of the blade root is 4.4 mm, and the maximum thickness of the blade tip is 6.1 mm.

[0093] According to the meridian profile of the hub and the casing of the engine at the variable camber guide vane, the engine flow passage is divided into 12 elements, and each element is projected onto a two-dimensional plane.

[0094] According to the solidity selection criterion σ≥2sin(β out ) / q; q≈1.0 is taken, and the rear blade solidity of each blade height is selected. Taking the blade root, the middle blade, and the blade tip as examples, the rear blade solidity is selected as 1.48, 1.25, and 1.13, respectively, and the solidity selection of other blade heights is shown in Table 1. The slot opening position is determined according to the solidity.

[0095] Table 1: Rear blade solidity and camber angle of preferred example 1

[0096]

[0097] In the design index of preferred example 1, the available range requirement of the average outlet flow angle is 0° to 30°. Taking the blade root, the middle blade, and the blade tip as examples, the spanwise distribution requirement is that at the 0° corner of the rear blade, the outlet flow angles of the three sections of the blade root, the middle blade, and the blade tip are -8.8°, -1.9°, and 4.2°, respectively. Since the maximum available outlet flow angle is less than 30°, it is relatively easy to achieve, so the rear blade camber angle criterion θ= The trailing edge angle of each blade height section is specified as the minimum exit flow angle. The trailing edge angle of each blade height section is selected as shown in Table 1.

[0098] In the first turning angle of 30°, the slot exit width is designed according to the design criterion of slot exit width The slot exit width is selected as 0.55mm.

[0099] The slot contraction ratio of each blade height is selected as the ratio of the slot exit velocity to the main flow velocity u jet / u≈1.

[0100] The trailing edge is selected as the profile with strong foreloading of the suction surface curvature distribution, and the peak curvature is located at the slot exit, and the peak curvature satisfies the angle α jeet <15°.

[0101] According to the slot exit width and the contraction ratio, the positions of the slot inlet and outlet points on the trailing edge profile of the front blade are calculated, and the front wall profile of the slot is formed by using a horizontal circular arc to connect the slot inlet and outlet points on the trailing edge of the front blade, and the part of the leading edge of the trailing blade together constitutes the slot.

[0102] Δθ2=β min is selected, that is, in the second turning angle, the slot exit width of each blade height section is specified as 0.2mm, and the geometry is checked to ensure that the front blade and the trailing blade do not interfere with each other in the full turning angle range from opening to closing of the trailing blade.

[0103] The fixed point between the first turning angle geometry of the trailing blade of each blade height element and the virtual trailing blade geometry in the Δθ2 turning angle is calculated as the rotation center position of the trailing blade of the blade height.

[0104] The slot front wall profile and the trailing blade of the 12 blade height elements are translated as a whole in the blade height plane, and the rotation center positions of the trailing blades of each blade height are aligned. In the plane of each element, the geometry of the front blade except the trailing edge part is translated circumferentially, so that the thickness of the front blade at the slot exit is the minimum thickness 0.1mm allowed by the processing technology. Smooth profiles are used to connect the slot inlet and the pressure surface of the front blade. The designed blade height elements in the two-dimensional plane are inversely transformed back to 12 elements uniformly divided from the blade root to the blade tip, and the design is completed.

[0105] Figure 7 is the total pressure loss characteristic diagram of the preferred example 1 and the circular slot variable-camber guide vane at different turning angles. It can be seen that the preferred example 1 has lower loss at most turning angles, especially at large turning angles. If the total pressure loss of 0.06 is taken as the standard, the maximum exit flow angle of the preferred example 1 is expanded from 19° to 29°.

[0106] Figure 8is the Mach number contour of the mid-span section of the blade at the 30° angle of attack. It can be seen that, at the 30° angle of attack, the large scale separation occurs on the suction surface of the downstream blade of the circular slot variable camber stator, while the total pressure loss of the preferred example 1 is low because the separation of the downstream blade is controlled by the slot jet.

[0107] Figure 9 is the total pressure loss distribution of the section at 25% chord length behind the trailing edge of the downstream blade at the 30° angle of attack. It can be seen that, because the separation flow occurs on the downstream blade of the circular slot variable camber stator, the wake is wide and the total pressure loss in the wake is large. While the wake of the preferred example 1 is narrow and the loss in the wake is low because the large scale separation of the downstream blade does not occur.

[0108] In the preferred example 2, the variable camber stator is designed using the design guidelines of the present application.

[0109] Table 2 is the design requirement of the preferred example 2, including two operating conditions. According to the geometric requirements in the design guidelines, the hub and the casing profiles of the preferred example 2 are specified. Seven sections are arranged in the spanwise direction, and the downstream blade camber angle of the blade in each section is specified. The downstream blade camber angles of the blade root and the blade tip are given according to the pre-whirl in the design requirement, and the camber angles of the remaining sections are calculated by interpolation.

[0110] Table 2 Design requirement of the preferred example 2

[0111]

[0112] The initial value is determined by the slot outlet width and the contraction ratio selection criteria of the present application. At the design angle of 40°, at the position of 50% blade height, the inlet and outlet widths of the slot are adjusted within a certain range, the loss under different inlet and outlet widths is evaluated by CFD calculation, and the optimal inlet and outlet widths are selected.

[0113] According to the inlet and outlet widths of the slot, a circular arc with a radius of is used as the upper half of the front blade trailing edge 8, and a cubic curve is used to transition the lower half of the front blade trailing edge 8 to the pressure surface, thereby constructing a horn-shaped slot inlet, increasing the total pressure of the slot inlet, and Figure 10 .

[0114] The downstream blade profile of each blade height element satisfies the form of the curvature distribution of the suction surface, which is strong front loading, and the peak curvature position is located at the slot outlet 4.

[0115] According to the design principle that the front and rear blades do not interfere with each other at the 0° angle of attack, the position of the downstream blade rotation center of each blade height section is selected, the positions of the downstream blade rotation centers of each blade height are aligned, and the radial stacking is performed to complete the design.

[0116] Figure 11is the total pressure loss spanwise distribution of the preferred example 2 and the round slot variable camber vane at 40° angle of attack, the total pressure loss of the round slot variable camber vane is all greater than 0.2 along the spanwise, the maximum total pressure loss coefficient reaches above 0.6 at the tip, while the total pressure loss coefficient of the preferred example 2 near the 50% spanwise height of the main flow is greatly reduced to below 0.04. Above the 70% blade height, the total pressure loss coefficient of the preferred example 2 is reduced by more than 0.3 compared with the round slot variable camber vane. Below the 20% blade height, the total pressure loss coefficient of the preferred example 2 is reduced by about 0.1.

[0117] Please refer to Figure 12a and Figure 12b , it can be seen that for the round slot variable camber vane, the slot flow streamline occurs large-scale separation on the full span of the back blade suction surface 7, and the streamline near the tip region is particularly chaotic, so the near-tip region of the total pressure loss cloud at the 50% chord length section of the outlet of the round slot variable camber vane appears a high total pressure loss area. For the preferred example 2, the high total pressure loss area in the total pressure loss cloud at the 50% chord length section of the outlet is greatly reduced, and the total pressure loss intensity is also greatly reduced.

[0118] In the preferred example 3, the two-dimensional blade profile is designed using the partial design criteria of the present application.

[0119] The design index of the preferred example 3 is the maximum outlet geometric angle β max = 47°, the minimum outlet geometric angle β min = 0°, and the back blade camber is selected to be 12° according to θ = 0.5 * (β min + β max ) - s * (β max - β min ).

[0120] At the first angle of attack, the criterion for selecting the slit outlet width is, where Re > 125; at the minimum design angle of attack β min , i.e. the 0° outlet geometric angle state, the slit outlet width is specified to be ≈ 0 at this time, which ensures that the front and back blades do not geometrically interfere within the full angle of attack. During the rotation from 47° to 0°, the slit outlet width is continuously reduced to gradually block the slit at small angles of attack and reduce the mixing loss effect of the jet.

[0121] Under the conditions of the first angle of attack and the design required inlet Mach number of 0.3, the slit contraction ratio is changed with 0.5 as the initial value to perform CFD calculation and evaluation, the ratio of the slit outlet velocity and the main flow velocity u jet / u is controlled within the range of 1.0-1.1 to obtain the optimal contraction ratio of the slit. Further, the slit inlet width W in is calculated.

[0122] According to the width of the slit inlet and outlet, under the constraint of the outlet level, the upper half of the front blade trailing edge 8 is a circular arc with a radius The lower half of the front blade trailing edge 8 uses a cubic curve to transition with the pressure surface, and a horn-shaped slit inlet is constructed, which increases the total pressure of the slit inlet.

[0123] The curvature distribution of the rear blade suction surface is in a strong front loading form, and the maximum curvature point is located at the slit outlet.

[0124] Through CFD calculation, the preferred example 3 not only has lower loss at a design rear blade outlet geometric angle of 35°, but also has a useable angle range of more than 35°. The geometry of the preferred example 3 at a rear blade outlet geometric angle of 0° and 47° is as follows Figure 13 , Figure 14 .

[0125] Figure 15 is a comparison chart of total pressure loss of the preferred example 3 at different angles and the circular slit variable curvature guide vane, it can be seen that the rear blade suction surface 7 of the circular slit variable curvature guide vane appears open separation after 25 degrees, and the loss rises rapidly; the total pressure loss coefficient of the preferred example 3 is greatly reduced compared with the circular slit variable curvature guide vane in the entire angle range, and the useable outlet flow angle range is expanded from about 28° of the circular slit variable curvature guide vane to about 52°.

[0126] Figure 16 is a Mach number cloud chart of the preferred example 3 at a rear blade limit angle of 57°, it can be seen that the preferred example 3 rear blade suction surface 7 does not appear open separation phenomenon at the limit working condition of the rear blade angle of 57°.

[0127] The above describes the design method of the large turning angle variable curvature guide vane according to the embodiments of the present disclosure with reference to the accompanying drawings, through the high-degree blade overall modeling method, the rear blade solidity, slit width, slit contraction ratio, and curvature at the rear blade leading edge 9 are selected according to the design criteria to finely control the flow field of the key areas such as the slit and the slit outlet 4 of the variable curvature guide vane, the slit geometry at different blade heights and different angles is considered for radial stacking, and the beneficial effects of suppressing open separation of the airflow, controlling the loss, and improving the useable angle range of the variable curvature guide vane at multiple different angles, especially large angles are achieved.

[0128] By controlling the outlet width and contraction ratio of the slit, the jet velocity can be accurately controlled to achieve the best jet velocity, the curvature distribution form of the rear blade suction surface 7 and the maximum curvature of the leading edge are controlled through the modeling method, the open separation of the rear blade is prevented, and better wall attachment flow is achieved, so the present application can achieve a wider angle adjustment range than other variable curvature guide vanes, and smaller loss in the useable angle range.

[0129] CFD calculation results show that under the condition of incoming flow Mach number of 0.3, the outlet flow angle range of the variable-pitch guide vane is increased from not more than 27 degrees to not more than 41 degrees by using the blade profile designed according to the design principle of the application. Experimental results show that under the condition of incoming flow Mach number of 0.1, the outlet flow angle range of the variable-pitch guide vane is increased from not more than 25 degrees to not more than 40 degrees by using the blade profile designed according to the design principle of the application.

[0130] It should be noted that in some embodiments, the first rotation angle can be the maximum rotation angle, the second rotation angle can be the minimum rotation angle, and the third rotation angle can be another commonly used rotation angle other than the maximum rotation angle and the minimum rotation angle.

[0131] The above describes the basic principles of the present disclosure in combination with specific embodiments, but it should be noted that the advantages, advantages, effects and the like mentioned in the present disclosure are only examples and are not limiting, and these advantages, advantages, effects and the like cannot be considered as the various embodiments of the present disclosure must have. In addition, the specific details of the above disclosure are only for the purpose of example and for the purpose of understanding, and are not limited to the above specific details, and the present disclosure is not limited to the above specific details.

[0132] The block diagrams of the devices, apparatuses, equipment, systems involved in the present disclosure are only illustrative examples and are not intended to require or imply the connection, arrangement, configuration shown in the block diagram. As those skilled in the art will recognize, these devices, apparatuses, equipment, systems can be connected, arranged, configured in any manner. Words such as "include", "contain", "have" and the like are open-ended words, mean "including but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

[0133] In addition, as used herein, "or" used in the list of items starting with "at least one of indicates a separate list, so that, for example, "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e. A and B and C). In addition, the phrase "exemplary" does not mean that the described example is preferred or better than other examples.

[0134] It should also be noted that in the systems and methods of the present disclosure, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be considered as equivalents of the present disclosure.

[0135] Various changes, modifications, and alterations to the techniques described herein can be made without departing from the teachings of the attached claims. Moreover, the scope of the claims of this disclosure is not limited to the particular aspects described above. In addition, where a process, machine, manufacture, composition of matter, means, method, or result containing procedural, business, and other steps is described, it is understood that the description is meant to encompass the specific implementation of the steps described, as well as the substitution of equivalent steps, or equivalent steps in the performance order. Accordingly, the attached claims are to be interpreted as embracing the specific aspects and embodiments described herein, as well as future modifications, changes, and alterations of the aspects and embodiments.

[0136] The above description of the disclosed aspects is given to enable any person skilled in the art to make or use the disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0137] The above description has been given for illustrative and descriptive purposes. Further, this description is not intended to limit the embodiments of the present disclosure to the forms disclosed herein. Although various example aspects and embodiments have been discussed above, those of ordinary skill in the art will appreciate certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A method of designing a large turning angle variable camber vane, characterized by, The method comprises the following steps, S1, determining a design index, and determining a total chord length and a maximum thickness of the guide vane height according to the design index; S2, dividing the guide vane into a plurality of elements uniformly from a vane root to a vane tip, and projecting the guide vane into a two-dimensional plane; S3, determining a bending angle of a rear vane camber line of each element; S4, determining a rear vane solidity of each element, and determining a slot position according to the rear vane solidity; a criterion of the rear vane solidity is: wherein, is the rear vane solidity, is the design outlet geometric angle of the blade height at the first turning condition, is a constant coefficient; S5, calculating an outlet width of the slot of each element in a first turning angle state; S6, determining a contraction ratio of the slot in the first turning angle state; S7, generating a rear vane profile of each element; S8, determining the slot; S9, determining the slot in a third turning angle state; S10, determining a rotation center position of the rear vane of each element; S11, inversely transforming the element designed in the two-dimensional plane back to the element divided uniformly from the vane root to the vane tip, and performing radial stacking.

2. The design method of large turning angle variable camber vanes as set forth in claim 1, characterized in that, In step S3, the bending angle of the rear vane camber line is determined by the following formula, ； wherein, is the trailing edge camber, is the minimum exit geometric angle corresponding to the design requirement of the blade height position, is the maximum exit geometric angle of the design requirement of the blade height position, is a constant coefficient.

3. The design method of large turning angle variable camber vanes as set forth in claim 1, characterized in that, In step S5, the outlet width of the slot of each element in the first turning angle state is calculated by the following formula: ； wherein is the slit exit width to be selected for the blade height, TH is the maximum thickness of the blade at the blade height determined according to the design index, is the density of the flow in the first corner state, is the flow velocity in the main flow region in the first corner state, is the air viscosity, is a constant.

4. The design method of large turning angle variable camber vanes as set forth in claim 1, characterized in that, In step S6, a method for determining the contraction ratio of the slot in the first turning angle state is that a ratio of a slot outlet velocity to a main flow velocity is controlled to be between 1.0 and 1.1, and the contraction ratio is selected according to a flow Mach number, a Reynolds number and the first turning angle.

5. The design method of large turning angle variable camber vanes as recited in claim 1, wherein, In step S7, the rear vane profile of each element comprises, A curvature distribution form of a rear vane suction surface 7 is strong front loading, and a peak curvature position is located at a slot outlet; a parameterized modeling is used to generate an element profile of the rear vane at each vane height; and a selection criterion of the peak curvature is that an included angle between a jet flow at the slot outlet and a horizontal direction is less than 15 degrees.

6. The design method of large turning angle variable camber vanes as defined in claim 3, wherein, In step S8, a method for determining the slot is that an inlet width and an outlet width of the slot in the first turning angle state of each element are calculated, positions of a slot inlet point and a slot outlet point on a fore vane trailing edge profile are calculated, a rear half of a front wall surface profile of the slot is formed by using a circular arc horizontal to the slot outlet to connect the slot inlet and outlet points on the fore vane trailing edge, and a front half of the slot is formed by using a smooth curve to connect the slot inlet and a fore vane pressure surface.

7. The design method of large turning angle variable camber vanes as claimed in claim 6, wherein, A calculation formula of a radius of the circular arc is: ； wherein, is the slit entrance width, R is the radius of the circular arc, is the horizontal distance between the highest point under the first corner and the most forward point at the leading edge of the rear vane, is the vertical distance between the highest point under the first corner and the most forward point at the leading edge of the rear vane.

8. The design method of large turning angle variable camber vanes as claimed in claim 6, wherein, Step S9 comprises judging whether a third turning angle commonly used exists in addition to a maximum turning angle and a minimum turning angle. If the third turning angle exists, the slot inlet width and the slot outlet width in the commonly used turning angle are calculated according to step S4 and step S5.

9. The design method of large turning angle variable camber vanes as claimed in claim 8, wherein, Step S10 comprises, Positions satisfying the slot inlet width and the slot outlet width in the first turning angle state and the third turning angle state are taken as the rotation center position of the rear vane.

10. The design method of large deflection variable camber vanes according to any one of claims 1 to 9, characterized in that, Further comprising, S12, evaluating whether open separation exists in the first turning angle, and if the open separation exists, adjusting the rear vane solidity and the slot geometric parameters according to an evaluation result, and repeating steps S1 to S11 until the open separation does not exist in the first turning angle.

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