A straight-blade slat pre-swirl nozzle for turbines and its design method

Abstract

This application provides a design method for a straight-blade pre-swirl nozzle for turbines, comprising: determining the structural frame of the pre-swirl nozzle; determining the meridional channel structure of the pre-swirl nozzle; designing the straight-blade cascade of the pre-swirl nozzle, wherein the straight-blade cascade of the pre-swirl nozzle is designed using a modeling design method with the mid-diameter section as the base section; designing the width and shape of the throat of the pre-swirl nozzle blade cascade as a square or nearly square shape; controlling the length of the pre-swirl nozzle blade cascade channel so that the axial chord length of the blade is less than the length of the pre-swirl nozzle blade cascade channel; obtaining the blade profile parameters and coordinate points of the mid-diameter section of the blade cascade by controlling the main parameters of the blade cascade using the typical modeling parameter method; obtaining the three-dimensional model of the straight-blade cascade by radially stretching the base section blade profile; and adjusting the width of the blade cascade throat and the number of blades to ensure that the outlet airflow angle of the pre-swirl nozzle obtained from the design and simulation calculations meets the requirements, while gradually making the width of the blade cascade throat approach the blade cascade height, thus completing the iterative modeling design of the blade cascade.

Description

Technical Field

[0001] This application belongs to the field of turbine cooling design, and specifically relates to a straight-blade grid-type pre-swirl nozzle for turbines and its design method. Background Technology

[0002] As the turbine inlet temperature of aero engines, marine or industrial gas turbines is getting higher and higher, the high-pressure turbine inlet temperature has even reached 2200K and the low-pressure turbine inlet temperature has reached 1700K. Such a high turbine inlet temperature has exceeded the load-bearing capacity of the blades, and the existing materials and blade cooling technologies cannot meet the usage requirements.

[0003] The main purpose of a turbine pre-swirl nozzle is to accelerate airflow within the nozzle channel, creating an airflow with specific velocity, pressure, angle, and swirl ratio at the outlet to match the rotor's rotational speed. The airflow then enters the blade cavity along the rotating tenon structure, achieving the purpose of cooling the turbine blades. As a structure providing cooling air to the engine blades, the pre-swirl nozzle exhibits significantly different outlet cooling characteristics depending on its structure. The pre-swirl nozzle's structural form directly determines the cooling conditions entering the turbine blade cavity, greatly influencing the cooling effect on the blades.

[0004] Most current pre-swirl nozzles are straight circular orifice type. Figure 1 (as shown) or oblique hole type (such as) Figure 2 (As shown).

[0005] For a straight-hole nozzle consisting of several straight-circular holes of the same size on a ring plate, there is a large airflow deflection at the nozzle inlet, resulting in significant flow loss, poor airflow acceleration in the channel, and a low outlet swirl ratio. Consequently, its cooling effect on the working blades is not ideal, and its structural weight is large, which is not conducive to the weight reduction design of the engine turbine.

[0006] For the inclined hole type pre-swirl nozzle with an inlet that uses an expanding inclined hole and then contracting to form a smaller inclined hole structure, although it reduces some flow loss compared to the straight circular hole type, there is a large airflow deflection and flow resistance at the nozzle inlet. The acceleration in the hole channel is poor, there is a large flow loss, the outlet swirl ratio is low, and the mixing with the rotating fluid is poor, which is not conducive to the cooling of the working blades by the cold air. Summary of the Invention

[0007] The purpose of this application is to provide a straight-blade pre-swirl nozzle for turbines and its design method, in order to solve or mitigate at least one of the problems in the prior art.

[0008] The technical solution of this application is: a design method for a straight-blade pre-swirl nozzle for a turbine, the design method comprising:

[0009] Determine the structural framework of the pre-swirl nozzle;

[0010] The meridional channel structure of the pre-swirl nozzle is determined, wherein the inner cavity of the meridional channel of the pre-swirl nozzle is divided into an air inlet cavity and a blade cavity, and the air inlet cavity is designed in a converging form;

[0011] The process of designing the pre-swirling nozzle straight blade cascade includes:

[0012] The pre-swirl nozzle straight blade grating is designed using a modeling design method with the medium diameter section as the base section;

[0013] The shape of the throat width of the pre-swirl nozzle is designed to be square or nearly square, thereby minimizing the wetted periphery area of ​​the blade passage, and the blade height of the pre-swirl nozzle is calculated.

[0014] Control the length of the pre-swirl nozzle blade passage so that the blade is completely contained within the pre-swirl nozzle blade passage, ensuring that the axial chord length of the blade is less than the length of the pre-swirl nozzle blade passage, while leaving axial length margin at the blade inlet and outlet.

[0015] By controlling the main parameters of the blade cascade and using the typical modeling parameter method, the modeling parameters and coordinate points of the blade cascade mid-diameter section are obtained through the modeling design of the pre-swirl nozzle blade cascade surface. The three-dimensional model of the straight blade cascade is obtained by radially stretching the base section blade profile. By adjusting the width of the blade cascade throat and the number of blades, the outlet airflow angle of the pre-swirl nozzle obtained from the design and simulation calculation meets the requirements. At the same time, the width of the blade cascade throat is gradually made close to the height of the blade cascade, thus completing the iterative modeling design of the blade cascade.

[0016] In a preferred embodiment of this application, the structural frame of the pre-swirl nozzle includes: a straight blade grid, an inner support ring, an inner sealing ring, and an outer sealing ring;

[0017] The inner support ring is fixedly connected to the inner sealing ring. The outer sealing ring is fixed to the inner support ring on one side and overlapped on the other side. The straight blade cascade is fixed to the outer wall surface of the inner sealing ring. Several circular holes are opened on the inner support ring to allow airflow to enter the pre-swirl nozzle through the circular holes. The number of circular holes is equal to the number of blades, and the circular holes are directly opposite the middle position of the circumferential channel of the blade cascade.

[0018] In a preferred embodiment of this application, the straight blade grid is fixed to the outer wall surface of the inner sealing ring by welding, or the straight blade grid is fixed to the outer wall surface of the inner sealing ring by inserting and welding after drilling holes in the inner sealing ring.

[0019] In a preferred embodiment of this application, the upper end wall flow channel of the intake chamber is connected to the upper end wall of the blade cavity via a Bezier curve to form a contraction angle θ1 ranging from 60° to 70°, and the lower end wall flow channel of the intake chamber is connected to the lower end wall of the blade cavity via two straight lines to form an expansion angle θ2 ranging from 15° to 25°.

[0020] In a preferred embodiment of this application, the process of calculating the pre-swirl nozzle blade height H1 is as follows:

[0021] The minimum height H of the pre-rotating nozzle blades to achieve the required cooling air volume is calculated using the following process. 1min :

[0022]

[0023] λ 实际 ≈(0.8~0.9)·λ 理论

[0024]

[0025]

[0026] R 中径 ≈R 引气孔中径 -2

[0027]

[0028] According to the flow conservation equation, assuming that the inlet and outlet densities and areas of the pre-swirling nozzle blade cavity remain consistent, that is:

[0029] ρ1C 1a A1=ρ2C 2a A2

[0030] ρ1A1=ρ2A2

[0031] The axial components of the inlet and outlet velocities of the pre-swirling nozzle vane cavity are equal, i.e., C 1a ≈C 2a .

[0032] According to the swirl ratio equation, assuming the swirl ratio is 1, we have:

[0033] SR=C 2u / u2=1

[0034] C 2a / C 2u =tanα

[0035] ρ2C 2a A2=m

[0036]

[0037] Make the cascade height H1 > H 1min The cascade height H1 was calculated.

[0038] In a preferred embodiment of this application, the axial length L1 of the blade channel is designed to be in the range of L1 = 15mm to 30mm;

[0039] The design range for the axial chord length L2 of the blade cascade is L1-L2=2mm~6mm.

[0040] In a preferred embodiment of this application, during the iteration process, the key parameters of the pre-swirl nozzle straight blade cascade base section airfoil are selected as follows:

[0041] Leading edge diameter: D1 = 1.5mm~2.5mm

[0042] Tail edge diameter: D2 = 0.4mm~0.8mm

[0043] Maximum thickness: C max =3mm~8mm

[0044] Imported geometric angle: β q =85°~95°

[0045] The adjusted number of blades must meet the following requirements:

[0046] ρ 喉部 C 喉部 A 喉部 =m

[0047]

[0048] A 喉部 =t·H1·n

[0049] Number of leaves

[0050] In a preferred embodiment of this application, the design method further includes:

[0051] By modeling and meshing the inlet chamber, blade cascade chamber, outlet chamber, and rotor blade air supply groove of the pre-swirl nozzle, and controlling the inlet and outlet boundary conditions according to the inlet and outlet pressure, temperature, and flow requirements of each chamber, a multi-chamber three-dimensional coupled simulation calculation is carried out to identify the structure that affects the performance of the pre-swirl nozzle. This structure includes the blade profile, the inlet chamber circular hole, and the air duct of the front sealing ring. A single variable is used to control the structure to achieve the optimized design and simulation iteration of the structure.

[0052] In a preferred embodiment of this application, the process of controlling the structure using a single variable includes:

[0053] a) Optimize only the blade profile parameters while keeping others unchanged to obtain better blade profile parameters;

[0054] b) Change parameters such as the diameter and circumferential position of the intake chamber orifice, while keeping other parameters unchanged, to obtain better orifice parameters;

[0055] c) By changing the diameter and angle of the air intake hole of the front sealing ring while keeping other parameters unchanged, better air intake hole parameters can be obtained, which can further improve the performance of the pre-swirl nozzle.

[0056] Finally, this application also provides a straight-blade slat type pre-swirl nozzle for a turbine, which is obtained by any of the above-described design methods for a straight-blade slat type pre-swirl nozzle for a turbine.

[0057] Compared with existing technologies, the straight-leaf cascade design method of this application has the following advantages:

[0058] 1) The straight blade grid of the pre-swirl nozzle is fixed by welding to the inner wall of the inner sealing ring or by inserting it into the inner sealing ring and then welding it to the outer wall. This facilitates the individual processing and manufacturing of the blades and their replacement after damage. By opening several round holes in the inner support ring, the airflow enters the pre-swirl nozzle through the round holes, thus enabling the inner support ring to perform the air intake function.

[0059] 2) Compared with the traditional equal inner diameter or equal outer diameter contraction form, the upper flow channel of the straight blade grid type pre-swirl nozzle inlet cavity adopts one section of Bezier curve control and the lower flow channel adopts two sections of straight line control, which is designed as a slope trajectory contraction form. The larger contraction degree can improve the acceleration of airflow and reduce flow loss.

[0060] 3) The design of the blade profile is reduced by using the medium diameter base section method. By controlling the swirl ratio and throat width shape, typical design methods such as the number of blades, blade height, leading and trailing edge diameters, and maximum thickness are used to achieve the straight blade profile design of the pre-swirling nozzle in a small space. This minimizes the friction loss and flow loss of the blade profile and improves the aerodynamic performance of the pre-swirling nozzle.

[0061] 4) By performing multi-disc, three-dimensional coupled simulation calculations on the inlet chamber, blade cascade chamber, outlet chamber, and rotor blade air supply groove of the pre-swirl nozzle, factors that significantly affect the performance of the pre-swirl nozzle are identified. Optimization design and simulation iterations using a single-variable control method can further improve the performance of the pre-swirl nozzle. Attached Figure Description

[0062] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0063] Figure 1 This is a schematic diagram of the existing straight circular orifice type pre-swirling nozzle structure.

[0064] Figure 2 This is a schematic diagram of the existing inclined hole type pre-swirl nozzle structure.

[0065] Figure 3 This is a schematic diagram of the design method for the straight-blade grid-type pre-swirl nozzle of this application.

[0066] Figure 4 This is a schematic diagram of the straight-blade grid-type pre-swirl nozzle structure frame in this application.

[0067] Figure 5 This is a schematic diagram of the meridional flow channel of the straight-blade grid-type pre-swirling nozzle in this application.

[0068] Figure 6 This is a schematic diagram of the aerodynamic design parameters of the straight blade cascade surface in this application.

[0069] Figure 7 This is a schematic diagram of the streamline distribution of the coupled simulation model of the pre-swirl nozzle system in this application.

[0070] Figure 8 This is a top view of the three-dimensional flow field of a straight-blade pre-swirling nozzle in one embodiment of this application.

[0071] Figure 9 This is a front view of the three-dimensional flow field of a straight-blade pre-swirling nozzle in one embodiment of this application. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0073] like Figure 3 As shown, the design method for a straight-blade pre-swirl nozzle for turbines provided in this application designs a straight-blade pre-swirl nozzle based on the nozzle inlet and outlet pressure ratio π, converted flow rate m, and outlet airflow angle α provided by the air system specialist. The design method specifically includes the following steps:

[0074] Step 1: Determine the structural framework of the pre-swirl nozzle

[0075] like Figure 4 The diagram shows the structural framework of a straight-blade pre-swirl nozzle 10. This nozzle mainly consists of a straight blade cascade 11, an inner support ring 12, an inner sealing ring 13, and an outer sealing ring 14. The inner support ring 12 and the inner sealing ring 13 are fixedly connected by bolts. The outer sealing ring 14 is fixed to the inner support ring 12 on one side by bolts and on the other side by a stop structure. The straight blade cascade 11 is fixed to the outer wall of the inner sealing ring 13 by welding or by inserting and welding through holes drilled in the inner sealing ring 13. Several circular holes 121 are formed on the inner support ring 12 to allow airflow into the pre-swirl nozzle. The number of circular holes 121 is generally equal to the number of blades, and the holes 121 are positioned directly opposite the center of the circumferential channel of the blade cascade.

[0076] Step 2: Determine the meridional channel structure of the pre-swirl nozzle.

[0077] like Figure 5 The diagram shows a schematic of the meridional flow channel structure of the pre-swirling nozzle. In this application, the inner cavity of the straight-blade pre-swirling nozzle is divided into an inlet cavity 21 and a blade cavity 22. To improve the acceleration of the cooled air, the inlet cavity 21 is designed with a large-amplitude contraction. Compared with the traditional constant inner diameter or constant outer diameter contraction, the end of the flow channel 23 on the upper wall of the inlet cavity 21 is connected to the upper wall of the blade cavity via a Bezier curve 231, with a contraction angle θ1 ranging from 60° to 70°. The flow channel 24 on the lower wall of the inlet cavity 21 is connected to the lower wall of the blade cavity via two straight lines—a front straight line 241 and a rear straight line 242—with an expansion angle θ2 ranging from 15° to 25°. The flow channel of the inlet cavity 21 forms a downward-sloping trajectory contraction. To match the surface contraction of the straight blade, the upper and lower walls of the blade cavity 22 adopt straight-line channels.

[0078] Step 3: Design of pre-swirling nozzle straight blade cascade

[0079] 3.1) The pre-swirl nozzle straight blade cascade adopts the modeling design method with the medium diameter section as the basic section. Compared with the traditional three basic section modeling method, it can reduce the amount of blade parameter design. At the same time, the resulting straight blade is easier to manufacture and process than the bent and twisted blade cascade.

[0080] 3.2) Aerodynamically, the airflow at the pre-swirl nozzle outlet is axially introduced relative to the rotor blades, ensuring that the tangential velocity component at the pre-swirl nozzle outlet is comparable to the circumferential velocity at the diameter of the air intake hole in the rotor's front sealing ring, i.e., the swirl ratio SR at the nozzle outlet is close to 1. The throat width and shape of the pre-swirl nozzle blade cascade in a relatively small space are designed to be close to square, minimizing the wetted periphery area of ​​the blade cascade channel. At this point, friction and flow losses can be minimized, which is beneficial for the outflow of cold air.

[0081] The height H1 of the pre-swirling nozzle blade cascade is calculated as follows:

[0082]

[0083] λ 实际 ≈(0.8~0.9)·λ 理论 (2)

[0084]

[0085]

[0086] R 中径 ≈R 引气孔中径 -2(5)

[0087]

[0088] The pre-swirl nozzle blade height calculated using the above formula represents the minimum blade height H required to achieve the desired cooling air volume.1min .

[0089] According to the flow conservation equation, assuming that the inlet and outlet densities and areas of the pre-swirling nozzle blade cavity remain consistent, that is:

[0090] ρ1C 1a A1=ρ2C 2a A2(7)

[0091] ρ1A1=ρ2A2(8)

[0092] It can be seen that the axial component velocities at the inlet and outlet of the pre-swirling nozzle blade cavity are equal, i.e., C 1a ≈C 2a .

[0093] According to the swirl ratio equation, assuming the swirl ratio is 1, we have:

[0094] SR=C 2u / u2=1(9)

[0095] C 2a / C 2u =tanα(10)

[0096] ρ2C 2a A2=m(11)

[0097]

[0098] The blade height H1 can be calculated from the above formula, satisfying H1 > H 1min ;

[0099] Where parameter p in p out , k, m, α, π, R 引气孔中径 All of these are known quantities.

[0100] 3.3) Considering the compact structure and limited space of the pre-swirl nozzle, the length L1 of the pre-swirl nozzle blade passage needs to be controlled. All blades should be contained within the pre-swirl nozzle blade passage. During design, the axial chord length L2 of the blades should be less than the length L1 of the pre-swirl nozzle blade passage. Simultaneously, a certain axial length margin should be reserved at the blade inlet and outlet, i.e.:

[0101] The design range for the axial length L1 of the blade passage is: L1 = 15mm ~ 30mm;

[0102] The design range of the axial chord length L2 of the blade cascade is: L1-L2 = 2mm to 6mm.

[0103] 3.4) The pre-swirl nozzle blade design adopts the medium diameter section as the blade base section, and controls the leading and trailing edge diameters D1 and D2, and the maximum thickness C of the blade. max Geometric angle β of inlet and outlet qand β h The main parameters, such as throat width t, number of blades n, and the two sections of Bézier curves on the blade base and back side, are determined using the typical styling parameter method (see blade profile styling parameters). Figure 6 As shown, the design of the pre-rotating nozzle blade profile is realized, and the blade profile parameters and coordinate points of the mid-diameter section of the blade profile are obtained. The three-dimensional model of the straight blade profile can be obtained by radially stretching the base section blade profile.

[0104] The key parameters for the airfoil profile of the pre-swirling nozzle straight blade cascade section are selected as follows:

[0105] Leading edge diameter: D1 = 1.5mm~2.5mm

[0106] Tail edge diameter: D2 = 0.4mm~0.8mm

[0107] Maximum thickness: C max =3mm~8mm

[0108] Imported geometric angle: β q =85°~95°

[0109] Based on the method proposed in step 3.2 that the throat width shape of the pre-swirl nozzle blade cascade should be close to square, and assuming the blade cascade height H1 is determined, the following formula applies:

[0110] ρ 喉部 C 喉部 A 喉部 =m (13)

[0111]

[0112] A 喉部 =t·H1·n(15)

[0113] We can obtain,

[0114] During the iterative design of the blade cascade, the throat width and the number of blades can be adjusted according to the above formula so that the pre-swirling nozzle outlet airflow angle obtained from the design and simulation calculation meets the requirements, while the throat width gradually approaches the blade cascade height.

[0115] 3.5) By modeling and meshing the pre-swirling nozzle inlet chamber, blade cascade chamber, outlet chamber, and rotor blade air supply groove, and controlling the inlet and outlet boundary conditions according to the inlet and outlet pressure, temperature, and flow rate requirements of each chamber, a multi-disc chamber three-dimensional coupled simulation calculation is carried out. The streamline distribution of the three-dimensional simulation model is shown in the figure. Figure 7 The blade profile, inlet cavity orifice, and front sealing ring bleed hole were identified as having a significant impact on the performance of the pre-swirl nozzle. A single-variable control method was employed for optimization design and simulation iteration, including:

[0116] a) Optimize only the blade profile parameters while keeping others unchanged to obtain better blade profile parameters;

[0117] b) Change parameters such as the diameter and circumferential position of the intake chamber orifice, while keeping other parameters unchanged, to obtain better orifice parameters;

[0118] c) By changing the diameter and angle of the air intake hole of the front sealing ring while keeping other parameters unchanged, better air intake hole parameters can be obtained, which can further improve the performance of the pre-swirl nozzle.

[0119] The key parameters of the pre-swirling nozzle corresponding to the three-dimensional model of the straight blade pre-swirling nozzle of a high-pressure turbine, completed using the method of this application, are shown in Table 1:

[0120] Table 1 Typical parameters of straight-blade pre-swirl nozzle

[0121]

[0122]

[0123] like Figure 8 and Figure 9 The figure shown is a three-dimensional flow field diagram of the straight blade pre-swirling nozzle in the table above. It can be seen from the three-dimensional flow field that the flow field at the outlet of the pre-swirling nozzle is uniform and the flow velocity is fast. Therefore, the performance loss of the pre-swirling nozzle is low and the cooling effect on the working blades behind it is good.

[0124] Compared with existing technologies, the straight-leaf cascade design method of this application has the following advantages:

[0125] 1) The straight blade grid of the pre-swirl nozzle is fixed by welding to the inner wall of the inner sealing ring or by inserting it into the inner sealing ring and then welding it to the outer wall. This facilitates the individual processing and manufacturing of the blades and their replacement after damage. By opening several round holes in the inner support ring, the airflow enters the pre-swirl nozzle through the round holes, thus enabling the inner support ring to perform the air intake function.

[0126] 2) Compared with the traditional equal inner diameter or equal outer diameter contraction form, the upper flow channel of the straight blade grid type pre-swirl nozzle inlet cavity adopts one section of Bezier curve control and the lower flow channel adopts two sections of straight line control, which is designed as a slope trajectory contraction form. The larger contraction degree can improve the acceleration of airflow and reduce flow loss.

[0127] 3) The design of the blade profile is reduced by using the medium diameter base section method. By controlling the swirl ratio and throat width shape, typical design methods such as the number of blades, blade height, leading and trailing edge diameters, and maximum thickness are used to achieve the straight blade profile design of the pre-swirling nozzle in a small space. This minimizes the friction loss and flow loss of the blade profile and improves the aerodynamic performance of the pre-swirling nozzle.

[0128] 4) By performing multi-disc, three-dimensional coupled simulation calculations on the inlet chamber, blade cascade chamber, outlet chamber, and rotor blade air supply groove of the pre-swirl nozzle, factors that significantly affect the performance of the pre-swirl nozzle are identified. Optimization design and simulation iterations using a single-variable control method can further improve the performance of the pre-swirl nozzle.

[0129] Symbol explanation:

[0130] π is the expansion ratio of the pre-swirling nozzle.

[0131] m is the flow rate of the pre-swirling nozzle.

[0132] α is the outlet airflow angle of the pre-swirling nozzle.

[0133] θ1 is the contraction angle of the upper flow channel of the intake chamber.

[0134] θ2 is the expansion angle of the lower flow channel of the intake chamber.

[0135] H1 is the height of the pre-swirling nozzle blade cascade.

[0136] H 1min Minimum height of pre-swirling nozzle blades

[0137] p is the static pressure of the pre-swirling nozzle.

[0138] p* represents the total pressure of the pre-swirling nozzle.

[0139] p in Total pressure at the inlet of the pre-swirl nozzle

[0140] p out For the static pressure at the outlet of the pre-swirl nozzle

[0141] π(λ 理论 () is an aerodynamic function, i.e., the theoretical total static pressure ratio of the pre-swirling nozzle.

[0142] λ 理论 Theoretical speed coefficient

[0143] λ 实际 Actual speed coefficient

[0144] q(λ 实际 ) is the actual flow function

[0145] k is the adiabatic index.

[0146] A is the annular area of ​​the pre-swirl nozzle channel.

[0147] T * Total temperature of the air conditioner

[0148] R 中径 The median diameter of the pre-swirling nozzle blade cascade

[0149] R 引气孔中径 The diameter of the air vent of the front sealing ring

[0150] β1 is the inlet airflow angle of the cascade.

[0151] β2 is the airflow angle at the cascade exit.

[0152] C 1a Axial velocity at the inlet of the pre-rotating nozzle

[0153] C 2a The axial velocity at the outlet of the pre-swirl nozzle

[0154] C 2u The circumferential velocity at the pre-swirl nozzle exit

[0155] u2 is the circumferential tangential velocity.

[0156] A1 is the inlet annular area of ​​the pre-swirl nozzle.

[0157] A2 is the outlet ring area of ​​the pre-swirl nozzle.

[0158] L1 is the axial length of the pre-swirl nozzle blade passage.

[0159] L2 is the axial chord length of the pre-swirl nozzle blade cascade.

[0160] β q For the inlet geometry of the cascade

[0161] β h The exit geometry of the cascade

[0162] D1 is the diameter of the leading edge of the cascade.

[0163] D2 is the diameter of the trailing edge of the cascade.

[0164] C max Maximum thickness of the blade cascade

[0165] ρ 喉部 airflow density

[0166] C 喉部 The axial velocity of the pre-rotating nozzle throat

[0167] A 喉部 For the pre-rotating nozzle throat area

[0168] t is the width of the cascade throat.

[0169] n is the number of leaves

[0170] SR stands for swirl ratio (the ratio of the tangential velocity of the airflow to its rotational velocity).

[0171] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A design method for a straight-blade slat pre-swirl nozzle for a turbine, characterized in that, The design method includes: Determine the structural framework of the pre-swirl nozzle; The meridional channel structure of the pre-swirl nozzle is determined, wherein the inner cavity of the meridional channel of the pre-swirl nozzle is divided into an air inlet cavity and a blade cavity, and the air inlet cavity is designed in a converging form; The process of designing the pre-swirling nozzle straight blade cascade includes: The pre-swirl nozzle straight blade grating is designed using a modeling design method with the medium diameter section as the base section; The throat width of the pre-swirl nozzle is designed to be square or nearly square to minimize the wetted periphery area of ​​the blade passage. The blade height of the pre-swirl nozzle is calculated as follows: the minimum height of the pre-swirl nozzle blade to achieve the required cooling air volume is calculated using the following process. : ； ； ； ； ； ； In the formula, p is the static pressure of the pre-swirling nozzle, p* is the total pressure of the pre-swirling nozzle, and p in p is the total pressure at the inlet of the pre-swirling nozzle. out The static pressure at the pre-swirl nozzle outlet. The aerodynamic function is the theoretical total static pressure ratio of the pre-swirling nozzle, k is the adiabatic index, and λ is the aerodynamic function. 理论 λ is the theoretical velocity coefficient. 实际 This is the actual speed coefficient. Here, m is the actual flow rate function, and m is the pre-swirling nozzle flow rate. The area of ​​the pre-swirled nozzle channel ring is... This is the total temperature of the air conditioner. The median diameter of the pre-swirling nozzle blade cascade, The diameter of the air vent of the front sealing ring is [missing information]. This represents the minimum height of the pre-swirling nozzle blade cascade. According to the flow conservation equation, assuming that the inlet and outlet densities and areas of the pre-swirling nozzle blade cavity remain consistent, that is: , In the formula, The inlet airflow angle of the blade cascade. C is the airflow angle at the cascade exit. 1a C represents the axial velocity at the inlet of the pre-rotating nozzle. 2a A1 is the axial velocity at the outlet of the pre-swirling nozzle, A2 is the inlet ring area of ​​the pre-swirling nozzle, and A2 is the outlet ring area of ​​the pre-swirling nozzle. The axial components of the inlet and outlet velocities of the pre-swirling nozzle vane cavity are equal, i.e. ; According to the swirl ratio equation, assuming the swirl ratio is 1, we have: ； ； ； ； In the formula, C is the swirl ratio. 2u Let u1 be the circumferential velocity at the pre-swirl nozzle exit, u2 be the circumferential tangential velocity, and α be the airflow angle at the pre-swirl nozzle exit. This refers to the height of the pre-swirling nozzle blade cascade. Increase the height of the cascade The cascade height H1 is calculated. Control the length of the pre-swirl nozzle blade passage so that the blade is completely contained within the pre-swirl nozzle blade passage, ensuring that the axial chord length of the blade is less than the length of the pre-swirl nozzle blade passage, while leaving axial length margin at the blade inlet and outlet. By controlling the main parameters of the blade cascade and employing the typical modeling parameter method, the blade profile of the pre-swirl nozzle was designed to obtain the blade profile parameters and coordinate points of the mid-diameter section. A three-dimensional model of the straight blade cascade was obtained by radially stretching the base section blade profile. By adjusting the throat width and the number of blades, the outlet airflow angle of the pre-swirl nozzle obtained from the design and simulation calculations was made to meet the requirements. Simultaneously, the throat width of the blade cascade was gradually made to approach the blade height, completing the iterative modeling design of the blade cascade. During the iteration process, the key parameters of the base section blade profile of the straight blade cascade of the pre-swirl nozzle were selected as follows: Leading edge diameter: =1.5mm~2.5mm Tail margin diameter: =0.4mm~0.8mm Maximum thickness: =3mm~8mm Imported geometric angles: =85°~95° The adjusted number of blades must meet the following requirements: ； ； ； Number of leaves ; In the formula, ρ 喉部 For airflow density, C 喉部 A represents the axial velocity of the pre-swirling nozzle throat. 喉部 t is the throat area of ​​the pre-swirling nozzle, t is the throat width of the blade cascade, and n is the number of blades.

2. The design method for a straight-blade pre-swirl nozzle for a turbine as described in claim 1, characterized in that, The pre-rotating nozzle's structural frame includes: a straight blade grid (11), an inner support ring (12), an inner sealing ring (13), and an outer sealing ring (14). The inner support ring (12) is fixedly connected to the inner sealing ring (13). The outer sealing ring (14) is fixed to the inner support ring (12) on one side and overlapped on the other side. The straight blade cascade (11) is fixed to the outer wall of the inner sealing ring (13). Several circular holes (121) are opened on the inner support ring (12) to allow airflow to enter the pre-rotating nozzle through the circular holes (121). The number of circular holes (121) is equal to the number of blades, and the circular holes (121) are directly opposite the middle position of the circumferential channel of the blade cascade.

3. The design method for a straight-blade cascade pre-swirl nozzle for a turbine as described in claim 2, characterized in that, The straight blade grid (11) is fixed to the outer wall of the inner sealing ring (13) by welding, or the straight blade grid (11) is fixed to the outer wall of the inner sealing ring (13) by making a hole in the inner sealing ring (13), inserting and welding.

4. The design method for a straight-blade slat pre-swirl nozzle for a turbine as described in claim 1, characterized in that, The upper wall flow channel (23) of the intake cavity (21) is connected to the upper wall of the blade cavity via a Bezier curve (231) to form a contraction angle θ1 ranging from 60° to 70°. The lower wall flow channel (24) of the intake cavity (21) is connected to the lower wall of the blade cavity via two straight lines to form an expansion angle θ2 ranging from 15° to 25°.

5. The design method for a straight-blade cascade pre-swirl nozzle for a turbine as described in claim 1, characterized in that, The design range of the axial length L1 of the cascade channel is: =15mm~30mm; The design range of the axial chord length L2 of the blade cascade is: - =2mm~6mm.

6. The design method for a straight-blade cascade pre-swirl nozzle for a turbine as described in claim 1, characterized in that, The design method further includes: By modeling and meshing the inlet chamber, blade cascade chamber, outlet chamber, and rotor blade air supply groove of the pre-swirl nozzle, and controlling the inlet and outlet boundary conditions according to the inlet and outlet pressure, temperature, and flow requirements of each chamber, a multi-chamber three-dimensional coupled simulation calculation is carried out to identify the structure that affects the performance of the pre-swirl nozzle. This structure includes the blade profile, the inlet chamber circular hole, and the air duct of the front sealing ring. A single variable is used to control the structure to achieve the optimized design and simulation iteration of the structure.

7. The design method for a straight-blade pre-swirl nozzle for a turbine as described in claim 6, characterized in that, The process of controlling the structure using a single variable includes: a) Optimize only the blade profile parameters while keeping others unchanged to obtain better blade profile parameters; b) Change the diameter and circumferential position parameters of the intake chamber orifice, while keeping other parameters unchanged, to obtain better orifice parameters; c) Change the diameter and slope of the air intake hole of the front sealing ring, while keeping other parameters unchanged, to obtain better air intake hole parameters and further improve the performance of the pre-swirl nozzle.

8. A straight-blade grid-type pre-swirl nozzle for a turbine, characterized in that, The straight-blade grid-type pre-swirl nozzle is obtained by the design method of the turbine straight-blade grid-type pre-swirl nozzle as described in any one of claims 1 to 7.

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