CN114382557B - Test structure for simulating turbine dynamic and static disc cavity leakage flow prerotation - Google Patents

Test structure for simulating turbine dynamic and static disc cavity leakage flow prerotation Download PDF

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CN114382557B
CN114382557B CN202210028951.4A CN202210028951A CN114382557B CN 114382557 B CN114382557 B CN 114382557B CN 202210028951 A CN202210028951 A CN 202210028951A CN 114382557 B CN114382557 B CN 114382557B
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turbine
leakage flow
blade
cascade
static
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CN114382557A (en
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刘钊
谢晔航
张韦馨
丰镇平
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Xian Jiaotong University
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Xian Jiaotong University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/003—Arrangements for testing or measuring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
    • F01D11/003—Preventing or minimising internal leakage of working-fluid, e.g. between stages by packing rings; Mechanical seals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
    • F01D11/08—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

A test structure for simulating pre-rotation of leakage flow of a moving and static disk cavity of a turbine comprises a gas collection cavity with a plurality of gas inlets, the gas collection cavity is communicated with a gap of the moving and static disk cavities, the gap of the moving and static disk cavities is communicated with a flange sealing structure, the flange sealing structure is positioned below a plane blade grid test bed, a pre-rotation structure is arranged on the top surface of the flange sealing structure, a turbine movable blade is arranged on the plane blade grid test bed, the pre-rotation structure is positioned at the upstream of the turbine movable blade, the leakage flow enters the gas collection cavity from the gas inlets and then enters the gap of the moving and static disk cavities, then flows through the flange sealing structure and the pre-rotation structure and enters a blade grid channel of the plane blade grid test bed. The design of the dynamic and static disc cavity gap and the wheel rim sealing structure refers to an actual turbine, so that the test result is closer to the actual turbine.

Description

Test structure for simulating turbine dynamic and static disc cavity leakage flow prerotation
Technical Field
The invention belongs to the technical field of flow, cooling and heat exchange of turbine blades of an aero-engine, and particularly relates to a test structure for simulating prerotation of leakage flow of a moving and static disc cavity of a turbine.
Background
The gas turbine has the advantages of large power density, small volume, light weight, high start-stop speed and the like, and is widely applied to the industrial fields of aviation propulsion, ship power, land power generation and the like. The increase of the inlet temperature of the gas turbine is a necessary trend of the development of the gas turbine, which increases the cycle thermal efficiency and specific work of the gas turbine and also causes the increase of the thermal load borne by the hot end part of the turbine, thereby causing thermal fatigue and high-temperature creep, seriously affecting the normal operation of parts and reducing the service life of the parts. Therefore, the research on the cooling technology of the hot-end component is particularly necessary.
Intrusion of high temperature mainstream combustion gases into the disk cavity in the turbine can affect disk life and reliability. Therefore, a method of introducing a flow of cold air to increase the pressure inside the disk chamber and suppress the invasion of the hot gas is generally adopted, and the flow of cold air flowing out from the inside of the disk chamber to the main flow channel is called a leakage flow. The leakage flow of the dynamic and static disk cavities can not only prevent the gas from invading the disk cavities, but also can be used for cooling the movable impeller disk. At present, research on the flowing, cooling and heat exchange characteristics of leakage flow of a moving disc cavity and a fixed disc cavity becomes a hot point in the field, but the prerotation phenomenon of the leakage flow of a gap between the moving disc cavity and the fixed disc cavity at the upstream of a moving impeller disc is difficult to effectively simulate in a static plane cascade test bench, and the test result lacks sufficient persuasion.
Disclosure of Invention
In order to overcome the limitation of the existing test structure, the prerotation phenomenon of the leakage flow of the clearance between the upstream moving disk cavity and the upstream moving disk cavity of the moving impeller disk is simulated on a static plane cascade test bed, the invention aims to provide the test structure for simulating the prerotation of the leakage flow of the moving disk cavity and the moving disk cavity of the turbine.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a simulation turbine sound dish chamber leakage flow test structure of prewhirling, includes the gas collecting cavity that has a plurality of air inlets, gas collecting cavity and sound dish chamber clearance intercommunication, sound dish chamber clearance and rim seal structure intercommunication, rim seal structure is located plane cascade test bench below, and its top surface sets up the prewhirling structure, and the turbine movable vane sets up on plane cascade test bench, and the prewhirling structure is located turbine movable vane upper reaches, and the leakage flow gets into the gas collecting cavity from the air inlet earlier, gets into sound dish chamber clearance again, then flows through rim seal structure and prewhirling structure, gets into in the cascade passageway of plane cascade test bench.
In one embodiment, the dynamic and static disc cavity gap and the flange sealing structure refer to a dynamic and static disc cavity flange sealing structure in an actual turbine, the dynamic and static disc cavity gap is a gap between a static impeller disc and a movable impeller disc, and a cuboid cavity structure is adopted; the rim sealing structure is used for sealing a disc cavity in an actual turbine and adopts a tooth-shaped structure, and the top surface, namely an outlet, of the rim sealing structure is the bottom surface, namely an inlet, of the prerotation structure.
In one embodiment, the prerotation structure is tens of identical rectangular holes with an inclination angle theta in the circumferential direction, and is used for introducing leakage flow in a clearance between a moving disc cavity and a static disc cavity into a blade cascade channel of a plane blade cascade test bed and generating a velocity component in the circumferential direction; seen from the end wall of the movable blade, the outlets of the pre-rotation structure are two rows of rectangular holes which are arranged in a staggered mode and are distributed at the upstream position of the turbine movable blade.
In one embodiment, the pre-rotation structure is angled to point to the suction side of the turbine bucket.
In one embodiment, the inclination angle θ of the rectangular hole is selected from 0 to 90 °, and the magnitude of the inclination angle θ depends on the swirl ratio of the leakage flow to be simulated, and the swirl ratio is defined as follows:
Figure BDA0003465627970000021
wherein v is leakage flow Is the absolute velocity of the leakage flow u blade Is the speed of the impeller disc, v relative For the velocity of the leakage flow relative to the moving impeller disc, i.e. the leakage flow velocity at the outlet of the pre-swirl structure, the subscript u represents the circumferential component of this velocity; therefore, when the leakage flow speed of the outlet of the prerotation structure is the same, the larger the inclination angle theta of the prerotation structure is, the larger the circumferential speed component is, and the lower the simulated leakage flow swirl ratio SR is.
In one embodiment, the turbine rotor blade is a straight blade, the blade profile line of the straight blade is selected from the profile line of the section of the actual turbine rotor blade at a certain blade height and is stretched in the vertical direction, and the axial chord length C of the turbine rotor blade ax The axial chord length of the section at the blade height of the actual turbine rotor blade is obtained, and the cascade pitch P of the turbine rotor blade is taken as the cascade pitch of the section at the blade height of the actual turbine rotor blade.
In one embodimentWherein the air inlets are a plurality of hollow cylindrical holes which are arranged at equal intervals in the circumferential direction, 1 air inlet is arranged on the length of each cascade pitch P, and the ratio phi between the outer diameter of each air inlet and the pitch of the cascade 1 P =0.12-0.16, ratio of inner diameter to cascade pitch phi 2 P =0.06-0.08; the outlet width D of the rim sealing structure is 0.06C ax -0.12C ax (ii) a The axial projection distance L of the pre-rotation structure relative to the turbine movable blade LE Value of 0.3C ax -0.5C ax The axial width D of the pre-rotation structure distribution swirl The same width D as the rim seal outlet, i.e. D swirl = D, circumferential length L of distribution swirl 2 times or 3 times of blade cascade pitch P of the turbine movable blade.
In one embodiment, the arrangement of the rectangular holes of the pre-rotation structure is staggered in two rows, that is, the rectangular holes are staggered and uniformly arranged: the ratio w/D of the axial distance between the two rows of rectangular holes to the width of the outlet of the rim sealing structure is =0.1-0.2; for each row of rectangular holes, the ratio delta/P =0.024-0.048 of the circumferential spacing between the holes to the turbine bucket cascade pitch.
In one embodiment, the size of the rectangular hole of the outlet of the pre-rotation structure is determined by the size of the leakage flow, when the leakage flow needs to be increased or decreased, the leakage flow swirl ratio of the outlet of the pre-rotation structure, that is, the outlet speed, is kept unchanged by proportionally increasing or decreasing the area of the rectangular holes, so that the effects of only changing the leakage flow and not changing the leakage flow swirl ratio are achieved, and a single variable is controlled.
In one embodiment, the ratio D/D =0.4-0.45 of the length of the rectangular hole of the pre-rotation structure in the axial direction to the width of the outlet of the rim sealing structure; the greater the length d in the axial direction, the smaller the axial spacing w between the individual holes: the sum of the two is equal to the width of a gap outlet of a cavity of the moving and static disks, namely 2d + w = D, and the ratio l/P of the length in the circumferential direction to the blade grid pitch of the turbine movable blades is =0.012-0.036; the larger the length l in the circumferential direction, the smaller the circumferential spacing Δ between the respective holes: the ratio of the sum of the two to the turbine bucket cascade pitch (l + delta)/P =0.06.
Compared with the prior art, the invention has the beneficial effects that:
(1) Compared with the traditional test structure, the gas collecting cavity is additionally arranged between the gap of the dynamic and static disc cavities and the leakage flow inlet, so that the influence of the arrangement position of the inlet on the outflow of leakage flow gas is weakened, and the leakage flow is more uniform in the circumferential direction when flowing out from the gap of the dynamic and static disc cavities;
(2) The clearance between the moving and static disc cavities and the sealing structure of the wheel rim refer to the design of an actual turbine, and the test structure is closer to the actual turbine;
(3) The design that the pre-rotation structure inclines towards the suction surface of the movable blade in the circumferential direction can simulate the pre-rotation generated by the rotation of the movable blade wheel in the cavity of the movable and static disks, and meanwhile, the simulated rotational flow ratio value can be changed by adjusting the inclination angle and the size of the rectangular hole at the outlet of the pre-rotation structure, so that the influence of the rotational flow ratio on the test result is researched;
(4) The outlet of the prerotation structure is designed into two rows of rectangular holes which are arranged in a staggered mode, so that leakage flow gas is more uniform in the circumferential direction when flowing out from the gap of the driven static disc cavity, and the outlet slot type design of the gap of the static disc cavity in the actual turbine is closer.
Drawings
FIG. 1 is a schematic diagram of a test structure for simulating turbine dynamic and static disc cavity leakage flow prerotation. In the figure, SS refers to a suction surface, and PS refers to a pressure surface.
FIG. 2 is a schematic view of the test structure of FIG. 1 mounted on a planar cascade test rig.
FIG. 3 is a cross-sectional bottom view of the leakage flow inlet, the gas collection chamber and the dynamic and static disk chamber gap.
Fig. 4 is a cross-sectional view of the structure of fig. 1 in a rim seal configuration.
Fig. 5 is a cross-sectional view of the structure of fig. 1 at a pre-spun configuration.
Fig. 6 is a front view of the pre-swirl structure.
Fig. 7 is a velocity vector triangle diagram after leakage flow exits from the pre-swirl structure.
FIG. 8 is a top view of the pre-swirl structure above the end wall of the outlet driven vane.
Fig. 9 is a partially enlarged view of the outlet of the pre-swirl structure.
The device comprises a turbine movable blade 1, a turbine movable blade 2, a movable blade end wall 3, an air inlet 4, an air collecting cavity 5, a movable and static disc cavity gap 6, a wheel rim sealing structure 7 and a pre-rotation structure 7.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples. The embodiment is only a specific implementation manner according to the above technical solution, and is not intended to limit the implementation scope of the present invention, and other equivalent changes based on the technical principle of the present invention belong to the protection scope of the present invention.
As shown in figures 1, 2, 3 and 4, the invention provides a test structure for simulating turbine moving and static disk cavity leakage flow prerotation, which comprises a gas collection cavity 4, wherein the gas collection cavity 4 is provided with a plurality of gas inlets 3, the gas collection cavity 4 is communicated with a moving and static disk cavity gap 5, the moving and static disk cavity gap 5 is communicated with a rim seal structure 6, the rim seal structure 6 is positioned below a plane cascade test bed, and the top surface of the rim seal structure is provided with a prerotation structure 7. The turbine movable vane 1 is arranged on the plane cascade test bed, the pre-rotation structure 7 is positioned at the upstream of the turbine movable vane 1, wherein the movable vane end wall 2 of the turbine movable vane 1 is one side close to the pre-rotation structure 7, leakage flow firstly enters the gas collecting cavity 4 from the gas inlet 3 and then enters the dynamic and static disc cavity gap 5, and then flows through the rim sealing structure 6 and the pre-rotation structure 7 and enters a cascade channel of the plane cascade test bed.
In the invention, the turbine movable vane 1 is a straight vane, and the vane profile is as follows: the proportion of 1 is selected from the molded lines of 10 percent of blade height sections of a certain actual turbine movable blade, and the molded lines are stretched in the vertical direction, and other molded lines of blade height sections can be selected according to requirements. Axial chord length C of turbine rotor blade 1 ax Namely, the axial chord length of the section of the actual turbine rotor blade at 10% of the blade height is obtained, and the cascade pitch P of the turbine rotor blade 1 is taken as the cascade pitch of the section of the actual turbine rotor blade at 10% of the blade height.
The air inlet 3 is a plurality of hollow cylindrical holes which are arranged at equal intervals in the circumferential direction, and the quantity and the recommended values of the inner diameter and the outer diameter of the hollow cylindrical holes are as follows: 1 blade cascade pitch P is arranged on the length of each blade cascade pitch P, and the ratio phi of the outer diameter of the cylindrical hole to the blade cascade pitch 1 P =0.12-0.16, ratio of inner diameter to cascade pitch phi 2 and/P =0.06-0.08. A collector is additionally arranged between the air inlet 3 and the clearance 5 between the dynamic disc cavity and the static disc cavityAnd the air cavity 4 weakens the influence of the arrangement position of the air inlet on the outflow of the leakage flow gas, so that the leakage flow is more uniform in the circumferential direction when flowing out from the gap of the driven static disc cavity.
The dynamic and static disc cavity gap 5 and the rim sealing structure 6 refer to the design of dynamic and static disc cavities and rim sealing in the actual turbine. The dynamic and static disc cavity gap 5 is a gap between the static impeller disc and the movable impeller disc, and a cuboid cavity structure is adopted in the test structure of the embodiment; the rim sealing structure 6 is used for sealing a disk cavity in an actual turbine, a tooth-shaped structure is adopted in the test structure of the embodiment, and the top surface (outlet) of the rim sealing structure 6 is the bottom surface (inlet) of the prerotation structure 7. The outlet width D of the rim sealing structure 6 depends on the design of a given moving and static disc cavity and a rim seal in an actual turbine, and the recommended value is 0.06C ax -0.12C ax 。
As shown in fig. 5, 6, and 7, the pre-rotation structure 7 is several tens of identical rectangular holes having an inclination angle θ in the circumferential direction, and is used for introducing a leakage flow in the moving and static disc cavity gap 5 into a cascade channel of the planar cascade test bed and generating a velocity component in the circumferential direction; seen from the movable blade end wall 2, the outlets of the pre-rotation structures 7 are two rows of rectangular holes arranged in a staggered manner, which are the same in number, and are distributed at the upstream position of the turbine movable blade 1. The oblique direction of the rectangular hole points to the suction surface side of the turbine bucket 1. The reason is as follows: in the working process of an actual turbine, the rotation of the movable impeller disc can drive the leakage flow outflowing from the dynamic and static disc cavities to generate circumferential deflection, but the circumferential velocity component v of the leakage flow leakage flow,u Is smaller than the movable impeller disc u blade The magnitude of the rotational linear velocity of (2). Thus, the leakage flow is relative to the velocity vector v of the turbine bucket 1 relative,u ＝v leakage flow,u -u blade The component direction in the circumferential direction is opposite to the rotation direction of the moving blade wheel, i.e., the leakage flow is biased toward the suction surface side of the turbine moving blade 1. Similarly, in order to simulate the swirling state, in a static plane blade cascade test bench, the velocity component to be generated by the pre-swirl structure 7 is v relative,u Therefore, the turbine blade 1 should be inclined toward the suction surface side. The range of the inclination angle theta can be selected from 0-90 degrees, and the size of the inclination angle theta depends on the leakage flow vortex to be simulatedThe flow ratio and the swirl ratio are defined as follows:
Figure BDA0003465627970000061
wherein v is leakage flow Is the absolute velocity of the leakage flow u blade Is the speed of the impeller disc, v relative The subscript u represents the circumferential component of the leakage flow relative to the velocity of the moving impeller disc, i.e. the leakage flow velocity at the outlet of the pre-swirl structure 7.
Therefore, when the leakage flow velocity at the outlet of the prerotation structure 7 is the same, the larger the inclination angle θ of the prerotation structure 7 is, the larger the velocity circumferential component is, and the lower the simulated leakage flow swirl ratio SR is.
As shown in fig. 8 and 9, the axial projection distance L of the pre-rotation structure 7 with respect to the turbine rotor blade 1 LE The recommended value is 0.3C depending on the design of the turbine stage ax -0.5C ax . Axial width D of distribution of pre-rotation structure 7 swirl The same width D as the outlet of the rim seal 6, i.e. D swirl = D; distributed circumferential length L swirl Is 2 times or 3 times the cascade pitch P of the turbine bucket 1.
The rectangular holes of the pre-rotation structure 7 are staggered and uniformly arranged, that is, the rectangular holes are staggered and uniformly arranged: the ratio w/D of the axial distance w between the two rows of rectangular holes to the width D of the outlet of the rim sealing structure 6 is =0.1-0.2; for each row of rectangular holes, the ratio delta/P of the circumferential spacing delta between the holes to the cascade pitch of the turbine bucket 1 is =0.024-0.048. The size of the rectangular hole at the outlet of the prerotation structure 7 is determined by the size of the leakage flow. When the leakage flow needs to be increased or reduced, the leakage flow swirl ratio of the outlet of the pre-rotation structure 7, namely the outlet speed, is ensured to be unchanged by a method of increasing or reducing the areas of the rectangular holes in proportion, so that the effects of only changing the leakage flow and not changing the leakage flow swirl ratio are achieved, and a single variable is controlled. The ratio D/D =0.4-0.45 of the axial length D of the rectangular hole of the pre-rotation structure 7 to the outlet width of the rim sealing structure 6, the larger the axial length D is, the smaller the axial distance w between the holes is, and the sum of the two times of the axial distance w between D and each hole is equal to the outlet width of the movable and static disc cavity gap 5, namely 2d + w =D. The ratio l/P of the length l in the circumferential direction to the cascade pitch of the turbine rotor blade 1 is =0.012-0.036, the larger the length l in the circumferential direction is, the smaller the circumferential distance delta between the holes is: the ratio (l + delta)/P =0.06 of the sum of circumferential intervals delta between the holes and the pitch of the cascade of the turbine rotor blades 1.
In the test process, leakage flow firstly converges into the gas collecting cavity through the gas inlet, then enters the gap between the dynamic and static disc cavities, then passes through the wheel edge sealing structure, and then flows out in an inclined mode under the action of the prerotation structure to generate circumferential speed components, so that prerotation generated by circumferential deflection of the leakage flow flowing out of the dynamic and static disc cavities driven by the rotation of the dynamic and static disc disks in an actual turbine can be simulated in a plane blade grid test. According to the invention, the gas collection cavity is additionally arranged between the gap between the dynamic and static disc cavities and the leakage flow gas inlet, so that the influence of the arrangement position of the gas inlet on the outflow of leakage flow gas is weakened, and the leakage flow is more uniform in the circumferential direction when flowing out from the gap between the dynamic and static disc cavities; the dynamic and static disc cavity gap and the wheel flange sealing structure refer to the design of an actual turbine, and the test structure is closer to the actual turbine; the problem that a static plane cascade test bed cannot simulate the prerotation phenomenon of the leakage flow at the upstream of a movable impeller disc is solved, and meanwhile, different turbine rotational flow ratio working conditions can be simulated by adjusting the inclination angle and the outlet area of a rectangular hole of a prerotation structure, so that the influence of the rotational flow ratio of the leakage flow of a cavity of a movable disc and a static disc on a cascade test result is researched; the outlet of the prerotation structure is designed into two rows of rectangular holes which are arranged in a staggered mode, so that leakage flow gas is more uniform in the circumferential direction when flowing out from the gap of the driven static disc cavity, and the outlet slot type design of the gap of the static disc cavity in the actual turbine is closer.
In conclusion, the invention provides a test structure for simulating the prerotation of the leakage flow of the moving and static disk cavities of the turbine, which can enable the leakage flow of the moving and static disk cavities of the moving and static disks to generate a velocity component in the circumferential direction and can simulate different rotational flow ratios by adjusting the prerotation structure. Meanwhile, the invention also weakens the influence of the arrangement position of the air inlet on the leakage flow, so that the leakage flow is more uniform in the circumferential direction.

Claims (10)

1. The utility model provides a test structure that simulation turbine sound dish chamber leakage flow prerevolves, its characterized in that, including gas collecting chamber (4) that have a plurality of air inlets (3), gas collecting chamber (4) and sound dish chamber clearance (5) intercommunication, sound dish chamber clearance (5) and rim seal structure (6) intercommunication, rim seal structure (6) are located plane cascade test bench below, and its top surface sets up prerotation structure (7), and turbine movable vane (1) set up on plane cascade test bench, and prerotation structure (7) are located turbine movable vane (1) upper reaches, and leakage flow gets into gas collecting chamber (4) from air inlet (3) earlier, gets into sound dish chamber clearance (5) again, then flows through rim seal structure (6) and prerotation structure (7), gets into in the cascade passageway of plane cascade test bench.
2. The test structure for simulating the pre-rotation of the leakage flow of the moving and static disc cavities of the turbine as claimed in claim 1, wherein the moving and static disc cavity gap (5) and the flange sealing structure (6) refer to the flange sealing structure of the moving and static disc cavities in the actual turbine, the moving and static disc cavity gap (5) is a gap between the moving and static wheel discs, and a cuboid cavity structure is adopted; the rim sealing structure (6) is used for sealing a disc cavity in an actual turbine and adopts a tooth-shaped structure, and the top surface, namely the outlet, of the rim sealing structure (6) is the bottom surface, namely the inlet, of the prerotation structure (7).
3. The test structure for simulating the pre-rotation of the leakage flow of the dynamic and static disk cavities of the turbine as claimed in claim 1, wherein the pre-rotation structure (7) is tens of identical rectangular holes with an inclination angle theta in the circumferential direction, is used for introducing the leakage flow in the dynamic and static disk cavity gap (5) into a blade cascade channel of a planar blade cascade test bed, and generates a velocity component in the circumferential direction; seen from the movable blade end wall (2), outlets of the pre-rotation structures (7) are two rows of rectangular holes which are arranged in a staggered mode and are the same in number, and the rectangular holes are distributed at the upstream position of the turbine movable blade (1).
4. The test structure for simulating the turbine dynamic and static disk cavity leakage flow prerotation according to claim 3, characterized in that the prerotation structure (7) is inclined and directed to the suction surface side of the turbine bucket (1).
5. The test structure for simulating the pre-rotation of the leakage flow of the dynamic and static disk cavity of the turbine as claimed in claim 3 or 4, wherein the inclination angle θ of the rectangular hole is selected from 0-90 °, and the size of the inclination angle θ depends on the size of the swirl ratio of the leakage flow to be simulated, and the swirl ratio is defined as follows:
Figure FDA0003784396380000021
wherein v is leakage flow Is the absolute velocity of the leakage flow u blade Is the speed of the impeller disc, v relative The subscript u represents the circumferential component of the leakage flow relative to the velocity of the moving impeller disc, i.e. the leakage flow velocity at the outlet of the pre-swirl structure (7); therefore, when the leakage flow speed at the outlet of the pre-rotation structure (7) is the same, the larger the inclination angle theta of the pre-rotation structure (7), the larger the magnitude of the circumferential speed component, and the lower the simulated leakage flow swirl ratio SR.
6. The test structure for simulating the pre-rotation of the leakage flow of the moving and static disk cavities of the turbine as claimed in claim 1, wherein the movable turbine blade (1) is a straight blade, the blade profile of the straight blade is selected from the profile of the cross section at a certain blade height of the actual movable turbine blade and is obtained by stretching the straight blade in the vertical direction, and the axial chord length C of the movable turbine blade (1) ax Namely the axial chord length of the section of the actual turbine movable blade at the blade height, and the cascade pitch P of the turbine movable blade (1) is taken as the cascade pitch of the section of the actual turbine movable blade at the blade height.
7. The test structure for simulating the turbine dynamic and static disk cavity leakage flow prerotation of claim 4, wherein the air inlets (3) are a plurality of hollow cylindrical holes which are equidistantly arranged in the circumferential direction, 1 hole is arranged on the length of each blade cascade pitch P, and the ratio phi between the outer diameter of each blade cascade pitch and the blade cascade pitch is phi 1 P =0.12-0.16, inner diameter and cascade pitchA ratio of phi 2 P =0.06-0.08; the outlet width D of the rim sealing structure (6) is 0.06C ax -0.12C ax (ii) a The axial projection distance L of the pre-rotation structure (7) relative to the turbine movable blade (1) LE Value of 0.3C ax -0.5C ax The axial width D of the distribution of the pre-rotation structure (7) swirl The width D of the outlet of the rim sealing structure (6) is the same, namely D swirl = D, circumferential length L of distribution swirl A cascade pitch P of the turbine rotor blade (1) of 2 or 3 times, wherein C ax Is the axial chord length of the turbine bucket (1).
8. The test structure for simulating turbine dynamic and static disc cavity leakage flow prerotation of claim 7, wherein the arrangement of the rectangular holes of the prerotation structure (7) is in a staggered arrangement of two rows, that is, the rectangular holes are staggered and uniformly arranged: the ratio w/D =0.1-0.2 of the axial distance between the two rows of rectangular holes to the width of the outlet of the rim sealing structure (6); for each row of rectangular holes, the ratio delta/P of the circumferential spacing between the holes to the cascade pitch of the turbine bucket (1) is =0.024-0.048.
9. The test structure for simulating the pre-rotation of the leakage flow of the dynamic and static disk cavity of the turbine as claimed in claim 1, wherein the size of the rectangular hole at the outlet of the pre-rotation structure (7) is determined by the size of the leakage flow, and when the leakage flow needs to be increased or decreased, the leakage flow rotational flow ratio (outlet speed) at the outlet of the pre-rotation structure (7) can be ensured to be unchanged by proportionally increasing or decreasing the area of the rectangular holes, so as to achieve the effects of only changing the leakage flow and not changing the leakage flow rotational flow ratio, thereby controlling a single variable.
10. The test structure for simulating the leakage flow prerotation of the dynamic and static disk cavity of the turbine as claimed in claim 9, wherein the ratio D/D =0.4-0.45 of the length of the rectangular hole of the prerotation structure (7) in the axial direction to the outlet width of the rim sealing structure (6); the greater the length d in the axial direction, the smaller the axial spacing w between the individual holes: the sum of the two is equal to the outlet width of the dynamic and static disc cavity gap (5), namely 2d + w = D, and the ratio l/P of the length in the circumferential direction to the blade grid pitch of the turbine movable blade (1) is =0.012-0.036; the greater the length l in the circumferential direction, the smaller the circumferential spacing Δ between the individual holes: the ratio (l + delta)/P =0.06 of the sum of the two and the pitch of the cascade of the turbine rotor blades (1).
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