Measurement Method and Application of Flow Coefficient of Single-Exhaust Film Cooling Hole on Turbine Blade Profile

Abstract

A method for measuring the flow coefficient of a single-flow film cooling orifice on a turbine blade profile and its application are disclosed. The method comprises a gas storage tank, a main flow valve, a main flow thermal flow meter, a rectifying section, a main flow section rectifying wind tunnel, and a cooling tower, connected in sequence. One end of the secondary flow valve is connected to the output end of the gas storage tank, and the other end is connected in sequence to a secondary flow thermal flow meter, a secondary flow pressure stabilizing tank, and a turbine blade profile single-flow film cooling orifice flow coefficient measuring test piece. The turbine blade profile single-flow film cooling orifice flow coefficient measuring test piece is installed in the main flow section rectifying wind tunnel. This invention's measurement method is designed for a single-flow film cooling orifice structure on a turbine blade profile. It allows adjustment of relevant parameters of the film cooling orifice structure to obtain the influence of changes in the film cooling orifice structure on the flow coefficient, ultimately yielding a precise film cooling orifice flow coefficient.

Description

Technical Field

[0001] This invention relates to the field of aero-engine turbine blade cooling technology, specifically to a method for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile and its application. Background Technology

[0002] Since the 1960s, cooling technology has been used on aero-engine turbine blades. Initially, turbine blade cooling methods simply involved machining several cylindrical holes radially inside the blade and passing cooling gas through them. However, the continuous increase in turbine inlet temperature spurred the rapid development of turbine blade cooling technology. Film cooling is a highly efficient and reliable cooling method, and it is now widely used in the cooling design of modern aero-engine turbine blades. When cooling air flows through the orifice wall of the film cooling film, due to inlet losses, friction losses, and outlet losses, the actual flow rate through the film cooling film is smaller than the theoretical flow rate under the same flow conditions. This leads to the definition of the flow coefficient:

[0003] C d =G re / G th

[0004] Among them, C d G is the flow coefficient. th For theoretical flow rate, G re This represents the actual traffic volume.

[0005] Since many factors influence actual flow rate, the actual flow rate is determined experimentally, while the theoretical flow rate is calculated under the assumption of isentropic expansion from the inlet secondary flow total pressure to the outlet mainstream static pressure. The formula for calculating the actual flow rate is as follows:

[0006]

[0007] Where A is the air film pore flow area; T * The total temperature of the inlet secondary flow; P1 * The total pressure of the inlet secondary flow; C d P2 is the flow coefficient; P2 is the outlet mainstream static pressure; k is the specific heat ratio: 1.4.

[0008] The flow coefficient is defined as the ratio of the actual flow rate through the film cooling orifice to the theoretical flow rate, and its value reflects the magnitude of the flow loss generated when the airflow passes through the orifice. In film cooling design, only by accurately determining the film cooling orifice flow coefficient can the cooling airflow be precisely controlled to achieve the expected cooling effect. Therefore, accurately obtaining the flow coefficient of the turbine blade film cooling orifice under experimental conditions is of great significance for exploring the heat transfer mechanism of the turbine blade film cooling structure, thereby guiding the solution of heat transfer engineering problems in high-temperature turbine components of engines, and improving the life of engine turbine blades.

[0009] Existing technologies, such as Chinese patent application number CN201710464122x and publication number CN107194118 A, disclose an aerodynamic-thermal co-optimization method for a turbine blade fan-shaped orifice film cooling structure. Based on a radial basis function neural network, it establishes a proxy model of the aerodynamic-thermal features of the turbine blade fan-shaped orifice film cooling structure and introduces a particle swarm optimization algorithm to achieve aerodynamic-thermal co-optimization of the turbine blade fan-shaped orifice film cooling structure. This invention overcomes the limitation of traditional film cooling structure optimization methods that rely on a large number of samples, possessing nonlinear prediction capabilities, high prediction accuracy, strong memory capacity and robustness, and good global approximation ability. However, this prior art is computationally complex and cannot accurately measure the flow coefficient of a single exhaust film cooling orifice on the turbine blade profile.

[0010] For example, existing technology, Chinese patent application number: CN2007101219834, publication number: CN101393071 A discloses a method and device for visual observation and transient measurement of turbine blade cooling process. The method involves heating the mainstream air to a predetermined temperature, introducing a cold airflow, which first enters the cooling channel inside the turbine blade to cool the blade, and then flows out to form a cold air film on the surface of the turbine blade. The temperature and pressure at each measuring point are recorded, and the mixing and flow of the mainstream airflow and the cold airflow near the turbine blade are observed. The apparatus for implementing the above method includes: a wind tunnel, one end of which is connected to a hot air source, and the other end of which is an exhaust port; a turbine blade is placed inside the wind tunnel according to its operating state; a cold air source is connected to the jet pipe of the turbine blade in the wind tunnel through a duct, and a pigment addition device is provided on the duct; an infrared detection window is opened on each side of the wind tunnel at the turbine blade, and an infrared thermal imager is provided at each infrared detection window; a visual observation window is opened on each side of the wind tunnel at the turbine blade, and a microscopic magnification photography device is provided at each visual observation window. However, this apparatus is for observing and measuring the turbine blade cooling process, and is not applied to the measurement of the flow coefficient of a single exhaust film cooling hole on a turbine blade profile. Furthermore, those skilled in the art cannot derive any technical inspiration from this disclosure to apply it to the measurement of the flow coefficient of a single exhaust film cooling hole on a turbine blade profile. Summary of the Invention

[0011] (1) Purpose of the invention

[0012] To address the issue of inaccurate cooling airflow prediction in existing turbine blade fluid dynamics calculation software, which leads to imprecise cooling airflow control, this invention proposes a test specimen, test system, and method for measuring the flow coefficient of a single-stage film cooling hole on a turbine blade profile. Using the method proposed in this invention, accurate measurement of the flow coefficient of a single-stage film cooling hole on a turbine blade profile can be achieved. Furthermore, the influence of different film cooling hole structures and operating conditions on the flow coefficient can be obtained, thereby correcting the blade fluid dynamics calculation software and improving the accuracy of blade cooling design.

[0013] (2) The solution of the present invention to achieve the above objectives

[0014] The construction and test scheme design of the turbine blade profile single exhaust film cooling hole flow coefficient measurement system are as follows: Based on the requirements of turbine blade profile single exhaust film cooling hole flow coefficient measurement, a suitable test system including mainstream and secondary flow is selected, the modules of the test system are reasonably arranged, and suitable mainstream flow path, secondary flow path and flow boundary environment of turbine blade profile single exhaust film cooling hole flow coefficient measurement test piece are arranged. The test piece, system and method technical scheme are as follows;

[0015] A test system for measuring the flow coefficient of a single exhaust film cooling hole in a turbine blade profile is characterized by comprising, in sequence, an air storage tank 1, a main flow valve 2, a main flow thermal flow meter 3, a rectifier section 4, a main flow section rectifier wind tunnel 5, and a cooling tower 6; one end of the secondary flow valve 7 is connected to the output end of the air storage tank 1, and the other end is connected in sequence to a secondary flow thermal flow meter 8, a secondary flow pressure stabilizing tank 9, and a turbine blade profile single exhaust film cooling hole flow coefficient measuring test piece 10; the turbine blade profile single exhaust film cooling hole flow coefficient measuring test piece 10 is set in the main flow section rectifier wind tunnel 5.

[0016] The structural design of the turbine blade profile single-outlet film flow coefficient measurement test piece 10 involves designing and fabricating a turbine blade profile single-outlet film flow coefficient measurement test piece while ensuring consistent pressure parameters and similar geometric structure. The test piece selects characteristic parameters similar to those of a real turbine blade, such as film outflow angle, film orifice diameter, aspect ratio, dimensionless cooling channel height, total film orifice thickness, and number of film orifices, to ensure the applicability of the test results. The specific structure of this test piece is as follows:

[0017] A test specimen for measuring the flow coefficient of a single exhaust film orifice on a turbine blade profile. The test specimen adopts a double-layer orifice plate combination structure including main and secondary flow side plates. The main flow side is made of plexiglass plate 13, and the secondary flow side is made of aluminum alloy plate 12. The two plates are fastened together with screws. A single exhaust film orifice is machined at the same position in the middle of the plexiglass plate and the middle of the aluminum alloy plate to ensure that the total thickness t14 of the film orifice is consistent with that of the real turbine blade.

[0018] The present invention also discloses a method for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile.

[0019] This invention also discloses a flow system that uses the flow coefficient measurement method of a single exhaust film cooling hole on a turbine blade profile to be applied to the design of aero-engine turbine blades.

[0020] (3) Beneficial effects

[0021] The method for measuring the flow coefficient of a single-row film cooling hole on a turbine blade profile proposed in this invention achieves relatively accurate measurement of the flow coefficient based on consistent pressure parameters and similar geometric structures. The beneficial effects of this invention are: the proposed measurement method is primarily designed for the single-row film cooling hole structure of turbine blade profiles, obtaining a precise film cooling hole flow coefficient; the proposed method, primarily designed for the single-row film cooling hole structure of turbine blade profiles, allows adjustment of relevant parameters of the film cooling hole structure to obtain the influence of changes in the film cooling hole structure on the flow coefficient; the proposed method, primarily designed for the single-row film cooling hole structure of turbine blade profiles, allows adjustment of test condition parameters such as pressure and temperature to obtain the influence of film cooling hole condition parameters on the flow coefficient; and the measurement results obtained by this invention can be used to correct blade fluid calculation software, improving calculation accuracy. Attached Figure Description

[0022] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the experimental system for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, as proposed in this invention.

[0024] Figure 2 This is a schematic diagram of the turbine blade profile single exhaust film cooling hole flow coefficient measurement test piece proposed in this invention.

[0025] Figure 3 This is a schematic diagram of the parameters of the test piece for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, as proposed in this invention.

[0026] Figure 4 This is a schematic diagram of the gas film cooling hole parameters for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, as proposed in this invention.

[0027] Figure 5 This is a schematic diagram of the measuring point location of the turbine blade profile single exhaust film cooling hole flow coefficient measurement test piece proposed in this invention.

[0028] Figure 6 This is a schematic diagram of the air film hole angle of the test piece for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, as proposed in this invention.

[0029] In the diagram: 1-Gas storage tank, 2-Main flow valve, 3-Main flow thermal flow meter, 4-Rectifying section, 5-Main flow section rectifying wind tunnel, 6-Cooling tower, 7-Secondary flow valve, 8-Secondary flow thermal flow meter, 9-Secondary flow pressure stabilizing tank, 10-Test piece for measuring the flow coefficient of a single exhaust film orifice on the turbine blade profile, 11-Film orifice, 12-Aluminum alloy plate, 13-Acrylic glass plate, 14-Total thickness t of film orifice, 15-Secondary flow, 16-Main flow, 17-Height of cooling channel h, 18-Length of test piece L, 19-Diameter of film orifice d, 20-Schematic diagram of the location of the inlet secondary flow total temperature and total pressure measuring point, 21-Schematic diagram of the location of the outlet main flow static pressure measuring point, 22-Inclination angle α of film orifice. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0031] This invention proposes a method for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, including experimental system design, test piece structure design, experimental testing, and flow coefficient calculation and analysis. The design of the above schemes will be described in detail below.

[0032] like Figure 1 As shown, the test system for measuring the flow coefficient of a single exhaust film cooling hole in a turbine blade profile is characterized by comprising, in sequence, an air storage tank 1, a main flow valve 2, a main flow thermal flow meter 3, a rectifier section 4, a main flow section rectifier wind tunnel 5, and a cooling tower 6; one end of the secondary flow valve 7 is connected to the output end of the air storage tank 1, and the other end is connected in sequence to a secondary flow thermal flow meter 8, a secondary flow pressure stabilizing tank 9, and a turbine blade profile single exhaust film cooling hole flow coefficient measuring test piece 10; the turbine blade profile single exhaust film cooling hole flow coefficient measuring test piece 10 is set in the main flow section rectifier wind tunnel 5.

[0033] During the test, the airflow is supplied by an air compressor and enters the air supply pipeline. A water separator removes moisture from the air to ensure the dryness of the airflow. The separated airflow is then split into a main stream and a secondary stream through the airflow pipeline. The main stream enters the main stream intake section through the main stream regulating valve 2, passes through a rectifier pipeline, and then flows through the rectifier wind tunnel to the turbine blade profile single-exhaust film orifice flow coefficient measuring test piece 10. The secondary stream, after its flow rate is controlled by the secondary stream regulating valve, enters the secondary stream intake section, passes through the airflow pipeline directly into the secondary stream pressure stabilizing tank, and after stabilization, flows through the airflow pipeline into the turbine blade profile single-exhaust film orifice flow coefficient measuring test piece 10, and exits through the film orifice on the test piece.

[0034] The present invention designs and manufactures a turbine blade profile single-exhaust film orifice flow coefficient measurement test piece under the condition of ensuring consistent pressure parameters and similar geometric structure. Each test piece has a single exhaust film orifice. The structural diagram of the test piece is shown below. Figure 2 As shown. The present invention relates to the structural design of the turbine blade profile single-outlet film flow coefficient measurement test piece 10. That is, under the condition of ensuring consistent pressure parameters and similar geometric structure, the turbine blade profile single-outlet film flow coefficient measurement test piece is designed and manufactured. The test piece selects the same characteristic parameters as the real turbine blade, such as film outflow angle, film hole diameter, length-to-diameter ratio, dimensionless cooling channel height, total film hole thickness, and number of film holes, to ensure the applicability of the test results.

[0035] The specific structure of the test piece is as follows: Figure 3 As shown. The turbine blade profile single-exhaust film orifice flow coefficient measurement test piece adopts a double-layer orifice plate combination structure including main and secondary flow side plates. The main flow side uses an acrylic plate 13, and the secondary flow side uses an aluminum alloy plate 12. The two plates are fastened together with screws. Using an acrylic plate on the main flow side can better measure the total secondary flow temperature T at the inlet of the film orifice under the thermal insulation effect. * In the secondary flow test, aluminum alloy plates were used to improve the strength of the test specimen. Single-layer gas film holes were simultaneously machined at the same positions in the middle of the plexiglass plate and the aluminum alloy plate to ensure that the total thickness t14 of the gas film holes was consistent with that of the actual turbine blade.

[0036] The aspect ratio L / d, dimensionless cooling channel height h / d, and number of film cooling holes are defined as follows: Figure 3 As shown. The diameter d of the film air pore and the definition of the film air pore parameters are as follows. Figure 4 As shown. The experimental specimen was selected with the same film flow angle α as the real turbine blade, such as... Figure 6 As shown.

[0037] According to the definition of flow coefficient, only the total secondary flow temperature T at the inlet of the film gas vent is needed during the experiment. * , inlet secondary flow total pressure By determining the main outlet static pressure P2 and combining it with the measured film gas flow area A, the theoretical flow rate G of the secondary flow can be calculated. th Then, based on the experimentally measured actual flow rate G of the secondary flow... re The flow coefficient C of the film pore can then be calculated. d The secondary flow total temperature and total pressure were measured using an integrated total temperature and total pressure probe located upstream of the inlet of the film gas vent on the secondary flow side of the test specimen. The main flow static pressure was measured at points arranged on the wall of the plexiglass plate on the main flow side. The locations of the measuring points are shown in the diagram below. Figure 5As shown in the diagram. Based on the total number of film membrane holes in the test specimen, multiple pressure and temperature measuring points are evenly arranged at the corresponding positions. The measured data are weighted and averaged to obtain the inlet secondary flow total temperature, inlet secondary flow total pressure, and outlet mainstream static pressure for a single exhaust film membrane hole in the test specimen. The actual secondary flow rate through the single exhaust film membrane hole of the test specimen is measured using a secondary flow thermal flow meter. By changing the test specimen with different film membrane hole structure parameters and adjusting the test conditions such as pressure and temperature, the flow coefficient value of a single exhaust film membrane hole under the influence of different parameters can be obtained.

[0038] A test method for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, including a test system for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, characterized by the following steps:

[0039] Step 1: Determine the relevant characteristic parameters of the air film pores of the test specimen being measured.

[0040] The test specimens were selected with the same characteristic parameters as real turbine blades, including film outflow angle, film hole diameter, length-to-diameter ratio, dimensionless cooling channel height, total film hole thickness, and number of film holes.

[0041] Step 2: Determine the double-layer perforated plate combination structure of the primary and secondary flow side plates of the test specimen.

[0042] A single air film hole is simultaneously machined in the middle of the plexiglass plate and the same position in the middle of the aluminum alloy plate to ensure that the total thickness of the air film hole is consistent with that of the actual turbine blade.

[0043] Step 3: Supply compressed gas to the main and secondary streams.

[0044] Step 4: Obtain the inlet secondary flow total temperature, inlet secondary flow total pressure, and outlet main flow static pressure of the film gas vent.

[0045] Step 5: Calculate the theoretical flow rate of the secondary flow.

[0046] Based on the measured flow area A of the air film orifice, the theoretical flow rate of the secondary flow is calculated.

[0047]

[0048] Step 6: Calculate the flow coefficient of the single exhaust film cooling hole on the turbine blade profile.

[0049] The flow coefficient of the film pores was calculated based on the actual flow rate of the secondary flow measured in the experiment.

[0050] C d =G re / G th

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A test system for measuring the flow coefficient of a single exhaust film cooling hole in a turbine blade profile, comprising a test piece for measuring the flow coefficient of a single exhaust film cooling hole in a turbine blade profile, characterized in that: The system includes, in sequence, a gas storage tank, a main flow valve, a main flow thermal flow meter, a rectifier section, a main flow rectifier wind tunnel, and a cooling tower; it also includes a secondary flow valve, a secondary flow thermal flow meter, and a secondary flow pressure stabilizing tank. One end of the secondary flow valve is connected to the output end of the gas storage tank, and the other end is connected in sequence to the secondary flow thermal flow meter, the secondary flow pressure stabilizing tank, and the measuring test piece. The turbine blade profile single-exhaust film orifice flow coefficient measuring test piece is set in the main flow rectifier wind tunnel. The test piece adopts a double-layer orifice plate combination structure including main and secondary flow side plates. The main flow side plate and the secondary flow side plate are fastened together with screws. The main flow side plate is made of plexiglass, and the secondary flow side plate is made of aluminum alloy. Single-exhaust film orifices are simultaneously machined at the same position in the middle of the plexiglass plate and the aluminum alloy plate to ensure that the total thickness t14 of the film orifice is consistent with that of the actual turbine blade. The test piece is a flat plate structure or a curved surface structure for a specific position of the turbine blade, and is set in the main flow rectifier wind tunnel.

2. A test method for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile, comprising the test system for measuring the flow coefficient of a single exhaust film cooling hole on a turbine blade profile as described in claim 1, characterized in that, Includes the following steps: Step 1: Determine the relevant characteristic parameters of the air film pores in the test specimen being measured; Step 2: Determine the double-layer perforated plate combination structure of the primary and secondary flow side plates of the test specimen; Step 3: Supply compressed gas to the main and secondary streams; Step 4: Obtain the inlet secondary flow total temperature, inlet secondary flow total pressure, and outlet main flow static pressure of the film gas vent. Step 5: Calculate the theoretical flow rate of the secondary flow; Step 6: Calculate the flow coefficient of a single exhaust film cooling hole on the turbine blade profile; Step 1 further includes the following: Selecting the same film cooling outflow angle, film cooling hole diameter, aspect ratio, dimensionless cooling channel height, total film cooling hole thickness, and number of film cooling holes as the actual turbine blade for the test specimen; Step 2 further includes the following: Simultaneously machining a single-row film cooling hole at the same position in the middle of the plexiglass plate and the aluminum alloy plate to ensure that the total thickness of the film cooling holes is consistent with that of the actual turbine blade; Step 5 further includes the following: Calculating the theoretical flow rate of the secondary flow based on the measured film cooling hole flow area A: Among them: the total secondary flow temperature T at the inlet of the film gas vent * , inlet secondary flow total pressure The outlet mainstream static pressure P2, combined with the measured gas film orifice flow area A and k as the specific heat ratio; step 6 further includes the following: based on the experimentally measured secondary flow rate, the flow coefficient of the gas film orifice is calculated: C d =G re / G th .

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