Device and method for measuring heat transfer coefficient in front edge spraying air film hole

Abstract

The invention discloses a device and a method for measuring a heat transfer coefficient in a front edge spraying air film hole, and belongs to the field of cooling of high-temperature parts of aero-engines. The device comprises a spraying module, an illumination imaging module, a temperature control module and a data processing module. The spraying module prepares the uniform thermochromic liquid crystal coating on the inner wall of the deep small aperture, the nozzle is driven by the pose adjusting mechanism to generate relative motion relative to the measured piece, and the motion at least comprises components in the axial direction of the pore channel and in the plane perpendicular to the axis of the pore channel, so that the whole inner wall of the pore channel is uniformly covered with the coating. The illumination imaging module collects in-hole coating developing images, the temperature control module provides and monitors thermal boundary conditions, and the data processing module processes the images and temperature data to calculate heat exchange coefficient distribution. The technical problem that uniform coating preparation, stable thermal environment control and in-hole effective imaging measurement are difficult to realize in a small-aperture deep hole is solved, and high-precision measurement of in-hole heat exchange coefficient distribution is realized.

Description

Technical Field

[0001] This invention belongs to the field of cooling technology for high-temperature components of aero-engines, specifically relating to a device and method for measuring the heat transfer coefficient distribution inside small-diameter leading-edge spray film orifices. Background Technology

[0002] Aero-engine turbine blades operate in extremely harsh environments, with their leading edges bearing the highest thermal loads. Film cooling (FSU) is a key technology for protecting the blade's leading edge. Its principle involves expelling low-temperature gas from the compressor through film cooling orifices created within the blade's internal cavities and along the leading edge, forming a protective film on the blade's outer surface to insulate against the high-temperature combustion gases. Research indicates that convective heat transfer within the film cooling orifices accounts for 50%-80% of the total cooling within the blade, making it a decisive factor affecting the overall cooling efficiency and temperature uniformity. Due to complex phenomena such as high-speed impacts, separation, and reattachment within the orifices, the local convective heat transfer coefficient distribution on the orifice wall is extremely uneven, forming local hot spots and inducing thermal stress concentration, severely impacting the blade's lifespan and reliability. Therefore, accurately obtaining the local heat transfer coefficient distribution across the entire surface of the film cooling orifice wall is of crucial engineering significance for optimizing film cooling orifice design, improving cooling efficiency, reducing cooling air consumption, and accurately predicting the blade's thermal fatigue life.

[0003] Thermochromic liquid crystal thermometry is widely used for measuring convective heat transfer coefficients due to its advantages such as non-contact operation, full-field measurement, and high spatial resolution. This technique involves coating the surface with a thermosensitive liquid crystal, whose color changes with temperature. Through calibration and image processing, the surface temperature field can be obtained, and the heat transfer coefficient can then be calculated using a heat transfer model. This technique is relatively mature in traditional planar or open-channel heat transfer studies.

[0004] However, applying thermochromic liquid crystal temperature measurement technology to the interior of small-aperture, high-aspect-ratio leading-edge spray film orifices presents a fundamental challenge: the small orifice diameter (typically on the millimeter scale) and deep channels make it difficult for conventional spraying methods to uniformly deliver and cover the entire inner wall of the orifice with liquid crystal atomized particles. This results in uneven coating thickness, the presence of dead zones, and the inability to form a consistent and reliable temperature measurement substrate. Current technologies lack effective methods for preparing uniform liquid crystal coatings within deep, small channels, which is the primary technical bottleneck hindering the acquisition of high-precision heat transfer coefficient distribution within the orifice. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem that existing thermochromic liquid crystal temperature measurement technology is difficult to achieve uniform coating preparation in small-diameter, deep-channel pores, resulting in the inability to accurately measure the heat transfer coefficient inside the pores. The invention proposes a measurement device and method that integrates a controllable spraying solution.

[0006] The applicant further recognized that even if the coating problem were solved, the measurement of the film gas vent inlet region would still have a fundamental error. The classical theory of thermochromic liquid crystal thermometry is based on the assumption of one-dimensional semi-infinite transient heat transfer. However, in the film gas vent inlet region, the flow experiences strong three-dimensional disturbances, and the wall exhibits significant lateral thermal conduction, causing the temperature response in this region to deviate from the classical theoretical model. Therefore, this invention introduces a specialized correction algorithm in the data processing.

[0007] By integrating a comprehensive solution to address the technical challenges of coating preparation and inlet error correction, this invention ultimately achieves high-precision and high-reliability measurement of the heat transfer coefficient distribution across the entire surface of the inner wall of a small-diameter air film pore.

[0008] To achieve the above objectives, the technical solution provided by this invention is:

[0009] On the one hand, a device for measuring the heat transfer coefficient inside the leading edge spray film orifice is provided, including a spraying module, an illumination imaging module, a temperature control module, and a data processing module;

[0010] The spraying module is used to coat the inner wall of the air film pore channel of the test piece with a uniform thermochromic liquid crystal coating, and includes a liquid crystal storage tank, a nozzle, a pressure controller, a posture adjustment mechanism, a horn-shaped flow guiding structure and an airflow driving structure.

[0011] Liquid crystal storage tanks are used to contain thermochromic liquid crystal solutions;

[0012] The nozzle inlet is connected to the liquid crystal storage tank via a fluid pipeline, which is used to atomize the liquid crystal solution and spray it onto the inner wall of the channel;

[0013] The pressure controller is installed on the fluid pipeline to regulate the pipeline pressure in order to control the liquid crystal ejection flow rate of the nozzle;

[0014] The flared mouth drainage structure is set at the inlet of the air film pore of the test piece to guide the atomized liquid crystal solution into the pore.

[0015] The airflow drive structure is located at the outlet of the air film hole of the test piece to provide auxiliary airflow to the channel;

[0016] The position adjustment mechanism is used to load the nozzle and can drive the nozzle to generate relative motion relative to the workpiece. The relative motion includes at least relative motion along the channel axis and relative motion in a plane perpendicular to the channel axis, so that the atomized liquid crystal solution ejected from the nozzle, guided by the flared mouth drainage structure and assisted by the airflow drive structure uniformly covers the entire inner wall of the channel.

[0017] The illumination imaging module and the temperature control module are located downstream of the spraying module, and are used to acquire color images of the liquid crystal coating and to provide, monitor and control thermal boundary conditions, respectively.

[0018] The data processing module is electrically connected to the illumination imaging module and the temperature control module, respectively, and is used to receive and process the color rendering image and the temperature data collected by the temperature control module in order to calculate the local heat transfer coefficient distribution of the inner wall of the air film pore of the test piece.

[0019] Furthermore, the illumination imaging module includes a ring-shaped LED light source and a camera. The ring-shaped LED light source is used to provide uniform illumination into the channel, and the camera is used to acquire liquid crystal color images of the inner wall of the channel.

[0020] Furthermore, the temperature control module includes a heater, a thermocouple, a temperature scanner, and a flow controller. The heater is used to heat the cooling fluid flowing through the orifice, the flow controller is used to regulate the flow rate of the cooling gas, and the thermocouple is used to monitor the temperature of the cooling gas and / or the inner wall of the orifice via the temperature scanner.

[0021] Furthermore, the data processing module includes an image processing unit and a heat transfer coefficient calculation unit. The image processing unit is used to obtain the temperature field of the inner wall of the channel based on the color image, and the heat transfer coefficient calculation unit is used to calculate the local heat transfer coefficient distribution based on the temperature field and temperature data, combined with the heat transfer model.

[0022] Furthermore, the heat transfer coefficient calculation unit is configured to correct the heat transfer coefficient calculation of the air film inlet region, and the parameters on which the correction is based include the time difference of transverse heat conduction effect obtained from the theoretical model.

[0023] On the other hand, a method for measuring the heat transfer coefficient inside the leading edge spray film orifice is provided, which is based on the aforementioned device for measuring the heat transfer coefficient inside the leading edge spray film orifice, and includes the following steps:

[0024] Step 1: Using a spraying module, a uniform thermochromic liquid crystal coating is applied to the inner wall of the air film pore channel of the test piece.

[0025] Step 2: Using the temperature control module, establish and control the thermal boundary conditions of the cooling gas flowing through the film cooling holes;

[0026] Step 3: Using the illumination imaging module, acquire color images of the liquid crystal coating under thermal boundary conditions;

[0027] Step 4: Using the data processing module, process the color image and the temperature data collected by the temperature control module to calculate the local heat transfer coefficient distribution of the inner wall of the air film pore.

[0028] Furthermore, step 1 specifically includes:

[0029] Step 1.1: Load the nozzle onto the pose adjustment mechanism;

[0030] Step 1.2: Adjust the inlet pressure of the nozzle using the pressure controller and start the nozzle to spray.

[0031] Step 1.3: The position adjustment mechanism drives the relative movement between the test piece and the nozzle, while the airflow drive structure set at the outlet of the air film hole provides auxiliary airflow, so that the atomized liquid crystal solution is evenly covered on the entire inner wall of the channel under the guidance of the funnel-shaped flow guide structure set at the inlet of the air film hole.

[0032] Furthermore, in step 4, when calculating the local heat transfer coefficient of the film gas inlet region, the following correction steps are performed:

[0033] Obtain the time difference of transverse thermal conduction influence in the inlet region of the air film vent, as determined by the theoretical model;

[0034] The actual color development response time obtained from the color development image is corrected by utilizing the time difference;

[0035] The corrected inlet region heat transfer coefficient is calculated based on the corrected time.

[0036] The advantages of this invention are:

[0037] 1. The leading-edge spray film orifice heat transfer coefficient measuring device provided by this invention, through a dedicated spraying module including a position adjustment mechanism, a flared nozzle guiding structure, and an airflow driving structure, achieves precise motion control of the nozzle relative to the test object. Combined with the synergistic effect of inlet guidance and outlet auxiliary airflow, it systematically solves for the first time the problem of unevenly coating a thermochromic liquid crystal coating on the inner wall of deep, small-diameter orifices, providing a reliable substrate for accurate temperature measurement within the orifice. Through an integrated illumination and imaging module and a temperature control module with monitoring and control functions, reliable image acquisition and thermal environment conditions are provided for the coating color development and heat transfer process. Finally, through the comprehensive processing of multi-source information by the data processing module, a complete distribution of the orifice heat transfer coefficient can be obtained. This device forms an integrated system specifically designed to solve the problems of orifice coating preparation and measurement.

[0038] 2. The method for measuring the heat transfer coefficient inside the leading-edge spray film pores provided by this invention forms a standardized and repeatable process for measuring the heat transfer coefficient inside the pores by sequentially connecting steps such as controllable spraying, establishment of thermal boundary conditions, image acquisition, and data processing. This method ensures controllability throughout the entire process from coating preparation to data output, and for the first time, it can obtain stable and reliable heat transfer coefficient distribution data in deep, small pores.

[0039] 3. This invention introduces a correction algorithm based on a transverse thermal conductivity model to calculate the heat transfer coefficient in the inlet region of the film gas vent. This effectively identifies and compensates for fundamental measurement errors caused by the complex flow and heat transfer characteristics in this region. This significantly improves the continuity and accuracy of the final inlet heat transfer coefficient distribution, especially in the significantly erroneous inlet region, providing a crucial guarantee for high-precision thermal analysis. Attached Figure Description

[0040] The above and / or other features and advantages of the present invention will become more readily understood from the following description with reference to the accompanying drawings, which are not drawn to scale and some features are enlarged or reduced to show details of specific parts.

[0041] Figure 1 This is a schematic diagram of the spraying module in the heat transfer coefficient measuring device inside the leading edge spray film hole according to an embodiment of the present invention;

[0042] Figure 2 This is a flowchart illustrating the steps of the method for measuring the heat transfer coefficient inside the leading edge spray film orifice according to an embodiment of the present invention.

[0043] Figure 3 This is a schematic diagram of the overall testing system according to an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the straight-hole type air film hole test specimen and spraying path in Example 1;

[0045] Figure 5 (a) and (b) in the example are comparisons of the Nusselt number (Nu) distribution cloud maps of the inner wall of the vertical air film pore, obtained through numerical simulation and experimental measurement, respectively.

[0046] Figure 6 In Example 1, (a), (b), and (c) are comparison curves of the spanwise average Nu number obtained from experiments and numerical simulations at three different Reynolds numbers (Re).

[0047] Figure 7 For Example 1, a bar chart comparing the surface-average Nu number obtained from experiments and numerical simulations under three different Re values;

[0048] Figure 8 This is a schematic diagram of the shrinkage outlet type film film orifice test specimen and spraying path in Example 2;

[0049] Figure 9 (a) and (b) in the figure are comparisons of Nu distribution cloud maps of the inner wall of the shrinkage outlet type air film orifice in Example 2, based on numerical simulation and experimental measurement.

[0050] Figure 10 (a), (b), and (c) in Example 2 are comparison curves of the average Nu number along the borehole along the span obtained by experiments and numerical simulations under three different Re values.

[0051] Figure 11 This is a bar chart comparing the surface-average Nu number obtained from experiments and numerical simulations under three different Re values ​​for Example 2.

[0052] Figure 12This is a schematic diagram of the shrinkage inlet type film film orifice test specimen and spraying path in Example 3;

[0053] Figure 13 (a) and (b) in the figure are comparisons of Nu distribution cloud maps of the inner wall of the contraction inlet type air film vent in Example 3, based on numerical simulation and experimental measurement.

[0054] Figure 14 (a), (b), and (c) in Example 3 are comparison curves of the average Nu number along the borehole along the span obtained by experiments and numerical simulations under three different Re values.

[0055] Figure 15 The bar chart shows the comparison of the surface-average Nu number obtained from experiments and numerical simulations under three different Re values ​​for Example 3.

[0056] In the diagram: 1- Nozzle; 2- Liquid crystal storage tank; 3- Pressure controller; 4- Position adjustment mechanism; 5- Horn-shaped flow guide structure; 6- Airflow drive structure; 7- Incoming air inlet chamber; 8- Outgoing air extraction chamber; 9- Cavity; 10- Air film hole test piece; 11- Lighting device. Detailed Implementation

[0057] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments thereof. It should be noted that the following detailed description of the present invention is for illustrative purposes only and is not intended to limit the scope of the invention.

[0058] The present invention provides a device for measuring the heat transfer coefficient inside leading-edge spray film cooling orifices, and a method for measuring the heat transfer coefficient inside leading-edge spray film cooling orifices based on the device. This method and device are specifically designed for small-diameter, deep-channel, and potentially angled or constricted / expanded complex orifice shapes. They solve a series of problems encountered by traditional thermochromic liquid crystal temperature measurement technology in achieving uniform coating preparation, stable thermal environment control, and fundamental error correction in the inlet region within the orifice. This provides crucial experimental data for the optimized design and life assessment of film cooling structures.

[0059] As an exemplary embodiment of the present invention, the core components of the device for measuring the heat transfer coefficient inside the leading edge spray film orifice are as follows: Figure 1 and Figure 3 As shown, it mainly includes a spraying module, an illumination and imaging module, a temperature control module, and a data processing module. These modules work together to systematically solve the aforementioned technical challenges.

[0060] Reference Figure 1The spraying module is crucial for uniformly coating the inner wall of the film cooling pores of the test piece. It includes a nozzle 1, a liquid crystal reservoir 2, a pressure controller 3, a position adjustment mechanism 4, a flared nozzle drainage structure 5, and an airflow drive structure 6. It should be understood that the term "test piece" in this document refers to any object whose heat transfer coefficient within its film cooling pores needs to be measured. This can be a real aero-engine turbine blade or a test piece specifically designed and manufactured to simulate the specific film cooling pore characteristics of a blade. In this embodiment, a test piece is used. The test piece is a standardized test model manufactured for research purposes. Its core consists of one or more film cooling pores with specific geometric parameters (such as aperture, inclination angle, and aspect ratio) used to reproduce the flow and heat transfer phenomena of real blade pores under controlled experimental conditions.

[0061] The liquid crystal reservoir 2 is used to hold the pre-prepared thermosensitive liquid crystal solution. The inlet of the nozzle 1 is connected to the reservoir via a fluid pipeline, which is used to atomize the liquid crystal solution and spray it onto the inner wall of the channel. The pressure controller 3 is usually a precision air pressure regulating valve, connected in series in the pipeline, which controls the liquid crystal ejection flow rate of the nozzle 1 by precisely adjusting the supply air pressure. This is the basis for achieving controllable coating thickness.

[0062] The orientation adjustment mechanism 4 is used to mount the nozzle 1. This mechanism has multi-degree-of-freedom motion capability, enabling it to drive the nozzle to generate relative motion with respect to the test piece. This relative motion includes at least relative motion along the axial direction of the channel and relative motion in a plane perpendicular to the channel axis. During spraying, the nozzle 1 and the film-forming test piece 10 are made to generate precise relative motion in the manner described above. This composite motion ensures that the atomized liquid crystal particles can reach and cover every area of ​​the channel's inner wall from different directions, thereby forming a coating of uniform thickness, laying an irreplaceable physical foundation for subsequent accurate temperature measurement.

[0063] In this embodiment, the pose adjustment mechanism 4 is mainly composed of a linear motion module and a two-axis rotating gimbal.

[0064] The linear motion module is the core component for achieving "relative motion along the axial direction of the channel". This module typically uses a high-precision ball screw slide or linear motor module, and its motion axis is set to be approximately parallel to the axis of the air film orifice to be measured. Driven by a stepper motor or servo motor, this module can drive the load on it to perform precise reciprocating linear motion along this axis.

[0065] The two-axis rotary gimbal is a key component for achieving relative motion within a plane perpendicular to the orifice axis. It typically consists of two precision rotary tables orthogonally connected in series (e.g., a U-shaped frame structure) or integrated into a compact two-dimensional gimbal. Rotation of the first axis (A-axis) changes the direction of nozzle 1's spray in the plane perpendicular to the orifice axis (i.e., changes the circumferential angle); rotation of the second axis (B-axis) fine-tunes the nozzle's pitch angle to optimize the incident angle of the atomizing cone. The combined motion of these two axes allows the spray axis of nozzle 1 to point in any direction within this vertical plane. When this rotary gimbal is mounted on the slider of the aforementioned linear motion module, the spray point of nozzle 1 can be aligned with any target area on the inner wall of the orifice within the motion space defined by "axial linear motion" and "in-plane rotation."

[0066] In actual spraying operations, the linear motion module and the two-axis rotary gimbal are usually coordinated and controlled by a CNC system. The system plans a motion trajectory based on the geometric parameters of the film film orifice (such as depth and tilt angle): the linear module is responsible for driving the nozzle to move along the axial direction of the orifice (corresponding to the depth direction of the orifice), while the rotary gimbal rotates at each axial position through the cooperation of the two axes, so that the spray center line of the nozzle is aligned with the corresponding direction of each circumferential area of ​​the inner wall of the orifice to be covered within the inlet section of the film film orifice. This achieves angular matching of each wall area within the orifice, allowing the atomized coating to enter the orifice in a preset direction, thereby achieving comprehensive coverage of the inlet section, middle section, and deep area.

[0067] It should be understood that the structure of the pose adjustment mechanism 4 is merely an example and is not intended to limit the invention; it can be implemented using any known and mature technology.

[0068] like Figure 1 and Figure 4 , Figure 8 , Figure 12 As shown, the flared nozzle guide structure 5 is located at the inlet of the air film orifice channel of the air film orifice test piece 10. Its centerline is collinear with the spray centerline of the nozzle, and its large-diameter end covers the outlet area of ​​the nozzle 1 to efficiently collect and guide the atomized flow through the small-diameter end of the guide structure into the orifice. This structure can effectively converge the atomized cone ejected from the nozzle 1, guide more liquid crystal particles into the orifice, reduce scattering loss at the inlet edge, and overcome the spraying "blind zone" caused by the small orifice diameter.

[0069] The airflow drive structure 6 is a miniature suction or blowing device installed at the outlet of the air film orifice of the air film orifice test piece 10. During spraying, it generates a controllable auxiliary airflow within the orifice. This airflow can pull the atomized particles deeper into the orifice and promote their uniform circumferential distribution. It is particularly beneficial for improving the coating uniformity in the latter half and bottom of the orifice, forming a synergistic effect with the inlet spraying.

[0070] The lighting imaging module and temperature control module are located downstream of the spraying process (e.g., Figure 3 (See system schematic diagram). The illumination imaging module is responsible for exciting and recording the color changes of the liquid crystal coating during the heat transfer test. It typically includes an illumination device 11 and a high-resolution digital camera. In this embodiment, the illumination device 11 is a ring-shaped LED light source. The illumination device 11 is positioned directly in front of the inlet of the air film aperture on the test specimen, with its luminescent surface parallel to the inlet end face. The position and angle of the light source can be adjusted according to the aperture diameter and depth to project as uniform a diffuse light as possible into the deep aperture, minimizing shadows and reflections within the measurement field of view and avoiding the influence of photothermal effects on the liquid crystal temperature. The high-resolution camera records a complete image sequence of the liquid crystal color change with temperature on the inner wall of the aperture at a fixed frame rate, either through the observation window of the test system or directly at the inlet.

[0071] The temperature control module provides, monitors, and controls the standard thermal boundary conditions required for the test. This module may include an electric heater, high-precision thermocouples, a temperature scanner, and a flow controller. The electric heater heats the cooling gas flowing into the front cavity of the test specimen; the flow controller precisely sets and stabilizes the flow rate (Reynolds number Re) of the cooling gas passing through the film orifice; and the thermocouples positioned in the airflow channel and at specific locations on the test specimen monitor the airflow temperature and / or the inner wall temperature in real time via the temperature scanner, forming a closed-loop control system to ensure a rapid, stable, and controllable rise in the inlet fluid temperature of the film orifice throughout the transient test.

[0072] The data processing module is the central hub that ultimately transforms image and temperature data into scientific conclusions. This module is electrically connected to the camera in the illumination imaging module and the temperature acquisition device in the temperature control module to receive colorimetric image sequences and temperature data, thereby calculating the local heat transfer coefficient distribution of the inner wall of the film pores of the tested object. Specifically, the data processing module includes an image processing unit and a heat transfer coefficient calculation unit.

[0073] The image processing unit is responsible for converting color information into temperature information. Internally, it stores a precise correspondence between the colors of the thermochromic liquid crystal (such as RGB or HSV values) and temperature, established beforehand through calibration experiments. When processing experimental data, this unit reads each frame of the color image of the inner wall of the aperture captured by the camera and, based on the aforementioned color-temperature relationship, converts the image pixel-by-pixel into corresponding instantaneous temperature field data.

[0074] The heat transfer coefficient calculation unit is responsible for calculating the final heat transfer coefficient distribution based on temperature field data and other experimental parameters. This unit receives time-series temperature field data from the image processing unit, as well as fluid mainstream temperature and thermophysical parameters from the temperature control module. Its core calculation is based on a one-dimensional transient heat transfer inverse problem model. Specifically, for most areas within the film gas vent, this unit directly utilizes the wall temperature over time obtained from the image processing unit. The process of change, combined with the known initial temperature difference between the fluid and the wall and the material's thermophysical parameters (thermal conductivity) ,density Specific heat The local convective heat transfer coefficient at this location is obtained by calculating using the standard solution formula of the following one-dimensional semi-infinite thermal conductivity model:

[0075] T w = T 0 + ( T g − T 0 ) [ 1 − exp ( h 2 t ρ c λ ) erfc ( h t ( ρ c λ ) 1 / 2 ) ]

[0076] In the formula, The temperature at the measuring point on the wall of the test specimen. The initial temperature of the test specimen wall surface. For the incoming flow temperature, The convective heat transfer coefficient of the test specimen is given.

[0077] Specifically, the heat transfer coefficient calculation unit is also configured to correct the heat transfer coefficient calculation for the inlet region of the film gas vent. This correction function addresses measurement errors caused by the transverse thermal conduction effect in the inlet region. Specifically, a correction algorithm is integrated within the unit. Its core is to obtain and apply a time difference in transverse thermal conduction influence determined by a theoretical model. The specific steps of this correction algorithm are as follows:

[0078] First, two theoretical models of transient heat conduction in solids are established. The first model is used to simulate the absence of lateral heat conduction, achieved by setting anisotropic thermal conductivity for the wall surface, and the theoretical curve of the temperature change of the inlet wall surface of the film vent over time is obtained by solving the model. And record the time it takes to reach a specific temperature peak. The second model is used to simulate transverse heat conduction, achieved by setting a three-dimensional thermal conductivity coefficient, and the theoretical temperature curve at the same location is obtained by solving. Record the time it takes for them to reach the same peak temperature. .

[0079] Next, the time difference of the lateral thermal conduction effect is calculated, i.e. This time difference characterizes the temperature response hysteresis caused by the transverse thermal conduction effect.

[0080] Next, the experimental data is processed. The computing unit identifies and records the actual experimental time when the wall reaches its maximum green value from the temperature field data of the inlet area provided by the image processing unit. .

[0081] Subsequently, the corrected characteristic time is calculated, i.e. This step eliminates the interference of lateral heat conduction on the experimental measurement time.

[0082] Finally, the corrected heat transfer coefficient is calculated. The heat transfer coefficient calculation unit uses this corrected time... Substituting these values ​​into the standard solution formula based on the one-dimensional semi-infinite model, we can obtain a more accurate local heat transfer coefficient in the inlet region that eliminates the fundamental error.

[0083] Through this series of steps, the data processing module is finally able to output a complete, continuous, and uniformly accurate local heat transfer coefficient distribution of the entire film pore inner wall from the inlet to the outlet.

[0084] The method for measuring the heat transfer coefficient inside the leading edge spray film orifice, as an exemplary embodiment of the present invention, includes the following steps:

[0085] Step S1: Apply a uniform liquid crystal coating. For example... Figure 4 , Figure 8 , Figure 12 As shown, nozzle 1 is mounted on the posture adjustment mechanism 4. The air pressure, distance, and angle of nozzle 1 are adjusted to initiate spraying of a specific aperture type (straight aperture, constricted outlet, constricted inlet, etc.) on the air film aperture test piece 10. The posture adjustment mechanism 4 drives the nozzle 1 to move. Simultaneously, the airflow drive structure 6 is activated to provide auxiliary airflow, causing the atomized liquid crystal ejected from nozzle 1 to form a uniform thin film on the inner wall of the aperture under the guidance of the flared nozzle guide structure 5 and the assistance of the airflow drive structure 6, followed by static curing.

[0086] Step S2: Establish steady-state thermal boundary conditions. The coated film pore test specimen 10 is assembled onto the [structure / structure] via an external flange. Figure 3 The test wind tunnel shown is composed of an inlet chamber 7, a cavity 9, and an outlet extraction chamber 8. The length * width * height of the cavity is 40D * 10D * 8D, where D is the aperture of the film gas pores. The temperature control module is activated, and the target gas temperature and flow rate are set. The system is allowed to reach a fully developed steady-state flow and temperature field.

[0087] Step S3: Perform a transient test and collect data. Quickly switch or start the main heater to cause a step increase in the temperature of the gas flowing into the front cavity of the test piece. At the same time, activate the lighting device 11 (such as a ring LED light source) to provide uniform illumination inside the channel, ensuring clear liquid crystal color display without light or shadow; and simultaneously trigger the high-resolution camera to begin high-speed recording of the color change process of the liquid crystal coating on the inner wall of the hole. The temperature control module simultaneously records the temperature change process of the fluid.

[0088] Step S4: Data Processing and Heat Transfer Coefficient Calculation. The data processing module reads the image sequence and temperature data. First, it performs temperature field calibration conversion on the full-channel image; then, specifically for the inlet region, it calls the aforementioned transverse heat conduction correction subroutine to correct the feature color development time; finally, based on the transient heat conduction model, it calculates the local convective heat transfer coefficient of the entire inner wall of the film pore pixel by pixel, and outputs the distribution cloud map and statistical results.

[0089] To verify the effectiveness and versatility of the apparatus and method provided by this invention, three typical examples are described below, with corresponding test specimens as follows: Figure 4 , Figure 8 , Figure 12 As shown.

[0090] Example 1

[0091] For straight cylindrical air film orifices with an aperture D=10mm, an inclination angle θ=45°, and identical inlet and outlet orifice diameters, the spray coating process is as follows: Figure 4 As indicated by the arrows in the diagram. After completing the experiment, the Nu distribution within the pores was obtained as shown in the diagram. Figure 5 As shown, the test results ( Figure 5 (b) in the figure and the numerical simulation results ( Figure 5 The spatial distribution trends of (a) in the samples are highly consistent, both showing high heat exchange zones on both sides of the aperture and low heat exchange zones in the middle. Figure 6 The diagram shows a comparison of the spanwise average Nu distribution along the flow direction at three Re numbers. It can be seen that in the latter half of the channel (X / L>0.3), the experimental data and the simulated values ​​almost coincide, while there is a reasonable deviation in the inlet section because the flow has not yet fully developed. Figure 7 The surface-averaged Nu comparison shows that, under all test conditions, the measured values ​​( ) and numerical simulation values ​​( deviation () All values ​​were within 15%, which fully verifies the effectiveness of the device provided by the present invention for measuring inclined cylindrical hole structures.

[0092] Example 2

[0093] For a film gas vent with an inlet diameter D=5mm, an inclination angle θ=45°, and an outlet shrinkage of 30%, the spray coating process is as follows: Figure 8 As shown. Nu distribution cloud map obtained from the experiment ( Figure 9 (b) in the middle) and simulation results ( Figure 9 (a) in the figure matches well. The mean Nu distribution along the span of length is similar to that in the figure. Figure 10 As shown, the curves of the two are highly consistent. For example, the average Nu... Figure 11 The deviation was less than 15%, proving the applicability of this method to complex shrinkage outlet orifice types.

[0094] Example 3

[0095] For a film gas vent with an outlet diameter D=5mm, an inclination angle θ=45°, and an inlet shrinkage of 30%, the spray coating process is as follows: Figure 12 As shown. Figures 13 to 15 As shown, whether it is the distribution cloud map, spanwise average distribution, or surface average, the experimental results and numerical simulation results all show good consistency, with the deviation range being comparable to that of the aforementioned examples. This ultimately proves that the device and method provided by this invention can effectively overcome the problems of spraying, imaging, and principle errors caused by deep, small-diameter holes and complex geometry, and stably and reliably obtain high-precision heat transfer coefficient distribution data of the inner wall of different types of leading-edge spray film orifices.

[0096] Finally, it should be noted that the features mentioned and / or shown in the above description of exemplary embodiments of the present invention can be combined in the same or similar manner with one or more other embodiments, combined with or substituted for corresponding features in other embodiments. These combined or substituted technical solutions should also be considered to be included within the scope of protection of the present invention.

Claims

1. A device for measuring the heat transfer coefficient inside the leading edge spray film orifice, characterized in that: It includes a spraying module, an illumination and imaging module, a temperature control module, and a data processing module; The spraying module is used to coat the inner wall of the air film pore channel of the test piece with a uniform thermochromic liquid crystal coating, and includes a liquid crystal storage tank, a nozzle, a pressure controller, a posture adjustment mechanism, a horn-shaped flow guiding structure and an airflow driving structure. The liquid crystal storage tank is used to contain a hot-color liquid crystal solution; The nozzle inlet is connected to the liquid crystal storage tank via a fluid pipeline, and is used to atomize the liquid crystal solution and spray it onto the inner wall of the channel. The pressure controller is installed on the fluid pipeline and is used to adjust the pipeline pressure to control the liquid crystal ejection flow rate of the nozzle. The horn-shaped flow guiding structure is located at the inlet of the air film pore of the test piece, and is used to guide the atomized liquid crystal solution into the pore. The airflow drive structure is disposed at the outlet of the air film hole of the test piece and is used to provide auxiliary airflow to the channel; The posture adjustment mechanism is used to load the nozzle and can drive the nozzle to generate relative movement with respect to the test piece. The relative movement includes at least relative movement along the axial direction of the channel and relative movement in a plane perpendicular to the axial direction of the channel, so that the atomized liquid crystal solution ejected from the nozzle, guided by the flared mouth drainage structure and assisted by the airflow driving structure uniformly covers the entire inner wall of the channel. The illumination imaging module and the temperature control module are located downstream of the spraying module, and are respectively used to acquire the color development image of the liquid crystal coating and to provide, monitor and control the thermal boundary conditions; The data processing module is electrically connected to the illumination imaging module and the temperature control module, respectively, and is used to receive and process the color image and the temperature data collected by the temperature control module to calculate the local heat transfer coefficient distribution of the inner wall of the air film pore of the test piece.

2. The heat transfer coefficient measuring device inside the leading edge spray film orifice according to claim 1, characterized in that: The illumination imaging module includes a ring-shaped LED light source and a camera. The ring-shaped LED light source is used to provide uniform illumination to the channel, and the camera is used to acquire liquid crystal color images of the inner wall of the channel.

3. The heat transfer coefficient measuring device inside the leading edge spray film orifice according to claim 1 or 2, characterized in that: The temperature control module includes a heater, a thermocouple, a temperature scanner, and a flow controller. The heater is used to heat the cooling fluid flowing through the orifice, the flow controller is used to regulate the flow rate of the cooling gas, and the thermocouple is used to monitor the temperature of the cooling gas and / or the inner wall of the orifice through the temperature scanner.

4. The heat transfer coefficient measuring device inside the leading edge spray film orifice according to claim 1 or 2, characterized in that: The data processing module includes an image processing unit and a heat transfer coefficient calculation unit. The image processing unit is used to obtain the temperature field of the inner wall of the channel based on the color image. The heat transfer coefficient calculation unit is used to calculate the local heat transfer coefficient distribution based on the temperature field and the temperature data, combined with the heat transfer model.

5. The heat transfer coefficient measuring device inside the leading edge spray film orifice according to claim 4, characterized in that: The heat transfer coefficient calculation unit is configured to correct the heat transfer coefficient calculation of the air film inlet region, and the parameters on which the correction is based include the time difference of transverse heat conduction influence obtained from the theoretical model.

6. A method for measuring the heat transfer coefficient inside the leading edge spray film orifice, characterized in that, The device for measuring the heat transfer coefficient inside the leading edge spray film orifice, as described in any one of claims 1 to 5, is implemented and includes the following steps: Step 1: Using the spraying module, a uniform thermochromic liquid crystal coating is applied to the inner wall of the air film pore channel of the test piece. Step 2: Using the temperature control module, establish and control the thermal boundary conditions of the cooling gas flowing through the air film orifice; Step 3: Using the illumination imaging module, acquire the color rendering image of the liquid crystal coating under the thermal boundary conditions; Step 4: Using the data processing module, process the color image and the temperature data collected by the temperature control module to calculate the local heat transfer coefficient distribution of the inner wall of the air film pore.

7. The method for measuring the heat transfer coefficient inside the leading edge spray film orifice according to claim 6, characterized in that, Step 1 specifically includes: Step 1.1: Load the nozzle onto the pose adjustment mechanism; Step 1.2: Adjust the inlet pressure of the nozzle using the pressure controller, and start the nozzle to spray. Step 1.3: The position adjustment mechanism drives the test piece and the nozzle to generate relative motion, while controlling the airflow drive structure set at the outlet of the air film hole to provide auxiliary airflow, so that the atomized liquid crystal solution is evenly covered on the entire inner wall of the channel under the guidance of the funnel-shaped flow guide structure set at the inlet of the air film hole.

8. The method for measuring the heat transfer coefficient inside the leading edge spray film orifice according to claim 6 or 7, characterized in that, In step 4, when calculating the local heat transfer coefficient of the film gas inlet region, the following correction steps are performed: Obtain the time difference of lateral thermal conduction influence in the air film inlet region of the test piece, determined based on the theoretical model; The actual color development response time obtained from the color development image is corrected using the time difference. The corrected inlet region heat transfer coefficient is calculated based on the corrected time.

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