Air film cooling effect and comprehensive cooling effect synchronous measurement method based on temperature-sensitive paint and pressure-sensitive paint

Abstract

The application discloses a kind of based on temperature-sensitive paint and pressure-sensitive paint air film cooling effect and comprehensive cooling effect synchronous measurement method, comprising: obtaining the model to be measured, adding paint coating on the surface of the model to be measured, paint coating includes: temperature-sensitive paint, pressure-sensitive paint and white primer coating;Obtain the model to be measured under several environments;Based on the model to be measured under each environment, the surface of the model to be measured is photographed by scientific camera, and temperature light intensity image and pressure light intensity image are obtained respectively;Based on temperature light intensity image and pressure light intensity image, the air film cooling effect of the surface of the model to be measured is calculated;The surface temperature of the model to be measured is obtained, and the comprehensive cooling effect of the surface of the model to be measured is calculated based on pressure light intensity image and surface temperature.The application corrects the light intensity change of pressure-sensitive paint under non-isothermal condition by temperature-sensitive paint, obtains air film cooling effect, and simultaneously obtains the comprehensive cooling effect of the surface to be measured under non-isothermal condition by temperature-sensitive paint, to reduce the difficulty of air film cooling experiment.

Description

Technical Field

[0001] This invention belongs to the field of cooling efficiency measurement technology for hot-end components of aero-engines, and particularly relates to a method for simultaneously measuring the film cooling efficiency and overall cooling efficiency based on temperature-sensitive paint and pressure-sensitive paint. Background Technology

[0002] Gas turbine engines are thermal power plants based on the Brayton cycle, widely used in industry due to their high output power and thermal efficiency. Experience shows that, with unchanged engine size, a 56K increase in turbine inlet temperature can increase gas turbine thrust by 8-13% and cycle efficiency by 2-4%. Currently, the turbine inlet temperature of advanced aero engines exceeds 2000K, while the temperature resistance limit of turbine blade materials is much lower than the turbine inlet temperature. Therefore, efficient cooling technologies are essential to ensure normal operation. Film cooling (FSM) is one of the important cooling methods for hot-end components of turbines. FSM is achieved by creating discrete holes on the surface of the turbine blades, drawing the cooling medium from the inside of the blades to the outer wall. Under the influence of the main gas flow, the cooling medium is pressed onto the blade surface to form a film, separating the wall from the high-temperature main gas flow and simultaneously carrying away heat from the wall.

[0003] One of the key evaluation parameters for film cooling is film cooling efficiency (FSI), which is numerically equal to the recovery temperature of the fluid on the wall surface after mixing the mainstream combustion gas and the cold air under adiabatic conditions. When the FSI equals 1, it indicates that the area near the wall is entirely filled with cold air, resulting in the best cooling effect; when the FSI equals 0, it indicates that the area near the wall is entirely filled with mainstream combustion gas, and the cold air does not provide protection. Therefore, FSI can be used to quantitatively analyze the effect of the film cooling covering the wall surface. However, in the actual design of hot-end components of aero-engines, the actual temperature of the wall surface is also a very important parameter, as it determines the service life and reliability of the hot-end components. The surface temperature of the hot-end components is determined by a combination of external film cooling, internal cooling, and solid-state heat conduction, i.e., the fluid-thermal-solid coupling condition. Since it is difficult to measure under engine operating conditions, in actual experimental research, the surface temperature of the hot-end components is usually modeled and studied in a dimensionless manner, i.e., the comprehensive cooling efficiency (CRE).

[0004] Currently, the measurement of film cooling effect based on pressure-sensitive paint technology has been widely applied in film cooling research. Zhang et al. first proposed a method for measuring film cooling effect based on pressure-sensitive paint technology in "Flat Plate Film Cooling Measurements using PSP Gas Chromatograph Techniques". Charbonnier, in his paper "Experimental and Numerical Study of the Thermal Performance of a Film Cooled Turbine Platform", derived the formula to achieve measurement under conditions where the secondary flow density is inconsistent with the mainstream density, using carbon dioxide as the tracer gas. When pressure-sensitive paint is irradiated with a specific wavelength, it emits fluorescence of another specific wavelength. At the same time, pressure-sensitive paint exhibits oxygen quenching, so the fluorescence intensity changes with the oxygen concentration (or pressure) around the paint. Both can be described by the Stern-Volmer equation. In measuring the cooling effect of a gas film, pressure-sensitive paint is sprayed onto the test surface, and the cooling medium is replaced with an oxygen-free gas. When the cold gas is ejected from the gas film orifice, the fluorescence intensity at the gas film coverage area changes. By analyzing the relationship between light intensity and concentration (or pressure), the oxygen concentration at the gas film coverage area can be further obtained. Based on the mass transfer simulation heat transfer theory, a gas film cooling effect distribution similar to that under adiabatic conditions can be obtained. However, since pressure-sensitive paint is quite sensitive to temperature, the above method requires the temperature difference between the main flow and the secondary flow to be less than 1K to maintain the wall surface under isothermal conditions. This places high demands on temperature control during the experiment.

[0005] The key to comprehensive cooling effect measurement is obtaining the temperature of the test wall surface. There are various measurement methods, including infrared thermometry, liquid crystal thermometry, thermocouple thermometry, and temperature-sensitive paint. Temperature-sensitive paint, based on the temperature quenching mechanism, is highly sensitive to temperature changes. Its method for measuring solid surface temperature has been widely applied; for example, in the test "A Test Method for Measuring the Transition Point of a Low-Temperature Transonic Device (TSP)," temperature-sensitive paint is used to locate the transition point by measuring temperature.

[0006] In film cooling characteristic measurements, the overall cooling effect needs to be measured under conditions of temperature difference between the mainstream and the cooling gas, and thermal conductivity at the wall surface—that is, under fluid-thermal-structure coupling conditions. However, previous studies on film cooling effect have mostly been conducted under adiabatic conditions. According to previous research, the pattern of film coverage on the wall surface under fluid-thermal-structure coupling conditions differs from that under adiabatic conditions. Obtaining both film cooling effect and overall cooling effect simultaneously under fluid-thermal-structure coupling conditions is beneficial for further understanding the influence mechanism of the film cooling effect on the temperature distribution of turbine hot-end components. Previous measurement methods could only measure one of the film cooling effect or the overall cooling effect, and could not simultaneously obtain both. Summary of the Invention

[0007] This invention proposes a method for simultaneously measuring the air film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint, in order to solve the technical problems existing in the prior art.

[0008] To achieve the above objectives, this invention provides a method for simultaneously measuring the film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint, comprising:

[0009] Obtain the model to be tested, and add a paint coating to the surface of the model to be tested. The paint coating includes: a temperature-sensitive paint, a pressure-sensitive paint, and a white primer coating.

[0010] Acquire test models under several different environments; based on the test model under each environment, take pictures of the surface of the test model using a scientific camera to obtain temperature and light intensity images and pressure and light intensity images respectively.

[0011] Based on the temperature light intensity image and the pressure light intensity image, the air film cooling effect on the surface of the model under test is calculated.

[0012] The surface temperature of the model under test is obtained, and the overall cooling effect of the surface of the model under test is calculated based on the temperature light intensity image and the surface temperature.

[0013] Preferably, the temperature-sensitive paint and the pressure-sensitive paint are combined to form a two-component coating, and the coating thickness of both the two-component coating and the white primer coating is controlled within a thickness threshold.

[0014] Preferably, the plurality of environments includes: a first environment, a second environment, a third environment, and a fourth environment;

[0015] The first environment is a dark, non-flowing environment;

[0016] The second environment is a light-filled, non-flowing environment;

[0017] The third environment is an environment with light and flowing jets of air.

[0018] The fourth environment is an environment with light, flowing jets, and heterogeneous gases.

[0019] Preferably, the process of calculating the film cooling effect on the surface of the model under test includes:

[0020] The temperature and light intensity images and the pressure and light intensity images are respectively subjected to matrix transformation to obtain a two-dimensional temperature matrix and a two-dimensional pressure matrix. Based on the temperature and pressure two-dimensional matrices, the oxygen partial pressure data is calculated, and the molecular weight ratio of the foreign gas to air is obtained. Based on the oxygen partial pressure data and the molecular weight ratio, the gas film cooling effect on the surface of the model under test is calculated.

[0021] Preferably, the process of calculating the oxygen partial pressure data includes:

[0022] Substituting the temperature two-dimensional matrix and the pressure two-dimensional matrix into the formula for calculating the corrected light intensity ratio matrix, the corrected light intensity ratio matrices for the third environment and the fourth environment are calculated respectively. Based on the corrected light intensity ratio matrix, the oxygen partial pressure data is calculated using the formula for calculating oxygen partial pressure.

[0023] Preferably, the formula for calculating the light intensity ratio matrix is ​​modified as follows:

[0024] ;

[0025] ;

[0026] Where r3 and r4 are the corrected light intensity matrices of the surface of the model under test under the conditions of air and heterogeneous gas, respectively; r ref I1 to I4 are the corrected light intensity matrix of the surface of the model under test under reference conditions; J1 to J4 are the two-dimensional temperature matrix and J1 to J4 are the two-dimensional pressure matrix.

[0027] Preferably, the formula for calculating oxygen partial pressure is:

[0028]

[0029] Where p is the oxygen partial pressure near the surface of the model under test during the test; p ref The oxygen partial pressure near the surface of the model under test is given by the reference condition; A(T) and B(T) are the performance parameters of the pressure-sensitive paint, respectively. ref / r is the corrected light intensity ratio matrix.

[0030] Preferably, the process of calculating the overall cooling effect of the surface of the model under test includes:

[0031] The temperature and light intensity images corresponding to the first environment, the second environment, and the fourth environment are respectively subjected to matrix transformation to obtain a two-dimensional temperature matrix corresponding to the temperature and light intensity image. Based on the two-dimensional temperature matrix, the temperature matrix data corresponding to the surface temperature of the model under test is obtained by using the temperature matrix calculation formula. Based on the temperature matrix data, the comprehensive cooling effect of the surface of the model under test is calculated.

[0032] Preferably, when there is one scientific camera, the temperature-sensitive paint and pressure-sensitive paint on the surface of the model to be tested are photographed by switching the filter in front of the lens of the scientific camera.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] This invention provides a method for simultaneously measuring the cooling effect and overall cooling effect of air film based on thermosensitive paint and pressure-sensitive paint. This method uses thermosensitive paint to correct the light intensity change of pressure-sensitive paint under non-isothermal conditions, thereby obtaining the cooling effect of air film. It can also use thermosensitive paint to simultaneously obtain the overall cooling effect of the test surface under non-isothermal conditions, reducing the difficulty of air film cooling experiments and providing a new method for further understanding the air film cooling mechanism under non-isothermal conditions. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of a test model of the present invention, which is coated with a two-component coating of white primer, temperature-sensitive paint and pressure-sensitive paint.

[0037] Figure 2 This is a diagram of a device for obtaining an image of the surface light intensity of a model under no-light conditions, according to an embodiment of the present invention.

[0038] Figure 3 This is a diagram of a device for obtaining an image of the surface light intensity of a model under illumination, according to an embodiment of the present invention.

[0039] Figure 4 This is a diagram of a device for capturing the surface light intensity of a model under test under conditions of light, current flow, and cold air, according to an embodiment of the present invention.

[0040] Figure 5 This is a schematic diagram illustrating an embodiment of the present invention using a scientific camera and two filters;

[0041] Among them, 1-two-component coating, 2-white primer coating, 3-model to be tested, 4-air film pore, 5-cold air, 6-mainstream, 7-light source, 8-filter, 9-scientific camera. Detailed Implementation

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0044] Example 1

[0045] like Figure 1-4This embodiment provides a device for simultaneously measuring the cooling effect and overall cooling effect of air film under non-isothermal conditions based on thermosensitive paint and pressure-sensitive paint. The testing device includes a two-component coating of thermosensitive paint and pressure-sensitive paint 1, a white primer coating 2, a model to be tested 3, an air film hole 4 opened on the model to be tested, a cooling air 5, a main stream 6, a light source of a specific wavelength 7, a filter that transmits light through a specific wavelength 8, and a scientific camera 9 for capturing fluorescence intensity.

[0046] Example 2

[0047] This embodiment provides a method for simultaneously measuring the air film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint, including:

[0048] Step 1: Sequentially spray a white primer coating 2, a two-component coating 1 consisting of a temperature-sensitive paint and a pressure-sensitive paint onto the surface of the model to be tested 3. The white primer coating 2 must be evenly sprayed onto the surface of the model to be tested 3, and the coating thickness must be controlled within 20 mm. The two-component coating 1 consisting of the temperature-sensitive paint and the pressure-sensitive paint must be evenly sprayed onto the surface of the white primer coating 2, and the coating thickness must be controlled within 30 mm. The coating thickness is controlled to reduce the impact of the coating's thermal conductivity on the surface temperature of the model to be tested.

[0049] Step 2: As Figure 2 Two scientific cameras 9 are set up to capture the fluorescence intensity of the thermosensitive paint and the pressure-sensitive paint respectively. Under the condition of no light source, they capture light intensity images W1 and Y1 respectively. The main difference between the two scientific cameras 9 used to capture the fluorescence intensity images of the thermosensitive paint and the pressure-sensitive paint is that a filter 8 is added in front of the lens. The filter 8 can transmit light of a specific wavelength. The wavelengths transmitted by the two filters 8 are close to the fluorescence wavelengths of the thermosensitive paint and the pressure-sensitive paint respectively.

[0050] Step 3: As Figure 3 The surface of the model under test 3 is illuminated by a light source 7 of a specific wavelength, exciting the thermosensitive paint and pressure-sensitive paint to emit fluorescence. Two scientific cameras 9 simultaneously photograph the surface of the model under test 3, obtaining reference light intensity images W2 and Y2, respectively. This operating condition is also called the reference condition, and the ambient temperature is T. ref In this embodiment, the two-component coating of thermosensitive paint and pressure-sensitive paint is the Binary FIB coating from ISSI. The wavelength of the excitation light source 7 is 400nm, and the fluorescence wavelengths of the thermosensitive paint and pressure-sensitive paint are 650nm and 550nm, respectively.

[0051] Step 4: As Figure 4 Turn on the main flow 6 (air) and the cold air 5 (air) and set the flow and temperature parameters. Illuminate the surface of the model under test with a 400nm wavelength light source 7. Then, use two scientific cameras 9 to capture fluorescence intensity images W3 and Y3 on the surface of the model under test 3, respectively. The flow and temperature parameters include the inflow velocity U of the main flow 6, the flow rate M of the cold air 5, and their temperatures T.g T c

[0052] Step 5: As Figure 4 The surface of the model under test is illuminated by a light source 7 with a wavelength of 400nm. The flow parameters and temperature parameters of the main flow 6 are kept unchanged. The cold gas 5 is replaced with an alien gas (without oxygen). In this embodiment, it is nitrogen. The flow parameters and temperature parameters of the cold gas 5 are set in the same way as in step 4. After the flow field and temperature parameters stabilize, two scientific cameras 9 are used to capture the fluorescence intensity images W4 and Y4 on the surface of the model under test 3.

[0053] Step 6: By processing the acquired fluorescence intensity images W1~W4 and Y1~Y4, the air film cooling effect under non-isothermal conditions is obtained;

[0054] The non-isothermal film cooling treatment method in step 6 includes the following steps:

[0055] Step 61: First, use MATLAB or other programs to read the light intensity images W1~W4 and Y1~Y4 and convert them into two-dimensional light intensity matrices I1~I4 and J1~J4, respectively, representing the light intensity values.

[0056] Step 62: Substitute the two-dimensional intensity matrix corresponding to the above fluorescence intensity image into the following formula to calculate:

[0057] ;

[0058] ;

[0059] Where r3 and r4 are the corrected light intensity matrices of the surface of the model 3 under the conditions of air and heterogeneous gas, respectively; r ref It is the corrected light intensity matrix of the surface of the model 3 under the reference condition.

[0060] Step 63: Modify the light intensity ratio matrix r ref / r3 and r ref Substituting / r4 into the following formulas, we obtain the oxygen partial pressure data near the surface of the model 3 under test, p3 / p. ref and p4 / p ref :

[0061]

[0062] Where p is the oxygen partial pressure near the surface of the model 3 under test during the test; p ref The oxygen partial pressure near the surface of the model 3 under reference conditions is denoted as A(T) and B(T), which are the performance parameters of the pressure-sensitive paint and are temperature-dependent. These parameters can be obtained through a pre-calibration experiment. The calibration experiment requires ensuring that the paint spraying, lighting conditions, camera settings, and experimental measurement process are consistent.

[0063] Step 64: The formula for defining the concentration of the air-film cooling effect is as follows:

[0064]

[0065] Among them, C x Let C4 be the mass concentration of oxygen. Since the gas injected through the film vent is an oxygen-free gas, with air as the mainstream and oxygen as the tracer gas, C4 in the formula actually represents the oxygen mass concentration near the wall after the foreign gas mixes with the mainstream gas. Furthermore, since... The cooling effect of the gas film on the surface of the model can be obtained by using the measured oxygen partial pressure data near the surface of the model. The calculation formula is as follows:

[0066]

[0067] Where C is the ratio of the molecular weight of the foreign gas to that of air.

[0068] Step 7: By processing the acquired light intensity images W1, W2 and W4, the temperature distribution on the surface of the model under test under non-isothermal conditions is obtained, and then the overall cooling effect is calculated.

[0069] The fluorescence intensity changes of the temperature-sensitive paint and the pressure-sensitive paint are similar under the same temperature change, meaning that the fluorescence intensity ratio of the temperature-sensitive paint and the pressure-sensitive paint remains basically unchanged at different temperatures.

[0070] The comprehensive cooling effect treatment method under non-isothermal conditions in step 7 includes the following steps:

[0071] Step 71: Substitute the two-dimensional matrices I1, I2, and I4 corresponding to the light intensity images W1, W2, and W4 into the following formula to calculate:

[0072] ;

[0073] Among them, T4 is the matrix data of the surface temperature of the model 3 under the condition of step 5, and D(T) and E(T) are the performance parameters of the temperature-sensitive paint, which can be obtained through pre-calibration experiments. The calibration experiments need to ensure that the paint spraying, lighting conditions, camera settings and experimental measurement process are consistent.

[0074] Step 72: Substitute the calculated surface temperature T4 of the test model into the following formula to obtain the overall cooling effect of the surface of test model 3:

[0075] .

[0076] Thus, the method mentioned in this invention achieves a comprehensive cooling effect by utilizing non-isothermal conditions and thermosensitive paint, and corrects the light intensity change of pressure-sensitive paint under non-isothermal conditions by using thermosensitive paint, solving the measurement problem of pressure-sensitive paint under non-isothermal conditions, and realizing the simultaneous measurement of air film cooling effect and comprehensive cooling effect under non-isothermal conditions.

[0077] Example 3

[0078] This implementation plan also has another form, such as Figure 5 As shown, the two scientific cameras 9 can be replaced with one scientific camera, with the other steps remaining unchanged. The only difference is that when capturing the fluorescence intensity of pressure-sensitive paint and temperature-sensitive paint respectively, the fluorescence intensity images of the surface of the model under test are captured by switching the filter 8 in front of the camera lens.

[0079] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for simultaneously measuring the cooling effect and overall cooling effect of air film based on temperature-sensitive paint and pressure-sensitive paint, characterized in that, Includes the following steps: Obtain the model to be tested, and add a paint coating to the surface of the model to be tested. The paint coating includes: a temperature-sensitive paint, a pressure-sensitive paint, and a white primer coating. Acquire test models under several different environments; based on the test model under each environment, take pictures of the surface of the test model using a scientific camera to obtain temperature and light intensity images and pressure and light intensity images respectively. Several environments include: environment 1, environment 2, environment 3, and environment 4; The first environment is a dark, non-flowing environment; The second environment is a light-filled, non-flowing environment; The third environment is an environment with light and flowing jets of air. The fourth environment is an environment with light, flowing jets, and heterogeneous gases; Based on the temperature light intensity image and the pressure light intensity image, the air film cooling effect on the surface of the model under test is calculated. The process of calculating the film cooling effect on the surface of the model under test includes: The temperature light intensity image and the pressure light intensity image are respectively subjected to matrix transformation to obtain a two-dimensional temperature matrix and a two-dimensional pressure matrix. Based on the two-dimensional temperature matrix and the two-dimensional pressure matrix, the oxygen partial pressure data is calculated, the molecular weight ratio of the foreign gas to air is obtained, and the gas film cooling effect on the surface of the model under test is calculated based on the oxygen partial pressure data and the molecular weight ratio. The process of calculating oxygen partial pressure data includes: Substitute the temperature two-dimensional matrix and the pressure two-dimensional matrix into the formula for calculating the corrected light intensity ratio matrix to obtain the corrected light intensity ratio matrix in the third environment and the fourth environment, respectively. Based on the corrected light intensity ratio matrix, the oxygen partial pressure data is calculated using the oxygen partial pressure calculation formula. Corrected formula for calculating the intensity ratio matrix: ； ； Where r3 and r4 are the corrected light intensity matrices of the surface of the model under test under the conditions of air and heterogeneous gas, respectively; r ref I1 to I4 are the corrected light intensity matrix of the surface of the model under test under reference conditions; J1 to J4 are the two-dimensional temperature matrix and J1 to J4 are the two-dimensional pressure matrix. The surface temperature of the model under test is obtained, and the overall cooling effect of the surface of the model under test is calculated based on the temperature light intensity image and the surface temperature. The process of calculating the overall cooling effect on the surface of the model under test includes: The temperature and light intensity images corresponding to the first environment, the second environment, and the fourth environment are respectively subjected to matrix transformation to obtain a temperature two-dimensional matrix corresponding to the temperature and light intensity image. Based on the temperature two-dimensional matrix, the temperature matrix data corresponding to the surface temperature of the model under test is obtained by using the temperature matrix calculation formula. Based on the temperature matrix data, the comprehensive cooling effect of the surface of the model under test is calculated. The formula for calculating the temperature matrix is: ； Where T4 is the matrix data of the surface temperature of the model under test, D(T) and E(T) are the performance parameters of the temperature-sensitive paint, and T ref The ambient temperature is for reference conditions.

2. The method for simultaneous measurement of air film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint according to claim 1, characterized in that, The temperature-sensitive paint and the pressure-sensitive paint are combined to form a two-component coating, and the coating thickness of the two-component coating and the white primer coating are both controlled within the thickness threshold.

3. The method for simultaneous measurement of air film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint according to claim 1, characterized in that, Formula for calculating oxygen partial pressure: Where p is the oxygen partial pressure near the surface of the model under test during the test; p ref The oxygen partial pressure near the surface of the model under test is given by the reference condition; A(T) and B(T) are the performance parameters of the pressure-sensitive paint, respectively. ref / r is the corrected light intensity ratio matrix.

4. The method for simultaneous measurement of air film cooling effect and overall cooling effect based on temperature-sensitive paint and pressure-sensitive paint according to claim 1, characterized in that, When there is only one scientific camera, the temperature-sensitive paint and pressure-sensitive paint on the surface of the model to be tested are photographed by switching the filter in front of the lens of the scientific camera.

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