A pressure testing method for multi-strand non-uniform density gas flow field based on pressure-sensitive paint

Abstract

The application discloses a kind of based on pressure sensitive paint multi-strand non-equidensity gas flow field pressure test method, comprising: by calibration, the light intensity of pressure sensitive paint emits oxygen partial pressure, and then obtain the relationship between light intensity and oxygen partial pressure;Configuration oxygen-containing mixed gas, to replace multi-strand non-equidensity gas, ensure that the molar fraction of oxygen in flowing environment is invariable;Pressure sensitive paint is sprayed on the surface of the model to be measured, oxygen-containing mixed gas is supplied, and a flowing environment consistent with the pressure distribution of the required flow field is created;Image of the surface of the model to be measured sprayed with pressure sensitive paint under several groups of different conditions is shot, light intensity image is obtained, light intensity image is converted, and the pressure distribution of the surface of the model to be measured is calculated.The application creates a fluid domain with constant oxygen molar fraction by a specific ratio of oxygen-containing mixed gas, and realizes the surface pressure measurement of multi-strand non-equidensity gas flow field.

Description

Technical Field

[0001] This invention relates to the field of flow parameter measurement technology, and in particular to a pressure testing method based on a multi-stream non-uniform density gas flow field using pressure-sensitive paint. Background Technology

[0002] Measuring pressure distribution on an object's surface is a crucial part of aerodynamic research. Measuring surface pressure distribution is an indispensable component of many flow field tests. Traditional pressure measurement methods primarily involve placing pressure gauge holes on the measurement surface to guide gas to a pressure transmitter. However, creating holes on the measurement surface constitutes a contact measurement, directly affecting the flow, and is essentially a point measurement.

[0003] Pressure-sensitive paint (PSP), or pressure-sensitive coating for short, emits light of a specific wavelength when exposed to light of a certain wavelength. Due to the oxygen quenching effect, higher oxygen concentrations result in lower luminescence intensity. Since the oxygen concentration in the air is directly proportional to the oxygen partial pressure, and the mole fraction of oxygen in the air is constant, the pressure distribution on the surface of an object can be obtained by measuring the light intensity.

[0004] This characteristic has been widely used for pressure measurement on object surfaces. For example, the paper "Aerodynamic Applications of Pressure Sensitive Paint" uses a pressure-sensitive paint (PSP) to measure the surface pressure distribution of a blended wing-body aircraft. In typical applications, pressure-sensitive paints are used to measure pressure in fluid domains containing only air. However, in reality, it is also necessary to measure surface pressure when multiple airflows of different densities are mixed. For example, in film cooling, the main stream and jet streams are mixed, and the jet density is generally different from the main stream density. The paper "Experimental and Numerical Study of the Thermal Performance of a Film Cooled Turbine Platform" requires measuring the pressure field when the main stream is air and the jet stream is carbon dioxide; however, in this case, the property that carbon dioxide causes a constant mole fraction of oxygen in the fluid domain does not exist. Therefore, it uses the pressure distribution when the main stream and jet stream are air instead of the required pressure distribution. This may be acceptable at low speeds; however, as aerodynamic research becomes increasingly high-speed and complex, using air instead of a heterogeneous gas with a different density for pressure measurement is inaccurate.

[0005] In summary, there is currently a lack of methods for measuring the pressure field of multiple airflows with different densities mixed together using pressure-sensitive paint, especially under high-speed and complex flow conditions. Summary of the Invention

[0006] This invention proposes a pressure testing method for a multi-stream non-uniform density gas flow field based on pressure-sensitive paint, in order to solve the problems existing in the prior art, and to measure the pressure of a flow field with multiple mixed gas streams, especially when multiple gas streams of different densities are mixed.

[0007] To achieve the above objectives, the present invention provides a pressure testing method based on a multi-stream non-uniform density gas flow field of pressure-sensitive paint, comprising:

[0008] The light intensity and oxygen partial pressure emitted by the pressure-sensitive paint were obtained through calibration, and the relationship between light intensity and oxygen partial pressure was then obtained.

[0009] A mixture of oxygen-containing gases is prepared to replace multiple streams of non-isodense gases, ensuring that the mole fraction of oxygen in the flow environment remains constant.

[0010] The pressure-sensitive paint is sprayed onto the surface of the model to be tested, and the oxygen-containing mixed gas is supplied to create a flow environment consistent with the pressure distribution of the flow field required for measurement.

[0011] Several sets of images of the test model surface coated with the pressure-sensitive paint under different conditions were captured to obtain light intensity images. The light intensity images were then converted, and the pressure distribution on the test model surface was calculated.

[0012] Preferably, obtaining the relationship between the light intensity and the oxygen partial pressure includes:

[0013] The light intensity and oxygen partial pressure emitted by the pressure-sensitive paint are obtained through calibration. The calibration process between light intensity and oxygen partial pressure is carried out in the calibration chamber. The oxygen partial pressure and temperature under certain conditions are selected as reference oxygen partial pressure and reference temperature, and the light intensity under the same conditions is used as reference light intensity to obtain the relationship model between light intensity and oxygen partial pressure.

[0014] Preferably, the relationship model between light intensity and oxygen partial pressure is as follows:

[0015]

[0016] Among them, I ref I1 is the reference light intensity; I1 is the light intensity on the surface of the model under test under conditions of no light and no flow. The oxygen partial pressure is given under reference conditions; T ref is the reference temperature; x represents the changing test environment during the calibration process; I represents the oxygen partial pressure on the surface of the model under test condition x; x The light intensity is denoted as α.

[0017] Preferably, the oxygen-containing gas mixture is an oxygen-containing gas mixture with a required density and a specific ratio, wherein the conditions satisfied by the oxygen-containing gas mixture with the specific ratio include: having the same density as each of the multiple gases, and having the same mole fraction of oxygen in each of them.

[0018] Preferably, the different conditions include:

[0019] First condition: a dark, still environment to eliminate the influence of ambient light;

[0020] The second condition is that the light source is turned on and there is no moving environment, in order to match the reference light intensity.

[0021] The third condition is that the light source is turned on and a flowing environment is created using a specific ratio of oxygen-containing gas mixture.

[0022] Preferably, the light intensity image is converted to obtain a two-dimensional oxygen partial pressure matrix; wherein the two-dimensional oxygen partial pressure matrix is:

[0023]

[0024] Where I1 is the two-dimensional matrix of light intensity on the surface of the model under test under the first condition; I2 is the two-dimensional matrix of light intensity on the surface of the model under test under the second condition; and I3 is the two-dimensional matrix of light intensity on the surface of the model under test under the third condition. This is the partial pressure of oxygen under the second condition, which is equal to the partial pressure of oxygen under the reference condition during the calibration process; The third condition is the two-dimensional matrix of oxygen partial pressure on the surface of the model to be tested; T ref This is a reference temperature.

[0025] Preferably, the pressure distribution on the surface of the model under test is calculated based on the two-dimensional oxygen partial pressure matrix, wherein the expression for the pressure distribution on the surface of the model under test is:

[0026]

[0027] in, denoted as , where is the mole fraction of oxygen in the fluid domain, is a constant, and P3 is the pressure distribution matrix on the surface of the model to be tested.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] The method of this invention utilizes an oxygen-containing mixed gas with a corresponding density and a specific ratio to create a fluid domain environment that is consistent with the target pressure field and has a constant oxygen molar concentration, thereby enabling pressure measurement of multiple non-uniform density gas flow fields. Attached Figure Description

[0030] 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:

[0031] Figure 1This is a schematic diagram of a multi-stream non-uniform density gas flow field according to an embodiment of the present invention, showing two streams.

[0032] Figure 2 This is a schematic diagram of a pressure testing method using a multi-stream non-uniform density gas flow field based on pressure-sensitive paint, according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram comparing the measurement results and actual pressure distribution of the pressure testing method using a multi-stream non-uniform density gas flow field based on pressure-sensitive paint according to an embodiment of the present invention.

[0034] Among them, 1-pressure-sensitive paint coating, 2-model to be tested, 3-mixing pore, 4-mainstream, 5-jet with a density different from the mainstream, 6-light source, 7-scientific camera, 8-oxygen-containing mixed gas with a specific ratio. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] Example 1

[0038] like Figure 1 This embodiment of the test device is used in a specific scenario, including the model under test 2, the mixing hole 3, the main stream 4, and the jet 5 with a density different from the main stream.

[0039] like Figure 2 This embodiment provides a pressure testing device based on a multi-stream non-uniform density gas flow field of pressure-sensitive paint. The testing device includes a pressure-sensitive paint coating 1, a model to be tested 2, mixing holes 3, a main stream 4, a light source 6, a scientific camera 7, and an oxygen-containing mixed gas with a specific ratio 8.

[0040] like Figure 1 This invention proposes a pressure testing method based on a multi-stream non-uniform density gas flow field of pressure-sensitive paint, comprising:

[0041] Step 1: Calibrate the relationship between the light emission intensity of the pressure-sensitive paint and the oxygen partial pressure:

[0042] The calibration process between light intensity and oxygen partial pressure is performed in the calibration chamber. Oxygen partial pressure and temperature under certain conditions are selected as reference oxygen partial pressure and reference temperature, and light intensity under these conditions is used as reference light intensity. The relationship between light intensity and oxygen partial pressure is obtained as follows:

[0043]

[0044] Among them, I ref I1 is the reference light intensity; I1 is the light intensity on the surface of the model under test under conditions of no light and no flow. The oxygen partial pressure is given under reference conditions; T ref is the reference temperature; x represents the changing test environment during the calibration process; I represents the oxygen partial pressure on the surface of the model under test condition x; x The light intensity is denoted as α.

[0045] Step 2: Prepare a series of oxygen-containing gas mixtures with required densities and specific ratios; prepare specific oxygen-containing gas mixtures using argon, sulfur hexafluoride, and oxygen, ensuring that the density of the mixture is the same as that of each of the multiple gases, and that the mole fraction of oxygen is consistent, generally choosing the same mole fraction of oxygen as in air. Table 1 shows the mixing ratios when the mole fraction of oxygen in the mixture is the same as in air, and the ratio of the gas mixture to the air density is 1.5 and 2.0, respectively.

[0046] Table 1

[0047]

[0048] Step 3: Spray pressure-sensitive paint 1 onto the surface of the model to be tested 2.

[0049] Step 4: As Figure 2 Set up a scientific camera 7, set a filter in front of the camera lens, and take a light intensity image J1 under conditions of no light source.

[0050] Step 5: As Figure 2 The surface of the model under test 2 is illuminated by a light source 6 of a specific wavelength, which excites the pressure-sensitive paint to emit fluorescence. The light intensity image J2 is captured by a scientific camera 7. This operating condition is also called the reference condition. At this time, the ambient temperature is T. ref .

[0051] Step 6: As Figure 2 The flow parameters are set, and the surface of the model under test 2 is illuminated by a light source 6 of a specific wavelength. The light intensity image J3 is captured by a scientific camera 7.

[0052] Step 7: The surface static pressure distribution is obtained by processing the acquired fluorescence intensity images J1 to J3.

[0053] The processing method in step 7 includes the following steps:

[0054] Step 71: First, use MATLAB or other programs to read the light intensity images J1 to J3 and convert them into two-dimensional light intensity matrices I1 to I3 with light intensity values;

[0055] Step 72: Substitute the two-dimensional light intensity matrix corresponding to the above fluorescence intensity image into the following formula to calculate and obtain the oxygen partial pressure data on the surface of the model to be tested 3.

[0056]

[0057] in, The results were obtained through a pre-calibration experiment, which required ensuring that the paint spraying, lighting conditions, camera settings, and measurement process remained consistent. This is the oxygen partial pressure under the second condition, which is equal to the oxygen partial pressure under the reference condition during the calibration process.

[0058] Step 73: Calculate the pressure distribution on the surface of the model to be tested:

[0059]

[0060] in, This represents the mole fraction of oxygen in the fluid domain, and is a constant. When the mole fraction of oxygen in a specific oxygen-containing mixture is the same as the mole fraction of oxygen in air, the mole fraction of oxygen in air is taken.

[0061] Thus, the method mentioned in this invention has obtained the pressure distribution on the surface of the model under test by measuring pressure-sensitive paint.

[0062] Example 2

[0063] This embodiment uses numerical simulation to evaluate the measurement results of a pressure testing method based on a multi-stream non-uniform density gas flow field using pressure-sensitive paint. Pressure distribution measurements were performed under the following conditions: a main airflow at Mach 0.7 flows through a flat plate, and a jet orifice is opened on the plate, from which a mixture of sulfur hexafluoride and argon with a density twice that of air is ejected. In this embodiment, an oxygen-containing mixture with the same density as the jet and the same oxygen molar concentration as air is used instead of the original mixture. In this embodiment, CFX software is used to calculate and compare the pressure distribution under the two conditions using numerical simulation. Figure 3 For comparison, it can be seen that using a specific ratio of oxygen-containing gas mixture instead of multiple streams of non-uniformly dense gases can create a very close pressure distribution. Therefore, the pressure testing method based on the multi-stream non-uniformly dense gas flow field of pressure-sensitive paint is feasible.

[0064] The above are merely preferred embodiments 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 scope of the technology 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 pressure testing method based on a multi-stream non-uniform density gas flow field using pressure-sensitive paint, characterized in that, include: The light intensity and oxygen partial pressure emitted by the pressure-sensitive paint were obtained through calibration, and the relationship between light intensity and oxygen partial pressure was then obtained. A mixture of oxygen-containing gases is prepared to replace multiple streams of non-isodense gases, ensuring that the mole fraction of oxygen in the flow environment remains constant. The pressure-sensitive paint is sprayed onto the surface of the model to be tested, and the oxygen-containing mixed gas is supplied to create a flow environment consistent with the pressure distribution of the flow field required for measurement. Several sets of images of the surface of the test model coated with the pressure-sensitive paint under different conditions were captured to obtain light intensity images. The light intensity images were then converted, and the pressure distribution on the surface of the test model was calculated. Obtaining the relationship between the light intensity and oxygen partial pressure includes: The light intensity and oxygen partial pressure emitted by the pressure-sensitive paint are obtained through calibration. The calibration process between light intensity and oxygen partial pressure is carried out in the calibration chamber. The oxygen partial pressure and temperature under certain conditions are selected as reference oxygen partial pressure and reference temperature, and the light intensity under the certain conditions is used as reference light intensity to obtain the relationship model between light intensity and oxygen partial pressure. The different conditions include: First condition: a dark, still environment to eliminate the influence of ambient light; The second condition is that the light source is turned on and there is no moving environment, in order to match the reference light intensity. The third condition: the light source is turned on, and a flowing environment is created using a specific ratio of oxygen-containing gas mixture; The light intensity image is converted to obtain a two-dimensional matrix of oxygen partial pressure; wherein the two-dimensional matrix of oxygen partial pressure is: in, I 1 represents the two-dimensional matrix of light intensity on the surface of the model under test under the first condition; I 2 represents the two-dimensional matrix of light intensity on the surface of the model under test under the second condition; I 3 represents the two-dimensional matrix of light intensity on the surface of the model under test when the third condition is met; This is the partial pressure of oxygen under the second condition, which is equal to the partial pressure of oxygen under the reference condition during the calibration process; The third condition is the two-dimensional matrix of oxygen partial pressure on the surface of the model to be tested; For reference temperature; The pressure distribution on the surface of the model under test is calculated based on the oxygen partial pressure two-dimensional matrix, wherein the expression for the pressure distribution on the surface of the model under test is: in, Let be the mole fraction of oxygen in the fluid domain, and be a constant. This is the pressure distribution matrix on the surface of the model to be tested.

2. The pressure testing method based on a multi-stream non-uniform density gas flow field using pressure-sensitive paint according to claim 1, characterized in that, The relationship model between light intensity and oxygen partial pressure is as follows: in, Iref It is the reference light intensity; I1 The light intensity on the surface of the model under test under conditions of no light and no flow. The oxygen partial pressure is under reference conditions; For reference temperature; x The test environment changes during the calibration process; for x Oxygen partial pressure on the surface of the model under test under the given conditions; Ix The light intensity is denoted as α.

3. The pressure testing method based on a multi-stream non-uniform density gas flow field using pressure-sensitive paint according to claim 1, characterized in that, The oxygen-containing gas mixture is an oxygen-containing gas mixture with a required density and a specific ratio. The conditions that the oxygen-containing gas mixture with the specific ratio satisfies include: having the same density as each of the multiple gases and having the same mole fraction of oxygen in each of them.

Images