Calibration method for describing melting characteristics of volcanic ash particles in aero-engine

Abstract

The invention belongs to the technical field of material fusibility test calibration, and provides a calibration method for describing the fusion characteristic of volcanic ash particles in an aero-engine, and the calibration method comprises the following steps: (1) polishing a platinum-rhodium alloy sheet; (2) placing the volcanic ash particles on the surface of the platinum-rhodium alloy sheet, putting the platinum-rhodium alloy sheet into a heating furnace, and filling reaction atmosphere gas; (3) heating and cooling the volcanic ash particles, and recording the whole process by adopting a camera; and (4) calibrating four characteristic temperatures in combination with the image recorded by the camera and the temperature rising and falling data. According to the method, the shape change of the volcanic ash particles in the high-temperature melting process is researched, and the melting characteristics of the volcanic ash particles are represented through four characteristic temperatures.

Description

Technical Field

[0001] The invention relates to the technical field of material fusibility test calibration, and in particular to a calibration method for describing the melting characteristics of volcanic ash particles in an aircraft engine. Background Art

[0002] Volcanic ash plays a vital role in the operating environment of aircraft engines. When tiny particles produced by volcanic eruptions enter the high altitude, they may enter the aircraft engine in flight with the airflow. The silicate components rich in volcanic ash are very easy to melt at high temperatures. When these particles adhere to the surface of aircraft engine blades, they will melt quickly and form a layer of glassy deposits. This deposit not only affects the aerodynamic performance of the blades, but may also cause blade overheating, structural damage, and even cause engine failure or shutdown. Therefore, accurately describing and understanding the fusibility of volcanic ash is crucial to preventing potential failures of aircraft engines in volcanic eruption events.

[0003] Although the potential threat of volcanic ash to aircraft engines has been widely recognized, research on the fusibility of volcanic ash is still relatively limited. Existing fusibility test methods, such as those specified in PD CEN / TR 15404:2010, are mainly used to analyze the fusibility of solid fuel ash. These test methods usually describe the behavior of ash at high temperatures by measuring certain standardized temperature points, such as deformation temperature, hemispherical temperature and flow temperature. However, these standard definitions use ash pressed into ash columns, and the standardized temperature points are determined based on the shape characteristics of the ash columns at high temperatures. There is a large difference between the shape characteristics of ash columns and real volcanic ash particles. In addition, volatile gases are generated in the ash columns during the melting process. The gases that are not removed in time also affect the shape characteristics of the sample and thus affect the calibration of fusibility. Therefore, they cannot effectively reflect the complex melting behavior of volcanic ash.

[0004] Given the limitations of existing methods, it is particularly important to accurately describe the shape changes of spherical particles prepared from volcanic ash during the melting process. However, the existing definition of solubility is relatively general and cannot capture the morphological changes of spherical particles during the melting process. This limitation leads to greater uncertainty in the practical application of volcanic ash, especially in fields such as aeroengines that require material stability at high temperatures. Therefore, it is urgent to develop a calibration method that can accurately describe the melting behavior of spherical particles to improve the performance prediction and control capabilities of volcanic ash in high-temperature applications. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a calibration method for describing the melting characteristics of volcanic ash particles in aircraft engines. Different from the traditional ash fusibility test method, which has limitations in describing the melting behavior of spherical particles, especially volcanic ash particles, the present invention proposes to analyze the melting characteristics of volcanic ash particles by calibrating the four characteristic temperatures of volcanic ash during the high-temperature melting deformation process.

[0006] The technical solution of the present invention is as follows:

[0007] A calibration method for describing the melting characteristics of volcanic ash particles in an aeroengine comprises the following steps:

[0008] Step S1: polishing the platinum-rhodium alloy sheet;

[0009] Step S2: placing volcanic ash particles on the surface of the platinum-rhodium alloy sheet, placing the sheet in a heating furnace, and filling it with reaction atmosphere gas;

[0010] Step S3: performing a temperature rise and fall process on the volcanic ash particles, and using a camera to record the entire process;

[0011] Step S4: Combine the image recorded by the camera and the temperature rise and fall data to calibrate the following four characteristic temperatures:

[0012] Softening temperature: the temperature at which the contact angle of volcanic ash particles decreases to 97% of the initial contact angle;

[0013] Critical wetting temperature: the temperature at which the contact angle of volcanic ash particles reaches 90°;

[0014] Fast-slow spreading critical point temperature: the temperature at which the contact angle of volcanic ash particles decreases to 20% of the initial contact angle;

[0015] Complete spreading temperature: the temperature at which the contact angle of volcanic ash particles reaches its minimum.

[0016] Preferably, the size of the platinum-rhodium alloy sheet is (10-20 mm)×(10-20 mm)×(0.5-3 mm).

[0017] Preferably, in step S1, the polishing is performed using 800, 1000, 1500 and 2000 grit sandpapers respectively, the polishing time of each type of sandpaper is not less than 1 minute, and the polishing is followed by drying.

[0018] Preferably, in step S2, the platinum-rhodium alloy sheet is placed horizontally in the heating furnace.

[0019] Preferably, in step S2, the reaction atmosphere gas flows through the volcanic ash particles at a minimum linear velocity of 50-300 mm / min, and the reaction atmosphere gas fills the heating furnace and then stands for 5-20 minutes; the reaction atmosphere gas is an oxidizing gas or a reducing gas.

[0020] Preferably, the temperature increase and decrease in step S3 is carried out in the following manner:

[0021] Below 500℃, use a heating rate of 50-100℃ / min; 500-800℃, use a heating rate of 20-30℃ / min; above 800℃, use a heating rate of 3-15℃ / min; cool down at a rate of 5-15℃ / min to reduce the furnace temperature to below 50℃.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The calibration method proposed in the present invention for describing the melting characteristics of volcanic ash particles in aircraft engines can accurately describe the melting behavior of volcanic ash spherical particles. By calibrating four key angles and their corresponding temperatures - softening temperature (97% initial contact angle θ0), critical wetting temperature (contact angle of 90°), fast and slow spreading critical point temperature (20% initial contact angle θ0) and complete spreading temperature (minimum contact angle θ e ), the method can accurately predict the softening, spreading and final penetration behavior of volcanic ash at different temperatures. Its specific applications include: first, by evaluating the softening temperature of CMAS of different components at high temperature, it can provide a basis for the selection of coating materials, optimize its initial anti-corrosion ability, reduce the risk of failure of the coating due to early softening, and ensure the safe operation of the engine. Secondly, using the critical wetting temperature as an evaluation index, the starting point of CMAS spreading on the coating surface can be determined, providing data support for the stability design of the coating material at high temperature, and ensuring effective prevention of volcanic ash erosion. In addition, by measuring the critical point temperature of fast and slow spreading, the fluidity of CMAS under high temperature conditions can be evaluated, providing a technical basis for selecting coating materials with superior high temperature resistance and spreading ability, and improving coating performance. Finally, determining the complete spreading temperature can predict the penetration depth of CMAS when it is completely melted, which is crucial for the anti-corrosion performance and long-term stability of coating materials under extreme conditions. In summary, the present invention provides an important theoretical basis and technical support for the optimization design, material selection and quality control of aircraft engine coatings, promotes the research and development of new high temperature resistant coating materials, improves the overall performance and reliability of aircraft engines, and ensures aviation safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the drawings. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a flow chart of a calibration method for describing the melting characteristics of volcanic ash particles in an aircraft engine according to the present invention.

[0026] Figure 2 It is a schematic diagram of an operation scenario of the calibration method of the present invention.

[0027] Figure 3 It is the real-time shape characteristics of volcanic ash particles corresponding to the four characteristic temperatures. DETAILED DESCRIPTION

[0028] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0030] like Figure 3 As shown, the present invention studies the shape changes of volcanic ash particles during high-temperature melting and finds four characteristic angles and characteristic temperatures that can characterize their melting characteristics, which are:

[0031] (1) Softening temperature: The contact angle of volcanic ash particles begins to change. When the contact angle decreases to 97% of the initial contact angle, it indicates that the melting process begins and the shape of the particles begins to change. The temperature at this time is the softening temperature.

[0032] (2) Critical wetting temperature: The contact angle of volcanic ash particles just reaches 90°. According to Young's equation:

[0033] γ SG =γ SL +γ LG ·cosθ

[0034] In the formula, γ SG is the solid-gas interfacial tension, γ SL is the solid-liquid interfacial tension, γLG is the liquid-gas interfacial tension and θ is the contact angle.

[0035] When the contact angle θ = 90°, the solid-gas interface energy is equal to the solid-liquid interface energy, and the system reaches a critical equilibrium state, indicating that the particles begin to change from a non-wetting state to a wetting state, and the corresponding temperature is the critical wetting temperature.

[0036] (3) Fast-slow spreading critical point temperature: As the contact angle decreases, the rate of contact angle decrease also changes. When the contact angle becomes 20% of the initial contact angle, the rate of contact angle decrease of the volcanic ash particles slows down significantly, from a rapid decrease to a slow decrease stage. The corresponding temperature at this time is the fast-slow spreading temperature.

[0037] (4) Complete spreading temperature: When the contact angle of volcanic ash particles no longer changes with temperature, the particles have reached the limit of spreading degree, and the corresponding temperature is the complete spreading temperature.

[0038] In the furnace process of volcanic ash particles, the above four characteristic temperatures are calibrated, such as Figure 1-2 As shown, the following steps are required:

[0039] Step S1: Polishing the platinum-rhodium alloy sheet to eliminate the influence of roughness on subsequent tests.

[0040] When polishing, first select sandpaper for pretreatment, and select 800, 1000, 1500 and 2000 grit sandpaper for polishing respectively. The polishing time of each sandpaper shall not be less than 1 minute. After polishing, use polishing cloth for wet polishing. When polishing, select diamond polishing paste as the polishing medium and add an appropriate amount of deionized water. The polishing time shall not be less than 10 minutes. The polished platinum-rhodium alloy sheet is dried in an oven at 100°C.

[0041] Step S2: Place the volcanic ash particles on the surface of the platinum-rhodium alloy sheet and put them into the sample table of the heating furnace. Then turn on the gas flow meter to allow the reaction atmosphere gas to fill the furnace cavity.

[0042] The maximum temperature of the heating furnace used must reach 1500-2000℃, and the furnace cavity must have good air tightness. The platinum-rhodium alloy sheet should be placed horizontally to avoid errors caused by non-horizontal surfaces in subsequent tests. The reaction atmosphere gas flows through the volcanic ash particles at a minimum linear velocity of 50-300mm / min. After the reaction atmosphere gas fills the heating furnace, it is left to stand for 5-20 minutes. The reaction atmosphere gas is an oxidizing gas or a reducing gas.

[0043] Step S3: The volcanic ash particles are subjected to temperature rise and fall treatments, and the entire process is recorded using a camera.

[0044] The heating and cooling methods are as follows: below 500℃, use a heating rate of 50-100℃ / min; from 500-800℃, use a heating rate of 20-30℃ / min; above 800℃, use a heating rate of 3-15℃ / min; and cool down at a rate of 5-15℃ / min to reduce the furnace temperature to below 50℃. The camera takes a photo every 1-3℃.

[0045] Step S4: calibrate four characteristic temperatures by combining the images recorded by the camera and the temperature rise and fall data.

[0046] Example 1

[0047] Select a platinum-rhodium alloy sheet with a size of 12×12×1mm for polishing. Select a relatively flat side of the platinum-rhodium alloy sheet and polish it on 800-mesh gauze paper for 2 minutes and then observe the surface. If there are no obvious concave-convex defects, proceed to the next step, otherwise continue to increase the polishing time of 800-mesh sandpaper. Then select 1000-mesh sandpaper to rotate the sample plane 90° clockwise for 3 minutes, and observe that the scratches produced completely cover the scratches produced in the previous step before proceeding to the next step. Select 1500-mesh sandpaper to rotate the sample plane 90° clockwise for 3 minutes, and observe that the scratches produced completely cover the scratches produced in the previous step before proceeding to the next step. According to the above steps, finally select 2000-mesh sandpaper for polishing. After all the sandpaper polishing is completed, select the polishing cloth for further polishing, fix the polishing cloth on the rotating disk of the polishing machine, and apply an appropriate amount of diamond polishing paste on the polishing cloth. After the preparation is completed, place the sample on the surface of the polishing cloth and press it gently with your fingers to fix it, then turn on the polishing machine rotation switch and select 400 rpm. A small amount of deionized water was continuously added during the polishing process, and the polishing time was 15 min. The polished samples were naturally dried in an oven.

[0048] Place the polished platinum-rhodium alloy sheet on the sample stage in the heating furnace, and make sure that the sample stage is horizontal, otherwise the subsequent samples will be at risk of slipping. After the inspection, place volcanic ash particles with a diameter of 2mm in the center of the platinum-rhodium alloy sheet, and then close the furnace door. Turn on the camera to observe the sample and adjust the sample image in the center area of ​​the field of view, then fine-tune the focus to make the sample outline clear, and set the camera to take a photo every 1°C.

[0049] Select carbon dioxide as the atmosphere gas, open the valve of the gas cylinder, and set the gas flow meter to 100mm / min. At this time, the gas begins to enter the furnace chamber at a fixed flow rate. In order to allow the carbon dioxide to fully fill the furnace chamber, proceed to the next step 15 minutes after the gas flow meter is set.

[0050] When setting the heating and cooling program, the heating and cooling rate is carried out in stages. When heating, the heating rate below 500℃ is 80℃ / min, the heating rate between 500-800℃ is 20℃ / min, and the heating rate above 800℃ is 5℃ / min. When cooling, the cooling rate is 10℃ / min to reduce the furnace temperature to 30℃.

[0051] Repeat the above operation three times, export the temperature rise and fall data and the real-time image data taken by the camera each time, and extract the specific values ​​of the four characteristic temperatures. The values ​​of the characteristic temperatures obtained in the three tests are softening temperature: 941℃, 944℃, 944℃, critical wetting temperature: 1017℃, 1015℃, 1016℃, fast-slow spreading critical point temperature: 1158℃, 1155℃, 1159℃, and complete spreading temperature: 1271℃, 1275℃, 1276℃. After calculation, the difference between the maximum and minimum values ​​of each characteristic temperature in the three tests is less than 5℃, which is a reasonable and correct test result. After averaging, the final four characteristic temperatures are softening temperature: 943℃, critical wetting temperature: 1016℃, fast-slow spreading critical point temperature: 1157.3℃, and complete spreading temperature: 1274℃. According to the real-time image in the original data, it is verified that the shape of the volcanic ash particles at each characteristic temperature is consistent.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0054] In the present invention, the terms "first", "second", "third", "fourth" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise clearly defined.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A calibration method for describing the melting characteristics of volcanic ash particles in an aircraft engine, characterized in that: The following steps are involved: Step S1: polishing the platinum-rhodium alloy sheet; Step S2: placing volcanic ash particles on the surface of the platinum-rhodium alloy sheet, placing the sheet in a heating furnace, and filling it with reaction atmosphere gas; Step S3: performing a temperature rise and fall process on the volcanic ash particles, and using a camera to record the entire process; Step S4: Combine the image recorded by the camera and the temperature rise and fall data to calibrate the following four characteristic temperatures: Softening temperature: the temperature at which the contact angle of volcanic ash particles decreases to 97% of the initial contact angle; Critical wetting temperature: the temperature at which the contact angle of volcanic ash particles reaches 90°; Fast-slow spreading critical point temperature: the temperature at which the contact angle of volcanic ash particles decreases to 20% of the initial contact angle; Complete spreading temperature: the temperature at which the contact angle of volcanic ash particles reaches its minimum.

2. The calibration method according to claim 1, characterized in that: The size of the platinum-rhodium alloy sheet is (10-20 mm)×(10-20 mm)×(0.5-3 mm).

3. The calibration method according to claim 1, characterized in that: In step S1, the polishing is performed using 800, 1000, 1500 and 2000 mesh sandpapers respectively, and the polishing time of each type of sandpaper is not less than 1 minute. Drying is performed after polishing.

4. The calibration method according to claim 1, characterized in that: In the step S2, the platinum-rhodium alloy sheet is placed horizontally in the heating furnace.

5. The calibration method according to claim 1, characterized in that: In step S2, the reaction atmosphere gas flows through the volcanic ash particles at a minimum linear velocity of 50-300 mm / min, and the reaction atmosphere gas fills the heating furnace and then stands for 5-20 minutes.

6. The calibration method according to claim 1, characterized in that: The reaction atmosphere gas is an oxidizing gas or a reducing gas.

7. The calibration method according to claim 1, characterized in that: The temperature rise and fall in step S3 is carried out in the following manner: Below 500℃, use a heating rate of 50-100℃ / min; 500-800℃, use a heating rate of 20-30℃ / min; Above 800℃, a heating rate of 3-15℃ / min is used; when cooling, a cooling rate of 5-15℃ / min is used to reduce the furnace temperature to below 50℃.

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