Method for measuring salt concentration distribution on surface of engine compressor blade

Abstract

The application provides a method for measuring salt concentration distribution on the surface of an engine compressor blade, comprising average salt concentration measurement and local salt concentration measurement. The method for measuring salt concentration distribution on the surface of an engine compressor blade is simple to operate, high in detection precision, can simultaneously obtain the overall and local salt concentration data on the blade surface, can complete in-situ detection without disassembling the blade, provides a basis for engine compressor corrosion protection and maintenance, and is suitable for salt concentration detection of related parts such as the compressor blade and the wheel disc of various aviation and ship engine compressors.

Description

Technical Field

[0001] This invention relates to the field of aero-engine component testing technology, and in particular to a method for determining the salt concentration distribution on the surface of an engine compressor blade. Background Technology

[0002] When engine compressor blades operate in marine or high-salt-spray environments, salt spray particles in the air adhere to the blade surface, forming a salt deposit layer. This deposit layer can form an electrolyte solution in humid environments, causing electrochemical corrosion. Simultaneously, the deposit layer alters the blade surface roughness and aerodynamic shape, leading to decreased compressor efficiency. Severe corrosion can cause safety accidents such as blade chipping and breakage. Therefore, accurately measuring the salt concentration on the blade surface, including the overall average salt concentration and the salt concentration in locally enriched areas, is crucial for assessing corrosion risk and determining maintenance schedules.

[0003] Existing methods for determining salt concentration on leaf surfaces have the following shortcomings: 1. Poor adaptability of sampling tools. Existing methods use a single type of sampling tool and have not designed dedicated tools for the differences in leaf size. When sampling large leaves with small swabs, the sampling efficiency is low and the salt collection is insufficient; when sampling small leaves or narrowly spaced leaves with large sponges, the operating space is limited, making it impossible to reach the narrow space between the leaves, resulting in missed samples.

[0004] 2. Insufficient control of external interference. During the sampling process, the salt from the operator's sweat can easily transfer to the leaf surface. Existing methods do not clearly specify anti-interference measures, leading to higher test results with an error of 15% to 20%.

[0005] 3. Lack of localized detection technology. Traditional localized salinity detection requires disassembling the blade or cutting the detection area, which is not only cumbersome and time-consuming (usually 24 to 48 hours), but also damages the original deposition state of the blade, resulting in detection results that cannot reflect the actual salinity distribution under real operating conditions. Some existing in-situ detection methods do not limit the detection area, and the salt easily diffuses after dissolution, leading to large errors in concentration calculation.

[0006] 4. Poor adaptability of detection sensitivity. Existing methods mostly employ a single detection technique, which is insufficient for detecting low-concentration salt samples, with relative errors reaching over ±20%, failing to meet the detection requirements under low-salt deposition conditions. Furthermore, the detection results are not clearly converted to sodium chloride content, resulting in inconsistencies with the actual deposited salt composition and poor data comparability.

[0007] Therefore, there is an urgent need to develop a salt concentration determination method that is adaptable, has strong anti-interference ability, high detection accuracy, and standardized operation. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for determining the salt concentration distribution on the surface of engine compressor blades that is adaptable, has strong anti-interference capabilities, high detection accuracy, and standardized operation.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for determining the salt concentration distribution on the surface of an engine compressor blade, comprising the following steps: Step (1): Measurement of average salt concentration: The sampling tool should be selected according to the blade size: for large blades with wide spacing, a square gauze sponge is used as the sampling tool; for small blades with narrow spacing, a degreased cotton swab fixed on a wooden rod is used as the sampling tool. First, wet the sampling tool with an organic solvent and wipe the leaf surface to remove oil; then wet the sampling tool with distilled water and wipe the leaf surface to collect salt; the operator wears powder-free rubber gloves during the sampling process; After sampling, the sampling tool is sealed in a sample bottle and sent for testing; The average salt concentration on the blade surface is calculated based on the area of ​​the compressor blades; Step (2): Local salt concentration measurement: A mask with detection holes is attached to the target area of ​​salt deposition on the blade surface, and the aperture of the detection holes is a preset size; Adjust the blade position to keep the detection surface horizontal; Add a predetermined volume of distilled water into the detection well using a syringe; Wipe the water droplet in the detection well with the test paper sleeve of the built-in indicator test paper to fully dissolve the salt. Immerse the liquid-absorbing end of the test paper sleeve into the water droplet. After the indicator test paper changes color, read the chloride ion concentration based on the length of the color change of the indicator test paper and the pre-drawn calibration curve. The local salt concentration is calculated based on the chloride ion concentration, the predetermined volume of distilled water, and the area of ​​the detection orifice.

[0010] Furthermore, in step (1), the square gauze sponge is 5 cm × 5 cm in size; the wooden rod is 15 cm long; and the degreased cotton swab is fixed to one end of the wooden rod.

[0011] Furthermore, in step (1), when sampling with the square gauze sponge, one square gauze sponge is used to remove oil stains, and two to four square gauze sponges are used to collect salt. When using the aforementioned degreased cotton swabs for sampling, one degreased cotton swab is used to remove oil stains, and two to four degreased cotton swabs are used to collect salt. After sampling, the wooden stick with a length of 2 to 3 centimeters at the end of the degreased cotton swab is cut off and sealed together with the degreased cotton swab in a sample bottle.

[0012] Furthermore, in step (1), 3 to 5 blades are selected for each stage of the compressor, and the back surface and the base surface of each blade are sampled and tested separately; the blade area is the average chord length of the blade multiplied by the blade height; the unit of the average salt concentration is milligrams per square centimeter.

[0013] Furthermore, in step (1), the organic solvent is isopropanol.

[0014] Furthermore, in step (2), the mask is electrical tape, the diameter of the detection hole is 5 mm, the predetermined volume of distilled water is 0.05 ml ± 0.002 ml, and the syringe is a high-precision syringe with a range of 0.1 ml and a graduation value of 0.001 ml.

[0015] Furthermore, in step (2), the indicator test paper is a test paper with built-in silver chromate indicator. The indicator test paper changes from brick red to light yellow after contacting chloride ions. The length of the test paper sleeve is 5 to 8 centimeters. The length of the test paper sleeve can be trimmed when testing a narrow area.

[0016] Furthermore, in step (2), the method for plotting the pre-plotted calibration curve includes: Prepare standard sodium chloride solutions with chloride ion concentrations of 0.01 mg / mL, 0.03 mg / mL, 0.05 mg / mL, 0.08 mg / mL, and 0.10 mg / mL; The test strip sleeves were used to perform colorimetric detection on standard sodium chloride solutions of various concentrations, and the length of color change of the test strips corresponding to each concentration was recorded. A calibration curve was plotted using linear regression with chloride ion concentration on the x-axis and the length of the test strip color change on the y-axis. The goodness of fit Rfit was calculated. 2 ≥0.995.

[0017] Furthermore, in step (2), the local salt concentration is calculated according to the following formula: Local salt concentration = (chloride ion concentration × distilled water volume × 58.5 / 35.5) ÷ detection well area; The area of ​​the detection hole is π × (detection hole radius). 2 .

[0018] Furthermore, the blade spacing of the large-size wide-spacing blades is greater than 2 cm; The blade spacing of the small-sized, narrow-pitch blades is no more than 2 centimeters.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are as follows: First, it has wider adaptability. Different sampling tools are designed for blades of different sizes. Square gauze sponges are used for large blades, while degreased cotton swabs with wooden rods are used for small blades with narrow spacing. It can cover various working conditions such as large, small, and narrow spacing blades, and can also be extended to salt detection in parts such as discs and bolt holes.

[0020] Secondly, it has strong anti-interference capabilities. By wearing powder-free rubber gloves, using specialized sampling tools, and following standardized operating procedures, it effectively avoids the transfer and contamination of operators' hand sweat and salt, and controls the error caused by external interference to within ±3%.

[0021] Third, it has high detection accuracy. It adopts the "mask limitation-quantitative salt dissolution-in-situ color development" technology. The detection area is limited by the mask to avoid salt diffusion. The volume of salt dissolution is precisely controlled by a high-precision syringe. The built-in silver chromate indicator paper achieves high-sensitivity detection of chloride ions. The detection limit for low-concentration samples can reach 0.001 mg / mL, and the absolute error of local salt concentration measurement is no more than ±10%.

[0022] Fourth, it is highly efficient and convenient to operate. This invention is an in-situ detection method that does not require disassembling the blades. The measurement can be completed on-site within 10 minutes. The operation procedure is standardized, and operators can master it after simple training.

[0023] Fifth, the data is reliable and comparable. This invention uses a standardized calibration curve plotting method, with a goodness of fit R... 2 A value of ≥0.995 ensures the comparability of test results from different operators; at the same time, converting chloride ion content to sodium chloride content is consistent with the actual composition of deposited salt, making the data more valuable for reference. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the method for measuring the salt concentration distribution on the surface of engine compressor blades according to the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0026] Please see Figure 1 This invention provides a method for determining the salt concentration distribution on the surface of an engine compressor blade, comprising the following steps: Step (1): Measurement of average salt concentration: The sampling tool should be selected according to the blade size: for large blades with wide spacing, a square gauze sponge is used as the sampling tool; for small blades with narrow spacing, a degreased cotton swab fixed on a wooden rod is used as the sampling tool. First, wet the sampling tool with an organic solvent and wipe the leaf surface to remove oil; then wet the sampling tool with distilled water and wipe the leaf surface to collect salt; the operator wears powder-free rubber gloves during the sampling process; After sampling, the sampling tool is sealed in a sample bottle and sent for testing; The average salt concentration on the blade surface is calculated based on the area of ​​the compressor blades; Step (2): Local salt concentration measurement: A mask with detection holes is attached to the target area of ​​salt deposition on the blade surface, and the aperture of the detection holes is a preset size; Adjust the blade position to keep the detection surface horizontal; Add a predetermined volume of distilled water into the detection well using a syringe; Wipe the water droplet in the detection well with the test paper sleeve of the built-in indicator test paper to fully dissolve the salt. Immerse the liquid-absorbing end of the test paper sleeve into the water droplet. After the indicator test paper changes color, read the chloride ion concentration based on the length of the color change of the indicator test paper and the pre-drawn calibration curve. The local salt concentration is calculated based on the chloride ion concentration, the predetermined volume of distilled water, and the area of ​​the detection orifice.

[0027] Furthermore, in step (1), the square gauze sponge is 5 cm × 5 cm in size; the wooden rod is 15 cm long; and the degreased cotton swab is fixed to one end of the wooden rod.

[0028] Furthermore, in step (1), when sampling with the square gauze sponge, one square gauze sponge is used to remove oil stains, and two to four square gauze sponges are used to collect salt. When using the aforementioned degreased cotton swabs for sampling, one degreased cotton swab is used to remove oil stains, and two to four degreased cotton swabs are used to collect salt. After sampling, the wooden stick with a length of 2 to 3 centimeters at the end of the degreased cotton swab is cut off and sealed together with the degreased cotton swab in a sample bottle.

[0029] Furthermore, in step (1), 3 to 5 blades are selected for each stage of the compressor, and the back surface and the base surface of each blade are sampled and tested separately; the blade area is the average chord length of the blade multiplied by the blade height; the unit of the average salt concentration is milligrams per square centimeter.

[0030] Furthermore, in step (1), the organic solvent is isopropanol.

[0031] Furthermore, in step (2), the mask is electrical tape, the diameter of the detection hole is 5 mm, the predetermined volume of distilled water is 0.05 ml ± 0.002 ml, and the syringe is a high-precision syringe with a range of 0.1 ml and a graduation value of 0.001 ml.

[0032] Furthermore, in step (2), the indicator test paper is a test paper with built-in silver chromate indicator. The indicator test paper changes from brick red to light yellow after contacting chloride ions. The length of the test paper sleeve is 5 to 8 centimeters. The length of the test paper sleeve can be trimmed when testing a narrow area.

[0033] Furthermore, in step (2), the method for plotting the pre-plotted calibration curve includes: Prepare standard sodium chloride solutions with chloride ion concentrations of 0.01 mg / mL, 0.03 mg / mL, 0.05 mg / mL, 0.08 mg / mL, and 0.10 mg / mL; The test strip sleeves were used to perform colorimetric detection on standard sodium chloride solutions of various concentrations, and the length of color change of the test strips corresponding to each concentration was recorded. A calibration curve was plotted using linear regression with chloride ion concentration on the x-axis and the length of the test strip color change on the y-axis. The goodness of fit Rfit was calculated. 2 ≥0.995.

[0034] Furthermore, in step (2), the local salt concentration is calculated according to the following formula: Local salt concentration = (chloride ion concentration × distilled water volume × 58.5 / 35.5) ÷ detection well area; The area of ​​the detection hole is π × (detection hole radius). 2 .

[0035] Furthermore, the blade spacing of the large-size wide-spacing blades is greater than 2 cm; The blade spacing of the small-sized, narrow-pitch blades is no more than 2 centimeters.

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be noted that all operations were carried out in an environment with a room temperature of 25 degrees Celsius and a relative humidity of 50% ± 5%.

[0037] Example 1: Salt concentration detection in large-sized leaves This embodiment focuses on the detection of salt concentration in large-sized blades (average chord length 8 cm, average blade height 20 cm).

[0038] (1) Determination of average salt concentration Step 1: Sampling. Select three large compressor blades, numbered A1, A2, and A3. Operators should wear powder-free rubber gloves. For each blade, first moisten a 5cm x 5cm square gauze sponge with isopropanol and wipe the blade surface to remove oil. Then, use two square gauze sponges moistened with distilled water to wipe the underside and base of the blade in sequence to collect salt. Place the sponges used to wipe the same blade into sample vials and seal them, numbering them S1, S2, and S3 respectively.

[0039] Step Two: Data Calculation. The leaf area is calculated by multiplying the average chord length by the leaf height and then by 2 (both the underside and leaf base), i.e., 8 cm × 20 cm × 2 = 320 square centimeters. Laboratory testing showed that the sodium chloride content of samples S1, S2, and S3 were 22.4 mg, 21.6 mg, and 23.0 mg, respectively. The average salt concentration is (22.4 + 21.6 + 23.0) ÷ 3 ÷ 320 ≈ 0.070 mg / cm².

[0040] (2) Local salt concentration measurement Step 1: Calibration Curve Plotting. Prepare standard sodium chloride solutions with chloride ion concentrations of 0.01 mg / mL, 0.03 mg / mL, 0.05 mg / mL, 0.08 mg / mL, and 0.10 mg / mL. Use test strip sleeves with built-in silver chromate indicator strips to perform colorimetric detection on each concentration of the standard solutions, recording the corresponding color change length on the test strip. Plot a calibration curve using linear regression with chloride ion concentration on the x-axis and test strip color change length on the y-axis, obtaining the regression equation y = 12.5x + 0.02, with a goodness of fit R0. 2 =0.998.

[0041] Step 2: Mask Preparation. In the area near the leading edge of a large blade where salt deposition is significant, apply electrical tape with 5mm diameter detection holes as a mask, ensuring the deposition area is exposed within the detection holes. Adjust the blade position to keep the detection surface horizontal.

[0042] Step 3: Salt Dissolution and Detection. Using a high-precision syringe with a volume of 0.1 ml and a graduation of 0.001 ml, add 0.050 ml of distilled water to the detection well. Wipe the water droplet in the detection well with the test paper sleeve containing the silver chromate indicator strip to fully dissolve the salt. Immerse the absorbent end of the test paper sleeve into the water droplet; the test paper changes from brick red to pale yellow within 30 seconds. Based on the pre-plotted calibration curve, the measured color change length of the test paper is 1.02 cm, and the chloride ion concentration is calculated to be (1.02 - 0.02) ÷ 12.5 = 0.08 mg / ml.

[0043] Step 4: Concentration Calculation. Detection well area = π × 0.25 cm × 0.25 cm ≈ 0.19635 square centimeters. Local salt concentration = (0.08 × 0.05 × 58.5 / 35.5) ÷ 0.19635 ≈ 0.0336 mg / square centimeter.

[0044] Example 2: Salt concentration detection in small-sized, narrow-spacing leaves This embodiment focuses on the detection of salt concentration in small-sized, narrow-spacing blades (average chord length 3 cm, average blade height 10 cm, blade spacing 1.5 cm).

[0045] (1) Determination of average salt concentration Step 1: Sampling. Select five small compressor blades, numbered B1, B2, B3, B4, and B5. Operators should wear powder-free rubber gloves. Attach degreased cotton swabs to one end of a 15 cm long wooden stick. First, moisten the swab with isopropanol and wipe the blade surface to remove oil. Then, use two swabs moistened with distilled water to wipe the underside and base of the blade, respectively, to collect salt. After sampling, cut off the 2 cm section of the wooden stick from the swab end and place it, along with the swabs, into sample vials and seal them. Number them T1, T2, T3, T4, and T5.

[0046] Step Two: Data Calculation. The leaf area is calculated by multiplying the average chord length by the leaf height and then by 2 (both the underside and the leaf base), i.e., 3 cm × 10 cm × 2 = 60 square centimeters. Laboratory testing showed that the sodium chloride content of samples T1, T2, T3, T4, and T5 were 3.6 mg, 3.3 mg, 3.8 mg, 3.5 mg, and 3.7 mg, respectively. The average salt concentration is (3.6 + 3.3 + 3.8 + 3.5 + 3.7) ÷ 5 ÷ 60 ≈ 0.060 mg / cm².

[0047] (2) Local salt concentration measurement Step 1: Plotting the calibration curve. The calibration curve was plotted using the same method as in Example 1. The regression equation was y = 12.5x + 0.02, and the goodness of fit Rfit was [value missing]. 2 =0.998.

[0048] Step 2: Mask Preparation. On the surface of a small blade with significant salt deposition, attach electrical tape with 5mm diameter detection holes as a mask, ensuring the deposition area is exposed within the detection holes. Adjust the blade position to keep the detection surface level.

[0049] Step 3: Salt Dissolution and Detection. Using a high-precision syringe with a volume of 0.1 ml and a graduation of 0.001 ml, add 0.049 ml of distilled water to the detection well. Wipe the water droplet in the detection well with the test paper sleeve containing the silver chromate indicator paper to fully dissolve the salt. Immerse the absorbent end of the test paper sleeve into the water droplet; the test paper changes from brick red to pale yellow within 30 seconds. Based on the pre-plotted calibration curve, the measured color change length of the test paper is 0.41 cm, and the chloride ion concentration is calculated to be (0.41 - 0.02) ÷ 12.5 = 0.0312 mg / ml.

[0050] Step 4: Concentration Calculation. Detection well area = π × 0.25 cm × 0.25 cm ≈ 0.19635 square centimeters. Local salt concentration = (0.0312 × 0.049 × 58.5 / 35.5) ÷ 0.19635 ≈ 0.0128 mg / square centimeter.

[0051] Example 3: Comparison of the dosage of different sampling tools This example illustrates the impact of different sampling tool dosages on test results.

[0052] For large-sized blades, when using square gauze sponges for sampling, one square gauze sponge is used to remove oil stains. For salt collection, comparative experiments were conducted using one, two, three, and four square gauze sponges moistened with distilled water. The results showed that using one sponge resulted in insufficient salt collection, with the detection results being approximately 15% to 20% lower than expected; using two to four sponges resulted in stable detection results with a relative deviation of less than 5%. Therefore, using two to four square gauze sponges is the optimal choice for salt collection.

[0053] For small-sized, narrow-spacing blades, when using degreased cotton swabs for sampling, one swab is used to remove oil stains. For salt collection, comparative experiments were conducted using one, two, three, and four swabs moistened with distilled water. The results showed that salt collection was insufficient when using one swab; the detection results were stable when using two to four swabs. After sampling, cutting off a 2-3 cm section of the wooden stick from the swab end and sealing it together with the swab can prevent interference from salt that may have been adsorbed on the wooden stick.

[0054] Example 4: The Influence of Detection Hole Size on Local Detection This embodiment illustrates the effect of different detection well sizes on the detection of local salt concentration.

[0055] In the same salt deposition area, local salt concentration was measured using detection wells with diameters of 3 mm, 5 mm, and 8 mm, respectively. The results showed that with a detection well diameter of 3 mm, the detection area was too small, resulting in insufficient total salt concentration, a weak detection signal, and a relatively large error. With a detection well diameter of 8 mm, the detection area was too large, potentially covering non-deposition areas and diluting the local concentration. A detection well diameter of 5 mm ensured sufficient total salt concentration for a reliable detection signal while accurately locating locally enriched areas, resulting in the best accuracy and repeatability. Therefore, a detection well diameter of 5 mm is preferred, but can be adjusted within the range of 3 to 8 mm depending on the specific circumstances.

[0056] Example 5: Effect of distilled water droplet volume on detection This example illustrates the effect of different volumes of distilled water added on the detection of local salt concentration.

[0057] Under the same detection conditions, local salt concentration was measured by adding 0.040 mL, 0.050 mL, and 0.060 mL of distilled water, respectively. The results showed that when the volume of distilled water was 0.040 mL, the water volume was insufficient to completely dissolve the salt in the detection area, leading to lower detection results. When the volume of distilled water was 0.060 mL, the solution concentration was too low, resulting in a shorter color change length on the indicator paper and decreased detection sensitivity. When the volume of distilled water was 0.050 mL ± 0.002 mL, the salt was fully dissolved and the solution concentration was moderate, resulting in the best accuracy and repeatability of the detection results. Therefore, the optimal volume of distilled water added is 0.05 mL ± 0.002 mL.

[0058] The above embodiments demonstrate that the method of the present invention is standardized in operation, has good repeatability, and high detection accuracy. It can be effectively adapted to the determination of salt concentration of blades of different sizes, providing a reliable data source for corrosion protection and maintenance of engine compressors.

[0059] In summary, this invention mainly includes the determination of average salt concentration and in-situ determination of local salt concentration. By designing sampling tools (e.g., square gauze sponges for large-sized, wide-spacing blades, and degreased cotton swabs with rods for small-sized, narrow-spacing blades) and sampling procedures, the average salt concentration of the blade is determined. Combined with the "mask limitation-quantitative salt dissolution-in-situ colorimetric" technique, rapid quantitative determination of salt concentration in locally enriched areas is achieved. This method solves the technical problems of sampling being easily interfered with by human body salt, inaccurate capture of local deposits, and insufficient sensitivity for low-concentration samples. This invention is simple to operate and has high detection accuracy (absolute error no greater than ±10%). It can simultaneously acquire overall and local salt concentration data of the blade surface, and in-situ detection can be completed without disassembling the blade, providing a basis for corrosion protection and maintenance of engine compressors. It is applicable to the detection of salt concentration in various aviation and marine engine compressor blades, rotor discs, and other related parts.

[0060] Compared with the prior art, the advantages and positive effects of the present invention are as follows: First, it has wider adaptability. Different sampling tools are designed for blades of different sizes. Square gauze sponges are used for large blades, while degreased cotton swabs with wooden rods are used for small blades with narrow spacing. It can cover various working conditions such as large, small, and narrow spacing blades, and can also be extended to salt detection in parts such as discs and bolt holes.

[0061] Secondly, it has strong anti-interference capabilities. By wearing powder-free rubber gloves, using specialized sampling tools, and following standardized operating procedures, it effectively avoids the transfer and contamination of operators' hand sweat and salt, and controls the error caused by external interference to within ±3%.

[0062] Third, it has high detection accuracy. It adopts the "mask limitation-quantitative salt dissolution-in-situ color development" technology. The detection area is limited by the mask to avoid salt diffusion. The volume of salt dissolution is precisely controlled by a high-precision syringe. The built-in silver chromate indicator paper achieves high-sensitivity detection of chloride ions. The detection limit for low-concentration samples can reach 0.001 mg / mL, and the absolute error of local salt concentration measurement is no more than ±10%.

[0063] Fourth, it is highly efficient and convenient to operate. This invention is an in-situ detection method that does not require disassembling the blades. The measurement can be completed on-site within 10 minutes. The operation procedure is standardized, and operators can master it after simple training.

[0064] Fifth, the data is reliable and comparable. This invention uses a standardized calibration curve plotting method, with a goodness of fit R... 2 A value of ≥0.995 ensures the comparability of test results from different operators; at the same time, converting chloride ion content to sodium chloride content is consistent with the actual composition of deposited salt, making the data more valuable for reference.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or equivalent variations to the disclosed technical content and apply them to other fields. However, any simple modifications, equivalent variations, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood through specific circumstances.

Claims

1. A method for determining the salt concentration distribution on the surface of an engine compressor blade, characterized in that: Includes the following steps: Step (1): Measurement of average salt concentration: The sampling tool should be selected according to the blade size: for large blades with wide spacing, a square gauze sponge is used as the sampling tool; for small blades with narrow spacing, a degreased cotton swab fixed on a wooden rod is used as the sampling tool. First, wet the sampling tool with an organic solvent and wipe the leaf surface to remove oil; then wet the sampling tool with distilled water and wipe the leaf surface to collect salt; the operator wears powder-free rubber gloves during the sampling process; After sampling, the sampling tool is sealed in a sample bottle and sent for testing; The average salt concentration on the blade surface is calculated based on the area of ​​the compressor blades; Step (2): Local salt concentration measurement: A mask with detection holes is attached to the target area of ​​salt deposition on the blade surface, and the aperture of the detection holes is a preset size; Adjust the blade position to keep the detection surface horizontal; Add a predetermined volume of distilled water into the detection well using a syringe; Wipe the water droplet in the detection well with the test paper sleeve of the built-in indicator test paper to fully dissolve the salt. Immerse the liquid-absorbing end of the test paper sleeve into the water droplet. After the indicator test paper changes color, read the chloride ion concentration based on the length of the color change of the indicator test paper and the pre-drawn calibration curve. The local salt concentration is calculated based on the chloride ion concentration, the predetermined volume of distilled water, and the area of ​​the detection orifice.

2. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (1), the square gauze sponge is 5 cm × 5 cm in size; the wooden rod is 15 cm long; and the degreased cotton swab is fixed to one end of the wooden rod.

3. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (1), when sampling with the square gauze sponge, one square gauze sponge is used to remove oil stains, and two to four square gauze sponges are used to collect salt. When using the aforementioned degreased cotton swabs for sampling, one degreased cotton swab is used to remove oil stains, and two to four degreased cotton swabs are used to collect salt. After sampling, the wooden stick with a length of 2 to 3 centimeters at the end of the degreased cotton swab is cut off and sealed together with the degreased cotton swab in a sample bottle.

4. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (1), 3 to 5 blades are selected for each stage of the compressor, and the back surface and the base surface of each blade are sampled and tested separately; the blade area is the average chord length of the blade multiplied by the blade height; the unit of the average salt concentration is milligrams per square centimeter.

5. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (1), the organic solvent is isopropanol.

6. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (2), the mask is electrical tape, the diameter of the detection hole is 5 mm, the predetermined volume of distilled water is 0.05 ml ± 0.002 ml, and the syringe is a high-precision syringe with a range of 0.1 ml and a graduation value of 0.001 ml.

7. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (2), the indicator test paper is a test paper with built-in silver chromate indicator. After the indicator test paper comes into contact with chloride ions, it changes from brick red to light yellow. The length of the test paper sleeve is 5 to 8 centimeters. When testing a narrow area, the length of the test paper sleeve can be trimmed.

8. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (2), the method for plotting the pre-plotted calibration curve includes: Prepare standard sodium chloride solutions with chloride ion concentrations of 0.01 mg / mL, 0.03 mg / mL, 0.05 mg / mL, 0.08 mg / mL, and 0.10 mg / mL; The test strip sleeves were used to perform colorimetric detection on standard sodium chloride solutions of various concentrations, and the length of color change of the test strips corresponding to each concentration was recorded. A calibration curve was plotted using linear regression with chloride ion concentration on the x-axis and the length of the test strip color change on the y-axis. The goodness of fit Rfit was calculated. 2 ≥0.

995.

9. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: In step (2), the local salt concentration is calculated according to the following formula: Local salt concentration = (chloride ion concentration × distilled water volume × 58.5 / 35.5) ÷ detection well area; The area of ​​the detection hole is π × (detection hole radius). 2 .

10. The method for determining the salt concentration distribution on the surface of an engine compressor blade according to claim 1, characterized in that: The blade spacing of the large-sized, wide-spacing blades is greater than 2 cm; The blade spacing of the small-sized, narrow-pitch blades is no more than 2 centimeters.

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