A cleaning method for stubborn carbon deposits in the fuel pipeline with complex structure of an aeroengine

Abstract

The present invention belongs to the technical field of surface treatment, and particularly relates to a cleaning method for stubborn carbon deposits in a fuel pipeline with a complex structure of an aero-engine. The technical solution of the present invention is as follows: A cleaning method for stubborn carbon deposits in a fuel pipeline with a complex structure of an aero-engine includes the following steps: First, high-temperature sintering to remove carbon deposits; Second, soaking in an oxidizing alkaline solution; Third, weak acid neutralization and cleaning; Fourth, alkaline cleaning and polishing; Fifth, weak acid neutralization and cleaning; Sixth, soaking in clear water and detecting the pH value. The cleaning method for stubborn carbon deposits in a fuel pipeline with a complex structure of an aero-engine provided by the present invention can effectively remove carbon deposits on the inner and outer surfaces of parts, does not damage the substrate, and ensures the reliability of the parts for continued use in the later stage.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment, and particularly relates to a method for cleaning stubborn carbon deposits in a fuel pipeline with a complex structure of an aeroengine. Background Art

[0002] Carbon deposits generated on high-temperature components of an aeroengine are deposits produced by incomplete combustion of fuel and lubricating oil. Their main components are hydroxy acids, asphaltenes, tar, etc. There is also an oxidation color generated by the metal matrix at high temperature at the bottom layer, and the overall composition is very complex.

[0003] Currently, the main methods for cleaning carbon deposits or oxidation colors include: surfactant cleaning, alkali solution cleaning, acid solution cleaning, etc.; cleaning processes include: dip cleaning, ultrasonic cleaning, pressure cleaning, etc. The cleaning effect of a single solution is not ideal, and the residues on the surface of the parts after acid or alkali cleaning are likely to cause corrosion of the parts, which will affect the use safety of the parts if not properly controlled. Mechanical cleaning methods use sandpaper, wire brushes, bamboo slices, sandblasting, etc. to grind and remove carbon deposits. Their efficiency is low, the cleaning quality is poor, fine scratches are easily left, the working surface of the parts is easily damaged, and there are easily dead corners, and the control of the removal size is poor. Especially when the surface quality requirements of the parts are strict, mechanical cleaning methods are not an ideal choice.

[0004] For stubborn carbon deposits in the fuel pipeline of an aeroengine with a special complex structure, since the pipeline has a coating, dip cleaning or mechanical cleaning cannot effectively remove the carbon deposits on the inner and outer surfaces. Summary of the Invention

[0005] The present invention provides a method for cleaning stubborn carbon deposits in a fuel pipeline with a complex structure of an aeroengine, which can effectively remove the carbon deposits on the inner and outer surfaces of the parts without damaging the matrix and ensure the reliability of the parts for continued use later.

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

[0007] A method for cleaning stubborn carbon deposits in a fuel pipeline with a complex structure of an aeroengine includes the following steps:

[0008] I. Removing carbon deposits by high-temperature sintering; placing the fuel pipeline in an air furnace, with the furnace temperature at 550 ± 10°C, heating for 10 min, and after taking it out, pouring out the sundries in the fuel pipeline;

[0009] II. Soaking in an oxidizing alkali solution; placing the fuel pipeline obtained in step I in an oxidizing alkali solution, where the oxidizing alkali solution is a potassium permanganate and sodium hydroxide solution, with the solution temperature at 100 ± 10°C, soaking for 60 - 120 min; then immediately placing it in water at 60 - 80°C and soaking for more than 120 min;

[0010] III. Weak acid neutralization and cleaning: Place the fuel pipeline from Step II into phosphoric acid solution and immerse it for more than 2 minutes; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure no chemical components remain in the inner cavity;

[0011] IV. Alkaline cleaning and polishing: Place the fuel pipeline from Step III into a solution of sodium gluconate and sodium hydroxide at a solution temperature of 80 - 95 °C and soak it for 30 - 60 minutes for cleaning and polishing to obtain a bright surface state;

[0012] V. Weak acid neutralization and cleaning: Place the fuel pipeline from Step IV into phosphoric acid solution and immerse it for more than 2 minutes; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure no chemical components remain in the inner cavity;

[0013] VI. Soaking in clear water and pH detection: Place the fuel pipeline from Step V into clear water and soak it for more than 2 hours; if the clear water is detected to be neutral, it is qualified.

[0014] Further, in the cleaning method for stubborn carbon deposits in the fuel pipeline with complex structure of an aeroengine, in Step II, the concentration of potassium permanganate is 170 - 210 g / L, and the concentration of sodium hydroxide is 240 - 280 g / L.

[0015] Further, in the cleaning method for stubborn carbon deposits in the fuel pipeline with complex structure of an aeroengine, in Step IV, the sodium gluconate is 60 - 120 g / L, and the concentration of sodium hydroxide is 135 - 165 g / L.

[0016] The composition of the carbon deposits in the fuel pipeline includes: 1. Deposits generated from incomplete combustion of fuel and lubricating oil are hydroxy acids and asphaltic tar, etc.; 2. The bottom layer is oxides (iron oxide, nickel oxide, aluminum oxide, chromium oxide, silicon oxide, etc.).

[0017] Removing carbon deposits by high-temperature sintering, the function of heating to a high temperature of 550 °C is as follows:

[0018] I. It can dehydrate hydroxy acids and undergo the following reactions to produce new substances:

[0019] 1. α-hydroxy acids undergo bimolecular dehydration reaction when heated, that is, cross-esterification between them to form cyclic compounds lactides;

[0020] 2. β-hydroxy acids: are prone to intramolecular dehydration to form unsaturated acids when heated;

[0021] 3. γ-hydroxy acids and δ-hydroxy acids: are prone to intramolecular dehydration to form rings (intramolecular esterification reaction) when heated, generating five-membered or six-membered cyclic lactones;

[0022] 4. Hydroxy acids with ε or higher: When heated, they are prone to lose water between multiple molecules to form long chains (linear polycondensation). Second, high-temperature heating can also decompose asphalt tar by thermal cracking, generating volatile liquid or solid hydrocarbon particles and gaseous hydrocarbon derivatives.

[0023] Potassium permanganate and sodium hydroxide solution play a chemical cleaning role through chemical reactions with different elemental oxides at the bottom layer:

[0024] 1. Fe2O3 + 2NaOH (concentrated) = 2NaFeO2 + H2O. Since sodium hydroxide is a strong base and iron oxide is a basic oxide, sodium hydroxide and iron oxide can only react when heated in a concentrated sodium hydroxide solution; nickel oxide is similar in properties to iron oxide and is also a basic oxide, and can only react with sodium oxide solution at high temperatures;

[0025] 2. Al2O3 + 2NaOH + 2H2O = 2Na[Al(OH)4] (sodium tetrahydroxyaluminate) or Al2O3 + 2NaOH = 2NaAlO2;

[0026] 3. Cr2O3 + 2NaOH (heating) = 2NaCrO2 + H2O;

[0027] 4. SiO2 + 2NaOH (heating) = Na2SiO3 + H2O;

[0028] 5. 5SiO2 + 2KMnO4 = 2MnSiO4 + K2SiO4 + 2H2SiO4 (precipitate).

[0029] The beneficial effects of the present invention are as follows: The method of the present invention can effectively remove carbon deposits on the inner and outer surfaces of parts without damaging the substrate, ensuring the reliability of the continued use of the parts in the later stage. Specific embodiments

[0030] A cleaning method for stubborn carbon deposits in a complex-structured fuel pipeline of an aero-engine, comprising the following steps:

[0031] I. Removing carbon deposits by high-temperature sintering; placing the fuel pipeline in an air furnace at a furnace temperature of 550 °C, heating for 10 min, taking it out and pouring out the sundries in the fuel pipeline; this process can be repeated 2 times;

[0032] II. Soaking in an oxidizing alkali solution; placing the fuel pipeline obtained in step I in an oxidizing alkali solution, the oxidizing alkali solution being a potassium permanganate and sodium hydroxide solution, with a potassium permanganate concentration of 190 g / L, a sodium hydroxide concentration of 260 g / L, a solution temperature of 100 °C, and soaking for 100 min; then immediately placing it in water at 60 - 80 °C and soaking for 180 min;

[0033] III. Weak acid neutralization and cleaning: Place the fuel pipeline from Step II in phosphoric acid solution and immerse it for more than 2 minutes; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure no chemical components remain in the inner cavity;

[0034] IV. Alkaline cleaning and polishing: Place the fuel pipeline from Step III in a solution of sodium gluconate and sodium hydroxide, with sodium gluconate at 80 g / L, sodium hydroxide concentration at 145 g / L, and the solution temperature at 90 °C. Immerse it for 50 minutes for cleaning and polishing to obtain a bright surface state;

[0035] V. Weak acid neutralization and cleaning: Place the fuel pipeline from Step IV in phosphoric acid solution and immerse it for more than 2 minutes; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure no chemical components remain in the inner cavity;

[0036] VI. Soaking in clear water and pH detection: Place the fuel pipeline from Step V in clear water and soak it for more than 2 hours; if the clear water is detected to be neutral, it is qualified.

Claims

1. A cleaning method for stubborn carbon deposits in the fuel pipeline with complex structure of an aero-engine, characterized in that, It includes the following steps:

1. Removing carbon deposits by high-temperature sintering: Place the fuel pipeline in an air furnace at a furnace temperature of 550 ± 10 °C, heat for 10 min, and after taking it out, pour out the sundries in the fuel pipeline; 2. Soaking in oxidizing alkaline solution: Place the fuel pipeline from step 1 in an oxidizing alkaline solution, which is a potassium permanganate and sodium hydroxide solution. The concentration of potassium permanganate is 170 - 210 g / L, the concentration of sodium hydroxide is 240 - 280 g / L, the solution temperature is 100 ± 10 °C, and soak for 60 - 120 min; then immediately place it in water at 60 - 80 °C and soak for more than 120 min; 3. Neutralizing with weak acid and cleaning: Place the fuel pipeline from step 2 in a phosphoric acid solution and impregnate for more than 2 min; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure that there is no chemical component residue in the inner cavity; 4. Alkaline washing and polishing: Place the fuel pipeline from step 3 in a sodium gluconate and sodium hydroxide solution. The sodium gluconate is 60 - 120 g / L, the concentration of sodium hydroxide is 135 - 165 g / L, the solution temperature is 80 - 95 °C, soak for 30 - 60 min, and carry out cleaning and polishing to obtain a bright surface state; 5. Neutralizing with weak acid and cleaning: Place the fuel pipeline from step 4 in a phosphoric acid solution and impregnate for more than 2 min; then clean it with a high-pressure water gun at a pressure of 0.4 MPa to ensure that there is no chemical component residue in the inner cavity; 6. Soaking in clean water and detecting pH value: Place the fuel pipeline from step 5 in clean water and soak for more than 2 h; if the detected clean water is neutral, it is qualified.