Aircraft turbine engine lubricating oil gas phase coking tendency determination system and method

Abstract

The present invention relates to the technical field of aviation turbine lubricating oil, and specifically to a system and method for determining the gas phase coking tendency of aviation turbine engine lubricating oil, wherein the system comprises a test tube; the test tube is a double-layer test tube, comprising: an inner tube and an outer tube; the inner tube is arranged in the outer tube, and there is a gap between the inner tube and the outer tube. The scheme can improve the test accuracy, thereby enhancing the repeatability and reproducibility of the gas phase coking tendency determination.

Description

Technical Field

[0001] The invention relates to the technical field of aviation turbine lubricating oil, and in particular to a system and method for determining the gas phase coking tendency of aviation turbine engine lubricating oil. Background Art

[0002] The function of aviation turbine engine lubricating oil (abbreviated as: turbine lubricating oil) is mainly used for lubrication and cooling of components in aircraft engines. Under the high temperature operating environment of the engine, the turbine lubricating oil is easily oxidized and cracked. The oxidized or cracked turbine lubricating oil will produce byproducts that seriously affect the performance of the engine, such as carbon deposits and sludge. These byproducts will hinder the normal operation of the bearings, gears, seals, oil return pumps and intake systems in the engine. In severe cases, it will also cause catastrophic failure of the engine, affecting the safe operation of the aircraft.

[0003] Although most existing aviation turbine engines are lubricated with turbine lubricating oil products based on neopentyl polyol ester as the base oil, this type of synthetic ester aviation lubricant has excellent thermal stability and antioxidant properties and can be used in a wide temperature range. Compared with synthetic diester-based lubricants, neopentyl polyol ester-based turbine lubricating oils have longer replacement cycles, lower losses, and significantly reduced sludge and carbon deposits.

[0004] However, as the demand for aviation turbine engines changes and develops, aviation turbine engines need to become lighter, more compact, but produce more power, which requires the unit "energy density" of aviation turbine engines to be increased, so as to produce greater thrust while reducing the size and weight of the engine. However, as the unit "energy density" of the engine increases, the temperature before the engine turbine will also increase significantly, causing the surface of the engine parts that the turbine oil contacts to generate higher temperatures, which will cause the currently widely used neopentyl polyol ester turbine oil to undergo high-temperature oxidation or thermal cracking reactions, generating a large amount of harmful carbon deposits or sludge.

[0005] Therefore, it is urgent to develop and produce turbine lubricants that are suitable for high-temperature operating conditions. At the same time, as a key component of aviation turbine engines, the product quality and performance parameters of lubricants are closely related to the safety of aviation turbine engine operation. Therefore, any turbine lubricant must undergo airworthiness certification to show compliance with the corresponding regulations and technical standards before it can be approved for use on civil aircraft. When verifying the airworthiness of turbine lubricants, it is necessary to measure the tendency of turbine lubricants to undergo high-temperature oxidation or thermal cracking reactions on the surfaces of hot end components such as engine ventilation pipes under high-temperature hot soaking conditions to generate harmful carbon deposits. Specifically, the China Civil Aviation Technical Standards stipulate that "Civil Aviation Engine Lubricants" (CTSO-2C704) clearly stipulates that turbine lubricants need to undergo gas phase coking tests to measure the tendency of lubricants to form carbon deposits in the high-temperature ventilation pipe area of ​​aviation turbine engines without oil infiltration.

[0006] The gas phase coking tendency characteristics of existing turbine lubricating oils are mainly measured by VPC gas phase coking tester; VPC gas phase coking tester mainly includes three-necked flask, purified air system part, heating furnace test part, insulation test tube part and control cabinet. For details, please see Figure 1 shown.

[0007] The specific test process is as follows: in a three-necked flask (such as Figure 1 Add an appropriate amount of the turbine oil sample to be tested into the test tube and use a suitable heating jacket (as shown in FIG. Figure 1 2) to heat the turbine oil sample in the three-necked flask to 204°C, and at the same time, the purified air supply subsystem (as shown in Figure 1 3) to continuously add 765±5mL / min of dry purified air into the three-necked flask, so that it becomes the medium to carry away the steam of the turbine lubricating oil sample and provides an oxidant (oxygen) for the oxidation and coking of the steam of the turbine lubricating oil sample at high temperature. The temperature of the three-necked flask is determined by the oil temperature indicating thermocouple (as shown in Figure 3) inserted under the oil level in the flask. Figure 1 The oil temperature indicating thermocouple adjusts the power of the spherical electric heating jacket according to the temperature fluctuation in the three-necked flask, thereby controlling the temperature of the three-necked flask. Then the mixed gas of the turbine lubricating oil sample steam and the dry purified air enters the heating furnace on the top of the three-necked flask (as shown in FIG. Figure 1 5), the heating furnace heats the mixed oil sample steam passing through its channel through a high-power heating coil (1200W), and also heats the test tube (such as Figure 16) to maintain it within the specified test temperature range, usually the sample temperature is 371°C. Consistent with the temperature control method of the three-necked flask, the heating furnace body also uses a thermocouple to determine the size of its temperature fluctuation, and then controls the power of the heating coil in the heating furnace to maintain a stable test temperature. The mixed gas of the turbine lubricating oil sample steam and dry purified air enters the test tube embedded in the heating furnace body after being heated by the heating furnace. The bottom of the test tube is firmly locked in the heating furnace by a fastening nut, and the test temperature of about 371°C is maintained by the heating furnace.

[0008] At the same time, six thermocouples are installed on the test tube at equal distances from the bottom to the top to monitor and record the temperature changes at different positions on the stainless steel test tube. This is because only a small part of the bottom tube (about 1 cm) of the stainless steel test tube is inserted into the heating furnace. Since the rest of the stainless steel test tube is far away from the heating furnace, there is a temperature gradient along the axial direction of the stainless steel test tube, resulting in a high temperature near the port of the heating furnace and a low temperature at the port far away from the heating furnace. When the turbine lubricating oil test steam passes through the test tube, as the temperature of the test tube continues to decrease, when the lubricating oil steam cools to a certain temperature, the lubricating oil steam will condense into liquid and flow back down along the inner wall of the test tube until it flows back to a specific temperature. Under the action of high temperature and oxygen in the air, the lubricating oil gradually forms sludge and carbon deposits on the inner wall of the test tube. At this time, the temperature of the lubricating oil steam coke is measured through the six thermocouples on the outer surface of the test tube and the position of the sludge and carbon deposits formed in the tube.

[0009] When all control parameters of the gas phase coking tester are stable, the 18-hour test begins.

[0010] The inventors conducted a large number of tests on the self-built gas phase coking tendency test bench and found that the existing VPC gas phase coking tester had a lot of problems:

[0011] 1. The test tube specified in foreign standards is a single-layer cylindrical tube with a diameter of 12.7 mm. The heat loss of the single-layer test tube is fast and is easily affected by the ambient temperature conditions;

[0012] 2. The thermocouple on the outside of the single-layer test tube specified in foreign standards is installed with a metal clamp, and the thermocouple wire tube is welded to the outside of the clamp, which increases the outer diameter of the single-layer test tube assembly to more than 30mm. At the same time, in order to prevent the thermocouple metal wire from contacting the inner wall of the insulation sleeve, increase measurement accuracy, and prevent the thermocouple metal wire from abrasion, the inner diameter of the insulation sleeve will be increased to at least 40mm, resulting in a large gap between the inner wall of the insulation sleeve and the single-layer test tube, which is easily affected by ambient temperature conditions, causing a large amount of heat loss in the single-layer test tube, resulting in an uneven temperature distribution gradient along the axial direction of the single-layer test tube, which seriously affects the test repeatability and reproducibility;

[0013] 3. The single-layer cylindrical shape with a diameter of 12.7 mm does not conform to the double-layer flat elliptical cylindrical structure of the domestic aviation turbine engine ventilation pipe, and its simulation authenticity is low;

[0014] 4. The inventors found through a large number of tests that the coking temperature range of standard aviation turbine lubricants inside the test tube is mostly concentrated between 170°C and 270°C, and that of high-performance aviation turbine lubricants is mainly concentrated between 190°C and 240°C. However, there are only 6 thermocouples on the test tube of the existing VPC gas phase coking tendency tester, and they are evenly distributed from the bottom to the top of the test tube, which limits the coking temperature range of different types of aviation turbine lubricants to be measured, and it is impossible to accurately measure the gas phase coking temperature range of different aviation turbine lubricants, affecting the test accuracy;

[0015] 5. The heating temperature of the three-necked flask is 204°C, which cannot adapt well to the hot soaking temperature of the high-temperature bearing cavity of low-power and high-power domestic aviation turbine engines, making the simulation less realistic;

[0016] The above problems will directly or indirectly lead to large differences in key parameters such as the quality of gas phase coking deposits, the temperature distribution of carbon deposits and paint films formed in the test tube, and the maximum generation temperature of carbon deposits in multiple tests of the same turbine lubricant, which seriously affects the accuracy of the determination of the gas phase coking tendency of turbine lubricants, resulting in low repeatability and reproducibility of the determination of the gas phase coking tendency of turbine lubricants, and the inability to guarantee the accuracy of the determination of the gas phase coking tendency of turbine lubricants, so that it is impossible to obtain accurate gas phase coking characteristics of turbine lubricants, making the referenceability of the determination results low. The development of existing domestic turbine lubricants cannot refer to the determination results of the gas phase coking tendency of turbine lubricants to design turbine lubricants, which greatly hinders the development and production of domestic turbine lubricants and restricts the airworthiness certification of my country's turbine lubricants; at the same time, it also makes it impossible for the development of existing domestic engines to accurately design the size, material and configuration of the engine high-temperature bearing cavity ventilation duct according to the gas phase coking characteristics of lubricants, which greatly restricts the development of domestic engines.

[0017] Therefore, there is an urgent need for a system for measuring the gas phase coking tendency of aviation turbine engine lubricating oil that can improve the test accuracy. Summary of the invention

[0018] One of the purposes of the present invention is to provide a system for determining the gas phase coking tendency of aviation turbine engine lubricating oil, which can improve the test accuracy and thus enhance the repeatability and reproducibility of the gas phase coking tendency determination.

[0019] The present invention provides a basic solution 1: a system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, comprising a test tube;

[0020] The test tube is a double-layer test tube, comprising: an inner tube and an outer tube;

[0021] The inner tube is arranged inside the outer tube, and there is a gap between the inner tube and the outer tube.

[0022] Beneficial effects of Basic Scheme 1: The test tube in the aviation turbine engine lubricating oil gas phase coking tendency determination system is a double-layer test tube, the inner tube is arranged in the outer tube, and there is a gap between the inner tube and the outer tube. When the temperature rises, the air layer in the gap can help the inner tube to insulate and prevent the inner tube from losing heat quickly. At the same time, it slows down the direct impact of the ambient temperature outside the test tube on the steam in the test tube, enhances the thermal insulation effect of the test tube, and improves the test accuracy. As a result, the differences in key parameters such as the mass of gas phase coking deposits, the temperature distribution of carbon deposits and paint films formed in the test tube, and the maximum generation temperature of carbon deposits in multiple tests on the same turbine lubricating oil will also be reduced, thereby enhancing the repeatability and reproducibility of the gas phase coking tendency determination, ensuring the accuracy of the turbine lubricating oil gas phase coking determination, thereby obtaining accurate turbine lubricating oil gas phase coking characteristics, and improving the reference value of the determination results. The development of existing domestically produced turbine lubricants can refer to the test results of the gas phase coking tendency of turbine lubricants to design turbine lubricants and promote the development and production of domestically produced turbine lubricants; at the same time, the development of existing domestically produced engines can be modeled and parameter adjusted according to the gas phase coking characteristics of turbine lubricants. For example, after determining to use a specific domestically produced turbine lubricant, the size, material and configuration of the engine high-temperature bearing cavity ventilation pipe can be accurately designed according to the test results of the gas phase coking tendency of domestically produced turbine lubricants to ensure that the performance of domestically produced engines is optimal when using the selected domestically produced turbine lubricants, thereby improving the forward design capabilities of my country's aviation engines. Further, the inner tube and the outer tube are both flat elliptical cylindrical tubes.

[0023] Beneficial effect: Both the inner tube and the outer tube are flat elliptical cylindrical tubes, which conform to the double-layer flat elliptical cylindrical structure of the ventilation tube of the domestic aviation turbofan engine, improve the authenticity of the simulation, and thus improve the accuracy of the measurement.

[0024] Furthermore, the test tube further comprises: a pipe joint;

[0025] One end of the pipe joint is a flat elliptical cylindrical pipe joint, and the other end is a cylindrical pipe joint;

[0026] The flat oval cylindrical pipe joint is used to connect the inner pipe and the outer pipe, and the cylindrical pipe joint is used for the installation of the test pipe.

[0027] Beneficial effects: The pipe joint can transform a flat elliptical cylinder into a conventional cylinder, so that the inner tube and the outer tube can be connected with the metal tube in the heating furnace or the pipe fittings of other devices.

[0028] Furthermore, a thermal insulation sleeve is arranged outside the test tube.

[0029] Beneficial effect: A thermal insulation sleeve is arranged outside the test tube. Compared with the prior art, there is a larger gap between the inner wall of the thermal insulation sleeve and the single-layer test tube. The thermal insulation sleeve covers the test tube, which reduces the heat loss of the test tube and reduces the impact of ambient temperature conditions.

[0030] Furthermore, the test tube is provided with 10 thermocouples from the bottom to the top, for monitoring the temperature changes at different positions on the test tube.

[0031] Beneficial effect: 10 thermocouples are set on the test tube to more accurately measure the temperature distribution of carbon deposits and the maximum generation temperature of carbon deposits of different types of turbine lubricating oils. Furthermore, the wire of the thermocouple adopts a flexible thermocouple wire with a diameter less than or equal to a preset diameter, and is connected to the inner tube by welding.

[0032] Beneficial effect: The conductor of the thermocouple adopts a flexible thermocouple wire with a diameter less than or equal to a preset diameter. The preset diameter is set according to demand. The preset diameter is generally a small diameter, because the flexible thermocouple wire with a small diameter requires a small space and is connected to the inner tube by welding, which greatly reduces the gap between the inner tube and the outer tube. While the air layer in the gap plays a certain degree of thermal insulation role, it prevents heat loss caused by excessive gap, further reducing heat loss in the test tube.

[0033] Further, it also includes: a three-necked flask, a heating jacket, a purified air supply subsystem, a heating furnace, and a control subsystem;

[0034] The three-necked flask is provided with an oil temperature indicating thermocouple for monitoring the temperature change of the turbine lubricating oil in the three-necked flask. The oil temperature indicating thermocouple is connected to the control subsystem through the neck opening on one side of the three-necked flask, the neck opening on the other side of the three-necked flask is connected to the purified air supply subsystem, and the neck opening in the middle is connected to the heating furnace;

[0035] The test tube is longitudinally arranged in the heating furnace and communicated with the neck opening in the middle; the thermocouple is connected to the control subsystem;

[0036] The three-necked flask is used to hold turbine lubricating oil;

[0037] The heating jacket is used to heat the three-necked flask, and the temperature is set to 220° C. during heating; the heating jacket is connected to the control subsystem;

[0038] The purified air supply subsystem is used to add air into the three-necked flask;

[0039] The heating furnace is used to heat the test tube, wherein the heating temperature includes: one or more of 288°C, 325°C, 343°C, 371°C, 399°C and 412°C; the heating furnace is connected to the control subsystem;

[0040] The control subsystem is used for data collection and processing of the heating jacket, the heating furnace, the thermocouple and the oil temperature indicating thermocouple, and adjusts the heating temperature of the heating jacket and the heating furnace according to the collected data.

[0041] Beneficial effects: According to the actual heat soak temperature of the high-temperature bearing cavity after shutdown of different domestic civil and military aviation turbofan engines, the heating temperature of the heating sleeve in this scheme is 220℃, and two heating furnace temperatures of 288℃ and 412℃ are added on the basis of the original standard range, which can better adapt to the heat soak temperature of the high-temperature bearing cavity of low-power and high-power domestic engines respectively, and increase the authenticity of the simulation.

[0042] The second object of the present invention is to provide a method for determining the gas phase coking tendency of aviation turbine engine lubricating oil, which can improve the test accuracy and thus enhance the repeatability and reproducibility of the gas phase coking tendency determination.

[0043] The present invention provides a second basic solution: a method for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, using the above-mentioned system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, comprising the following contents:

[0044] Initial data measurement steps: obtaining the 40°C kinematic viscosity, total acid value, initial weight of the test tube and initial weight of the three-necked flask containing the turbine lubricating oil to be tested;

[0045] Test steps: Test the turbine lubricating oil for a preset time at several preset heating furnace heating temperatures one by one using the aviation turbine engine lubricating oil gas phase coking tendency determination system;

[0046] Final data measurement steps: obtain the 40°C kinematic viscosity, total acid value, final weight of the test tube and final weight of the three-necked flask containing the tested turbine lubricant;

[0047] Data analysis steps: Obtain the weight of the coke based on the initial weight and final weight of the test tube; Obtain the consumption of the turbine lubricating oil based on the initial weight and final weight of the three-necked flask; Obtain the change in kinematic viscosity and total acid value based on the comparison results of the 40°C kinematic viscosity and total acid value of the turbine lubricating oil to be tested and the 40°C kinematic viscosity and total acid value of the turbine lubricating oil after the test.

[0048] Beneficial effects of Basic Scheme 2: This method adopts the above-mentioned aviation turbine engine lubricating oil gas phase coking tendency determination system, and the test tube in the system is a double-layer test tube, and the inner tube is arranged in the outer tube, and there is a gap between the inner tube and the outer tube. When the temperature rises, the air layer in the gap can help the inner tube to insulate and prevent the inner tube from losing heat quickly. The thermocouple wire adopts a flexible thermocouple wire with a diameter less than or equal to a preset diameter. The preset diameter is set according to demand. The preset diameter generally selects a small diameter because a small diameter flexible thermocouple wire requires a small space and is connected to the inner tube by welding, which greatly reduces the gap between the inner tube and the outer tube. , so that the air layer in the gap can play a certain degree of heat insulation role while preventing heat loss caused by excessive gaps, further reducing the heat loss in the test tube, and at the same time slowing down the direct impact of the ambient temperature outside the test tube on the steam in the test tube, enhancing the thermal insulation effect of the test tube, and improving the test accuracy. As a result, the differences in the weight of coke, consumption of turbine lubricating oil, kinematic viscosity and total acid value change obtained from multiple experiments on the same turbine lubricating oil are reduced, thereby enhancing the repeatability and reproducibility of the gas phase coking tendency determination, ensuring the accuracy of the turbine lubricating oil gas phase coking determination, thereby obtaining accurate turbine lubricating oil gas phase coking characteristics, and improving the reference value of the determination results. The development of existing domestic turbine lubricants can refer to the test results of turbine lubricants' gas phase coking tendency to design turbine lubricants and promote the development and production of domestic turbine lubricants. At the same time, the development of existing domestic engines can carry out model design and parameter adjustment according to the gas phase coking characteristics of the lubricants. For example: after determining to use a specific domestic turbine lubricant, the size, material and configuration of the engine's high-temperature bearing cavity ventilation pipe can be accurately designed based on the test results of the gas phase coking tendency of the domestic turbine lubricant, ensuring that the domestic engine has optimal performance when using the selected domestic turbine lubricant, thereby enhancing the forward design capability of my country's aviation engines.

[0049] Further, the test steps include:

[0050] Connecting various components in the aviation turbine engine lubricating oil gas phase coking tendency determination system;

[0051] At a plurality of preset heating furnace temperatures, the heating jacket heats the three-necked flask, the heating furnace heats the test tube, the purified air system adds air into the three-necked flask, and during the heating process, the control subsystem adjusts the heating jacket and the heating furnace's heating temperatures according to the thermocouple data and its first preset temperature value and the oil temperature indicating thermocouple data and its second preset temperature value;

[0052] After all the preset heating furnaces have completed the test at the preset heating temperature for the preset time, stop heating and cool down;

[0053] After cooling, the components in the aviation turbine engine lubricating oil gas phase coking tendency determination system are disassembled;

[0054] Dry the test tube.

[0055] Beneficial effect: During the test, the heating temperature of the heating jacket and the heating furnace is maintained stable through the thermocouple and the oil temperature indicating thermocouple.

[0056] Further, the second preset temperature value is 220°C;

[0057] The preset heating furnace heating temperature includes one or more of 288°C, 325°C, 343°C, 371°C, 399°C and 412°C.

[0058] Beneficial effect: According to the actual hot-dip temperature of the high-temperature bearing cavity after shutdown of different domestic civil and military aviation turbofan engines, the heating temperature of the heating sleeve in this scheme, that is, the second preset temperature value is 220℃, and two heating furnace temperatures of 288℃ and 412℃ are added on the basis of the original standard range, which can better adapt to the hot-dip temperature of the high-temperature bearing cavity of low-power and high-power domestic engines respectively, and increase the authenticity of the simulation.

[0059] Further, the weight of the coke is M3=M2-M1, wherein M1 is the initial weight of the test tube; M2 is the final weight of the test tube;

[0060] The consumption of the turbine lubricating oil m5=m4-m3, wherein m3 is the initial weight of the three-necked flask containing the turbine lubricating oil to be tested; m4 is the final weight of the three-necked flask containing the turbine lubricating oil after the test;

[0061] The kinematic viscosity change rate % = [(V2-V1) / V1] × 100%, where V1 is the kinematic viscosity of the turbine lubricating oil at 40°C, mm 2 / s; V2 is the kinematic viscosity of the turbine oil at 40°C after the test, mm 2 / s;

[0062] The total acid value change value = TAN2 - TAN1, wherein TAN1 is the total acid value of the turbine lubricating oil to be tested, mgKOH / g; TAN2 is the total acid value of the turbine lubricating oil after the test, mgKOH / g.

[0063] Beneficial effects: The above method can accurately calculate the weight, consumption, kinematic viscosity change rate and total acid value change of the coking material. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a structural schematic diagram of a VPC gas phase coking tester of the prior art;

[0065] Figure 2It is a schematic diagram of the structure of the inner tube in the embodiment of the system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine of the present invention;

[0066] Figure 3 It is a front view of the inner layer tube in the embodiment of the system for determining the gas phase coking tendency of the aviation turbine engine lubricating oil of the present invention;

[0067] Figure 4 It is a schematic diagram of the structure of a pipe joint in an embodiment of the system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine of the present invention. DETAILED DESCRIPTION

[0068] The following is further described in detail through specific implementation methods:

[0069] The reference numerals in the drawings of the specification include: three-necked flask 1, heating jacket 2, purified air supply subsystem 3, oil temperature indicating thermocouple 4, heating furnace 5, test tube 6, flat elliptical cylindrical pipe joint 7, cylindrical pipe joint 8.

[0070] Embodiment 1

[0071] This embodiment provides a system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, comprising a test tube 6, a three-necked flask 1, a heating jacket 2, a purified air supply subsystem 3, a heating furnace 5 and a control subsystem;

[0072] The test tube 6 comprises an inner tube, an outer tube and a tube joint;

[0073] The inner tube is arranged in the outer tube, and there is a gap between the inner tube and the outer tube, and both the inner tube and the outer tube are flat elliptical cylindrical tubes; one end of the pipe joint is a flat elliptical cylindrical pipe joint 7, and the other end is a cylindrical pipe joint 8; the flat elliptical cylindrical pipe joint 7 is used to connect the inner tube and the outer tube, and the cylindrical pipe joint 8 is used for the installation of the test tube 6;

[0074] Specifically, the material of the test tube 6 is MAS7101 standard GH625 steel;

[0075] The inner tube shape is Figure 2 , Figure 3 As shown, it is a flat elliptical cylindrical tube, which is welded by two semicircular tubes and two flat plates, with a surface roughness range of 2.0-5.0, a long end range of 20-50, and a round surface profile range of 0.1-0.4; the upper and lower sides are two semicircular tubes, with an outer diameter range of 15-20mm, a thickness range of 0.5-2.0mm, and a length range of 100-200mm; the length range of the flat plate is 100-200mm, the thickness range is 0.5-2.0mm, and the width range is 10-25mm;

[0076] The outer tube has the same shape as the inner tube, which is a flat elliptical cylindrical tube, welded by two semicircular tubes and two flat plates, with a surface roughness range of 2.0-5.0, a long end range of 20-55, and a round surface profile range of 0.1-0.4; the upper and lower sides are two semicircular tubes, with an outer diameter range of 18-30mm, a thickness range of 0.5-2.0mm, and a length range of 150-250mm; the length range of the flat plate is 150-250mm, the thickness range is 0.5-2.0mm, and the width range is 10-25mm;

[0077] Pipe fittings such as Figure 4 As shown, the size of the inner layer tube can be converted into a cylindrical pipe joint with a length range of 18-30mm, an outer diameter range of 8-20mm, and a thickness range of 0.8-2.0mm; the maximum cross-sectional length and width of the pipe joint are both less than 50mm;

[0078] The total length of the inner tube and the tube joint is in the range of 150-250 mm, and the total length of the outer tube is in the range of 150-250 mm.

[0079] The test tube 6 is provided with a plurality of thermocouples from the bottom to the top, for monitoring the temperature changes at different positions on the test tube 6. In this embodiment, the number of thermocouples is 10, and the specific positions are shown in Table 1 below:

[0080] Table 1: Installation parameters of thermocouples on test tube 6

[0081]

[0082] Among them, the 1#, 3#, 5# and 7# thermocouples are newly added thermocouples compared to the six thermocouples provided in the prior art, and all the thermocouples are connected to the control subsystem.

[0083] The wire of the thermocouple adopts a flexible thermocouple wire with a diameter less than or equal to the preset diameter, and is connected to the inner tube by welding. The wire of the thermocouple adopts a flexible thermocouple wire with a diameter less than or equal to the preset diameter. The preset diameter is set according to demand. The preset diameter generally selects a small diameter, because the flexible thermocouple wire with a small diameter requires a small space, and is connected to the inner tube by welding, which greatly reduces the gap between the inner tube and the outer tube, so that the air layer in the gap plays a certain degree of heat insulation while preventing the gap from being too large to cause heat loss, and the insulation sleeve can cover the test tube, further reducing the heat loss in the test tube, and also preventing the thermocouple wire from being worn. In this embodiment, the preset diameter is less than or equal to 1mm.

[0084] An oil temperature indicating thermocouple 4 is arranged in the three-necked flask 1, and is used to monitor the temperature change of the turbine lubricating oil in the three-necked flask 1. The oil temperature indicating thermocouple 4 is connected to the control subsystem through the neck opening on one side of the three-necked flask 1. Specifically, the oil temperature indicating thermocouple 4 is installed into the thermocouple adapter, and the black plastic fixing nut on the top of the thermocouple adapter is tightened, and then the assembled thermocouple adapter is inserted into the neck opening of the three-necked flask 1, so that the outer wall and the neck opening are tightly sealed, and the oil temperature indicating thermocouple 4 is located in the middle of the three-necked flask 1, wherein the thermocouple adapter adopts a frosted glass adapter; the thermocouple and the oil temperature indicating thermocouple 4 of this embodiment both adopt J-type thermocouples, 304-type stainless steel shells, ungrounded, and double connectors;

[0085] The neck opening on the other side of the three-necked flask 1 is connected to the purified air supply subsystem 3. Specifically, the neck opening on the other side of the three-necked flask 1 is connected to the purified air supply subsystem 3 through an air inlet pipe, a PTFE sealing diaphragm is inserted into the conical ground mouth of the air inlet pipe, and the air inlet pipe is inserted into the neck opening. When inserted, it is rotated downward and left and right to make the air inlet pipe in close contact with the neck opening;

[0086] The neck opening in the middle of the three-necked flask 1 is connected to the heating furnace 5; specifically, the metal tube below the heating furnace 5 is inserted into the neck opening in the middle of the three-necked flask 1 through the adapter, and the adapter and the end of the metal tube are in close contact;

[0087] The test tube 6 is coated with a heat-insulating layer, and is disposed longitudinally in the heating furnace 5 and is connected to the neck opening in the middle of the three-necked flask 1; specifically, the test tube 6 is disposed longitudinally in the heating furnace 5, with the pipe joint facing downward, and a cylindrical pipe joint 8 of the pipe joint is inserted into a metal pipe of the heating furnace 5 and fixedly connected;

[0088] A three-necked flask 1 is used to hold turbine lubricating oil; in this embodiment, the capacity of the three-necked flask 1 is 2000 mL;

[0089] The heating jacket 2 is used to heat the three-necked flask 1, and the temperature is set to 220°C during heating; the heating jacket 2 is connected to the control subsystem; in this embodiment, the heating jacket 2 adopts a spherical temperature bag stand, which can support the three-necked flask 1;

[0090] The purified air supply subsystem 3 is used to add air to the three-necked flask 1; specifically, when the purified air supply subsystem 3 injects air into the turbine lubricating oil in the three-necked flask 1, the air flow rate is controlled at 765±5mL / min by a rotor flowmeter and a mass flow controller; in order to ensure drying, an air gas purifier is also used;

[0091] The heating furnace 5 is used to heat the test tube 6, wherein the heating temperature includes one or more of 288°C, 325°C, 343°C, 371°C, 399°C and 412°C; the heating furnace 5 is connected to the control subsystem; the heater coils in the heating furnace 5 are 220 volts and 1200 watts respectively;

[0092] The control subsystem is used for data collection and processing of the heating jacket 2, the heating furnace 5, the thermocouple and the oil temperature indicating thermocouple 4, and adjusts the heating temperature of the heating jacket 2 and the heating furnace 5 according to the collected data; specifically, the control subsystem includes:

[0093] Data acquisition controller, used to read J-type thermocouple, with a sensitivity of 1°C and can be used continuously for more than 20 hours;

[0094] Heating jacket controller, used to design time variable, heating and constant temperature controller, single loop, input J-type thermocouple, output relay or contact, can be accurately controlled within 1℃;

[0095] Heating furnace controller, used for designing time, heating and constant temperature controller, single loop, input J-type thermocouple, output relay or contact, can be accurately controlled within 1℃;

[0096] A heating jacket power controller, comprising: a silicon controlled rectifier (SCR), for receiving an input from a heating jacket 2 controller;

[0097] The heating furnace power controller is used to receive the input of the heating furnace 5 controller.

[0098] Embodiment 2

[0099] This embodiment is basically as shown in the accompanying drawings: a method for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, using the above-mentioned system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine, includes the following contents:

[0100] Equipment preparation steps: Clean all components in the aviation turbine engine lubricating oil gas phase coking tendency determination system;

[0101] Initial data measurement steps: obtaining the 40°C kinematic viscosity, total acid value, initial weight of the test tube 6 and initial weight of the three-necked flask 1 containing the turbine lubricant to be tested of the turbine lubricant to be tested; specifically, the 40°C kinematic viscosity and total acid value of the turbine lubricant to be tested of the first preset weight are measured using GB / T 265 and GB / T 7304 methods respectively; the turbine lubricant to be tested of the second preset weight is added to the three-necked flask 1, and the initial weight of the test tube 6 and the initial weight of the three-necked flask 1 containing the turbine lubricant to be tested are weighed using an analytical balance, with the accuracy being 0.1 mg and 0.1 g respectively;

[0102] Test steps: at a plurality of preset heating furnace 5 heating temperatures, the turbine lubricating oil is tested for a preset time using the aviation turbine engine lubricating oil gas phase coking tendency determination system; specifically,

[0103] Connecting various components in the aviation turbine engine lubricating oil gas phase coking tendency determination system;

[0104] At several preset heating temperatures of the heating furnace 5, the heating jacket 2 heats the three-necked flask 1, the heating furnace 5 heats the test tube 6, the purified air system adds air into the three-necked flask 1, and during the heating process, the control subsystem adjusts the heating temperature of the heating jacket 2 and the heating furnace 5 according to the data of the thermocouple and its first preset temperature value and the data of the oil temperature indicating thermocouple 4 and its second preset temperature value; in this embodiment, the second preset temperature value is 220°C;

[0105] The preset heating temperature of the heating furnace 5 includes one or more of 288°C, 325°C, 343°C, 371°C, 399°C and 412°C;

[0106] After all the preset heating furnaces 5 have completed the preset heating time, the heating is stopped and the cooling is performed; in this embodiment, the preset heating time of each preset heating furnace 5 is 6 hours;

[0107] After cooling, the components in the aviation turbine engine lubricating oil gas phase coking tendency determination system are disassembled; when disassembling the three-necked flask 1, the air intake pipe is carefully removed to allow the turbine lubricating oil in the air intake pipe to fully flow back to the three-necked flask 1, and then the oil temperature indicating thermocouple 4 is removed to allow the test oil attached to the oil temperature indicating thermocouple 4 to fully flow back to the three-necked flask 1;

[0108] Dry the test tube 6; specifically, immerse the test tube 6 in petroleum ether for at least 30 minutes, then place the test tube 6 in an oven and dry it at 100° C. for at least 30 minutes. After drying, place the insulated test tube 6 in an airtight storage tube, and then place the airtight storage tank in a drying oven to allow the test tube 6 to naturally cool to room temperature;

[0109] Final data measurement step: obtaining the 40°C kinematic viscosity, total acid value, final weight of the test tube 6 and final weight of the three-necked flask 1 containing the tested turbine lubricant; the same method as the initial data measurement step is used to obtain the data, which will not be repeated in this embodiment;

[0110] Data analysis steps: according to the initial weight and final weight of the test tube 6, the weight of the coke is obtained; according to the initial weight and final weight of the three-necked flask 1, the consumption of the turbine lubricating oil is obtained; according to the comparison results of the 40°C kinematic viscosity and the total acid value of the turbine lubricating oil to be tested and the 40°C kinematic viscosity and the total acid value of the turbine lubricating oil after the test, the change values ​​of the kinematic viscosity and the total acid value are obtained; specifically, the weight of the coke M3 = M2-M1, wherein M1 is the initial weight of the test tube 6; M2 is the final weight of the test tube 6;

[0111] The consumption of the turbine lubricating oil m5=m4-m3, wherein m3 is the initial weight of the three-necked flask 1 containing the turbine lubricating oil to be tested; m4 is the final weight of the three-necked flask 1 containing the turbine lubricating oil after the test;

[0112] The kinematic viscosity change rate % = [(V2-V1) / V1] × 100%, where V1 is the kinematic viscosity of the turbine lubricating oil at 40°C, mm 2 / s; V2 is the kinematic viscosity of the turbine oil at 40°C after the test, mm 2 / s;

[0113] The total acid value change value = TAN2 - TAN1, wherein TAN1 is the total acid value of the turbine lubricating oil to be tested, mgKOH / g; TAN2 is the total acid value of the turbine lubricating oil after the test, mgKOH / g.

[0114] Specifically, the experimental results of the experiments conducted using the prior art method and the present solution are as follows: Table 2 Test results of test tube 6 using the original standard requirements

[0115]

[0116] Note: All the above tests were completed at 204℃ turbine oil temperature, 371℃ test tube 6 heating furnace 5 temperature, 765mL / min air flow, and 18h ​​test time. Table 3 Test results using modified test tube 6

[0117]

[0118] Note: All the above tests were completed at 204℃ turbine lubricating oil temperature, 371℃ test tube 6 heating furnace 5 temperature, 765mL / min air flow rate, and 18h ​​test time.

[0119] It can be clearly seen from Tables 2 and 3 that the differences in the weight of coke, consumption of turbine lubricating oil, kinematic viscosity and change in total acid value obtained by multiple experiments on the same turbine lubricating oil are smaller than those in the prior art, and the range of determination for standard aviation turbine lubricating oil and high-performance aviation turbine lubricating oil is more accurate, so this scheme can improve the test accuracy, thereby enhancing the repeatability and reproducibility of the determination of gas phase coking tendency.

[0120] The improvement of repeatability and reproducibility, combined with the fact that the shape of the test tube in the turbine lubricant gas phase coking tendency determination system adopted conforms to the double-layer flat elliptical cylindrical structure of the ventilation pipe of the domestic aviation turbofan engine, and the temperature gradient distribution of carbon deposits and paint films formed in the test tube is uniform, ensures the accuracy of the determination of turbine lubricant gas phase coking, thereby obtaining accurate turbine lubricant gas phase coking characteristics, making the reference value of the determination results improved.

[0121] The research and development of existing domestically produced turbine lubricants can refer to the test results of the gas phase coking tendency of turbine lubricants to design turbine lubricants, promote the research and development of domestically produced turbine lubricants, and make the developed domestically produced turbine lubricants more suitable for domestically produced engines;

[0122] At the same time, the development of existing domestic engines can be modeled and parameter adjusted according to the gas phase coking characteristics of turbine lubricants. For example, after clarifying the gas phase coking characteristics of various domestic turbine lubricants, domestic turbine lubricants can be selected according to demand, and according to the gas phase coking tendency measurement results of domestic turbine lubricants, the size, material and configuration of the engine high temperature bearing cavity ventilation pipe can be accurately designed to ensure that the performance of domestic engines is optimal when using the selected domestic turbine lubricants, thereby improving the forward design capability of my country's aviation engines. The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described too much here. Ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A system for determining the gas phase coking tendency of aviation turbine engine lubricating oil, comprising a test tube, characterized in that: The test tube is a double-layer test tube, comprising: an inner tube, an outer tube and a tube joint; The inner tube is arranged inside the outer tube, and there is a gap between the inner tube and the outer tube; The inner tube and the outer tube are both flat elliptical cylindrical tubes; One end of the pipe joint is a flat elliptical cylindrical pipe joint, and the other end is a cylindrical pipe joint; The flat oval cylindrical pipe joint is used to connect the inner pipe and the outer pipe, and the cylindrical pipe joint is used for the installation of the test pipe; The test tube is provided with 10 thermocouples from the bottom to the top, which are used to monitor the temperature changes at different positions on the test tube. The wires of the thermocouples are flexible thermocouple wires with a diameter less than or equal to a preset diameter, and are connected to the inner tube by welding. It also includes: a three-necked flask, a heating jacket, a purified air supply subsystem, a heating furnace, and a control subsystem; The three-necked flask is provided with an oil temperature indicating thermocouple for monitoring the temperature change of the turbine lubricating oil in the three-necked flask. The oil temperature indicating thermocouple is connected to the control subsystem through the neck opening on one side of the three-necked flask, the neck opening on the other side of the three-necked flask is connected to the purified air supply subsystem, and the neck opening in the middle is connected to the heating furnace; The test tube is longitudinally arranged in the heating furnace and communicated with the neck opening in the middle; the thermocouple is connected to the control subsystem; The three-necked flask is used to hold turbine lubricating oil; The heating jacket is used to heat the three-necked flask; the heating jacket is connected to the control subsystem; The purified air supply subsystem is used to add air into the three-necked flask; The heating furnace is used to heat the test tube; the heating furnace is connected to the control subsystem; The control subsystem is used for data collection and processing of the heating jacket, the heating furnace, the thermocouple and the oil temperature indicating thermocouple, and adjusts the heating temperature of the heating jacket and the heating furnace according to the collected data.

2. The system for measuring the gas phase coking tendency of aviation turbine engine lubricating oil according to claim 1, characterized in that: A heat-insulating sleeve is arranged outside the test tube.

3. The system for determining the gas phase coking tendency of lubricating oil for aviation turbine engines according to claim 1, characterized in that: The heating jacket is set at a temperature of 220°C during heating; The heating furnace heats the test tube, wherein the heating temperature includes any one of 288° C., 325° C., 343° C., 371° C., 399° C. and 412° C.

4. A method for determining the gas phase coking tendency of aviation turbine engine lubricating oil, characterized in that: The system for determining the gas phase coking tendency of lubricating oil of an aviation turbine engine according to any one of claims 1 to 3 comprises the following contents: Initial data measurement steps: obtaining the 40°C kinematic viscosity, total acid value, initial weight of the test tube and initial weight of the three-necked flask containing the turbine lubricating oil to be tested; Test steps: Test the turbine lubricating oil for a preset time at several preset heating furnace heating temperatures using a turbine lubricating oil gas phase coking tendency determination system; Final data measurement steps: obtain the 40°C kinematic viscosity, total acid value, final weight of the test tube and final weight of the three-necked flask containing the tested turbine lubricant; Data analysis steps: Obtain the weight of the coke based on the initial weight and final weight of the test tube; Obtain the consumption of the turbine lubricating oil based on the initial weight and final weight of the three-necked flask; Obtain the change in kinematic viscosity and total acid value based on the comparison results of the 40°C kinematic viscosity and total acid value of the turbine lubricating oil to be tested and the 40°C kinematic viscosity and total acid value of the turbine lubricating oil after the test.

5. The method for determining the gas phase coking tendency of aviation turbine engine lubricating oil according to claim 4, characterized in that: The test steps include: Connecting various components in the aviation turbine engine lubricating oil gas phase coking tendency determination system; At a plurality of preset heating furnace temperatures, the heating jacket heats the three-necked flask, the heating furnace heats the test tube, the purified air system adds air into the three-necked flask, and during the heating process, the control subsystem adjusts the heating jacket and the heating furnace's heating temperatures according to the thermocouple data and its first preset temperature value and the oil temperature indicating thermocouple data and its second preset temperature value; After all the preset heating furnaces have completed the test at the preset heating temperature for the preset time, stop heating and cool down; After cooling, the components in the aviation turbine engine lubricating oil gas phase coking tendency determination system are disassembled; Dry the test tube.

6. The method for determining the gas phase coking tendency of aviation turbine engine lubricating oil according to claim 5, characterized in that: The second preset temperature value is 220°C; The preset heating furnace heating temperature includes any one of 288°C, 325°C, 343°C, 371°C, 399°C and 412°C.

7. The method for determining the gas phase coking tendency of aviation turbine engine lubricating oil according to claim 4, characterized in that: The coke weight M3=M2-M1, where M1 is the initial weight of the test tube; M2 is the final weight of the test tube; The consumption of the turbine lubricating oil m5=m4-m3, wherein m3 is the initial weight of the three-necked flask containing the turbine lubricating oil to be tested; m4 is the final weight of the three-necked flask containing the turbine lubricating oil after the test; The viscosity change value is the viscosity change rate %=[(V2-V1) / V1]×100%, wherein V1 is the 40°C kinematic viscosity of the turbine lubricating oil to be tested; V2 is the 40°C kinematic viscosity of the turbine lubricating oil after the test; The total acid value change value=TAN2-TAN1, wherein TAN1 is the total acid value of the turbine lubricating oil to be tested, mgKOH / g; TAN2 is the total acid value of the turbine lubricating oil after the test, mgKOH / g.

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