Flushing method for lubricating oil system of aero-engine

Abstract

The invention discloses an aero-engine lubricating oil system flushing method, which belongs to the technical field of aero-engine maintenance, and comprises the following steps: evaluating and calculating the proportion K of lubricating oil in a lubricating oil tank of a lubricating oil system in the lubricating oil of the whole lubricating oil system; determining the replacement frequency n of the lubricating oil in the lubricating oil tank, and replacing the lubricating oil in the lubricating oil tank; lubricating oil flushing and mixing are carried out after lubricating oil in the lubricating oil tank is replaced every time; the engine is started for cold operation, and the next step is carried out according to the cold operation condition of the engine; if the cold operation of the engine is abnormal, the engine is started again for cold operation after the metal filings are cleaned; and if the cold running of the engine is normal, then the slow running state running time t is determined for slow running. According to the method, the final cleanliness and the execution times are directly locked, the old oil pollution risk is completely eradicated, process control scientization and standardization are achieved, optimal control over the process is achieved, comprehensive benefits are remarkably improved, unification of safety and economical efficiency is achieved, and guarantee is provided for guaranteeing the overhaul interval of the engine.

Description

Technical Field

[0001] This application relates to the field of aircraft engine maintenance technology, and in particular, to a method for flushing the lubricating oil system of an aircraft engine. Background Technology

[0002] The lubrication system of an aircraft turboshaft engine is generally a self-contained circulation system. It has an oil tank to store lubricating oil, and the oil supply system pumps lubricating oil to engine bearings, gears, and other lubrication points. The return system collects the lubricating oil from each bearing cavity back to the oil tank, as shown in the instruction manual. Figure 1 As shown. When the lubricating oil becomes contaminated (by metal shavings or other contaminants), or when the lubricating oil reaches the end of its service life, the lubricating oil system needs to be flushed and replaced.

[0003] For example, Chinese Patent Publication No. CN104595034 A discloses a flushing method for an aero-engine lubricating oil system. This method can improve the cleanliness of the engine lubricating oil system, reduce the scrap rate of engine bearings and gears, and reduce the number of additional test runs required to replace new bearings and gears. Another example is an external lubricating oil system for an aero-engine disclosed in CN114635803A. This system can automatically switch between two oil supply and return methods: external open circulation and internal self-circulation. It also has functions for cooling and heating the lubricating oil, and can measure the oil supply and consumption, improving the applicability of the lubricating oil system on the test bench under different scenarios.

[0004] For flushing the lubricating oil system of aero-turboshaft engines, the traditional procedure for flushing and replacing the lubricating oil system mainly involves draining the oil from the oil tank through the drain valve of the engine's lubricating oil system; then adding sufficient lubricating oil according to the engine manual requirements; followed by cold running and idle running of the engine. If no abnormalities such as oil leakage or metal shavings alarms are detected during engine operation, the procedure is terminated. If any abnormalities are detected, the above procedure is repeated.

[0005] The existing technology has the following problems: Incomplete oil changes pose a risk of contamination: Besides the oil pan, other parts of the engine's lubrication system (including oil lines, bearing cavities, and lubrication accessories) will still retain a certain proportion of lubricating oil. Conventional methods only replace the oil in the oil pan, neglecting to address this substantial amount of old oil (potentially 20%-30% of the total oil volume). When new and old oil mix, contaminants are diluted but not removed, creating a potential for wear and tear during long-term engine operation.

[0006] The flushing process lacks quantifiable standards to ensure flushing effectiveness: various time parameters, such as slow running after adding lubricating oil, rely on operational experience and are not related to parameters such as the specific volume of the lubricating oil system and pump flow rate.

[0007] The maintenance goals are vague: the existing methods take "no alarms" as the end standard, which is a passive and minimum safety standard, rather than an active and optimized maintenance standard aimed at achieving a specific level of cleanliness. Summary of the Invention

[0008] In view of at least one of the above technical problems, this application provides a flushing method for an aircraft engine lubricating oil system. By directly locking the final cleanliness and the number of flushing cycles, the risk of old oil contamination is eliminated, the process control is made scientific and standardized, the optimal control of the process is achieved, and the insufficient or excessive flushing is avoided. Furthermore, an efficient "displacement-mixing" cycle mechanism is established to ensure the efficient and exponential discharge of old lubricating oil, which ultimately significantly improves the overall efficiency, achieves a balance between safety and economy, and provides a guarantee for ensuring the engine overhaul interval.

[0009] According to one aspect of this application, a method for flushing an aircraft engine lubricating oil system is provided, comprising the following steps: S100: Calculate the proportion K of the lubricating oil in the oil tank of the lubricating oil system to the total lubricating oil in the lubricating oil system; S200: Determine the proportion of new lubricating oil after each oil change based on the ratio K, and determine the number of times n of lubricating oil in the oil pan needs to be changed based on the engine's new lubricating oil proportion requirements, and then change the lubricating oil in the oil pan. S300: Perform the lubricating oil replacement operation in the lubricating oil tank n times in sequence, and flush and mix the lubricating oil after each lubricating oil replacement: start the engine for cold running. If the engine cold running is abnormal and a metal shaving alarm is triggered, clean the metal shavings and start the engine again for cold running. If the engine cold running is normal, run at low speed according to the preset slow running time t.

[0010] In some embodiments of this application, step S100 specifically includes: S101. Take the minimum amount of lubricating oil A liters preset in the engine's oil tank as the amount of lubricating oil in the oil tank; S102. Calculate the sum of the theoretical maximum oil retention capacity of the accessories of the lubricating oil system excluding the lubricating oil tank to be B liters; S103. Calculate the proportion K of the lubricating oil in the lubricating oil tank of the lubricating oil system to the total lubricating oil in the lubricating oil system using the following formula: K=A / (A+B)×100%.

[0011] In some embodiments of this application, step S102 specifically includes: using a three-dimensional model of the engine lubricating oil system, performing fluid simulation and / or geometric calculation on the internal volume of accessories including bearing cavity, lubricating oil pipeline and cooler, and summarizing to obtain the theoretical maximum oil retention capacity of accessories as B liters.

[0012] In step S200, the requirement for the proportion of new lubricating oil in the engine is that the proportion of new lubricating oil in the lubricating oil system should not be less than 99%.

[0013] In some embodiments of this application, the number of times the lubricating oil in the oil tank is replaced, n, is determined by the following formula: (1-K) n ≤0.02.

[0014] In some embodiments of this application, when changing the lubricating oil in the lubricating oil tank in step S200, the lubricating oil in the lubricating oil tank is first drained through the drain valve of the lubricating oil system, and then the minimum required amount of lubricating oil A liters is added to the lubricating oil tank according to the engine design requirements.

[0015] In some embodiments of this application, when starting the engine for cold operation in step S300, the generator drives the engine rotor to reach a preset speed range within a preset time to check for contaminants in the engine. If there are contaminants in the engine, it is determined that the engine cold operation is abnormal; if there are no contaminants in the engine, it is determined that the engine cold operation is normal.

[0016] In some embodiments of this application, step S300, driving the engine ignition rotor to a preset speed range by starting the generator within a preset time specifically includes driving the engine ignition rotor to a speed range of 18% to 22% of the maximum speed by starting the generator within 10 to 20 seconds.

[0017] In some embodiments of this application, step S300, the calculation step of the preset idle state running time t includes: determining the lubricating oil flow rate D delivered by the lubricating oil pump per minute in the idle state according to the design flow characteristics of the lubricating oil pump, the preset minimum amount of lubricating oil added to the lubricating oil tank of the engine is A liters, the sum of the theoretical maximum oil retention of the lubricating oil system accessories other than the lubricating oil tank is B liters, and calculating the preset idle state running time t based on the lubricating oil circulation number not less than M times: t=M×(A+B) / D.

[0018] In some embodiments of this application, the number of oil cycles M is set to 5 times to ensure that the new and old oils in the oil system are fully mixed.

[0019] This application has the following beneficial effects: This application's method for flushing the lubricating oil system of an aircraft engine first assesses and calculates the proportion K of the lubricating oil in the oil tank to the total lubricating oil in the entire lubricating oil system. This allows for the determination of the required number of oil replacements, n, and ensures that the added lubricating oil reaches a certain proportion, meeting the engine's lubricating oil replacement requirements and guaranteeing no impact on subsequent normal engine operation. Furthermore, this application proposes flushing and mixing the lubricating oil after each oil tank replacement: starting the engine for cold running, depending on the engine's cold running condition, either draining the lubricating oil from the oil tank and then refilling it (if the engine's cold running is abnormal), or running at idle for a determined time t (if the engine's cold running is normal), thus achieving thorough mixing of the new and old lubricating oil. This application's method achieves a predictable and quantifiable improvement in maintenance quality. Through engineering experience, it directly links the final cleanliness to the number of oil changes (n), transforming the maintenance result from "unknowable" to "designable and verifiable," fundamentally eliminating the risk of old oil contamination. The method's process control is scientific and standardized. By using a defined flushing time (i.e., idle time t), it completely replaces experience-based operations, achieving optimal process control and avoiding insufficient or excessive flushing. This method establishes an efficient "displacement-mixing" cycle mechanism, ensuring that each oil change proportionally replaces the old oil in the system, thus achieving efficient and exponential discharge of old oil. The overall benefits of this application are significant, maximizing savings in oil consumption and fuel costs, reducing unnecessary engine wear, achieving a balance between safety and economy, and providing a guarantee for ensuring engine overhaul intervals.

[0020] Of course, any product implementing this application does not necessarily need to achieve all the advantages described above simultaneously. In addition to the purposes, features, and advantages described above, this application also has other purposes, features, and advantages. The following will provide a more detailed description of this application with reference to figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the lubricating oil circulation route of an existing aircraft engine lubricating oil system; Figure 2 This is a schematic diagram of the method flow of a preferred embodiment of this application. Detailed Implementation

[0022] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Figure 1 This is a schematic diagram of the lubricating oil circulation route of an existing aircraft engine lubricating oil system; Figure 2 This is a schematic diagram of the method flow of a preferred embodiment of this application.

[0023] A method for flushing an aircraft engine lubricating oil system includes the following steps: S100: Calculate the proportion K of the lubricating oil in the oil tank of the lubricating oil system to the total lubricating oil in the lubricating oil system; S200: Determine the proportion of new lubricating oil after each oil change based on the ratio K, and determine the number of times n of lubricating oil in the oil pan needs to be changed based on the engine's new lubricating oil proportion requirements, and then change the lubricating oil in the oil pan. S300: Perform the lubricating oil replacement operation in the lubricating oil tank n times in sequence, and flush and mix the lubricating oil after each lubricating oil replacement: start the engine for cold running. If the engine cold running is abnormal and a metal shaving alarm is triggered, clean the metal shavings and start the engine again for cold running. If the engine cold running is normal, run at low speed according to the preset slow running time t.

[0024] The meaning of "lubricating oil in the lubricating oil tank of the lubricating oil system" here refers to the minimum amount of lubricating oil to be added to the lubricating oil tank as specified in the engine manual, which is a design requirement parameter of the engine lubricating oil system.

[0025] In some embodiments, the "metal shavings alarm due to abnormal engine cold running" refers to a magnetic plug installed in the lubricating oil circuit. This magnetic plug contains a magnetic detector that uses magnetic force to attract metal shavings, thus triggering the alarm. Subsequent cleaning of the metal shavings involves manually removing the magnetic plug, which reduces the amount of metal shavings in the lubricating oil.

[0026] This application's method for flushing the lubricating oil system of an aircraft engine first assesses and calculates the proportion K of the lubricating oil in the oil tank to the total lubricating oil in the entire lubricating oil system. This allows for the determination of the required number of oil replacements, n, and ensures that the added lubricating oil reaches a certain proportion, meeting the engine's lubricating oil replacement requirements and guaranteeing no impact on subsequent normal engine operation. Furthermore, this application proposes flushing and mixing the lubricating oil after each oil tank replacement: starting the engine for cold running, depending on the engine's cold running condition, either draining the lubricating oil from the oil tank and then refilling it (if the engine's cold running is abnormal), or running at idle for a determined time t (if the engine's cold running is normal), thus achieving thorough mixing of the new and old lubricating oil. This application's method achieves a predictable and quantifiable improvement in maintenance quality. Through engineering experience, it directly links the final cleanliness to the number of oil changes (n), transforming the maintenance result from "unknowable" to "designable and verifiable," fundamentally eliminating the risk of old oil contamination. The method's process control is scientific and standardized. By using a defined flushing time (i.e., idle time t), it completely replaces experience-based operations, achieving optimal process control and avoiding insufficient or excessive flushing. This method establishes an efficient "displacement-mixing" cycle mechanism, ensuring that each oil change proportionally replaces the old oil in the system, thus achieving efficient and exponential discharge of old oil. The overall benefits of this application are significant, maximizing savings in oil consumption and fuel costs, reducing unnecessary engine wear, achieving a balance between safety and economy, and providing a guarantee for ensuring engine overhaul intervals.

[0027] Preferably, step S100 specifically includes: S101. Take the minimum amount of lubricating oil A liters preset in the engine's oil tank as the amount of lubricating oil in the oil tank; S102. Calculate the sum of the theoretical maximum oil retention capacity of the accessories of the lubricating oil system excluding the lubricating oil tank to be B liters; S103. Calculate the proportion K of the lubricating oil in the lubricating oil tank of the lubricating oil system to the total lubricating oil in the lubricating oil system using the following formula: K=A / (A+B)×100%.

[0028] Understandably, by determining the amount of lubricating oil in the oil tank and the sum of the theoretical maximum oil retention of the accessories in the lubricating system excluding the oil tank, the proportion K of the lubricating oil in the oil tank to the total lubricating oil in the lubricating system can be calculated. The proportion K can be used to intuitively assess the percentage of lubricating oil in the oil tank and can serve as a basis for determining the number of times the lubricating oil needs to be replaced.

[0029] Preferably, step S102 specifically includes: using a three-dimensional model of the engine lubricating oil system, performing fluid simulation and / or geometric calculation on the internal volume of accessories including bearing cavity, lubricating oil pipeline and cooler, and summarizing to obtain the theoretical maximum oil retention capacity of accessories as B liters.

[0030] Understandably, finite element software can be used to perform fluid simulation or geometric calculations on the internal volume of each bearing cavity, lubricating oil pipeline, and cooler, etc., based on the three-dimensional model of the engine lubricating oil system. The theoretical maximum oil retention capacity of B liters can then be obtained by summarizing the results. Software calculation is more convenient and faster, and significantly reduces the workload of actual measurement.

[0031] Preferably, the requirement for the proportion of new lubricating oil in the engine in step S200 is that the proportion of new lubricating oil in the lubricating oil system is not less than 99%.

[0032] Understandably, based on engineering practice, when the proportion of new oil in the engine lubrication system reaches 99%, it can be considered that the engine lubrication system has been completely replaced and will not affect subsequent normal use. Therefore, with the goal of ensuring that the proportion of new oil is not less than 99%, determining the number of oil replacements n in the oil tank will yield the final optimal number of oil replacements, thus optimizing the flushing efficiency of the lubrication system.

[0033] In this preferred embodiment, the number of times the lubricating oil in the oil tank needs to be replaced, n, is determined by the following formula: (1-K) n ≤0.02.

[0034] Understandably, directly linking the final cleanliness (≥99% new oil) to the number of executions n transforms the maintenance result from "unknowable" to "designable and verifiable," fundamentally eliminating the risk of old oil contamination.

[0035] In some embodiments, after replacing the lubricating oil in the oil tank of a certain type of turboshaft engine once, the proportion of new lubricating oil is 76.9%; after replacing it twice, the proportion of new lubricating oil is 94.6%; after replacing it three times, the proportion is 98.7%; and after replacing it four times, the proportion is 99.1%. Therefore, it is necessary to replace it four times to ensure that the proportion of new lubricating oil in the lubricating oil system is not less than 99%, thus ensuring the normal operation of the engine.

[0036] Preferably, when changing the lubricating oil in the lubricating oil tank in step S200, the lubricating oil in the lubricating oil tank is first drained through the drain valve of the lubricating oil system, and then the minimum required amount of lubricating oil A liters is added to the lubricating oil tank according to the engine design requirements.

[0037] Understandably, based on the evaluation and calculation in step S100 of the proportion K of the lubricating oil in the lubricating oil tank to the total lubricating oil in the lubricating oil system, the minimum amount of lubricating oil A liters preset by the engine is taken as the amount of lubricating oil in the lubricating oil tank. Further, based on the proportion K, the precise and optimal number of times the lubricating oil in the lubricating oil tank needs to be replaced is calculated. Then, each time the lubricating oil in the lubricating oil tank is replaced, the required minimum amount of lubricating oil A liters needs to be added to the lubricating oil tank according to the engine design requirements. This can achieve precise and efficient control that the proportion of new lubricating oil is not less than 99%, meeting the normal operation requirements of the engine.

[0038] Preferably, in step S300, when starting the engine for cold operation, the generator drives the engine rotor to reach a preset speed range within a preset time to check for contaminants in the engine. If there are contaminants in the engine, the engine is determined to be abnormal during cold operation; if there are no contaminants in the engine, the engine is determined to be normal during cold operation.

[0039] Understandably, starting the engine for a cold run first can check for metal shavings or other phenomena that may affect driving safety, and also avoid engine failures that may be caused by running the engine at slow speed (60% or more of the maximum speed) or higher under polluted conditions.

[0040] In this preferred embodiment, step S300, driving the engine ignition rotor to a preset speed range by starting the generator within a preset time specifically includes driving the engine ignition rotor to a speed range of 18% to 22% of its maximum speed by starting the generator within 10 to 20 seconds.

[0041] Understandably, by briefly driving the engine rotor to about 20% of its maximum speed (i.e., reaching the low speed range) using the starter generator, and then operating it at this low speed, the normal operation of the engine during cold running can be checked. This can serve as a basis for selecting the next step, avoiding affecting engine driving safety or causing other engine malfunctions.

[0042] Preferably, in step S300, the calculation step of the preset idle state running time t includes: determining the lubricating oil flow rate D delivered by the lubricating oil pump per minute in the idle state according to the design flow characteristics of the lubricating oil pump, the preset minimum amount of lubricating oil added to the lubricating oil tank of the engine is A liters, the sum of the theoretical maximum oil retention of the lubricating oil system accessories other than the lubricating oil tank is B liters, and calculating the preset idle state running time t based on the lubricating oil circulation number not less than M times: t=M×(A+B) / D.

[0043] In this preferred embodiment, the number of oil circulation cycles M is set to 5 times to ensure that the new and old oils in the oil system are fully mixed.

[0044] Understandably, running the engine at idle for too short a time may result in insufficient mixing of the old and new lubricating oil, making it impossible to effectively remove the old oil from other parts of the system by changing the lubricating oil in the oil tank; running for too long will cause unnecessary engine wear and fuel consumption.

[0045] It should be noted that the oil pump flow rate is a key design parameter of the oil pump. The flow characteristics of the oil pump (i.e., the minimum flow rate under different speed conditions) are specified during the design phase, and this characteristic is verified and corrected through specialized tests during the research and development process. Based on the design flow characteristics of the oil pump, the oil flow rate D delivered by the oil pump per minute at idle is determined. Combined with the engine's preset minimum amount of oil to add to the oil tank, and the sum of the theoretical maximum oil retention capacity of the oil system accessories excluding the oil tank, the precise idle running time t can be calculated. This completely replaces traditional experience-based operation, achieving optimal process control and avoiding insufficient or excessive flushing.

[0046] In some embodiments, the flow rate of the lubricating oil pump in the idle state of a certain type of turboshaft engine is 4L / min, and the idle state operation time is 5×(5+1.2+0.3) / 4=8.125min.

[0047] As can be seen, this application takes the system physical parameters (A, B, D) as input and calculates the precise flushing time t through formulas, completely replacing experience-based operation, realizing optimal process control, avoiding insufficient or excessive flushing, and ultimately achieving scientific and standardized process control of engine lubricating oil system flushing.

[0048] In summary, this application achieves the following beneficial effects: 1. Predictable and quantifiable improvement in maintenance quality: Through engineering experience, the final cleanliness (≥99% new oil) is directly locked to the number of executions n, making the maintenance result "unknowable" to "designable and verifiable", fundamentally eliminating the risk of old oil contamination; 2. Scientific and standardized process control: Taking system parameters (minimum amount of lubricating oil to be added to the oil tank as specified in the engine manual A, the sum of the theoretical maximum oil retention of accessories in the lubricating system other than the oil tank B, and the flow rate of lubricating oil delivered by the lubricating pump per minute D at idle state) as input, the precise flushing time t is calculated by formula, which completely replaces experience-based operation, realizes optimal process control, and avoids insufficient or excessive flushing. 3. An efficient "displacement-mixing" cycle mechanism has been established: By setting a "5-cycle" mixing standard, it is ensured that the old oil in the system can be replaced proportionally each time the lubricating oil in the oil tank is changed, thereby achieving efficient and exponential discharge of old lubricating oil; 4. Significant overall benefits: While ensuring the highest cleanliness standards, by accurately calculating the minimum n and t, it maximizes the savings in lubricating oil consumption and fuel costs, and reduces unnecessary engine wear, achieving a balance between safety and economy, and providing a guarantee for ensuring engine overhaul intervals.

[0049] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0050] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and aiding in the understanding of a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may readily identify some of the devices as separate embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple secondary embodiments. It is also valid when each secondary embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0051] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification by adopting alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the application. For those skilled in the art, several improvements, modifications, or changes can be made without departing from the principles of this application, and the above technical features can also be combined in an appropriate manner; these improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other occasions without modification, should all be considered as protection of this application.

Claims

1. An aircraft engine lubricating oil system flushing method, characterized by, The method comprises the following steps: S100: calculating the proportion K of the oil in the oil tank in the entire oil system; S200: determining the proportion of new oil after each oil change according to the proportion K, and determining the number n of oil changes in the oil tank according to the new oil proportion requirement of the engine, and performing the oil change in the oil tank; S300: sequentially performing the oil change in the oil tank for n times, and performing oil flushing and mixing after each oil change: starting the engine for cold running, and if the engine cold running is abnormal and metal debris alarm occurs, cleaning the metal debris and starting the engine for cold running again; If the engine cold running is normal, slow running is performed according to the preset slow running time t.

2. The method of claim 1, wherein, Step S100 specifically comprises: S101, taking the minimum amount A of oil added to the oil tank of the engine as the oil amount in the oil tank; S102, calculating the sum B of the maximum theoretical residual oil amounts of the accessories other than the oil tank in the oil system; S103, calculating the proportion K of the oil in the oil tank in the entire oil system by the following formula: K=A / (A+B) ×100%.

3. The method of claim 2, wherein, Step S102 specifically comprises: performing fluid simulation and / or geometric calculation on the internal volumes of the accessories including bearing cavities, oil pipelines and coolers through the three-dimensional model of the engine oil system, and summarizing that the maximum theoretical residual oil amount of the accessories is B liters.

4. The method of claim 1, wherein, The new oil proportion requirement of the engine in step S200 is that the proportion of new oil in the oil system is not less than 99%.

5. A method of flushing an aircraft engine oil system according to claim 4, wherein, The number of times n of changing the lubricating oil in the lubricating oil tank is determined by the following equation: (1 - K) n ≤ 0.

02.

6. The method of claim 1, wherein, In step S200 of replacing the oil in the oil tank, the oil in the oil tank is first emptied through the oil drain valve of the oil system, and then the minimum amount A of oil required by the engine design is added to the oil tank.

7. The method of claim 1, wherein, In step S300 of starting the engine for cold running, the engine fuel rotor is driven to a preset speed range by the starter generator within a preset time, and it is checked whether the engine has pollutants, if the engine has pollutants, it is determined that the engine cold running is abnormal; If the engine has no pollutants, it is determined that the engine cold running is normal.

8. The method of claim 7, wherein, In step S300, the engine fuel rotor is driven to a speed range of 18-22% of the highest speed by the starter generator within 10-20 seconds.

9. The method of claim 1, wherein, In step S300, the calculation steps of the preset slow running time t include: determining the oil flow rate D of the oil pump per minute in the slow running state according to the design flow characteristics of the oil pump, the minimum amount A of oil added to the oil tank of the engine, the sum B of the maximum theoretical residual oil amounts of the accessories other than the oil tank in the oil system, and calculating the preset slow running time t according to the oil circulation number M times: t=M× (A+B) / D.

10. The method of claim 9, wherein, Taking the oil circulation number M as 5 times, the new oil and the old oil in the oil system are fully mixed.

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