Turboshaft engine on-condition maintenance decision-making method considering individual characteristics

Abstract

The invention discloses a turboshaft engine on-condition maintenance decision-making method considering individual characteristics, and belongs to the technical field of turboshaft engine maintenance. The turboshaft engine on-condition maintenance decision-making method comprises the following steps: analyzing composition products of a turboshaft engine in different aspects to obtain influence factors of the composition products; acquiring a damage mode and a measurement parameter of the component product according to the influence factors of the component product; according to the damage mode and the measurement parameter of the composition product, constructing decision-making standards of different maintenance work; wherein the maintenance work comprises external field maintenance and factory return maintenance; according to the damage mode and the measurement parameter of the composition product, setting a corresponding detection mode; according to the detection mode, obtaining measurement parameter values of the composition product, and according to the decision-making standards of the different maintenance work, making a decision on the measurement parameter values to obtain a final condition-based maintenance decision-making scheme of the turboshaft engine. The invention can provide the condition-based maintenance method which is oriented to the use process of the turboshaft engine and considers individual characteristics.

Description

Technical Field

[0001] The present invention belongs to the technical field of turbine engine maintenance, and in particular relates to a turboshaft engine condition-based maintenance decision method taking individual characteristics into consideration. Background Art

[0002] As the power source of helicopters, turboshaft engines currently widely use scheduled maintenance, that is, according to the specified interval, fixed cumulative working time (such as flight hours) or mileage, they are returned to the repair shop and carried out according to a fixed process including disassembly, cleaning, inspection, repair / replacement, assembly, and delivery. Therefore, scheduled maintenance is based on a full understanding of the fault pattern and is carried out according to a pre-arranged time plan, regardless of the current state. Although such a solidified maintenance process can ensure that the performance of the turboshaft engine meets the requirements after the repair, it has the following limitations due to the lack of targeted repair methods:

[0003] First, excessive maintenance. If the turboshaft engine is used in a good environment and has a moderate mission intensity, some parts and accessories on the aircraft will still be in good working condition even after the prescribed repair period. At this time, if the fixed process is followed, these "may not need to be disassembled, may not need to be repaired, and may not need to be replaced" work will lead to a waste of manpower, resources, and costs, and the repaired parts may not be guaranteed to be better than before the repair.

[0004] Second, insufficient maintenance. When the turboshaft engine is under heavy mission intensity and in a harsh operating environment, it is possible that it will be damaged before the specified repair time limit. Even if it can continue to work until the repair time limit, some parts and accessories are seriously damaged. If the fixed process is followed, it will take more manpower, materials and expenses to fully restore these parts;

[0005] Third, availability is limited to a low level. Due to the time limit of the engine's use by the scheduled maintenance method, when a certain number of engines are returned to the repair shop for repair, or encounter sudden failures and cannot work, from the perspective of the overall system, the availability cannot be maintained at a relatively stable level, which is not user-friendly.

[0006] Fourth: Practice has proven that there is a need for improvement. From the work situation in the past decade, whether it is the field maintenance of turboshaft engines or the disassembly and repair after returning to the repair shop, almost all work is carried out in a fixed way, with poor autonomy and freedom, and there is a lot of repetitive and ineffective work, which makes it almost difficult to carry out targeted maintenance work according to the situation of the turboshaft engines.

[0007] Benefits of Condition-Based Maintenance in Improving Maintenance Effectiveness

[0008] Condition-based maintenance is a way of preventive maintenance. It conducts targeted maintenance when signs of functional failures are detected through regular / irregular inspections or continuous monitoring of products. Specifically, functional tests are carried out at certain intervals, and decisions are made based on the status of the object. If there are potential failures that require intervention, targeted maintenance activities are implemented. If there are no potential failures or potential failures that do not require intervention for the time being, the product continues to be used. As a preventive maintenance strategy, condition-based maintenance uses condition assessment to check for potential failures, and then takes necessary measures to prevent functional failures or avoid the consequences of functional failures. The advantages of this maintenance method are as follows:

[0009] First, it can pre-perceive damage and take measures. By means of personnel monitoring, usage inspections, condition detections, etc., it collects equipment operation information and analyzes the status, and takes necessary intervention measures before the problem worsens, and optimizes with the update of equipment status data. This flexibility makes condition-based maintenance have important application value in equipment types with many varieties, complex failure modes, and significant failure impacts such as turboshaft engines.

[0010] Second, at the individual level, it can improve the efficiency level. For different forms of damage exposed at different positions, to different degrees, and of different types during the use of individual objects, targeted damage perception methods are adopted, including but not limited to monitoring, detection, inspection, etc., and measures are taken before their failures to avoid downtime losses caused by aggravated damage.

[0011] Third, at the system level, it can improve the availability level. Considering the damage differences caused by different usage environments and task intensities of group objects, on the basis of damage perception and taking measures at the individual level, further measures are taken from the perspective of overall availability, reducing equipment failures while achieving efficient allocation of maintenance resources, avoiding concentrated downtime, and reducing resource waste. Summary of the Invention

[0012] To solve the above technical problems, the present invention proposes a condition-based maintenance decision-making method for turboshaft engines considering individual characteristics to solve the problems existing in the above-mentioned prior art.

[0013] To achieve the above object, the present invention provides a condition-based maintenance decision-making method for turboshaft engines considering individual characteristics, including:

[0014] Analyze the component products of the turboshaft engine from different aspects to obtain the influencing factors of the component products;

[0015] According to the influencing factors of the component products, obtain the damage modes and measurement parameters of the component products;

[0016] Construct decision criteria for different maintenance tasks based on the damage modes and measurement parameters of the component products; wherein the maintenance tasks include on-site maintenance and factory return maintenance;

[0017] Set corresponding detection methods according to the damage modes and measurement parameters of the component products;

[0018] Obtain the measurement parameter values of the component products according to the detection methods, and make decisions on the measurement parameter values according to the decision criteria for different maintenance tasks to obtain the final condition-based maintenance decision-making scheme for the turboshaft engine.

[0019] Optionally, the process of analyzing the component products of the turboshaft engine in different aspects includes:

[0020] In terms of inherent characteristics, divide the component products, determine the partial types of the component products, divide the main body part of the turboshaft engine into limited-life parts, vulnerable parts, parts that must be replaced, and consumable parts, and divide the accessories part of the turboshaft engine into repairable accessories and non-repairable accessories to obtain the types of component products;

[0021] In terms of usage characteristics, analyze the historical data of the component products to obtain the damage degree and failure frequency of different types of component products;

[0022] In terms of repair characteristics, analyze the work complexity of different maintenance tasks of the component products to obtain the types of maintenance tasks of the component products;

[0023] In terms of engine impact, analyze the engine performance and safety impact of the component products to obtain the discrimination situation of the decision criteria of the component products.

[0024] Optionally, the process of obtaining the damage modes and measurement parameters of the component products includes:

[0025] Determine the damage modes corresponding to the damage degrees of different types of component products according to the damage degrees and failure frequencies in the influencing factors of the component products, and determine the measurement parameters representing the damage modes according to the damage modes. The measurement parameters include quantifiable parameters and non-quantifiable parameters, and the non-quantifiable parameters are represented by corresponding fixed quantifiable parameters.

[0026] Optionally, the process of constructing decision criteria for different maintenance tasks includes:

[0027] For the damage modes and measurement parameters of the component products, set the critical values of the corresponding range intervals, and set the corresponding decision contents for the range intervals. Among them, in on-site maintenance, the corresponding decision contents include normal use, monitoring, key monitoring, inspection, replacement or repair; in factory return maintenance, the corresponding decision contents include: continued use, use after repair, replacement with a new one, repair and replacement of old parts, and scrapping of old parts.

[0028] Optionally, the process of setting the corresponding detection method includes:

[0029] According to the damage modes and measurement parameters of the component products, in on-site maintenance, corresponding visual inspection, borescope inspection and sensing detection are carried out on the turbofan engine according to the measurement parameters to obtain the measurement parameter values; in factory return maintenance, corresponding visual inspection, borescope inspection, sensing detection and experimental detection are carried out on the turbofan engine according to the measurement parameters to obtain the measurement parameter values.

[0030] Optionally, the process of generating the final condition-based maintenance decision scheme for the turboshaft engine includes:

[0031] In on-site maintenance, the measurement parameter values are judged according to the decision criteria of on-site maintenance, and according to the decision criteria, on-site decision contents are generated. If the on-site decision content is replacement or repair, decision-making processing is carried out on the component products to be replaced, that is, the faulty parts, according to the types of the component products. Among them, the decision-making processing contents include: if the faulty part is the overall unit body or the component parts of the unit body, it is returned to the overhaul factory for maintenance; if the faulty part is a repairable accessory, it is judged whether to repair according to the degree of damage; if the faulty part is an irreparable accessory, it is directly scrapped, and the final on-site maintenance condition-based maintenance decision scheme for the turboshaft engine is obtained.

[0032] Optionally, the process of generating the final condition-based maintenance decision scheme for the turboshaft engine includes:

[0033] In factory return maintenance, the turbofan engine is fully disassembled and only some unit bodies are disassembled. The measurement parameter values are judged according to the decision criteria of factory return maintenance and the maintenance cost, and the corresponding factory return decision contents are generated. And according to the types of the component products in the turbofan engine and the decision criteria of factory return maintenance, the factory return decision contents of the component products are adjusted, and it is judged whether the decision in the decision content can be omitted, and the final factory return maintenance condition-based maintenance decision scheme for the turboshaft engine is obtained.

[0034] Optionally, the decision criteria are adjusted according to environmental parameters, mission risks and historical data.

[0035] Compared with the prior art, the present invention has the following advantages and technical effects:

[0036] The present invention focuses on the core of condition-based maintenance: "maintenance actions" that are only performed "when necessary" when there is "factual evidence" to prove that they are necessary. It proposes a condition-based maintenance method that is oriented to the use process of turboshaft engines and takes into account individual characteristics. This method has the following advantages: in the "factual evidence" part, it is proposed that the implementation of condition-based maintenance requires the selection and determination of reasonable inspection, monitoring, and detection parameters in combination with product types; in the "when necessary" part, it is proposed to set thresholds for different maintenance methods for the selected inspection, monitoring, and detection parameters according to four types of considerations; in the "maintenance action" part, corresponding decision contents are formulated for field decisions and return to the factory decisions. This method can provide a reference for the current transformation of turboshaft engines from "scheduled maintenance" to "condition-based maintenance". BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 It is a principle block diagram of a turboshaft engine condition-based maintenance decision method considering individual characteristics according to an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of the corresponding relationship between the measurement parameters, monitoring / detection / inspection methods, and required designs of the embodiments of the present invention;

[0040] Figure 3 This is a schematic diagram of a maintenance solution based on the situation, taking a unit body as an example, according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] The present invention proposes a condition-based maintenance method that takes the field use process and the factory overhaul process of the turboshaft engine as the analysis objects, systematically sorts out and analyzes the influencing factors that need to be considered in the field use of the turboshaft engine, and analyzes the maintenance methods that can be adopted in the field and overhaul for the common failure modes of the components and accessories on the turboshaft engine. At the same time, qualitative or quantitative decision-making standards that can be used to support condition-based maintenance under different failure modes are proposed, and the decomposition depth and maintenance methods of the field use process and the factory overhaul process are decided.

[0043] Benefits of Condition-Based Maintenance in Improving Maintenance Effectiveness

[0044] Condition-based maintenance is a way of preventive maintenance. It conducts targeted maintenance when signs of functional failures are detected through regular / irregular inspections or continuous monitoring of products. Specifically, a function test is carried out at certain intervals, and decisions are made based on the status of the object. If there are potential failures that require intervention, targeted maintenance activities are implemented. If there are no potential failures or potential failures that do not require intervention for the time being, the product continues to be used. As a preventive maintenance strategy, condition-based maintenance uses condition assessment to check for potential failures and takes necessary measures to prevent functional failures or avoid the consequences of functional failures. The advantages of this maintenance method are as follows:

[0045] First, it can perceive damage in advance and take measures. By means of personnel monitoring, usage inspection, condition detection, etc., it collects equipment operation information and analyzes the status, and takes necessary intervention measures before the problem worsens, and optimizes as the equipment condition data is updated. This flexibility makes condition-based maintenance have important application value in equipment types such as turboshaft engines with a large number of equipment types, complex failure modes, and significant failure impacts.

[0046] Second, at the individual level, it improves the efficiency level. For different forms of damage at different positions, degrees, and types exposed during the use of individual objects, targeted damage perception methods are adopted, including but not limited to monitoring, detection, inspection, etc., and measures are taken before their failures to avoid downtime losses caused by aggravated damage.

[0047] Third, at the system level, it improves the availability level. Considering the damage differences caused by different usage environments and task intensities of group objects, based on damage perception and measures taken at the individual level, further measures are taken from the perspective of overall availability to achieve efficient allocation of maintenance resources while reducing equipment failures, avoid centralized downtime, and reduce resource waste.

[0048] It should be noted that the present invention is directed to turboshaft engines. Turboshaft engines have significant differences from other engines (such as turbojet and turbofan engines) in power output, operating characteristics, and applicable scenarios. Turboshaft engines are mainly used in rotorcraft such as helicopters to drive the rotor with shaft power output, and their operating modes need to be adjusted frequently to adapt to complex working conditions such as climbing, hovering, and maneuvering flight. The working environment of turboshaft engines is often more severe. Other engines, such as turbojet and turbofan engines, are mainly used in fixed-wing aircraft and rely on jet thrust to provide power. Compared with turboshaft engines, they usually operate under relatively stable working conditions rather than complex working conditions and changing working environments. Based on the above factors and specific maintenance practices, the demand for condition-based maintenance of turboshaft engines is very different from that of other engines. Therefore, specific analysis needs to be carried out for turboshaft engines to form a unique condition-based maintenance decision-making method, and this method is not applicable to other engines.

[0049] The condition-based maintenance decision-making method for turboshaft engines considering individual characteristics is applicable to turboshaft engines mainly due to the complexity of different components and different damage modes. Even for engines of the same model, due to differences in the tasks performed, different individual turboshaft engines may experience different load changes, temperature shocks, and environmental impacts, resulting in diverse damage modes. Traditional fixed maintenance strategies are difficult to adapt to such individual differences, which may lead to increased costs due to over-maintenance or potential safety hazards due to insufficient maintenance. Therefore, the condition-based maintenance method based on the individual health status can more accurately monitor the wear and aging of key components and dynamically adjust maintenance decisions accordingly, thereby effectively reducing the risk of sudden failures, improving the reliability and economy of the engine, and ensuring that the helicopter maintains good performance in various complex mission environments.

[0050] The technical solution of the present invention:

[0051] A condition-based maintenance decision-making method for turboshaft engines considering individual characteristics according to the present invention, as Figure 1 shown, is achieved through the following steps:

[0052] Step 1: Analyze the influencing factors of condition-based maintenance decision-making for different types of turboshaft engine products:

[0053] Turboshaft engines consist of a variety of product types. The primary task in carrying out condition-based maintenance work should be to determine the factors to be considered in decision-making for different types of products, including the inherent characteristics, usage characteristics, repair characteristics of different types of products that make up the turboshaft engine, and the impact on the engine in four aspects.

[0054] In terms of inherent characteristics, for the main body part of the turboshaft engine, consider four types: limited-life parts, vulnerable parts, mandatory replacement parts, and consumable parts.

[0055] Limited-life parts are key components in turboshaft engines whose service time is strictly controlled and must be compulsorily replaced within the specified life cycle and are usually not repairable for reuse.

[0056] Vulnerable parts refer to components that are easily damaged or worn due to external factors during engine operation. The damage to such components is usually related to vibration, friction, corrosion, or external contamination.

[0057] Mandatory replacement parts refer to components that must be replaced during engine overhaul or specific maintenance, regardless of whether they have reached the theoretical life limit. Generally, it is considered that as long as the engine undergoes disassembly and assembly operations, relevant mandatory replacement parts must be compulsorily replaced to ensure that the engine can still meet safety and performance requirements after maintenance.

[0058] Consumables refer to materials or components that are gradually consumed or functionally degraded during the operation of the engine. Different from other categories, consumables usually do not have a long mechanical life, but need to be replaced or replenished after routine maintenance or when the flight hours reach a certain threshold to maintain the normal operation of the engine.

[0059] For the components and accessories part, components and accessories (generally line replaceable units) are key components designed for quick maintenance and replacement. Consider two types: repairable components and non-repairable components. The inherent characteristic is that condition-based maintenance decision-making is the primary task to achieve "targeted" maintenance.

[0060] In terms of usage characteristics, consider the damage degree (individual characteristics) and failure frequency (group characteristics) of each type of product.

[0061] In terms of repair characteristics, consider the work complexity of on-site maintenance and factory overhaul for each type of product. The work complexity is generally proportional to time and cost and needs to be considered in decision-making. Generally speaking, the work complexity will affect the depth of maintenance decision-making. The simpler the maintenance work, the shallower the maintenance decision-making can be in on-site maintenance or factory overhaul; the more complex the maintenance work, the greater the difficulty of on-site maintenance, and the more inclined to make in-depth maintenance decisions during overhaul.

[0062] In terms of the impact on the engine, consider the impact of damage of each type of product on the engine performance and safety to provide support for what kind of maintenance decision-making should be taken. The impact of the product damage degree on the engine performance and safety will also affect the determination of the maintenance decision threshold interval, which will be mentioned in Step 3.

[0063] Step 2: Collect different types of damage modes of different types of products and determine measurement parameters

[0064] Maintenance, that is, maintenance and repair, is an activity to maintain or restore the specified state and established functions of a product. Therefore, the damage mode of the product is the key object of maintenance activities and also the "condition" in the condition-based maintenance strategy.

[0065] Specifically, the damage modes can be collected according to the composition of the turboshaft engine system, such as unit 1, unit 2, unit n, components and accessories 1, components and accessories 2; or according to the product type, such as mechanical products, electronic products, and mechatronic products.

[0066] The analysis method according to the composition of the turboshaft engine system is as follows:

[0067] ① According to the units included in the engine design scheme, determine the composition of each unit hierarchically. For example, the power turbine unit includes a casing, a rotor system (including working blades, disks, output shafts), and a stator system (including bearing housings, guide vanes); at the same time, according to the components and accessories included in the engine, classify them according to repairable components and non-repairable components.

[0068] ②Combined with the usage experience, collect all possible damage modes of the component parts of each unit, such as the deformation of the casing, the creep of the working blades, and the vibration of the bearings; at the same time, collect all damage modes of each accessory, such as the oil leakage of the fuel filter and the rupture of the filter element.

[0069] ③Determine the measurement parameters for each type of damage mode. For example, creep is characterized by the elongation, vibration is characterized by the amplitude or frequency, deformation is characterized by the amount of deformation, and oil leakage is characterized by the amount of oil leakage.

[0070] The analysis method for the types of products included in the turboshaft engine is similar to the above:

[0071] 1) In mechanical products, such as discs, blades, shafts, bearings, casings, etc.;

[0072] 2) In electronic products, such as controllers, health management systems, cables, plugs, etc.;

[0073] 3) In mechatronic products, such as pumps, valves, valves, etc.;

[0074] Collecting damage modes and determining measurement parameters are similar.

[0075] It is recommended to carry out work according to the first "analysis method based on the system composition of the turboshaft engine" above, which is more operable.

[0076] Step 3: For the damage modes in Step 2, formulate different decision criteria from the perspectives of quantifiable or non-quantifiable

[0077] The decision criteria are an important basis for the specific implementation of condition-based maintenance, that is, according to the severity of different types of damage modes, different maintenance work methods are adopted, which is a more accurate representation of the "condition" in the condition-based maintenance strategy.

[0078] Specifically:

[0079] Quantifiable parameters include crack length or depth, creep elongation, spall area, vibration response, ablation area, etc.; non-quantifiable parameters include carbon deposition amount, deformation amount, wear amount.

[0080] Furthermore, it is necessary to fully consider the impact of the severity of the damage mode on the engine performance and safety, and set intervals for each parameter, that is, when the damage degree is within a certain interval, what maintenance measures should be taken.

[0081] It should be noted that the types of maintenance work corresponding to the interval setting should be formulated separately considering on-site maintenance and factory overhaul. The types of maintenance work here can be carried out and determined by using the reliability-centered maintenance analysis method (mature methods for determining the types of maintenance work can be used to ensure the safe and economical operation of the product at the lowest cost).

[0082] For on-site maintenance, since the engine is in a continuous or intermittent working state, the corresponding manner between the interval setting and the decision type is considered in a dynamic way over time (dynamic adjustment, depending on the impact of the parameter type on the engine use, with emphasis on the impact on performance and safety. The core lies in the critical values of each interval, namely X1, X2, and X3, which can generally be given by the designers). It can be referred to the following manner:

[0083] When 0 ≤ parameter value < X1, it is in normal use;

[0084] When X1 ≤ parameter value < X2, attention is needed (every certain time t1);

[0085] When X2 ≤ parameter value < X3, key monitoring, inspection, and detection are required (the interval time t2 should be less than the above interval time t1);

[0086] When X3 ≤ parameter value, replacement or repair is needed.

[0087] For factory overhaul, since the engine is in a non-working state, the correspondence between the interval setting and the decision type is a static fixed value that does not change with time. It can be referred to the following manner:

[0088] If 0 ≤ parameter value < Y1, it can continue to be used;

[0089] If Y1 ≤ parameter value < Y2, the used parts need to be repaired before use;

[0090] If Y2 ≤ parameter value < Y3, new parts need to be used, and the used parts can be repaired;

[0091] If Y3 ≤ parameter value < Y4, new parts need to be used, and the used parts cannot be repaired and are directly scrapped.

[0092] The setting of the number of intervals should be related to the damage mode, its decision criteria, and the corresponding optional maintenance methods, and generally should not be less than 2.

[0093] For quantifiable parameters, the parameter values of each interval should be accurate numerical values; for non-quantifiable parameters, the parameter values of each interval can be determined according to engineering experience as approximate numerical values. (Although it is not easy to quantify, it can still be expressed by a quantitative value. However, the quantitative value here is not necessarily a uniquely determined value. For example, for the carbon deposit amount, measures need to be taken when it reaches a certain level. This carbon deposit can be the carbon deposit area or the carbon deposit thickness; another example is the wear amount, which can be the wear area or the wear depth.)

[0094] Step 4: For the damage modes in Step 2, make the different types of engine products have a design that can be monitored, (or / and) detected, (or / and) inspected

[0095] The damage mode needs to be monitored, detected, or inspected before the maintenance activities can be carried out. Therefore, it is an important prerequisite that the products on the engine are designed to be monitorable, detectable, and inspectable, that is, the "condition" can be "seen". Similar to Step 3, when designing the engine products to be monitorable, detectable, and inspectable, the types of maintenance work for on-site maintenance and factory overhaul should also be considered.

[0096] Specifically:

[0097] Regarding the quantifiable parameters (crack length or depth, creep elongation, spall area, vibration response, ablation area) and non-quantifiable parameters (carbon deposit amount, deformation amount, wear amount) mentioned in Step 3.

[0098] During on-site maintenance work, the above-mentioned measurement parameters can be obtained through visual inspection, borescope inspection, vibration monitoring, metal debris monitoring, lubricating oil monitoring, and numerical control system detection. The "measurement parameter - monitoring / detection / inspection method - design to be possessed" is as Figure 2 shown. Specifically, for external damage, it should be designed to be visually observable without obstruction; for internal damage, several borescope holes should be designed; for vibration response monitoring, vibration sensors should be installed at appropriate positions; for metal debris monitoring, metal debris sensors should be installed in the lubricating oil circuit; for lubricating oil leakage, lubricating oil consumption sensors can be installed. The increase in carbon deposit amount, deformation amount, and oil leakage will further affect the engine performance, and monitoring can be achieved through the numerical control system. In addition to the above designs, the accessories of the engine should be designed as on-site replaceable units, and if the design level is higher, even the unit bodies can be designed as on-site replaceable units.

[0099] During factory overhaul work, since the overhaul factory has the ability to complete all repair work and the monitoring methods are more comprehensive, when the turboshaft engine is in a non-operating state, in addition to visual inspection and borescope inspection used in on-site maintenance, it also includes appearance inspection, non-destructive inspection, torque inspection, seal inspection, fit inspection, etc. (These are conventional inspection techniques commonly used by turboshaft engine overhaul factories, and the information is from the overhaul manual.) And bench testing (operating state) can be carried out, and all damage types can be monitored, detected, and inspected through fixed methods.

[0100] Step 5. On-site maintenance decision

[0101] The primary purpose of condition-based maintenance is to improve the fault recovery ability of the turboshaft engine during on-site use, and to avoid the degradation of availability and the increase in maintenance costs caused by downtime and returning to the factory. Therefore, it is necessary to detect, locate, and replace the faulty parts as much as possible on-site. In short, "replace the faulty one", and the ultimate goal of condition-based maintenance is that when the unit bodies and accessories of the turboshaft engine are designed to be on-site replaceable, all unit body replacements and accessory replacements can be completed on-site.

[0102] The core of condition-based maintenance lies in the "maintenance actions" carried out when there is "factual evidence" proving "when needed". There are three core elements, namely "factual evidence", "when needed", and "maintenance actions". Step 2 and Step 3 provide the specific manifestations and quantification forms of "conditions" in condition-based maintenance, solving the two core elements of "factual evidence" and "when needed". Step 4 provides the methods and prerequisites for "seeing" the "conditions", jointly providing support for taking "maintenance actions".

[0103] For on-site decision-making during the normal use of turboshaft engines, generally after detecting, monitoring, and inspecting faulty parts on-site, replacements are carried out, and the faulty parts are either directly scrapped or sent back to the repair factory separately for repair.

[0104] Specifically, after detecting, monitoring, and inspecting the corresponding unit (including its components) and accessories through the methods mentioned in Step 4 and reaching the replacement standard mentioned in Step 3, the faulty parts are disassembled and new parts are replaced. The handling methods for the faulty parts are as follows:

[0105] If the faulty part is the entire unit (the main body part), the unit is returned to the overhaul factory for repair;

[0106] If the faulty part is a component of the unit, the component is returned to the overhaul factory for repair;

[0107] If the faulty part is a repairable accessory, evaluate the degree of damage. If repair is necessary, return it to the accessory factory for repair. If repair is not necessary, directly scrap it;

[0108] If the faulty part is a non-repairable accessory, directly scrap it.

[0109] Step 6. Decision-making for factory return repair

[0110] Factory return repair is a traditional repair method for turboshaft engines with relatively mature technical conditions. The decision-making for factory return repair includes two situations:

[0111] Firstly, the first three situations mentioned in Step 5;

[0112] Secondly, although the ultimate goal of condition-based maintenance can complete the replacement of all units and accessories on-site, when the turboshaft engine does not fully meet the conditions for condition-based maintenance, it is still necessary to consider returning to the overhaul factory for repair when reaching the overhaul interval or the minimum design life to ensure the performance and safety of the whole machine.

[0113] Specifically, the decision-making content after returning to the factory:

[0114] The depth of decision-making decomposition includes complete disassembly of the whole machine and disassembly of only some units;

[0115] Decision on repair depth is a longitudinal perspective for a single object. Considering the four types of factors in Step 1 and their corresponding costs comprehensively, and referring to Step 3 to determine the extent to which each object should be repaired, including replacing with new parts, replacing with repaired parts, completely repairing the original parts, and repairing the original parts to a certain extent (incomplete repair). In the process of making a decision on repair depth, the core goal is to determine the optimal repair method with the lowest comprehensive cost on the premise of ensuring reliability. First, it is necessary to analyze the direct costs, indirect costs, etc. related to maintenance, covering factors such as replacement, repair, working hours, and downtime losses. Subsequently, compare the cost expenditures of different repair plans, calculate their economy, and select the repair depth with the lowest cost. If the repair cost is greater than or equal to the replacement cost, new parts or repaired parts should be preferred; if the repair cost is significantly less than the replacement cost and complete repair can be carried out to meet the reliability requirements, choose to completely repair the original parts; for parts that are not completely repaired, if they can ensure the reliability of the engine and keep the equipment operating within an acceptable range, cost reduction can be considered through incomplete repair.

[0116] Decision on repair scope is a horizontal perspective for the entire engine. Considering the four types of factors in Step 1 and the decision-making criteria in Step 3 comprehensively, decide which parts must be repaired and which can be omitted. The four types of factors of the turboshaft engine affect the design of engine monitoring, inspection, and examination, that is, the basis for "seeing" in condition-based maintenance of the engine; and based on the four types of factors, the engine design considers modular and replaceable designs, which determines that when the engine fails, the maintenance unit or component can be flexibly determined. Then, considering the decision-making criteria in Step 3, the specific maintenance content of the engine components can be determined horizontally.

[0117] Finally, a condition-based maintenance plan for a certain engine considering repair depth and repair scope is formed. The schematic diagram is as Figure 3 shown.

[0118] Step 7: Dynamic adjustment of the critical value in the maintenance decision interval

[0119] In the maintenance of complex systems such as turboshaft engines, although the parameter critical values (such as crack width, oil leakage, corrosion area, etc.) are usually preset based on material properties, safety redundancy, and engineering experience and are strictly followed after being set and generally not modified. However, based on the actual situation and a scientific and rigorous working attitude, dynamically adjusting the critical value to adapt to environmental changes or the cumulative effect of time is indeed an effective means to improve the flexibility and safety of maintenance.

[0120] The following are several feasible dynamic adjustment methods:

[0121] 1. Dynamic compensation based on the environment

[0122] The external environmental parameters (temperature, humidity, air pressure, etc.) are monitored in real time through environmental sensors, and the threshold range of the critical value is dynamically corrected. This method is only applicable to the maintenance decision-making in the field.

[0123] 2. Dynamic Threshold Based on Task Risk

[0124] According to the current task duration and risk tolerance of the engine, the critical value is dynamically adjusted. This technology requires task risk assessment and flexibly stipulates the maintenance strategy of the turboshaft engine. For short-term and highly important tasks, due to the extremely low risk tolerance, the threshold interval should be tightened to strictly control the engine performance fluctuation and reduce the risk of sudden failures. For long-duration continuous tasks with high task risk tolerance, the threshold interval can be appropriately relaxed to adapt to long-term operation and ensure the priority completion of the task.

[0125] To implement the risk-driven maintenance strategy of the turboshaft engine in the field mission, two key factors, namely task duration and task risk tolerance, can be quantified and integrated into a comprehensive evaluation index to guide the dynamic adjustment of the performance threshold interval.

[0126] Specifically, the task duration (T) reflects the length of the task operation cycle, and the risk tolerance (R) reflects the tolerance degree of the task to the consequences of failures. After normalization, a threshold adjustment factor D is constructed and defined as follows:

[0127]

[0128] Among them, T is the task duration, which is normalized to the interval [0, 1] and denoted as T';

[0129] R is the risk tolerance, which can also be normalized to the interval [0, 1] and denoted as R';

[0130] ω T is the weight of the task duration;

[0131] ω R is the weight of the task risk tolerance;

[0132] ω T + ω R = 1;

[0133] (1 - R') indicates that the higher the risk (the lower the tolerance), the higher the score of this item.

[0134] Based on the D value obtained from this formula, the threshold adjustment strategy can be specifically formulated. For example: when D ≥ 0.8, it is determined as a high-risk short-term task, and the threshold interval is considered to be tightened for stricter performance control; when 0.5 ≤ D < 0.8, it is determined as a medium task, and the threshold interval remains unchanged; when D < 0.5, it is determined as a long-duration task with high tolerance, and the threshold interval is considered to be relaxed.

[0135] This model reflects that when the task is shorter and the risk tolerance is lower, the factor 𝐷 is larger, indicating that more stringent control of performance fluctuations is required, thus tightening the threshold interval; conversely, if the task tolerance is high and the duration is long, the threshold limit can be appropriately relaxed to enhance the flexibility and continuity of task completion.

[0136] This method is only applicable to the maintenance decision-making in the field.

[0137] 3. Statistical Process Control Based on Historical Data

[0138] By using the damage data accumulated over a long period, the critical value is dynamically updated to avoid being overly conservative or overly radical caused by a "one-size-fits-all" threshold. This part needs to be achieved through data analysis and by using statistical process control techniques. This method is applicable to both the maintenance decision-making in the field and the return-to-factory situation.

[0139] However, it should be noted that many restrictions need to be imposed in the specific implementation of dynamic adjustment, as follows:

[0140] 1. Data quality requirements: High-precision sensors and long-term data accumulation are required. Otherwise, blind adjustment without scientific basis may lead to risks. 2. Standard compliance: In the aviation field, relevant rules and regulations need to be complied with, and dynamic adjustment requires strict certification. 3. Cost-benefit balance: Frequent adjustment may increase the maintenance complexity, and the safety and economy need to be weighed. 4. Risk of human intervention: Over-reliance on algorithms may lead to "black-boxing", and the decision-making power of engineers needs to be retained.

[0141] Taking a certain type of turboshaft engine as an example, this invention selects the unit body and components for illustration respectively. Among them, the rotor system of the power turbine unit body is selected for the unit body, and the oil filter is selected for the components.

[0142] Analysis of Consideration Factors

[0143] In terms of inherent characteristics, the rotor system consists of shafts, disks, and blades and belongs to limited-life parts; the oil filter belongs to repairable components.

[0144] In terms of usage characteristics, the three types of products of the rotor system are all mechanical products, and the damage forms are cracks, fractures, wear, and deformation; the damage modes of the oil filter are oil leakage, blockage, filter element rupture, etc. According to statistics, the failure probability is about 3.51%, which is at a relatively low level.

[0145] In terms of repair characteristics, the power turbine unit body is designed for field replacement. When the three component parts are damaged to the point where they cannot work, the unit body needs to be returned to the factory for repair; the oil filter is also designed for field replacement. When it is damaged to the point where it cannot work in the field, it is replaced with a new one.

[0146] Regarding the impact on the engine, the rotor system of the power turbine unit is very important for the engine operation and directly affects performance and safety. After the oil filter leaks or the filter element ruptures, the engine can still operate for a period of time, but it needs to be replaced as soon as possible. Otherwise, insufficient oil supply will cause greater damage to the engine's mechanical components.

[0147] Formulate decision-making criteria:

[0148] During the outfield operation of the engine,

[0149] Regarding the crack damage of the blade:

[0150] When 0 ≤ crack width < 0.01μm, it can be used normally;

[0151] When 0.01μm ≤ crack width < 0.05μm, borescope inspection is required (every 10 flights);

[0152] When 0.05μm ≤ crack width < 0.1μm, key borescope inspection is required (every 3 flights);

[0153] When 0.1μm ≤ crack width, it is necessary to stop working and return to the factory with the unit.

[0154] Regarding the deformation damage of the blade:

[0155] When the blade deformation is < 0.5mm, it can be used normally;

[0156] When 0.5mm ≤ blade deformation < 1.5mm, regular inspection is required (every 20 flights);

[0157] When 1.5mm ≤ blade deformation < 3mm, key inspection is carried out (every 10 flights);

[0158] When the blade deformation ≥ 3mm, it is necessary to immediately stop using and return to the factory with the unit.

[0159] Regarding the high-temperature corrosion, melting, and wear of the blade:

[0160] When the corrosion, melting, and wear area < 10mm², it can be used normally;

[0161] When 10mm² ≤ corrosion, melting, and wear area < 30mm², regular inspection is required (every 20 flights);

[0162] When 30mm² ≤ corrosion, melting, and wear area < 50mm², key inspection is carried out (every 10 flights);

[0163] When the corrosion, melting, and wear area ≥ 50mm², it is necessary to immediately stop using and return to the factory with the unit.

[0164] For crack damage of the output shaft:

[0165] When the crack width < 0.01 mm, it can be used normally;

[0166] When 0.01 mm ≤ crack width < 0.05 mm, borescope inspection is required for attention (every 15 flights for inspection);

[0167] When 0.05 mm ≤ crack width < 0.1 mm, key borescope inspection is carried out (every 5 flights for inspection);

[0168] When the crack width ≥ 0.1 mm, it is necessary to stop using immediately and return to the factory with the unit body.

[0169] For wear of the output shaft:

[0170] When the wear depth < 0.1 mm, it can be used normally;

[0171] When 0.1 mm ≤ wear depth < 0.3 mm, regular inspection is required for attention (every 20 flights for inspection); when the wear depth ≥ 0.3 mm and < 0.5 mm, key inspection is carried out (every 10 flights for inspection); when the wear depth ≥ 0.5 mm, it is necessary to stop using immediately and return to the factory with the unit body.

[0172] For torsional deformation of the output shaft:

[0173] When the torsional angle < 0.5°, it can be used normally;

[0174] When 0.5° ≤ torsional angle < 1.5°, regular inspection is required for attention (every 20 flights for inspection);

[0175] When the torsional angle ≥ 1.5° and < 3°, key inspection is carried out (every 10 flights for inspection);

[0176] When the torsional angle ≥ 3°, it is necessary to stop using immediately and return to the factory with the unit body.

[0177] For corrosion of the output shaft:

[0178] When the corrosion area < 2%, it can be used normally;

[0179] When the corrosion area is between 2% and 5%, regular inspection is required for attention (every 20 flights for inspection);

[0180] When the corrosion area is between 5% and 10%, key inspection is carried out (every 10 flights for inspection);

[0181] When the corrosion area ≥ 10%, it is necessary to stop using immediately and return to the factory with the unit body.

[0182] For deformation of the disc:

[0183] When the disk deformation is less than 0.5 mm, it can be used normally;

[0184] When 0.5 mm ≤ disk deformation < 1.5 mm, regular detection and attention are required (every 20 flights for detection);

[0185] When 1.5 mm ≤ disk deformation < 3 mm, key detection is carried out (every 10 flights for detection);

[0186] When the disk deformation ≥ 3 mm, it is necessary to immediately stop using and return to the factory with the unit body.

[0187] Regarding the cracks on the disk:

[0188] When the crack width is less than 0.01 mm, it can be used normally;

[0189] When 0.01 mm ≤ crack width < 0.05 mm, borescope inspection and attention are required (every 10 flights for detection); when 0.05 mm ≤ crack width < 0.1 mm, key borescope inspection is carried out (every 3 flights for detection); when the crack width ≥ 0.1 mm, it is necessary to immediately stop using and return to the factory with the unit body.

[0190] Regarding the high-temperature corrosion and wear of the disk:

[0191] When the wear depth is less than 0.2 mm (or the corrosion area is less than 2%), it can be used normally;

[0192] When 0.2 mm ≤ wear depth < 0.5 mm (or the corrosion area is between 2% and 5%), regular detection and attention are required (every 20 flights for detection); when the wear depth ≥ 0.5 mm and < 1.0 mm (or the corrosion area is between 5% and 10%), key detection is carried out (every 10 flights for detection); when the wear depth ≥ 1.0 mm (or the corrosion area ≥ 10%), it is necessary to immediately stop using and return to the factory with the unit body.

[0193] Regarding the oil leakage of the oil filter:

[0194] When 0 ≤ oil leakage < 0.001 ml / h, it can be used normally;

[0195] When 0.001 ml / h ≤ oil leakage < 0.01 ml / h, inspection is required (after every 5 flights);

[0196] When 0.01 ml / h ≤ oil leakage < 0.1 ml / h, key inspection is carried out (after each flight);

[0197] When 0.1 ml / h ≤ oil leakage, the oil filter needs to be replaced.

[0198] Regarding the blockage of the oil filter:

[0199] When the oil flow rate decreases by less than 5%, it can be used normally;

[0200] When 5% ≤ the oil flow rate decrease < 10%, regular detection and attention are required (detect every 15 working cycles);

[0201] When 10% ≤ the oil flow rate decrease < 15%, key detection is carried out (detect every 5 working cycles);

[0202] When the oil flow rate decrease ≥ 15%, it is necessary to immediately stop using and return to the factory for maintenance.

[0203] For the damage of the lubricating oil filter screen and the rupture of the filter element:

[0204] When the damaged area < 2%, it can be used normally;

[0205] When 2% ≤ the damaged area < 5%, regular detection and attention are required (detect every 20 working cycles);

[0206] When 5% ≤ the damaged area < 10%, key detection is carried out (detect every 10 working cycles);

[0207] When the damaged area ≥ 10%, it is necessary to immediately stop using and return to the factory with the unit body.

[0208] For the vibration damage of the lubricating oil filter:

[0209] When the vibration amplitude < 0.2m / s², it can be used normally;

[0210] When 0.2m / s² ≤ the vibration amplitude < 0.5m / s², regular detection and attention are required (detect every 15 working cycles);

[0211] When 0.5m / s² ≤ the vibration amplitude < 1.0m / s², key detection is carried out (detect every 5 working cycles);

[0212] When the vibration amplitude ≥ 1.0m / s², it is necessary to immediately stop using and return to the factory for maintenance

[0213] For the false alarm and sensor failure of the lubricating oil filter:

[0214] When the false alarm rate < 1%, it can be used normally;

[0215] When 1% ≤ the false alarm rate < 3%, regular monitoring and attention are required (detect every 30 working cycles);

[0216] When 3% ≤ the false alarm rate < 5%, key detection is carried out (detect every 15 working cycles);

[0217] When the false alarm rate ≥ 5%, it is necessary to immediately stop using and return to the factory for repair or replace the sensor.

[0218] Regarding the inability to open the lubricating oil filter bypass valve:

[0219] When the abnormal opening frequency < 1 time / 100 working cycles, it can be used normally;

[0220] When the abnormal opening frequency is between 1 and 3 times / 100 working cycles, regular inspections are required (inspect every 50 working cycles);

[0221] When the abnormal opening frequency is between 3 and 5 times / 100 working cycles, key inspections are carried out (inspect every 20 working cycles);

[0222] When the abnormal opening frequency > 5 times / 100 working cycles, it is necessary to immediately stop using and return to the factory for repair or replace the bypass valve.

[0223] After the engine returns to the factory,

[0224] Regarding the crack damage of the blade:

[0225] When 0 ≤ crack width < 0.01μm, it can be used normally;

[0226] When 0.01μm ≤ crack width < 0.1μm, the blade is repaired;

[0227] When 0.1μm ≤ crack width, a new blade is replaced.

[0228] Regarding the deformation damage of the blade:

[0229] When the blade deformation < 0.5mm, it can be used normally;

[0230] When 0.5mm ≤ blade deformation < 3mm, the blade is repaired;

[0231] When the blade deformation ≥ 3mm, a new blade is replaced.

[0232] Regarding the high-temperature corrosion, melting, and wear of the blade:

[0233] When the corrosion, melting, and wear area < 10mm², it can be used normally;

[0234] When 10mm² ≤ corrosion, melting, and wear area < 50mm², the blade is repaired;

[0235] When the corrosion, melting, and wear area ≥ 50mm², a new blade is replaced.

[0236] Regarding the crack damage of the output shaft:

[0237] When the crack width < 0.01mm, it can be used normally;

[0238] When 0.01mm ≤ crack width < 0.1mm, the output shaft is repaired;

[0239] When the crack width ≥ 0.1 mm, replace the new output shaft.

[0240] Regarding the wear of the output shaft:

[0241] When the wear depth < 0.1 mm, use it normally;

[0242] When 0.1 mm ≤ wear depth < 0.5 mm, repair the output shaft;

[0243] When the wear depth ≥ 0.5 mm, replace the new output shaft.

[0244] Regarding the torsional deformation of the output shaft:

[0245] When the torsional angle < 0.5°, use it normally;

[0246] When 0.5° ≤ torsional angle < 3°, repair the output shaft;

[0247] When the torsional angle ≥ 3°, replace the new output shaft.

[0248] Regarding the corrosion of the output shaft:

[0249] When the corrosion area < 2%, use it normally;

[0250] When the corrosion area is between 2% and 10%, repair the output shaft;

[0251] When the corrosion area ≥ 10%, replace the new output shaft.

[0252] Regarding the deformation of the disc:

[0253] When the disc deformation < 0.5 mm, use it normally;

[0254] When 0.5 mm ≤ disc deformation < 3 mm, repair the disc;

[0255] When the disc deformation ≥ 3 mm, replace the new disc.

[0256] Regarding the crack of the disc:

[0257] When the crack width < 0.01 mm, use it normally;

[0258] When 0.01 mm ≤ crack width < 0.1 mm, repair the disc;

[0259] When the crack width ≥ 0.1 mm, replace the new disc.

[0260] Regarding the high-temperature corrosion and wear of the disc:

[0261] When the wear depth < 0.2 mm (or the corrosion area < 2%), use it normally;

[0262] When 0.2 mm ≤ wear depth < 1.0 mm (or corrosion area is between 2% and 10%), the disc is repaired;

[0263] When the wear depth ≥ 1.0 mm (or corrosion area ≥ 10%), a new disc is replaced.

[0264] For the oil leakage of the lubricating oil filter:

[0265] When 0 ≤ oil leakage < 0.001 ml / h, it is used normally;

[0266] When 0.001 ml / h ≤ oil leakage < 0.1 ml / h, it is replaced with a new one and the old part is repaired;

[0267] When 0.1 ml / h ≤ crack width, it is replaced with a new one and the old part is scrapped.

[0268] For the blockage of the lubricating oil filter:

[0269] When the oil flow rate drops < 5%, it is used normally;

[0270] When 5% ≤ oil flow rate drop < 15%, it is restored to use after cleaning and maintenance;

[0271] When the oil flow rate drop ≥ 15%, a new lubricating oil filter is replaced and the old part is repaired.

[0272] For the damage of the filter screen and the rupture of the filter element of the lubricating oil filter:

[0273] When the damaged area < 2%, it is used normally;

[0274] When 2% ≤ damaged area < 10%, the old part is repaired;

[0275] When the damaged area ≥ 10%, a new lubricating oil filter is replaced and the old part is scrapped.

[0276] For the vibration damage of the lubricating oil filter:

[0277] When the vibration amplitude < 0.2 m / s², it is used normally;

[0278] When 0.2 m / s² ≤ vibration amplitude < 1.0 m / s², the old part is repaired;

[0279] When the vibration amplitude ≥ 1.0 m / s², a new lubricating oil filter is replaced and the old part is scrapped.

[0280] For the false alarm and sensor failure of the lubricating oil filter:

[0281] When the false alarm rate < 1%, it is used normally;

[0282] When 1% ≤ false alarm rate < 5%, the sensor is repaired or calibrated;

[0283] When the false alarm rate ≥ 5%, replace the new sensor and scrap the old part.

[0284] Regarding the lubricating oil filter bypass valve that cannot be opened:

[0285] When the abnormal opening frequency < 1 time / 100 working cycles, use it normally;

[0286] When the abnormal opening frequency is between 1 and 5 times / 100 working cycles, repair the bypass valve;

[0287] When the abnormal opening frequency > 5 times / 100 working cycles, replace the new bypass valve and scrap the old part.

[0288] Field decision-making and decision-making for returning to the factory:

[0289] In response to the above damage modes and sorting, a decision form is formulated as shown in Table 1, and the grading of the damage modes is determined.

[0290] Table 1

[0291]

[0292] Take the damage modes of the blades and the lubricating oil filter as examples.

[0293] The blade is a vulnerable part. Regarding the crack damage of the blade, let T0 be the starting time of the engine operation. When the engine operates to T0 + 57h, the crack width is detected as 0.035μm during the field borescope inspection. At this time, the crack position is inspected by borescope every 10 flights; when the engine operates to T0 + 216h, the crack width expands to 0.052μm. At this time, the crack position is inspected by borescope every 3 flights; when the engine operates to T0 + 327h, the crack width expands to 0.11μm, and the engine is no longer used. After disassembling the power turbine unit, it is returned to the factory for repair. After returning to the factory, because the crack width ≥ 0.1μm, directly replace the new blade.

[0294] Regarding the high-temperature abrasion and wear damage of the blade, when the engine operates to T0 + 80h, the corrosion area is detected as 15mm2 during the field borescope inspection. At this time, the corrosion position is inspected by borescope every 20 flights; when the engine operates to T0 + 200h, the crack width expands to 35mm2. At this time, the crack position is inspected by borescope every 10 flights; when the engine operates to T0 + 350h, the corrosion area expands to 55mm2, and the engine is no longer used. After disassembling the power turbine unit, it is returned to the factory for repair. After returning to the factory, because the corrosion area ≥ 50mm2, directly replace the new blade.

[0295] The lubricating oil filter is a repairable accessory. Regarding the leakage damage of the lubricating oil filter, when the engine has run for T0 + 120h, during on-site lubricating oil monitoring and visual inspection, an abnormal increase in oil consumption is found, and the oil leakage rate is 0.005 ml / h. At this time, the oil leakage condition of the lubricating oil filter is checked every 5 flights; when the engine has run for T0 + 300h, the oil leakage rate expands to 0.03 ml / h, and at this time, the oil leakage condition is checked every flight; when the engine has run for T0 + 450h, the oil leakage rate expands to 0.15 ml / h. The lubricating oil filter is replaced with a new one on-site, and the old lubricating oil filter accessory is disassembled and returned to the factory for repair. After returning to the factory, since the oil leakage rate is 0.15 ml / h, a new lubricating oil filter is directly replaced.

[0296] Regarding the damage of the lubricating oil filter screen, when the engine has run for T0 + 120h, during on-site metal chip monitoring, it is found that the metal chips of the lubricating oil filter cannot be completely filtered out. After visual inspection, the damaged area is found to be 3%. At this time, the oil leakage condition of the lubricating oil filter is checked every 20 flights; when the engine has run for T0 + 300h, the damaged area of the screen reaches 8%, and at this time, the damaged condition of the screen is checked every 10 flights; when the engine has run for T0 + 450h, the damaged area of the screen is 12%. The lubricating oil filter is replaced with a new one on-site, and the old lubricating oil filter accessory is disassembled and returned to the factory for repair. After returning to the factory, since the damaged area is greater than 12%, a new lubricating oil filter is directly replaced.

[0297] (4)Dynamic adjustment of the critical value of the maintenance decision interval

[0298] For the external environmental data provided by the environmental sensor, when the engine operates in a high-temperature environment, a dynamic adjustment method for triggering the dynamic compensation mechanism based on environmental conditions is adopted.

[0299] Under long-term high-temperature working conditions, the fatigue rate of metal materials increases, and the critical value of the crack width of 0.1 μm can be dynamically reduced by 0.02 μm. That is, during on-site maintenance decision-making:

[0300] When 0 ≤ crack width < 0.01 μm, it can be used normally;

[0301] When 0.01 μm ≤ crack width < 0.03 μm, it is necessary to conduct borescope inspection (every 10 flights);

[0302] When 0.03 μm ≤ crack width < 0.08 μm, key borescope inspection is required (every 3 flights);

[0303] When 0.08 μm ≤ crack width, it is necessary to stop working and return to the factory with the unit body.

[0304] For an urgent and major military mission, a dynamic adjustment method for triggering the dynamic threshold based on mission risk is adopted. The mission T' is 0.75, R' is 0.8, ω T is determined to be 0.4, ωR It is determined to be 0.6. After calculation, the D value is obtained as 0.42, which is less than 0.5, and the task is determined to be a long-term high-tolerance task.

[0305] Therefore, during the task, the temporary relaxation of the blade crack width is allowed by 0.02μm, but the original standard is still referred to after the task. That is, during the on-site maintenance decision-making during the task:

[0306] When 0 ≤ crack width < 0.03μm, it is used normally;

[0307] When 0.03μm ≤ crack width < 0.07μm, borescope inspection is required (every 10 flights);

[0308] When 0.07μm ≤ crack width < 0.12μm, key borescope inspection is required (every 3 flights);

[0309] When 0.12μm ≤ crack width, the work needs to be stopped and returned to the factory with the unit body.

[0310] For turboshaft engines with a large amount of maintenance data, a dynamic adjustment method based on statistical process control triggered by historical data can be considered artificially.

[0311] Through the long-term accumulated damage data, the critical value is updated dynamically. For example, for group analysis of the same type of engine, summarize the blade crack damage law of the same batch. If the blades of a certain batch in the field frequently fail at 0.09μm, the critical value can be dynamically lowered by 0.02μm.

[0312] For on-site maintenance decision-making of blade cracks:

[0313] When 0 ≤ crack width < 0.01μm, it is used normally;

[0314] When 0.01μm ≤ crack width < 0.03μm, borescope inspection is required (every 10 flights);

[0315] When 0.03μm ≤ crack width < 0.08μm, key borescope inspection is required (every 3 flights);

[0316] When 0.08μm ≤ crack width, the work needs to be stopped and returned to the factory with the unit body.

[0317] If in the specific maintenance practice of returning to the factory, it is found that the blades of a certain batch can still be restored to a good effect when repaired at 0.12μm, the return-to-factory repair threshold can be increased by 0.02μm.

[0318] For return-to-factory maintenance decision-making of blade cracks:

[0319] When 0 ≤ crack width < 0.01μm, it is used normally;

[0320] When 0.01μm ≤ crack width < 0.12μm, the blade is repaired;

[0321] When 0.12μm ≤ crack width, a new blade is replaced.

[0322] The above is only a preferred specific embodiment of the present application, and the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A turboshaft engine condition-based maintenance decision method considering individual characteristics, characterized in that: include: Analyze the components of the turboshaft engine in different aspects to obtain the influencing factors of the components; According to the influencing factors of the component products, the damage mode and measurement parameters of the component products are obtained; According to the damage modes and measurement parameters of the component products, decision criteria for different maintenance tasks are constructed; wherein the maintenance tasks include field maintenance and factory maintenance; According to the damage mode and measurement parameters of the component products, a corresponding detection method is set; The metric parameter values ​​of the constituent products are obtained according to the detection method, and the metric parameter values ​​are decided according to the decision criteria of the different maintenance works, so as to obtain the final situation-based maintenance decision plan of the turboshaft engine.

2. The method according to claim 1, characterized in that The process of analyzing different aspects of the components of the turboshaft engine includes: In terms of inherent characteristics, the component products are divided to determine the types of the components. The main body of the turboshaft engine is divided into life-limited parts, wearing parts, must-replace parts and consumable parts. The accessory parts of the turboshaft engine are divided into repairable accessories and non-repairable accessories, thereby obtaining the types of the component products. In terms of usage characteristics, historical data of component products are analyzed to obtain the damage degree and failure frequency of different types of component products; In the aspect of repair characteristics, the work complexity of different maintenance tasks constituting the product is analyzed to obtain the maintenance work types constituting the product; In terms of engine impact, the engine performance and safety impact of the component products are analyzed to obtain the judgment of the decision criteria of the component products.

3. The method according to claim 1, characterized in that The process of obtaining the damage mode and measurement parameters of the component products includes: According to the damage degree and failure frequency among the influencing factors of the component products, the damage mode corresponding to the damage degree of the different types of component products is determined, and according to the damage mode, the measurement parameters characterizing the damage mode are determined, wherein the measurement parameters include quantifiable parameters and difficult-to-quantify parameters, wherein the difficult-to-quantify parameters are represented by corresponding fixed quantifiable parameters.

4. The method according to claim 1, characterized in that: The process of constructing decision criteria for different maintenance tasks includes: With respect to the damage modes and measurement parameters of the component products, critical values ​​of corresponding range intervals are set, and corresponding decision contents are set for the range intervals, wherein in field maintenance, the corresponding decision contents include normal use, monitoring, key monitoring and inspection, and replacement or repair; in factory maintenance, the corresponding decision contents include: continued use, use after repair, replacement for use, repair of old parts, replacement for use, and scrapping of old parts.

5. The method according to claim 1, characterized in that The process of setting the corresponding detection method includes: According to the damage mode and measurement parameters of the component products, in field maintenance, corresponding visual, boresight and sensor inspections are performed on the turbine engine according to the measurement parameters to obtain measurement parameter values; in factory maintenance, corresponding visual, boresight, sensor inspections and experimental inspections are performed on the turbine engine according to the measurement parameters to obtain measurement parameter values.

6. The method according to claim 1, characterized in that The process of generating the final condition-based maintenance decision plan for the turboshaft engine includes: In field maintenance, the metric parameter values ​​are judged according to the decision criteria for field maintenance, and the field decision content is generated according to the decision criteria. If the field decision content is replacement or repair, the component product to be replaced, i.e., the faulty part, is decided according to the type of the component product. The decision processing content includes: if the faulty part is a unit body as a whole or a component of the unit body, it is returned to the overhaul plant for repair. If the faulty part is a repairable accessory, it is determined whether to repair it according to the degree of damage. If the faulty part is an accessory that cannot be repaired, it is directly scrapped, and the final field maintenance decision plan for the turboshaft engine is obtained.

7. The method according to claim 1, characterized in that The process of generating the final condition-based maintenance decision plan for the turboshaft engine includes: During the factory repair, the turbine engine is completely decomposed or only partially decomposed into units, and the metric parameter values ​​are judged according to the decision criteria and repair cost of the factory repair, and the corresponding factory return decision content is generated. The component product types and the decision criteria for factory return repair in the turbine engine are used to adjust the factory return decision content of the component products, and it is judged whether the decision in the decision content can be omitted, so as to obtain the situation-based maintenance decision plan for the final factory return of the turboshaft engine for repair.

8. The method according to claim 1, characterized in that Decision criteria are adjusted based on environmental parameters, mission risk, and historical data.

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