A method for mission reliability allocation based on aero-engine functional architecture

Abstract

A method for mission reliability allocation based on aero-engine functional architecture includes the following steps: Based on a set functional redundancy R, decision items, and allocated mean time between failures (MTBF), determine the impact of engine functional unit-level object functions on engine failures; obtain the failure impact category; determine the failure impact judgment value S and the mission function judgment value M; and determine the mission success rate of completing the function. Based on the failure impact judgment value S and the mission function judgment value M, calculate the number of mission functions Q. Mi ; Obtain the number of functional failure modes, combine it with functional redundancy R, and calculate the number of task functions Q. Mi The allocation of mission reliability indicators is determined by proportion. Based on the functional architecture of the corresponding systems and functional units of the aero-engine, and considering the influence of factors such as basic reliability, the number of functions for mission success, and functional redundancy on mission reliability, a mission reliability allocation model is constructed.

Description

Technical Field

[0001] This invention belongs to the field of general mass characteristic design methods for aero-engines, and specifically relates to a task reliability allocation method based on the functional architecture of aero-engines. Background Technology

[0002] The mission reliability level of aero-engines is generally measured using the Mean Time Between Critical Failures (MTBCF). The mission reliability level of an aero-engine directly affects the aircraft's ability to successfully perform missions. Therefore, during the aero-engine design phase, it is necessary to accurately allocate the quantitative mission reliability indicators of the entire engine to its systems and functional units, and to clearly define the design specifications for each functional unit.

[0003] While basic reliability allocation methods are detailed in relevant reliability technology books, the theory and methods for mission reliability allocation remain lacking. In aero-engine engineering practice, mission reliability allocation can only be performed by referring to basic reliability allocation methods. Because the mission reliability indicators allocated by methods such as comprehensive scoring and similar product methods are not sufficiently correlated with mission success and functional architecture redundancy, they are difficult to guide and constrain the design of systems or functional units.

[0004] Therefore, there is an urgent need for a mission reliability allocation method that can allocate aero-engine mission reliability indicators to the system or functional unit level during the scheme design phase, so as to serve as input for aero-engine scheme design and detailed design. Summary of the Invention

[0005] To address the above technical problems, this invention provides a task reliability allocation method based on the functional architecture of an aero-engine, comprising the following steps:

[0006] Based on the set functional redundancy R, decision items and allocated mean time between failures (MTBF), determine the impact of engine functional unit level objects on engine faults, obtain the fault impact category, determine the fault impact judgment value S and the task function judgment value M, and determine the task success of completing the function.

[0007] Based on the fault impact judgment value S and the task function judgment value M, calculate the number of task functions Q. Mi ;

[0008] Obtain the number of functional failure modes, combine it with functional redundancy R, and calculate the number of task functions Q. Mi Percentage, allocation of reliability indicators for task completion.

[0009] Furthermore, the fault impact categories include categories I to IV, with corresponding fault impact judgment values ​​S ranging from 4 to 1. The lower the fault impact category, the more severe the fault. When the fault impact category reaches category II, it is considered a severe fault, and the task fails.

[0010] Furthermore, the number of task functions Q Mi Through formula Calculate, when hour, ,when hour, ;

[0011] Among them, S MAXij This refers to the value indicating the most severe category of failure mode impact for the j-th function of the i-th product-level object. j = 1, 2, 3, ..., Q i Q i M represents the number of functionalities contained in the i-th product level object. ij This refers to the task function judgment value of the j-th item of the i-th product level object.

[0012] Furthermore, the task reliability index allocation is based on a task reliability allocation method, which includes:

[0013] Under the same impact on task success, products with lower basic reliability levels are assigned tasks with lower reliability.

[0014] Under the same basic reliability level, products with more task functions and greater impact on task success are assigned tasks with higher reliability.

[0015] With the same basic reliability level, products with higher functional redundancy (R) have higher reliability in assigned tasks.

[0016] Furthermore, the allocation model for the task reliability index allocation supports the calculation of the first task reliability allocation and the calculation of the second task reliability allocation.

[0017] The first task reliability allocation is the task reliability allocation of product-level objects without considering functional redundancy R;

[0018] The second task reliability allocation is the task reliability allocation for product-level objects that takes into account functional redundancy R.

[0019] Furthermore, the calculation of the reliability allocation for the first task specifically includes the following:

[0020] Define the mean time between serious failures (T) for product-level objects. BCFi The allocation calculation formula is as follows:

[0021]

[0022] Where: λ CEThe specified critical failure rate of an engine is the reciprocal of the specified mean time between critical failures (MTBCF); λ i This refers to the failure rate assigned to the i-th product level object, where i = 1, 2, 3, ..., n, and n is the number of objects contained in a certain product level of the engine; Q Mi Q refers to the number of task functions contained in the i-th product level object; i This refers to the number of functions contained in the i-th product level object.

[0023] Furthermore, the calculation of the reliability allocation for the second task specifically includes the following:

[0024] Define the mean time between serious failures (T) for product-level objects. BCFi The calculation formula is:

[0025]

[0026] Where: M ij The task function judgment value of the j-th item of the i-th product level object; R ij This refers to the redundancy of the function of the j-th task in the i-th product-level object; for functions with uncertain redundancy R, Rij ij Take 1.

[0027] Furthermore, when the functional redundancy R is 1, the calculation of the reliability allocation of the first task is equivalent to the calculation of the reliability allocation of the second task.

[0028] Furthermore, after completing the allocation of task reliability indicators, the method further includes: verifying and adjusting the results of the task reliability indicator allocation, including the following steps:

[0029] According to the formula:

[0030]

[0031] Verify the allocation results;

[0032] When the test results are met, it indicates that the allocation result is valid;

[0033] If the test results are not met, the rounded result in the allocation result should be compared with the original value before rounding. The rounded result should be increased by 1 in ascending order of the difference until the test results of the allocation result are passed.

[0034] The beneficial effects of this invention are that, based on the functional architecture of the corresponding systems and functional units of aero-engines, and based on the influence relationship of factors such as basic reliability, number of functions for mission success, and functional redundancy on mission reliability, a mission reliability allocation model is constructed. This model can be used for the allocation of quantitative indicators of mission reliability in the scheme design stage, and can serve as input for aero-engine scheme design and detailed design, playing a guiding and constraining role in the design stage of systems or functional units. Attached Figure Description

[0035] Figure 1 This is a flowchart of a task reliability allocation method according to an embodiment of the present invention; Detailed Implementation

[0036] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0037] This invention provides a mission reliability allocation method based on the functional architecture of an aero-engine. Based on the functional architecture of the corresponding systems and functional unit product levels of the aero-engine, and considering the influence of factors such as basic reliability, the number of mission success functions, and functional redundancy on mission reliability, a mission reliability allocation model is constructed. The method includes the following steps:

[0038] Step S10: Based on the set functional redundancy R, decision items and allocated mean time between failures (MTBF), determine the impact of engine functional unit level objects on engine failures, obtain the failure impact category, determine the failure impact judgment value S and the task function judgment value M, and determine the task success of completing the function.

[0039] In this embodiment, the fault impact categories include categories I to IV, and the corresponding fault impact judgment values ​​S are 4 to 1. The lower the fault impact category, the more serious the fault. When the fault impact category reaches category II, it is a serious fault and the task fails. See Table 1 for details.

[0040] Functional architecture design during the aero-engine design phase is the foundation for establishing reliability models and allocating reliability. Mission reliability design presupposes determining the mission success of functions and identifying the functions within the system or functional unit that are relevant to mission success.

[0041] According to GJB 451 "Reliability, Maintainability, and Supportability Terminology," the Mean Time Between Critical Failures (MTBF) is measured as the ratio of the total time of product tasks to the total number of critical failures across a specified series of task profiles. A critical failure is defined as a failure that prevents the product from completing its specified task. Based on the failure impact classification method specified in GJB 1391 "Guideline for Failure Mode, Effects, and Criticality Analysis," failures that reach Category II impact are classified as critical failures, and their corresponding functions are classified as functions related to task success (hereinafter referred to as task functions).

[0042] The definition of the impact categories of aircraft engine failures is shown in Table 1.

[0043] Table 1 Definition of Engine Fault Impact Categories

[0044]

[0045] Table 2 shows the composition of functional unit-level objects of aero-engines, the allocated mean time between failures (MTBF), object functions, and the determination of the mission success of functions.

[0046] Table 2. Detailed List of Task Success Determination for Functional Unit-Level Objects

[0047]

[0048] Step S20: Calculate the number of task functions Q based on the fault impact judgment value S and the task function judgment value M. Mi ;

[0049] In this embodiment, the number of task functions Q Mi The calculation formula is:

[0050] …………………………(1)

[0051] when hour, ;

[0052] when hour, ;

[0053] in:

[0054] S MAXij This refers to the value indicating the most severe category of failure mode impact for the j-th function of the i-th product-level object. j = 1, 2, 3, ..., Q i Q i The number of features contained in the i-th product level object;

[0055] M ij This refers to the task function judgment value of the j-th item of the i-th product level object.

[0056] Step S30: Obtain the number of functional failure modes, combine it with the functional redundancy R, and calculate the number of task functions Q. Mi Percentage, allocation of reliability indicators for task completion.

[0057] The task reliability index allocation is based on the task reliability allocation principle. On the basis of the failure rate of the basic reliability allocation, the task reliability index is allocated to the corresponding product level objects according to the number of functional failure modes and functional redundancy, based on the proportion of the task functional failure rate.

[0058] Among them, basic reliability allocation and task reliability allocation are both reliability allocation tasks specified by standards such as GJB 450. Task reliability allocation needs to be carried out based on the failure rate of basic reliability allocation.

[0059] The basic reliability allocation process involves allocating the overall basic reliability indicators of the system, such as the mean time between failures (MTBF), to product objects at a specified level within the system. The allocated indicators can be either MTBF or failure rate.

[0060] The task function failure rate percentage is the ideal allocation criterion, but it is unavailable in the early design phase. Therefore, in the method of this invention, the number of task functions Q is used based on functional architecture data. Mi Approximate substitution by proportion;

[0061] The number of functional failure modes was obtained through the Failure Disorientation Effects Analysis (FMEA) work specified in standard GJB 1391.

[0062] In this embodiment, the task reliability index allocation is based on a task reliability allocation method, which includes:

[0063] Under the same impact on task success, products with lower basic reliability levels are assigned tasks with lower reliability.

[0064] Under the same basic reliability level, products with more task functions and greater impact on task success are assigned tasks with higher reliability.

[0065] With the same basic reliability level, products with higher functional redundancy (R) have higher reliability in assigned tasks.

[0066] In this embodiment, the allocation model for the task reliability index allocation supports the calculation of the first task reliability allocation and the calculation of the second task reliability allocation.

[0067] The first task reliability allocation is the task reliability allocation of product-level objects without considering functional redundancy R;

[0068] The second task reliability allocation is the task reliability allocation for product-level objects that takes into account functional redundancy R.

[0069] In this embodiment, the calculation of the reliability allocation of the first task specifically includes the following:

[0070] Define the mean time between serious failures (T) for product-level objects. BCFi The allocation calculation formula is as follows:

[0071]

[0072] …………………(2)

[0073] in:

[0074] λ CE The specified serious failure rate of an engine is the reciprocal of the specified mean time between serious failures (MTBCF).

[0075] λ i The failure rate assigned to the i-th product level object, i = 1, 2, 3, ..., n, where n is the number of objects contained in a certain product level of the engine;

[0076] Q Mi This refers to the number of task functions contained in the i-th product level object;

[0077] Q i This refers to the number of functions contained in the i-th product level object.

[0078] In this embodiment, the calculation of the second task reliability allocation specifically includes the following:

[0079] Define the mean time between serious failures (T) for product-level objects. BCFi The calculation formula is:

[0080]

[0081] ……………(3)

[0082] in:

[0083] M ij The task function judgment value of the j-th item of the i-th product level object;

[0084] R ij This refers to the redundancy of the function of the j-th task in the i-th product-level object; for functions with redundancy R that are not specified, R... ij Take 1.

[0085] In this embodiment, when the functional redundancy R is 1, the calculation of the reliability allocation of the first task is equivalent to the calculation of the reliability allocation of the second task.

[0086] In this embodiment, after the task reliability index allocation is completed, the allocation result may not meet the requirements of the engine task reliability index due to the need for rounding the allocated value. Therefore, it is necessary to check and adjust the allocation result. The check and adjustment include the following steps:

[0087] Allocation result verification formula:

[0088]

[0089] ………………(4)

[0090] When the test results are met, it indicates that the allocation result is valid;

[0091] If the test results are not met, the rounded result in the allocation result should be compared with the original value before rounding. The rounded result should be increased by 1 in ascending order of the difference until the test results of the allocation result are passed.

[0092] In this embodiment, the Mean Time Between Serious Failures (MTBCF) of the engine is specified as 1200 h. The engine architecture design has clearly defined the redundancy of the corresponding functions, and the quantitative indicators of mission reliability are allocated according to formula (3). The allocation results are shown in Table 3.

[0093] Table 3 Task Reliability Calculation Table for Functional Unit-Level Objects

[0094]

[0095] Based on the allocation results in Table 3, the test is performed according to formula (4).

[0096]

[0097] The test passed, and the allocation result is valid.

[0098] The mission reliability allocation method based on the functional architecture of aero-engines proposed in this invention is based on the functional architecture of the corresponding systems and functional units of aero-engines. It constructs a mission reliability allocation model based on the influence relationship of factors such as basic reliability, number of mission success functions, and functional redundancy on mission reliability. It can be used to allocate quantitative indicators of mission reliability in the scheme design stage, and can serve as input for aero-engine scheme design and detailed design, playing a guiding and constraining role in the design stage of systems or functional units.

[0099] The above-disclosed embodiments are merely specific examples of the present invention. However, the present invention is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for mission reliability allocation based on the functional architecture of an aero-engine, characterized in that, Includes the following steps: Based on the set functional redundancy R, decision items and allocated mean time between failures (MTBF), determine the impact of engine functional unit level objects on engine faults, obtain the fault impact category, determine the fault impact judgment value S and the task function judgment value M, and determine the task success of completing the function. Based on the fault impact judgment value S and the task function judgment value M, calculate the number of task functions Q. Mi ; The number of task functions Q Mi Through formula Calculate, when hour, ,when hour, ; Among them, S MAXij This refers to the function of the i-th product level object containing the most severe category judgment value of the failure mode impact, where j=1, 2, 3, ..., Q. i Q i M represents the number of functionalities contained in the i-th product level object. ij The task function judgment value of the j-th item of the i-th product level object; Obtain the number of functional failure modes, combine it with functional redundancy R, and calculate the number of task functions Q. Mi Percentage, allocation of reliability indicators for task completion; The allocation model for the task reliability index supports the calculation of the first task reliability allocation and the second task reliability allocation; the first task reliability allocation is the task reliability allocation of product-level objects without considering functional redundancy R; the second task reliability allocation is the task reliability allocation of product-level objects considering functional redundancy R. The calculation of the reliability allocation for the second task specifically includes the following: Define the mean time between serious failures (T) for product-level objects. BCFi The calculation formula is: Where: λ CE The specified critical failure rate of an engine is the reciprocal of the specified mean critical failure interval (MTBCF); λ i The failure rate assigned to the i-th product level object, where i = 1, 2, 3, ..., n, and n is the number of objects contained in a certain product level of the engine; R ij This refers to the redundancy of the function of the j-th task in the i-th product-level object; for cases where the functional redundancy R is unclear, Rij... ij Take 1.

2. The mission reliability allocation method based on aero-engine functional architecture as described in claim 1, characterized in that: The fault impact categories include categories I to IV, with corresponding fault impact judgment values ​​S ranging from 4 to 1. The lower the fault impact category, the more severe the fault. When the fault impact category reaches category II, it is a severe fault, and the task fails.

3. The mission reliability allocation method based on aero-engine functional architecture as described in claim 1, characterized in that: The task reliability index allocation is based on a task reliability allocation method, which includes: Under the same impact on task success, products with lower basic reliability levels are assigned tasks with lower reliability. Under the same basic reliability level, products with more task functions and greater impact on task success are assigned tasks with higher reliability. With the same basic reliability level, products with higher functional redundancy (R) have higher reliability in assigned tasks.

4. The mission reliability allocation method based on aero-engine functional architecture as described in claim 1, characterized in that: The calculation of the reliability allocation for the first task specifically includes the following: Define the mean time between serious failures (T) for product-level objects. BCFi The allocation calculation formula is as follows: Where: λ CE The specified critical failure rate of an engine is the reciprocal of the specified mean critical failure interval (MTBCF); λ i This refers to the failure rate assigned to the i-th product level object, where i = 1, 2, 3, ..., n, and n is the number of objects contained in a certain product level of the engine; Q Mi Q refers to the number of task functions contained in the i-th product level object; i This refers to the number of functions contained in the i-th product level object.

5. The mission reliability allocation method based on aero-engine functional architecture as described in claim 4, characterized in that: When the functional redundancy R is 1, the calculation of the reliability allocation of the first task is equivalent to the calculation of the reliability allocation of the second task.

6. The mission reliability allocation method based on aero-engine functional architecture as described in claim 1, characterized in that: After completing the allocation of task reliability indicators, the method further includes: verifying and adjusting the results of the task reliability indicator allocation, including the following steps: According to the formula Verify the allocation results; When the test results are met, it indicates that the allocation result is valid; If the test results are not met, the rounded result in the allocation result should be compared with the original value before rounding. The rounded result should be increased by 1 in ascending order of the difference until the test results of the allocation result are passed.

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