Method for determining shortest load holding time after speed reduction in aero-engine acceleration task test run spectrum

Abstract

This invention discloses a method for determining the shortest hold-up time after speed reduction in an aero-engine acceleration mission test spectrum, relating to the field of aero-engine load spectrum technology. The method includes: acquiring and normalizing the measured temperature and speed spectra; using a rainflow filtering threshold based on the maximum and minimum amplitude differences to remove small cycles and disturbance signals, and completing spectral segment completion and interpolation; loading the normalized spectrum into a high-pressure turbine disk finite element thermal simulation model, constructing a transient thermal simulation system including convective heat transfer boundary conditions to obtain the turbine disk temperature field response curve; identifying the shortest hold-up time required under the condition of simultaneous decrease in speed and turbine inlet temperature based on the criterion of continuous convergence of the temperature change rate to a threshold; and compressing spectral segments that do not meet the conditions using a temperature-stress coupled equivalent life conversion method to generate an acceleration mission test spectrum with the shortest hold-up time. This invention improves the damage equivalence and physical accuracy of spectral segment compression and is applicable to the optimization and reconstruction of aero-engine life test spectra.

Description

Technical Field

[0001] This invention relates to the field of aero-engine load spectrum technology, and in particular to a method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum. Background Technology

[0002] With the continuous advancement of aviation technology, the service life of aero-engines has significantly increased. Currently, the design life of military aero-engines has generally reached 6,000 hours, while that of civil aero-engines exceeds 20,000 hours. To assess and verify the structural durability and failure modes of engines during long service life, traditional methods typically require conducting full-life tests. However, these tests are lengthy and resource-intensive; a single complete full-life test can last from months to years, and the cost is prohibitive, significantly hindering the development progress and iteration efficiency of new engine models. Therefore, accelerated mission test programs have become an important means of solving this problem. By rationally compressing repetitive operating conditions within the flight mission spectrum, they shorten the test cycle and reduce test costs, becoming a core tool in aero-engine life verification.

[0003] Constructing acceleration spectrum analysis faces several technical challenges, especially for critical hot-end components such as the high-pressure turbine disk. These components operate under complex thermo-mechanical coupling conditions of high temperature and pressure during flight, making them particularly sensitive to the thermal response characteristics during speed reduction conditions within the mission spectrum. Current mainstream acceleration spectrum construction methods typically rely on empirical equivalent models or statistical compression methods, but lack accurate thermal response modeling for determining the holding time during speed changes. Particularly when engine speed drops sharply from a high value to a low value, and the turbine inlet temperature decreases simultaneously, the turbine disk experiences a significant transient thermal gradient, generating substantial thermal stress. Due to heat transfer hysteresis and thermal inertia, the overall temperature field of the turbine disk requires a certain amount of time to stabilize, and this steady-state response time significantly impacts fatigue life and creep life.

[0004] Current technology has not adequately considered how to accurately determine the shortest holding time after speed reduction, especially how to correctly incorporate this parameter into acceleration test spectra to ensure that the spectra accurately reflect the engine's thermal-stress response under actual service conditions. Therefore, there is an urgent need to propose a solution that can quantitatively identify the time required for the turbine disk to reach thermal steady state, and to reasonably compress the acceleration spectra by combining an equivalent life reduction model. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the shortest load holding time after speed reduction in the test spectrum of an aero-engine acceleration mission. This method addresses the limitations of existing acceleration mission test spectrum compilation processes, which fail to adequately consider the thermal steady-state response of high-temperature components after speed reduction, cannot accurately determine the load holding time, and lack equivalent life guarantee for spectrum compression. The invention enables quantitative identification and reasonable load holding control of the turbine disk thermal steady state under speed reduction conditions, thereby ensuring that the test spectrum still has the ability to accurately reflect the service load characteristics under acceleration conditions, effectively improving the scientific nature of spectrum compression and the efficiency of engine testing.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum includes the following steps:

[0008] Obtain the measured temperature spectrum and measured speed spectrum collected during the test run of the aero-engine;

[0009] The measured temperature spectrum and measured rotational speed spectrum are normalized. The normalization process includes: extracting intermediate flight segment data with peak and valley characteristics; and using a rainflow filtering method based on the maximum and minimum amplitude difference to delete small cycles and disturbance signals with amplitudes less than the set threshold.

[0010] Add points at the beginning and end of the spectrum segment, and insert the original spectrum points in the segment with consistent trend to generate a regular temperature spectrum and a regular rotation speed spectrum.

[0011] The regularized temperature spectrum and regularized rotational speed spectrum are loaded onto the finite element model of the high-pressure turbine disk of the aero-engine to construct a thermal simulation model containing convective heat transfer boundary conditions, and transient simulation is performed to obtain the overall transient temperature field response curve of the turbine disk.

[0012] Analyze the transient temperature field response curve and, based on the criterion that the rate of temperature change converges to a set threshold within a continuous sampling period, identify the shortest load holding time required for the overall temperature field of the turbine disk to reach a steady state under the condition that the engine speed drops from the first value to the second value and the turbine inlet temperature drops synchronously.

[0013] Using the shortest load holding time as the control benchmark for the load holding segment, the load holding segments that do not meet this time are compressed based on the equivalent lifetime conversion method of temperature and stress nonlinear coupling, and the task spectrum structure data containing the shortest load holding time is output.

[0014] A further improvement of the present invention is that the rainflow filtering method includes the following steps:

[0015] Extreme points with local extreme value characteristics are extracted from the measured speed spectrum or temperature spectrum of aero-engines and arranged in chronological order to form an extreme point sequence;

[0016] Calculate the amplitude difference Δ between any two adjacent points in the extreme point sequence, and calculate the filtering threshold Δ% using the following formula:

[0017]

[0018] Among them: G max With G min These are the maximum and minimum amplitude values ​​in the spectral segment, respectively; if Δ is less than the absolute value corresponding to Δ%, then the pair of extreme points is deleted; the selected and retained extreme points are connected in chronological order to construct the filtered spectrum.

[0019] A further improvement of the present invention is that the rainflow filtering method further includes a spectrum beginning and end point supplementation step:

[0020] When the amplitudes of the first and last points in the extreme point sequence after amplitude filtering are not equal and the difference is greater than the preset tolerance, a supplementary point with an amplitude equal to that of the first point is inserted at the end of the sequence so that the spectrum forms a closure in the amplitude dimension. The tolerance is an engineering setting parameter.

[0021] A further improvement of the present invention is that the rainflow filtering method further includes an interpolation processing step:

[0022] For two adjacent points in the selected and retained extreme point sequence, if their amplitude changes in the same direction and the time interval between the two points is greater than the set interpolation threshold, then several intermediate points that conform to the changing trend are selected from the original spectrum between the two points and inserted into the extreme point sequence to form a continuous changing spectrum segment. The consistent changing direction means that the product of the difference between the amplitudes of the two adjacent points is positive.

[0023] A further improvement of the present invention is that the step of loading the regularized temperature spectrum and the regularized rotational speed spectrum onto the finite element model of the high-pressure turbine disk of the aero-engine includes:

[0024] The regularized temperature spectrum and regularized rotational speed spectrum were loaded into a three-dimensional finite element model of the high-pressure turbine disk of the aero-engine;

[0025] In the three-dimensional finite element model, convective heat transfer boundary conditions covering the blade and disk regions are set, and the heat transfer coefficient is preset based on the engine flight conditions and cooling structure parameters.

[0026] Based on the transient heat conduction equation, the transient simulation module of the finite element analysis software is called to perform transient thermal simulation analysis according to the time step, and the transient temperature field response curve of the turbine disk as a whole is obtained.

[0027] A further improvement of the present invention is that the step of analyzing the transient temperature field response curve and identifying the shortest holding time required for the overall temperature field of the turbine disk to reach a steady state under the condition that the engine speed drops from a first value to a second value and the turbine inlet temperature drops synchronously includes:

[0028] Under the operating conditions where the speed of the aero-engine drops from the first value n1 to the second value n2 and the turbine inlet temperature drops from T1 to T2, the corresponding transient temperature field response curve is extracted.

[0029] Based on the temperature-time change trend of typical dangerous nodes in the simulation curve, the shortest response time t1 required for the overall temperature field of the turbine disk to reach thermal equilibrium is determined. The thermal equilibrium state is determined by the convergence of the temperature change rate to the threshold θ.

[0030] The shortest response time t1 is taken as the shortest load holding time under the speed reduction condition, and the corresponding time period is recorded and imported into the test spectrum data table.

[0031] A further improvement of the present invention is that the step of determining the shortest holding time required for the overall temperature field of the turbine disk to reach a steady state includes:

[0032] Select several key nodes in the temperature field response curve and calculate the rate of temperature change of each node per unit time.

[0033] A fixed simulation sampling time interval is set as the judgment period. If the temperature change rate of all key nodes is less than the preset steady-state criterion threshold in two consecutive sampling periods, then the time point is determined to be the shortest response time required to reach thermal steady state.

[0034] The steady-state criterion threshold is a temperature change limit determined based on the thermal response characteristics of the material and the engineering safety margin, preferably within the range of 0.5 to 1.5 degrees Celsius per second;

[0035] The shortest response time is used as the minimum duration standard for retaining the payload segment during the subsequent task spectrum construction process.

[0036] A further improvement of the present invention is that the step of compressing the load-holding segment that does not meet the minimum load-holding time according to the principle of proximity equivalence includes:

[0037] The rotational speed, power, and duration parameters of each load-holding segment are statistically analyzed, and the load-holding segment with the shortest load-holding time is taken as the steady-state reference segment.

[0038] Based on the temperature, stress and load response of each segment, the thermal load of the preceding load-preserving segment is equivalently converted using the creep life conversion model to obtain the equivalent stress life value.

[0039] The conversion results are merged into the reference segment, which is retained as the reconstructed spectral structure. The original load-preserving segments that do not meet the minimum load preservation time are deleted.

[0040] A further improvement of the present invention is that the life calculation model includes an equivalent life calculation method that combines temperature and stress nonlinear coupling, used to determine whether multiple compression bearing segments can be replaced by a reference bearing segment. The calculation method includes the following steps:

[0041] For multiple compression load-preserving spectrum segments, extract the average temperature value and corrected thermal stress value of each spectrum segment at the critical location of the high-pressure turbine disk;

[0042] The average temperature value and the corrected thermal stress value are respectively compared with the steady-state temperature and steady-state thermal stress corresponding to the reference load-bearing segment to obtain the temperature ratio factor and the stress ratio factor respectively.

[0043] The temperature ratio factor and stress ratio factor are weighted by power by the empirically fitted first and second exponents, respectively, and multiplied by the duration of each spectral segment to obtain the equivalent lifetime contribution value of that segment.

[0044] The equivalent lifetime contribution value is accumulated according to the time series of all compression and load-preserving segments to obtain the total equivalent lifetime value of the compression segment.

[0045] A further improvement of the present invention is that the calculation of the equivalent life total value adopts a temperature-stress coupled nonlinear model, the expression of which is:

[0046]

[0047] Where: L accum This represents the cumulative life index corresponding to all compression and load-preserving sections; N represents the number of compression and load-preserving sections to be compressed; σ eq,j σ represents the creep equivalent thermal stress calculated at the critical point of the high-pressure turbine disk in the j-th compression bearing section; ref,load T represents the steady-state equivalent thermal stress of the reference load-bearing section; avg,j T represents the average temperature of the j-th compression segment; ref,load Indicates the steady-state temperature of the reference load-maintaining section; Δt j denoted as the duration of compression in segment j; α and β are the life conversion indices of stress and temperature in the creep life model, derived from the fitting of the creep life curve of high-temperature alloys;

[0048] When the calculated L accum When the lifetime target value of the compression segment is greater than or equal to that of the reference load segment, the compression segment set is determined to meet the equivalent lifetime condition and is used as a replacement spectral segment for the reference segment.

[0049] The beneficial effects of this invention are as follows: By normalizing the measured temperature and speed spectra collected during aero-engine testing, and employing a rainflow filtering method based on the maximum and minimum amplitude difference threshold, this invention effectively identifies and eliminates small cycles and disturbance signals, ensuring the representativeness and stability of the extracted spectral segments. Combined with spectral segment end-to-end point supplementation and trend-consistent interpolation, a normalized temperature and speed spectrum that accurately reflects the changes in operating conditions during flight is generated, improving the physical authenticity of the spectral data input. Based on this, a finite element thermal simulation model of a high-pressure turbine disk, incorporating convective heat transfer boundary conditions, is constructed, and transient simulation analysis is conducted to obtain the overall transient temperature field response curve of the turbine disk, providing a quantitative basis for the thermal dynamic evolution during the speed reduction process. This invention further utilizes the response curves of turbine inlet temperature and speed over time, combined with finite element simulation results, to accurately capture the shortest response time required for the overall turbine disk temperature field to reach thermal steady state under the condition that the engine speed decreases from a high value to a low value while the turbine inlet temperature decreases simultaneously. This addresses the technical shortcomings of traditional acceleration test spectra that fail to scientifically consider thermal hysteresis and steady-state identification. By setting a convergence criterion for the rate of temperature change, a quantitative determination of the shortest holding time is achieved. This time is used as the compression control benchmark, and an equivalent life reduction method based on the nonlinear coupling of temperature and stress is employed to perform equivalent life compression on spectrum segments that do not meet steady-state conditions. During spectrum segment compression, the fitting relationship of the temperature-stress curve and the equivalent approximation principle are referenced to further ensure that the acceleration spectrum structure maintains the ability to simulate the actual working conditions of key hot-end components while meeting the equivalent damage criteria. The steady-state load holding time determination and spectrum compression method proposed in this invention fully considers the thermal inertia and heat transfer hysteresis effects caused by the sudden drop in engine speed during operation. It solves the engineering pain point that traditional spectrum compression cannot guarantee the consistency between damage equivalence and thermal steady state. While ensuring the accuracy of life estimation and the consistency of thermal stress response, it improves the scientific nature, feasibility and engineering practical value of mission spectrum construction, and provides reliable technical support for aero-engine life assessment and accelerated testing. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] in:

[0052] Figure 1 This is a flowchart of the method of the present invention;

[0053] Figure 2 This is a measured speed-temperature spectrum of a certain type of engine in an embodiment of the present invention;

[0054] Figure 3 This is a measured power spectrum of a certain type of engine in an embodiment of the present invention;

[0055] Figure 4 This is the normalized rotational speed spectrum in an embodiment of the present invention;

[0056] Figure 5 This is the normalized temperature spectrum in an embodiment of the present invention;

[0057] Figure 6 This refers to the shortest load holding time after the engine speed is reduced in the acceleration mission test spectrum compiled in this embodiment of the invention.

[0058] Figure 7 The compressive loads used to compress the test spectrum for the acceleration mission in this embodiment of the invention;

[0059] Figure 8 This is an acceleration mission test spectrum compiled in this embodiment of the invention, taking into account the shortest load holding time after the engine speed is reduced. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0061] Example 1

[0062] like Figure 1 As shown, this is an embodiment of the present invention, which provides a method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum, including:

[0063] Step 1: Obtain the measured temperature spectrum and measured speed spectrum collected during the test run of the aero-engine;

[0064] Step 2: Normalize the measured temperature spectrum and measured rotation speed spectrum. The normalization process includes: extracting intermediate flight segment data with peak and valley characteristics; and using a rainflow filtering method based on the maximum and minimum amplitude difference to delete small cycles and disturbance signals with amplitudes less than the set threshold.

[0065] In a preferred embodiment, the rainflow filtering method includes the following steps:

[0066] Extreme points with local extreme value characteristics are extracted from the measured speed spectrum or temperature spectrum of aero-engines and arranged in chronological order to form an extreme point sequence;

[0067] Calculate the amplitude difference Δ between any two adjacent points in the extreme point sequence, and calculate the filtering threshold Δ% using the following formula:

[0068]

[0069] Among them: G max With G min These are the maximum and minimum amplitude values ​​in the spectral segment, respectively; if Δ is less than the absolute value corresponding to Δ%, then the pair of extreme points is deleted; the selected and retained extreme points are connected in chronological order to construct the filtered spectrum.

[0070] Therefore, this embodiment, by introducing a rainflow filtering threshold calculation method based on the maximum and minimum amplitude difference, achieves accurate removal of small disturbances and invalid cycles on the basis of traditional filtering processing, significantly improving the accuracy and engineering adaptability of measured spectrum normalization. Compared with existing methods that rely on empirical filtering or fixed thresholds, this embodiment introduces an adjustable filtering factor and calculates the filtering threshold based on full-spectrum characteristics, making the filtering process more adaptable and physically reasonable.

[0071] Furthermore, the filtering process, combined with extreme point sequence analysis, constructs a spectral structure consistent with the original spectral trend, avoiding load distortion problems caused by spectral compression. This provides a reliable data foundation for subsequent transient thermal simulation and minimum load holding time calculation. Therefore, this embodiment not only automates and parameterizes the rainflow filtering process but also provides high-quality spectral input for subsequent turbine thermal load analysis, demonstrating significant engineering promotion value and application prospects.

[0072] Step 3: Add points at the beginning and end of the spectrum segment, and insert the original spectrum points in the segment with consistent trend to generate a regular temperature spectrum and a regular rotation speed spectrum;

[0073] The regularized temperature spectrum and regularized rotational speed spectrum are loaded onto the finite element model of the high-pressure turbine disk of the aero-engine to construct a thermal simulation model containing convective heat transfer boundary conditions, and transient simulation is performed to obtain the overall transient temperature field response curve of the turbine disk.

[0074] In a preferred embodiment, the rainflow filtering method further includes a spectrum beginning and end point supplementation step:

[0075] When the amplitudes of the first and last points in the extreme point sequence after amplitude filtering are not equal and the difference is greater than the preset tolerance, a supplementary point with an amplitude equal to that of the first point is inserted at the end of the sequence so that the spectrum forms a closure in the amplitude dimension. The tolerance is an engineering setting parameter.

[0076] In a preferred embodiment, the rainflow filtering method further includes an interpolation step:

[0077] For two adjacent points in the selected and retained extreme point sequence, if their amplitude changes in the same direction and the time interval between the two points is greater than the set interpolation threshold, then several intermediate points that conform to the changing trend are selected from the original spectrum between the two points and inserted into the extreme point sequence to form a continuous changing spectrum segment. The consistent changing direction means that the product of the difference between the amplitudes of the two adjacent points is positive.

[0078] In a preferred embodiment, the step of loading the regularized temperature spectrum and regularized rotational speed spectrum onto the finite element model of the high-pressure turbine disk of the aero-engine includes:

[0079] The regularized temperature spectrum and regularized rotational speed spectrum were loaded into a three-dimensional finite element model of the high-pressure turbine disk of the aero-engine;

[0080] In the three-dimensional finite element model, convective heat transfer boundary conditions covering the blade and disk regions are set, and the heat transfer coefficient is preset based on the engine flight conditions and cooling structure parameters.

[0081] Based on the transient heat conduction equation, the transient simulation module of the finite element analysis software is called to perform transient thermal simulation analysis according to the time step, and the transient temperature field response curve of the turbine disk as a whole is obtained.

[0082] Step 4: Analyze the transient temperature field response curve. Based on the criterion that the rate of temperature change converges to a set threshold within a continuous sampling period, identify the shortest load holding time required for the overall temperature field of the turbine disk to reach a steady state under the condition that the engine speed drops from the first value to the second value and the turbine inlet temperature drops synchronously.

[0083] In a preferred embodiment, the steps of analyzing the transient temperature field response curve and identifying the shortest holding time required for the overall turbine disk temperature field to reach a steady state under the condition that the engine speed decreases from a first value to a second value and the turbine inlet temperature decreases synchronously include:

[0084] Under the operating conditions where the speed of the aero-engine drops from the first value n1 to the second value n2 and the turbine inlet temperature drops from T1 to T2, the corresponding transient temperature field response curve is extracted.

[0085] Based on the temperature-time change trend of typical dangerous nodes in the simulation curve, the shortest response time t1 required for the overall temperature field of the turbine disk to reach thermal equilibrium is determined. The thermal equilibrium state is determined by the convergence of the temperature change rate to the threshold θ.

[0086] The shortest response time t1 is taken as the shortest load holding time under the speed reduction condition, and the corresponding time period is recorded and imported into the test spectrum data table.

[0087] The steps for determining the shortest holding time required for the overall temperature field of the turbine disk to reach a steady state include:

[0088] Select several key nodes in the temperature field response curve and calculate the rate of temperature change of each node per unit time.

[0089] A fixed simulation sampling time interval is set as the judgment period. If the temperature change rate of all key nodes is less than the preset steady-state criterion threshold in two consecutive sampling periods, then the time point is determined to be the shortest response time required to reach thermal steady state.

[0090] The steady-state criterion threshold is a temperature change limit determined based on the thermal response characteristics of the material and the engineering safety margin, preferably within the range of 0.5 to 1.5 degrees Celsius per second;

[0091] The shortest response time is used as the minimum duration standard for retaining the payload segment during the subsequent task spectrum construction process.

[0092] Step 5: Using the shortest load holding time as the control benchmark for the load holding segment, the load holding segments that do not meet the time requirement are compressed based on the equivalent lifetime conversion method of temperature and stress nonlinear coupling, and the task spectrum structure data containing the shortest load holding time are output.

[0093] In a preferred embodiment, the step of compressing the load-bearing segment that does not meet the minimum load-bearing time according to the principle of proximity equivalence includes:

[0094] The rotational speed, power, and duration parameters of each load-holding segment are statistically analyzed, and the load-holding segment with the shortest load-holding time is taken as the steady-state reference segment.

[0095] Based on the temperature, stress and load response of each segment, the thermal load of the preceding load-preserving segment is equivalently converted using the creep life conversion model to obtain the equivalent stress life value.

[0096] The conversion results are merged into the reference segment, which is retained as the reconstructed spectral structure. The original load-preserving segments that do not meet the minimum load preservation time are deleted.

[0097] In a preferred embodiment, the life calculation model includes an equivalent life calculation method that combines temperature and stress nonlinear coupling, used to determine whether multiple compression bearing segments can be replaced by a reference bearing segment. The calculation method includes the following steps:

[0098] For multiple compression load-preserving spectrum segments, extract the average temperature value and corrected thermal stress value of each spectrum segment at the critical location of the high-pressure turbine disk;

[0099] The average temperature value and the corrected thermal stress value are respectively compared with the steady-state temperature and steady-state thermal stress corresponding to the reference load-bearing segment to obtain the temperature ratio factor and the stress ratio factor respectively.

[0100] The temperature ratio factor and stress ratio factor are weighted by power by the empirically fitted first and second exponents, respectively, and multiplied by the duration of each spectral segment to obtain the equivalent lifetime contribution value of that segment.

[0101] The equivalent lifetime contribution value is accumulated according to the time series of all compression and load-preserving segments to obtain the total equivalent lifetime value of the compression segment.

[0102] In a preferred embodiment, the calculation of the equivalent lifetime total value employs a temperature-stress coupled nonlinear model, expressed as follows:

[0103]

[0104] Where: L accum This represents the cumulative life index corresponding to all compression and load-preserving sections; N represents the number of compression and load-preserving sections to be compressed; σ eq,j σ represents the creep equivalent thermal stress calculated at the critical point of the high-pressure turbine disk in the j-th compression bearing section; ref,load T represents the steady-state equivalent thermal stress of the reference load-bearing section; avg,j T represents the average temperature of the j-th compression segment; ref,load Indicates the steady-state temperature of the reference load-maintaining section; Δt j denoted as the duration of compression in segment j; α and β are the life conversion indices of stress and temperature in the creep life model, derived from the fitting of the creep life curve of high-temperature alloys;

[0105] When the calculated L accum When the lifetime target value of the compression segment is greater than or equal to that of the reference load segment, the compression segment set is determined to meet the equivalent lifetime condition and is used as a replacement spectral segment for the reference segment.

[0106] Example 2

[0107] To verify the practical engineering applicability of the method of the present invention, test spectrum data of a certain type of military aero-engine was selected as input, and the steady-state load holding time of speed reduction and spectrum compression processing were performed in combination with the simulation platform.

[0108] The measured speed and temperature spectrum of the aero-engine are as follows: Figure 2 As shown.

[0109] The aero-engine speed and temperature spectra are preprocessed using a rainflow filtering program to remove minor loads and normalize the load spectrum. The processing effect on the speed spectrum is as follows: Figure 4 , Figure 5 As shown.

[0110] As engine speed decreases, turbine inlet temperature decreases, causing the overall disk temperature to change dynamically. To determine the shortest load holding time after speed reduction, ANSYS transient thermal calculations were used to determine the shortest time required for the turbine disk to reach thermal equilibrium after each speed reduction, as shown in Table 1. The shortest retained load is as follows: Figure 6 As shown. To further construct the test spectrum for accelerated missions, the lifespan of the load-maintaining section during the test process is equivalently reduced and compressed. For example... Figure 7 As shown, this diagram illustrates the distribution of the first peak point and subsequent compressed spectral segments in the original mission spectrum. By statistically analyzing and identifying key compressed segments, a graphical basis is provided for subsequent lifetime calculations.

[0111] Table 1 shows the shortest load holding time after speed reduction in the acceleration test spectrum.

[0112] Rotational speed (r / min) Time s 32814-31156 150 31800-30692 120 30692-29945 120 32030-28844 140

[0113] Table 2 shows the statistical analysis of the state of the first peak point and the compressed spectrum in chronological order.

[0114] Table 2. Statistical analysis of the first peak point and the compressed spectrum.

[0115] Serial Number Power (KW) Rotational speed (rpm) Duration (s) First peak point 947 32814 74 1 781 31156 377 2 700 30692 656 3 589 29945 1174 4 936 32030 714

[0116] Based on the conversion principle of sustained load, the conversion results of items 1 to 3 in Table 2 to item 4 are shown in Table 3. The thermal load state is converted to the equivalent lifetime contribution of the reference segment (spectral segment 4). The conversion calculation process is as follows: Figure 3 As shown in the figure, the corrected thermal stress, life reduction factor, and reduced life time index of the critical node of the wheel under different temperature and stress conditions are listed in the figure, which serve as the basic data support for the spectral band retention and compression criteria.

[0117] Table 3. Creep Analysis and Load Calculation of the High-Pressure Stage I Disk of the Gas Turbine

[0118]

[0119] The simplified and regularized acceleration spectrum after compilation is as follows: Figure 8 As shown.

[0120] In summary, this invention addresses core issues such as thermal response hysteresis and spectral compression in high-temperature components, constructing an integrated processing flow encompassing measured spectrum preprocessing, transient thermal simulation, steady-state criterion determination, and lifespan reduction and compression. This method not only achieves quantitative identification of the steady-state time of the turbine disk temperature field under reduced speed conditions but also introduces an equivalent lifespan model coupled with temperature and stress, ensuring consistency between the compressed spectral band and the original spectral band in terms of thermal damage. The mission test spectrum constructed using this method can significantly improve test efficiency, save resources, and provide accurate and reliable engineering support for aero-engine life assessment and accelerated spectral simulation, demonstrating promising application prospects and widespread application value.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0122] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process. Furthermore, the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functionality involved.

[0123] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum, characterized in that, Includes the following steps: Obtain the measured temperature spectrum and measured speed spectrum collected during the test run of the aero-engine; The measured temperature spectrum and measured rotational speed spectrum are normalized. The normalization process includes: extracting intermediate flight segment data with peak and valley characteristics; and using a rainflow filtering method based on the maximum and minimum amplitude difference to delete small cycles and disturbance signals with amplitudes less than the set threshold. The beginning and end points of the spectrum are supplemented, and the original spectrum points are inserted in the segment with consistent trend to generate a regular temperature spectrum and a regular speed spectrum. The regular temperature spectrum and regular speed spectrum are loaded onto the finite element model of the high pressure turbine disk of the aero-engine to construct a thermal simulation model containing convective heat transfer boundary conditions, and transient simulation is performed to obtain the overall transient temperature field response curve of the turbine disk. Analyze the transient temperature field response curve and, based on the criterion that the rate of temperature change converges to a set threshold within a continuous sampling period, identify the shortest load holding time required for the overall temperature field of the turbine disk to reach a steady state under the condition that the engine speed drops from the first value to the second value and the turbine inlet temperature drops synchronously. Using the shortest load holding time as the control benchmark for the load holding segment, the load holding segments that do not meet the time requirement are compressed based on the equivalent lifetime conversion method of temperature and stress nonlinear coupling, and the task spectrum structure data containing the shortest load holding time is output.

2. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The rainflow filtering method includes the following steps: Extreme points with local extreme value characteristics are extracted from the measured speed spectrum or temperature spectrum of aero-engines and arranged in chronological order to form an extreme point sequence; Calculate the amplitude difference Δ between any two adjacent points in the extreme point sequence, and calculate the filtering threshold Δ% using the following formula: Among them: G max With G min These are the maximum and minimum amplitude values ​​in the spectral segment, respectively; if Δ is less than the absolute value corresponding to Δ%, then the pair of extreme points is deleted; the selected and retained extreme points are connected in chronological order to construct the filtered spectrum.

3. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The rainflow filtering method also includes a spectrum beginning and end point supplementation step, including: When the amplitudes of the first and last points in the extreme point sequence after amplitude filtering are not equal and the difference is greater than the preset tolerance, a spectral point with the same amplitude as the first point is inserted at the end of the sequence so that the spectral segment forms a closure in the amplitude dimension. The tolerance is an engineering setting parameter.

4. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The rainflow filtering method further includes an interpolation processing step, including: If two adjacent points in the selected and retained extreme point sequence have the same direction of amplitude change and the time interval between the two points is greater than the set interpolation threshold, then several intermediate spectral points that conform to the above trend are selected from the original spectrum between the two points and inserted into the extreme point sequence to form a continuous changing spectral segment. The same direction of change means that the product of the difference between the amplitudes of the two adjacent points is positive.

5. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The steps of loading the regularized temperature spectrum and regularized speed spectrum into the finite element model of the high-pressure turbine disk of the aero-engine include: The regularized temperature spectrum and regularized rotational speed spectrum were loaded into a three-dimensional finite element model of the high-pressure turbine disk of the aero-engine; In the three-dimensional finite element model, convective heat transfer boundary conditions covering the blade and disk regions are set, and the heat transfer coefficient is preset based on the engine flight conditions and cooling structure parameters. Based on the transient heat conduction equation, the transient simulation module of the finite element analysis software is called to perform transient thermal simulation analysis according to the time step, and the transient temperature field response curve of the turbine disk as a whole is obtained.

6. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, Analyzing the transient temperature field response curve, the steps to identify the shortest holding time required for the overall turbine disk temperature field to reach steady state under the condition that the engine speed decreases from the first value to the second value and the turbine inlet temperature decreases synchronously include: Under the operating conditions where the speed of the aero-engine drops from the first value n1 to the second value n2 and the turbine inlet temperature drops from T1 to T2, the corresponding transient temperature field response curve is extracted. Based on the temperature-time change trend of typical dangerous nodes in the simulation curve, the shortest response time t1 required for the overall temperature field of the turbine disk to reach thermal equilibrium is determined. The thermal equilibrium state is determined by the convergence of the temperature change rate to the threshold θ. The shortest response time t1 is taken as the shortest load holding time under the speed reduction condition, and the corresponding time period is recorded and imported into the test spectrum data table.

7. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 6, characterized in that, The steps for determining the shortest holding time required for the overall temperature field of the turbine disk to reach a steady state include: Select several key nodes in the temperature field response curve and calculate the rate of temperature change of each node per unit time. A fixed simulation sampling time interval is set as the judgment period. If the temperature change rate of all key nodes is less than the preset steady-state criterion threshold in two consecutive sampling periods, then the time point is determined to be the shortest response time required to reach thermal steady state. The steady-state criterion threshold is a temperature change limit determined based on the thermal response characteristics of the material and the engineering safety margin, and is in the range of 0.5 to 1.5 degrees Celsius per second. The shortest response time is used as the minimum duration standard for retaining the payload segment during the subsequent task spectrum construction process.

8. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The steps for compressing the load-holding segments that do not meet the minimum load-holding time according to the principle of proximity equivalence include: statistically analyzing the rotational speed, power, and duration parameters of each load-holding segment and taking the load-holding segment with the shortest load-holding time as the steady-state reference segment; and using the creep life conversion model to perform equivalent conversion of the thermal load of the preceding load-holding segment based on the temperature, stress, and load response corresponding to each segment, to obtain the equivalent stress life value. The conversion results are merged into the reference segment, and the segment is retained as the reconstructed spectral structure. Segments that do not meet the minimum load retention time requirement are discarded.

9. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 1, characterized in that, The life reduction model includes an equivalent life calculation method that combines the nonlinear coupling of temperature and stress, used to determine whether multiple compression bearing segments can be replaced by a reference bearing segment. The calculation method includes the following steps: For multiple compression load-preserving spectrum segments, extract the average temperature value and corrected thermal stress value of each spectrum segment at the critical location of the high-pressure turbine disk; The average temperature value and the corrected thermal stress value are respectively compared with the steady-state temperature and steady-state thermal stress corresponding to the reference load-bearing segment to obtain the temperature ratio factor and the stress ratio factor respectively. The temperature ratio factor and stress ratio factor are weighted by power by the empirically fitted first and second exponents, respectively, and multiplied by the duration of each spectral segment to obtain the equivalent lifetime contribution value of that segment. The equivalent lifetime contribution value is accumulated according to the time series of all compression and load-preserving segments to obtain the total equivalent lifetime value of the compression segment.

10. The method for determining the shortest load holding time after speed reduction in an aero-engine acceleration mission test spectrum according to claim 9, characterized in that, The calculation of the equivalent life total value adopts a temperature-stress coupled nonlinear model, and the expression is: Where: L accum This represents the cumulative life index corresponding to all compression and load-preserving sections; N represents the number of compression and load-preserving sections to be compressed; σ eq,j σ represents the creep equivalent thermal stress calculated at the critical point of the high-pressure turbine disk in the j-th compression bearing section; ref,load T represents the steady-state equivalent thermal stress of the reference load-bearing section; avg,j T represents the average temperature of the j-th compression segment; ref,load Indicates the steady-state temperature of the reference load-maintaining section; Δt j denoted as the duration of compression in segment j; α and β are the life conversion indices of stress and temperature in the creep life model, derived from the fitting of the creep life curve of high-temperature alloys; When the calculated L accum When the lifetime target value of the compression segment is greater than or equal to that of the reference load-bearing segment, the compression segment set is determined to meet the equivalent lifetime condition and is used as a typical spectral segment that meets the minimum load-bearing time.

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