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

Abstract

The invention discloses a method for determining the shortest load holding time after rotating speed reduction in an aero-engine acceleration task test run spectrum, and relates to the technical field of aero-engine load spectrums. Comprising the following steps: acquiring an actually measured temperature spectrum and a rotating speed spectrum, performing regularization processing, deleting small circulation and disturbance signals by adopting a rain flow filtering threshold value with a maximum and minimum amplitude difference, and completing spectral band head and tail point supplementation and interpolation; loading the regular spectrum into a finite element thermal simulation model of the high-pressure turbine disc, and constructing a transient thermal simulation system containing convective heat transfer boundary conditions to obtain a turbine disc temperature field response curve; according to the criterion that the temperature change rate is continuously converged to a threshold value, the shortest load holding time needed under the working condition that the rotating speed and the turbine front temperature are synchronously reduced is recognized; and a temperature-stress coupling equivalent life conversion method is adopted to compress spectrum segments which do not meet conditions, and an acceleration task test run spectrum with the shortest load holding time is generated. The method improves the damage equivalence and physical accuracy of spectrum compression, and is suitable for optimization and reconstruction of the aero-engine life test spectrum.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aero-engine load spectrum, and particularly relates to a method for determining the shortest load maintaining time after speed reduction in an aero-engine acceleration mission test spectrum. BACKGROUND

[0002] With the continuous progress of aviation technology, the service life of aero-engines has significantly increased. Currently, the design life of military aero-engines has generally reached 6000 hours, and the service life of civil aero-engines is more than 20,000 hours. In order to evaluate and verify the structural durability and failure mode of the engine during long-life service, the traditional method usually needs to carry out full-life tests. However, such tests have a long cycle and high resource consumption. It may take months to years to perform a complete full-life test, and the cost is unacceptable, which significantly restricts the development progress and iteration efficiency of new engine models. Therefore, the acceleration mission test spectrum becomes an important means to solve this problem. It can shorten the test cycle and reduce the test cost by reasonably compressing the repeated working conditions in the flight mission spectrum, and becomes a core tool in the life verification of aero-engines.

[0003] The construction of the acceleration spectrum faces many technical challenges, especially for high-pressure turbine discs and other key components at the hot end, which are in a complex thermal coupling state of high temperature and high pressure during flight. The thermal response characteristics of the speed reduction condition in the mission spectrum are particularly sensitive. The current mainstream method for constructing the acceleration spectrum usually relies on empirical equivalent models or statistical compression methods, but lacks accurate thermal response modeling in determining the load maintaining time during speed change. Especially when the engine speed suddenly drops from a high value to a lower value, the turbine front temperature also drops synchronously, and the turbine disc will experience a significant transient thermal gradient, resulting in a large thermal stress. Due to the heat lag and thermal inertia, the overall temperature field of the turbine disc needs a certain time to stabilize, and this steady-state response time has a significant impact on fatigue life and creep life.

[0004] The current technology has not fully considered how to accurately determine the shortest load maintaining time after speed reduction, especially how to correctly introduce this parameter in the acceleration mission test spectrum to ensure that the test spectrum can truly reflect the thermal-stress response of the engine under actual service conditions. Therefore, it is urgent to propose a solution that can quantitatively identify the time required for the turbine disc to reach thermal steady state, and combine the equivalent life reduction model to reasonably compress the acceleration spectrum. SUMMARY

[0005] The present application aims to provide an aero-engine acceleration task test run spectrum after the shortest holding time determination method of reducing the speed, to solve the existing acceleration task test run spectrum compilation process unable to reasonably consider the thermal steady state response of high temperature components after reducing the speed, the holding time cannot be accurately determined, and the spectrum segment compression lacks equivalent life guarantee, etc. Limitation problem, realize the quantitative identification and reasonable holding control of the turbine disc thermal steady state under the condition of reducing the speed, and then ensure that the test run spectrum still has the ability to truly reflect the service load characteristics under the acceleration condition, effectively improve the scientific nature of the spectrum segment compression and the engine test efficiency.

[0006] In order to achieve the above-mentioned purpose, the present application is realized through the following technical scheme:

[0007] An aero-engine acceleration task test run spectrum after the shortest holding time determination method of reducing the speed, comprising the following steps:

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

[0009] The measured temperature spectrum and the measured speed spectrum are normalized, and the normalization processing includes: extracting the intermediate flight segment data with peak-valley characteristics; using the rain flow filtering method based on the maximum minimum amplitude difference rain flow filtering threshold, deleting the small cycle and disturbance signal with amplitude less than the set threshold;

[0010] The first and last points of the spectrum segment are supplemented, and the original spectrum points are inserted in the consistent trend segment to generate the normalized temperature spectrum and the normalized speed spectrum;

[0011] Load the normalized temperature spectrum and the normalized speed spectrum on the high-pressure turbine disc finite element model of the aero-engine, build a thermal simulation model containing convective heat transfer boundary conditions, and perform transient simulation to obtain the overall transient temperature field response curve of the turbine disc;

[0012] Analyze the transient temperature field response curve, and according to the criterion that the temperature change rate converges to the set threshold in the continuous sampling period, identify the shortest holding time required for the overall temperature field of the turbine disc to reach steady state under the condition that the engine speed is reduced from a first value to a second value and the turbine front temperature is synchronously reduced;

[0013] Take the shortest holding time as the holding segment control reference, compress the holding segment that does not meet the time based on the equivalent life conversion method of temperature and stress nonlinear coupling, and output the task spectrum structure data containing the shortest holding time.

[0014] Further improvement of the present application is that the rain flow filtering method comprises the following steps:

[0015] Extract the extreme value points with local extreme value characteristics from the measured speed spectrum or temperature spectrum of the aero-engine, and arrange them in time sequence to form an extreme value point sequence;

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

[0017]

[0018] Wherein: G max And G min The maximum amplitude and the minimum amplitude in the spectrum segment respectively; if Δ is less than the absolute value corresponding to Δ%, the pair of extreme points is deleted; the screened extreme points are connected in time sequence to construct a filtered spectrum.

[0019] Further improvement of the application is that the rainflow filtering method further comprises a spectrum head and tail supplement point processing step:

[0020] When the amplitude of the first point and the amplitude of the last point in the extreme point sequence screened by amplitude are not equal, and the difference is greater than the preset tolerance, a supplement point with an amplitude equal to the first point is inserted at the end of the sequence, so that the spectrum segment forms a closed loop in the amplitude dimension, wherein the tolerance is an engineering set parameter.

[0021] Further improvement of the application is that the rainflow filtering method further comprises an interpolation processing step:

[0022] For the adjacent two points in the screened extreme point sequence, if the amplitude change direction is consistent, and the time interval between the two points is greater than the set interpolation threshold, a plurality of intermediate points conforming to the change trend are selected from the original spectrum between the two points and inserted into the extreme point sequence to form a continuously changing spectrum segment, wherein the consistent change direction means that the product of the amplitude difference of the adjacent two points is positive.

[0023] Further improvement of the application is that the step of loading the normalized temperature spectrum and the normalized speed spectrum on the finite element model of the high-pressure turbine disc of the aero-engine comprises:

[0024] The normalized temperature spectrum and the normalized speed spectrum are loaded into the three-dimensional finite element model of the high-pressure turbine disc of the aero-engine;

[0025] The convection heat transfer boundary condition covering the blade and the disc area is set in the three-dimensional finite element model, and the heat transfer coefficient is preset according to the engine flight condition and the cooling structure parameter;

[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 to obtain the transient temperature field response curve of the turbine disc as a whole.

[0027] The further improvement of the application is that the step of analyzing the transient temperature field response curve and identifying the shortest holding time required for the turbine disc overall temperature field to reach a steady state in the working condition where the engine speed decreases from a first value to a second value and the temperature before the turbine synchronously decreases comprises:

[0028] In the working condition where the aero-engine speed decreases from a first value n1 to a second value n2 and the temperature before the turbine decreases from T1 to T2, a corresponding transient temperature field response curve is extracted;

[0029] Based on the temperature-time variation trend of the typical dangerous node in the simulation curve, the shortest response time t1 required for the turbine disc overall temperature field to reach a thermal equilibrium state is judged, and the thermal equilibrium state is judged by the convergence of the temperature variation rate to a threshold value θ;

[0030] The shortest response time t1 is taken as the shortest holding time in the speed decreasing condition, the corresponding time period is recorded and is integrated into a test run spectrum data table.

[0031] The further improvement of the application is that the step of judging the shortest holding time required for the turbine disc overall temperature field to reach a steady state comprises:

[0032] In the temperature field response curve, a plurality of key nodes are selected, and the temperature variation rate of each node per unit time is calculated;

[0033] A fixed simulation sampling time interval is set as a judgment period, and if the temperature variation rates of all the key nodes in two consecutive sampling periods are all less than a preset steady state criterion threshold value, then the time point is judged as the shortest response time required to reach a thermal steady state;

[0034] The steady state criterion threshold value is a temperature variation limit value determined according to the thermal response characteristics of the material and the engineering safety margin, and is preferably in the range of 0.5 to 1.5 degrees Celsius per second;

[0035] The shortest response time is taken as the minimum duration standard of the holding period reserved in the subsequent task spectrum construction process.

[0036] The further improvement of the application is that the step of compressing the holding period that does not meet the shortest holding time according to the nearest equivalent principle comprises:

[0037] The speed, power and duration parameters of each holding period are counted, and the holding period with the shortest holding time is taken as a steady state reference period;

[0038] According to the temperature, stress and load response corresponding to each period, a persistent creep life reduction model is used to equivalently reduce the thermal load of the previous holding period, and an equivalent stress life value is obtained;

[0039] The converted result is combined into the reference section, the section is reserved as a reconstructed spectrum structure, and the original holding section that does not meet the shortest holding time is deleted.

[0040] A further improvement of the application is that the life conversion model comprises an equivalent life calculation method combining the nonlinear coupling of temperature and stress, which is used to determine whether a plurality of compressed holding sections can be replaced by a reference holding section, and the calculation method comprises the following steps:

[0041] For a plurality of compressed holding spectrum sections, the average temperature value and the corrected thermal stress value at the dangerous part of the high-pressure turbine disc of each spectrum section are extracted;

[0042] The average temperature value and the corrected thermal stress value are respectively calculated by the ratio of the corresponding steady-state temperature and the steady-state thermal stress of the reference holding section, and the temperature ratio factor and the stress ratio factor are respectively obtained;

[0043] The temperature ratio factor and the stress ratio factor are respectively weighted by the first exponential and the second exponential fitted by experience, and multiplied by the duration of each spectrum section to obtain the equivalent life contribution value of the section;

[0044] The equivalent life contribution value is accumulated according to the time sequence of all compressed holding sections to obtain the equivalent life conversion total value of the compressed section.

[0045] A further improvement of the application is that the equivalent life conversion total value is calculated by using a temperature and stress coupling nonlinear model, and the expression is:

[0046]

[0047] Wherein, L accum represents the accumulated life index corresponding to all compressed holding sections; N represents the number of compressed holding sections; σ eq,j represents the creep equivalent thermal stress of the jth compressed holding section at the dangerous point of the high-pressure turbine disc; σ ref,load represents the steady-state equivalent thermal stress of the reference holding section; T avg,j represents the average temperature of the jth compressed section; T ref,load represents the steady-state temperature of the reference holding section; Δt j represents the duration of the jth compressed section; α and β are respectively the life conversion indexes of stress and temperature in the creep life model, which are derived from the fitting of the high-temperature alloy creep life curve;

[0048] When the calculated L accum is greater than or equal to the life target value of the reference holding section, it is determined that the compressed section set meets the equivalent life condition and is used as a replacement spectrum section of the reference section.

[0049] The beneficial effects of the present application are: the present application carries out normalization processing on the measured temperature spectrum and the measured rotating speed spectrum collected in the aero-engine test run process, adopts the rain flow filtering method based on the rain flow filtering threshold of the maximum minimum amplitude difference, effectively identifies and eliminates small cycles and disturbance signals, and ensures that the extracted spectrum segment has representativeness and stability. In combination with the head and tail supplement point of the spectrum segment and the trend consistent interpolation processing, the normalized temperature spectrum and the normalized rotating speed spectrum which can truly reflect the working condition change in the flight stage are generated, and the physical authenticity of the spectrum data input is improved. On this basis, the high-pressure turbine disc finite element thermal simulation model containing the convection heat transfer boundary condition is constructed, and the transient simulation analysis is carried out, and the overall transient temperature field response curve of the turbine disc is obtained, which provides quantitative basis for the thermal dynamic evolution in the process of rotating speed reduction. The present application further accurately captures the shortest response time required for the overall temperature field of the turbine disc to reach the thermal steady state under the condition that the engine rotating speed decreases from high value to low value and the temperature before the turbine simultaneously decreases, solves the technical short board that the traditional acceleration task test spectrum cannot scientifically consider the thermal hysteresis and steady state identification. By setting the temperature change rate convergence criterion, the quantitative determination of the shortest load holding time is realized, and the spectrum segment that does not meet the steady state condition is subjected to equivalent life compression by taking the time as the compression control reference and using the equivalent life folding method of temperature and stress nonlinear coupling. In the spectrum segment compression process, the fitting relationship of the reference temperature-stress curve and the equivalent approximation principle are further ensured to ensure that the acceleration spectrum structure meets the equivalent damage criterion while maintaining the real working condition simulation capability of the key components at the hot end. The steady state load holding time determination and spectrum segment compression method proposed by the present application fully considers the thermal inertia and heat transfer hysteresis effect caused by the sudden drop of the engine rotating speed in operation, solves the engineering pain point that the traditional spectrum segment compression cannot guarantee the consistency of damage equivalence and thermal steady state, ensures the accuracy of life estimation and the consistency of thermal stress response, improves the scientificity, implementability and engineering practical value of the task spectrum construction, and provides reliable technical support for the life evaluation and acceleration test of the aero-engine. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0051] Among them:

[0052] Figure 1 The method flowchart of the present application;

[0053] Figure 2 The measured rotating speed temperature spectrum of a certain type of engine in the embodiment of the present application;

[0054] Figure 3 The measured power spectrum of a certain type of engine in the embodiment of the present application;

[0055] Figure 4 The normalized speed spectrum in the embodiment of the present application;

[0056] Figure 5 The normalized temperature spectrum in the embodiment of the present application;

[0057] Figure 6 The shortest load holding time after the speed reduction of an aero-engine in the embodiment of the present application for compiling the acceleration task test spectrum;

[0058] Figure 7 The compression load for compiling the acceleration task test spectrum in the embodiment of the present application;

[0059] Figure 8 The acceleration task test spectrum considering the shortest load holding time after the speed reduction of an aero-engine in the embodiment of the present application. DETAILED DESCRIPTION

[0060] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0061] Embodiment 1

[0062] As shown in Figure 1 , one embodiment of the present application provides a method for determining the shortest load holding time after the speed reduction in an acceleration task test spectrum of an aero-engine, comprising:

[0063] Step 1: obtaining the measured temperature spectrum and the measured speed spectrum collected in the test process of the aero-engine;

[0064] Step 2: performing normalization processing on the measured temperature spectrum and the measured speed spectrum, the normalization processing comprising: extracting the intermediate flight segment data with peak-valley characteristics; using a rain flow filtering method based on the rain flow filtering threshold of the maximum-minimum amplitude difference to delete small cycles and disturbance signals with an amplitude less than a set threshold;

[0065] In a preferred embodiment, the rain flow filtering method comprises the following steps:

[0066] Extracting extreme points with local extreme characteristics from the measured speed spectrum or temperature spectrum of the aero-engine, and arranging the extreme points in time sequence to form an extreme point sequence;

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

[0068]

[0069] Wherein: G max and G min are the maximum amplitude and the minimum amplitude in the spectrum segment respectively; if Δ is less than the absolute value corresponding to Δ%, the pair of extreme points is deleted; the remaining extreme points are connected in time sequence to construct a filtered spectrum.

[0070] As can be seen, the embodiment introduces a rainflow filtering threshold calculation method based on the maximum and minimum amplitude difference, which realizes the accurate elimination of small perturbations and invalid cycles on the basis of traditional filtering processing, significantly improves the accuracy and engineering adaptability of the measured spectrum regularization. Compared with the existing methods relying on empirical filtering or fixed threshold, the embodiment introduces an adjustable filtering factor and calculates the filtering threshold based on the full spectrum characteristics, so that the filtering process has stronger adaptability and physical rationality.

[0071] In addition, the filtering process combines the extreme point sequence analysis to construct a spectrum segment structure consistent with the original spectrum trend, avoiding the load distortion problem caused by spectrum compression, and providing a reliable data basis for subsequent transient thermal simulation and shortest load retention time calculation. Therefore, the embodiment not only realizes the automation and parameterization of the rainflow filtering process, but also provides high-quality spectrum input for subsequent turbine thermal load analysis, which has significant engineering promotion value and application prospect.

[0072] Step 3: Perform head-tail point filling on both ends of the spectrum segment, and insert the original spectrum points in the consistent trend segment to generate a regular temperature spectrum and a regular speed spectrum;

[0073] Load the regular temperature spectrum and the regular speed spectrum into the finite element model of the high-pressure turbine disc of the aero-engine, construct a thermal simulation model containing convective heat transfer boundary conditions, and perform transient simulation to obtain the overall transient temperature field response curve of the turbine disc;

[0074] In a preferred embodiment, the rainflow filtering method further includes a spectrum head-tail point filling step:

[0075] When the amplitude of the first point and the amplitude of the last point in the amplitude-screened extreme point sequence are not equal, and the difference is greater than a preset tolerance, a filling point with an amplitude equal to the first point is inserted at the end of the sequence, so that the spectrum segment is closed in the amplitude dimension, wherein the tolerance is an engineering set parameter.

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

[0077] For the adjacent two points in the sequence of the screened extreme value points, if the amplitude variation direction is consistent and the time interval between the two points is greater than the set interpolation threshold, then a plurality of intermediate points in the original spectrum which are consistent with the variation trend are selected and inserted into the sequence of the extreme value points to form a continuously varying spectrum segment, wherein the consistent variation direction means that the product of the amplitude difference of the adjacent two points is positive.

[0078] In a preferred embodiment, the step of loading the normalized temperature spectrum and the normalized rotation speed spectrum to the finite element model of the high-pressure turbine disk of the aero-engine comprises:

[0079] loading the normalized temperature spectrum and the normalized rotation speed spectrum to the three-dimensional finite element model of the high-pressure turbine disk of the aero-engine;

[0080] setting a convective heat transfer boundary condition covering the blade and disk area in the three-dimensional finite element model, and the heat transfer coefficient is preset according to the engine flight condition and the cooling structure parameter;

[0081] based on the transient heat conduction equation, calling the transient simulation module of the finite element analysis software to perform transient thermal simulation analysis by time step to obtain the transient temperature field response curve of the turbine disk as a whole.

[0082] Step 4: analyzing the transient temperature field response curve, and identifying the shortest holding time required for the turbine disk overall 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 pre-temperature decreases synchronously according to the criterion that the temperature change rate converges to a set threshold within a continuous sampling period;

[0083] In a preferred embodiment, the step of analyzing the transient temperature field response curve to identify the shortest holding time required for the turbine disk overall 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 pre-temperature decreases synchronously comprises:

[0084] extracting the corresponding transient temperature field response curve under the condition that the aero-engine speed decreases from a first value n1 to a second value n2 and the turbine pre-temperature decreases from T1 to T2;

[0085] based on the temperature-time variation trend of the typical dangerous node in the simulation curve, judging the shortest response time t1 required for the turbine disk overall temperature field to reach a thermal equilibrium state, and the thermal equilibrium state is determined by the convergence of the temperature change rate to a threshold θ;

[0086] taking the shortest response time t1 as the shortest holding time under the speed decreasing condition, recording the corresponding time period and integrating into the test run spectrum data table.

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

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

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

[0090] The steady-state criterion threshold is a temperature change limit value determined according to the thermal response characteristics of the material and the engineering safety margin, preferably in 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 holding section in the subsequent task spectrum construction process.

[0092] Step 5: Use the shortest holding time as the holding section control reference, compress the holding section that does not meet the time based on the equivalent life conversion method of temperature and stress nonlinear coupling, and output the task spectrum structure data containing the shortest holding time.

[0093] In a preferred embodiment, the step of compressing the holding section that does not meet the shortest holding time according to the nearest equivalent principle includes:

[0094] Statistical parameters of rotational speed, power and duration of each holding section, and the shortest holding time holding section as a steady-state reference section;

[0095] According to the temperature, stress and load response corresponding to each section, the equivalent stress life value is obtained by using the creep life conversion model to equivalently convert the thermal load of the previous holding section;

[0096] The conversion results are combined into the reference section to retain the section as the reconstructed spectrum structure, and the original holding section that does not meet the shortest holding time is deleted.

[0097] In a preferred embodiment, the life conversion model includes an equivalent life calculation method combining temperature and stress nonlinear coupling, which is used to determine whether multiple holding sections to be compressed can be replaced by a reference holding section. The calculation method includes the following steps:

[0098] For multiple holding spectrum sections to be compressed, extract the average temperature value and the corrected thermal stress value at the dangerous part of the high-pressure turbine disc of each spectrum section;

[0099] Calculate the ratio of the average temperature value and the corrected thermal stress value to the steady-state temperature and the steady-state thermal stress corresponding to the reference holding section, respectively, to obtain the temperature ratio factor and the stress ratio factor;

[0100] The temperature ratio factor and the stress ratio factor are respectively power-weighted by the first and second exponential functions of empirical fitting, and multiplied by the duration of each spectrum segment to obtain the equivalent life contribution value of the segment;

[0101] The equivalent life contribution values are accumulated in the time sequence of all compression storage segments to obtain the equivalent life conversion total value of the compression segment.

[0102] In a preferred embodiment, a temperature-stress coupled nonlinear model is used in the calculation of the equivalent life conversion total value, and the expression is:

[0103]

[0104] Wherein: L accum represents the accumulated life index corresponding to all compression storage segments; N represents the number of compression storage segments to be compressed; σ eq,j represents the creep equivalent thermal stress at the dangerous point of the high-pressure turbine disc calculated for the jth compression storage segment; σ ref,load represents the steady-state equivalent thermal stress of the reference storage segment; T avg,j represents the average temperature of the jth compression segment; T ref,load represents the steady-state temperature of the reference storage segment; Δt j represents the compression duration of the jth segment; α and β are the life conversion exponents of stress and temperature in the creep life model, respectively, and are derived from the fitting of the high-temperature alloy creep life curve;

[0105] When the calculated L accum is greater than or equal to the life target value of the reference storage segment, it is determined that the compression segment set meets the equivalent life condition and is used as a replacement spectrum segment for the reference segment.

[0106] Example 2

[0107] To verify the practical engineering applicability of the method, the test run spectrum data of a certain type of military aviation engine were selected as input, and the simulation platform was used to calculate the steady-state storage time at reduced speed and to process the spectrum compression.

[0108] The actual measured aviation engine speed and temperature spectrum are shown in Figure 2 .

[0109] The rain flow filtering program was used to pretreat the aviation engine speed and temperature spectrum, and small loads were deleted, and the load spectrum was regularized. The processing effect of the speed spectrum is shown in Figure 4 , Figure 5 .

[0110] According to the engine speed reduction, the turbine temperature decreases, and the disc overall temperature is dynamically changed. To determine the shortest load retention time after speed reduction, ANSYS transient heat calculation is used to calculate the shortest time required for the turbine disc overall to reach thermal equilibrium after each speed reduction. The shortest load retention is shown in Table 1. Figure 6 To further construct the accelerated task test spectrum, the load retention section in the test process is life equivalent and compressed. As shown in Figure 7 , the first peak point in the original task spectrum and the subsequent compressed spectrum distribution are shown. Through statistics and identification of the key compression section, graphical basis is provided for subsequent life conversion.

[0111] Table 1 Shortest load retention time after speed reduction in accelerated task test spectrum

[0112] Rpm Time s 32814-31156 150 31800-30692 120 30692-29945 120 32030-28844 140

[0113] In chronological order, the state of the first peak point and the compressed spectrum is counted as shown in Table 2.

[0114] Table 2 Load state statistics of the first peak point and the compressed spectrum

[0115] Serial number Power (KW) 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] According to the conversion principle of the permanent load, the 1-3 in Table 2 is converted to the 4th conversion result. The thermal load state is converted to the life contribution equivalent to the reference section (spectrum section 4). The conversion calculation process is shown in Figure 3 . The modified thermal stress, life conversion coefficient and converted life time index of the disc dangerous node under different temperature and stress conditions are listed in the figure, which are the basic data support for the spectrum section retention and compression criterion.

[0117] Table 3 Creep analysis and load conversion of gas turbine high pressure I stage disc

[0118]

[0119] The simplified accelerated spectrum after programming is shown in Figure 8 .

[0120] In summary, the application builds an integrated processing flow covering measured spectrum preprocessing, transient thermal simulation, steady-state criterion determination and life reduction compression around the core problems of high-temperature component thermal response hysteresis and spectrum compression. This method not only realizes the quantitative identification of the steady-state time of the turbine disc temperature field under the condition of speed reduction, but also introduces an equivalent life model of temperature-stress coupling to ensure that the compressed spectrum has consistency with the original spectrum in terms of thermal damage. The task test spectrum constructed by this method can significantly improve the test efficiency, save resources, and provide accurate and reliable engineering support for aero-engine life evaluation and spectrum acceleration simulation, and has good application prospect and popularization value.

[0121] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0122] Any process or method descriptions in flow charts or described elsewhere herein can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for performing specific logic functions or steps in the process. And the scope of preferred embodiments of the present application includes additional implementation in which the functions are performed in different orders, including substantially simultaneously, or in reverse order, according to the functions involved.

[0123] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for determining the shortest hold time after speed reduction in an aircraft engine acceleration mission test spectrum, characterized in that: The steps include: Obtain the measured temperature spectrum and speed spectrum collected during the aircraft engine test; Regularization processing is performed on the measured temperature spectrum and the measured speed spectrum, the regularization processing comprising: extracting data of the intermediate flight segment having peak and valley characteristics; using a rain flow filtering method based on a rain flow filtering threshold value of a maximum and minimum amplitude difference to delete small cycles and disturbance signals with amplitudes less than a set threshold; Adding points at both ends of the spectrum segment and inserting the original spectrum points into the segment with consistent trends to generate a regular temperature spectrum and a regular speed spectrum; loading the regular temperature spectrum and regular speed spectrum into a finite element model of a high-pressure turbine disk of an aircraft engine, constructing a thermal simulation model including convective heat transfer boundary conditions, and performing transient simulation to obtain the overall transient temperature field response curve of the turbine disk; Analyzing the transient temperature field response curve and, based on the criterion that the temperature change rate converges to a set threshold within a continuous sampling period, identifying the shortest dwell time required for the overall temperature field of the turbine disk to reach a steady state under the operating conditions where the engine speed decreases from a first value to a second value and the turbine front temperature decreases simultaneously; The shortest holding time is used as the control benchmark for the holding segment, and the holding segments that do not meet the time are compressed based on the equivalent life conversion method of nonlinear coupling of temperature and stress, and the mission spectrum structure data containing the shortest holding time is output.

2. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The rainflow filtering method comprises the following steps: Extracting extreme points with local extreme value characteristics from the measured speed spectrum or temperature spectrum of the aircraft engine and arranging them in chronological order to form an extreme point sequence; Calculate the amplitude difference Δ for any two adjacent points in the extreme point sequence, and calculate the filtering threshold Δ% according to the following formula: Among them: G max With G min are the maximum and minimum amplitudes in the spectrum segment respectively; if Δ is less than the absolute value corresponding to Δ%, the pair of extreme points is deleted; the extreme points retained by the screening are connected in chronological order to construct a filtered spectrum.

3. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The rainflow filtering method further includes a spectrum beginning and end point filling processing step including: When the amplitudes of the first and last points in the extreme point sequence after amplitude screening are not equal, and the difference is greater than the preset tolerance, a spectrum point with the same amplitude as the first point is inserted at the end of the sequence to close the spectrum segment in the amplitude dimension, where the tolerance is a project setting parameter.

4. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The rain flow filtering method further includes an interpolation processing step comprising: For two adjacent points in the retained extreme point sequence, if their amplitude change directions are consistent and the time interval between the two points is greater than the set interpolation threshold, several intermediate spectrum points that meet the above change trend are selected from the original spectrum between the two points and inserted into the extreme point sequence to form a continuously changing spectrum segment. The consistent change direction means that the product of the difference between the amplitudes of the two adjacent points is positive.

5. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The step of loading the regular temperature spectrum and the regular speed spectrum onto a finite element model of a high-pressure turbine disk of an aircraft engine comprises: Loading the regular temperature spectrum and the regular speed spectrum into a three-dimensional finite element model of an aircraft engine high-pressure turbine disk; Setting convective heat transfer boundary conditions covering the blade and disk area in the three-dimensional finite element model, wherein 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 to obtain the transient temperature field response curve of the entire turbine disk.

6. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The step of analyzing the transient temperature field response curve to identify the shortest dwell time required for the overall temperature field of the turbine disk to reach a steady state under the operating condition where the engine speed decreases from a first value to a second value and the temperature before the turbine decreases simultaneously comprises: Under the operating conditions where the aircraft engine speed drops from a first value n1 to a 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 variation 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 the thermal equilibrium state is determined. The thermal equilibrium state is determined by the temperature change rate converging to the threshold value θ; The shortest response time t1 is used as the shortest load holding time under the speed reduction condition, and the corresponding time period is recorded and entered into the test spectrum data table.

7. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 6, characterized in that: The step of determining the shortest dwell time required for the overall temperature field of the turbine disk to reach a steady state comprises: Select several key nodes in the temperature field response curve and calculate the temperature change rate 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 in two consecutive sampling periods is less than the preset steady-state judgment threshold, the time point is determined to be the shortest response time required to achieve thermal steady-state. The steady-state judgment threshold is a temperature change limit determined based on the thermal response characteristics of the material and the engineering safety margin, and is within 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 load-holding segment during the subsequent task spectrum construction process.

8. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The steps of compressing the holding sections that do not meet the shortest holding time according to the nearest equivalent principle include: calculating the speed, power, and duration parameters of each holding section and using the holding section with the shortest holding time as a steady-state reference section; and using a creep life conversion model to convert the thermal load of the preceding holding section into an equivalent value based on the temperature, stress, and load response of each section to obtain an equivalent stress-life value. The converted results are merged into the reference segment to retain the segment as the reconstructed spectrum structure, and the holding segments that do not meet the shortest holding time requirement are discarded.

9. The method for determining the shortest dwell time after speed reduction in an aircraft engine acceleration mission test spectrum according to claim 1, characterized in that: The life reduction model includes an equivalent life calculation method that combines nonlinear coupling of temperature and stress, and is used to determine whether multiple to-be-compressed load-holding sections can be replaced by reference load-holding sections. The calculation method includes the following steps: For multiple load-keeping spectrum segments to be compressed, extract the average temperature value and corrected thermal stress value at the dangerous part of the high-pressure turbine disc of each spectrum segment; Calculate the ratio of the average temperature value and the corrected thermal stress value to the steady-state temperature and steady-state thermal stress corresponding to the reference load-holding section, respectively, to obtain a temperature ratio factor and a stress ratio factor; The temperature ratio factor and stress ratio factor are weighted by the first exponent and the second exponent respectively according to the empirical fitting, and multiplied by the duration of each spectrum segment to obtain the equivalent life contribution value of the segment; The equivalent life contribution values ​​are accumulated according to the time series of all compression and load-holding sections to obtain the total equivalent life conversion value of the compression section.

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

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