A method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum

Abstract

The present invention discloses a method for extracting creep loads and determining the distribution law in an aircraft engine load spectrum, which includes the following steps: Step S1, equally divide the flight mission profile to obtain a load spectrum with each having the same duration t0; Step S2, based on the creep load judgment criterion, extract the creep loads to obtain a creep load spectrum; Step S3, based on the creep load spectrum obtained in Step S2 that meets the creep load judgment criterion, construct a duration - rotational speed - temperature fitting curve graph to obtain the creep load distribution law. The creep load extraction of the present invention has a more scientific basis and is more applicable to the creep load extraction of the actual aircraft engine load spectrum and the research on the random distribution law of creep loads.

Description

Technical Field

[0001] The present invention belongs to the field of aero-engine load spectra, and particularly relates to a method for extracting creep loads and determining the distribution law of aero-engine load spectra. Background Art

[0002] For key components such as aero-engine turbine blades, disks, and nozzle rings, they often suffer from the influence of variable-temperature and variable-load creep loads, and finally creep damage occurs, leading to fracture. The creep loads they bear have a large amount of randomness, that is, the three creep parameters of temperature, stress, and duration have strong randomness. In order to accurately evaluate the structural damage caused by creep loads, it is necessary to carry out research on the influence law of creep load randomness on structural damage. In order to carry out the research, it is necessary to provide an effective method for extracting creep loads and determining the distribution law. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for extracting creep loads and determining the distribution law in an aero-engine load spectrum, so as to convert the original load spectrum into a creep spectrum and study the creep load distribution law.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for extracting creep loads and determining the distribution law in an aero-engine load spectrum includes the following steps:

[0006] Step S1: Divide the flight mission profile equally to obtain a load spectrum with each part having the same duration t0;

[0007] Step S2: Based on the creep load judgment criterion, extract the creep loads to obtain a creep load spectrum;

[0008] Step S3: Based on the creep load spectrum obtained in Step S2 that meets the creep load judgment criterion, construct a duration-rotation speed-temperature fitting curve graph to obtain the creep load distribution law.

[0009] In the above Step 1, each load spectrum includes a rotation speed spectrum and an engine temperature spectrum.

[0010] In the above Step 1, t0 = 100 s.

[0011] The specific steps of step S2 are as follows: If the equal part meets the creep load judgment criterion, regard this equal part as the creep load, and record it as unit 1. Calculate the average values of the rotational speed and gas temperature in this equal part, and store them in arrays N2 and T4 respectively. The duration is recorded as t0. If this equal part does not meet the creep load judgment criterion, continue to divide the equal part that does not meet the judgment criterion, and obtain a load spectrum with each equal part having the same duration t1. Then judge this equal part again. If it meets the creep load judgment criterion, also regard this equal part as the creep load, and record it as unit 1. Calculate the average values of the rotational speed and gas temperature in this equal part, and store them in arrays N2 and T4 respectively. The duration is recorded as t1.

[0012] In step 2, t1 = 10s.

[0013] In step S2, the creep load judgment criterion is as follows:

[0014] a. Calculate the standard deviation and average value of the rotational speed and temperature in each equal part, and divide the standard deviation by the average value to obtain the coefficient of variation of the rotational speed and temperature in each equal part.

[0015] b. Calculate the difference between the maximum value and the minimum value of the rotational speed and temperature in each equal part, and divide the difference by the average value to obtain the maximum coefficient of variation measurement criterion in each equal part.

[0016] c. Judge whether the coefficient of variation of the rotational speed and temperature in each equal part is less than 0.5%; judge whether the maximum coefficient of variation measurement criterion in each equal part is less than 2.5%; if both meet the less-than conditions, extract it as the creep load.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0018] (1) In the method of the present invention, only the specific data of the original load spectrum need to be known. Relying on programming software and according to the judgment criterion, it is simple to implement, intuitive in performance, and low in cost.

[0019] (2) The method of the present invention uses the coefficient of variation and extracts the creep load based on the influence of the average value of the discrete degree of load data.

[0020] (3) The method of the present invention can be applied to materials such as common metals and alloys in engineering, has strong applicability, and has extremely strong popularization. Description of the Drawings

[0021] Figure 1 is the implementation flowchart of the present invention;

[0022] Figure 2 is the original flight mission profile of a certain civil turboshaft engine;

[0023] Figure 3It is a schematic diagram of the local (first 100 seconds) of the engine flight mission profile;

[0024] Figure 4 It is a schematic diagram of the load spectrum with the smallest equal parts;

[0025] Figure 5 It is a schematic diagram of the creep load extracted according to the creep load judgment standard;

[0026] Figure 6 It is a fitting diagram of the creep load distribution law. Specific implementation mode

[0027] The present invention will be further explained below with reference to the accompanying drawings.

[0028] During the actual flight process, the load spectrum of an aeroengine is a typical random load spectrum, and there are a large number of creep loads. Therefore, the present invention proposes a method with clear logic and orderly steps, which can simply and accurately extract the creep loads in the aeroengine load spectrum and study the distribution law after use.

[0029] As Figure 1 shown, a method for extracting creep loads and determining distribution laws in the load spectrum of an aeroengine according to the present invention includes the following steps:

[0030] Step S1: Divide the flight mission profile equally to obtain a load spectrum with each having the same duration t0 = 100s. Each load spectrum includes a rotational speed spectrum and an engine temperature spectrum; store each rotational speed spectrum in the first column of the array N2 in units of 100s in chronological order, and store each gas temperature spectrum in the first column of the array T4 in units of 100s in chronological order;

[0031] Step S2: Calculate the average value, the difference between the maximum value and the minimum value, and the standard deviation of each rotational speed and temperature data respectively. Divide the standard deviation by the average value to obtain the coefficient of variation CV1-N2 of the rotational speed and the coefficient of variation CV1-T4 of the temperature for each part respectively. Divide the difference between the maximum value and the minimum value by the average value to obtain the maximum coefficient of variation measurement standard CV2-N2 of the rotational speed and the coefficient of variation CV2-T4 of the temperature for each part respectively;

[0032] Judge the coefficient of variation and the maximum coefficient of variation measurement standard of each rotational speed and temperature:

[0033] If the coefficient of variation of the rotational speed and temperature of this portion is simultaneously less than 0.5%, and the maximum coefficient of variation measurement standard is simultaneously less than 2.5%, then this portion of the load spectrum meets the judgment criteria for creep load. Consider this portion as creep load and denote it as unit 1. Unit 1 is stored in the second column of arrays N2 and T4. The average values of the rotational speed and temperature of this portion are regarded as the creep load data of this portion and are stored in the third column of arrays N2 and T4 in chronological order respectively. The duration of the rotational speed and temperature is denoted as t0 = 100s and is stored in the fourth column of arrays N2 and T4 respectively;

[0034] Otherwise, continue to divide the portions that do not meet the judgment criteria equally to obtain a load spectrum with each portion having the same duration t1 = 10s. Conduct the same judgment as described above for this portion. If it meets the creep load criteria, also consider this portion as creep load and denote it as unit 1, which is stored in the second column of arrays N2 and T4. The average values of the rotational speed and temperature of this portion are also regarded as the creep load data of this portion and are stored in the third column of arrays N2 and T4 in chronological order respectively. The duration is denoted as t1 = 10s and is stored in the fourth column of arrays N2 and T4 respectively;

[0035] After judging each portion of the load spectrum based on the proposed creep load judgment criteria, extract the creep load of the aero-engine load spectrum. The rotational speed and gas temperature of the original load spectrum data are stored in the first column of N2 and T4, the creep load data is stored in the third column of N2 and T4, and the durations of different values of creep load are stored in the fourth column of N2 and T4. Thus, draw the original load spectrum and the creep load spectrum of this mission profile, with time as the horizontal axis and rotational speed and time as the vertical axis.

[0036] Step S3: Based on the creep load spectrum that meets the creep load criteria obtained in step S2, construct a duration-rotational speed-temperature fitting curve graph to obtain the creep load distribution law.

[0037] The following further illustrates the present invention according to specific embodiments.

[0038] Embodiment

[0039] The process of extracting the creep load and determining the distribution law of the load spectrum of a certain type of engine:

[0040] As Figure 2 shown is the load spectrum of a certain type of aero-engine. This load spectrum has a total of 5945 sampling points, and the sampling frequency is 1HZ.

[0041] (1) Divide the flight mission profile equally to obtain a load spectrum with each portion having the same duration t0 = 100s. Each portion of the load spectrum includes a rotational speed spectrum and an engine temperature spectrum, Figure 2This is the first load spectrum, and a total of 59 load spectra are finally obtained. Each rotational speed spectrum is stored in the first column of array N2 in chronological order in units of 100 s, and each gas temperature spectrum is stored in the first column of array T4 in chronological order in units of 100 s.

[0042] (2) Calculate the average value, the difference between the maximum and minimum values, and the standard deviation for each set of rotational speed and temperature data respectively.

[0043] Divide the standard deviation by the average value to obtain the coefficient of variation CV1-N2 of rotational speed and the coefficient of variation CV1-T4 of temperature for each part respectively. Divide the difference between the maximum and minimum values by the average value to obtain the maximum coefficient of variation measurement standard CV2-N2 of rotational speed and the maximum coefficient of variation measurement standard CV2-T4 of temperature for each part respectively.

[0044] Judge the coefficient of variation and the maximum coefficient of variation measurement standard for each set of rotational speed and temperature:

[0045] If the coefficients of variation of rotational speed and temperature for this part are both less than 0.5%, and the maximum coefficient of variation measurement standards are both less than 2.5%, then this load spectrum meets the judgment criteria for creep load. Consider this part as creep load and record it as unit 1. Unit 1 is stored in the second column of arrays N2 and T4. The average values of rotational speed and temperature for this part are regarded as the creep load data for this part and are stored in the third column of arrays N2 and T4 in chronological order respectively. The duration of rotational speed and temperature is recorded as t0 = 100 s and is stored in the fourth column of arrays N2 and T4 respectively.

[0046] Table 1 Data and data processing of the first load spectrum

[0047]

[0048]

[0049]

[0050] The coefficients of variation of rotational speed and temperature for the first load spectrum are 1.610435% and 1.373522% respectively, and the maximum coefficient of variation measurement standards are 5.60567196% and 4.699465238% respectively, which do not meet the creep load judgment criteria that the coefficients of variation of rotational speed and temperature are both less than 0.5%, and the maximum coefficient of variation measurement standards are both less than 2.5%. The first load spectrum diagram is as Figure 3 shown.

[0051] Continue to divide the first part that does not meet the judgment criteria into 10 equal parts to obtain load spectra with the same duration t1 = 10 s. The diagrams of the first and second load spectra are as Figure 4 shown.

[0052] Data processing after the first load spectrum in Table 2 is equally divided into 10 parts again

[0053]

[0054] Perform the creep load judgment on these 10 equal parts again as described above. Except that the time periods of 11 - 20 seconds, 21 - 30 seconds, and 31 - 40 seconds do not meet the creep load judgment criteria, the remaining equal parts are also regarded as creep loads, denoted as unit 1, and stored in the second column of arrays N2 and T4. The average values of the rotational speed and temperature of this part are also regarded as the creep load data of this equal part and are stored in the third column of arrays N2 and T4 in chronological order respectively. The duration is denoted as t1 = 10s and is stored in the fourth column of arrays N2 and T4 respectively. After judging all 59 equal parts of the load spectrum based on the proposed creep load judgment criteria in turn, the creep loads of the aero-engine load spectrum are extracted. The rotational speed and gas temperature of the original load spectrum data are stored in the first column of N2 and T4, the creep load data are stored in the third column of N2 and T4, and the durations of different creep loads are stored in the fourth column of N2 and T4. Thus, the original load spectrum and the creep load spectrum of this mission profile can be drawn, with time as the horizontal axis and rotational speed and time as the vertical axis, as Figure 5 shown

[0055] (3) Based on the average values of the rotational speed and gas temperature and the durations of each equal part that meet the creep load criteria obtained in step (3), construct a duration-rotational speed-temperature fitting curve graph to obtain the creep load distribution law, as Figure 6 shown

[0056] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum, characterized in that: Including the following steps: Step S1: Divide the flight mission profile equally to obtain a load spectrum with each part having the same duration t0. Step S2: Based on the creep load judgment criterion, extract the creep load to obtain a creep load spectrum. Among them, the creep load judgment criterion is as follows: a. Calculate the standard deviation and average value of the rotational speed and temperature in each equal part, divide the standard deviation by the average value to obtain the coefficient of variation of the rotational speed and temperature in each equal part. b. Calculate the difference between the maximum and minimum values of the rotational speed and temperature in each equal part, divide the difference by the average value to obtain the maximum coefficient of variation measurement criterion in each equal part. c. Judge whether the coefficient of variation of the rotational speed and temperature in each equal part is less than 0.5%; judge whether the maximum coefficient of variation measurement criterion in each equal part is less than 2.5%; if both less-than conditions are satisfied, extract it as the creep load. Step S3: Based on the creep load spectrum obtained in Step S2 that meets the creep load judgment criterion, construct a duration-rotational speed-temperature fitting curve graph to obtain the creep load distribution law.

2. The method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum according to claim 1, characterized in that: In the said Step S1, each load spectrum includes a rotational speed spectrum and an engine temperature spectrum.

3. The method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum according to claim 1, characterized in that: In the said Step S1, t0 = 100s.

4. The method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum according to claim 1, characterized in that: The said Step S2 is specifically as follows: If the equal-part load spectrum meets the creep load judgment criterion, regard this equal-part load spectrum as the creep load, and record it as unit 1, obtain the average values of the rotational speed and gas temperature in this equal-part load spectrum, store them in arrays N2 and T4 respectively, and record the duration as t0; if the equal-part load spectrum does not meet the creep load judgment criterion, continue to divide the equal part that does not meet the judgment criterion equally to obtain a load spectrum with each part having the same duration t1, judge this equal-part load spectrum again, if it meets the creep load judgment criterion, also regard this equal-part load spectrum as the creep load, and record it as unit 1, obtain the average values of the rotational speed and gas temperature in this equal-part load spectrum, store them in arrays N2 and T4 respectively, and record the duration as t1.

5. The method for extracting creep loads and determining their distribution laws in an aero-engine load spectrum according to claim 4, characterized in that: In the said Step S2, t1 = 10s.

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