A method and device for blade tip timing based on laser doppler effect

Abstract

A kind of tip timing method and device based on laser Doppler effect, for realizing fiber tip timing;The method comprises the following steps: step S1, laser is sent out, through fiber beam splitter and laser is divided into first light beam and second light beam;Step S2, first light beam is irradiated to blade tip by temperature-resistant fiber probe, and the laser reflected by blade tip is received, signal light participating in interference is formed, and is sent to fiber combiner;Step S3, second light beam is sent to fiber combiner, and reference light participating in interference is formed;Step S4, signal light and reference light interfere to form interference light field, and the electrical signal of interference light field is acquired;Step S5, blade tip time ti is obtained according to electrical signal;And a kind of tip timing device based on laser Doppler effect, the blade tip time of the blade tip of the engine blade in the engine casing of engine is measured.The present application has the advantages of accurate measurement and high engineering applicability.

Description

Technical Field

[0001] This invention relates to the field of optical precision measurement technology, and in particular to a method and apparatus for leaf tip timing based on the laser Doppler effect. Background Technology

[0002] Blades are one of the core components of aero-engines. During operation, they are subjected to complex environments such as extreme high temperature, high pressure, and heavy load. Under the combined action of centrifugal force and aerodynamic force, they will vibrate. Vibration exceeding limits and vibration-induced fatigue failure will lead to serious engine malfunctions. Therefore, accurate measurement of blade vibration parameters (amplitude and frequency) is one of the important means of engine condition monitoring, fault diagnosis, and accident prevention. Non-contact blade tip timing technology is the most effective method to achieve vibration parameter measurement.

[0003] To measure the vibration parameters of engine fan, compressor, and turbine blades, the primary method currently employed is the blade vibration parameter measurement method based on the blade tip timing principle. Traditional blade tip timing methods include fiber optic blade tip timing, capacitive blade tip timing, and microwave blade tip timing. Among these, the fiber optic blade tip timing method has been widely used in engineering experiments and is currently the mainstream method for measuring blade vibration parameters. The fiber optic blade tip timing method involves emitting a continuous laser beam towards the blade. When the blade arrives, the reflected light intensity reaches a predetermined trigger threshold, thus identifying the blade tip arrival time. The reflected light intensity is closely related to the distance between the fiber optic sensor and the blade tip, the blade tip reflectivity, and the luminescence from combustion products. However, in actual engineering environments, due to factors such as changes in blade tip clearance, variations in blade tip optical reflection characteristics under high temperatures, and high-temperature radiation luminescence, the reflected light intensity exhibits drastic random fluctuations. Its timing accuracy is generally only on the order of microseconds, making it unable to effectively distinguish relatively small blade vibration amplitudes and higher-order vibration modes. Summary of the Invention

[0004] The purpose of this invention is to provide a blade tip timing method and device based on the laser Doppler effect, which has the advantages of accurate measurement and high engineering applicability.

[0005] To achieve the above objectives, this invention provides a leaf tip timing method based on the laser Doppler effect for fiber optic leaf tip timing. The method includes: Step S1, emitting a laser beam, which is then split into a first beam and a second beam by an optical fiber beam splitter; Step S2, irradiating the leaf tip with the first beam through a heat-resistant optical fiber probe and receiving the laser reflected from the leaf tip to form a signal beam participating in interference, which is then sent to an optical fiber combiner; Step S3, sending the second beam to the optical fiber combiner to form a reference beam participating in interference; Step S4, interfering with the signal beam and the reference beam to form an interference light field, and acquiring the electrical signal of the interference light field. Step S5, based on the electrical signal Obtain the leaf tip time ti.

[0006] Preferably, in step S1, the emitted laser light is split into two beams by an optical fiber beam splitter, and the first beam has the following optical field form: With the second beam light field form They are respectively:

[0007]

[0008]

[0009] k=2π / λ

[0010] f0=c / λ

[0011] in, λ is the amplitude of the laser; k is the laser wave vector; λ is the laser wavelength; r0 is the initial propagation path of the laser; f0 is the laser frequency; c is the speed of light; t is time; η is a constant determined by the fractional ratio of the fiber beam splitter.

[0012] Preferably, step S2 includes: step S21, irradiating the leaf tip with a first light beam through a heat-resistant fiber optic probe, and the expression for the light field of the first light beam emitted by the heat-resistant fiber optic probe. for,

[0013]

[0014] Where α is the collection efficiency of the heat-resistant fiber optic probe; ρ is the light reflectivity at the leaf tip; η1 is the amplitude attenuation factor of the first beam reaching the link of the heat-resistant fiber optic probe; r 10 f1 represents the laser propagation path from the fiber optic beam splitter to the heat-resistant fiber optic probe; f2 represents the laser with Doppler frequency shift reflected back from the leaf tip received by the heat-resistant fiber optic probe.

[0015] Step S22: The heat-resistant fiber optic probe receives the laser light reflected from the leaf tip, which is then transmitted to the fiber optic combiner after passing through a fiber optic amplifier to form the signal light participating in the interference. The expression for the light field of the signal light participating in the interference is... for:

[0016]

[0017] Where η2 is the amplitude attenuation factor at the connection port from the temperature-resistant fiber optic probe to the fiber optic amplifier; K is the amplitude amplification factor of the fiber optic amplifier; r 20 This represents the laser propagation path from the heat-resistant fiber optic probe to the fiber optic combiner.

[0018] Preferably, in step S22, f1 is:

[0019]

[0020] Where ω is the rotational speed of the engine to which the blade belongs; R is the radius of the blade; and θ is the angle between the central axis of the heat-resistant fiber optic probe and the normal to the blade rotor.

[0021] Preferably, in step S3, the expression for the reference light field participating in the interference is... for:

[0022]

[0023] Where, r 30 This is the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner. This is the amplitude attenuation factor of the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner.

[0024] Preferably, step S4 includes: step S41, interfering the signal light with the reference light to obtain an interference light field, and the light intensity of the interference light field... for:

[0025]

[0026]

[0027]

[0028] = r 30 - r 10 - r 20

[0029] Where A is the amplitude of the signal light; and B is the amplitude of the reference light. The phase difference between the signal light and the reference light that participate in the interference, after they have traveled different paths;

[0030] Step S42, based on the intensity of the light after interference Electrical signals are obtained through photodetectors. ;

[0031]

[0032] Where k is the sensitivity of the photodetector.

[0033] Preferably, step S5 includes: step S51, detecting the electrical signal at time T. Does it satisfy the electrical signal? The high-frequency components are Step S52: If the condition is met, output the current time as the tip time ti; if the condition is not met, let T = T + T and return to step S51.

[0034] A blade tip timing device based on the laser Doppler effect is disclosed. The device is used to implement a aforementioned blade tip timing method based on the laser Doppler effect, measuring the blade tip time of engine blades within the engine casing. The device includes: a fiber laser emitting laser light with wavelength λ; a fiber beam splitter connected to the fiber laser, proportionally splitting the input laser light into a first beam and a second beam for output; and a fiber circulator including a first port, a second port, and a third port. The beam travels unidirectionally from the first port to the second port, and unidirectionally from the second port to the third port. The system consists of: a first port connected to an optical fiber beam splitter; a transmission optical fiber connected to the second port to transmit the first beam to the location to be tested; a heat-resistant optical fiber probe fixedly mounted on the outside of the engine casing; an optical fiber amplifier connected to the third port to amplify the power of the reflected light from the engine blade tip; an optical fiber combiner connected to both the optical fiber amplifier and the optical fiber beam splitter to receive the second beam as a reference beam and interfere with the reference beam and the signal beam to form an interference light field; and an acquisition module connected to the optical fiber combiner to analyze the interference light field and obtain the blade tip time.

[0035] Preferably, the acquisition module includes: a photoelectric converter connected to an optical fiber combiner to convert the light intensity of the interference light field into an electrical signal; an acquisition card connected to the photoelectric converter to acquire the electrical signal in real time and perform time-frequency analysis to extract the occurrence time information of characteristic frequencies; and a computer connected to the acquisition card to analyze and store the occurrence time information of characteristic frequencies output by the acquisition card, i.e., the leaf tip arrival time sequence.

[0036] In summary, compared with the prior art, the leaf tip timing method and device based on the laser Doppler effect provided by the present invention have the following beneficial effects:

[0037] First, the present invention proposes a blade tip timing method and device based on the laser Doppler effect, in which a probe laser is irradiated onto a high-speed rotating blade through an optical fiber sensor. Due to the optical Doppler effect, the reflected laser will have a Doppler frequency shift. The reflected light from the blade is heterodyne-interfered with the reference laser, and the precise measurement of the blade tip arrival time is achieved by measuring the frequency change moment of the interference signal.

[0038] Secondly, the blade tip timing method and device proposed in this invention, based on the laser Doppler effect, addresses the accuracy reduction problem of existing fiber optic blade tip timing methods that rely on intensity measurement. This invention's method avoids the influence of intensity fluctuations in the engineering environment by measuring the blade arrival time in the frequency domain. Its blade tip arrival time measurement accuracy can reach the nanosecond level, making it highly applicable to engineering applications. Attached Figure Description

[0039] Figure 1 This invention proposes a blade tip timing device based on the laser Doppler effect.

[0040] Figure 2(a) shows the test results of the laser interferometry method.

[0041] Figure 2(b) shows the test results of light intensity reflection.

[0042] Figure 3 This is a schematic flowchart of a blade tip timing method based on the laser Doppler effect proposed in this invention.

[0043] Figure label:

[0044] 1-Fiber laser, 2-Fiber beam splitter, 3-Fiber circulator, 4-Transmission fiber, 5-Temperature resistant fiber probe, 6-Fiber amplifier, 7-Fiber combiner, 8-Photoelectric converter, 9-Acquisition card, 10-Computer, 11-Engine casing, 12-Engine blade, 31-First port, 32-Second port, 33-Third port. Detailed Implementation

[0045] The following will be combined with the appendix in the embodiments of the present invention. Figure 1 ~Appendix Figure 3 The technical solutions, structural features, objectives and effects achieved in the embodiments of the present invention will be described in detail.

[0046] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0047] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0048] like Figure 3 As shown, this invention proposes a leaf tip timing method and apparatus based on the laser Doppler effect for realizing fiber optic leaf tip timing; the method includes:

[0049] Step S1: Emit laser light, which is then split into a first beam and a second beam by an optical fiber beam splitter;

[0050] Step S2: The first beam is irradiated onto the leaf tip through a heat-resistant fiber optic probe, and the laser reflected from the leaf tip is received to form a signal light that participates in the interference, which is then sent to the fiber optic combiner.

[0051] Step S3: Send the second beam to the fiber optic combiner to form a reference beam that participates in the interference;

[0052] Step S4: The signal light interferes with the reference light to form an interference light field, and the electrical signal of the interference light field is acquired. ;

[0053] Step S5, based on the electrical signal Obtain the leaf tip time ti.

[0054] Specifically, in step S1, the laser emitted by the fiber laser is first split into two beams by a fiber beam splitter, and the first beam has a different optical field shape. With the second beam light field form They are respectively:

[0055]

[0056]

[0057] k=2π / λ

[0058] f0=c / λ

[0059] in, λ is the amplitude of the laser; k is the laser wave vector; λ is the laser wavelength; r0 is the initial propagation path of the laser; f0 is the laser frequency; c is the speed of light; t is time; η is a constant determined by the fractional ratio of the fiber beam splitter.

[0060] Specifically, step S2 includes:

[0061] Step S21: The first light beam is irradiated onto the blade tip through a heat-resistant fiber optic probe. The light field expression of the first light beam emitted by the heat-resistant fiber optic probe is... for,

[0062]

[0063] Where α is the collection efficiency of the heat-resistant fiber optic probe; ρ is the light reflectivity at the leaf tip; η1 is the amplitude attenuation factor of the first beam reaching the link of the heat-resistant fiber optic probe; r 10 f1 represents the laser propagation path from the fiber optic beam splitter to the heat-resistant fiber optic probe; f2 represents the laser with Doppler frequency shift reflected back from the leaf tip received by the heat-resistant fiber optic probe.

[0064] In a preferred embodiment, f1 is

[0065]

[0066] Where ω is the rotational speed of the engine to which the blade belongs; R is the radius of the blade; and θ is the angle between the central axis of the heat-resistant fiber optic probe and the normal to the blade rotor.

[0067] Step S22: The heat-resistant fiber optic probe receives the laser light reflected from the leaf tip, which is then transmitted to the fiber optic combiner after passing through a fiber optic amplifier to form the signal light participating in the interference. The expression for the light field of the signal light participating in the interference is... for:

[0068]

[0069] Where η2 is the amplitude attenuation factor at the connection port from the temperature-resistant fiber optic probe to the fiber optic amplifier (specifically, the connection port between the fiber optic circulator and the fiber optic amplifier); K is the amplitude amplification factor of the fiber optic amplifier; r 20 This describes the laser propagation path from the heat-resistant fiber optic probe to the fiber optic combiner.

[0070] In addition, when the engine is running, after the blade tip leaves the field of view of the heat-resistant fiber optic probe, the heat-resistant fiber optic probe will not receive the laser reflected back from the blade tip, ρ=0, which represents this situation.

[0071] Specifically, in step S3, the expression for the reference light field participating in the interference... for:

[0072]

[0073] Where, r 30 This is the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner. The amplitude attenuation factor is the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner.

[0074] Specifically, step S4 includes:

[0075] Step S41: The signal light interferes with the reference light to obtain the interference light field, and the intensity of the interference light field is... for:

[0076]

[0077]

[0078]

[0079] = r 30 - r 10 - r 20

[0080] Where A is the amplitude of the signal light and B is the amplitude of the reference light. The phase difference between the signal light and the reference light that participate in the interference, resulting from the different paths they have taken.

[0081] Step S42, based on the intensity of the light after interference Electrical signals are obtained through photodetectors. ;

[0082]

[0083] Where k is the sensitivity of the photodetector.

[0084] Specifically, step S5 includes:

[0085] Step S51: Detect the electrical signal at time T. Does it satisfy the electrical signal? The high-frequency components are ;

[0086] Step S52: If the condition is met, output the current time as the tip time ti; if the condition is not met, let T = T + T and return to step S51.

[0087] The principle here is as follows: The first two items , is the DC component generated by the interference of the signal light and the reference light; the third term The interference component is the AC component generated by the interference. When the blade tip passes through the field of view of the heat-resistant fiber optic probe, the probe will receive the reflected light from the blade tip, thus generating the interference signal described above. When the blade tip leaves the field of view of the heat-resistant fiber optic probe, the probe will not receive any reflected light. Therefore, when only the second term exists... That is, only the DC component of the reference light.

[0088] Therefore, in a specific embodiment, the electrical signal i output by the photodetector can be acquired in real time using a data acquisition card and subjected to time-frequency analysis. When the blade tip does not appear within the field of view of the heat-resistant fiber optic probe, it can be known that it has only one DC component and no high-frequency components appear in the spectrum.

[0089] Once the leaf tip enters the field of view of the heat-resistant fiber optic probe, it is known that it contains an AC component, and a high-frequency component will appear in the spectrum. Therefore, the frequency of this high-frequency component is:

[0090]

[0091] When the acquisition card detects the high-frequency component fi, it records the moment when the high-frequency signal appears as the blade tip time ti. This moment represents the arrival time of the blade tip at the field of view of the heat-resistant fiber optic probe, thus realizing blade tip timing. This arrival time information can be used for analysis of the vibration amplitude and vibration frequency of the blade.

[0092] In addition, such as Figure 1 As shown, the present invention also proposes a heterodyne interferometric blade tip timing device based on the laser Doppler effect; for measuring the blade tip timing of the engine blade 12 within the engine casing 11; the device includes:

[0093] Fiber laser 1 emits laser light with a wavelength of λ;

[0094] The fiber beam splitter 2 is connected to the fiber laser 1 and splits the input laser into two output beams in equal proportion, namely the first beam and the second beam mentioned above.

[0095] The fiber optic circulator 3 includes a first port 31, a second port 32, and a third port 33; wherein the light beam travels unidirectionally from the first port 31 to the second port 32, and from the second port 32 to the third port 33; the first port 31 is connected to the fiber optic beam splitter 2.

[0096] The transmission fiber 4 is connected to the second port 32 and is used to transmit the first beam to the location that needs to be tested.

[0097] The heat-resistant fiber optic probe 5 is fixedly installed outside the engine casing 11; the first beam shines on the tip of the engine blade 12 through the heat-resistant fiber optic probe 5, and at the same time receives the reflected light from the tip of the blade; subsequently, the reflected light will be amplified by the fiber optic amplifier 6 and used as the interference signal light. The heat-resistant fiber optic probe 5 is installed on the engine casing 11 at a certain angle (the angle with the normal is θ).

[0098] Fiber optic amplifier 6, connected to the third port 33, amplifies the power of the reflected light (weak laser) reflected back from the engine blade tip;

[0099] The fiber optic combiner 7 is connected to the fiber optic amplifier 6 and the fiber optic splitter 2 respectively. It receives the second beam as a reference beam and interferes with the reference beam and the signal beam to form an interference light field. In this embodiment, its beam combining ratio is 50:50. After combining the reference beam and the signal beam (i.e. forming an interference light field), it is output.

[0100] The acquisition module, connected to the fiber optic combiner 7, analyzes the interference light field to obtain the leaf tip time.

[0101] Specifically, the data acquisition module includes:

[0102] The photoelectric converter 8 is connected to the fiber optic combiner 7 to convert the light intensity of the interference light field into an electrical signal;

[0103] The acquisition card 9 is connected to the photoelectric converter 8 to acquire electrical signals in real time, perform time-frequency analysis, and extract the time information of characteristic frequency occurrence.

[0104] Computer 10 is connected to acquisition card 9 to analyze and store the characteristic frequency occurrence time information output by acquisition card 9, that is, the leaf tip arrival time sequence.

[0105] For heterodyne interferometric blade tip timing systems based on the laser Doppler effect, Figure 1 The optimal implementation scheme is illustrated using the structure shown in the figure. The laser source used in the figure is a 1550nm continuous laser, which is connected to the input port of a 1×2 fiber beam splitter 2 with a splitting ratio of 90:10. The output port of the 1×2 fiber beam splitter 2 is connected to the first port 31 of the fiber optic circulator 3, and the second port 32 of the fiber optic circulator 3 is connected to the transmission fiber 4. The transmission fiber 4 is connected to the heat-resistant fiber optic probe 5, which is mounted on the engine casing 11 at an angle θ=3° with the normal.

[0106] The engine blade 12 operates at a maximum speed of 8000 rpm. The third port 33 of the fiber optic circulator 3 is connected to the input port of the fiber optic amplifier 6, amplifying the reflected signal light to 20mW, and then connected to the input port of the 2×1 fiber optic combiner 7. The other output port of the 1×2 fiber optic splitter 2 is connected to the input port of the 2×1 fiber optic combiner 7. The output port of the 2×1 fiber optic combiner 7 is connected to the optical input port of the 1GHz bandwidth photoelectric converter 8. The electrical output port of the photoelectric converter 8 is connected to the acquisition card 9. After real-time acquisition, the acquisition card 9 performs short-time Fourier transform processing, obtains the blade tip arrival time by judging the high-frequency signal occurrence time, and uploads it to the computer to calculate the blade vibration amplitude.

[0107] As shown in Figures 2(a) and 2(b), this is the final result. After the blade time is measured, the blade vibration amplitude is calculated using the same algorithm and then compared. It can be seen that this method can clearly identify vibrations of 6th to 13th harmonics, while commercial technology can only measure vibrations of 6th to 10th harmonics. This improvement in discrimination ability is brought about by the improvement in blade timing accuracy.

[0108] The heterodyne interferometric blade tip timing method proposed in this invention significantly improves the timing accuracy of blade tip timing compared to the traditional light intensity reflection method, resulting in a markedly enhanced amplitude resolution. This solves the problem that the timing accuracy of traditional fiber optic blade tip timing technology is greatly affected by factors such as the intensity of blade tip reflection and the change in blade tip-casing gap, providing a brand-new technical method for the effective measurement of the vibration amplitude and higher-order vibration modes of micro blades.

[0109] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A blade tip timing method based on the laser Doppler effect, used to achieve fiber optic blade tip timing; characterized in that, The leaf tip timing method includes: Step S1: Emit laser light, which is then split into a first beam and a second beam by an optical fiber beam splitter; Step S2: The first beam is irradiated onto the blade tip through a heat-resistant fiber optic probe, and the laser reflected from the blade tip is received to form a signal light that participates in the interference, which is then sent to the fiber optic combiner. Step S3: Send the second beam to the fiber optic combiner to form a reference beam that participates in the interference; Step S4: The signal light interferes with the reference light to form an interference light field, and the electrical signal of the interference light field is acquired. ; Step S5, based on the electrical signal Obtain the leaf tip time ti; In step S1, the emitted laser light is split into two beams by an optical fiber beam splitter, and the first beam has the following optical field form. With the second beam light field form They are respectively: k=2π / λ f0=c / λ in, λ is the amplitude of the laser beam; k is the laser wave vector; λ is the laser wavelength; r0 is the initial propagation path of the laser; f0 is the laser frequency; c is the speed of light; t is time; η is a constant determined by the fractional ratio of the fiber beam splitter. Step S2 includes: Step S21: The first beam is irradiated onto the blade tip through a heat-resistant fiber optic probe. The expression for the light field of the first beam emitted by the heat-resistant fiber optic probe is... for, Where α is the collection efficiency of the heat-resistant fiber optic probe; ρ is the light reflectivity at the leaf tip; η1 is the amplitude attenuation factor of the first beam reaching the link of the heat-resistant fiber optic probe; r 10 f1 represents the laser propagation path from the fiber optic beam splitter to the heat-resistant fiber optic probe; f2 represents the laser with Doppler frequency shift reflected back from the leaf tip received by the heat-resistant fiber optic probe. Step S22: The heat-resistant fiber optic probe receives the laser light reflected from the leaf tip, which is then transmitted to the fiber optic combiner after passing through a fiber optic amplifier to form the signal light participating in the interference. The expression for the light field of the signal light participating in the interference is... for: Where η2 is the amplitude attenuation factor at the connection port from the temperature-resistant fiber optic probe to the fiber optic amplifier; K is the amplitude amplification factor of the fiber optic amplifier; r 20 This describes the laser propagation path from the heat-resistant fiber optic probe to the fiber optic combiner. In step S22, f1 is: Where ω is the rotational speed of the engine to which the blade belongs; R is the radius of the blade; and θ is the angle between the central axis of the heat-resistant fiber optic probe and the normal to the blade rotor.

2. The leaf tip timing method based on the laser Doppler effect according to claim 1, characterized in that, In step S3, the expression for the reference light field participating in the interference is... for: Where, r 30 This is the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner. This is the amplitude attenuation factor of the laser propagation path of the second beam from the fiber beam splitter to the fiber beam combiner.

3. The leaf tip timing method based on the laser Doppler effect according to claim 2, characterized in that, Step S4 includes: Step S41: The signal light interferes with the reference light to obtain the interference light field, and the intensity of the interference light field is... for: = r 30 - r 10 - r 20 Where A is the amplitude of the signal light; and B is the amplitude of the reference light. The phase difference between the signal light and the reference light that participate in the interference, after they have traveled different paths; Step S42, based on the intensity of the light after interference Electrical signals are obtained through photodetectors. ; in, This refers to the sensitivity of the photodetector.

4. The leaf tip timing method based on the laser Doppler effect according to claim 3, characterized in that, Step S5 includes: Step S51: Detect the electrical signal at time T. Does it satisfy the electrical signal? The high-frequency components are ; Step S52: If the condition is met, output the current time as the tip time ti; if the condition is not met, let T = T + T and return to step S51.

5. A blade tip timing device based on the laser Doppler effect, characterized in that, The blade tip timing device is used to implement the blade tip timing method based on the laser Doppler effect as described in any one of claims 1 to 4; The device measures the tip-tip time of the engine blades (12) within the engine casing (11); the device includes: Fiber laser (1) emits laser light with a wavelength of λ; The fiber beam splitter (2) is connected to the fiber laser (1) and splits the input laser into a first beam and a second beam for output in equal proportion; The fiber optic circulator (3) includes a first port (31), a second port (32), and a third port (33); wherein the light beam travels unidirectionally from the first port (31) to the second port (32), and the light beam travels unidirectionally from the second port (32) to the third port (33); the first port (31) is connected to the fiber optic beam splitter (2); The transmission fiber (4) is connected to the second port (32) to transmit the first beam to the location to be tested; A heat-resistant fiber optic probe (5) is fixedly installed on the outside of the engine casing (11). The heat-resistant fiber optic probe (5) is installed on the engine casing (11). The fiber amplifier (6), connected to the third port (33), amplifies the power of the reflected light reflected from the engine blade tip; The fiber optic combiner (7) is connected to the fiber optic amplifier (6) and the fiber optic splitter (2) respectively. It receives the second beam as the reference beam and interferes with the signal beam to form an interference light field. The acquisition module is connected to the fiber optic combiner (7) to analyze the interference light field and obtain the leaf tip time.

6. The blade tip timing device based on the laser Doppler effect according to claim 5, characterized in that, The acquisition module includes: The photoelectric converter (8) is connected to the fiber optic combiner (7) to convert the light intensity of the interference light field into an electrical signal; The acquisition card (9) is connected to the photoelectric converter (8) to acquire electrical signals in real time and perform time-frequency analysis to extract the time information of the occurrence of characteristic frequencies; The computer (10) is connected to the acquisition card (9) to analyze and store the characteristic frequency occurrence time information output by the acquisition card (9).

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