A device and method for measuring steady-state deformation of rotating blades inside a casing

Abstract

The present invention discloses a device for measuring the steady-state deformation of rotating blades inside a casing, comprising a data acquisition and processing system, an optical fiber array, and an optical fiber probe group. The optical fiber probe group includes at least two optical fiber probes, which are mounted on the casing along the chord direction. The axial position of each optical fiber probe relative to the rotating shaft is different. The optical fiber array has optical fibers that match the number of optical fiber probes. The optical fiber probes are connected to the data acquisition and processing system via the optical fibers of the optical fiber array. The data acquisition and processing system collects and processes the data collected by the optical fiber probe group. The data acquisition and processing system is configured to calculate the steady-state deformation of the blades. The present invention also discloses a method for measuring the steady-state deformation of rotating blades inside a casing. The present invention can simultaneously obtain three parameters: circumferential translation, axial translation, and anti-torsion angle, with high calculation accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of rotating blade measurement, and in particular to a device and method for measuring the steady-state deformation of rotating blades inside a casing. Background Art

[0002] Blades are one of the most important working components of a turbomachinery. During turbomachinery operation, blade static deformation is a key operating parameter. This parameter can be categorized as axial movement, translation, and torsion. Without reliable measurement methods, researchers often struggle to accurately measure blade static deformation. The following devices and methods exist for measuring the steady-state deformation of rotating blades located within the casing.

[0003] Coordinate measuring (CMM) is an advanced method for measuring blade shape during quality inspection. It relies on a sensitive contact probe and a high-precision displacement mechanism to measure blade shape with high accuracy. However, CMMs are comparable in size to machine tools and cannot be used to measure rotating blades inside casings.

[0004] The 3D scanner method uses structured light scanning to quickly measure the blade shape. It is more efficient than the three-dimensional coordinate measuring machine method, but its accuracy is slightly lower. However, when measuring the blade inside the casing, its light path is blocked, making measurement impossible.

[0005] Optical derotation instruments and high-speed cameras directly capture the blade's shape, a simple principle. However, when the blade is inside the casing, the illumination and imaging light paths are obstructed, making measurement impossible. Furthermore, measurement accuracy is poor at high rotational speeds.

[0006] There are several non-contact measurement techniques based on blade tip timing.

[0007] The chord fitting method treats the blade as a one-dimensional model, assuming that the steady-state deformation consists solely of translation perpendicular to the chord direction. This translation distance is calculated using a blade tip sensor and a preset blade mounting angle. However, real engine blades have three-dimensional shapes, and the deformations they undergo also exhibit three-dimensional characteristics. This method cannot accurately measure axial translation, circumferential translation, and torsion simultaneously, making it impractical and unable to provide the parameters designers require. In particular, the trend term method can mistakenly attribute changes caused by torsion and axial translation to translation perpendicular to the chord direction, resulting in significant errors.

[0008] The forward fitting method considers the blade profile on the pressure surface and five types of blade tip motion. By specifying a specific motion form, it estimates the distance the blade would move under that motion form. This method fails to consider the coupling between the different blade motion forms, resulting in low accuracy in the calculated results.

[0009] In addition, the chord fitting method and the forward fitting method only use the blade arrival time for calculation, and the deformation resolution of the blade along the chord direction is very low in actual use.

[0010] Therefore, technicians in this field are committed to providing a device and method for measuring the steady-state deformation of rotating blades inside the casing, so as to solve the problem that the existing measuring device's steady-state deformation measurement method of rotating blades is imperfect and can only measure a single static deformation parameter, namely blade translation, to achieve accurate measurement of the axial movement and torsion of static deformation and improve the ability of static deformation measurement. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is how to provide a measuring device and a measuring method that can accurately measure the circumferential, axial and torsional static deformation of a blade.

[0012] To achieve the above-mentioned purpose, the present invention provides a device for measuring the steady-state deformation of rotating blades inside a casing, which is used for measuring the steady-state deformation of blades. The blades are mounted on a rotating shaft, and the blades and the rotating shaft are located inside the casing. The device includes a data acquisition and processing system, an optical fiber array, and an optical fiber probe group. The optical fiber probe group includes at least two optical fiber probes, which are mounted on the casing along the chord direction. The axial position of each optical fiber probe relative to the rotating shaft is different. The optical fiber array has optical fibers matching the number of the optical fiber probes. The optical fiber probes are connected to the data acquisition and processing system through the optical fibers of the optical fiber array. The data acquisition and processing system collects and processes the data collected by the optical fiber probe group. The data acquisition and processing system is configured to calculate the steady-state deformation of the blades.

[0013] Furthermore, the optical fiber probe collects the arrival and departure times of the blades.

[0014] Furthermore, the steady-state deformation of the blade includes the displacement d of the leading edge point of the blade tip and the anti-twist angle ψ of the leading edge point of the blade tip projection curve.

[0015] Furthermore, the displacement d of the blade tip leading edge point includes a circumferential displacement Δζ and an axial displacement Δη.

[0016] Preferably, the optical fiber probe set is replaced by a capacitive sensor or an eddy current sensor.

[0017] The present invention also provides a method for measuring the steady-state deformation of a rotating blade inside a casing, comprising the following steps:

[0018] Step 1: Install the fiber optic probe assembly on the casing and record the installation angle of the fiber optic probe. and

[0019] Step 2: Start the turbine and collect the data of blade arrival and departure by the data acquisition and processing system to calculate the circumferential position offset ζ offset and axial position offset η offset ;

[0020] Step 3: Run the turbine under the same fiber optic probe configuration, and use the data acquisition and processing system to collect the blade arrival and departure data to calculate ψ, Δζ, and Δη.

[0021] Furthermore, step 2 specifically includes:

[0022] Start the impeller and make the blades work at low speed and low aerodynamic force;

[0023] The data acquisition and processing system collects the data of the blade's arrival and departure until the blade rotates n times. rev lock up;

[0024] Calculate the initial parameters of the pressure surface;

[0025] Establish the objective function, solve the optimization problem, and obtain ζ offset and η offset .

[0026] Furthermore, the initial parameters of the pressure surface are:

[0027]

[0028]

[0029]

[0030] The objective function established is:

[0031]

[0032] The optimization solution is:

[0033] min e pre∩suc

[0034]

[0035] Furthermore, step 3 specifically includes:

[0036] Under the same fiber optic probe configuration scheme as step 2, start the impeller and run it under stable conditions;

[0037] The data acquisition and processing system collects the data of blade arrival and departure;

[0038] Calculate the initial coordinates of the parameter points;

[0039] Establish the objective function, solve the optimization problem, and obtain ψ, Δζ, and Δη.

[0040] Furthermore, the initial coordinates of the parameter points are:

[0041]

[0042] The objective function is:

[0043]

[0044] The optimization solution is:

[0045] min e pre∩suc

[0046] ψ min <ψ<ψ max ,

[0047] stΔζ min <Δζ<Δζ max ,

[0048] Δη min <Δη<Δη max ..

[0049] The present invention has at least the following beneficial technical effects:

[0050] 1. The present invention realizes the function of obtaining the steady-state deformation of the blades running inside the casing in a non-contact manner, and can simultaneously calculate the three parameters of circumferential translation, axial translation and anti-twist angle. It has low technical difficulty and is easy to maintain.

[0051] 2. The present invention can integrate the two features of blade arrival time and blade departure time, thereby improving the calculation accuracy, especially the calculation accuracy of the blade deformation size along the chord direction; the calculation method of the present invention can integrate data from more than two sensors, further improving the calculation accuracy.

[0052] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Schematic diagram of a device for measuring steady-state deformation of rotating blades inside a casing according to an embodiment of the present invention;

[0054] Figure 2 Schematic diagram of the measurement principle of an embodiment of the present invention;

[0055] Figure 3 Schematic diagram of the calculation principle of an embodiment of the present invention;

[0056] Figure 4 is a schematic diagram of calibration results according to an embodiment of the present invention;

[0057] Figure 5 Schematic diagram of measurement results according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following describes preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0059] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0060] The present invention provides a device and a method for measuring the steady-state deformation of rotating blades inside a casing, which can achieve accurate measurement of the circumferential movement, axial movement and torsion of the static deformation of the blades and improve the ability of static deformation measurement.

[0061] like Figure 1 As shown, the device for measuring the steady-state deformation of rotating blades within a casing 2 is used to measure the steady-state deformation of blades 3. Blades 3 are arranged along the circumference of a rotating shaft 4 and rotate with the rotating shaft 4. Blades 3 and the rotating shaft 4 are disposed within a casing 2. The measurement device of this embodiment includes a blade tip timing system 1, specifically composed of a data acquisition and processing system 101, an optical fiber array 102, and an optical fiber probe assembly 103. The optical fiber probes of the optical fiber probe assembly 103 are mounted on the casing 2 along the chord direction, and each optical fiber probe has a different axial position relative to the rotating shaft 4. Each optical fiber probe in the optical fiber probe assembly 103 is connected to the data acquisition and processing system 101 via an optical fiber of the optical fiber array 102. Each optical fiber probe in the optical fiber probe assembly 103 is capable of detecting the arrival and departure of blades 3 and transmitting the detection signal to the data acquisition and processing system 101 via the optical fiber array 102. The data acquisition and processing system 101 records the arrival and departure times of blades 3 and calculates the steady-state deformation of blades 3 through data processing.

[0062] like Figure 2 and Figure 3 As shown in the figure, the deformation of blade 3 can be represented by the displacement d of the leading edge point of the blade tip and the anti-twist angle ψ of the blade tip projection curve around the leading edge point. The displacement d of the leading edge point can be decomposed into two components: circumferential displacement Δζ and axial displacement Δη. That is, the deformation of blade 3 can be described by three parameters: anti-twist angle ψ, circumferential displacement Δζ, and axial displacement Δη.

[0063] In the above embodiments, the optical fiber probe set 103 may also be replaced by a capacitive sensor or an eddy current sensor.

[0064] The measuring principle of the measuring device of this embodiment is as follows.

[0065] To distinguish the relative motion between the fiber optic probe and the blade, two reference frames are set. The first reference frame is the rotor reference frame fixed to the shaft 4 and rotating with the shaft 4. The second reference frame is the casing reference frame fixed to the casing 2. Assuming that the shaft 4 rotates by an angle φ(t) in time t, there is a transformation between the two reference frames:

[0066] ζ C =ζ R +r LE φ(t), (1)

[0067] η C =η R +η offset , (2)

[0068] Where superscript C represents the case reference frame, and superscript R represents the rotor reference frame. If the relative positions of the rotor and case in the axial direction are designed to be exactly the same, then η C Should be equal to η R Due to the limitation of assembly accuracy and the axial movement of the rotor, the rotor usually deviates from the design. To compensate for the error, the offset η is included in formula (2) offset .

[0069] The circumferential position of the i-th optical fiber probe in the optical fiber probe group 103 is recorded as The axial position is recorded as When a blade sweeps past it in the nth rotation, the data acquisition and processing system 101 measures the arrival time or departure time t i,n At this time, the angle φ(t i,n ), r LE is the leading edge radius of the blade, then:

[0070]

[0071]

[0072] It is expressed in the rotor coordinate system as:

[0073]

[0074]

[0075] Due to the limitation of machining accuracy, the actual installation position of each fiber optic probe in the fiber optic probe group 103 may be different from the designed position. Generally, the axial errors of all fiber optic probes are small and consistent, which can be simply expressed as a variable η offset The circumferential installation error of the fiber optic probe can also be calibrated by the BTT sensor during operation. After calibration, we have:

[0076]

[0077]

[0078] In the above formula, φ' i,n =φ i,n -2π(n-1), is the circumferential installation error,

[0079] Under the ideal condition of constant speed, φ' i，n The value in any circle should be constant, which can be expressed as Instead, formula (7) becomes:

[0080]

[0081] When there is a slight fluctuation in the speed, φ' is sampled every circle. i,n In the ideal Up and down fluctuations can be obtained through multi-circle average calibration:

[0082]

[0083] use Substitute the formula (9) We can get:

[0084]

[0085] Keep running at a stable speed, the measured and Calculate the initial state coordinates of the blade tip shape:

[0086]

[0087] The calculated initial point position should satisfy:

[0088]

[0089] In formula (13), η0 is a known function, Contains two variables to be calibrated η offset and In equation (12), three deformation parameters need to be solved: the anti-torsion angle ψ, the circumferential displacement Δζ, and the axial displacement Δη. In order for the problem to have a unique solution or a least-squares solution, the number of equations must be equal to or greater than the number of unknowns (3). Considering that each fiber optic probe can collect two features: the arrival time and the departure time of the blade, this embodiment requires the fiber optic probe group 103 to include at least two fiber optic probes, thereby collecting four features to make the equation well-posed. The more sensors there are, the higher the measurement accuracy.

[0090] The fiber optic probes are distributed in a limited small range in the circumferential direction, and their relative positions can be accurately measured without being significantly affected by the thermal deformation of the housing. Therefore, the actual position of the fiber optic probe can be obtained by adding the circumferential offset ζ to its design position. offset To express:

[0091]

[0092] To calibrate ζ offset and η offset This embodiment requires the rotor to operate at low speed and low aerodynamic load. During this period, the data acquisition and processing system 101 collects data. Under low speed and low aerodynamic load conditions, blade deformation can be ignored, and ψ = Δζ = Δη = 0 can be set. ζ is obtained by solving the following optimization problem. offset and η offset .

[0093] min e pre∩suc

[0094]

[0095] The expression of the objective function in the above formula is:

[0096]

[0097] Finally, the task of measuring the coupled static deformation parameters can be accomplished by solving the following optimization problem:

[0098] min e pre∩suc

[0099] ψ min <ψ<ψ max ,

[0100] stΔζ min <Δζ<Δζ max ,

[0101] Δη min <Δη<Δη max . (17)

[0102] It should be noted that Equations (15) and (17) have the same objective function. The difference is that in Equation (15), the deformation parameter ψ = Δζ = Δη = 0, and the calibration parameter ζ is solved. offset and η offset ; In formula (17), the calibration parameter ζ offset and η offset is known, and what is solved is the deformation parameters, namely the anti-torsion angle ψ, circumferential displacement Δζ, and axial displacement Δη under high speed and high load conditions.

[0103] Therefore, the method for measuring the steady-state deformation of the rotating blades inside the casing in this embodiment is as follows:

[0104] 1. Install the fiber optic probe assembly on the casing and record the installation angle and

[0105] 2. Start the impeller and make the blade 3 work at low speed and low aerodynamic force. The data acquisition and processing system 101 collects the data of the blade's arrival and departure until the blade rotates n times. rev Then, calculate the initial parameters of the pressure surface:

[0106]

[0107]

[0108]

[0109]

[0110] Establish the objective function as shown in formula (16), and solve the optimization problem according to formula (15) to calculate ζ offset and η offset Typical calibration results are as follows: Figure 4 shown.

[0111] 3. Using the same fiber optic probe configuration as in the above steps, start the turbine and run it under any stable operating conditions required for measurement. The data acquisition and processing system 101 collects the arrival and departure data of the blades and calculates the initial coordinates of the parameter points:

[0112]

[0113] Establish the objective function as shown in formula (16), and solve the optimization problem according to formula (17) to calculate ψ, Δζ, and Δη. Typical calibration results are as follows: Figure 5 shown.

[0114] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention can be made by one of ordinary skill in the art without inventive effort. Therefore, any person skilled in the art can arrive at a solution based on the concepts of the present invention through logical analysis, reasoning, or limited experimentation based on the prior art.

Claims

1. A method for measuring the steady-state deformation of a rotating blade inside a casing, wherein the blade is mounted on a rotating shaft, and the blade and the rotating shaft are located inside the casing. The device comprises a data acquisition and processing system, an optical fiber array, and an optical fiber probe group. The optical fiber probe group comprises at least two optical fiber probes, which are mounted on the casing along a chord direction. The axial position of each optical fiber probe relative to the rotating shaft is different. The optical fiber array has optical fibers that match the number of optical fiber probes. The optical fiber probe is connected to the data acquisition and processing system via the optical fibers of the optical fiber array. The data acquisition and processing system acquires and processes data acquired by the optical fiber probe group. The data acquisition and processing system is configured to calculate the steady-state deformation of the blade, characterized in that: The measuring method comprises the following steps: Step 1: Install the fiber optic probe assembly on the casing and record the installation angle of the fiber optic probe. and Step 2: Start the turbine and collect the data of blade arrival and departure by the data acquisition and processing system to calculate the circumferential position offset ζ offset and axial position offset η offset , specifically, Start the impeller and make the blades work at low speed and low aerodynamic force; The data acquisition and processing system collects the data of the blade's arrival and departure until the blade rotates n times. rev lock up; Calculate the initial parameters of the pressure surface; Establish the objective function, solve the optimization problem, and obtain ζ offset and η offset ; The initial parameters of the pressure surface are: The objective function established is: The optimization solution is: my email pre∩suc Step 3: Run the turbine under the same fiber optic probe configuration, and use the data acquisition and processing system to collect the blade arrival and departure data to calculate ψ, Δζ, and Δη.

2. The measuring method of the device for measuring the steady-state deformation of rotating blades inside a casing according to claim 1, characterized in that: Step 3 specifically includes: Under the same fiber optic probe configuration scheme as step 2, start the impeller and run it under stable conditions; The data acquisition and processing system collects the data of blade arrival and departure; Calculate the initial coordinates of the parameter points; Establish the objective function, solve the optimization problem, and obtain ψ, Δζ, and Δη.

3. The measuring method of the device for measuring the steady-state deformation of rotating blades inside a casing according to claim 2, characterized in that: The initial coordinates of the parameter points are: The objective function is: The optimization solution is: my email pre∩suc

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