CN211060879U - A RMS-based Rotating Blade Tip Clearance Measurement System - Google Patents

Abstract

The utility model discloses an RMS-based rotary blade tip clearance measurement system, which comprises a sensor, a rotor and a rotary blade located in an engine casing, a dynamic calibration test bench, a signal preprocessing module, an RMS conversion module, a signal acquisition module and a host computer; the sensor is connected to a signal preprocessing module through a signal transmission cable; the dynamic calibration test bench includes a drive motor, a simulated rotor, a simulated blade, a support platform, a sensor bracket and a high-precision displacement platform; the simulated rotor The high-precision displacement platform and the high-precision displacement platform are both arranged on the upper surface of the support platform; the high-precision displacement platform is provided with a sensor bracket, the simulated rotor is driven by a drive motor, and the circumference of the simulated rotor is provided with cards for clamping the simulated blades at equal intervals. In the slot, a simulated blade is installed on the card slot; when pre-calibrating, the sensor is fixed on the sensor bracket; when the actual measurement is performed, the sensor is fixed on the engine casing.

Description

A RMS-based Rotating Blade Tip Clearance Measurement System

technical field

The utility model belongs to the field of blade tip clearance measurement, in particular to the field of sensor signal processing, in particular to an RMS-based rotary blade blade tip clearance measurement system.

Background technique

Tip clearance refers to the radial distance between the tip (tip) of the rotor blade and the inner wall of the casing in an aero-engine. The tip clearance of aero-engine rotor blades is an important parameter for performance analysis and evaluation, and has an important impact on the working efficiency, safety and reliability of the engine.

The principle of the capacitive tip clearance measurement system is to establish the relationship between the capacitance and the gap based on the capacitance between the sensor probe and the tip of the blade. Among them, the measuring probe is fixed in the casing at the tip of the blade, which constitutes one pole of the capacitor, and the blade tip of the engine rotor will sweep in front of the probe during operation, thereby forming the other pole in the capacitor. The measured capacitance is a function of the electrode geometry, the distance between the electrodes, and the medium between the electrodes. Under normal circumstances, the working medium of the engine is unchanged. For the blade with the same blade tip geometry, the frontal area between the blade tip and the probe is a fixed value, so it is only necessary to establish the relationship between capacitance and distance through calibration. The distance between the tip and the probe, that is, the tip clearance, can be directly measured by capacitance.

For a typical military engine, the blade thickness is 1-2mm, the speed of the blade rotor is about 0-20000r/min, and the number of blades is usually 8-100. Assuming that the rotational speed is 18000r/min and the number of blades is 60, tens of thousands of blade signals need to be collected and processed every second, and the dynamic response time of the sensor is only about 5us, which requires the data sampling frequency to be at least 5MHz. Under such a high sampling frequency, the collection of leaf information usually uses multiple sensors and multiple channels to measure and collect at the same time, resulting in a larger amount of data. The requirements for subsequent data acquisition and processing are relatively high. At the same time, in order to realize the online analysis of the tip clearance data and ensure the real-time display of the waveform, it is also necessary to upload a large number of complex tip clearance acquisition signals in real time, and the real-time requirements of the host computer software are also high, which increases the hardware cost and burden.

Utility model content

In order to overcome the problems in the prior art that the design of the data acquisition circuit requires high sampling frequency and large amount of data transmission, which leads to higher real-time requirements of the subsequent system and more complicated design, the utility model provides an RMS-based rotary blade tip. Clearance measurement system, and design a dynamic calibration scheme and a dynamic calibration test bench for rotating blades to determine the corresponding relationship and calibration relationship between the RMS value of the tip clearance signal and the tip clearance value. According to the obtained calibration relationship between the RMS value of the tip clearance signal and the tip clearance value, an RMS-based rotating blade tip clearance measurement system is built to realize real-time measurement of the tip clearance of the engine blade. It can reduce the difficulty of subsequent signal acquisition and processing; convert high-frequency tip clearance signals to DC level output; improve the efficiency of the measurement system.

The purpose of this utility model is to realize through the following technical solutions:

An RMS-based rotating blade tip clearance measurement system includes a sensor, a rotor and a rotating blade located in an engine casing, a dynamic calibration test bench, a signal preprocessing module, an RMS conversion module, a signal acquisition module and a signal acquisition module connected in sequence. upper computer; the sensor is connected to the signal preprocessing module through a signal transmission cable; the dynamic calibration test bench includes a drive motor, a simulated rotor, a simulated blade, a support platform, a sensor bracket and a high-precision displacement platform; the simulated rotor and high-precision displacement platform The high-precision displacement platforms are all arranged on the upper surface of the support platform; the high-precision displacement platform is provided with a sensor bracket, on which the sensor can be fixed, and the sensor bracket and the sensor are driven by the movement of the high-precision displacement platform to approach or move away from the simulated rotor; The simulated rotor is driven by a driving motor, and the driving motor is connected with the simulated rotor through a coupling; the circumference of the simulated rotor is provided with clamping grooves for clamping the simulated blades at equal intervals, and a simulated rotor is installed on the clamping groove. Blade; during pre-calibration, the sensor is fixed on the sensor bracket of the dynamic calibration test bench to form a dynamic calibration system; during actual measurement, the sensor is fixed on the engine case.

Further, the RMS conversion module includes a full-wave rectifier module, a square/divider function module, a low-pass filter module, a mirror current source module and a buffer amplifier module that are connected in turn; the mirror current source module and the square/divider function modules are connected.

Compared with the prior art, the beneficial effects brought by the technical solution of the present utility model are:

1. Aiming at the problems of large and complex data volume and high signal frequency of the tip clearance signal of the rotating blade of the engine, the present utility model utilizes the RMS value of the tip clearance signal to characterize the tip clearance value, converts the high frequency signal into a DC output, and solves the subsequent problems. Signal processing complex problems.

2. The utility model obtains the calibration relationship between the tip clearance value d and the tip clearance signal RMS value through dynamic calibration, which effectively improves the accuracy of the RMS-based rotating blade tip clearance measurement system.

3. The rotating blade tip clearance measuring system based on the design of the present invention can realize real-time high-precision measurement of the high-speed rotating blade tip clearance in the engine, and effectively ensure the safety during the operation of the engine.

Description of drawings

Fig. 1 is the characteristic and form of the tip clearance signal in the utility model.

FIG. 2 is a schematic front view of the dynamic calibration system in the utility model.

FIG. 3 is a schematic top view structure diagram of the dynamic calibration system of the present invention.

4 is a schematic diagram of a calibration curve and a calibration relationship in the utility model.

FIG. 5 is a schematic structural diagram of the measuring system in the present invention.

FIG. 6 is a schematic structural diagram of the RMS conversion module of the present invention.

Reference numerals: 1-rotor and rotating blades, 2-engine casing, 3-sensor, 4-signal transmission cable, 5-signal preprocessing module, 6-RMS conversion module, 7-signal acquisition module, 8-host computer , 9-drive motor, 10-simulation rotor, 11-simulation blade, 12-support platform, 13-sensor bracket, 14-high-precision displacement platform, 15-full-wave rectifier module, 16-square/divider function module, 17 -Low-pass filter module, 18-Mirror current source module, 19-Buffer amplifier module

Detailed ways

The specific embodiment of the present utility model is that a RMS-based rotating blade tip clearance measurement system is proposed, the tip clearance value is represented by the RMS value of the tip clearance signal, and an RMS conversion circuit is designed to realize the signal RMS value conversion, and proposes a blade dynamic calibration method for this signal processing scheme.

The utility model designs a rotating blade tip clearance measurement system based on RMS, which includes a rotor and a rotating blade 1, an engine casing 2, a sensor 3, a signal transmission cable 4, a signal preprocessing module 5, an RMS conversion module 6, and a signal acquisition module. 7 and the host computer 8; wherein the RMS conversion module 6 includes a full-wave rectification module 15, a square/divider function module 16, a low-pass filter module 17, a mirror current source module 18 and a buffer amplifier module 19; It also includes a dynamic calibration test bench , the dynamic calibration test bench includes a drive motor 9 , a simulated rotor 10 , a simulated blade 11 , a support platform 12 , a sensor bracket 13 and a high-precision displacement platform 14 .

In the dynamic calibration system, the sensor 3 is fixed on the sensor bracket 13 of the dynamic calibration test bench, the simulated rotor 10 and the high-precision displacement platform 14 are both arranged on the upper surface of the support platform 12, and the high-precision displacement platform 14 is provided with a sensor bracket 13, The drive motor 9 is connected with the simulated rotor 10 through a coupling. The circumference of the simulated rotor 10 is provided with card slots for holding the simulated blades at equal intervals, and the simulated blades 11 are installed on the card slots. The sensor 3 passes the signal The transmission cable 4 is connected with the signal preprocessing module 5, the signal preprocessing module 5 is connected with the RMS conversion module 6 through the circuit connection, the RMS conversion module 6 is connected with the signal acquisition module 7 through the connection line, and the signal acquisition module 7 is connected with the upper position through the connection line. Machine 8 is connected.

In the actual measurement system, the sensor 3 is installed on the engine casing 2, the probe end face of the sensor 3 is facing the axis of the rotor and the rotating blade 1, the sensor 3 is connected to the signal preprocessing module 5 through the signal transmission cable 4, and the signal preprocessing module 5 is connected to the RMS conversion module 6 through a circuit connection, the RMS conversion module 6 is connected to the signal acquisition module 7 through a connection wire, and the signal acquisition module 7 is connected to the upper computer 8 through a connection wire.

Referring to Fig. 6, in the RMS conversion module 6, the full-wave rectification module 15, the square/divider function module 16, the low-pass filter module 17, the mirror current source module 18 and the buffer amplifier module 19 are sequentially connected through circuit connections; The source module 18 is connected to the square/divider function module 19 through circuit connections.

In order to overcome the problems of high sampling frequency and large amount of data transmission in the design of data acquisition circuit in the existing blade tip clearance measurement technology, which lead to high real-time requirements of subsequent systems and more complicated design, the present utility model provides a RMS-based system. The method of measuring the tip clearance of the rotating blade is as follows:

During the blade tip clearance measurement, the sensor 3 installed on the engine casing 2 senses the distance d from the end face of the sensor probe to the tip of the rotating blade 1 and converts it into a weak electrical signal. After preprocessing to output the tip clearance signal, it can be considered that other factors are fixed or the influencing factors are small, and the tip clearance signal is regarded as a single-valued function about the distance d, which is expressed as

U=f ₁ (d)

When the rotor and the rotating blade 1 move to the position facing the sensor 3, the distance d between them is the smallest, which is the tip clearance value d ₀ , and the voltage value of the tip clearance signal reaches the maximum, which corresponds to the amplitude of the tip clearance signal. Value A, as shown in Figure 1, can be calculated from the amplitude of the signal tip clearance value:

d ₀ =f ₂ (A)

RMS (Root Mean Square) is called the root mean square value. For a signal with a fixed period, the ratio of its amplitude A _x to its RMS value is a fixed value, which is called the crest factor, which is expressed by CF. relationship is

A _x is the amplitude of the periodic signal, and x _RMS is the RMS value of the periodic signal.

The tip clearance signal can also be regarded as a spike signal with a fixed period, and its period is the time interval from the arrival of the previous blade to the sensor probe position to the next blade leaving the sensor probe position. Therefore, it can be seen from the above relationship that the RMS value of the tip clearance signal is proportional to the amplitude A, so the corresponding relationship between the RMS value of the tip clearance signal and the tip clearance value d ₀ can be established:

d ₀ =f ₃ (U _RMS )

U _RMS is the RMS value of the tip clearance signal.

The RMS value of the sensor output signal can be used to represent the tip clearance value d ₀ , and the tip clearance value of the rotating blade can be calculated by using the calibration relationship between the tip clearance signal RMS value and the tip clearance value d ₀ . The real-time high-precision measurement of the tip clearance of medium and high-speed rotating blades, the specific implementation steps are as follows:

(1) Use the dynamic calibration test bench to build a dynamic calibration system to complete the early dynamic calibration

① Ensure that the sensor 3 is fixed on the sensor bracket of the dynamic calibration test bench, ensure that the sensor 3 is facing the axis of the simulated rotor, the end face of the sensor probe is parallel to the tip of the simulated blade, and the high-precision displacement platform 14 is arranged on the upper surface of the support platform 12. The high-precision displacement platform 14 is provided with a sensor bracket 13, the drive motor 9 is connected to the simulated rotor 10 through a coupling, the simulated blade 11 is installed on the groove on the circumference of the simulated rotor 10 according to the actual situation, and the sensor 3 is transmitted through a signal transmission cable 4 is connected with the signal preprocessing module 5, the signal preprocessing module 5 is connected with the RMS conversion module 6 through the circuit connection line, the RMS conversion module 6 is connected with the signal acquisition module 7 through the connection line, and the signal acquisition module 7 is connected with the host computer 8 through the connection line connected to complete the construction of the tip clearance dynamic calibration system, as shown in Figure 2 and Figure 3;

②Start the drive motor 9, drive the simulated rotor 10 and the simulated blade 11 to rotate and stabilize at a certain speed, run the dynamic calibration system for the tip clearance, and use the host computer 8 to monitor and record the RMS value of the tip clearance signal obtained through the RMS conversion module in real time;

③ Move the high-precision displacement platform 14, drive the sensor bracket 13 to move back and forth, change the tip clearance value, and repeat the above operation ② to obtain the tip clearance signal RMS value under different tip clearance values;

④Dynamic calibration curve diagram is made by the host computer 8, the corresponding relationship between the RMS value of the tip clearance signal and the tip clearance value is determined, and the calibration relationship between the RMS value of the tip clearance signal and the tip clearance value is further deduced: d ₀ = f ₃ (U _RMS ), as shown in Figure 4, it can be seen that the correlation coefficient of this equation is above 0.9, indicating that the calibration curve truly reflects the corresponding relationship between the tip clearance value and the tip clearance signal RMS value, effectively improving the Accuracy of an RMS-based rotating blade tip clearance measurement system.

(2) Build a tip clearance measurement system

As shown in Figure 5, the sensor 3 is installed on the engine casing 2, the probe end face of the sensor 3 is facing the axis of the rotor and the rotating blade 1, the sensor 3 is connected to the signal preprocessing module 5 through the signal transmission cable 4, and the signal preprocessing The processing module 5 is connected to the RMS conversion module 6 through a circuit connection, the RMS conversion module 6 is connected to the signal acquisition module 7 through a connection wire, and the signal acquisition module 7 is connected to the host computer 8 through a connection wire.

(3) Complete the real-time measurement of the tip clearance of the rotating blade

Start the engine, the rotor drives the blade 1 to rotate and sweep the probe of the sensor 3, and the tip clearance signal output by the signal preprocessing module 5 passes through the RMS conversion module 6 to obtain the RMS value of the tip clearance signal, which is used as the result by the signal acquisition module 7. The collection is uploaded to the host computer 8 for calculation, and is substituted into the calibration relationship d ₀ =f ₃ (U _RMS ) obtained above to calculate the tip clearance value, and complete the real-time measurement of the tip clearance of the rotating blade of the engine.

Further, the specific process of RMS value conversion in step (3) is:

① The tip gap signal is first input to the full-wave rectifier module processing 15, and the input voltage signal is converted into a current signal for output. Let the voltage input to the full-wave rectifier module be V _IN , and the current converted and output by the full-wave rectifier module 15 is I _IN ;

②The current I _IN is input into the square/divider function module 16 , in this module, the square of the input current, that is, I _IN ² , is first obtained by the square operation, and then the result is divided by the final feedback input of the mirror current source module 18 . As a result I _OUT get:

The output It is _averaged through the low-pass filter module 17, and the final output result is obtained:

After transformation, the output signal has the following relationship:

The output result is the RMS value of the input signal:

I _OUT =I _RMS ;

3. Input the final result outputted by the low-pass filter module 17 into the mirror current source module 18, and the mirror current source module 18 provides two-way signal outputs; one of the outputs participates in the calculation in the aforementioned square/divider function module as a feedback current, and the mirror current The magnitude of the source output signal is equal to the input of the mirror current source module 18, which is I _OUT ; the other output of the mirror current source module 18 is also I _OUT , which is input to the buffer amplifier module 19 to provide a low-impedance voltage output, which is equivalent to At the beginning of the reverse operation of the full-wave rectifier module 15, the input current is converted into the output voltage V _RMS through the unity gain resistor _RL inside the buffer amplifier module 19;

V _OUT =R _L ×I _OUT =V _RMS

After the above process, the RMS value of the tip clearance signal is finally obtained.

The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above-mentioned specific embodiments are only illustrative and not restrictive. Without departing from the scope of protection of the purpose of the present invention and the claims, those of ordinary skill in the art can also make many specific transformations under the inspiration of the present invention, which all belong to the protection scope of the present invention. Inside.

Claims (2)

1. A rotating blade tip clearance measuring system based on RMS comprises a sensor, a rotor and a rotating blade, wherein the rotor and the rotating blade are positioned in an engine casing; the sensor is connected with the signal preprocessing module through a signal transmission cable; the dynamic calibration test bed comprises a driving motor, a simulation rotor, a simulation blade, a supporting platform, a sensor bracket and a high-precision displacement platform; the simulation rotor and the high-precision displacement platform are both arranged on the upper surface of the supporting platform; the high-precision displacement platform is provided with a sensor support, a sensor can be fixed on the sensor support, and the sensor support and the sensor are driven to be close to or far away from the simulation rotor through the movement of the high-precision displacement platform; the simulation rotor is driven by a driving motor, and the driving motor is connected with the simulation rotor through a coupler; clamping grooves for clamping the simulation blades are formed in the circumference of the simulation rotor at equal intervals, and the simulation blades are additionally arranged on the clamping grooves; when in pre-calibration, a sensor is fixed on a sensor bracket of a dynamic calibration test bed to form a dynamic calibration system; during actual measurement, the sensor is fixed on the engine casing.

2. An RMS-based rotating blade tip clearance measurement system as claimed in claim 1, wherein said RMS conversion module includes a full wave rectifier module, a squarer/divider function module, a low pass filter module, a mirror current source module and a buffer amplifier module connected in series; the mirror current source module is connected with the square/divider functional module.

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