A blade tip clearance measurement device and method based on a closed environment

Abstract

The present invention discloses a blade tip clearance measuring device and method based on a closed environment. The blade tip clearance measuring device is used for being nested and installed on a rotor blade that needs to be detected. The rotor blade is located in a casing. The blade tip clearance measuring device comprises a capacitive sensor, a detection circuit unit, a wireless transmission module, a power supply battery and a fastening device. The capacitive sensor is arranged on the top of the blade tip clearance measuring device. The radial position of the blade tip clearance measuring device is adjusted by adjusting the fastening device so that the electrode plate of the capacitive sensor is parallel to the top of the rotor blade. The capacitive sensor, the detection circuit unit and the wireless transmission module are connected in sequence. The power supply battery is used for providing the electric energy required by the blade tip clearance measuring device.

Description

Technical Field

[0001] The present invention relates to the field of blade tip clearance measurement, and in particular to a blade tip clearance measurement device and method based on a closed environment. Background Art

[0002] In rotating machinery such as aircraft engines, gas turbines, and steam turbines, the tiny distance between the top of the rotor blade and the inner wall of the casing is called the tip clearance, which is one of the important parameters affecting the performance of rotating machinery. Reducing the tip clearance can reduce fuel consumption and significantly improve the operating efficiency of rotating machinery, but too small a tip clearance value will cause friction between the blade and the casing, seriously endangering the safe operation of the rotating machinery. Therefore, the tip clearance measurement technology is of great significance to improving the performance of rotating machinery and ensuring the safe operation of rotating machinery.

[0003] At present, mature methods for measuring blade tip clearance include discharge probe method, laser triangulation method, fiber bundle method, eddy current method, capacitance method and microwave method. Except for the eddy current method, which does not require opening holes when the casing is thin, the other methods all require opening holes on the casing surface to install sensors, and measure the gap value by measuring the distance between the blade tip and the sensor tip. This method destroys the airtightness of the internal environment of the rotating machinery and is prone to fluid leakage. At the same time, opening holes in the casing is permanent damage, and once the measuring point is changed, the hole must be opened again, causing great damage to the rotating machinery and easily leading to failures.

[0004] In order to ensure the airtightness of the rotating machinery environment, the common tip clearance measurement method is the plasticine method. Apply the plasticine evenly to the inner wall of the casing, and the high-speed rotating blades will cut off the excess plasticine. After stopping, measure the height of the remaining plasticine, which is the minimum tip clearance during the working process. This method is relatively simple to implement, has low cost, and will not cause any damage to the rotating machinery, but the measurement accuracy is low. It can only measure the minimum clearance of the first-stage blade during the entire working process, and can only be measured when starting and stopping, and the real-time value of the tip clearance cannot be known. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art that the closed environment of rotating machinery is damaged, the gap value measurement accuracy is low, and only the minimum gap value of the first-stage rotor blade in the entire working process can be measured, and the real-time display of multiple blade gap values ​​cannot be achieved. A blade tip clearance measurement device and method suitable for a closed environment is provided, which can achieve high-precision and real-time measurement of multiple blades, has a simple structure and low cost.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A blade tip clearance measuring device based on a closed environment is used for being nested and installed in a rotor blade that needs to be detected. The rotor blade is located in a casing. The blade tip clearance measuring device comprises a capacitive sensor, a detection circuit unit, a wireless transmission module, a power supply battery and a fastening device. The capacitive sensor is arranged on the top of the blade tip clearance measuring device. The radial position of the blade tip clearance measuring device is adjusted by adjusting the fastening device so that the electrode plate of the capacitive sensor is parallel to the top of the rotor blade. The capacitive sensor, the detection circuit unit and the wireless transmission module are connected in sequence, and the power supply battery is used to provide the electric energy required by the blade tip clearance measuring device.

[0008] Furthermore, the detection circuit unit includes a signal modulation module and a main control chip.

[0009] The present invention provides another technical solution as follows:

[0010] A blade tip clearance measurement method in a closed environment comprises the following steps:

[0011] (301) The capacitive sensor converts the displacement signal from the top of the rotor blade to the inner wall of the casing into a change in capacitance value, and transmits it to the detection circuit unit through the sensor cable;

[0012] (302) The detection circuit unit includes a signal modulation module and a main control chip, and the main control chip includes an ARM and an FPGA; the signal modulation module receives the capacitance signal transmitted by the capacitance sensor cable, converts the capacitance signal into an electrical signal after noise removal, and transmits the electrical signal to the main control chip; the main control chip performs corresponding calculations based on the received electrical signal, calculates the blade tip clearance value by reverse calculation of the electrical signal, and transmits the obtained blade tip clearance value to the wireless transmission module;

[0013] (303) The wireless transmission module receives the blade tip clearance value and sends the blade tip clearance value data to the system host computer via wireless transmission;

[0014] (304) The host computer receives the blade tip clearance value and displays it in the host computer software.

[0015] Another technical solution provided by the present invention is as follows:

[0016] A design method for a blade tip clearance measurement device in a closed environment comprises the following steps:

[0017] (501) To ensure the gas flow capacity of the rotor blades, the housing height H of the tip clearance measuring device should be less than half of the rotor blade radius R, that is,

[0018] H<0.5R;

[0019] (502) When there are several blades on the same stage of the rotor that require tip clearance measurement, it is necessary to install tip clearance measurement devices on different blades; in order to enable adjacent rotor blades to be equipped with tip clearance measurement devices, the width W of the tip clearance measurement device housing should meet

[0020]

[0021] Where N is the number of rotor blades, r is the radius of the rotor hub, and R is the radius of the rotor blade;

[0022] (503) There is an error in the capacitance signal of the capacitance sensor:

[0023]

[0024] in, ε is the dielectric constant, d is the tip clearance value, a is the characteristic length of the capacitance sensor plate, and θ is the plate inclination angle; when the capacitance sensor signal error is less than ΔC0, its error can be ignored or eliminated by circuit compensation, and then when the inclination angle is less than θ0, the error introduced by the plate inclination angle change can be ignored or eliminated by circuit compensation, where ΔC0 and θ0 are both constants, which are determined by the technical level and measurement accuracy requirements;

[0025] (504) The capacitive sensor is a capacitive plate type or a flexible sensing device;

[0026] (505) Each blade tip clearance measurement device can be equipped with at least two capacitive sensors for measuring different positions of the same rotor blade.

[0027] Furthermore, a single-stage rotor of a rotating machine can be equipped with several blade tip clearance measurement devices. Each rotating machine contains multiple-stage rotors. Through networking, the fusion of several measurement blade data of the multiple-stage rotors can be achieved, thereby obtaining the overall operating status of the rotating machine.

[0028] The invention discloses an application of a blade tip clearance measuring device in a closed environment, which is suitable for real-time measurement of rotor blade tip clearance of rotating machinery such as aircraft engines, gas turbines and steam turbines in a closed environment.

[0029] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0030] 1. The blade tip clearance measuring device of the present invention is installed and nested on the rotor blade to be detected, so that the rotor blade tip clearance value can be measured in the closed environment of the rotating machine casing, without drilling holes on the casing to install the sensor, thus avoiding damage to the rotating machine structure;

[0031] 2. The blade tip clearance measurement device of the present invention can send the measurement data to the host computer in real time through the wireless transmission module, so it can perform real-time online measurement when the rotor blades rotate at high speed, overcoming the deficiency of the traditional clearance measurement method that the blade tip clearance can only be measured at the start and stop time;

[0032] 3. The blade tip clearance measurement device of the present invention can send the measurement data to the host computer in real time through the wireless transmission module, and can realize the real-time online measurement of the blade tip clearance of any rotor blade, thus overcoming the deficiency of the traditional clearance measurement method that can only measure the minimum value of the blade tip clearance during the working process;

[0033] 4. Since the blade tip clearance measuring device of the present invention is small in size, exquisitely designed, and will not cause structural damage to the rotating machinery, multiple measuring devices can be installed on a single-stage blade at the same time;

[0034] 5. Through wireless transmission technology, the tip clearance values ​​of multiple blades of multi-stage rotors can be measured simultaneously;

[0035] 6. Through wireless transmission technology, multiple measuring devices can be networked, thus providing good technical support for the overall operating status monitoring and data fusion of rotating machinery;

[0036] 7. By selecting a flexible sensor device, it can be used in complex environments with blades of different shapes and narrow gaps;

[0037] 8. Aiming at the closed environment of rotating machinery, a low-cost, high-precision blade tip clearance measurement device is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the installation of the blade tip clearance measuring device of the present invention is shown.

[0039] Figure 2 A schematic structural diagram of the blade tip clearance measuring device of the present invention is shown.

[0040] Figure 3 A schematic diagram of the flexible sensing structure of the blade tip clearance measurement device in the present invention is shown.

[0041] Figure numerals: 1-tip clearance measuring device, 2-rotor blade, 3-capacitive sensor, 4-fastening device, 5-casing, 6-power supply battery, 7-detection circuit unit, 8-wireless transmission module, 9-flexible sensing device, 10-obstacle. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] The blade tip clearance measuring device 1 provided by the present invention in a closed environment can be nested and installed on the rotor blade 2 to be detected, such as Figure 1 As shown. The tip clearance measuring device 1 has a capacitive sensor 3 at its top. The radial relative position of the tip clearance measuring device 1 is adjusted so that the capacitive sensor 3 is placed exactly at the top of the rotor blade 2 to be measured, and the electrode plate of the capacitive sensor 3 is kept parallel to the top of the rotor blade 2 as much as possible. After the tip clearance measuring device 1 is positioned, it is fixed to the rotor blade 2 with a fastening device 4 to prevent it from moving during the high-speed rotation of the rotor blade 2, thereby affecting the accuracy of the clearance measurement data.

[0044] The tip clearance measuring device 1 of the present invention is based on the capacitance sensor ranging technology, and calculates the tip clearance value of the rotor blade 2 by measuring the capacitance change between the central electrode installed at the top of the rotor blade 2 and the inner wall of the casing 5. When the blade is stationary, the capacitance value from the central electrode of the capacitance sensor to the casing is:

[0045]

[0046] Among them, ε is the dielectric constant, S is the plate area, and d1 is the distance from the center electrode of the capacitive sensor to the inner wall of the casing. Because the tip clearance measurement device 1 is fixed to the rotor blade 2 by the fastening device 4, it can be considered that the distance from the center electrode of the capacitive sensor 3 to the top of the rotor blade 2 is a fixed value d0, so when the rotor is stationary, the tip clearance of the rotor blade is:

[0047] d=d1+d0

[0048] During operation, the rotor blade 2 rotates at high speed under high temperature. Strong centrifugal force and thermal stress will cause the blade to elongate. Under the fixation of the fastening device 4, the tip clearance measurement device 1 will move along with the elongation of the rotor blade 2, so the radial relative position between it and the rotor blade 2 will not change. However, the distance from the center electrode of the capacitive sensor 3 to the top of the rotor blade 2 may change due to the influence of high temperature and centrifugal force, so when the rotor is in motion, the tip clearance of the blade is:

[0049] d=d1+d′0

[0050] Wherein, d'0 is the distance from the central electrode of the capacitance sensor to the top of the rotor blade when the rotor is in motion. Therefore, the blade tip clearance measuring device 1 of the present invention can realize the dynamic measurement of the blade tip clearance when the rotor blade is in high-speed motion.

[0051] In summary, the structural design of the blade tip clearance measuring device 1 is very critical. The structure of the blade tip clearance measuring device 1 of the present invention is as follows: Figure 2As shown, it is composed of a capacitive sensor 3, a fastening device 4, a power supply battery 6, a detection circuit unit 7, a wireless transmission module 8 and other parts.

[0052] First, the capacitive sensor 3 converts the displacement signal from the top of the rotor blade 2 to the inner wall of the casing 5 into a change in capacitance value, and transmits it to the detection circuit unit through the sensor cable. Then the detection circuit unit 7 includes the signal modulation module of the sensor, the main control chip, etc. The signal modulation module of the sensor receives the capacitance signal transmitted by the sensor cable, removes noise, converts the capacitance signal into an electrical signal, and transmits the electrical signal to the main control chip. The main control chip includes ARM and FPGA, etc., which perform corresponding calculations based on the received electrical signal, calculate the tip clearance value by back-calculating the electrical signal, and transmit the tip clearance value to the wireless transmission module. Finally, the wireless transmission module 8 receives the tip clearance value and sends the data to the system host computer via wireless transmission. The host computer receives the tip clearance value and displays the value in the host computer software.

[0053] The blade tip clearance measuring device 1 is powered by a battery 6 to ensure the normal operation of the entire system. The blade tip clearance measuring device 1 is fixed to the rotor blade 2 by a fastening device 4, which can ensure that the relative position between the measuring device 1 and the rotor blade 2 does not move under the harsh working conditions of high temperature, high pressure and high speed rotation.

[0054] Furthermore, in order to enable the tip clearance measuring device 1 to work normally in a closed environment of a rotating machine, the tip clearance measuring device should be designed according to the working environment of the rotor blades of the rotating machine and referring to the measurement requirements of the tip clearance.

[0055] The details are as follows:

[0056] (1) Due to the limited space on the rotor of a rotating machine in a closed environment, the tip clearance measuring device should be designed to be compact. In order to ensure the gas flow capacity of the rotor blades, the shell height H of the tip clearance measuring device should be less than half of the rotor blade radius R, that is,

[0057] H<0.5R

[0058] (2) When there are multiple blade tip clearances on the same rotor stage that require measurement, multiple blade tip clearance measurement devices must be installed on different blades. In order to allow adjacent rotor blades to be equipped with clearance measurement devices, the width W of the device housing should meet

[0059]

[0060] Where N is the number of rotor blades, r is the radius of the rotor hub, and R is the radius of the rotor blade.

[0061] (3) The capacitive sensor 3 is installed at the top of the rotor blade 2. During installation, the capacitive sensor plate should be kept parallel to the blade tip as much as possible. However, due to installation errors, high temperature, high pressure or blade rotation, the capacitive sensor plate may have an inclination angle, which may cause errors in the capacitive signal of the capacitive sensor:

[0062]

[0063] in, ε is the dielectric constant, d is the tip clearance value, a is the characteristic length of the capacitance sensor plate, and θ is the plate inclination angle. Determined by the detection capability and calculation level of the circuit, when the capacitance signal error is less than ΔC0, its error can be ignored or eliminated through circuit compensation. It can be known that when the inclination angle is less than Δ θ When , the error introduced by the change of the plate inclination angle can be ignored or eliminated by circuit compensation, where ΔC0 and θ0 are constants determined by the technical level and measurement accuracy requirements.

[0064] (4) In order to adapt to different application environments, capacitive sensors have different forms. One is a capacitive plate type, i.e., a capacitive sensor 3, which is mainly used in environments with simple internal structures and no complex obstacles; another is a flexible sensor device 9, which uses a flexible PCB and is suitable for environments with different blade shapes and complex structures in steam turbines or aircraft engines, such as Figure 3 As shown. The flexible sensor device 9 can bypass complex obstacles 10, pass through narrow gaps, and be fixed to the blade surface by magnets. Under high-speed rotating working conditions, the relative position of the flexible sensor device 9 will not move with the rotor blade. The working principle and design process of the flexible sensor device 9 are still as described above, but the structure of the sensor itself is slightly different.

[0065] (5) Each blade tip clearance measurement device can be equipped with multiple sensors to measure different positions of the same rotor blade. In addition, a single-stage rotor of a rotating machine can be equipped with multiple blade tip clearance measurement devices. Each rotating machine contains multiple rotors. Through networking, the fusion of multiple measurement blade data of the multi-stage rotor can be achieved, thereby ultimately obtaining the overall operating status of the rotating machine.

[0066] 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 solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A design method for a blade tip clearance measuring device in a closed environment, wherein the blade tip clearance measuring device is used to be nested and installed on a rotor blade that needs to be detected, and the rotor blade is located in a casing. The blade tip clearance measuring device includes a capacitive sensor, a detection circuit unit, a wireless transmission module, a power supply battery and a fastening device. The capacitive sensor is arranged on the top of the blade tip clearance measuring device, and the radial position of the blade tip clearance measuring device is adjusted by adjusting the fastening device so that the electrode plate of the capacitive sensor is parallel to the top of the rotor blade; the capacitive sensor, the detection circuit unit and the wireless transmission module are connected in sequence, and the power supply battery is used to provide the electric energy required by the blade tip clearance measuring device, characterized in that: The following steps are involved: (501) To ensure the gas flow capacity of the rotor blades, the housing height H of the tip clearance measuring device should be less than half of the rotor blade radius R, that is, H<0.5R; (502) When there are several blades on the same stage of the rotor that require tip clearance measurement, it is necessary to install tip clearance measurement devices on different blades; in order to enable adjacent rotor blades to be equipped with tip clearance measurement devices, the width W of the tip clearance measurement device housing should meet Where N is the number of rotor blades, r is the radius of the rotor hub, and R is the radius of the rotor blade; (503) There is an error in the capacitance signal of the capacitance sensor: Wherein, ε is the dielectric constant, d is the tip clearance value, a is the characteristic length of the capacitance sensor plate, and θ is the plate inclination angle; when the capacitance sensor signal error is less than ΔC0, its error can be ignored or eliminated by circuit compensation, and then when the inclination angle is less than θ0, the error introduced by the change of the plate inclination angle can be ignored or eliminated by circuit compensation, where ΔC0 and θ0 are both constants, which are determined by the technical level and measurement accuracy requirements; (504) The capacitive sensor is a capacitive plate type or a flexible sensing device; (505) Each blade tip clearance measurement device can be equipped with at least two capacitive sensors for measuring different positions of the same rotor blade.

2. The design method of a blade tip clearance measurement device in a closed environment according to claim 1, characterized in that: A single-stage rotor of a rotating machinery can be equipped with several blade tip clearance measurement devices. Each rotating machinery contains multiple-stage rotors. Through networking, the fusion of several measurement blade data of the multi-stage rotors can be achieved, thereby obtaining the overall operating status of the rotating machinery.

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