Multi-channel pressure acquisition and calibration system and method for high-speed rotating equipment

Abstract

The application relates to a multi-channel pressure acquisition and calibration system and method suitable for high-speed rotating equipment, which comprises a rotating pressure switching system, a pressure signal dynamic-static conversion system and a rotating automatic calibration system; the pressure signal dynamic-static conversion system is used for converting the along-the-way pressure signal of an experimental piece tested by a rotating experiment table and a pressure control valve control electric signal from the rotating end to the static end of an experimental system through a slip ring and a pressure signal dynamic-static conversion joint; the rotating automatic calibration system comprises a mathematical method for deducing a rotating pressure correction method and an experimental calibration system micro-pressure leakage; when the experimental calibration system micro-pressure leakage exists, the known pressure in the experimental piece is kept, the micro-pressure leakage existing in each joint and the pressure signal dynamic-static conversion joint in the pressure test system is tested, and the pressure test system is calibrated. The application solves the rapid test of multi-channel pressure of high-speed rotating equipment, corrects the pressure error generated by the pressure pipe of a high-speed rotating experiment table, and realizes the real-time calibration of the multi-channel pressure loss of high-speed rotating equipment.

Description

Technical Field

[0001] This invention relates to the field of flow testing of turbomachinery, and more specifically to a multi-channel acquisition and calibration system for pressure in a rotating turbomachinery experiment. Background Technology

[0002] Aero-turbine engines represent a major breakthrough in aviation propulsion. Since the 1940s, aero-engines have made continuous breakthroughs in nearly eighty years of development, with a significant increase in thrust. However, this has led to a problem: the turbine inlet temperature has been constantly rising, far exceeding the temperature resistance limit of the materials. Various advanced cooling technologies have been gradually applied to turbine blades. To ensure engine efficiency, precise measurements of the flow within the turbine machinery are required, such as the pressure distribution within the moving blade channels and the pressure distribution within the turbine cooling structure. With the increasing demands for refined turbine machinery design, sufficient experimental data is needed to support the design of engine blade profiles and cooling structures, and more precise pressure testing capabilities are required to obtain detailed pressure distributions within rotating components.

[0003] The challenge of rotating pressure testing lies in measuring pressure during high-speed rotation. Currently, there are two basic approaches to rotating pressure testing: using a sensor for pressure measurement and using a pressure-sensitive element (PSP) to measure pressure.

[0004] Sensor pressure measurement can only measure pressure at discrete points, but its accuracy can generally reach 0.1%, making it a high-precision pressure test method. Currently, there are two main methods for sensor pressure measurement. The first method involves placing the sensor on the rotating section and extracting the signal through a slip ring. Placing the sensor on the rotating end allows for direct placement at the measurement position on the test piece when the rotation speed is low, acquiring dynamic pressure signals. Because the distance between the sensor and the measurement point is relatively short, it is advantageous for dynamic measurement. (This was proposed by Luo Xiang et al. from Beijing University of Aeronautics and Astronautics.) [1,2] This method is used for pressure testing within the turbine disk cavity. At higher speeds, some scholars have proposed placing the pressure sensor at a lower radius to reduce the effect of rotation on the sensor. Zhao Shu et al. from Northwestern Polytechnical University... [3] Zhang Dawei et al. from Beijing University of Aeronautics and Astronautics [4] This method was used for rotational pressure testing. The sensor was placed at the stationary end, and the pressure tap was led out through a rotary joint. Since the sensor was placed at the stationary end, it was unaffected by rotation, ensuring its stability and accuracy. (Deng Hongwu, Beijing University of Aeronautics and Astronautics) [5,6] Qiu Lu [7] Li Yang [8]This method is commonly used to measure rotational pressure. Both of these testing methods have problems. Placing the sensor at the rotating end requires a very small sensor size, ideally positioned at the axis to minimize the impact of rotation. However, rotational effects are unavoidable, and the sensor's effect cannot be easily corrected. Furthermore, transmitting the signal to the stationary end via a pressure tube inevitably leads to air leakage at the rotary joint, causing measurement errors due to the stationary pressure sensor. Therefore, to obtain accurate rotational pressure, pressure calibration is necessary to eliminate systematic errors caused by rotation.

[0005] Pressure-sensitive coatings (PSPs) can be used to measure pressure distribution on a surface. Rotational pressure distribution can be obtained by measuring luminescence intensity using a camera. However, the accuracy of PSPs is much lower than that of sensors, making it impossible to obtain precise pressure distribution. Placing the camera at the rotating end is problematic because the camera cannot withstand high centrifugal forces, preventing high-speed pressure field imaging. Using phase-locked loop technology to capture images at a stationary end is also limited by exposure time and cannot measure velocity fields at high speeds.

[0006] In the measurement of rotating pressure on turbine blades, due to the relatively small pressure difference along the blade, sensors are often used to measure the pressure at local points to improve testing accuracy. However, the number of pressure measurement points is also relatively limited. In previous rotating experiments, due to the limitations of the number of pressure sensors and rotating pressure taps, pressure testing often relied on two points to determine the global resistance characteristics or local features of the pressure measurement points.

[0007] As research into rotating turbomachinery deepens, there is a need to deploy more measuring points to obtain detailed flow conditions at the rotating end. However, for high-speed rotating test benches, limitations such as space constraints and high rotational speeds make multi-channel pressure testing difficult to achieve.

[0008] The existing technology references are as follows:

[0009] [1] Hu Yanli, Guo Wen, Wang Lei, et al. Pressure loss characteristics of the inlet rotating disk cavity of the reverse swirl nozzle [J]. Journal of Aerospace Power, 2016, 31(08): 1866-1873.

[0010] [2] Cai Xu, Luo Xiang, Xu Guoqiang, et al. Experimental study on pressure characteristics of dual rotating disk cavity[J]. Journal of Aerospace Power, 2013, 28(10):2267-2275.

[0011] [3] Zhao Shu. Study on flow and heat transfer characteristics inside a rotating channel under rotating conditions [D]. Northwestern Polytechnical University, 2014.

[0012] [4] Zhang D, Li H, Tian Y, et al. Effects of a high Reynolds number and rotation on the leading-edge heat transfer of a ribbed cooling channel with cross-section consisting of a semicircle and a rectangle[J]. International Journal of Heat and Mass Transfer, 2022, 188: 122646.

[0013] [5]Deng H, Li H, Tao Z, et al. Effect of Blockage Ratio on Heat Transfer and Pressure Drop in Rotating Ribbed Channels at High Rotation Numbers[J]. Journal of Thermal Science, 2021, 30(3):902-913.

[0014] [6] Chen Hao, Deng Hongwu, Cheng Junhua, et al. Experimental realization and verification of flow resistance characteristics in a rotating channel [J]. Journal of Aerospace Power, 2015, 30(11):2623-2629.

[0015] [7]Qiu L, Deng HW, Sun JN, et al. Pressure drop and heat transfer inrotating smooth square U-duct under high rotation numbers [J]. International Journal of Heat and Mass Transfer, 2013, 66: 543-552.

[0016] [8] Li Y, Deng HW, Xu GQ, et al. HEAT TRANSFER AND PRESSURE DROP INAROTATING TWO-PASS SQUARE CHANNEL WITH DIFFERENT RIBS AT HIGH ROTATIONNUMBERS[C]. ASME Turbo Expo: Turbine Technical Conference and Exposition, 2015. Summary of the Invention

[0017] In turbomachinery structures, pressure testing of complex cooling structures is hampered by limitations in rotational pressure measurement capabilities, making it impossible to obtain accurate pressure data or acquire sufficient pressure test point data. This problem is particularly pronounced in high-speed test benches. To address the technical challenges of multi-channel pressure testing on high-speed test benches, this invention proposes a multi-channel pressure acquisition and calibration system suitable for high-speed rotating equipment, the technical solution of which is as follows:

[0018] This paper takes a high-speed rotating turbine blade cooling structure test rig as an example to introduce a multi-channel pressure acquisition and calibration system for high-speed rotating experiments. The multi-channel pressure acquisition and calibration system for high-speed rotating experiments includes a rotating pressure switching system, a pressure signal dynamic-to-static conversion system, and a rotating automatic calibration system, characterized by:

[0019] The rotary pressure switching system: Through a pressure scanning system and control device composed of multi-way pressure control valves, it enables rapid measurement of multiple pressure measurement points on a high-speed test bench, and obtains accurate pressure along the test piece for rotary flow resistance characteristic testing of the measurement points.

[0020] The pressure signal dynamic-to-static conversion system: uses a slip ring and a pressure signal dynamic-to-static conversion joint to convert the pressure signal along the test piece tested on the rotating test bench and the control electrical signal of the pressure control valve from the rotating end to the stationary end of the test system, thereby realizing the signal transmission between the stationary end and the rotating end of the test system.

[0021] The rotary automatic calibration system detects the pressure signals of the multi-pressure connectors in the rotary test bench and determines whether there is micro-pressure leakage at the dynamic-static conversion connector, thereby calibrating the multi-pressure connections.

[0022] This invention also discloses a multi-channel pressure acquisition and calibration method suitable for high-speed rotating equipment, including the aforementioned multi-channel pressure acquisition and calibration system suitable for high-speed rotating test benches, characterized in that the calibration method includes the following steps:

[0023] Step 1: During the experiment, the flow regulating valves at the inlet and outlet of the rotary multi-channel pressure acquisition and calibration system experimental platform are kept at a certain opening to control the flow and pressure in the experimental specimen; before the rotary flow resistance characteristic test experiment begins, the system first enters the calibration mode.

[0024] Step 2: Adjust the pressure inside the test piece (6) to match the experimental state. When stationary, close the flow control valve (3) and the flow control valve (2) in sequence; adjust the opening of the flow control valve (3) to 1% to slowly release the gas, so that the pressure inside the test piece (6) remains consistent with the experimental state; at this time, there is no gas flow in the channel, and the pressure in the channel is also consistent with the experimental state;

[0025] Step 3: Perform micro-pressure leakage calibration on each pressure measuring pipeline. The rotating solenoid valve disc (8) is equipped with 48 pressure control valves. Switch the pressure control valves (9) in sequence and read the differential pressure reading when the differential pressure sensor (12) is not venting. The reading at this time is the micro-pressure leakage value of the system when it is stationary.

[0026] Step 4: Start the high-speed rotating test bench with the motor and repeat the above steps at different speeds. Record the micro-pressure leakage value when each pressure control valve (9) of the system is opened within the experimental speed range, and form a micro-pressure leakage error table for all measuring points at different speeds. The micro-pressure leakage error table serves as the benchmark for testing.

[0027] Step 5: During the rotation experiment, according to the experimental requirements, the pressure at each point in the experimental piece under different inlet Reynolds numbers and different rotation speeds is scanned in sequence, and the differential pressure sensor (12) records the pressure reading at each measuring point; combined with the micro-pressure leakage error table, the values ​​are corrected to obtain the corrected pressure distribution at each point in the experimental piece.

[0028] Step 6: Using the pressure correction theory derived mathematically, the actual pressure at the measuring point is derived from the sensor reading; due to the centrifugal pressure gradient generated in the pressure tube by the centrifugal force of rotation, there is a difference between the reading of the pressure at the axis, i.e., the differential pressure sensor (12), and the reading at the measuring point position inside the experimental piece.

[0029] This section presents a method for deriving the readings of the measuring points inside the experimental specimen from the readings of the differential pressure sensor (12).

[0030]

[0031] Where P(x) is the pressure at the measuring point with radius x; P0 is the pressure introduced into the shaft at the measuring point, which is also the reading of the differential pressure sensor (12); Ω is the rotational speed, in rad / s; R is the gas constant, with a value of 287.06 J / (Kg·K); and T is the gas temperature in the pressure tapping tube.

[0032] Beneficial effects

[0033] 1) Solved the problem of rapid testing of multiple pressures on a high-speed rotating test bench;

[0034] 2) The pressure error caused by the pressure tapping tube of the high-speed test bench was corrected;

[0035] 3) Real-time calibration of multi-channel pressure loss on the high-speed rotating test bench was achieved. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a multi-channel pressure acquisition and calibration system suitable for high-speed rotating test benches;

[0037] Figure 2 Diagram of an integrated pressure control valve system;

[0038] Figure 3 For the gas path and control of the pressure acquisition system;

[0039] Figure 4 This is a schematic diagram of the rotational pressure test and pressure application method;

[0040] Figure 5 A pressure testing system consisting of a pressure tap and a pressure sensor;

[0041] 1. High-pressure gas tank; 2. Flow control valve for the air inlet channel; 3. Flow control valve for the air outlet channel; 4. Rotary air inlet connector; 5. Rotary disc; 6. Experimental piece; 7. Counterweight; 8. Rotary solenoid valve disc; 9. Rotary pressure control valve group; 10. Pressure signal dynamic-static conversion connector; 11. Pressure sensor cluster; 12. Pressure sensor. Detailed Implementation

[0042] The air path section of the experimental platform for the rotating multi-channel pressure acquisition and calibration system is shown in the figure.

[0043] 1. The high-pressure gas tank provides high-pressure gas to the experimental specimen;

[0044] 2 is the flow control valve for the air intake channel, which controls the air intake flow of the system.

[0045] 3 is the flow control valve for the air outlet channel, which controls the pressure inside the experimental piece (6).

[0046] 4 is a rotary air inlet connector, which allows the required air to be transferred from the stationary end to the rotating end. A ceramic sealing ring is used for rotary flow sealing to reduce gas leakage.

[0047] 5 is the rotating disk, which is the mounting position for the experimental piece and can achieve a maximum speed of 4000 rpm.

[0048] 6 is the experimental piece, installed on one side of the rotating disk.

[0049] 7 is a counterweight block, installed on the opposite side of the test piece to balance the weight of the test piece, maintain the balance of the rotating disk during rotation, and reduce vibration during the experiment.

[0050] 8 represents a rotary solenoid valve disc. It contains 48 pressure control valves, enabling a maximum of 48 differential pressure tests in the experimental system.

[0051] 9 represents a rotary pressure control valve group. These valves are placed on the circumferential wall of the solenoid valve disc and achieve rapid measurement of multiple pressure channels through a group scanning method.

[0052] 10 is a pressure signal dynamic-to-static conversion connector. It is used to convert the pressure signal from the rotating end to the stationary end.

[0053] 11 is a pressure sensor cluster. It integrates multiple differential pressure sensors and absolute pressure transmitters.

[0054] 12 is a pressure sensor that measures the pressure data extracted from the experimental specimen.

[0055] In the experiment, the cooling gas required for the experimental specimen was compressed by a compressor and stored in a high-pressure gas tank. During the experiment, the inlet and outlet flow valves were opened, and the flow rate through the experimental specimen and the gas pressure inside the specimen were controlled by adjusting the opening degree of the inlet and outlet flow control valves. This control of flow rate and pressure was intended to match the Reynolds number at the inlet of the experimental specimen with the Reynolds number parameters of the actual blade.

[0056] Example 1

[0057] The multi-channel pressure acquisition and calibration system for high-speed rotating equipment consists of three main parts: a rotation pressure switching system, a pressure signal dynamic-static conversion system, and a rotation automatic calibration system.

[0058] The rotary pressure switching system is the core of this system. To accommodate high speeds (maximum speed > 4000 rpm), the pressure switching connectors for dynamic and static pressure conversion require the air paths to be positioned in small-radius locations, significantly limiting the number of pressure air paths. While pressure scanning valves are commonly used at the stationary end to measure multiple pressures, placing them at the rotating end at high speeds greatly affects test accuracy. Therefore, the most reliable method is to construct a pressure scanning system at the rotating end and place the sensor at the stationary end, thus reducing the influence of rotation. To solve the problem of acquiring multiple pressure signals on a high-speed rotating test bench, a rotary module integrating a pressure control valve group is installed at the rotating end. 48 reliable miniature pressure control valves are selected to control the on / off of pressure lines at high speeds. The pressure control valve group is grouped, controlling the number of valves in each group, enabling rapid scanning of each pressure path within a short time, thereby greatly improving the pressure measurement capability of the rotary pressure test. The solenoid valve panel is as follows: Figure 1As shown, 24 pressure control valves are arranged on a circle with a radius of only 45 mm to minimize the impact of centrifugal force on the valves. The experimental setup includes two solenoid valve discs, providing switching capability for 48 pressure measurement points. The pressure control valves of the switching system are controlled using a 4056SO module.

[0059] Pressure acquisition gas path and control, such as Figure 2 As shown in the diagram. Since we are more concerned with the pressure difference between test points when measuring the flow resistance characteristics of turbine blade cooling channels, this system extensively uses differential pressure sensors for full-field pressure testing to improve the accuracy of differential pressure measurement. Using the inlet pressure P0 of the experimental piece as a reference, the absolute pressure transmitter measures the absolute pressure at the channel inlet, while the differential pressure sensor measures the pressure difference between any point in the channel and the inlet. Therefore, this experimental system, with the help of a rotating pressure scanning system, can achieve up to 49 pressure measurements, meeting the pressure testing requirements of complex structures.

[0060] Six pressure control valve groups are set in the rotary solenoid valve disc, each containing eight pressure control valves, with one valve corresponding to each rotary joint. The opening and closing of the pressure control valves are controlled by computer software. The signal is introduced to the rotary end through a slip ring, and the Adam 4056 controller controls the on / off state of the pressure control valves. The Adam 4056 can precisely control the on / off state of any single pressure control valve. In the experiment, to obtain one absolute pressure data point and 48 differential pressure data points, only one valve in each pressure control valve group was open during each reading. Due to the close distance between the rotary solenoid valve disc and the pressure sensor, the data stabilization time is short. After the pressure data stabilizes, the pressure control valves are closed. The Adam 4056 module controls the pressure control valves in each control valve to open, read, and then close sequentially, reading the pressure data for each channel in turn.

[0061] The core of the rotary pressure switching system is its coordination with the hardware system to achieve rapid scanning of multiple pressure channels through control. Due to the presence of the pressure tapping tube, the scanning frequency of the pressure scanning system decreases. To improve pressure scanning speed, accurate judgment of pressure stability and rapid switching are crucial. For the pressure signal at the measuring point, the pressure tapping tube acts as a filter, filtering out high-frequency signals. When using the pressure tapping tube, its dynamic response is first obtained based on its geometric parameters (length, diameter). By analyzing the amplitude-frequency characteristics of the pressure tapping system, the system's natural frequency and operating frequency band are determined, allowing low-frequency signals at the measuring point to be monitored. Furthermore, since a step signal is generated when switching gas paths, the system's response time to this step signal is a crucial factor in controlling the pressure control valve's gas path switching and improving scanning speed.

[0062] The system's amplitude-frequency response is used in the following way:

[0063] The pressure tap and pressure sensor constitute a pressure testing system, whose dynamic mathematical model is theoretically a distributed parameter model. This distributed parameter model can be equivalently viewed as a single-degree-of-freedom second-order system with lumped parameters.

[0064] Equivalent gas volume of the cavity:

[0065] Equivalent gas sensation of the pressure tap:

[0066] Equivalent air resistance of the pressure tapping tube:

[0067] Where: r is the radius of the pressure tube; l is the length of the pressure tube; V is the volume of the sensor's own cavity; ρ is the density of the gas; η is the dynamic viscosity of the gas; and v is the speed of sound in the gas.

[0068] The system's natural frequency is:

[0069]

[0070] The volume of the pressure sensor cavity in this experiment is much smaller than the volume of the pressure tapping tube. Therefore, the equivalent gas volume of the cavity can be ignored. Thus, the natural frequency of the system can be expressed using the 1 / 4 wavelength formula:

[0071]

[0072] If p0(t) represents the pressure at the inlet of the pressure tap and p(t) represents the pressure inside the sensor cavity, then the amplitude-frequency characteristic of the above system is:

[0073]

[0074] in:

[0075] By utilizing the amplitude-frequency characteristics of the system, the system's inherent frequency and operating frequency band can be determined, enabling the monitoring of low-frequency signals at the measurement points.

[0076] When the system switches gas paths, the system's step response can be expressed as:

[0077]

[0078] Where τ is dimensionless time:

[0079]

[0080] Where τ0 is the dimensionless delay time:

[0081]

[0082] Where T is the ratio of the pressure tap length to the speed of sound:

[0083]

[0084] After determining the parameters of the length and diameter of the pressure tapping tube by calculating the dynamic response of the system, the step response time of the pressure tapping system is calculated to achieve rapid scanning of the pressure tapping system.

[0085] Pressure signal dynamic-to-static conversion system, such as Figure 3 As shown, the system pressure signal is acquired at the rotating end and read by a sensor at the stationary end. The scanning control signal for the pressure control valve is input from the stationary end, controlling the pressure control valve at the rotating end to scan the pressure. The pressure signal conversion system is the key component for converting the pressure signal from the rotating end to the stationary end. In this system, the slip ring transmits the electrical signal, and the pressure signal conversion connector transmits the pressure signal. The customized pressure signal conversion connector in this system uses a stainless steel frame and a PTFE bracket for end face sealing, employing a fully sealed structure to significantly reduce air leakage at the rotary joint. The shaft uses a ceramic coating process, making it high-speed and wear-resistant. Compared with traditional non-fully sealed rotary joints, this significantly reduces pressure loss at the joint. The pressure control signal is introduced from the stationary end through the slip ring, controlling the on / off state of the pressure control valve.

[0086] The rotary automatic calibration system is an important component of the rotary pressure measurement system. The system can obtain precise pressure at the measurement points and measure minute pressure leaks within the system. The automatic calibration system consists of two parts: a correction algorithm for the measurement point pressure and a calibration of the pressure loss in the test system.

[0087] The pressure correction algorithm at the measuring points is fundamental to accurate pressure measurement at high speeds. The pressure measurement scheme used in this paper introduces pressure into the shaft center for measurement. Since the pressure is varied due to the radially arranged pressure taps, calculating the actual pressure between the measuring points from the pressure obtained from the sensor is crucial. In the pressure tests conducted by Qiu Lu, Cheng Junhua, and others, the pressure in the pressure taps was simply calculated using... A correction is made that ignores the density inside the pressure tube. This correction has a small error at low speeds, but at higher speeds, the effect of this density change can have a significant impact on the test results.

[0088] Therefore, this system derives and evaluates the pressure distribution within the high-speed pressure tapping tube. An equation for the rotational pressure correction, considering density variations within the pressure tapping tube, is obtained.

[0089]

[0090] Where P(x) is the pressure at the measuring point with radius x; P0 is the pressure introduced into the shaft at the measuring point, which is also the reading of the differential pressure sensor (12); Ω is the rotational speed, in rad / s; R is the gas constant, with a value of 287.06 J / (Kg·K); and T is the gas temperature in the pressure tapping tube.

[0091] When x1 = 0.2m and x2 = 0.4m, and the rotational speed is less than 500 rpm, the error caused by the third term results in a pressure error of approximately 1 Pa under experimental pressure, which can be ignored. However, when the rotational speed increases to 3000 rpm, the pressure gradient in the pressure tapping tube increases rapidly due to the increased rotational speed. The error in the pressure difference between the two points caused by the calculation method increases to 2000 Pa. At this point, the error is on the same order of magnitude as the pressure difference between the two points caused by flow resistance. Therefore, at high rotational speeds, the pressure error generated in the radial pressure tapping tube must be accurately corrected.

[0092] The pressure loss of the testing system also needs to be calibrated. Using stationary end pressure measurement, the micro-pressure leakage at the dynamic-static transition joint is easier to correct than the reading error caused by the rotation of the pressure sensor. Calibration of the dynamic-static transition joint leakage can be performed at different speeds. Using pressure control valve group switching, the error caused by the system's micro-pressure leakage in each flow path can be accurately obtained, thus allowing for pressure correction during the experiment.

[0093] This system features a customized 8-channel high-speed pressure signal dynamic-to-static conversion connector. The connector uses a PTFE friction seal with a stainless steel frame, significantly reducing micro-pressure leakage at the connector. Furthermore, considering that the diameter of the rotary joint should not be too large, the number of channels was chosen to be 8.

[0094] Rotary pressure calibration is crucial for pressure measurement. This experimental system is a real-time pressure calibration system, which can calibrate the effect of micro-pressure leakage at the joint after the pressure measurement is completed. As shown in the experimental system diagram, during the experiment, the inlet and outlet flow control valves maintain a certain opening to control the flow and pressure within the experimental specimen. When the experiment at one rotation speed ends, the system automatically switches to calibration mode. The flow control valves at outlet 2 and inlet 1 are calibrated sequentially. The outlet valve is jogged to release air, ensuring the pressure in the channel remains consistent with the experimental pressure. At this point, there is no gas flow in the channel, and the pressure in the channel remains consistent with the experimental pressure. The pressure control valve is then used to sequentially read the differential pressure reading when no air is supplied. The difference between the experimental reading and the differential pressure reading under the calibration system is used to obtain the actual differential pressure between the two points.

[0095] This invention also discloses a multi-channel pressure acquisition and calibration method suitable for high-speed rotating equipment, including the aforementioned multi-channel pressure acquisition and calibration system suitable for high-speed rotating test benches, characterized in that the calibration method includes the following steps:

[0096] Step 1: During the experiment, the flow regulating valves at the inlet and outlet of the rotary multi-channel pressure acquisition and calibration system experimental platform are kept at a certain opening to control the flow and pressure in the experimental specimen; before the rotary flow resistance characteristic test experiment begins, the system first enters the calibration mode.

[0097] Step 2: Adjust the pressure inside the test piece (6) to match the experimental state. When stationary, close the flow control valve (3) and the flow control valve (2) in sequence; adjust the opening of the flow control valve (3) to 1% to slowly release the gas, so that the pressure inside the test piece (6) remains consistent with the experimental state; at this time, there is no gas flow in the channel, and the pressure in the channel is also consistent with the experimental state;

[0098] Step 3: Perform micro-pressure leakage calibration on each pressure measuring pipeline. The rotating solenoid valve disc (8) is equipped with 48 pressure control valves. Switch the pressure control valves (9) in sequence and read the differential pressure reading when the differential pressure sensor (12) is not venting. The reading at this time is the micro-pressure leakage value of the system when it is stationary.

[0099] Step 4: Start the high-speed rotating test bench with the motor and repeat the above steps at different speeds. Record the micro-pressure leakage value when each pressure control valve (9) of the system is opened within the experimental speed range, and form a micro-pressure leakage error table for all measuring points at different speeds. The micro-pressure leakage error table serves as the benchmark for testing.

[0100] Step 5: During the rotation experiment, according to the experimental requirements, the pressure at each point in the experimental piece under different inlet Reynolds numbers and different rotation speeds is scanned in sequence, and the differential pressure sensor (12) records the pressure reading at each measuring point; combined with the micro-pressure leakage error table, the values ​​are corrected to obtain the corrected pressure distribution at each point in the experimental piece.

[0101] Step 6: Using the pressure correction theory derived mathematically, the actual pressure at the measuring point is derived from the sensor reading; due to the centrifugal pressure gradient generated in the pressure tube by the centrifugal force of rotation, there is a difference between the reading of the pressure at the axis, i.e., the differential pressure sensor (12), and the reading at the measuring point position inside the experimental piece.

[0102] This section presents a method for deriving the readings of the measuring points inside the experimental specimen from the readings of the differential pressure sensor (12).

[0103]

[0104] Where P(x) is the pressure at the measuring point with radius x; P0 is the pressure introduced into the shaft at the measuring point, which is also the reading of the differential pressure sensor (12); Ω is the rotational speed, in rad / s; R is the gas constant, with a value of 287.06 J / (Kg·K); and T is the gas temperature in the pressure tapping tube.

[0105] The mathematical derivation of the correction method for rotational pressure is as follows:

[0106] In the experiment, a pressure-induction scheme was used to introduce pressure into the shaft center for measurement. Therefore, the pressure was first converted to the measuring point position. The static pressure P(x) at the position with a radius of rotation x can be expressed as:

[0107]

[0108] Where P0 is the pressure at the axial position, which is the measured value of the pressure sensor; ρ(r) is the gas density in the pressure tube with radius r; and Ω is the rotational speed of the experimental system, in rad / s.

[0109] Convert ρ(r), and assume the default temperature inside the pressure tap is constant:

[0110]

[0111]

[0112] Where P is the rational gas state constant, R is the gas constant, R = 287.06 J / (Kg·K); T is the gas temperature inside the pressure tapping tube;

[0113] Differentiate both sides of the equation:

[0114]

[0115]

[0116] The above equation is a first-order homogeneous ordinary differential equation, and its general solution can be expressed as:

[0117]

[0118] Solve for the general solution:

[0119]

[0120]

[0121] At the axial position: P(0) = P0, where P0 is the experimental test value.

[0122] therefore:

[0123]

[0124] Expressed in polynomial form using Taylor expansion:

[0125]

[0126] After neglecting higher-order minor quantities, the pressure at the measuring point with radius r1 can be expressed as the pressure measured at the axis center as follows:

[0127]

[0128] The second term represents the pressure difference caused by the pressure tapping tube when density changes within the tube are not considered. When x1 = 0.2m, x2 = 0.4m, and the rotation speed is less than 500 rpm, the pressure error caused by the third term under experimental pressure is approximately 1 Pa, which can be ignored. However, when the rotation speed increases to 3000 rpm, the pressure gradient in the pressure tapping tube increases rapidly due to the increased rotation speed. The error in the pressure difference between the two points caused by the calculation method increases to 2000 Pa. At this point, the error is on the same order of magnitude as the pressure difference between the two points caused by flow resistance. Therefore, at high rotation speeds, the pressure error generated within the radial pressure tapping tube must be accurately corrected.

[0129] A multi-channel pressure acquisition and calibration system for high-speed rotational experiments on turbomachinery.

[0130] 1. Solved the problem of rapid testing of multiple pressures on a high-speed rotating test bench.

[0131] This invention constructs a pressure scanning system at the rotating end of a high-speed experimental platform, while placing the sensor at the stationary end, thereby reducing the impact of rotation. To address the challenge of acquiring multiple pressure signals from rotating components on a high-speed rotating experimental platform, a rotating module integrating a pressure control valve group is installed at the rotating end. A group of 48 reliable miniature pressure control valves is used to control the on / off state of the pressure lines at high speeds. By grouping the pressure control valves and controlling the number of valves in each group, rapid scanning of each pressure line is achieved within a short time, significantly improving the pressure measurement capability of rotating pressure testing. With the help of the control system, combined with the diameter and length of the pressure taps for different experiments, the stabilization time is quickly determined, accelerating the scanning frequency.

[0132] 2. The pressure error caused by the pressure tapping tube of the high-speed test bench has been corrected.

[0133] The pressure measurement scheme used in this paper introduces pressure into the shaft for measurement. Since the pressure is varied due to the radially arranged pressure taps, calculating the actual pressure between the measurement points from the pressure measured by the sensor is crucial. Previous rotational pressure tests simply used the pressure in the pressure taps... A correction was made that ignored the density inside the pressure tapping tube. This correction resulted in a small error at low speeds, but at higher speeds, the effect of density changes significantly impacted the test results. This system, by deriving the pressure distribution inside the pressure tapping tube, obtained an accurate numerical solution for obtaining the pressure at the measuring point from the measured pressure, greatly correcting the measurement error of the pressure tapping tube at high speeds.

[0134] 3. Real-time calibration of multi-channel pressure loss on the high-speed rotating test bench was achieved.

[0135] By employing stationary end pressure measurement, the micro-pressure leakage at the dynamic-static transition joint is easier to correct than the reading error caused by the rotation of the pressure sensor. This allows for calibration of the dynamic-static transition joint leakage at different speeds. Using a pressure-controlled valve group switching method, the error caused by micro-pressure leakage in each flow path can be accurately obtained, enabling pressure correction during experiments.

[0136] This invention focuses on the precise measurement of pressure in rotating components of turbomachinery. It presents a multi-channel pressure acquisition and calibration system suitable for high-speed rotating test benches, solving the long-standing problems of difficult pressure testing at high speeds, limited test quantity, and inaccurate measurements. It achieves precise rotating pressure testing of up to 49 pressure channels at speeds exceeding 4000 rpm, and utilizes a control program to quickly determine stabilization time, improving pressure scanning speed. Addressing the lack of theoretical correction for pressure at high speeds, a theoretical derivation method is used to correct the pressure within the pressure tapping tube at high speeds. To address the micro-pressure leakage error present in the system, a rotating pressure calibration system is developed to further improve the accuracy of rotating pressure testing.

[0137] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A multi-channel pressure acquisition and calibration system suitable for high-speed rotating equipment, including a rotation pressure switching system, a pressure signal dynamic-to-static conversion system, and a rotation automatic calibration system, characterized by: The rotary pressure switching system: Through a pressure scanning system and control device composed of multi-way pressure control valves, it enables rapid measurement of multiple pressure measurement points on a high-speed test bench, and obtains accurate pressure along the test piece for rotary flow resistance characteristic testing of the measurement points. The pressure signal dynamic-to-static conversion system: uses a slip ring and a pressure signal dynamic-to-static conversion joint to convert the pressure signal along the test piece tested by the rotating test bench and the control electrical signal of the pressure control valve from the rotating end to the stationary end of the test system, thereby realizing the signal transmission between the stationary end and the rotating end of the test system. The rotary automatic calibration system detects the pressure signals of the multi-pressure connectors in the rotary test bench and determines whether there is micro-pressure leakage at the dynamic-static conversion connector, thereby calibrating the multi-pressure connectors. The rotary pressure switching system further includes the following: 1) Construct a pressure scanning system at the rotating end and place the sensor at the stationary end; 2) The pressure measuring point of the test piece on the rotating disk is connected to the pressure control valve. The pressure control valve controls the opening and closing of the pressure air path. The pressure control valve group is grouped to ensure that each group of pressure control valves has only one path in the passage at the same time. After stabilization, the next path is quickly switched to the passage. 3) A rotating module integrating pressure control valve group is set at the rotating end, and a multi-way miniature pressure control valve is selected to realize the opening and closing of the pressure pipeline at high speed; the experimental platform is equipped with two solenoid valve discs to provide the ability to switch multiple pressure measurement points. 4) Pressure testing using a differential pressure sensor: Using the inlet pressure P0 of the test piece as a reference, the absolute pressure transmitter measures the absolute pressure at the inlet of the channel, and the differential pressure sensor measures the pressure difference between any point in the channel and the inlet measuring point; multiple pressure control valve groups are set in the rotary solenoid valve disc, each pressure control valve group contains multiple pressure control valves, and each group corresponds to one rotary joint; the signal is introduced to the rotary end through the slip ring, and the on / off state of the pressure control valve is controlled by Adam 4056SO; 5) After the pressure data stabilizes, close the pressure control valve; the Adam 4056SO module controls the pressure control valve in each control valve group to open and close sequentially after reading the data, reading the pressure data of each channel in turn.

2. The multi-channel pressure acquisition and calibration system for high-speed rotating equipment according to claim 1, characterized in that: The pressure tap and pressure sensor together constitute a pressure testing system, whose dynamic mathematical model is theoretically a distributed parameter model. Equivalent gas volume of the cavity: ; Equivalent gas sensation of the pressure tap: ; Equivalent air resistance of the pressure tapping tube: ; Where: r is the radius of the pressure-sensing tube; l is the length of the pressure-sensing tube; V is the volume of the sensor's own cavity; ρ is the density of the gas; η is the dynamic viscosity of the gas; v is the speed of sound in the gas; If p0(t) represents the pressure at the inlet of the pressure tap and p(t) represents the pressure inside the sensor cavity, then the amplitude-frequency characteristic of the above system is: in: The system's natural frequency is: The volume of the pressure sensor cavity in this experiment is much smaller than the volume of the pressure tapping tube; therefore, the equivalent gas volume of the cavity is negligible. The natural frequency of the system is set using the 1 / 4 wavelength formula: When the system switches gas paths, the system's step response is expressed as: in For dimensionless time: in For dimensionless delay time: Where T is the ratio of the pressure tap length to the speed of sound: Once the parameters of the length and diameter of the pressure tapping tube are determined by the dynamic response, the step response time of the pressure tapping system is calculated to achieve rapid scanning of the pressure tapping system.

3. The multi-channel pressure acquisition and calibration system for high-speed rotating equipment according to claim 1, characterized in that: The pressure signal dynamic-to-static conversion system includes the following components: It includes a slip ring and a pressure signal dynamic-static conversion connector. The pressure signal dynamic-static conversion connector uses a stainless steel frame and a PTFE bracket for rotating end face sealing. It adopts multi-channel pressure signal conversion to achieve rapid conversion of multiple pressure signals at high speed. The slip ring is set with different channels to adapt to current signals, RS485 signals, Ethernet and USB signal conversion, so as to realize communication and control with the hardware on the rotating side. The pressure control signal and power supply are introduced from the stationary end through the slip ring to control the on and off of the pressure control valve.

4. The multi-channel pressure acquisition and calibration system for high-speed rotating equipment according to claim 1, characterized in that: the automatic rotation calibration system includes the following components: This includes a system for correcting pressure reading errors caused by rotary pressure tapping, and automatic calibration of pressure signal dynamic-static conversion joints under rotational conditions for minor pressure leaks. A pressure correction method for correcting pressure reading errors caused by rotary pressure tapping is established through mathematical derivation, taking into account changes in gas density within the pressure tapping tube.

5. The multi-channel pressure acquisition and calibration system for high-speed rotating equipment according to claim 4, characterized in that: The mathematical derivation of the correction method for rotational pressure is as follows: First, the pressure is transferred to the measuring point position, and the static pressure is measured at a position with a rotation radius of x. Represented as: in, This is the pressure at the axial position, which is also the measured value of the pressure sensor; Let r be the gas density inside the pressure tap at a position with radius r; The rotational speed of the experimental system is expressed in rad / s. Will The conversion is performed, and the default temperature inside the pressure tapping tube is constant: in, R is the rational gas state constant, R = 287.06 J / (Kg∙K); T is the gas temperature inside the pressure tapping tube; Differentiate both sides of the equation: The above equation is a first-order homogeneous ordinary differential equation, and its general solution can be expressed as: Solve for the general solution: At the axis position: , These are experimental test values; therefore: Expressed in polynomial form using Taylor expansion: After ignoring higher-order minor quantities, the radius is The pressure at the measuring point can be expressed as the pressure measured at the axis: The second term is the pressure difference caused by the pressure tapping tube when density changes within the tapping tube are not considered; when , When the rotational speed is less than 500 rpm, the pressure error caused by the third item is about 1 Pa under the experimental pressure, which can be ignored. When the rotational speed increases to 3000 rpm, the pressure gradient of the pressure tapping tube increases rapidly due to the increase in rotational speed, and the pressure difference error between the two points increases to 2000 Pa. At this time, the error is on the same order of magnitude as the pressure difference between the two points due to the flow resistance. Therefore, the pressure error generated in the radial pressure tapping tube must be accurately corrected at high rotational speeds.

6. A method for multi-channel pressure acquisition and calibration of high-speed rotating equipment, comprising the multi-channel pressure acquisition and calibration system for high-speed rotating equipment as described in any one of claims 1-5, characterized in that: The calibration method includes the following steps: Step 1: During the experiment, the flow regulating valves at the inlet and outlet of the rotary multi-channel pressure acquisition and calibration system experimental platform are kept at a certain opening to control the flow and pressure in the experimental specimen; before the rotary flow resistance characteristic test experiment begins, the system first enters the calibration mode. Step 2: Adjust the pressure inside the test piece (6) to match the experimental state; while stationary, close the flow control valve (3) of the outlet channel and the flow control valve (2) of the inlet channel in sequence; adjust the opening of the flow control valve (3) of the outlet channel to 1% to slowly release the gas, so that the pressure inside the test piece (6) remains consistent with the experimental state; at this time, there is no gas flow in the channel, and the pressure in the channel is also consistent with the experimental state; Step 3: Perform micro-pressure leakage calibration on each pressure measuring pipeline; rotate the solenoid valve disc (8) which is arranged with multiple pressure control valves, switch the pressure control valves (9) in sequence, and read the differential pressure reading when the differential pressure sensor (12) is not venting. The reading at this time is the micro-pressure leakage value of the system when it is stationary; Step 4: Start the high-speed rotating test bench by motor and repeat the above steps at different speeds. Record the micro-pressure leakage value when each pressure control valve (9) of the system is opened within the experimental speed range to form a micro-pressure leakage error table at different speeds for all measuring points. This micro-pressure leakage error table serves as the reference point for the test. Step 5: During the rotation experiment, the pressure at each point in the test piece under different inlet Reynolds numbers and different rotation speeds is scanned in sequence as required. The differential pressure sensor (12) records the pressure reading at each measuring point. The value is corrected by combining the micro-pressure leakage error table to obtain the corrected pressure distribution at each point in the test piece. Step 6: Using the pressure correction theory derived mathematically, the actual pressure at the measuring point is derived from the sensor reading; due to the centrifugal pressure gradient generated in the pressure tube by the centrifugal force of rotation, there is a difference between the reading of the pressure at the axis, i.e., the differential pressure sensor (12), and the reading at the measuring point position inside the experimental piece. Method for deriving the readings of the measuring points inside the experimental piece from the readings of the differential pressure sensor (12): in The pressure at the measuring point with radius x; The pressure of the axis is introduced to the measuring point, which is the reading of the differential pressure sensor (12); R is the rotational speed in rad / s; R is the gas constant, with a value of 287.06 J / (Kg∙K); and T is the gas temperature inside the pressure tapping tube.

7. The multi-channel pressure acquisition and calibration method for high-speed rotating equipment according to claim 6 is characterized in that: the method for deriving the reading of the differential pressure sensor (12) from the reading of the measuring point inside the experimental piece is as follows: in The pressure at the measuring point with radius x; The pressure of the axis is introduced to the measuring point, which is the reading of the differential pressure sensor (12); R is the rotational speed in rad / s; R is the gas constant, with a value of 287.06 J / (Kg∙K); and T is the gas temperature inside the pressure tapping tube.

Images