A method for measuring and analyzing the distribution of an unsteady flow field at the outlet of a compressor rotor

Abstract

The application provides a compressor rotor outlet unsteady flow field distribution measurement and analysis method, comprising: arranging a movable slot extending in the circumferential direction on a compressor casing corresponding to a rotor blade outlet, so that a probe in the movable slot moves in the circumferential direction and the radial direction to perform spatial scanning on the rotor blade outlet; performing lock-in measurement, and controlling the probe to collect dynamic pressure signal data according to set acquisition parameters; and establishing a time axis and a space axis respectively according to dynamic pressure signal data obtained by a probe measuring point in a certain blade height direction of the rotor blade and corresponding circumferential space positions and measurement time sequences, and then establishing a time-space correlation axis; performing interpolation on dynamic pressure signal data on the time-space correlation axis to obtain a flow field reconstruction virtual channel, so as to obtain a change rule of dynamic pressure signal distribution of the rotor blade blade height position with time; and repeating the above steps for measuring points at different radial positions of the rotor blade to obtain a transient two-dimensional distribution of the rotor outlet flow field parameters.

Description

Technical Field

[0001] This application belongs to the field of turbomachinery testing technology, and specifically relates to a method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet. Background Technology

[0002] Inside a high-performance compressor, the compressor rotor outlet flow field exhibits strong unsteadiness and three-dimensionality due to the intense upstream and downstream interference effects between the rotor and stator blade rows, as well as the unsteady characteristics of the rotor and stator themselves. To measure the compressor rotor blade outlet flow field, current technologies typically employ contact probes. These probes allow for analysis of the distribution of aerodynamic parameters at the blade channel outlet, thereby guiding compressor blade design and optimization, which is of great significance for the design of high-performance compressor blades.

[0003] Currently, there are three main measurement methods for testing the outlet flow field of compressor rotor blades using contact probes:

[0004] 1) Airfoil probes are arranged on the stator blades downstream of the compressor rotor blades. That is, multiple total pressure or total temperature stagnation chambers are arranged along the blade height direction at the leading edge of the stator blades. The compressor rotor blades periodically sweep the downstream stator blades. The measuring point of each blade height of the airfoil probes obtains the circumferential average value of the flow field at the corresponding blade height at the compressor rotor outlet. By combining different measuring points at different blade heights, the radial distribution of total pressure or total temperature at the rotor outlet is obtained.

[0005] This testing method is relatively easy to implement and can achieve quantitative measurement of the flow field behind the rotor. However, the number of stagnation chamber probes welded to the leading edge of the stator blade is limited, the test results are very discrete along the blade height direction, and can only obtain the steady-state total pressure or total temperature results of each radial blade height circumferential average. It cannot obtain the circumferential distribution of aerodynamic parameters, nor can it obtain the direction, Mach number and static pressure results.

[0006] 2) Measurements are performed using a single-point steady-state multi-hole aerodynamic probe (typically a five-hole probe). During measurement, a probe hole 12 is drilled in the compressor outer casing 11. A displacement mechanism extends the probe 13 head to the radial blade height position behind the rotor blade 14 to be measured. The rotor blade 14 periodically sweeps the head of the steady-state probe 13, and the probe 13 measures the circumferential average of the aerodynamic parameters (total pressure, static pressure, Mach number, and airflow angle) behind the upstream rotor blade 14. By combining the test results for different radial blade heights, the radial distribution of multiple aerodynamic parameters at the rotor outlet can be obtained, such as... Figure 1 As shown;

[0007] The test scheme using a steady-state porous aerodynamic probe is advantageous because the steady-state porous aerodynamic probe is small in size and can be moved within a small spatial range along the blade height direction by a displacement mechanism, thereby obtaining relatively dense measurement parameters along the blade height direction. Its advantage is that it can quantitatively obtain the circumferential average results of multiple parameters such as total pressure, static pressure, Mach number and airflow angle along the blade height direction. However, the limitation of this method is that it cannot obtain the circumferential distribution of the rotor outlet flow field.

[0008] 3) Using a high-frequency dynamic single-hole or multi-hole aerodynamic probe, similar to using a steady-state multi-hole aerodynamic probe, a probe hole 22 is opened on the compressor casing 21 during measurement. The head of the dynamic probe 23 is inserted into the radial blade height position of the rotor blade 24 to be measured via a displacement mechanism. Based on the high frequency response and high sampling rate of the dynamic probe 23, phase-locked measurement allows the dynamic probe 23 to record the aerodynamic parameters of the rotor blade relative to the probe at different phases. The results from different phases can then be combined to obtain the circumferential aerodynamic parameter distribution at a specific blade height at the blade passage outlet. Moving the probe radially yields the circumferential distribution of the flow field at different blade heights, thus establishing the distribution of the rotor outlet flow field along both the circumferential and radial spatial dimensions. Figure 2 As shown;

[0009] While using high-frequency dynamic single-hole or multi-hole aerodynamic probes can leverage their high-frequency acquisition capabilities to obtain results from upstream rotor blades at different phases with the probe, and combine these results into a circumferential distribution of the flow field covering the entire blade outlet, the theoretical basis of this measurement method rests on the assumption that the flow field at the rotor outlet is steady in the rotor coordinate system. In reality, the flow field at the rotor blade outlet is affected by the potential effect of the downstream blades and the propagation effect of the upstream wake. The flow field differs when the rotor is at different phases, especially under off-design conditions or when the upstream wake effect is strong. Simply combining the results from different phases can introduce erroneous information into the measured flow field and may even mislead the analysis of the flow field. Summary of the Invention

[0010] The purpose of this application is to provide a method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet, so as to solve or alleviate at least one of the problems in the background art.

[0011] The technical solution of this application is: a method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet, the method comprising:

[0012] Step S1: A movable groove extending circumferentially is provided on the compressor casing corresponding to the rotor blade outlet. A probe is inserted through the movable groove to realize the movement of the probe along the circumferential and radial directions. The probe moves along the circumferential and radial directions to perform spatial scanning of the rotor blade outlet, establish the measurement point position of the probe at the rotor blade outlet, and the sampling frequency of each probe measurement point in the spatial range meets a predetermined multiple of the rotor blade passing frequency.

[0013] Step S2: Perform phase-locked loop measurement, so that the probe test system starts to control the probe to collect dynamic pressure signal data according to the set acquisition parameters based on the trigger signal;

[0014] Step S3: Based on the corresponding circumferential spatial position and measurement sequence, establish a time axis and a spatial axis for the dynamic pressure signal data obtained from the probe measurement point in the height direction of a certain rotor blade, and establish a spatiotemporal correlation axis based on the time axis and the spatial axis.

[0015] Step S4: Interpolate the dynamic pressure signal data on the spatiotemporal correlation axis to obtain a virtual channel for flow field reconstruction, thereby obtaining the variation law of dynamic pressure signal distribution at the blade height position of the rotor blade over time.

[0016] Step S5: Repeat the above steps for measuring points at different radial positions of the rotor blades to obtain the transient two-dimensional distribution of the rotor outlet flow field parameters.

[0017] Furthermore, the probe is a dynamic probe.

[0018] Furthermore, the probe has at least four measuring points in the circumferential direction.

[0019] Furthermore, the predetermined multiple is 10 to 30 times.

[0020] Furthermore, the acquisition parameters include acquisition frequency, sampling time, and number of samples.

[0021] Based on the temporal and spatial correlation of dynamic signals collected at a certain sampling frequency downstream of the compressor rotor blades during periodic sweeping, this invention combines these signals with dynamic probes and phase-locked loop (PLL) acquisition technology to form a novel method for measuring the compressor rotor outlet flow field. This method can measure the transient circumferential distribution of the compressor rotor outlet flow field and effectively distinguish the differences in the rotor outlet flow field when the rotor blades and upstream and downstream stators (including the dynamic probe) are in different phases. This method can obtain rotor outlet flow field with high spatial and temporal resolution by utilizing a limited number of measurement positions arranged circumferentially at the rotor blade outlet, effectively controlling the time consumption of dynamic probe testing, and is suitable for application in high-speed, high-risk compressor engineering tests. Attached Figure Description

[0022] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0023] Figure 1 This is a schematic diagram of the existing single-point steady-state multi-hole pneumatic probe testing method.

[0024] Figure 2 This is a schematic diagram of a high-frequency dynamic probe testing method in the prior art.

[0025] Figure 3 This is a flowchart of the method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet of this application.

[0026] Figure 4 This is a schematic diagram of the compressor rotor outlet flow field distribution measurement in this application.

[0027] Figure 5 This is a schematic diagram of the probe measurement point grid in this application.

[0028] Figure 6 This is a schematic diagram of the spatiotemporal correlation principle in this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0030] To address the problems existing in the measurement of compressor rotor outlet flow field distribution in the prior art, this application proposes a test method for the transient pressure field distribution at the compressor rotor outlet that can effectively distinguish the differences in flow field at the same location in the rotor coordinate system. Based on the fact that when the compressor rotor blades sweep across a dynamic probe arranged downstream, the dynamic probe measurement point periodically senses the dynamic signal of the flow field. By changing the position of the dynamic probe measurement point, a set of dynamic signals can be obtained. Furthermore, the signal measured at a certain moment by each probe measurement point has a strong temporal and spatial correlation with the signals at other measurement points at other moments. By establishing a spatiotemporal correlation coordinate axis from the collected data of discrete dynamic measurement points and analyzing the data on the spatiotemporal correlation coordinate axis, a signal distribution with high spatial resolution can be reconstructed based on a limited number of discrete measurement points.

[0031] like Figure 3 As shown, the method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet provided in this application includes the following steps:

[0032] Step S1: A movable groove 32 extending circumferentially is provided on the compressor casing 31 corresponding to the outlet of rotor blade 34. A probe 33 is connected via a displacement mechanism (not shown) to manipulate the probe 33 to extend into the flow channel between rotor blade 34 and downstream stator blade 35, thereby enabling the probe 33 to move circumferentially (Y) and radially (X). Figure 4 As shown.

[0033] Among them, probe 33 is a dynamic probe, which performs spatial scanning tests on the rotor blade outlet by moving the dynamic probe along the circumferential and radial directions, establishing the measurement point position of the probe at the rotor blade outlet, such as... Figure 5 As shown, the number of measuring points covering a certain range of rotor blade radial height and circumferential length is determined according to the analysis requirements. The circumferential range is generally set based on the width of the stator blade channel upstream of the rotor blade, and the number of circumferential measuring points is no less than 4.

[0034] In this application, the sampling frequency of each dynamic probe measurement point within the spatial range is 10 to 30 times the passing frequency of the rotor blades, and can be appropriately adjusted according to the capabilities of the testing system. For example, in this embodiment of the application, the number of the first stage of the compressor rotor blades under test is 40, and the rotor speed is 12000 r / min, then the sampling frequency of the dynamic probe measurement point is at least 80 kHz.

[0035] Step S2: Conduct phase-locked measurement. That is, when the rotor blade 34 rotates once, the dynamic probe test system starts to control the dynamic probe to collect dynamic pressure signal data according to the set acquisition parameters (including acquisition frequency, sampling time, sampling quantity, etc.) based on the trigger signal.

[0036] Step S3: Based on the dynamic pressure signal data obtained from the dynamic probe 33 measuring point in the height direction of a certain rotor blade, establish a time axis X and a spatial axis T according to their corresponding circumferential spatial position and measurement sequence. Establish a spatiotemporal correlation axis XT based on the time axis X and spatial axis T. The slope of the spatiotemporal correlation axis XT is set according to the time it takes for the measured rotor blade to sweep across the upstream stator blade. Figure 6 As shown;

[0037] Step S4: Interpolate the dynamic pressure signal data on the spatiotemporal correlation axis XT to obtain the flow field reconstruction virtual channel VC. Based on the flow field reconstruction virtual channel VC, obtain the variation law of the dynamic pressure signal distribution at the rotor blade height position over time.

[0038] Step S5: Repeat the above steps for measuring points at different radial positions of the rotor blades to obtain the transient two-dimensional (circumferential and radial) distribution of the rotor outlet flow field parameters.

[0039] Based on the temporal and spatial correlation of dynamic signals collected at a certain sampling frequency downstream of the compressor rotor blades during periodic sweeping, this invention combines these signals with dynamic probes and phase-locked loop (PLL) acquisition technology to form a novel method for measuring the compressor rotor outlet flow field. This method can measure the transient circumferential distribution of the compressor rotor outlet flow field and effectively distinguish the differences in the rotor outlet flow field when the rotor blades and upstream and downstream stators (including the dynamic probe) are in different phases. This method can obtain rotor outlet flow field with high spatial and temporal resolution by utilizing a limited number of measurement positions arranged circumferentially at the rotor blade outlet, effectively controlling the time consumption of dynamic probe testing, and is suitable for application in high-speed, high-risk compressor engineering tests.

[0040] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet, characterized in that, The method includes: Step S1: A movable groove extending circumferentially is provided on the compressor casing corresponding to the rotor blade outlet. A probe is inserted through the movable groove to realize the movement of the probe along the circumferential and radial directions. The probe moves along the circumferential and radial directions to perform spatial scanning of the rotor blade outlet, establishing the measurement point position of the probe at the rotor blade outlet. The sampling frequency of each probe measurement point within the spatial range meets 10 to 30 times the rotor blade passing frequency. The probe is a dynamic probe, and the probe has no less than 4 measurement points in the circumferential direction. Step S2: Perform phase-locked loop measurement, so that the probe test system starts to control the probe to collect dynamic pressure signal data according to the set acquisition parameters based on the trigger signal; Step S3: Based on the corresponding circumferential spatial position and measurement sequence, establish a time axis and a spatial axis for the dynamic pressure signal data obtained from the probe measurement point in the height direction of a certain rotor blade, and establish a spatiotemporal correlation axis based on the time axis and the spatial axis. Step S4: Interpolate the dynamic pressure signal data on the spatiotemporal correlation axis to obtain a virtual channel for flow field reconstruction, thereby obtaining the variation law of dynamic pressure signal distribution at the blade height position of the rotor blade over time. Step S5: Repeat the above steps for measuring points at different radial positions of the rotor blades to obtain the unsteady two-dimensional distribution of the rotor outlet flow field parameters.

2. The method for measuring and analyzing the unsteady flow field distribution at the compressor rotor outlet as described in claim 1, characterized in that, The acquisition parameters include acquisition frequency, sampling time, and number of samples.

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