Synchronous dynamic measurement method for surface boundary layer and interstage flow field of aero-engine rotor blade

Abstract

The invention discloses a synchronous dynamic measurement method for a surface boundary layer and an interstage flow field of an aero-engine rotor blade, and belongs to the technical field of mechanical testing of aero-engine / gas turbine impellers. According to the method, fluid-solid coupling numerical simulation is carried out on a to-be-tested rotor system under a given rotating speed and a given working condition, and arrangement positions and installation postures of a surface hot film, a hot wire probe or a dynamic probe and a strain gauge are determined; a synchronous measurement system composed of a surface hot film measurement channel, a hot wire / dynamic probe measurement channel, a strain gauge measurement channel, a synchronous phase locking device, a high-fidelity slip ring and a multi-channel data acquisition system is constructed; and synchronous dynamic measurement and conjoint analysis of a blade surface boundary layer, an interstage flow field and a blade vibration signal are realized. According to the method, high-precision three-field coupling data can be obtained, and a reliable basis is provided for fluid-structure interaction mechanism research and aeroelasticity and fatigue life design of a high-load aero-engine.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine / gas turbine turbomachinery testing technology, and relates to a synchronous dynamic measurement method for the boundary layer and interstage flow field on the surface of aero-engine rotor blades. Specifically, it relates to a non-steady-state synchronous measurement method that combines surface hot film technology, hot wire probe or dynamic probe technology and strain gauge technology to achieve transient flow characteristics and rotor blade vibration characteristics of aero-engines. Background Technology

[0002] The internal flow of aero-engines exhibits significant unsteady characteristics, with the flow and vibration characteristics in the rotor blade region being particularly complex. The boundary layer flow field involves multi-scale physical processes such as transition, separation, and reattachment. Its vibration characteristics at high speeds exhibit multi-mode coupling and traveling wave vibrations. Furthermore, the flow field between the turbine and compressor stages displays strong unsteadiness due to the combined effects of dynamic and static interference, potential flow disturbance, and wake mixing. Meanwhile, for aero-engine rotors, high-load design has become an inevitable trend to improve efficiency and thrust-to-weight ratio. However, this significantly exacerbates the adverse pressure gradient, leading to large-scale boundary layer separation on the blade suction surface, forming separation bubbles or even open separation, significantly increasing flow losses and deteriorating engine performance.

[0003] Furthermore, rotor blades operate in an extreme environment characterized by high speeds and unsteady aerodynamic forces, making them highly susceptible to high-cycle fatigue and potentially triggering catastrophic resonance or flutter. More critically, a strong bidirectional coupling exists between blade vibration and boundary layer characteristics: blade vibration alters the local angle of attack and tip clearance in real time, distorting the three-dimensional flow field structure and inducing or exacerbating corner separation, endwall boundary layer separation, and tip leakage vortices; while the dynamic pressure pulsations generated by the unsteady boundary layer separation react on the blade surface, creating strong additional aerodynamic excitation forces, thereby altering the blade's aerodynamic damping characteristics, affecting vibration modes, and even inducing aeroelastic instability. During engine operation, the periodic rotation of the rotor and the complex unsteady interference between stages further intensify the complex interaction between flow and blade vibration through various pathways such as potential flow fields, wakes, and shock waves. Therefore, a deep understanding of the interaction mechanism among rotor blade boundary layer characteristics, interstage flow field characteristics, and blade vibration characteristics is crucial for overcoming aerodynamic and structural design bottlenecks and achieving high engine performance and reliability. One of the key issues in solving this problem is how to simultaneously acquire high-precision experimental data on the unsteady flow characteristics, unsteady vibration characteristics, and unsteady interstage flow field characteristics of the blade boundary layer under the same operating conditions.

[0004] Currently, unsteady characteristics inside aero-engines are mainly obtained through two methods: numerical calculation and experimental measurement. Flow characteristic calculations primarily rely on CFD (Computational Fluid Dynamics). However, due to the characteristics of aero-engine flow, which involves abrupt transitions, strong shear, and large separation, the accuracy of CFD calculations is often low. Vibration characteristic analysis mainly relies on finite element simulation, but its discrete nature also limits its ability to characterize the stress characteristics of complex structures. Current simulation software typically supports fluid-structure interaction (FSI) calculations, but due to the inherent limitations of CFD and finite element simulations, it is usually difficult to accurately obtain flow field and blade vibration information through FSI simulations.

[0005] In experimental measurement, the most commonly used method for measuring the boundary layer of high-load rotor blades is surface thermal film technology. The measurement principle of surface thermal film technology is based on the convective heat transfer effect: a micron-sized metal thin-film sensor is fixed to the blade surface and heated by electricity. Its heat dissipation rate varies with the local flow velocity, leading to changes in the sensor's resistance and the voltage signal obtained by the hot-wire anemometer. By monitoring this electrical signal, key parameters of boundary layer flow, such as wall shear stress, can be derived, exhibiting extremely high temporal and spatial resolution. However, thermal film elements are highly sensitive to temperature and are difficult to operate stably and persistently in the high-speed, high-temperature environment of aero-engines. Furthermore, as a contact measurement method, the application of thermal film can have a certain impact on the blade boundary layer, and this impact should be minimized during experiments.

[0006] The interstage flow field of an aero-engine can be measured using a two-dimensional hot-wire probe. When heated by electricity, the heat dissipation rate of two miniature hot wires at the tip of the probe changes with the magnitude and direction of the airflow velocity. This change directly reflects the change in the voltage required to maintain the constant temperature of the hot wires. By measuring the voltage signals on these two hot wires and combining this with precise pre-calibration, the two-dimensional velocity vector in the plane can be simultaneously analyzed, thus obtaining the velocity field between the aero-engine stages. The hot-wire probe has an extremely high frequency response, enabling it to accurately capture the unsteady flow structure between aero-engine stages. However, the two-dimensional hot-wire probe is extremely sensitive to airflow direction, requiring frequent angle adjustments during actual measurements.

[0007] The interstage flow field of aero-engines can also be measured using a dynamic probe. The miniature high-frequency pressure sensor integrated at the tip of the dynamic pressure probe, based on the piezoresistive or capacitive effect, can directly convert the sensed unsteady pressure pulsations into electrical signals. By measuring this time-varying pressure signal and combining it with the probe's aerodynamic calibration data, the dynamic pressure distribution and pulsation characteristics in the flow field can be analyzed, thereby obtaining the energy spectrum structure and pressure fluctuation characteristics of the unsteady interstage flow. The dynamic pressure probe possesses excellent mechanical strength and environmental adaptability, enabling it to operate stably in harsh environments with specific high temperatures and high flow rates, and accurately capturing transient phenomena such as shock wave oscillations and vortex structure evolution induced by rotor-stator interference. However, similar to two-dimensional hot-wire probes, the dynamic probe is also extremely sensitive to airflow direction, requiring frequent angle adjustments during actual measurements.

[0008] Currently, strain gauge measurement technology is mainly used to measure the vibration characteristics of blades. The principle of strain gauge measurement of blade vibration is to use a miniature resistive grid attached to the blade surface to sense deformation, which is then converted into an electrical signal by a dynamic strain gauge. Strain gauge measurement technology has the characteristics of high frequency response and high local spatial resolution, which can directly obtain the dynamic strain of the structural surface, and then indirectly obtain the vibration stress through calculation.

[0009] Theoretically, coupling the aforementioned measurement techniques can achieve the measurement of rotor blade vibration, blade boundary layer, and interstage flow field in aero-engines. However, these measurements are often asynchronous in time, and may even be performed on different test specimens or test benches. It is difficult to obtain mutually coupled unsteady data under the same operating conditions and time reference. Furthermore, when performing multi-cycle flow field measurements, all four techniques suffer from high signal-to-noise ratio and dynamic detail distortion. There is a lack of effective means to strictly correlate the measurement data with the rotor's rotational phase, thus making it difficult to reflect the dynamic evolution of the flow field with the rotor phase. Therefore, under the background of complex flow and vibration coupling in high-load aero-engines, how to achieve multi-parameter, high-precision, simultaneous, and synchronous dynamic measurement of rotor blade surface boundary layer, interstage flow field, and blade vibration characteristics under the premise of engineering feasibility remains an urgent problem to be solved. Summary of the Invention

[0010] (a) Purpose of the invention To address the aforementioned deficiencies and shortcomings of existing technologies, this invention aims to provide a synchronous dynamic measurement method for the surface boundary layer and interstage flow field of aero-engine rotor blades. Based on fluid-structure interaction numerical simulation results, the arrangement and configuration of the surface hot film, hot-wire probe or dynamic probe, and strain gauges are determined. The method utilizes the surface hot film, a synchronous phase-locked loop (PLL) device, and slip rings to measure the flow characteristics of the aero-engine rotor boundary layer; the hot-wire probe (or dynamic probe) and PLL device to measure the interstage velocity field; and strain gauges, PLL device, and slip rings to measure the blade vibration characteristics. By employing a unified PLL trigger signal and a high-precision clock source, all measurement channels are ensured to be synchronously triggered and acquire data based on the same time reference. Ultimately, this achieves spatiotemporal synchronous dynamic measurement of the rotor blade boundary layer flow field, interstage flow field, and blade vibration characteristics across multiple physical parameters, providing reliable experimental support for the study of fluid-structure interaction mechanisms and structural safety assessments of high-load engines.

[0011] (II) Technical Solution To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution: A method for synchronous dynamic measurement of the boundary layer and interstage flow field on the surface of an aero-engine rotor blade is provided to simultaneously acquire the unsteady flow characteristics of the boundary layer on the surface of the aero-engine rotor blade, the unsteady characteristics of the interstage flow field, and the unsteady vibration characteristics of the rotor blade. The method includes the following implementation steps: S100. Fluid-structure interaction numerical simulation: Perform fluid-structure interaction numerical simulation on the rotor system of the aero-engine under test under a given rotational speed to obtain the prominent locations of unsteady vibration of rotor blades, significant locations of unsteady separation and reattachment of surface boundary layer, and airflow direction at the locations of the interstage flow field to be measured. S200. Test measurement device arrangement: Strain gauges are placed at the prominent positions of unsteady vibration of rotor blades, and surface thermal film is placed at the prominent positions of unsteady separation of the boundary layer on the surface of rotor blades; hot wire probes or dynamic probes are set in the interstage channel, so that the hot wire plane is perpendicular to the local incoming flow direction or the hole of the dynamic probe is directly facing the incoming flow direction. S300. Construction of Synchronous Phase-Locked Measurement System: A synchronous phase-locked device including a phase-locked trigger and a phase-locked amplifier is set up, and the surface hot film, strain gauge, and hot wire probe or dynamic probe are communicatively connected to the synchronous phase-locked device. A unified reference signal and trigger signal are generated by the phase-locked trigger and transmitted to each measurement device respectively. Each measurement channel completes phase-locked amplification and signal conditioning based on the same reference signal in the phase-locked amplifier. S400. Multi-channel synchronous data acquisition: Using a multi-channel data acquisition system, under the unified time and phase reference provided by the synchronous phase-locked device, the phase-locked output signals of each measurement channel are synchronously acquired and stored, so that each measured physical quantity has a one-to-one correspondence under the unified time reference and phase period; S500. Engine Rotor Coupling Characteristics Analysis: Based on synchronously acquired data, the measurement data are processed and analyzed under a unified time and phase reference to obtain the flow characteristics of the blade surface boundary layer, the interstage flow field characteristics, and the rotor blade vibration characteristics, thereby realizing the synchronous dynamic measurement of the surface boundary layer and interstage flow field of the aero-engine rotor blade.

[0012] (III) Technical Effects Compared with the prior art, the synchronous dynamic measurement method of the boundary layer and interstage flow field on the surface of aero-engine rotor blades of the present invention has the following beneficial and significant technical effects: (1) Based on fluid-structure interaction numerical simulation, this invention determines the location of the hot film on the surface for measuring the blade boundary layer, the location and method of the hot wire probe or dynamic probe for measuring the interstage velocity field, and the location of the strain gauge for measuring the blade vibration characteristics. This can effectively reduce the wear and tear on the measuring instruments caused by frequent adjustments, reduce the impact of improper installation or laying of the measuring instruments on the flow field, and enable more accurate measurement of the flow field and blade vibration characteristics.

[0013] (2) This invention achieves spatial synchronous measurement of the boundary layer flow field, interstage flow field, and rotor blade vibration of aero-engine rotors through a technique of simultaneous measurement using a surface hot film, a hot wire probe (or a dynamic probe), and strain gauges. By setting the same reference signal during the phase-locked amplification process of the hot film measurement signal, the hot wire measurement signal, and the strain gauge measurement signal, and by using a shared clock and common triggering method during the acquisition of the three measurement signals, simultaneous and synchronous dynamic measurement of the three measurement signals is achieved. This enables synchronous dynamic measurement of the boundary layer flow field, rotor blade vibration, and interstage flow field of aero-engine rotors in both space and time. High-fidelity transmission of the hot film measurement signal and the strain gauge measurement signal is achieved through a slip ring. This method is of great significance for analyzing the unsteady flow characteristics, including the rotor blade boundary layer and interstage flow fields, the semi-steady vibration characteristics of rotor blades, and the interaction between them.

[0014] (3) This invention combines fluid-structure interaction-guided measurement point layout with three-field synchronous dynamic measurement to construct a high spatiotemporal resolution experimental data system covering the blade surface boundary layer, interstage channel flow field and blade vibration response. It can provide reliable benchmark data for the verification and correction of CFD and fluid-structure interaction numerical models, and provide experimental support for the aeroelastic stability design, vibration fatigue life assessment and safety margin analysis of high-load aero-engine blades, thereby improving the overall operational reliability and engineering application value of the engine. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The diagram shown is an architecture diagram of the synchronous dynamic measurement method for the boundary layer and interstage flow field on the surface of aero-engine rotor blades provided in an embodiment of the present invention. Figure 2 The diagram shown is a flowchart of the synchronous dynamic measurement process of the boundary layer and interstage flow field on the surface of an aero-engine rotor blade, provided in an embodiment of the present invention. Detailed Implementation

[0017] This invention aims to provide a method for synchronous dynamic measurement of the boundary layer and interstage flow field on the surface of aero-engine rotor blades. To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, embodiments of this invention, and are exemplary and intended to explain the invention, not to limit it. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0018] like Figure 1 and Figure 2 As shown in the embodiment of the present invention, the method for synchronous dynamic measurement of the boundary layer and interstage flow field on the surface of an aero-engine rotor blade is used to simultaneously acquire the flow characteristics of the boundary layer on the surface of the aero-engine rotor blade, the flow field characteristics between stages, and the vibration characteristics of the rotor blade. The method includes the following implementation steps: S100. Numerical simulation of fluid-structure interaction: Under a given operating speed, a fluid-structure interaction numerical simulation is performed on the rotor system of the aero-engine under test to obtain the prominent locations of unsteady vibration of the rotor blades, the significant locations of unsteady separation and reattachment of the surface boundary layer, and the airflow direction at the measured locations of the interstage flow field. Based on the results of the fluid-structure interaction numerical simulation, this invention determines the arrangement positions and methods of the surface hot film, hot wire probe, dynamic probe, and strain gauge. The boundary layer flow characteristics of the aero-engine rotor are measured using the surface hot film, synchronous phase-locked loop device, and slip ring; the interstage velocity field of the aero-engine is measured using the hot wire probe (or dynamic probe) and synchronous phase-locked loop device; and the blade vibration characteristics are measured using strain gauges, synchronous phase-locked loop device, and slip ring.

[0019] As a preferred implementation, the fluid-structure interaction numerical simulation of the rotor system of the aero-engine under test adopts a two-way fluid-structure interaction approach combining CFD flow field calculation and finite element structural simulation. Specifically, CFD calculation is first used to obtain the aerodynamic time history distribution on the rotor blade surface, and the aerodynamic calculation results are used as load inputs to the finite element model of the blade structure for dynamic response calculation. Subsequently, the deformation results of the structure are fed back to the CFD domain, thereby realizing two-way data exchange and coupled calculation between the fluid and the structure. The location of unsteady vibration prominence is identified by the equivalent stress or displacement amplitude distribution on the blade surface, and the location of unsteady boundary layer separation and reattachment on the rotor blade surface is identified by the wall shear coefficient and pressure gradient. Finally, the local airflow direction at the test location of the interstage flow field is determined based on the time-averaged results of the interstage velocity field.

[0020] Furthermore, in the fluid-structure interaction numerical simulation, the Reynolds-averaged Navier-Stokes (RANS) equations or the Large Eddy Simulation (LES) method are preferred for flow field calculation. The SST k-ω model or the LES model coupled with a transition model is selected for the turbulence model to accurately capture the transition and separation phenomena within the boundary layer. The structural calculation adopts the dynamic finite element method, considering the elastic modulus, Poisson's ratio, and density of the blade material, and calculates the stress distribution and natural frequency of the blade under the combined action of centrifugal force and aerodynamic force. The fluid-structure interaction calculation adopts a two-way iterative coupling method, alternately solving the flow field and structural field in each time step. The load and deformation transfer between the flow field mesh and the structural mesh is realized through the interpolation algorithm until the flow field force and structural response reach convergence, obtaining accurate unsteady fluid-structure interaction characteristics, and providing a reliable basis for the subsequent experimental measurement device layout.

[0021] S200. Arrangement of test and measurement equipment: Strain gauges are placed at locations where unsteady vibration of the rotor blades is prominent, and surface thermal films are applied to locations where the boundary layer of the rotor blade surface is unsteady and significantly separated. Hot wire probes or dynamic probes are installed in the interstage channels, with the hot wire plane perpendicular to the local incoming flow direction or the hole in the dynamic probe facing the incoming flow direction.

[0022] Specifically, the arrangement of the experimental measurement device is determined as follows: Based on the fluid-structure interaction numerical simulation in step S100, the locations of prominent unsteady vibrations of the aero-engine rotor blades, the locations of significant unsteady separation and reattachment of the rotor blade boundary layer, and the airflow direction at the locations to be measured in the interstage velocity field are obtained. The locations of prominent unsteady vibrations of the rotor blades are used as the locations for strain gauge installation, and the locations of significant unsteady separation and reattachment of the rotor blade boundary layer are used as the locations for surface thermal film installation. The two-dimensional hot wire probe is adjusted so that the plane of the two-dimensional hot wire is perpendicular to the airflow direction at the location to be measured. If a four-hole dynamic probe is used, the attitude of the dynamic probe is adjusted according to the local airflow direction so that the central hole of the four-hole probe faces the incoming airflow direction.

[0023] As a preferred option, the strain gauges and surface thermal films are arranged as follows when they are applied to the rotor blade surface: several areas with prominent unsteady vibrations and significant boundary layer separation and reattachment are selected along the blade spanwise and chordwise directions, and at least one strain gauge is arranged in the high-load area of ​​the blade suction surface and the high-stress area at the blade root. The thermal film applied to the blade suction surface should cover the boundary layer separation, reattachment, and transition positions. The wires at each measuring point are embedded or buried to reduce secondary interference to the boundary layer flow and ensure the accuracy and reliability of the measurement results.

[0024] Furthermore, when setting up hot-wire probes or dynamic probes in the interstage channel, the following arrangement is adopted: A two-dimensional hot-wire probe is selected, with two miniature hot wires arranged at its tip. A calibration coefficient matrix is ​​obtained by establishing the correspondence between the voltage of the two hot wires and the magnitude and direction of the velocity in the plane through pre-flow calibration. During actual measurement, the two-dimensional velocity vector of the interstage flow field is obtained by inverting the calibration relationship based on the voltage output of the two hot wires. When using a dynamic probe scheme, a four-hole high-frequency dynamic pressure probe is selected, with four pressure holes arranged at its tip. The central hole faces the incoming flow direction to measure the total pressure, and the other three holes are used to measure static pressure and directional information. A correspondence between the pressure difference of each hole and the local angle of attack and total pressure is established through static and dynamic calibration, obtaining an aerodynamic calibration curve or calibration database. During the experimental setup, the probe attitude is adjusted according to the local airflow direction, ensuring that the plane containing the hot wires is perpendicular to the incoming flow direction or that the central hole of the dynamic probe faces the incoming flow direction, ensuring the probe is in the optimal measurement state and improving measurement accuracy and sensitivity.

[0025] S300. Construction of Synchronous Phase-Locked Measurement System: A synchronous phase-locked device is set up, including a phase-locked trigger and a phase-locked amplifier. The surface hot film, strain gauge, and hot wire probe or dynamic probe are communicatively connected to the synchronous phase-locked device. The phase-locked trigger generates a unified reference signal and a trigger signal, which are transmitted to each measurement device respectively. Each measurement channel completes phase-locked amplification and signal conditioning based on the same reference signal in the phase-locked amplifier, thereby realizing phase synchronization and time alignment of multi-physics field measurement signals.

[0026] In this embodiment of the invention, the measurement signals of the surface thermal film and strain gauges disposed on the rotor blades are transmitted to the stationary side measurement circuit via a high-fidelity slip ring. The high-fidelity slip ring adopts a contact slip ring or a fiber optic rotary connector, and has a multi-channel loop that meets the channel requirements of the surface thermal film and strain gauges. The slip ring also integrates a signal conditioning circuit that performs impedance matching and pre-amplification processing on the transmitted signal. It has a bandwidth and low contact resistance fluctuation characteristics that are adapted to the frequency range of the unsteady signal to be measured, so as to reduce the influence of speed changes and mechanical vibration on the signal amplitude and phase, and realize the complete and stable transmission of the weak electrical signal on the rotor side under high-speed rotation conditions.

[0027] In this embodiment of the invention, the implementation process of the synchronous phase-locked loop measurement system for the boundary layer, interstage flow field, and blade vibration characteristics of aero-engine rotor blades is as follows: Figure 2 As shown. The system generates a common trigger signal and reference signal through a unified phase-locked loop triggering device, ensuring that all measurements are based on the same time reference and phase period. During measurement, the signals obtained by the surface hot film and hot wire probe are processed by the temperature-controlled circuit in the hot film anemometer, and output as the hot film and hot wire measurement signals after temperature control and primary filtering. If a four-hole dynamic probe is used instead of a two-dimensional hot wire probe, the signal after the dynamic probe is filtered and conditioned by the dynamic pressure signal conditioner should also be included. At the same time, the strain gauge signal is converted by the Wheatstone bridge of the dynamic strain gauge, and the blade vibration strain signal is amplified and primary filtered. The various test signals and reference signals after being conditioned by the temperature-controlled circuit, dynamic pressure signal conditioner and dynamic strain gauge are input into the lock-in amplifier for synchronous demodulation and narrowband filtering.

[0028] Preferably, the phase-locked trigger uses a speed pulse or phase signal generated by a photoelectric encoder, magnetoelectric sensor, or Hall sensor arranged coaxially with the rotor as input. The digital signal processing circuit inside the phase-locked trigger performs frequency multiplication, frequency division, or phase-locked loop processing on the input pulse signal to generate a reference signal corresponding to the rotor fundamental frequency and several harmonic frequencies. The reference signal is then distributed to the surface hot film measurement channel, the hot wire or dynamic probe measurement channel, and the strain gauge measurement channel, so that the phase-locked amplification process of each channel is demodulated with the same time base and phase period to obtain boundary layer, interstage flow field, and blade vibration unsteady signals with clear phase significance relative to the rotor azimuth angle.

[0029] In addition, the lock-in amplification process in the lock-in amplifier preferably includes: (1) phase-sensitive detection, multiplying the time-varying signal output by each measuring device with the reference signal to achieve frequency domain shift of the signal, so that each measuring signal is demodulated relative to the same reference signal to ensure the correspondence of different measuring signals in phase; (2) low-pass filtering, filtering out high-frequency components through a low-pass filter and extracting useful signal components that are in phase with the reference signal. The cutoff frequency and order of the filter are optimized according to the frequency characteristics and noise level of the signal to be measured to effectively suppress noise interference of asynchronous frequencies, including white noise, power frequency interference and other random noise; (3) adjustable gain amplification, amplifying and conditioning the extracted signal through an adjustable gain amplifier. The gain of the amplifier can be independently adjusted according to the signal amplitude range of each measuring channel to ensure that the output signal amplitude is adapted to the range of the subsequent data acquisition system, while maintaining the signal dynamic range and signal-to-noise ratio of each channel.

[0030] S400. Multi-channel synchronous data acquisition: By utilizing a multi-channel data acquisition system, and under the unified time and phase reference provided by the synchronous phase-locked loop device, the phase-locked output signals of each measurement channel are synchronously acquired and stored, so that each measured physical quantity has a one-to-one correspondence under the unified time reference and phase period, providing a reliable data foundation for subsequent fluid-structure interaction characteristic analysis.

[0031] In this embodiment of the invention, the multi-channel data acquisition system preferably includes multiple data sampling channels. The number of channels is determined according to the number of measurement points, typically 16-128 channels. Each data sampling channel, lock-in trigger, and lock-in amplifier shares the same high-precision clock source. This clock source uses a temperature-compensated crystal oscillator or atomic clock, exhibiting an extremely low clock drift rate (typically less than 1 ppm), ensuring the stability of the time reference during long-term measurements. The multi-channel data acquisition system receives the trigger signal generated by the lock-in trigger as the acquisition start signal. Upon the arrival of each trigger pulse, data acquisition of all channels is synchronously initiated, achieving precise alignment of the data from each measurement channel in the time dimension. The output signals of each measurement channel, after processing by the lock-in amplifier, are stored according to timestamps and rotor phase angles, ensuring that the signals from surface hot films, hot wires, dynamic probes, and strain gauges correspond to the same rotor angular position and the same phase period at strictly identical sampling times. The data storage format adopts a multi-dimensional array structure: the first dimension is time or phase, the second dimension is the channel number, and the third dimension is the physical quantity type, facilitating subsequent data processing and analysis.

[0032] In addition, multi-channel data synchronous acquisition also includes: (1) sampling frequency selection. The sampling frequency is selected according to the frequency range of the unsteady phenomenon to be measured, so that the sampling frequency is at least several times the rotor passing frequency and its highest harmonic frequency of interest, so as to meet the Nyquist sampling criterion and have a preset frequency margin. For example, for a rotor system with a rotational speed of 10,000 rpm (rotor fundamental frequency of about 167 Hz) and 20 blades, the blade passing frequency is 3340 Hz. If the 5th harmonic is of interest, the sampling frequency should not be lower than 33.4 kHz. In practical applications, 50-100 kHz is usually selected. (1) kHz to obtain better time domain resolution and frequency domain analysis capability; (2) Sampling time window setting: set the sampling time window to cover multiple rotor rotation cycles, preferably covering 10-100 rotor rotation cycles, so as to perform phase averaging and spectrum analysis later; (3) Quantization accuracy requirements: each channel of the multi-channel data acquisition system preferably has a quantization accuracy of not less than 16 bits. For weak signal measurement occasions, a 24-bit high-precision ADC can be used to ensure the ability to distinguish small signal changes such as hot film voltage, hot wire or dynamic pressure and strain voltage. The dynamic range usually reaches more than 90 dB, and the effective number of bits (ENOB) is not less than 14 bits.

[0033] It should be noted that in this embodiment of the invention, all test systems share the same high-precision clock source. The lock-in trigger, lock-in amplifier, and multi-channel data acquisition system all operate based on this clock source, ensuring the time synchronization of the entire measurement system. The multi-channel data acquisition system synchronously acquires the amplified signals from the lock-in circuit, achieving data acquisition of different physical signals at strictly identical times. Measurement signals on key rotating components are transmitted through high-fidelity slip rings, effectively ensuring signal integrity and signal-to-noise ratio under high-speed rotation conditions. Finally, the system synchronously outputs and stores raw data such as hot-film voltage, hot-wire velocity, and strain voltage at the same time. Subsequent processing yields multi-dimensional coupled information such as rotor blade surface boundary layer characteristics, interstage flow field structure, and blade vibration response within the same period.

[0034] S500 Engine Rotor Coupling Characteristics Analysis: Based on synchronously acquired data, the measurement data are processed and analyzed under a unified time and phase reference to obtain the flow characteristics of the blade surface boundary layer, the interstage flow field characteristics, and the vibration characteristics of the rotor blade, thereby realizing the synchronous dynamic measurement of the surface boundary layer and interstage flow field of the aero-engine rotor blade.

[0035] Specifically, the analysis of engine rotor coupling characteristics includes: using the rotor phase signal provided by the phase-locked trigger as the independent variable, performing phase reconstruction and phase averaging on the synchronously acquired surface hot film, hot wire or dynamic probe and strain gauge signals respectively, to obtain the boundary layer shear force distribution, interstage velocity field or pressure field distribution and blade vibration strain distribution that vary with azimuth angle within a rotor channel; further, through power spectrum analysis and coherence function calculation, identifying the coupling characteristics between unsteady boundary layer separation, wake mixing structure and blade vibration modes, to achieve quantitative characterization of the fluid-structure interaction mechanism.

[0036] The acquisition of the boundary layer flow characteristics on the blade surface includes: based on the voltage signal measured by the surface thermal film, the voltage value is converted into wall shear stress through a pre-established calibration curve, thereby identifying the transition position, separation point and reattachment point of the boundary layer, and analyzing the scale and oscillation frequency of the separated bubble; the acquisition of the interstage flow field characteristics includes: based on the dual-channel voltage signal measured by the hot wire probe, the two-dimensional velocity vector is resolved through the flow direction calibration relationship, or based on the four-hole pressure signal measured by the dynamic probe, the flow field velocity and pressure are calculated through aerodynamic calibration data; the acquisition of the rotor blade vibration characteristics includes: based on the strain voltage signal measured by the strain gauge, the blade surface stress is calculated through the strain-stress relationship, and the dominant frequency, amplitude and modal characteristics of the vibration are identified.

[0037] By comprehensively analyzing the above three types of physical quantities under a unified time and phase reference, the correlation between boundary layer flow, interstage flow field, and blade vibration is established. For example, the phase relationship between the blade surface pressure pulsation caused by interstage wake passage and the periodic changes in boundary layer separation and reattachment is analyzed; the influence of dynamic deformation of the blade surface caused by blade vibration on the location of the boundary layer flow separation point and the size of the separation bubble is analyzed; and the excitation effect and modal coupling effect of unsteady aerodynamic forces generated by interstage dynamic-static interference on blade vibration modes are analyzed. By constructing fluid-structure interaction transfer functions or coupling coefficient matrices, the interaction strength and energy transfer efficiency between multiple physical fields are quantitatively characterized, providing a scientific basis for aeroelastic stability analysis, vibration suppression design, and performance optimization of aero-engine rotor systems.

[0038] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A method for synchronous dynamic measurement of the boundary layer and interstage flow field on the surface of an aero-engine rotor blade, characterized in that, Includes the following steps: S100. Perform fluid-structure interaction numerical simulation on the rotor system of the aero-engine under test under a given rotational speed to obtain the prominent locations of unsteady vibration of rotor blades, significant locations of unsteady separation and reattachment of surface boundary layer, and airflow direction at the locations of the interstage flow field to be measured. S200. Strain gauges are placed at the locations of unsteady vibrations of the blade, and surface thermal films are applied to the locations of unsteady separation of the blade surface boundary layer. Hot wire probes or dynamic probes are installed in the interstage channels, with the hot wire plane perpendicular to the local flow direction or the hole of the dynamic probe facing the flow direction. S300. Set up a synchronous phase-locked device and connect the surface hot film, strain gauge, and hot wire or dynamic probe to the synchronous phase-locked device. Generate a unified reference signal and trigger signal through a phase-locked trigger and transmit them to each measuring device respectively. Make each measuring channel complete phase-locked amplification and signal conditioning based on the same reference signal in the phase-locked amplifier. S400. Using a multi-channel data acquisition system, the phase-locked output signals of each measurement channel are synchronously acquired and stored under the unified time and phase reference provided by the synchronous phase-locked device; S500. Process and analyze the synchronously acquired measurement data to obtain the boundary layer flow characteristics, interstage flow field characteristics, and rotor blade vibration characteristics on the rotor blade surface.

2. The method according to claim 1, characterized in that, In step S100, the fluid-structure interaction numerical simulation adopts a two-way fluid-structure interaction method that combines CFD flow field calculation and finite element structural simulation. The aerodynamic time history distribution on the rotor blade surface is obtained by CFD calculation, and the aerodynamic force is used as a load input to the finite element model of the blade structure for dynamic response calculation. Then, the response result of the structure is fed back to the CFD domain to realize two-way data exchange and coupled calculation between fluid and structure. The location of unsteady vibration protrusion is identified by the equivalent stress or displacement amplitude distribution on the blade surface. The location of unsteady separation and reattachment of the boundary layer on the rotor blade surface is identified by the wall shear coefficient and pressure gradient. The local airflow direction at the test location of the interstage flow field is determined based on the time-averaged result of the interstage velocity field.

3. The method according to claim 1 or 2, characterized in that, In step S100, in the fluid-structure interaction numerical simulation, the flow field calculation adopts the Reynolds-averaged Navier-Stokes equations or the large eddy simulation method, and the turbulence model is the SST k-ω model coupled with the transition model or the large eddy model; the structural calculation adopts the dynamic finite element method, considering the elastic modulus, Poisson's ratio and density of the blade material, and calculates the stress distribution and natural frequency of the blade under the combined action of centrifugal force and aerodynamic force; the fluid-structure interaction calculation adopts a two-way iterative coupling method, alternately solving the flow field and structural field in each time step, and realizing the load and deformation transfer between the flow field mesh and the structural mesh through the interpolation algorithm until the flow field force and structural response reach convergence.

4. The method according to claim 1, characterized in that, In step S200, when the strain gauge and surface thermal film are applied to the rotor blade surface, several areas with prominent unsteady vibration and significant boundary layer separation and reattachment are selected along the blade spanwise and chordwise directions, respectively. At least one strain gauge is arranged in the high-load area of ​​the blade suction surface and the high-stress area of ​​the blade root. The thermal film applied to the blade suction surface should cover the boundary layer separation position, reattachment position and transition position. The wires at each measuring point adopt an embedded or buried wiring method.

5. The method according to claim 1 or 4, characterized in that, In step S200, a two-dimensional hot wire probe is selected as the hot wire probe. Two miniature hot wires are arranged at the top of the probe. The correspondence between the voltage of the two hot wires and the magnitude and direction of the velocity in the plane is established through pre-flow direction calibration. A four-hole high-frequency dynamic pressure probe is selected as the dynamic probe. Four pressure holes are arranged in a 1:3 distribution along the axial direction at the top of the probe. The correspondence between the pressure difference of each hole and the local angle of attack and the total pressure is established through static calibration and dynamic calibration. During the test setup, the probe posture is adjusted according to the local airflow direction so that the plane where the hot wire is located is perpendicular to the incoming flow direction or the middle hole of the dynamic probe is directly facing the incoming flow direction.

6. The method according to claim 1, characterized in that, In step S300, the measurement signals of the surface hot film and strain gauge are transmitted to the stationary side measurement circuit via a high-fidelity slip ring. The high-fidelity slip ring has a multi-channel loop that meets the channel requirements of the surface hot film and strain gauge, and the slip ring integrates a signal conditioning circuit that performs impedance matching and pre-amplification processing on the transmitted signal. It has bandwidth and low contact resistance fluctuation characteristics that are compatible with the frequency range of the unsteady signal to be measured.

7. The method according to claim 1 or 6, characterized in that, In step S300, the signals collected by the surface hot film and the hot wire probe are connected to the constant temperature circuit in the hot film anemometer. After constant temperature control and primary filtering, the output is used as the hot film and hot wire measurement signals. If the hot wire probe is replaced by a dynamic probe, its output pressure signal is connected to the dynamic pressure signal conditioner to complete the amplification, filtering and conditioning of static pressure and dynamic pressure. At the same time, the strain gauge is connected to the dynamic strain gauge to amplify and perform primary filtering on the blade vibration strain signal. The multi-channel test signals conditioned by the constant temperature circuit, the dynamic pressure signal processor and the dynamic strain gauge, together with the unified reference signal provided by the phase-locked trigger, are input to the lock-in amplifier for synchronous demodulation and narrowband filtering.

8. The method according to claim 7, characterized in that, In step S300, the phase-locked trigger uses a rotational speed pulse or phase signal arranged coaxially with the rotor as input to generate a reference signal corresponding to the rotor fundamental frequency and several harmonics. The reference signal is then distributed to the surface hot film measurement channel, the hot wire or dynamic probe measurement channel, and the strain gauge measurement channel, so that the phase-locked amplification process of each channel is demodulated with the same time reference and phase period to obtain boundary layer, interstage flow field and blade vibration unsteady signals with clear phase significance relative to the rotor azimuth angle.

9. The method according to claim 8, characterized in that, In step S300, the lock-in amplification process within the lock-in amplifier includes: multiplying the time-varying signals output by each measuring device with the reference signal to achieve frequency domain shifting of the signals, so that each measured signal is demodulated relative to the same reference signal to ensure the phase correspondence of different measured signals; filtering out high-frequency components through a low-pass filter to extract useful signal components that are in phase and frequency with the reference signal, and suppressing noise interference from asynchronous frequencies; and amplifying and conditioning the extracted signals through an adjustable gain amplifier.

10. The method according to claim 6, characterized in that, In step S400, the multi-channel data acquisition system includes multiple data sampling channels, and each data sampling channel, phase-locked trigger, and phase-locked amplifier shares the same high-precision clock source. The multi-channel data acquisition system receives the trigger signal generated by the phase-locked trigger as the acquisition start signal, and synchronously starts the data acquisition of all channels when each trigger pulse arrives. The output signal of each measurement channel after being processed by the phase-locked amplifier is stored according to the timestamp and rotor phase angle.

11. The method according to claim 1 or 10, characterized in that, In step S400, the multi-channel data synchronous acquisition also includes: selecting a sampling frequency according to the frequency range of the unsteady phenomenon to be measured, so that the sampling frequency is at least several times the rotor passing frequency and its highest harmonic frequency of interest, and setting a sampling time window to cover multiple rotor rotation cycles.

12. The method according to claim 1, characterized in that, In step S500, the rotor phase signal provided by the phase-locked trigger is used as the independent variable. The synchronously acquired surface hot film, hot wire or dynamic probe and strain gauge signals are reconstructed and averaged to obtain the boundary layer shear force distribution, interstage velocity field or pressure field distribution and blade vibration strain distribution that vary with azimuth angle in a rotor channel. Through power spectrum analysis and coherence function calculation, the coupling characteristics between boundary layer unsteady separation, wake mixing and blade vibration modes are identified, so as to achieve quantitative characterization of fluid-structure interaction mechanism.

13. The method according to claim 1 or 12, characterized in that, In step S500, based on the voltage signal measured by the surface thermal film, the voltage value is converted into wall shear stress through a pre-established calibration curve, thereby identifying the transition position, separation point and reattachment point of the boundary layer, and analyzing the scale and oscillation frequency of the separation bubble; The acquisition of interstage flow field characteristics includes: based on the dual-channel voltage signal measured by the hot wire probe, the two-dimensional velocity vector is analyzed through the flow direction calibration relationship; or based on the four-hole pressure signal measured by the dynamic probe, the flow field velocity and pressure are calculated through aerodynamic calibration data. The acquisition of rotor blade vibration characteristics includes: based on the strain voltage signal measured by the strain gauge, the blade surface stress is calculated through the strain-stress relationship, and the dominant frequency, amplitude and modal characteristics of the vibration are identified.

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