A high-precision measurement device and method for high-load turbine boundary layer

Abstract

The present invention relates to a high-precision measurement device and method for the boundary layer of a high-load turbine, comprising a boundary layer probe, a hot-wire probe, a surface thermal film, and a two-axis displacement control mechanism. The two-axis displacement control mechanism is used to control the boundary layer probe to perform steady-state measurement of the proximal end region of the blade end wall and the normal boundary layer. The two-axis displacement control mechanism is used to control the hot-wire probe to perform transient measurement of the proximal end region of the blade end wall and the normal boundary layer. The surface thermal film is used to perform transient measurement of the boundary layer of the blade end wall. Steady-state and unsteady-state measurement of the boundary layer in the end region and proximal end region of a high-load turbine is achieved by combining three technologies: a boundary layer probe technology with an end wall detection function, a hot-wire probe technology with an end wall detection function, and a surface thermal film measurement technology. This solves the problem of difficulty in measuring complex fluid characteristics such as boundary layer separation and radial migration of fluid caused by large turning angles of high-load turbine blades.

Description

Technical Field

[0001] The present invention belongs to the technical field of aero-engine / gas turbine turbine machinery and relates to a high-precision measurement device and method for a high-load turbine boundary layer. Background Art

[0002] The turbine is one of the core components of an aircraft engine / gas turbine. Its internal flow field is essentially a complex flow characterized by strong three-dimensionality, strong unsteadiness, and strong shear, operating under high temperature, high pressure, and strong pressure and temperature gradients. For high-performance gas turbines, achieving low weight, high efficiency, and a high thrust-to-weight ratio requires maximizing blade load. However, high blade loads inevitably increase the lateral pressure gradient and flow-direction reverse pressure gradient within the turbine, leading to easy separation of the boundary layer on the suction surface of the turbine blade, forming a separation bubble. Losses caused by the separation bubble, the transition to the free shear layer, and turbulent mixing during reattachment result in aerodynamic losses on the suction surface accounting for up to 60% of the blade profile losses, severely deteriorating the turbine's aerodynamic performance. Therefore, effectively reducing or suppressing boundary layer flow separation is a major challenge facing the aerodynamic design of high-load, low-pressure turbine blades. The key to solving this problem lies in understanding the complex unsteady flow field structure within the turbine.

[0003] Currently, there are two main approaches to understanding the structure of unsteady flow fields: CFD calculations and experimental measurements. Because the actual flow field inside a turbine is characterized by sharp transitions, strong shear, and large separation, the accuracy of CFD calculations is often low. Therefore, a high-precision measurement technique is needed to reproduce the flow field structure and improve our understanding of unsteady flow inside turbines.

[0004] Currently, methods for measuring the boundary layer of high-load turbines primarily include boundary layer probes, hot wire probes, and surface hot film techniques. Boundary layer probes have a simple structure and require relatively low operating conditions. To measure thin-wall boundary layers, the probe head is typically flat. However, boundary layer probes suffer from long response times and low spatial resolution, making them incapable of measuring unsteady signals. Hot wire probes are compact, minimize flow field interference, have fast response times, and offer high temporal and spatial resolution, effectively capturing unsteady signals. However, hot wire probes have complex internal structures and require not only a hot wire anemometer but also temperature correction during operation. Furthermore, when operating extremely close to the wall, they are susceptible to radiation heat transfer from the metal endwall, resulting in significant measurement errors. Furthermore, both boundary layer probe and hot wire probe technologies are limited to intermittent measurements, resulting in low efficiency. They are also susceptible to interference from rotating blades, making it difficult to accurately transmit boundary layer flow signals in real time. Furthermore, both are non-contact methods, limiting their measurement capabilities to the boundary layer near the endwall and are susceptible to damage when operating extremely close to the wall.

[0005] Surface hot film measurement technology is a contact-based measurement method that can continuously measure boundary layer data at the endwall. It features high-frequency response, high synchronization, and minimal flow field disturbance. For rotating blades, it can also ensure real-time and accurate transmission of boundary layer unsteady flow signals, making it a significant advantage in boundary layer measurement. However, the characteristics of surface hot film measurement technology limit its ability to measure data only at the blade endwall, and it cannot measure boundary layer flows near the endwall. Furthermore, like hot wire probe technology, it has a complex internal structure and requires temperature correction and the integration of a hot wire anemometer.

[0006] Therefore, there is an urgent need for a relatively complete set of measurement devices and methods that can obtain steady-state and unsteady-state data of the boundary layer in the turbine end and proximal areas, so as to solve the problem of difficulty in measuring complex fluid characteristics such as boundary layer separation and radial migration of fluid caused by large turning angles of high-load turbine blades. Summary of the Invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a high-precision measurement device and method for the boundary layer of a high-load turbine. By combining three technologies: boundary layer probe technology with end wall detection function, hot wire probe technology with end wall detection function and surface hot film measurement technology, steady-state and unsteady-state measurements of the boundary layer in the end area and near-end area of ​​a high-load turbine can be achieved.

[0008] The technical solution adopted by the present invention to solve its technical problems is:

[0009] A high-precision measurement device for a high-load turbine boundary layer according to the present invention comprises:

[0010] Boundary layer probe, hot wire probe, surface hot film and two-axis displacement control mechanism;

[0011] The boundary layer probe consists of a boundary layer probe, an intake duct, an air bleed duct, a support tube, and a boundary layer probe end wall detection sensor. The boundary layer probe is flat and waist-shaped to facilitate measuring the thin boundary layer at the end wall. The intake duct is connected to the boundary layer probe to guide the fluid entering the boundary layer probe. The support tube is used to support and fix the intake duct and air bleed duct, and the two ends are connected by soft rubber. The boundary layer probe end wall detection sensor is located at the tail of the boundary layer probe and is used to monitor whether the boundary layer probe hits the end wall.

[0012] The hot wire probe includes a metal wire, a hot wire fork rod, a hot wire probe, a connecting device, a hot wire body, a hot wire probe end wall detection sensing device cable and a hot wire probe signal transmission cable; the metal wire is located between the hot wire fork rods; the hot wire fork rods are tapered and located on the hot wire probe; the hot wire probe has a circular through hole inside, which is used to lead the end wall detection sensing device cable and the signal transmission cable from the hot wire body to the hot wire fork rod; the connecting device is tapered and located on the hot wire body, which is used to connect the hot wire probe; the hot wire body is used to fix and support the hot wire probe device, and at the same time, it is loaded with the end wall detection sensing device cable and the signal transmission cable; the hot wire probe end wall detection sensing device cable is used to transmit the wall collision information of the hot wire probe device to the external control device; the hot wire probe signal transmission cable is used to transmit the measured original signal to the external control device;

[0013] A two-axis displacement control mechanism, installed on the wind tunnel test equipment, includes two degrees of freedom of motion (X and Y axes) and comprises a flat base, a lateral motion mechanism, a longitudinal motion mechanism, and a probe mounting mechanism. The flat base is used to secure the displacement control mechanism and connect the experimental equipment. The lateral motion mechanism includes a lateral pulley, a lateral support platform, a lateral slide, a lateral screw, and a lateral control unit. The lateral motion mechanism is mounted on the flat base, and the lateral control unit includes a lateral stepper motor, a lateral driver, and a lateral controller. The lateral stepper motor drives the lateral screw via the lateral driver. The other end of the lateral screw is rotatably supported on the lateral pulley. The lateral support platform is supported on the lateral screw via a screw nut, and the two ends of the lateral support platform are guided by lateral slides. In this way, the lateral control unit, together with the lateral pulley, lateral slide, and lateral screw, controls the axial motion of the probe along the blade. The longitudinal motion mechanism includes a first support rib, a longitudinal pulley, a longitudinal slide rail, a second support rib, a longitudinal support platform, a longitudinal screw, and a longitudinal control unit. A longitudinal displacement control unit is mounted on the transverse support platform and is fixed and supported by the first support rib. The longitudinal control unit includes a longitudinal stepper motor, a longitudinal driver, and a longitudinal controller. The longitudinal stepper motor drives the longitudinal screw via the longitudinal driver. The other end of the longitudinal screw is rotationally supported on the longitudinal pulley. The longitudinal support platform is supported on the longitudinal screw via a screw nut, and both ends of the longitudinal support platform are guided by the longitudinal slide rail. Thus, the longitudinal control unit, together with the longitudinal pulley, longitudinal slide rail, and longitudinal screw, controls the movement of the probe along the circumference of the blade. The probe mounting mechanism includes a probe support platform and a probe holder. A probe support platform is mounted on the longitudinal support platform, which has five waist-shaped through-holes arranged at equal intervals. The probe, located on the probe support platform, is secured and locked by a probe holder. The probe holder is split in half, with a central through-hole. Countersunk screws connect the two holders and the probe holder to the probe support platform.

[0014] The surface thermal film includes a thermal film measuring unit and a surface thermal film base plate. The thermal film measuring unit is arranged on the surface thermal film base plate. The thermal film measuring unit includes a wire and a temperature sensor. The two ends of the temperature sensor are connected with wires. The wires are used to transmit current and signals. The temperature sensor is used to collect the temperature difference caused by convective heat transfer.

[0015] A high-precision measurement method for a high-load turbine boundary layer according to the present invention comprises the following steps:

[0016] SS1, using a two-axis displacement control mechanism to control the boundary layer probe to perform steady-state measurements on the blade endwall proximal area and normal boundary layer;

[0017] SS2, using a two-axis displacement control mechanism to control the hot wire probe to perform transient measurements on the blade endwall proximal area and normal boundary layer;

[0018] SS3, transient measurement of the blade endwall boundary layer using a surface hot film;

[0019] SS4, through boundary layer probe sweep measurement, obtains the fluid velocity along the wall normal at the blade cross section, and then obtains the time-averaged velocity distribution in the normal direction of the blade suction surface wall. By analyzing the velocity distribution, the changes in the suction surface boundary layer at each axial position in the blade channel are obtained; through hot wire probe sweep measurement, the pulsation curve of the fluid velocity in the boundary layer with time is obtained, and according to its transient velocity fluctuation, the boundary layer state and boundary layer separation and reattachment data are obtained; through the original signal obtained by surface hot film measurement, according to the positive peak and negative peak signal signs, the boundary layer transition interval data at the blade end wall is obtained.

[0020] The advantages of the present invention compared with the prior art are:

[0021] (1) The present invention proposes a high-precision measurement method for the boundary layer of a high-load turbine, which solves the problem of difficulty in measuring complex fluid characteristics such as boundary layer separation and radial migration of fluid caused by large turning angles of high-load turbine blades. It also solves the problem of being unable to achieve real-time and faithful transmission of dynamic signals of the boundary layer on the blade surface at high speeds, and realizes the measurement of steady-state and transient data of the end zone, near-end zone and normal boundary layer.

[0022] (2) On the one hand, the present invention uses a boundary layer probe to perform steady-state measurements of the boundary layer and a hot-wire probe to perform transient measurements of the boundary layer, thereby resolving the problem that the surface thermal film measurement technology can only measure boundary layer data at the blade end wall. Furthermore, the two-axis displacement control mechanism is used to resolve the problem that boundary layer probes and hot-wire probes can only measure at breakpoints, resulting in low efficiency. The probe end wall detection sensor is used to resolve the problem that both probes are easily damaged by the wall when they are extremely close to the wall. On the other hand, the surface thermal film measurement technology is used to resolve the problem that boundary layer probes and hot-wire probes cannot measure boundary layer data at the blade end wall and that it is difficult to transmit boundary layer flow signals in real time with high-speed rotation of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of a high-precision measurement method for a high-load turbine boundary layer according to the present invention.

[0024] Figure 2 Schematic diagram of the boundary layer probe structure of the present invention.

[0025] Figure 3 Schematic diagram of the hot wire probe structure of the present invention.

[0026] Figure 4 This is a diagram of the probe end wall detection sensing circuit of the present invention.

[0027] Figure 5 It is a schematic structural diagram of the two-axis displacement control mechanism of the present invention.

[0028] Figure 6 It is a schematic diagram of the surface thermal film structure of the present invention.

[0029] Figure 7 It is a schematic structural diagram of the steady-state experimental measurement device of the proximal region and normal boundary layer of the present invention.

[0030] Figure 8 It is a schematic structural diagram of the transient experimental measurement device of the proximal region and normal boundary layer of the present invention.

[0031] Figure 9 It is a schematic structural diagram of the end wall boundary layer transient experimental measurement device of the present invention.

[0032] Figure numerals: air bleed pipe 1, support pipe 2, boundary layer probe end wall detection sensor 3, air intake pipe 4, boundary layer probe 5, metal wire 6, hot wire fork rod 7, hot wire probe 8, connecting device 9, hot wire probe 10, hot wire probe end wall detection sensing device cable 11, hot wire probe signal transmission cable 12, transverse pulley 13, transverse support platform 14, transverse slide rail 15, transverse screw rod 16, flat plate base 17, transverse control unit 18, first supporting rib 19, longitudinal pulley 20, longitudinal slide rail 21, second supporting rib 22, longitudinal support platform 23, longitudinal screw rod 24, longitudinal control unit 25, probe supporting platform 26, probe holder 27, wire 28, temperature sensor 29, surface thermal film bottom plate 30, turbine blade 31, grid plate 32, two-axis displacement control mechanism 33, boundary layer probe 34, hot wire probe 35, rotor blade 36, surface thermal film 37, thermal film lead 38, grid plate 39. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the implementation of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The structure and technical solutions of the present invention are further described in detail below in conjunction with the drawings, and an embodiment of the present invention is given.

[0034] like Figure 1 As shown, in a high-load turbine boundary layer high-precision measurement device and method of the present invention, the boundary layer probe belongs to a non-contact measurement technology. Due to its simple structure, high measurement accuracy, and low working condition requirements, the boundary layer probe is used to perform steady-state measurements of the proximal area of ​​the blade end wall and the normal boundary layer; the hot wire probe also belongs to a non-contact measurement technology, but it has the characteristics of small size, small interference to the flow field, short response time, and high time and space resolution. It can effectively capture unsteady signals and can perform transient measurements of the proximal area and the normal boundary layer. The combination of these two measurement technologies can obtain steady-state and transient data of the proximal area and the normal boundary layer, solving the problem that the surface hot film measurement technology can only measure the boundary layer data of the blade end wall, and solving the problem that the two can only measure at breakpoints and have low efficiency through the two-axis displacement control mechanism, and solving the problem that the two are easily damaged by the wall when they are extremely close to the wall through the probe end wall detector. Surface hot film measurement technology is a contact measurement technique. Its characteristics of continuity, high-frequency response, high synchronization, and minimal flow field disturbance address the inability of boundary layer probes and hot wire probes to measure boundary layer data at the blade endwall, as well as the difficulty in accurately transmitting boundary layer flow signals in real time under high-speed blade rotation. In summary, this invention organically combines boundary layer probes, hot wire probes, and surface hot film measurement techniques to achieve steady-state and transient data measurement in the end zone, near-end zone, and normal boundary layer.

[0035] like Figure 2As shown, the boundary layer probe 34 consists of a boundary layer probe 5, an intake duct 4, an air bleed duct 1, a support tube 2, and a boundary layer probe end wall detection sensor 3, with a total length of 320 mm. The boundary layer probe 5 is a flat, waist-shaped hole with a width of 2.5 mm, which allows for measuring thin boundary layers at the end wall, increasing spatial resolution and improving measurement accuracy. The intake duct 4, connected to the boundary layer probe 5, is a circular tube 8 mm long and 1 mm in diameter, used to guide the boundary layer fluid entering the boundary layer probe 5. The air bleed duct 1 is a circular tube 2 mm in diameter, used to guide and transfer the fluid from the intake duct 4. The support tube 2 is a circular tube 280 mm long and 3 mm in diameter, used to support and secure the intake duct 4 and air bleed duct 1, and its two ends are connected by soft glue. The boundary layer probe end wall detection sensor 3 is located at the rear of the boundary layer probe and is used to monitor whether the boundary layer probe hits the end wall.

[0036] like Figure 3 As shown, the hot wire probe 35 is a one-dimensional hot wire probe and includes a metal wire 6, a hot wire fork 7, a hot wire probe 8, a connecting device 9, a hot wire body 10, a hot wire probe end wall detection sensing device cable 11, and a hot wire probe signal transmission cable 12. The metal wire 6 is located between the hot wire forks 7. It is 1.25 mm long and 5 μm in diameter. It is made of gold-plated tungsten wire and forms a 70° angle with the hot wire forks 7. The hot wire forks 7 are conical and 5 mm long. They are located on the hot wire probe 8 and are arranged in a straight line, equidistantly with a spacing of 0.6 mm. The hot wire forks 7 are made of stainless steel. The hot wire probe 8 is a long cylinder, 17 mm long and 1.9 mm in diameter. It has a circular through-hole inside for routing the hot wire probe end wall detection sensing device cable 11 and the hot wire probe signal transmission cable 12 from the hot wire body 10 to the hot wire forks 7. Connecting device 9 is a tapered, 3mm long connector located on hot-wire probe 10. It connects to hot-wire probe 8. Hot-wire probe 10, 235mm long and 4mm in diameter, secures and supports the hot-wire probe assembly. It also houses the end-wall detection sensing cable and signal transmission cable. The end-wall detection sensing cable 11 transmits wall-impact information to an external control device. The signal transmission cable 12 transmits the measured raw signal to the external control device.

[0037] The working principle of the hot wire probe 35 is thermal balance. That is, the hot wire 6 is located in the blade channel. When the airflow passes through, part of the heat is carried away by the airflow due to heat exchange, resulting in a temperature difference. The magnitude and speed of the temperature change are related to the airflow velocity and the temperature difference between the airflow and the hot wire 6, thereby establishing a relationship between the hot wire temperature and the airflow velocity.

[0038] In addition, the hot wire probe 35 needs to be temperature corrected before operation, and the correction formula is:

[0039]

[0040] in is the temperature correction coefficient, is the output voltage at different heights from the metal wall (air velocity is zero), is the output voltage at the center of the leaf (air velocity is zero), and the parameter A 、 B 、 n It can be obtained from the fitting curve of the calibrated wind tunnel.

[0041] The boundary layer probe 34 and the hot wire probe 35 are respectively equipped with end wall detection sensors and their corresponding cables to monitor the distance between the probe and the end wall, thereby preventing the two probes from being damaged by the wall and the metal end wall radiation heat transfer from causing large measurement errors to the hot wire probe. Figure 4 As shown, the circuit consists of a power supply, switch, voltmeter, ammeter, and LED light. The power supply is a 3V DC power supply, and the switch is a pushbutton switch. These two are connected in series with the LED light and ammeter to form the main circuit. The voltmeter is connected in parallel with them. The circuit between the ammeter and the switch is disconnected, with one end connected to the hot wire probe and the other to the end wall. When the end wall detection sensor's switch is closed, the probe is disconnected under normal operating conditions. However, when the hot wire probe moves very slowly toward the wall, the circuit connects only when the probe nearly touches the non-contact wall. At this point, the LED light flashes, and the voltmeter and ammeter display readings. Stopping the probe at this point can prevent damage to the probe from hitting the wall.

[0042] like Figure 5As shown, a two-axis displacement control mechanism 33 is installed in the wind tunnel test equipment to fix and carry the probe, driving the probe to move across the blade surface, solving the problem of low efficiency in probe breakpoint measurement. To enable the probe to move axially and circumferentially on the blade midsection, the two-axis displacement control mechanism includes two degrees of freedom of motion: X-axis and Y-axis. It includes a flat base 17, a lateral motion mechanism, a longitudinal motion mechanism, and a probe mounting mechanism. The flat base 17 is used to fix the displacement control mechanism and connect to the experimental equipment. The lateral motion mechanism includes a lateral pulley 13, a lateral support platform 14, a lateral slide 15, a lateral screw 16, and a lateral control unit 18. The lateral motion mechanism is mounted on the flat base 17. The lateral control unit 18 includes a lateral stepping motor, a lateral driver, and a lateral controller. The lateral stepping motor drives the lateral screw 16 via the lateral driver. The other end of the lateral screw 16 is rotatably supported on the lateral pulley 13. The lateral support platform 14 is supported on the lateral screw 16 via a screw nut. The two ends of the lateral support platform 14 are guided by the lateral slide 15. In this way, the transverse control unit 18, together with the transverse pulley 13, the transverse slide 15, and the transverse screw 16, controls the movement of the probe along the axial direction of the blade. The longitudinal movement mechanism includes a first support rib 19, a longitudinal pulley 20, a longitudinal slide 21, a second support rib 22, a longitudinal support platform 23, a longitudinal screw 24, and a longitudinal control unit 25. The transverse support platform 14 is equipped with a longitudinal control unit 25, which is fixed and supported by the first support rib 19. The longitudinal control unit 25 includes a longitudinal stepping motor, a longitudinal driver, and a longitudinal controller. The longitudinal stepping motor drives the longitudinal screw 24 to move through the longitudinal driver. The other end of the longitudinal screw 24 is rotatably supported on the longitudinal pulley 20. The longitudinal support platform 23 is supported on the longitudinal screw 24 through a screw nut. The two ends of the longitudinal support platform 23 are guided by the longitudinal slide 21. In this way, the longitudinal control unit 25, together with the longitudinal pulley 20, the longitudinal slide 21, and the longitudinal screw 24, controls the movement of the probe along the circumferential direction of the blade.

[0043] The probe mounting mechanism includes a probe support 26 and a probe holder 27. The probe support 26 is mounted on the longitudinal support 23. It has five waist-shaped through-holes, spaced equidistantly at 75 mm intervals, for adjusting the probe's position along the blade span. The probe on the probe support 26 is secured and locked by a probe holder 27. The probe holder 27 is split in half, with a central through-hole. Countersunk screws connect the two halves, as well as the probe holder 27 to the probe support 26.

[0044] The motion control of the two-axis displacement control mechanism is as follows: the external test system outputs the displacement control signal to the controller in the horizontal and vertical control unit, the controller performs A / D conversion on the signal, and then determines the number of pulses to be sent to the driver in the horizontal and vertical control unit according to the set ratio. The driver performs A / D conversion again and drives the horizontal and vertical stepper motors according to the number of pulses to drive the lead screw to rotate, so that the horizontal and vertical support tables move along the horizontal and vertical slide rails respectively, driving the probe to the specified position. At the same time, the stepper motor will feed back the motor position signal to the controller, and then the controller will feed back to the test system to observe whether it has moved into place.

[0045] like Figure 6 As shown, the surface thermal film 37 structure operates on the principle of thermal equilibrium. This involves heating the surface thermal film through a hot-wire anemometer and maintaining a constant temperature within the flow field. The flow within the end wall boundary layer removes some of the heat through convective heat transfer. To maintain a constant temperature, the hot-wire anemometer continues to supply heat, causing the voltage applied across the surface thermal film to change. By monitoring this voltage change, changes in the fluid within the boundary layer can be detected. Furthermore, the surface thermal film requires temperature correction before operation. The correction method is the same as that for the hot-wire probe and will not be further described here. The surface thermal film of the present invention has a spatial resolution of up to 0.5 mm and includes a thermal film measurement unit and a surface thermal film substrate 30. To minimize disturbances to the end wall boundary layer, the thickness of the surface thermal film substrate is controlled to be less than 0.05 mm. The thermal film measurement unit includes a conductor 28 and a temperature sensor 29. The conductor 28 transmits current and signals, while the temperature sensor 29 detects temperature differences caused by convective heat transfer. A single surface thermal film is equipped with seven thermal film measurement units, enabling simultaneous monitoring of fluid changes at different locations on the blade surface.

[0046] A high-precision measurement method for a high-load turbine boundary layer according to the present invention comprises the following steps:

[0047] SS1, steady-state measurement of the blade endwall proximal region and normal boundary layer using a boundary layer probe;

[0048] SS2, transient measurements of the blade endwall proximal region and normal boundary layer using a hot wire probe;

[0049] SS3, transient measurement of the blade end wall boundary layer using surface hot film;

[0050] SS4, first, through boundary layer probe sweep measurement, the fluid velocity along the normal direction from the wall at the mid-section of the blade is obtained, and then the time-averaged velocity distribution in the normal direction of the suction surface and wall of the blade is obtained. By analyzing the velocity distribution, the changes in the boundary layer of the suction surface at each axial position in the blade channel can be obtained; second, through hot wire probe sweep measurement, the pulsation curve of the fluid velocity in the boundary layer with time can be obtained. According to its transient velocity fluctuation, the boundary layer state (laminar, turbulent, transition) and boundary layer separation and reattachment data can be obtained; third, the original signal obtained by hot film measurement, based on signal signs such as positive peaks and negative peaks, can be used to obtain data such as the boundary layer transition range at the blade end wall.

[0051] like Figure 7 As shown in the figure, the combination of a boundary layer probe and a two-axis displacement control mechanism is used as an example to illustrate the measurement process of the steady-state data of the proximal region of the turbine blade and the normal boundary layer, which mainly involves the turbine blade 31, the grid plate 32, the two-axis displacement control mechanism 33, and the boundary layer probe 34. The specific steps are:

[0052] SS11, Installing the Experimental Apparatus: To measure the boundary layer distribution at the blade midsection, ensure that the two-dimensional motion plane of the two-axis displacement control mechanism is parallel to the plane formed by the blade's axial and circumferential directions (B2B section), and that the boundary layer probe's head opening faces the incoming gas flow. First, install the two-axis displacement control mechanism 33 on the experimental apparatus, and secure the boundary layer probe to the third waist-shaped through-hole of the probe support 26 using the probe holder 27. The grid plate 32 is secured to the bottom of the flat base 17, with the boundary layer probe facing the blade wall.

[0053] SS12, Determine the measurement position: Activate the end wall detection sensor on the boundary layer probe. The external test system and the control unit of the two-axis displacement control mechanism 33 cooperate to drive the probe movement. First, the boundary layer probe is moved very slowly toward the blade wall. When the LED light on the end wall detection sensor flashes and the voltmeter and ammeter display readings, the two-axis displacement control mechanism 33 stops moving the probe and transmits the current position coordinates to the external test system for recording and use as the wall point. The boundary layer probe is then slowly moved circumferentially to a suitable position on the blade. The current position coordinates are then transmitted to the external test system for recording and use as the normal endpoint. The lateral and longitudinal displacement mechanisms then cooperate to repeat the above process, recording the wall point coordinates and the normal endpoint coordinates at multiple axial positions on the blade.

[0054] SS13, Experimental Measurement: After determining the boundary layer measurement location, the fan is started to introduce airflow into the blade channel. The two-axis displacement control mechanism 33 drives the boundary layer probe to move along the path set in the previous step. The data collected by the boundary layer probe 34 is transmitted from the tail of the boundary layer to the measurement system via a lead. After further processing, the steady-state data of the proximal region and the normal boundary layer are obtained.

[0055] Among them, SS2 uses a hot wire probe to perform transient measurements on the proximal area of ​​the blade end wall and the normal boundary layer; it mainly involves the turbine blade 31, grid plate 32, two-axis displacement control mechanism 33, and hot wire probe 35. The specific steps are:

[0056] SS21, Install the experimental device and determine the measurement position: In order to measure the transient data of the incoming flow boundary layer at the middle section of the blade, install the hot wire probe at the appropriate waist-shaped through-hole position of the two-axis displacement control mechanism according to the steps of SS11, and load the two-axis displacement control mechanism with the hot wire probe into the wind tunnel experimental equipment. The installation structure is as follows: Figure 8 As shown, the measurement position of the hot wire probe is then determined according to the steps of SS12.

[0057] SS22, Experimental Measurement: Before the experimental measurement, the hot-wire probe needs to be temperature-corrected to ensure that the temperature of the hot-wire probe in the flow field is exactly the same as the temperature during calibration, thus ensuring the accuracy of the measurement results. The hot-wire anemometer is then activated. The probe wire is heated to the preheating temperature and stabilized. The fan is then started to introduce airflow into the blade channel. The boundary layer probe is driven along a pre-set path by a two-axis displacement control structure. Simultaneously, a temperature sensor monitors the temperature difference generated by the convective heat transfer of the airflow. The temperature voltage signal is transmitted via the temperature sensor lead. This voltage signal is then transmitted to external testing equipment via the hot-wire probe signal transmission cable 12 for data processing, thereby obtaining transient data of the proximal region and normal boundary layer.

[0058] Among them, S3 uses the surface thermal film to perform transient measurement of the boundary layer on the blade end wall; taking the surface thermal film applied to the rotor blade end wall as an example, the measurement process of the transient data of the boundary layer on the turbine blade end wall is explained.

[0059] S31, install the experimental device: rotor blades 36, surface thermal film 37, thermal film lead 38, grid plate 39, installation structure as shown Figure 9 First, the measurement position on the blade surface is determined. The present invention applies a surface thermal film 37 to the blade suction surface, 30 mm from the blade tip and root. Thermal film leads 38 run along the surface of the rotor blade 36 and connect to a grid plate 39. This leads through the grid plate 39 to an external hot wire anemometer and test system.

[0060] S32, Experimental Measurement: The motor and hot-wire anemometer are then started, rotating the rotor blades while heating the surface hot film to a stable temperature via the hot-film lead 38 and the wire 28 within the hot-film measurement unit. Immediately thereafter, the fan is started to introduce airflow into the blade channel. The temperature difference generated by the convective heat transfer of the airflow is monitored via the temperature sensor 29. This signal is transmitted to the hot-wire anemometer via the wire 28 within the hot-film measurement unit and the hot-film lead 38, continuing to heat the surface hot film. This, in turn, causes the voltage applied across the surface hot film to change. The hot-film lead 38 transmits this voltage signal to the test equipment, thereby obtaining the flow field conditions within the boundary layer. Further processing is used to obtain the boundary layer wall shear stress at the measured position on the suction surface of the turbine blade.

[0061] This invention combines the advantages and disadvantages of three measurement techniques to propose a high-precision boundary layer measurement method for high-load turbines. On one hand, the boundary layer probe's simple structure, high measurement accuracy, and low operating condition requirements enable steady-state boundary layer measurements. On the other hand, the hot-wire probe's small size, minimal flow field interference, short response time, and high temporal and spatial resolution enable transient boundary layer measurements. This method addresses the problem of surface hot-film measurement technology, which only measures boundary layer data at the blade endwall. A two-axis displacement control mechanism addresses the inefficiency of both boundary layer and hot-wire probes, which can only measure at intermittent points. The probe's endwall detection sensor addresses the problem of both probes being easily damaged by contact with the wall when in extreme contact. Furthermore, the surface hot-film measurement technology allows continuous measurement of boundary layer data at the endwall, and its high-frequency response, high synchronization, and minimal flow field perturbation address the inability of boundary layer and hot-wire probes to measure boundary layer data at the blade endwall, as well as the difficulty in accurately transmitting boundary layer flow signals in real time under high-speed blade rotation. The portions not described in detail in this invention are common knowledge in the art.

[0062] The above embodiments fully and effectively achieve the objectives of the present invention. Those skilled in the art will appreciate that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the above specific embodiments. Although the present invention has been described with reference to the embodiments currently considered to be the most practical and preferred, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A high-precision measurement device for high-load turbine boundary layer, characterized in that: include: Boundary layer probe, hot wire probe, surface hot film and two-axis displacement control mechanism; The two-axis displacement control mechanism is installed on the wind tunnel experimental equipment. The two-axis displacement control mechanism includes two degrees of freedom of movement of X-axis and Y-axis, including a flat base, a transverse motion mechanism, a longitudinal motion mechanism and a probe installation mechanism; the flat base is used to fix the displacement control mechanism and connect the experimental equipment; the transverse motion mechanism includes a transverse pulley, a transverse support platform, a transverse slide rail, a transverse screw rod and a transverse control unit; the transverse motion mechanism is arranged on the flat base, and the transverse control unit includes a transverse stepping motor, a transverse driver and a transverse controller, the transverse stepping motor drives the transverse screw rod to move through the transverse driver, and the other end of the transverse screw rod is rotatably supported on the transverse pulley, the transverse support platform is supported on the transverse screw rod through a screw nut, and the two ends of the transverse support platform are guided by transverse slide rails; in this way, the transverse control unit controls the movement of the probe along the axial direction of the blade together with the transverse pulley, the transverse slide rail and the transverse screw rod; the longitudinal motion mechanism includes a first support rib, a longitudinal pulley, a longitudinal slide rail, a second support rib, a longitudinal support The cam is provided with a longitudinal guide rail and a longitudinal control unit, and the cam is provided with a longitudinal guide rail, and the longitudinal guide rail is provided with a longitudinal guide rail. The cam is provided with a longitudinal guide rail, and the longitudinal guide rail is provided with a longitudinal guide rail. The cam is provided with a longitudinal guide rail, and the longitudinal guide rail is provided with a longitudinal guide rail. The cam is provided with a longitudinal guide rail, and the longitudinal guide rail is provided with a longitudinal guide rail. The cam is provided with a longitudinal guide rail, and the longitudinal guide rail is provided with a longitudinal guide rail. Among them, the boundary layer probe consists of a boundary layer probe, an intake pipe, an air bleed pipe, a support pipe and a boundary layer probe end wall detection sensor; the boundary layer probe is in the shape of a flat waist hole to facilitate the measurement of the thin boundary layer on the end wall; the intake pipe is connected to the boundary layer probe to guide the fluid entering the boundary layer probe; the support pipe is used to support and fix the intake pipe and the air bleed pipe, and the two ends are connected by soft rubber; the boundary layer probe end wall detection sensor is located at the tail of the boundary layer probe to monitor whether the boundary layer probe hits the end wall.

2. The high-precision measurement device for the high-load turbine boundary layer according to claim 1, characterized in that: The hot wire probe includes a metal wire, a hot wire fork rod, a hot wire probe, a connecting device, a hot wire body, a hot wire probe end wall detection sensing device cable, and a hot wire probe signal transmission cable; the metal wire is located between the hot wire fork rods; the hot wire fork rods are tapered and located on the hot wire probe; the hot wire probe has a circular through hole inside for leading the end wall detection sensing device cable and the signal transmission cable from the hot wire body to the hot wire fork rod; the connecting device is tapered and located on the hot wire body for connecting the hot wire probe; the hot wire body is used to fix and support the hot wire probe device, and at the same time, it is loaded with the end wall detection sensing device cable and the signal transmission cable; the hot wire probe end wall detection sensing device cable is used to transmit the wall collision information of the hot wire probe device to an external control device; The hot wire probe signal transmission cable is used to transmit the measured original signal to the external control device; The surface thermal film includes a thermal film measuring unit and a surface thermal film base plate. The thermal film measuring unit is arranged on the surface thermal film base plate. The thermal film measuring unit includes a wire and a temperature sensor. The two ends of the temperature sensor are connected with wires. The wires are used to transmit current and signals. The temperature sensor is used to collect the temperature difference caused by convective heat transfer.

3. The high-precision measurement device for the high-load turbine boundary layer according to claim 2, characterized in that: The hot wire probe needs to be temperature corrected before operation. The correction formula is: ,in is the temperature correction coefficient, is the output voltage at different heights from the metal wall when the airflow velocity is zero, is the output voltage at the center of the leaf when the air velocity is zero, and the parameter A 、 B 、 n Derived from the fitted curve of the calibrated wind tunnel.

4. The high-precision measurement device for the high-load turbine boundary layer according to claim 2, characterized in that: The end wall detection sensor is installed on the boundary layer probe and the hot wire probe. The circuit consists of a power supply, a switch, a voltmeter, an ammeter and an LED light. The power supply is a 3V DC power supply, and the switch is a push button switch. The two are connected in series with the LED light and the ammeter to form the main circuit. The voltmeter is connected in parallel with them. The line between the ammeter and the switch is disconnected, one end is connected to the hot wire probe, and the other end is connected to the end wall.

5. The measurement method of a high-load turbine boundary layer high-precision measurement device according to any one of claims 1 to 4, characterized in that: The following steps are involved: SS1, using a two-axis displacement control mechanism to control the boundary layer probe to perform steady-state measurements of the blade endwall proximal area and normal boundary layer; SS2, using a two-axis displacement control mechanism to control the hot wire probe to perform transient measurements on the blade endwall proximal area and normal boundary layer; SS3, transient measurement of the blade endwall boundary layer using a surface hot film; SS4, through boundary layer probe sweep measurement, obtains the fluid velocity along the wall normal at the blade cross section, and then obtains the time-averaged velocity distribution in the normal direction of the blade suction surface wall. By analyzing the velocity distribution, the changes in the suction surface boundary layer at each axial position in the blade channel are obtained; through hot wire probe sweep measurement, the pulsation curve of the fluid velocity in the boundary layer with time is obtained, and according to its transient velocity fluctuation, the boundary layer state and boundary layer separation and reattachment data are obtained; through the original signal obtained by surface hot film measurement, according to the positive peak and negative peak signal signs, the boundary layer transition interval data at the blade end wall is obtained.

6. The measurement method of a high-load turbine boundary layer high-precision measurement device according to claim 5, characterized in that: Step SS1 specifically includes: SS11, Install the experimental apparatus: First, install the two-axis displacement control mechanism on the experimental equipment and secure the boundary layer probe to the waist-shaped through-hole of the probe support platform using the probe holder. The grid plate is fixed to the bottom of the flat base, with the boundary layer probe facing the blade wall. SS12, determine the measurement position: start the end wall detection sensor on the boundary layer probe, and the external test system and the control unit of the two-axis displacement control mechanism cooperate to drive the probe movement; first, drive the boundary layer probe to move towards the blade wall at an extremely slow speed. When the LED light on the end wall detection sensor flashes and the voltmeter and ammeter show readings, the two-axis displacement control mechanism stops moving the probe and transmits the current position coordinates to the external test system for recording and use as the wall point. Then, drive the boundary layer probe slowly to the appropriate position in the blade circumferential direction, and transmit the current position coordinates to the external test system for recording and use as the normal end point; then the lateral displacement mechanism and the longitudinal displacement mechanism cooperate to repeat the above process, recording the wall point coordinates and the normal end point coordinates at multiple axial positions of the blade; SS13, Experimental Measurement: After determining the boundary layer measurement location, the fan is started to introduce airflow into the blade channel. The two-axis displacement control structure drives the boundary layer probe along the path set in the previous step. The data collected by the boundary layer probe is transmitted from the tail of the boundary layer to the measurement system via a lead. After further processing, steady-state data of the proximal region and normal boundary layer are obtained.

7. The measurement method of a high-load turbine boundary layer high-precision measurement device according to claim 6, characterized in that: Step SS2 specifically includes: SS21, Installing the Experimental Apparatus and Determining the Measurement Position: To obtain transient data on the incoming boundary layer at the midsection of the blade, follow the steps in SS11 to install the hot-wire probe at the appropriate waist-shaped through-hole position on the two-axis displacement control mechanism. The two-axis displacement control mechanism with the hot-wire probe is then loaded into the wind tunnel experimental apparatus. The measurement position of the hot-wire probe is then determined according to the steps in SS12. SS22, experimental measurement: Before the experimental measurement, the hot-wire probe needs to be temperature-corrected to ensure that the temperature of the hot-wire probe in the flow field is consistent with the temperature during calibration, thereby ensuring the accuracy of the measurement results. The hot-wire anemometer is then started, and the metal wire is heated to the preheating temperature with the help of the probe wire. After it stabilizes, the fan is started to introduce airflow into the blade channel. The boundary layer probe is driven to move along a pre-set path through the two-axis displacement control structure. At the same time, the temperature difference caused by the convective heat transfer of the airflow is monitored through the temperature sensor, and the temperature voltage signal is transmitted through the temperature sensor lead. The voltage signal is further transmitted to the external test equipment through the lead of the hot-wire probe for data processing, thereby obtaining transient data of the proximal region and the normal boundary layer.

8. The measurement method of a high-load turbine boundary layer high-precision measurement device according to claim 7, characterized in that: Step SS3 specifically includes: S31, Install the experimental device: Apply the surface thermal film to the suction side of the blade, 30 mm away from the blade tip and blade root. Connect the thermal film lead along the rotor blade surface to the grid plate, pass through the grid plate and connect to the external hot wire anemometer and test system; S32, Experimental Measurement: The motor and hot-wire anemometer are then started, rotating the rotor blades while heating the surface hot film to a stable temperature via the hot-film leads and the wires within the hot-film measurement unit. Immediately thereafter, the fan is started to introduce airflow into the blade channel. The temperature sensor monitors the temperature difference generated by the convective heat transfer of the airflow, and transmits the signal to the hot-wire anemometer via the wires within the hot-film measurement unit and the hot-film leads. This signal continues to heat the surface hot film, causing the voltage applied across the surface hot film to change. The hot-film leads transmit this voltage signal to the test equipment, thereby obtaining the flow field conditions within the boundary layer. Further processing yields the boundary layer wall shear stress at the measured position on the suction side of the turbine blade.

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