Multi-stage flow passage coordinated regulation system and method of carbon dioxide two-phase turbine

Abstract

The application provides a two-phase turbine multistage flow channel coordinated regulation system and method of carbon dioxide, belongs to the technical field of supercritical carbon dioxide cycle power generation, and can at least partially solve the problems that the existing turbine design cannot accurately characterize the non-equilibrium phase change phenomenon of carbon dioxide near the critical region and the strong coupling of gas-liquid two-phase flow, the actual turbine performance significantly deviates from the design expectation, the cycle efficiency is lost, the erosion damage of the blade is caused, the non-steady flow excitation force generated during variable load operation affects the operation safety of the rotor, the application comprises a turbine with three-stage gradient decompression flow channel design, a transcritical coupling monitoring module, a regulation module and an external processing module, the transcritical coupling monitoring module captures the critical density jump, the droplet distribution and the vibration signal in real time, provides data support for regulation, and the regulation module dynamically adjusts the flow channel based on the relaxation time, the erosion risk index and other parameters, so that wide load efficient and stable operation is realized.

Description

Technical Field

[0001] This invention belongs to the field of supercritical carbon dioxide cycle power generation technology, specifically relating to a multi-stage flow channel coordinated control system and method for a two-phase carbon dioxide turbine. Background Technology

[0002] Unlike traditional steam turbines, which rely on stable flow in a single gas phase or wet steam region, carbon dioxide two-phase turbines face the challenge of drastic density fluctuations coupled with phase transitions near the critical pressure. When the working fluid flows through the turbine blades, localized pressure drops can trigger a sudden transition from a supercritical state to a gas-liquid two-phase mixture, leading to interphase slip with large density differences in the flow field. This interphase flow necessitates turbine design that considers the dramatic changes in specific heat capacity of carbon dioxide near the critical pressure, achieving precise enthalpy drop distribution through a staged flow channel structure. The upstream section must withstand the drastic property changes near the critical region, while the downstream section must accommodate droplet entrainment and boundary layer separation in low-dryness two-phase flow.

[0003] Traditional turbine design methods based on ideal gas or pure gas / liquid phase assumptions can describe macroscopic flow parameters, but they cannot accurately characterize the strong non-idealities of carbon dioxide near the critical region, potential non-equilibrium phase transitions, and strong coupling effects between gas and liquid two-phase flows. This leads to a significant deviation of actual turbine performance from design expectations, resulting not only in cycle efficiency loss but also potential erosion damage to the blades from high-speed droplets. Furthermore, the unsteady flow excitation forces generated during variable load operation threaten the long-term operational safety of the rotor. To address these issues, we propose a multi-stage flow channel coordinated control system and method for carbon dioxide two-phase turbines. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a multi-stage flow channel coordinated control system and method for carbon dioxide two-phase turbines.

[0005] One aspect of the present invention provides a multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine, the system comprising: The turbine includes a three-stage gradient depressurization channel; A transcritical coupling monitoring module is disposed in the turbine to monitor in real time the property jumps, two-phase flow evolution, and vibrations caused by the two-phase flow evolution of carbon dioxide during transcritical expansion. The transcritical coupling monitoring module includes: a critical state property monitoring unit disposed in the first stage of the turbine to monitor in real time the density jump in the critical region and the temperature hysteresis caused by non-equilibrium phase transition; a droplet distribution tracking unit disposed in the second stage of the turbine to transmit droplet Sotel average diameter data in real time and monitor the liquid film thickness; and an aerodynamic vibration coupling unit disposed in the last stage of the turbine to monitor broadband vibrations caused by droplet impact and generate anti-phase excitation force. An adjustment module is disposed within the turbine flow channel for adjusting the turbine flow channel based on data from the transcritical coupling monitoring module; An external processing module is communicatively connected to the transcritical coupling monitoring module and the adjustment module, and regulates the adjustment module according to the data from the transcritical coupling monitoring module, so that the adjustment module can dynamically adjust the flow channel of the turbine.

[0006] Furthermore, the turbine includes a first-stage supercritical expansion section, the first-stage supercritical expansion section includes a stator blade disposed at the inlet of the first-stage supercritical expansion section, the stator blade includes an elliptical leading edge to improve adaptability to changes in the inlet angle of attack, and the stator blade includes rotatable blades to improve the range of variation of the flow area within the first-stage supercritical expansion section.

[0007] Furthermore, the turbine also includes a secondary two-phase transition section, which includes rotor blades rotatably disposed inside the secondary two-phase transition section, an axial cyclone separator integrated at the end of the secondary two-phase transition section, an axial sliding inner ring installed on the inner wall of the casing of the secondary two-phase transition section and capable of moving back and forth along the turbine axis, and adjustable guide vanes located downstream of the axial sliding inner ring and circumferentially arranged on the casing of the secondary two-phase transition section.

[0008] Specifically, the rotor blade includes a variable curvature leading edge integrally formed at the front end of the rotor blade to reduce droplet impact stress, a serrated trailing edge movably disposed at the rear end of the rotor blade to break large droplets, and a servo motor disposed on the rotor blade body to adjust the angle of the serrated trailing edge.

[0009] Specifically, the turbine further includes a final stage pure gas phase expansion section, which includes blades fixed in the circumferential groove of the rotor disk of the final stage pure gas phase expansion section and a diffuser disposed downstream of the blade outlet. The blades include swept blade tips disposed at the leading edge of the blades to suppress secondary flow losses.

[0010] Preferably, the critical state property monitoring unit includes a resonant density meter embedded in the stator throat of the first-stage supercritical expansion section for real-time capture of density jumps in the critical region, and a T-type thermocouple arranged in the Laval nozzle diffuser section of the first-stage supercritical expansion section for monitoring temperature hysteresis caused by non-equilibrium phase transition.

[0011] Specifically, the droplet distribution tracking unit includes a laser diffractometer integrated at the inlet of the cyclone separator in the secondary two-phase transition section for real-time output of the droplet Sotel average diameter, and a capacitive liquid film sensor circumferentially arranged at the drain hole in the casing wall of the secondary two-phase transition section for monitoring the liquid film thickness.

[0012] Furthermore, the aerodynamic vibration coupling unit includes a MEMS piezoelectric array embedded at the tip of the blade in the final stage pure gas phase expansion section to capture broadband vibrations caused by droplet impact, and an electromagnetic coil embedded at the tip of the blade to generate an anti-phase excitation force.

[0013] Furthermore, the adjustment module includes a movable wall surface symmetrically arranged at the throat of the stationary blade in the first-stage supercritical expansion section, a stepper motor connected to the guide vane of the axial cyclone separator in the second-stage two-phase transition section and used to adjust the guide vane installation angle of the axial cyclone separator, and an adjustable fish-scale plate assembly hinged to the inner wall of the diffuser inlet in the last-stage pure gas phase expansion section via a radial rotating shaft, wherein the movable wall surface is adjusted by an electro-hydraulic servo actuator arranged at the throat of the stationary blade.

[0014] Another aspect of the present invention provides a method for coordinated control of multi-stage flow channels in a two-phase carbon dioxide turbine. The method is implemented using the aforementioned coordinated control system for multi-stage flow channels in a two-phase carbon dioxide turbine, and the steps are as follows: S1: In the first-stage supercritical expansion section, the critical state property monitoring unit outputs density and temperature in real time. The external processing module calculates the density gradient and temperature gradient and calculates the relaxation time in real time through the real-time density data and real-time temperature data. When the relaxation time exceeds the limit, the corresponding width adjustment of the first-stage supercritical expansion section is triggered based on the phase transition type. S2: In the secondary two-phase transition section, the droplet distribution tracking unit calculates the average Sobel diameter of the droplets and outputs the liquid film thickness. The external processing module defines an erosion risk index based on the average Sobel diameter and liquid film thickness data. When the average Sobel diameter of the droplets exceeds the limit, the sawtooth angle is increased to enhance the droplet breaking effect. When the liquid film thickness exceeds the limit, the guide vane installation angle in the secondary two-phase transition section is increased to strengthen centrifugal separation. When the erosion risk index exceeds the limit, the coordinated adjustment of the sawtooth angle and the guide vane installation angle is initiated. S3: In the final stage pure gas phase expansion section, the vibration main frequency is identified by the aerodynamic vibration coupling unit, and a vibration mode database is established. The external processing module obtains the corresponding droplet size by querying the database. When the characteristic frequency is detected, the electromagnetic coil of the aerodynamic vibration coupling unit applies a counter-phase force to suppress the vibration, and at the same time increases the area of ​​the diffuser throat of the final stage pure gas phase expansion section to reduce the airflow velocity.

[0015] The beneficial effects of this invention are as follows: The transcritical coupling monitoring module captures critical density jumps, droplet distribution, and vibration signals in real time, providing data support for regulation. The regulation module dynamically adjusts the flow channel based on parameters such as relaxation time and erosion risk index to achieve efficient and stable operation under wide loads. Through multi-stage gradient depressurization flow channel design and coordinated regulation, the flow loss, wear, and vibration problems induced by the phase change of carbon dioxide two-phase turbines are effectively solved. The first stage adopts rotatable nozzle blades and elliptical leading-edge airfoils, which reduce flow loss in the supercritical region and improve load adaptability by continuously adjusting the flow area and adapting to changes in the angle of attack. The second stage combines a variable curvature leading edge and a serrated trailing edge with an axial vortex separator to suppress droplet erosion and secondary flow. The swept-back blade tip of the last stage is combined with a variable throat diffuser to improve aerodynamic efficiency. Attached Figure Description

[0016] Figure 1 This is a control logic diagram of a multi-stage flow channel coordinated control method for a carbon dioxide two-phase turbine according to a specific embodiment of the present invention. Figure 2 This is a flowchart illustrating the steps of a multi-stage flow channel coordinated control method for a carbon dioxide two-phase turbine according to a specific embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine provided in this specific embodiment of the invention includes: The turbine includes a three-stage gradient depressurization channel; A transcritical coupling monitoring module is installed in the turbine to monitor in real time the property jumps, two-phase flow evolution, and vibrations caused by the two-phase flow evolution of carbon dioxide during transcritical expansion. The system includes: a critical state property monitoring unit installed in the first stage of the turbine to monitor in real time the density jump in the critical region and the temperature hysteresis caused by non-equilibrium phase change; a droplet distribution tracking unit installed in the second stage of the turbine to transmit the Sothel average diameter data of droplets in real time and monitor the liquid film thickness; and an aerodynamic vibration coupling unit installed in the last stage of the turbine to monitor the broadband vibrations caused by droplet impact and generate anti-phase excitation force. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine also includes an adjustment module, which is set inside the turbine flow channel to adjust the turbine flow channel based on data from the transcritical coupling monitoring module; and an external processing module, which is communicatively connected to the transcritical coupling monitoring module and the adjustment module and controls the adjustment module based on data from the transcritical coupling monitoring module, so that the adjustment module can dynamically adjust the turbine flow channel.

[0019] Specifically, the transcritical expansion process described above refers to the phase transition of carbon dioxide working fluid from a supercritical to a subcritical state in a turbine, while simultaneously, high-temperature, high-pressure CO2 is depressurized and accelerated in the turbine flow channel, converting thermal energy into mechanical energy. The working fluid within the turbine undergoes the following progression: supercritical → critical point → two-phase flow → pure gas phase. The pressure of the carbon dioxide working fluid decreases gradually along the flow channel, and the temperature drops sharply, accompanied by the release / absorption of latent heat of phase change. The aforementioned property jumps include density jumps, specific heat jumps, and viscosity jumps.

[0020] Based on the above basic implementation method, in a specific embodiment, the turbine includes a first-stage supercritical expansion section, the first-stage supercritical expansion section includes a stator blade disposed at the inlet of the first-stage supercritical expansion section, the stator blade includes an elliptical leading edge large-head arc profile to improve adaptability to changes in the inlet angle of attack, and the stator blade includes rotatable blades to improve the range of variation of the flow area within the first-stage supercritical expansion section.

[0021] Specifically, the stator blade's leading edge (inlet edge) adopts an elliptical shape, with a relatively thick overall blade cross-section ("big head"). The transition between the pressure and suction surfaces uses a large arc. The elliptical leading edge can more smoothly guide the incoming flow from different directions, reducing the risk of flow separation. The big head and arc profile provide greater structural strength and rigidity, better able to withstand the high pressure and potential impact loads of supercritical carbon dioxide, while maintaining good aerodynamic performance under off-design conditions. The stator blade constitutes a Laval nozzle. The specific configuration of the rotatable stator blade in the turbine is as follows: the blade root is mounted in a bearing housing on the stator support ring (nozzle ring), allowing the blade to rotate around its own axis while bearing the load of the high-pressure fluid. A precision high-pressure rotary seal is installed where the blade root shaft passes through the stator support ring to prevent high-pressure working fluid from leaking to the outside of the turbine or the actuator chamber.

[0022] In one specific embodiment, the turbine further includes a secondary two-phase transition section, which includes rotor blades rotatably disposed inside the secondary two-phase transition section, an axial cyclone separator integrated at the end of the secondary two-phase transition section, an axial sliding inner ring mounted on the inner wall of the casing of the secondary two-phase transition section and movable back and forth along the turbine axis, and adjustable guide vanes located downstream of the axial sliding inner ring and circumferentially arranged on the casing of the secondary two-phase transition section.

[0023] In this embodiment, the radius of curvature of the leading edge of the blade varies along the blade height (e.g., the curvature is large at the root and small at the tip), forming a smoothly transitioning irregular leading edge. The trailing edge of the blade is designed with a continuous serrated structure (similar to a "comb" shape).

[0024] Furthermore, the leading and trailing edges of this blade shape function as follows: Reduce droplet impact stress: By optimizing the droplet impact angle and local velocity distribution, impact energy is dispersed, reducing the risk of blade leading edge erosion.

[0025] Actively breaking up large droplets: Utilizing the eddy shear force generated by the sawtooth structure, the unevaporated residual large droplets are torn into smaller droplets.

[0026] Suppressing secondary droplet erosion: Small droplets are more likely to follow the airflow, reducing impact erosion on downstream blades.

[0027] The axial cyclone separator consists of a ring channel formed by circumferentially distributed spiral guide vanes. The angle of the guide vanes forces the airflow to generate a high-speed cyclone. The centrifugal force generated by the cyclone throws the denser droplets toward the outer casing wall. The separated liquid working fluid is discharged through the drain hole on the casing wall (the capacitive liquid film sensor monitors this point), ensuring that the working fluid entering the final stage is close to the pure gas phase.

[0028] In this embodiment, the axially sliding inner ring is installed on the inner wall of the secondary transition section casing and can move back and forth along the turbine axis. Adjustable guide vanes are located downstream of the sliding inner ring and are circumferentially arranged on the casing (alternating with the rotating blades). The displacement of the axially sliding inner ring adjusts the radial clearance between the blade tip and the casing, controlling the flow cross-sectional area. The adjustable guide vanes are used to adjust the airflow exit angle to optimize the angle of attack of the downstream blades and avoid flow separation. In low-load wet steam conditions, reducing the guide vane angle and flow channel height can increase the flow velocity and suppress droplet deposition on the wall. Optimizing the angle of attack reduces flow separation on the blade surface and lowers the probability of droplet impact, thus achieving a dual effect of preventing droplet erosion in the wet steam region.

[0029] In another specific embodiment, the rotor blade includes a variable curvature leading edge integrally formed at the front end of the rotor blade to reduce the impact stress of the droplets, a serrated trailing edge movably disposed at the rear end of the rotor blade to break large droplets, and a servo motor disposed on the rotor blade body to adjust the angle of the serrated trailing edge. The servo motor drives the serrated angle of the trailing edge of the rotor blade. When the serrated angle is increased, the droplet breaking effect of the rotor blade can be enhanced.

[0030] In one specific embodiment, the turbine further includes a final-stage pure gas phase expansion section, which includes blades fixed in the circumferential grooves of the rotor disk of the final-stage pure gas phase expansion section, and a diffuser disposed downstream of the blade outlet. The blades include swept-back blade tips disposed at the leading edge of the blades to suppress secondary flow losses. The swept-back blade tip, i.e., the top region of the blade, is bent backward along the airflow direction (similar to the sweep angle of an airfoil), and the blade tip profile forms a non-perpendicular angle with the radial direction. This reduces the channel vortex intensity by weakening the lateral pressure gradient at the endwall; at the same time, it reduces mixing losses by reducing the interaction between the tip leakage flow and the mainstream.

[0031] Furthermore, the blades are fixed to the circumferential grooves of the final-stage rotor disk via fir-shaped blade roots or dovetail-shaped tenons. An intermediate blade root platform is set between the blade body and the disk to isolate thermal stress and seal the radial gap. The blade body is optimized based on B-spline control points, that is, the three-dimensional profile from the blade's mid-diameter to the root is defined by B-spline curves. The coordinates of the control points are adjusted by aerodynamic optimization algorithms to accurately control the curvature distribution of the pressure / suction surface profile, delay boundary layer separation, optimize the supersonic expansion wave system, reduce shock wave losses, and match the radial load distribution to reduce end losses in order to maximize aerodynamic efficiency.

[0032] In another specific embodiment, the critical state property monitoring unit includes a resonant density meter embedded in the stator throat of the first-stage supercritical expansion section for real-time capture of density jumps in the critical region, and a T-type thermocouple arranged in the Laval nozzle diffuser section of the first-stage supercritical expansion section for monitoring temperature hysteresis caused by non-equilibrium phase transition.

[0033] Furthermore, in this embodiment, the critical state property monitoring unit also includes a droplet distribution tracking unit, which includes a laser diffractometer integrated at the inlet of the cyclone separator in the secondary two-phase transition section for real-time output of the droplet Sotel average diameter, and a capacitive liquid film sensor circumferentially arranged at the drain hole of the casing wall in the secondary two-phase transition section for monitoring the liquid film thickness.

[0034] Furthermore, in this embodiment, the critical state property monitoring unit also includes an aerodynamic vibration coupling unit. The aerodynamic vibration coupling unit includes a MEMS piezoelectric array embedded in the blade tip of the final stage pure gas phase expansion section to capture broadband vibrations caused by droplet impact, and an electromagnetic coil embedded in the blade tip to generate an anti-phase excitation force. The MEMS piezoelectric array is a miniaturized, arrayed functional device formed by combining piezoelectric materials with microelectromechanical systems (MEMS) technology. It utilizes the force-electric coupling characteristics of piezoelectric materials (applying voltage generates deformation / applying force generates voltage).

[0035] Specifically, the Sothel mean diameter (SMD) is used to characterize the average particle size of the droplet swarm. The laser diffractometer is based on the Fraunhofer diffraction principle. The droplets scatter laser light to form an angular distribution spectrum. The laser beam (wavelength 632 nm) of the particle size analyzer penetrates the two-phase flow. The detector receives the intensity distribution of the scattered light and calculates the droplet particle size distribution through Mie scattering theory.

[0036] In one specific embodiment, the adjustment module includes a movable wall symmetrically arranged at the throat of the stator blade in the first-stage supercritical expansion section, a stepper motor connected to the guide vane of the axial cyclone separator in the second-stage two-phase transition section and used to adjust the installation angle of the guide vane of the axial cyclone separator, and an adjustable fish-scale plate assembly on a ceramic bearing seat hinged to the inner wall of the diffuser inlet in the last-stage pure gas phase expansion section via a radial rotating shaft, wherein the movable wall is adjusted by an electro-hydraulic servo actuator arranged at the throat of the stator blade.

[0037] Furthermore, the adjustable fish scales are circumferentially arranged arc-shaped thin plates that cover the throat area of ​​the diffuser and are hinged to the diffuser wall via a rotating shaft. A high-temperature flexible sealing sheet is used at the rotating shaft of the fish scales to prevent working fluid leakage. The adjustable fish scales are connected by a circumferential linkage ring and driven by an electro-hydraulic servo actuator. The circumferential linkage ring is a ring mechanism that connects all the rotating shafts of the fish scales to achieve synchronous adjustment. The electro-hydraulic servo actuator pushes the linkage ring to move axially.

[0038] Furthermore, under low pressure ratio conditions, the throat area of ​​the diffuser is reduced, the throat velocity of the diffuser is increased, airflow separation is avoided, the boundary layer kinetic energy of the diffuser wall is enhanced, and diffuser stall (flow separation leads to surge risk) is suppressed. Under high pressure ratio conditions, the throat area of ​​the diffuser is increased, the throat velocity of the diffuser is reduced, shock wave loss is avoided, the design expansion ratio is matched, supersonic shock wave loss is reduced, and high efficiency is maintained.

[0039] In another embodiment, the present invention also provides a method for coordinated control of multi-stage flow channels in a carbon dioxide two-phase turbine. The method is implemented using the aforementioned coordinated control system for multi-stage flow channels in a carbon dioxide two-phase turbine, and the steps are as follows: S1: In the first-stage supercritical expansion section, the critical state property monitoring unit outputs density and temperature in real time. The external processing module calculates the density gradient and temperature gradient and calculates the relaxation time in real time through the real-time density data and real-time temperature data. When the relaxation time exceeds the limit, the corresponding width adjustment of the first-stage supercritical expansion section is triggered based on the phase transition type. S2: In the secondary two-phase transition section, the droplet distribution tracking unit calculates the average Sobel diameter of the droplets and outputs the liquid film thickness. The external processing module defines the erosion risk index based on the average Sobel diameter of the droplets and the liquid film thickness data. When the average Sobel diameter of the droplets exceeds the limit, the sawtooth angle is increased to enhance the droplet breaking effect. When the liquid film thickness exceeds the limit, the guide vane installation angle in the secondary two-phase transition section is increased to strengthen centrifugal separation. When the erosion risk index exceeds the limit, the coordinated adjustment of the sawtooth angle and the guide vane installation angle is initiated. S3: In the final stage of pure gas phase expansion, the vibration main frequency is identified by the aerodynamic vibration coupling unit, and a vibration mode database is established. The external processing module obtains the corresponding droplet size by querying the database. When the characteristic frequency is detected, the electromagnetic coil of the aerodynamic vibration coupling unit applies a counter-phase force to suppress the vibration. At the same time, the area of ​​the diffuser throat in the final stage of pure gas phase expansion is increased to reduce the airflow velocity.

[0040] Furthermore, when a sharp negative change in gradient density or a sharp positive change in temperature gradient is detected, the phase transition type is condensation hysteresis. The fluid in the turbine is supercooled and does not condense, resulting in a falsely high fluid density. When a sharp positive change in gradient density or a sharp negative change in temperature gradient is detected, the phase transition type is evaporation hysteresis. The fluid in the turbine is superheated and does not evaporate, resulting in a falsely low density. Relaxation time represents the time required for a supercritical fluid to recover from a non-equilibrium state to local thermodynamic equilibrium. When the fluid expansion rate exceeds the molecular collision rate, the relaxation time increases, leading to phase transition hysteresis. After the phase transition, there are the aforementioned condensation hysteresis and evaporation hysteresis. When condensation hysteresis occurs, the area of ​​the variable throat of the diffuser is increased to reduce the working fluid flow rate in the turbine, thereby allowing the supercooled CO2 to release latent heat for a longer period of time, thus promoting condensation equilibrium and reducing the relaxation time. When evaporation hysteresis occurs, the area of ​​the variable throat of the diffuser is decreased to increase the working fluid flow rate in the turbine, thereby allowing the superheated CO2 to quickly cross the phase transition energy barrier, thus triggering flash evaporation and reducing the relaxation time.

[0041] To aid in a better understanding of the present invention, a more comprehensive and specific embodiment is described, in which one aspect of the present invention provides a multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine, the system comprising: The turbine; the turbine includes a three-stage gradient depressurization channel; A transcritical coupling monitoring module is installed in the turbine to monitor in real time the property jumps, two-phase flow evolution, and vibrations caused by the two-phase flow evolution of carbon dioxide during transcritical expansion. The system includes: a critical state property monitoring unit installed in the first stage of the turbine to monitor in real time the density jump in the critical region and the temperature hysteresis caused by non-equilibrium phase change; a droplet distribution tracking unit installed in the second stage of the turbine to transmit the Sothel average diameter data of droplets in real time and monitor the liquid film thickness; and an aerodynamic vibration coupling unit installed in the last stage of the turbine to monitor the broadband vibrations caused by droplet impact and generate anti-phase excitation force. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine also includes an adjustment module, which is set inside the turbine flow channel to adjust the turbine flow channel based on data from the transcritical coupling monitoring module; and an external processing module, which is communicatively connected to the transcritical coupling monitoring module and the adjustment module and controls the adjustment module based on data from the transcritical coupling monitoring module, so that the adjustment module can dynamically adjust the turbine flow channel.

[0042] In this embodiment, the turbine includes a first-stage supercritical expansion section, a second-stage two-phase transition section, and a final-stage pure gas phase expansion section. The first-stage supercritical expansion section includes a stationary blade disposed at the inlet of the first-stage supercritical expansion section. The stationary blade includes an elliptical leading edge with a large-head arc profile to improve adaptability to changes in the inlet angle of attack. The stationary blade includes rotatable blades to increase the range of variation in the flow area within the first-stage supercritical expansion section. The second-stage two-phase transition section includes rotor blades rotatably disposed inside the second-stage two-phase transition section, an axial cyclone separator integrated at the end of the second-stage two-phase transition section, and an axial cyclone separator mounted on the inner wall of the casing of the second-stage two-phase transition section and movable back and forth along the turbine axis. The rotor blades include a sliding inner ring and adjustable guide vanes located downstream of the axial sliding inner ring and circumferentially arranged on the secondary two-phase transition section casing; the rotor blades include a variable curvature leading edge integrally formed at the front end of the rotor blades to reduce droplet impact stress, a serrated trailing edge movably disposed at the rear end of the rotor blades to break large droplets, and a servo motor disposed on the rotor blade body to adjust the angle of the serrated trailing edge; the final stage pure gas phase expansion section includes blades fixed in the circumferential groove of the rotor disk of the final stage pure gas phase expansion section, and a diffuser disposed downstream of the blade outlet, the blades including swept-back blade tips disposed at the front end of the blades to suppress secondary flow losses.

[0043] Furthermore, the critical state property monitoring unit includes a resonant density meter embedded in the throat of the first-stage supercritical expansion section to capture the density jump in the critical region in real time, and a T-type thermocouple arranged in the Laval nozzle diffusion section of the first-stage supercritical expansion section to monitor the temperature hysteresis caused by non-equilibrium phase transition; the droplet distribution tracking unit includes a laser diffractometer integrated at the inlet of the cyclone separator in the secondary two-phase transition section to output the Sothel average diameter of the droplets in real time, and a capacitive liquid film sensor circumferentially arranged at the drain hole of the casing wall in the secondary two-phase transition section to monitor the liquid film thickness; the aerodynamic vibration coupling unit includes a device embedded in the end... The blade tip of the first-stage pure gas phase expansion section is equipped with a MEMS piezoelectric array for capturing broadband vibrations caused by droplet impact, and an electromagnetic coil embedded in the blade tip to generate a reverse excitation force; the adjustment module includes a movable wall symmetrically arranged in the throat of the first-stage supercritical expansion section, a stepper motor connected to the guide vane of the axial cyclone separator in the second-stage two-phase transition section and used to adjust the guide vane installation angle of the axial cyclone separator, and an adjustable fish scale assembly on a ceramic bearing seat hinged to the inner wall of the diffuser inlet of the last-stage pure gas phase expansion section via a radial rotating shaft, wherein the movable wall is adjusted by an electro-hydraulic servo actuator arranged in the throat of the stator.

[0044] In this embodiment, the following is combined with Figures 1 to 2 In another aspect, the present invention provides a method for coordinated control of multi-stage flow channels in a two-phase carbon dioxide turbine. This method is implemented using the aforementioned coordinated control system for multi-stage flow channels in a two-phase carbon dioxide turbine, and the steps are as follows: S1: In the first-stage supercritical expansion section, the resonant density meter outputs density in real time, the T-type thermocouple outputs temperature in real time, and the external processing module calculates density gradient and temperature gradient and calculates relaxation time in real time through real-time density data and real-time temperature data. When the relaxation time exceeds the limit, the corresponding width adjustment of the stationary blade throat is triggered based on the phase change type. S2: In the secondary two-phase transition section, the average diameter of the droplets in Sobel is calculated by a laser diffractometer, and the liquid film thickness is output by a capacitive liquid film sensor. The external processing module defines an erosion risk index based on the average diameter of the droplets in Sobel and the liquid film thickness data. When the average diameter of the droplets in Sobel exceeds the limit, the sawtooth angle is increased to enhance the droplet breaking effect. When the liquid film thickness exceeds the limit, the guide vane installation angle of the axial cyclone separator is increased to strengthen centrifugal separation. When the erosion risk index exceeds the limit, the coordinated adjustment of the sawtooth angle and the guide vane installation angle is initiated. S3: In the final stage of pure gas phase expansion, the vibration main frequency is identified by the MEMS piezoelectric array, and a vibration mode database is established. The external processing module obtains the corresponding droplet size by querying the database. When the characteristic frequency is detected, the electromagnetic coil applies a reverse force to suppress the vibration. At the same time, the area of ​​the diffuser throat in the final stage of pure gas phase expansion is increased to reduce the airflow velocity.

[0045] In summary, the embodiments disclosed herein have at least the following technical effects: Real-time monitoring and control improve efficiency and stability: Mechanism: The system is equipped with a transcritical coupling monitoring module, which can monitor in real time the physical property jumps (such as density, specific heat, and viscosity) of carbon dioxide during transcritical expansion within the turbine, the evolution of the two-phase flow regime, and the resulting vibrations. The external processing module dynamically adjusts the regulating module based on the monitoring data, enabling the turbine flow channel to adapt to changes in operating conditions.

[0046] Results: By promptly identifying and addressing issues such as phase transition hysteresis, droplet erosion, and vibration, the efficiency of converting thermal energy into mechanical energy was optimized, enhancing the stability of turbine operation.

[0047] Promote phase transition equilibrium and reduce relaxation time: Mechanism: The critical state property monitoring unit (resonant density meter and T-type thermocouple) monitors the density and temperature of the first-stage supercritical expansion section in real time, and the external processing module calculates the relaxation time (the time it takes for the fluid to recover from a non-equilibrium state to thermodynamic equilibrium). When the relaxation time exceeds the limit, the working fluid flow rate is controlled by adjusting the width of the stator throat.

[0048] Effects: When condensation lags (supercooled and not condensing), the throat area is expanded to reduce the flow rate and promote the release of latent heat; when evaporation lags (superheated and not evaporating), the throat area is reduced to increase the flow rate and trigger flash evaporation. This dynamic regulation effectively reduces relaxation time and improves thermodynamic efficiency.

[0049] Reduce droplet erosion and protect the blades: Mechanism: The droplet distribution tracking unit (laser diffractometer and capacitive liquid film sensor) monitors the Souter mean diameter of droplets and the thickness of the liquid film in the secondary two-phase transition section. The adjustment module enhances the droplet breakup effect by increasing the serrated trailing edge angle of the rotor blades and strengthens centrifugal separation by adjusting the guide vane installation angle of the axial cyclone separator.

[0050] Effects: It breaks up large droplets and throws them against the casing wall for discharge, reducing the impact and erosion of the blades by the droplets, extending the service life of the blades, and reducing the risk of erosion in the wet steam zone.

[0051] Suppress vibration and reduce losses: Mechanism: The aerodynamic vibration coupling unit (MEMS piezoelectric array and electromagnetic coil) monitors the broadband vibration caused by droplet impact in the final pure gas phase expansion section and applies an anti-phase excitation force to suppress the vibration. At the same time, the airflow velocity is reduced by adjusting the area of ​​the diffuser throat.

[0052] Effects: Effectively suppresses vibration, reduces aerodynamic losses and mechanical fatigue, improves turbine operation stability, and reduces energy loss.

[0053] Optimize structural design to improve performance: First-stage supercritical expansion section: Design: The stationary blades adopt an elliptical leading edge large-head arc profile and rotatable blades.

[0054] Effects: Improves adaptability to changes in the angle of attack of the inlet, reduces the risk of flow separation, enhances structural strength, and optimizes aerodynamic performance.

[0055] Secondary two-phase transition section: Design: The rotor blades are equipped with a variable curvature leading edge and a serrated trailing edge, combined with an axial cyclone separator and adjustable guide vanes.

[0056] Effects: Reduces droplet impact stress, breaks up large droplets and separates liquid working fluid, optimizes airflow angle of attack, and reduces erosion and flow loss.

[0057] Final stage pure gas phase expansion section: Design: The blades adopt a swept-back blade tip, and the diffuser is adjustable.

[0058] Effects: Suppresses secondary flow losses, reduces mixing and shock wave losses, and improves aerodynamic efficiency.

[0059] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine, characterized in that, The system includes: The turbine includes a three-stage gradient pressure-reducing flow path. The turbine includes a first-stage supercritical expansion section, which includes stator blades disposed at its inlet. These stator blades have elliptical leading edges to improve adaptability to changes in the inlet angle of attack and rotatable blades to increase the range of flow area variation within the first-stage supercritical expansion section. The turbine also includes a second-stage two-phase transition section, which includes rotor blades rotatably disposed within the second-stage two-phase transition section and integrated at its end. The turbine includes an axial cyclone separator, an axially sliding inner ring mounted on the inner wall of the casing of the secondary two-phase transition section and capable of moving back and forth along the turbine axis, and adjustable guide vanes located downstream of the axially sliding inner ring and circumferentially arranged on the casing of the secondary two-phase transition section; the turbine also includes a final stage pure gas phase expansion section, which includes blades fixed in the circumferential groove of the rotor disk of the final stage pure gas phase expansion section, and a diffuser disposed downstream of the blade outlet, wherein the blades include swept-back blade tips disposed at the leading edge of the blades to suppress secondary flow losses. A transcritical coupling monitoring module, disposed within the turbine, is used to monitor in real time the property jumps, two-phase flow evolution, and vibrations caused by the two-phase flow evolution of carbon dioxide during transcritical expansion within the turbine. The transcritical coupling monitoring module includes: a critical state property monitoring unit disposed in the first stage of the turbine for real-time monitoring of density jumps in the critical region and monitoring temperature hysteresis caused by non-equilibrium phase transitions; a droplet distribution tracking unit disposed in the second stage of the turbine for real-time transmission of droplet Sothel average diameter data and monitoring of liquid film thickness; and an aerodynamic vibration coupling unit disposed in the last stage of the turbine for monitoring broadband vibrations induced by droplet impacts and generating anti-phase excitation forces. The aerodynamic vibration coupling unit includes a MEMS piezoelectric array embedded in the blade tip of the last-stage pure gas phase expansion section for capturing broadband vibrations induced by droplet impacts, and an electromagnetic coil embedded in the blade tip to generate anti-phase excitation forces. An adjustment module is disposed within the turbine flow channel for adjusting the turbine flow channel based on data from the transcritical coupling monitoring module; An external processing module is communicatively connected to the transcritical coupling monitoring module and the adjustment module, and regulates the adjustment module according to the data from the transcritical coupling monitoring module, so that the adjustment module can dynamically adjust the flow channel of the turbine.

2. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine according to claim 1, characterized in that, The rotor blade includes a variable curvature leading edge integrally formed at the front end of the rotor blade to reduce droplet impact stress, a serrated trailing edge movably disposed at the rear end of the rotor blade to break large droplets, and a servo motor disposed on the rotor blade body to adjust the angle of the serrated trailing edge.

3. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine according to claim 1, characterized in that, The critical state property monitoring unit includes a resonant density meter embedded in the throat of the first-stage supercritical expansion section for real-time capture of density jumps in the critical region, and a T-type thermocouple arranged in the Laval nozzle diffuser section of the first-stage supercritical expansion section for monitoring temperature hysteresis caused by non-equilibrium phase transition.

4. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine according to claim 1, characterized in that, The droplet distribution tracking unit includes a laser diffractometer integrated at the inlet of the cyclone separator in the secondary two-phase transition section for real-time output of the droplet Sotel average diameter, and a capacitive liquid film sensor circumferentially arranged at the drain hole in the casing wall of the secondary two-phase transition section for monitoring the liquid film thickness.

5. The multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine according to any one of claims 1 to 4, characterized in that, The adjustment module includes a movable wall symmetrically arranged at the throat of the stationary blade in the first-stage supercritical expansion section, a stepper motor connected to the guide vane of the axial cyclone separator in the second-stage two-phase transition section and used to adjust the guide vane installation angle of the axial cyclone separator, and an adjustable fish-scale plate assembly hinged to the inner wall of the diffuser inlet in the last-stage pure gas phase expansion section via a radial rotating shaft. The movable wall is adjusted by an electro-hydraulic servo actuator arranged at the throat of the stationary blade.

6. A method for coordinated control of multi-stage flow channels in a carbon dioxide two-phase turbine, characterized in that, The method is implemented using a multi-stage flow channel coordinated control system for a carbon dioxide two-phase turbine according to any one of claims 1 to 5, and the steps are as follows: S1: In the first-stage supercritical expansion section, the critical state property monitoring unit outputs density and temperature in real time. The external processing module calculates the density gradient and temperature gradient and calculates the relaxation time in real time through the real-time density data and real-time temperature data. When the relaxation time exceeds the limit, the corresponding width adjustment of the first-stage supercritical expansion section is triggered based on the phase transition type. S2: In the secondary two-phase transition section, the droplet distribution tracking unit calculates the average Sobel diameter of the droplets and outputs the liquid film thickness. The external processing module defines an erosion risk index based on the average Sobel diameter and liquid film thickness data. When the average Sobel diameter of the droplets exceeds the limit, the sawtooth angle is increased to enhance the droplet breaking effect. When the liquid film thickness exceeds the limit, the guide vane installation angle in the secondary two-phase transition section is increased to strengthen centrifugal separation. When the erosion risk index exceeds the limit, the coordinated adjustment of the sawtooth angle and the guide vane installation angle is initiated. S3: In the final stage pure gas phase expansion section, the vibration main frequency is identified by the aerodynamic vibration coupling unit, and a vibration mode database is established. The external processing module obtains the corresponding droplet size by querying the database. When the characteristic frequency is detected, the electromagnetic coil of the aerodynamic vibration coupling unit applies a counter-phase force to suppress the vibration, and at the same time increases the area of ​​the diffuser throat of the final stage pure gas phase expansion section to reduce the airflow velocity.

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