Unshrouded turbine startup method and system based on bleed air pre-whirl tuning

Abstract

The application relates to the technical field of jet starting control, and discloses a guide vane-free turbine starting method and system based on air pre-rotation tuning, which comprises the following steps: acquiring the instantaneous tangential velocity of airflow at multiple circumferential positions of the annular section of a pre-rotation cavity, and forming a circumferential airflow velocity distribution; calculating the airflow distribution uniformity based on the distribution; when the uniformity is insufficient, identifying at least one circumferential angle interval with a speed lower than the current circumferential average speed as a local low-speed area; starting the corresponding compensation nozzle for the identified low-speed area, injecting compensation airflow into the pre-rotation cavity, and forming an optimized airflow field with a uniform circumferential distribution; and finally, using the optimized airflow field to smoothly drive the turbine rotor to accelerate to the ignition rotating speed. The method and system disclosed by the application realize active sensing and closed-loop tuning of the airflow field of the pre-rotation cavity, and effectively improve the smoothness, efficiency and reliability of the starting process.

Description

Technical Field

[0001] This invention relates to the field of jet start-up control technology, and in particular to a method and system for starting a bladeless turbine based on bleed air pre-swirl tuning. Background Technology

[0002] Bleed air pre-swirl tuning is an important starting method for bladeless turbines in aero-engines. It drives the turbine rotor to accelerate by providing pre-swirling airflow to reach the ignition speed. Bladeless turbines, by eliminating the guide vane structure, help reduce weight, simplify the structure, and improve response speed, making them an important research direction for improving the overall performance and reliability of engines. However, in practical applications, the circumferential distribution of airflow within the pre-swirl chamber is non-uniform. This non-uniformity is not due to design flaws, but rather to a combination of complex factors, including dynamic differences in upstream multi-stage bleed air parameters, asymmetry in pipeline layout, and inherent disturbances in the flow process. The direct consequence is that the driving torque experienced by the turbine rotor during startup is inconsistent in the circumferential direction, resulting in periodic torque fluctuations. This not only reduces energy transfer efficiency and prolongs startup time, but more seriously, it can induce rotor vibration, affecting ignition stability, and even leading to startup failure in extreme cases. This has become a key bottleneck restricting the widespread application of this technology in high-performance, high-reliability engines. Summary of the Invention

[0003] Therefore, the purpose of this invention is to overcome the problems of large driving torque fluctuations, low energy transfer efficiency, and poor start-up stability caused by uneven circumferential distribution of airflow in the pre-swirl chamber during the start-up of a guide vaneless turbine in the prior art. It provides a method and system for starting a guide vaneless turbine based on induced draft pre-swirl tuning, which actively identifies and compensates for local low-speed airflow regions in the pre-swirl chamber, and realizes closed-loop tuning of the airflow field, thereby effectively improving the stability, efficiency, and reliability of the start-up process.

[0004] In a first aspect, to solve the above-mentioned technical problems, the present invention provides a method for starting a bladeless turbine based on bleed air pre-swirl tuning, comprising:

[0005] Obtain the circumferential airflow velocity distribution at the inlet of the pre-swirl chamber; the circumferential airflow velocity distribution is the instantaneous tangential velocity of the airflow at multiple positions along the circumferential direction at the annular cross section of the inlet;

[0006] Calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution;

[0007] Based on the uniformity of airflow distribution, at least one circumferential angle interval in which the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber is identified as a local low-speed region.

[0008] For the local low-speed region, the compensation nozzles configured corresponding to the circumferential angle range are activated, and compensation airflow is injected into the pre-swirl chamber through the compensation nozzles to obtain an optimized airflow field with uniform circumferential distribution.

[0009] The turbine rotor is pre-rotated by the optimized airflow field.

[0010] Preferably, the injection direction of the compensating nozzle is configured to be downstream of the airflow in the local low-speed region, and the injection axis of the compensating nozzle forms an angle θ with the tangent direction of the pre-swirl cavity at the installation position of the compensating nozzle; wherein, the angle θ is an acute angle.

[0011] Preferably, the included angle θ satisfies: 15°≤θ≤60°.

[0012] Preferably, the total temperature of the compensating airflow is higher than the total temperature of the airflow in the local low-speed region, and after compensation, the total temperature T of the airflow at the location of the local low-speed region before entering the turbine rotor satisfies the following relationship:

[0013] T ref <T≤1.1×T ref ;

[0014] Among them, T ref This represents the spatial average total temperature of the airflow at the inlet of the pre-swirl chamber.

[0015] Preferably, the compensating airflow is based on pulsed injection; and the frequency of the pulsed injection is controlled to be synchronized with an integer multiple of the current rotational frequency of the turbine rotor.

[0016] Preferably, calculating the airflow distribution uniformity based on the circumferential airflow velocity distribution includes: calculating the current circumferential average velocity based on the instantaneous tangential velocities of the airflow at the plurality of locations; calculating the instantaneous deviation between the instantaneous tangential velocity of the airflow at each location and the current circumferential average velocity; integrating the instantaneous deviation values ​​at all locations at the same moment to obtain an instantaneous spatial integral value; and performing a time-domain average on the sequence of the instantaneous spatial integral values ​​changing over time to obtain the airflow distribution uniformity.

[0017] Preferably, identifying the local low-speed region includes: generating a region scanning signal in response to the airflow distribution uniformity being less than a uniformity threshold; dividing the circumference of the pre-swirl cavity inlet into multiple scanning units in response to the region scanning signal; for each scanning unit, counting the number of measurement points where the instantaneous tangential velocity of the airflow is lower than the current circumferential average velocity, and calculating the ratio of the number of measurement points to the total number of velocity measurement points in the scanning unit; identifying scanning units whose ratio exceeds a ratio threshold as candidate low-speed units; recording the starting angle and ending angle of the candidate low-speed units; sorting all the candidate low-speed units by angle, merging candidate low-speed units with adjacent angles or intervals less than an angle tolerance into a continuous circumferential angle interval, and outputting it as the local low-speed region.

[0018] Preferably, during the process of pre-spinning the turbine rotor by optimizing the airflow field, the method further includes: monitoring the driving torque signal of the turbine rotor during the monitoring period after injecting the compensating airflow into the local low-speed region, and calculating the torque fluctuation value during the monitoring period; and adjusting the injection angle of the compensating nozzle and / or the temperature of the compensating airflow according to the torque fluctuation value.

[0019] Preferably, adjusting the injection angle of the compensating nozzle and / or the temperature of the compensating airflow based on the torque fluctuation value includes: comparing the torque fluctuation value with a fluctuation threshold one and a fluctuation threshold two, wherein the fluctuation threshold two is greater than the fluctuation threshold one; if the torque fluctuation value is less than or equal to the fluctuation threshold one, then the injection angle and the temperature of the compensating airflow are not adjusted; if the torque fluctuation value is greater than the fluctuation threshold one and less than or equal to the fluctuation threshold two, then the injection angle is reduced by an angle adjustment amount one based on the current value, and / or the temperature of the compensating airflow is increased by a temperature adjustment amount one based on the current value; if the torque fluctuation value is greater than the fluctuation threshold two, then the injection angle is reduced by an angle adjustment amount two based on the current value, and / or the temperature of the compensating airflow is increased by a temperature adjustment amount two based on the current value; wherein the absolute value of the angle adjustment amount two is greater than the absolute value of the angle adjustment amount one, and the temperature adjustment amount two is greater than the temperature adjustment amount one.

[0020] Secondly, to solve the above-mentioned technical problems, the present invention provides a bladeless turbine starting system based on bleed air pre-swirl tuning, comprising:

[0021] A sensor array, configured at the inlet of the pre-swirl chamber, is used to collect the instantaneous tangential velocity of the airflow at multiple locations along the circumferential direction to obtain the circumferential airflow velocity distribution;

[0022] The data processing module is used to calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution; and to identify at least one circumferential angle interval where the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber, based on the airflow distribution uniformity, as a local low-speed region.

[0023] A compensation nozzle, configured to correspond to the identified circumferential angle range, is used to inject compensation airflow into the pre-swirl chamber;

[0024] The control execution module, in response to the data processing module's identification of the local low-speed region, activates the corresponding compensation nozzle to inject compensation airflow to obtain a uniformly circumferentially distributed optimized airflow field within the pre-swirl chamber; the optimized airflow field is used to drive the turbine rotor to accelerate to the ignition speed.

[0025] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0026] The bladeless turbine starting method and system based on bleed air pre-swirl tuning described in this invention actively identifies and compensates for low-speed regions of local airflow within the pre-swirl chamber. It dynamically and proactively corrects the circumferential non-uniformity of airflow distribution within the pre-swirl chamber caused by factors such as upstream bleed air differences, pipeline asymmetry, and flow disturbances, thereby providing a significantly optimized circumferential driving flow field at the source. This optimized flow field acts on the turbine rotor, making the driving torque on each blade in the rotor's circumferential direction tend to be consistent, effectively suppressing periodic torque fluctuations and the resulting rotor vibration, and improving the smoothness and inherent safety of the starting acceleration process. Simultaneously, the uniform flow field ensures efficient utilization of limited bleed air energy by the blades, reduces local flow losses, and improves the overall efficiency of energy conversion to rotor kinetic energy, thus helping to shorten the time to reach ignition speed.

[0027] More importantly, the closed-loop tuning mechanism itself has adaptive characteristics, which can respond to different engine operating conditions and environmental changes, continuously compensate for flow field distortion caused by component aging or state drift, and effectively enhance the robustness and reliability of the starting system under complex conditions. Attached Figure Description

[0028] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0029] Figure 1 This is a flowchart of a bladeless turbine start-up method based on bleed air pre-swirl tuning in a preferred embodiment of the present invention;

[0030] Figure 2 This is a flowchart of obtaining airflow distribution uniformity in a preferred embodiment of the present invention;

[0031] Figure 3 This is a flowchart illustrating the identification of local low-speed regions in a preferred embodiment of the present invention;

[0032] Figure 4 This is a flowchart illustrating the adjustment of compensation parameters based on torque fluctuation values ​​in a preferred embodiment of the present invention.

[0033] Figure 5 This is a structural block diagram of a bladeless turbine starting system based on bleed air pre-swirl tuning in a preferred embodiment of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0035] When implementing the guide vaneless turbine start-up method based on induced draft pre-swirl tuning, the core problem is: how to sense and correct the inherent circumferential airflow non-uniformity in the pre-swirl chamber in real time without introducing complex mechanical structures such as guide vanes, so as to suppress turbine torque fluctuations and improve start-up stability and efficiency.

[0036] The purpose of this invention is to overcome the problems of large fluctuations in driving torque, low energy transfer efficiency, and poor starting stability caused by uneven circumferential distribution of airflow in the pre-swirl chamber during the start-up of a guide vane-less turbine in the prior art.

[0037] Example 1: Refer to Figure 1 As shown, this embodiment of the invention discloses a method for starting a bladeless turbine based on bleed air pre-swirl tuning, comprising:

[0038] S100. Obtain the circumferential airflow velocity distribution at the inlet of the pre-swirl chamber; the circumferential airflow velocity distribution is the instantaneous tangential velocity of the airflow at multiple positions along the circumferential direction at the annular cross section of the inlet.

[0039] S200. Calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution;

[0040] S300. Based on the uniformity of airflow distribution, identify at least one circumferential angle interval where the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber as a local low-speed region.

[0041] S400: For local low-speed areas, activate the compensation nozzles configured corresponding to the circumferential angle range, and inject compensation airflow into the pre-swirl chamber through the compensation nozzles to obtain an optimized airflow field with uniform circumferential distribution.

[0042] The S500 pre-spins the turbine rotor by optimizing the airflow field.

[0043] In the specific scenario of implementing step S100, the circumferential airflow velocity distribution specifically refers to the instantaneous tangential velocity of the airflow collected at N measurement positions (e.g., N=24 or 36) uniformly arranged along the circumferential direction at the annular cross-section of the pre-swirl chamber inlet. During implementation, one of the following two methods can be used:

[0044] Direct measurement: N high-temperature resistant, high-frequency response optical velocity sensors, such as laser Doppler velocimeter probes, are embedded in the inner wall of the casing at the inlet section of the pre-spinning cavity. These optical velocity sensors directly measure the tangential velocity component at their location and transmit it to the controller via a data bus.

[0045] Indirect calculation: Considering the harsh inlet environment, N miniature dynamic pressure sensors can be embedded circumferentially within the annular flow channel in the stable section upstream of the pre-swirl chamber inlet. These sensors measure the dynamic pressure pulsations of the airflow and convert the pressure pulsation signal into a tangential velocity pulsation signal at the inlet section of the pre-swirl chamber using a pre-calibrated transfer function. This transfer function establishes the unsteady flow relationship from the upstream measurement point to the downstream target section through fluid dynamics simulation or bench experiments. Subsequently, the converted velocity pulsation signal is filtered and reconstructed to obtain the instantaneous tangential velocity of the airflow.

[0046] Step S200 aims to convert the instantaneous tangential velocity of the airflow into a quantitative indicator that can characterize the uniformity of the airflow. Specifically, the implementation is as follows:

[0047] First, calculate the circumferential average velocity at the current time t, which is the arithmetic mean of the instantaneous tangential velocities of the airflow at all N measurement locations. Then, calculate the instantaneous deviation at each measurement location, with a value of max(0, instantaneous tangential velocity - circumferential average velocity), ensuring that only regions with velocities lower than the circumferential average velocity are considered. Next, perform a circumferential integration on the instantaneous deviations at the N measurement locations to obtain the instantaneous spatial integral value characterizing the total overall low-velocity deficit at the current time. Finally, perform a time-domain average on the time-series signal of the instantaneous spatial integral value (e.g., using a moving average with a window length of 0.1 seconds) to obtain the smoothed airflow distribution uniformity; the smaller the airflow distribution uniformity value, the more uniform the airflow distribution.

[0048] In the specific scenario of implementing step S300, when the airflow distribution uniformity index is lower than a preset uniformity threshold, it is determined that the current flow field non-uniformity has exceeded the standard, triggering the low-speed region scanning and identification process; the identification process is as follows:

[0049] First, divide the entire circumference into M consecutive scanning units, for example, one unit every 10°, M=36.

[0050] Next, for each scanning unit, the number of measurement points covered by the unit where the instantaneous tangential velocity of the airflow is consistently lower than the circumferential average velocity is counted. If the proportion of measurement points meeting the above conditions in a scanning unit exceeds a preset threshold (e.g., 70%), the scanning unit is identified as a candidate low-speed unit, and its starting and ending angles are recorded.

[0051] Finally, all candidate low-speed units are sorted by angle, and units with adjacent angles or intervals less than a preset tolerance angle (e.g., 5°) are merged to form one or more continuous circumferential angle intervals. Each interval is defined as a local low-speed region. At the same time, the average circumferential width W of the local low-speed region is calculated. Here, the average circumferential width W is calculated based on the termination angle minus the starting angle. It refers to the measure of the angle covered by the identified local low-speed region along the circumferential direction, describing how many radians of the circumference the local low-speed region occupies.

[0052] In the specific scenario of implementing step S400, for each identified local low-speed region, the following compensation action is performed:

[0053] Activate one or more compensation nozzles configured spatially corresponding to the circumferential angle range.

[0054] The injection direction of the compensating nozzle is configured to face downstream of the airflow in the local low-speed region, and the injection axis of the compensating nozzle forms an angle θ with the tangent direction of the pre-swirl cavity at its installation position. The angle θ is dynamically adjusted according to the average circumferential width W of the local low-speed region; a smaller angle θ (e.g., 20°) is used for narrower regions to enhance penetration, while a larger angle θ (e.g., 45°) is used for wider regions to achieve broader coverage. Simultaneously, the total temperature of the compensating airflow is controlled to be higher than that of the airflow in the local low-speed region, and the total temperature T of the compensated airflow before entering the turbine rotor satisfies T0. ref <T≤1.1×T ref (T) ref The average total temperature at the inlet of the pre-swirl chamber is set to take advantage of the thermal expansion effect. Finally, a compensated airflow with the aforementioned set angle θ and total temperature is injected into the pre-swirl chamber through a compensated nozzle.

[0055] After compensation in step S400, a uniformly distributed optimized airflow field is formed in the pre-swirl chamber. This optimized airflow field impacts the turbine rotor blades with a consistent tangential velocity, generating a stable and efficient driving torque that drives the turbine rotor to accelerate to the engine ignition speed, thus completing the start-up process.

[0056] The present invention provides a bladeless turbine starting method based on bleed air pre-swirl tuning. This method actively identifies and compensates for low-speed regions of localized airflow within the pre-swirl chamber, dynamically and proactively correcting the circumferential non-uniformity of airflow distribution within the pre-swirl chamber caused by factors such as upstream bleed air differences, pipeline asymmetry, and flow disturbances. This provides a significantly optimized circumferentially distributed driving flow field at the source. This optimized flow field acts on the turbine rotor, making the driving torque on each blade in the rotor's circumferential direction more consistent, effectively suppressing periodic torque fluctuations and the resulting rotor vibration, thus improving the smoothness and inherent safety of the starting acceleration process. Simultaneously, the uniform flow field ensures efficient utilization of limited bleed air energy by the blades, reducing localized flow losses and improving the overall efficiency of energy conversion to rotor kinetic energy, thereby helping to shorten the time to reach ignition speed.

[0057] More importantly, the closed-loop tuning mechanism itself has adaptive characteristics, which can respond to different engine operating conditions and environmental changes, continuously compensate for flow field distortion caused by component aging or state drift, and effectively enhance the robustness and reliability of the starting system under complex conditions.

[0058] In the above scheme, if the compensating airflow is injected in a direction perpendicular to the main airflow (radial) or in the opposite direction when implementing airflow compensation, serious problems will occur: First, the momentum of the compensating airflow cannot be efficiently converted into the circumferential momentum required to drive the turbine to rotate. Most of the energy is dissipated in ineffective radial impacts and vortices, resulting in extremely low compensation efficiency. Second, such violent lateral or reverse impacts will seriously interfere with or even destroy the existing main swirling flow structure in the pre-swirl chamber, which may induce new flow instability, pressure pulsation, or even separation vortices. This will not only fail to homogenize the flow field but will also exacerbate flow field turbulence and torque fluctuations.

[0059] To address this issue, after identifying the local low-speed region, the average flow direction of the airflow within that region, i.e., the dominant flow direction angle, is first determined. Specifically, this involves acquiring the instantaneous tangential velocity vectors of the airflow at all measurement points within the local low-speed region and calculating the direction of their vector synthesis. This dominant flow direction angle defines the downstream direction of the airflow within the local low-speed region.

[0060] The compensating nozzles are fixedly mounted on the casing wall of the pre-swirl chamber, with their installation positions corresponding to potential low-speed regions. The mechanical structure of each compensating nozzle is pre-configured such that its injection axis can be adjusted within a small range of angles within an adjustment plane, which typically includes the circumferential tangent direction of the pre-swirl chamber at the installation position. When compensation is initiated for a specific localized low-speed region, the control unit drives the compensating nozzle to ensure its injection axis meets two conditions:

[0061] Condition 1: The injection axis of the compensating nozzle is adjusted to face downstream of the dominant flow direction angle in the local low-speed region; this ensures that the compensating airflow is injected downstream, rather than upstream or transversely. The injection axis facing downstream of the dominant flow direction angle in the local low-speed region allows the compensating airflow to shear and mix with the main airflow most smoothly, effectively adding its own momentum to the circumferential momentum of the main airflow, avoiding momentum cancellation and energy loss due to directional conflict.

[0062] Condition 2: The injection axis of the compensating nozzle forms an acute angle θ with the circumferential tangent direction of the pre-swirl chamber passing through the installation position of the compensating nozzle.

[0063] The circumferential tangential direction represents the ideal direction of the pre-swirling airflow and is also the most effective direction for driving the turbine. When the included angle θ is acute, the velocity vector of the compensating airflow can be decomposed into two components: a larger circumferential component (along the tangential direction) and a smaller radial component (pointing towards the cavity center or outer wall). The circumferential component directly contributes to increasing the circumferential velocity of the local airflow and is the primary purpose of compensation. Although the radial component does not directly do work, it plays a crucial role: it gives the compensating airflow a certain penetration depth, allowing it to penetrate deep into the flow field and effectively mix with the airflow in the core low-speed region, rather than merely skimming the wall. Simultaneously, the shearing effect of this radial component with the mainstream circumferential velocity induces a beneficial vortex with the same rotation direction as the main swirling flow. This vortex acts like a miniature stirrer, accelerating the momentum exchange between high- and low-speed airflows and expanding the range of influence of the compensation effect.

[0064] In the preferred design, the included angle θ satisfies the following conditions: 15° ≤ θ ≤ 60°; ideally, it should be 20° ≤ θ ≤ 45°. The smaller the included angle θ, the larger the radial velocity component of the compensating airflow, and the smaller the circumferential (tangential) velocity component. If the included angle θ is too small, for example, <15°, the compensating airflow will become overly radial, with most of its momentum used for penetration and radial mixing, while the circumferential momentum contribution, crucial for directly driving turbine rotation, will decrease sharply, contradicting the fundamental purpose of pre-swirl drive. Simultaneously, the near-radial strong jet will directly impact the inner wall of the pre-swirl cavity or violently interfere with the outer wall, easily inducing large-scale flow separation and strong vortices, severely damaging the stability of the main swirling flow, and increasing unnecessary pressure loss and noise. Therefore, the lower limit of the included angle θ is above 15° to ensure that the compensating airflow possesses a dominant circumferential momentum component, enabling its energy to be efficiently converted into driving torque and minimizing destructive interference with the main flow.

[0065] The larger the angle θ, the closer the direction of the compensating airflow is to the pure circumferential direction. If the angle θ is too large, for example, >60°, its radial penetration will be severely insufficient. In this case, the compensating airflow can only flow close to the cavity wall or within a very thin surface layer, passing over the low-speed region without penetrating its core. For narrow and deep velocity defects, this compensation is almost ineffective, failing to truly deliver energy to the most needed low-speed core region. Furthermore, when the angle θ is close to 90° (pure tangential), the compensating airflow is almost parallel to the main airflow, lacking an effective velocity direction difference between the two, resulting in weak shear mixing, slow momentum transfer, and sluggish compensation response. Therefore, the upper limit of the angle θ is below 60° to ensure that the compensating airflow has sufficient radial penetration to penetrate deep into the flow field, substantially interact with the low-speed airflow, and achieve effective mixing and momentum transfer.

[0066] In the above scheme, airflow compensation is implemented for local low-speed areas. When implementing compensation, if the local speed is increased by only relying on the injection of compensation air flow (flow rate and velocity), there are inherent bottlenecks in its effect: First, a large compensation air flow rate is often required to achieve a significant momentum increase, which may affect the stability of the main air intake system or be limited by the air supply capacity; Second, the simple momentum mixing process has energy dissipation, and the efficiency is difficult to further improve.

[0067] To address this problem, the present invention further implements total temperature control for the compensating airflow, with the specific implementation steps as follows:

[0068] Determining the reference total temperature: Multiple total temperature sensors are evenly arranged on the annular cross-section of the pre-swirl chamber inlet to measure the total temperature of the airflow at each circumferential position. The spatial average of all total temperature measurements is then calculated to obtain the spatial average total temperature of the airflow at the pre-swirl chamber inlet. This spatial average total temperature is used as the reference value for the entire temperature control process. The total temperature sensors can be arranged independently of the velocity sensors, or a composite probe can be used.

[0069] Calculate the expected total temperature after compensation: Based on the average velocity deficit value of the local low-speed region, the expected total temperature that the local low-speed region should reach after compensation is calculated using a preset temperature-velocity compensation model.

[0070] It should be noted here that the arithmetic mean of the difference between the instantaneous tangential velocity of the airflow at all velocity measurement points and the current circumferential average velocity at the inlet of the pre-swirl chamber (i.e., the "deficit") in a identified local low-speed region is defined as the average velocity deficit of the local low-speed region.

[0071] Total temperature is a thermodynamic state parameter characterizing the energy of airflow. It is also called stagnation temperature. It refers to the temperature reached when an airflow is completely blocked to zero velocity under adiabatic (no heat exchange) and frictionless (isentropic) conditions.

[0072] The desired total temperature refers to the total temperature that the airflow in a currently identified local low-speed region with a specific average velocity deficit is expected to reach before entering the turbine rotor to do work, after ideal compensation.

[0073] The temperature-velocity compensation model here establishes the physical relationship between velocity deficit and required temperature rise; one feasible implementation is as follows:

[0074] ;

[0075] T represents the desired total temperature, which is the total temperature of the airflow at the location of the local low-speed region before entering the turbine rotor, after compensation; T ref The space-averaged total temperature of the airflow at the inlet of the pre-swirl chamber is represented; k represents the temperature compensation coefficient, with a value of 0.1~0.5, which comprehensively characterizes the overall efficiency and system characteristics of the process of converting thermal energy (by increasing the total temperature) into kinetic energy (increasing velocity) to compensate for the velocity deficit; ΔV represents the average velocity deficit value; V avg This represents the current circumferential average velocity.

[0076] The constraint of the temperature-velocity compensation model is to ensure that the calculation results satisfy: T ref <T≤1.1×T ref .

[0077] The control unit sets the desired total temperature T as the thermodynamic calibration target for this compensation, adjusts the compensation airflow to the set total temperature, and injects it.

[0078] To achieve the desired total temperature T after compensation, the compensation airflow needs to be heated to a higher set total temperature. The set total temperature needs to take into account the heat loss and incomplete mixing during the mixing process between the compensation airflow and the mainstream in the low-speed zone. It is usually calculated by another preset mixing heat transfer model and must satisfy the condition that the set total temperature is greater than the target total temperature.

[0079] The heating process is implemented through an independently controllable heating device, which can be:

[0080] Electric heater: Installed in the compensating airflow branch, it heats up quickly by adjusting the power.

[0081] Heat exchanger: It uses high-temperature gas from the engine (such as dilution gas drawn from the combustion chamber or between turbine stages) to heat the compensating airflow, and controls the temperature by adjusting the high-temperature gas flow rate or heat exchange area.

[0082] Micro combustion chamber: The fuel and air are catalytically combusted upstream of the compensation nozzle to directly generate high-temperature compensation gas.

[0083] The heating device is controlled in a closed loop by a temperature controller. The temperature controller receives the set value and reads the actual temperature fed back by the fast-response temperature sensor installed upstream of the compensating nozzle. It dynamically adjusts the heating power or heat source flow rate through a PID algorithm to make the actual temperature accurately and stably stabilize at the set value.

[0084] The present invention, in its embodiments, firstly utilizes the physical principle of gas expansion and acceleration due to heat. When a compensating gas flow with a temperature higher than the surrounding environment is injected into a local low-speed region and mixed with it, the total temperature of the locally mixed gas increases. According to gas dynamics, under the same pressure environment, its static temperature increases and its density decreases, thereby leading to an increase in flow velocity. This method of directly converting thermal energy into kinetic energy provides an additional velocity increment for compensating the local low-speed region, and its efficiency is higher than that of the method relying on external jet flow to push the flow. Secondly, the total temperature after compensation is precisely controlled to meet T... ref <T ≤ 1.10× T ref This optimized narrow window ensures that the compensation action is effective and safe.

[0085] When continuous compensation airflow injection is used, its effect is essentially to increase the average flow velocity in the entire local low-speed region. However, the turbine drive torque fluctuations caused by circumferential airflow unevenness often contain periodic components at the same frequency as the turbine rotor rotation or at integer multiples thereof (harmonics); these periodic torque fluctuations are the main excitation source causing synchronous rotor vibration. Although continuous compensation can improve the mean, it has limited effect on suppressing these periodic fluctuation components of specific frequencies.

[0086] To address the aforementioned problems, this embodiment of the invention changes the injection method of the compensating airflow from continuous to controlled pulse injection, and actively synchronizes its pulse frequency with the rotor rotation. The specific implementation steps are as follows:

[0087] The current rotational frequency f of the turbine rotor is obtained by directly measuring it through a speed sensor mounted on the turbine rotor shaft and reading the signal from the bus of the engine's full authority digital electronic controller.

[0088] The base frequency f0 of the pulse injection is set to satisfy f0 = m × f, where m is a positive integer (1, 2, 3...). Typically, m is 1 (synchronization) or 2 (frequency multiplication). The control unit calculates and locks the base frequency f0 based on the current rotational frequency f. For example, if f is 100Hz (corresponding to 6000 rpm), when m = 1, f0 is synchronized to 100Hz; this means that 100 compensation pulses are injected per second, with each pulse corresponding to one rotor rotation.

[0089] The core of pulse jet control lies not only in frequency synchronization but also in phase matching. The system needs to ensure that the moment the compensating airflow pulse arrives at the turbine blade plane is strictly aligned with the moment when the blade experiences a trough of periodic aerodynamic torque due to uneven flow field (the moment when it needs the most boost) or when it needs to counteract specific harmonic torques.

[0090] First, by analyzing the driving torque fluctuation signal or based on flow field simulation, the phase angle Φ of the torque fluctuation component to be canceled relative to the rotor position (such as the moment when a reference blade reaches its apex) is determined.

[0091] The control unit calculates a complete timing chain, including: the moment the pulse command is issued → the delay Δt1 in the transmission of the compensating airflow through the pipeline to the compensating nozzle → the flight time Δt2 of the airflow from the compensating nozzle to the turbine blade plane. The trigger phase Φ1 of the pulse command must satisfy: Φ1 = Φ - 2π × f0 × (Δt1 + Δt2); where Δt1 and Δt2 are obtained through a preset fluid dynamics model or experimental calibration.

[0092] Based on the rotor angle signal, when the angle reaches Φ1, the control unit sends an opening command to the high-speed pulse valve of the compensating nozzle to execute a brief, high-flow injection, forming a compensating airflow pulse.

[0093] The duration and intensity of a single pulse are determined based on the severity of the local low-velocity region and the amplitude of the torque fluctuations that need to be counteracted. Typically, the pulse width is extremely short, but the peak flow rate is much higher than the average flow rate during continuous injection to provide a high-intensity momentum increment instantaneously.

[0094] In this embodiment of the invention, pulsed injection achieves frequency locking, ensuring that the release rhythm of compensating energy is perfectly synchronized with rotor rotation and its harmonics. Furthermore, by introducing precise phase control, the timing of this synchronized energy release is precisely targeted at the weakest point (trough) in the periodic fluctuations of the turbine blade aerodynamic torque or at specific harmonic components that need to be canceled. This allows each compensating pulse to directly act on a specific periodic excitation term in the rotor dynamics equations. As a result, the compensation system no longer merely passively improves the average flow field but actively counteracts the main excitation sources of rotor vibration. Ultimately, this results in superior torque fluctuation suppression with lower average compensating airflow consumption, particularly with an immediate effect on suppressing speed-related synchronous vibrations.

[0095] In the above embodiments, the uniformity of airflow distribution is obtained. After acquiring a large amount of instantaneous tangential airflow velocity using a pre-swirl cavity inlet velocity sensor array, a core problem arises: how to quickly, stably, and reliably extract a single index that can objectively and quantitatively characterize the uniformity of the entire circumferential airflow from this set of instantaneous velocity data that fluctuates drastically over time and is spatially complex. Simple statistics (such as the difference between the maximum and minimum values) are sensitive to noise and cannot reflect the overall pattern; while directly calculating the standard deviation of all points can reflect the dispersion, it treats high-speed and low-speed points equally, and its value is greatly affected by the overall acceleration / deceleration trend, failing to focus on reflecting the low-speed bottleneck problem.

[0096] To address the aforementioned issues, this embodiment further provides a step-by-step, focused, and robust method for calculating airflow distribution uniformity, referring to... Figure 2 As shown, the specific implementation includes the following sequential steps:

[0097] At each sampling time t, the instantaneous tangential velocity of the airflow at N measurement positions along the circumference is acquired, and the arithmetic mean of these instantaneous tangential velocities is calculated to obtain the current circumferential average velocity. The current circumferential average velocity represents the average tangential momentum level of the airflow across the entire inlet section at that time, and will be used as the benchmark for subsequent comparisons.

[0098] For each measurement location, the difference between the instantaneous tangential velocity of the airflow and the current circumferential average velocity is calculated, i.e., the instantaneous deviation value.

[0099] The instantaneous deviation values ​​at all N measurement locations at the same time t are integrated circumferentially. Since the measurement points are uniformly and discretely distributed on the circumference, this integration is simplified in practice to summing all instantaneous deviation values ​​and then multiplying them by a constant factor related to the angular interval—the instantaneous spatial integral value. The instantaneous spatial integral value represents the total velocity deficit relative to the average velocity at all low-velocity points on the entire pre-swirl cavity inlet circumference at the current time t. The larger the instantaneous spatial integral value, the more severe the overall airflow inhomogeneity.

[0100] The instantaneous spatial integral value obtained in the above steps is a signal that fluctuates rapidly over time, containing real changes in flow field inhomogeneity, measurement noise, and high-frequency jitter caused by turbulent fluctuations. To obtain a stable index that can be used for reliable threshold judgment, the instantaneous spatial integral value needs to be smoothed. This embodiment uses a time-domain averaging method, specifically applying a moving average filter to the time series of the instantaneous spatial integral value. A time window length T1 is set (e.g., T1 = 0.1 seconds). At each time t, the average value of the instantaneous spatial integral value within the past time window T1 is calculated; this average value is the airflow distribution uniformity index.

[0101] The method for determining the airflow distribution uniformity index in this embodiment of the invention uses real-time calculation of dynamic average speed as a benchmark, making the evaluation standard adaptive to engine operating conditions and avoiding the failure problem of a fixed threshold under varying operating conditions. By extracting only the negative velocity deviation, the evaluation focus is locked on the root cause of torque fluctuations—the local low-speed bottleneck. This makes the calculated uniformity index highly physically correlated with the degree of unevenness of the actual driving torque borne by the turbine rotor. An increase in the distribution uniformity index directly corresponds to the risk of failure or performance degradation. Furthermore, by first spatially integrating the negative deviation, an instantaneous spatial integral value representing the instantaneous total deficit is obtained. This step transforms the complex spatial distribution problem into an intuitive scalar problem. Then, the airflow distribution uniformity is obtained by time-domain averaging of the instantaneous spatial integral value, which cleverly filters out the unavoidable random noise and high-frequency pulsations in the signal, resulting in a stable, reliable, and interference-resistant control variable.

[0102] After obtaining the airflow distribution uniformity index and determining the flow field non-uniformity, how can we accurately and automatically locate the spatial range (start and end angles) of local low-speed regions on the circumference? Due to noise in sensor measurements and turbulent fluctuations in the airflow itself, the boundaries of local low-speed regions may be blurred and isolated low-speed points may exist. The following problems exist when actually identifying local areas: 1) Region fragmentation: A physically continuous low-speed region may be misjudged as multiple discontinuous small regions due to instantaneous velocity fluctuations at a few points; 2) Large boundary error: Inaccurate determination of the start and end angles of the region leads to misalignment between the effective range of subsequent compensation nozzles and the actual problem area, reducing compensation efficiency and even causing interference.

[0103] To address this problem, embodiments of the present invention provide an identification method based on scanning units and merging rules, referring to... Figure 3 As shown, the specific steps are as follows:

[0104] When the calculated airflow distribution uniformity index is less than the preset uniformity threshold, the control unit determines that the current airflow distribution non-uniformity has exceeded the permissible range and generates a region scan trigger signal, which initiates the identification process of local low-speed regions.

[0105] In response to the region scan trigger signal, the entire circumference (360°) of the pre-rotation cavity inlet is logically divided into M consecutive scanning units, each covering a fixed angular range (e.g., M=36 if each unit is 10°). Based on a preset mapping relationship, the specific set of velocity measurement points contained in each scanning unit is determined. For example, if 72 measurement points are uniformly arranged along the circumference, then each 10° scanning unit contains an average of 2 measurement points.

[0106] For each defined scan unit, perform the following operations:

[0107] a. Read the instantaneous tangential velocity of the airflow at all mapped measurement points within the scanning unit, and compare the instantaneous tangential velocity of the airflow at each measurement point with the current circumferential average velocity at the same moment.

[0108] b. Count the number of measurement points within the scanning unit where the instantaneous tangential velocity of the airflow is consistently lower than the current circumferential average velocity, and denote it as Nlow.

[0109] c. Calculate the low-speed point ratio R, i.e., R = Nlow / Ntotal, where Ntotal is the total number of measurement points within the scanning unit.

[0110] d. Compare the calculated ratio R with a preset ratio threshold Rth (e.g., Rth = 0.6 or 60%). If R ≥ Rth, the low-speed phenomenon within the scanning cell is determined to be widespread and stable, and the scanning cell is marked as a candidate low-speed cell. Simultaneously, record the starting angle θs (cell start boundary) and ending angle θe (cell end boundary) of the candidate low-speed cell.

[0111] After determining all scanned units, further processing is performed on all marked candidate low-speed units:

[0112] Sort all candidate low-speed units in ascending order according to their recorded starting angle θs.

[0113] Check two adjacent candidate low-speed cells in sequence; let the termination angle of the previous scan cell be θe1 ​​and the starting angle of the next cell be θs2, and calculate the angle interval between them Δθ=θs2-θe1.

[0114] If Δθ ≤ the preset angle tolerance θtol (e.g., θtol = 5°), then the two candidate low-speed units are considered to be physically connected or close and should belong to the same low-speed region; the system merges the two units, with the starting angle of the new region being θs1 of the first unit and the ending angle being θe2 of the second unit; this merging process is iterated until there are no adjacent units that meet the merging conditions.

[0115] Each consecutive circumferential angle interval formed after merging is ultimately determined as a local low-speed region, and its boundary angle information is output.

[0116] By using scanning units rather than individual measurement points as the basic judgment unit and introducing a proportional threshold Rth, false alarms caused by instantaneous velocity fluctuations at isolated points are effectively filtered out. Only when most measurement points within a unit exhibit low velocity are the area considered problematic, thus improving the reliability of identification.

[0117] Angular tolerance merging addresses the issue of fragmented identification of physically continuous regions caused by measurement gaps, boundary point velocity fluctuations, or element division. By merging closely spaced candidate elements, the true physical contours of low-velocity regions can be more accurately reconstructed, avoiding the generation of too many fragmented areas.

[0118] After the implementation of the feedforward-based compensation strategy, its actual effect may deviate from the expectation due to dynamic changes in engine operating conditions, uncertainties in complex flow within the pre-swirl chamber, and drifts in the characteristics of the compensation system itself (such as nozzle flow characteristics and heating efficiency).

[0119] To address the aforementioned problems, embodiments of the present invention introduce a feedback tuning process based on the driving effect after compensation execution, referring to... Figure 4 As shown, the specific implementation steps are as follows:

[0120] After completing a compensation airflow injection action for a specific local low-speed area, the system enters a preset monitoring period. During this monitoring period, the system continuously collects the driving torque signal generated by the turbine rotor under the optimized airflow field through a torque sensor installed on the turbine rotor shaft.

[0121] After the monitoring period ends, the acquired driving torque signal is processed. First, high-frequency noise in the signal is filtered out. Then, the standard deviation of the driving torque signal during the monitoring period, or its peak-to-peak value, is calculated. This calculated value is defined as the torque fluctuation value after this compensation action. The torque fluctuation value characterizes the smoothness of the turbine rotor drive process under this compensation action; the smaller the torque fluctuation value, the more stable the torque.

[0122] Within the control system, two torque fluctuation thresholds are preset: fluctuation threshold one and fluctuation threshold two, with fluctuation threshold two being greater than fluctuation threshold one. These two fluctuation thresholds divide torque fluctuations into three regions: good, requiring fine-tuning, and requiring strong intervention. Simultaneously, two sets of adjustment amounts are preset:

[0123] Angle adjustment amount one and temperature adjustment amount one correspond to fine adjustment;

[0124] Angle adjustment amount two and temperature adjustment amount two correspond to strong intervention.

[0125] Furthermore, the absolute value of angle adjustment amount two is greater than the absolute value of angle adjustment amount one, and the temperature adjustment amount two is greater than the temperature adjustment amount one. Specifically, the direction of angle adjustment is to decrease, so as to enhance the radial penetration force of the compensating airflow and act more directly on the low-speed core region; the direction of temperature adjustment is to increase, so as to enhance the thermal expansion effect and provide additional acceleration from an energy perspective.

[0126] Within the monitoring period following a compensation action, the torque fluctuation value, which characterizes the drive stability after the compensation, is calculated. The torque fluctuation value is then compared sequentially with fluctuation threshold one and fluctuation threshold two. Based on the comparison results, a graded adjustment strategy is executed.

[0127] Scenario 1: Torque fluctuation value is less than or equal to fluctuation threshold 1.

[0128] The system determines that the current compensation effect is excellent and the torque fluctuation is at an acceptable level; therefore, no adjustment is needed, and the current spray angle of the compensation nozzle and the temperature setting of the compensation airflow are maintained unchanged.

[0129] Scenario 2: The torque fluctuation value is greater than fluctuation threshold one and less than or equal to fluctuation threshold two.

[0130] The system initiates a first-level adjustment: the injection angle is reduced by one based on the current value, and the temperature of the compensating airflow is increased by one based on the current value.

[0131] Scenario 3: Torque fluctuation value is greater than fluctuation threshold 2:

[0132] Then the injection angle will be reduced by an angle adjustment amount of two based on the current value, and the temperature of the compensating airflow will be increased by a temperature adjustment amount of two based on the current value.

[0133] The new injection angle and temperature setpoints calculated above will be stored and applied the next time the system identifies a local low-speed area and triggers compensation. The adjustment process will not interfere with the compensation already completed, ensuring the stability of system operation.

[0134] It should be noted that, through high-fidelity simulation or ground bench testing, multiple starts were conducted under conditions of uniform air intake and ideal flow field. The standard deviation of the driving torque fluctuation was measured and statistically analyzed. Fluctuation threshold one was set to 1.1 to 1.2 times this standard deviation. Fluctuation threshold two was set to 1.5 to 3 times fluctuation threshold one.

[0135] Angle adjustment amount one is set to a small negative angle value. For example, based on the working range of the injection angle θ (15°≤θ≤60°), the initial step size can be set to 1%~2% of this range, i.e., |Angle Adjustment Amount One| = 0.15° ~ 0.9°; to be conservative, it can start from the lower limit, such as -0.5°. Angle adjustment amount two is set to 1.5~3 times that of angle adjustment amount one.

[0136] Temperature adjustment amount one is set to a small positive temperature value. Considering the upper limit constraint on temperature rise (T ≤ 1.10 × Tref), it can be set to 5%~10% of the allowable total temperature rise (0.10 × Tref). If Tref = 500K and the allowable temperature rise is 50K, then temperature adjustment amount one is 2.5K~5K; it can start from +3K. Temperature adjustment amount two is set to 1.5~2.5 times that of temperature adjustment amount one.

[0137] Example 2: Refer to Figure 5 As shown, this embodiment of the invention provides a vaneless turbine starting system based on bleed air pre-swirl tuning, comprising:

[0138] A sensor array, configured at the inlet of the pre-swirl chamber, is used to collect the instantaneous tangential velocity of the airflow at multiple locations along the circumferential direction to obtain the circumferential airflow velocity distribution;

[0139] The data processing module is used to calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution; and to identify at least one circumferential angle interval where the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber, based on the airflow distribution uniformity, as a local low-speed region.

[0140] The compensating nozzle is configured to correspond to the identified circumferential angle range and is used to inject compensating airflow into the pre-swirl chamber;

[0141] The control execution module, in response to the data processing module's identification of local low-speed regions, activates the corresponding compensation nozzles to inject compensation airflow to obtain a uniformly circumferentially distributed optimized airflow field within the pre-swirl chamber; the optimized airflow field is used to drive the turbine rotor to accelerate to the ignition speed.

[0142] The embodiments of the present invention are used to execute the guide vaneless turbine starting method based on bleed air pre-swirl tuning in Embodiment 1. Both belong to the same inventive concept and have the same beneficial effects, which will not be repeated here.

[0143] In summary, the bladeless turbine starting method and system based on bleed air pre-swirl tuning described in this invention actively identifies and compensates for local low-speed airflow regions within the pre-swirl chamber. It dynamically and proactively corrects the circumferential non-uniformity of airflow distribution within the pre-swirl chamber caused by factors such as upstream bleed air differences, pipeline asymmetry, and flow disturbances, thereby providing a significantly optimized circumferential driving flow field at the source. This optimized flow field acts on the turbine rotor, making the driving torque on each blade in the rotor's circumferential direction tend to be consistent, effectively suppressing periodic torque fluctuations and the resulting rotor vibration, and improving the smoothness and inherent safety of the starting acceleration process. Simultaneously, the uniform flow field ensures efficient utilization of limited bleed air energy by the blades, reduces local flow losses, and improves the overall efficiency of energy conversion to rotor kinetic energy, thus helping to shorten the time to reach ignition speed.

[0144] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for starting a vaneless turbine based on bleed air pre-swirl tuning, characterized in that, include: Obtain the circumferential airflow velocity distribution at the inlet of the pre-swirl chamber; the circumferential airflow velocity distribution is the instantaneous tangential velocity of the airflow at multiple positions along the circumferential direction at the annular cross section of the inlet; Calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution; Based on the uniformity of airflow distribution, at least one circumferential angle interval in which the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber is identified as a local low-speed region. For the local low-speed region, the compensation nozzles configured corresponding to the circumferential angle range are activated, and compensation airflow is injected into the pre-swirl chamber through the compensation nozzles to obtain an optimized airflow field with uniform circumferential distribution. The turbine rotor is pre-rotated by the optimized airflow field.

2. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 1, characterized in that, The injection direction of the compensation nozzle is configured to be downstream of the airflow in the local low-speed region, and the injection axis of the compensation nozzle forms an angle θ with the tangent direction of the pre-swirl cavity at the installation position of the compensation nozzle; wherein, the angle θ is an acute angle.

3. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 2, characterized in that, The included angle θ satisfies: 15°≤θ≤60°.

4. The method for starting a vaneless turbine based on bleed air pre-swirl tuning according to claim 1 or 2, characterized in that, The total temperature of the compensating airflow is higher than the total temperature of the airflow in the local low-speed region, and after compensation, the total temperature T of the airflow at the location of the local low-speed region before entering the turbine rotor satisfies the following relationship: T ref <T≤1.1×T ref ; Among them, T ref This represents the spatial average total temperature of the airflow at the inlet of the pre-swirl chamber.

5. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 1, characterized in that, The compensating airflow is based on pulsed injection; and the frequency of the pulsed injection is controlled to be synchronized with an integer multiple of the current rotational frequency of the turbine rotor.

6. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 1, characterized in that, Based on the circumferential airflow velocity distribution, the uniformity of airflow distribution is calculated, including: The current circumferential average velocity is calculated based on the instantaneous tangential velocity of the airflow at the multiple locations; Calculate the instantaneous deviation between the instantaneous tangential velocity of the airflow and the current circumferential average velocity at each of the aforementioned locations; Integrate the instantaneous deviation values ​​at all locations at the same moment to obtain the instantaneous spatial integral value; The uniformity of airflow distribution is obtained by performing a time-domain average on the sequence of instantaneous spatial integral values ​​that change over time.

7. The method for starting a vaneless turbine based on bleed air pre-swirl tuning according to claim 1 or 6, characterized in that, Identifying the local low-speed region includes: In response to the airflow distribution uniformity being less than a uniformity threshold, a region scanning signal is generated; In response to the region scanning signal, the circumference of the pre-spinning cavity inlet is divided into multiple scanning units; For each scanning unit, the number of measurement points where the instantaneous tangential velocity of the airflow within it is lower than the current circumferential average velocity is counted, and the ratio of the number of measurement points to the total number of velocity measurement points within the scanning unit is calculated. The scanning units whose ratio exceeds the ratio threshold are identified as candidate low-speed units; and the start angle and end angle of the candidate low-speed units are recorded. All candidate low-speed units are sorted by angle, and candidate low-speed units with adjacent angles or intervals less than the angle tolerance are merged into a continuous circumferential angle interval, which is output as the local low-speed region.

8. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 1, characterized in that, The process of pre-spinning the turbine rotor using the optimized airflow field also includes: During the monitoring period after injecting compensating airflow into the local low-speed region, the driving torque signal of the turbine rotor is monitored, and the torque fluctuation value during the monitoring period is calculated. The injection angle of the compensating nozzle and / or the temperature of the compensating airflow are adjusted according to the torque fluctuation value.

9. The method for starting a bladeless turbine based on bleed air pre-swirl tuning according to claim 8, characterized in that, Adjusting the injection angle of the compensating nozzle and / or the temperature of the compensating airflow based on the torque fluctuation value includes: The torque fluctuation value is compared with fluctuation threshold one and fluctuation threshold two, wherein fluctuation threshold two is greater than fluctuation threshold one; If the torque fluctuation value is less than or equal to the fluctuation threshold, then the injection angle and the temperature of the compensating airflow are not adjusted. If the torque fluctuation value is greater than the fluctuation threshold one and less than or equal to the fluctuation threshold two, then the injection angle is reduced by an angle adjustment amount one based on the current value, and / or the temperature of the compensation airflow is increased by a temperature adjustment amount one based on the current value. If the torque fluctuation value is greater than the fluctuation threshold two, then the injection angle will be reduced by angle adjustment amount two based on the current value, and / or the temperature of the compensation airflow will be increased by temperature adjustment amount two based on the current value; Wherein, the absolute value of the second angle adjustment is greater than the absolute value of the first angle adjustment, and the second temperature adjustment is greater than the first temperature adjustment.

10. A vaneless turbine starting system based on bleed air pre-swirl tuning, characterized in that, include: A sensor array, configured at the inlet of the pre-swirl chamber, is used to collect the instantaneous tangential velocity of the airflow at multiple locations along the circumferential direction to obtain the circumferential airflow velocity distribution; The data processing module is used to calculate the airflow distribution uniformity based on the circumferential airflow velocity distribution; and to identify at least one circumferential angle interval where the instantaneous tangential velocity of the airflow is less than the current circumferential average velocity at the inlet of the pre-swirl chamber, based on the airflow distribution uniformity, as a local low-speed region. A compensation nozzle, configured to correspond to the identified circumferential angle range, is used to inject compensation airflow into the pre-swirl chamber; The control execution module, in response to the data processing module's identification of the local low-speed region, activates the corresponding compensation nozzle to inject compensation airflow to obtain a uniformly circumferentially distributed optimized airflow field within the pre-swirl chamber; the optimized airflow field is used to drive the turbine rotor to accelerate to the ignition speed.

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