A flow expansion stability control method for low-reaction-degree compressor blade tip cutting

Abstract

The application provides a flow expansion stability control method for low-reaction-degree compressor blade tip cutting, and belongs to the field of compressor aerodynamic design. The method solves the existing conventional tip blade cutting technology, which is not originally designed to directly deal with this specific flow problem. The cutting form and design criteria cannot effectively solve or even worsen the flow instability risk problem faced by the low-reaction-degree rotor. The method comprises the following steps: performing three-dimensional flow field analysis on the original rotor blade to identify the high-load area where the tip leakage flow starts and develops; locally cutting the tip in the high-load area to change the local pressure distribution of the tip and the leakage flow path; the cutting position is arranged in the range of 10% to 90% chord length of the tip along the chord direction of the blade; the cutting form is an asymmetric and directional local cutting structure performed on the side close to the pressure surface or the side close to the suction surface. The method is used in the field of turbomachinery and aero-engine design.

Description

Technical Field

[0001] This invention belongs to the field of compressor aerodynamic design, and in particular relates to a flow stabilization control method for compressor blade tip cutting with low reaction force. Background Technology

[0002] As aero-engines continue to evolve towards higher thrust-to-weight ratios, higher efficiency, and wider operating ranges, compressor stage loads are constantly increasing. Against this backdrop, low-reaction, high-load compressors, as an important advanced aerodynamic design, have attracted widespread attention due to their ability to optimize stage load distribution and improve performance by redistributing the pressurization load between the rotor and stator. However, while this design brings high-load advantages, it also introduces significant technical challenges: its stability margin is typically poor. The core issue lies in the rotor blade tip region. Due to the pressure difference between the pressure and suction surfaces of the blades, fluid is driven through the tip clearance to form a leakage flow. This leakage flow further entrains and forms a strong tip leakage vortex. This vortex structure is strongly coupled with complex flow structures such as channel shock waves and endwall boundary layers, easily leading to flow separation and blockage in the tip region, becoming a key factor inducing rotating stall and limiting the compressor's stable operating range.

[0003] To address the instability problem of compressors, especially low-response compressors, those skilled in the art have explored various technical approaches. These existing technologies can be broadly categorized into two types: one focuses on the geometric modification of the blades themselves, and the other on flow control of the flow channel or casing. In the first type of technology, "tip trimming," which involves localized material removal at the blade tip, is a known method. However, in-depth analysis shows that traditional tip trimming techniques primarily stem from structural design requirements, such as frequency tuning to adjust the blade's natural frequency to avoid resonance; their primary purpose is not targeted aerodynamic optimization. Even when some studies use it for aerodynamic adjustment, it is mostly based on compressors with conventional reaction force designs. Its effects often manifest as a comprehensive, minor trade-off between multiple performance indicators such as flow rate, efficiency, pressure ratio, and stall margin, lacking a profound intervention in specific flow structures. Therefore, for the severe instability problem faced by low-response compressors, dominated by specific tip leakage vortices, its stabilization effect is not significant, and it may even worsen the flow field due to improper design.

[0004] In the second category of technologies, existing solutions focus more on stator flow field optimization or casing treatment. For example, endwall suction and tandem stator designs are used to improve stator angle-of-attack adaptability, or swept blades and casing circumferential grooves are applied to handle rotor tip flow. While these methods can extend stability margin to some extent, they generally have inherent drawbacks: either the control object is indirect, such as targeting the stator, failing to directly address the root cause of rotor tip leakage flow; or additional complex structures, moving parts, and control systems are required, significantly increasing system complexity, manufacturing costs, and maintenance difficulty; or their stability extension effect has reached its limit, making it difficult to meet the stringent requirements of next-generation ultra-high-load compressors.

[0005] In summary, existing technologies have significant shortcomings when facing the unique stability margin challenges of compressor rotors operating under low reaction forces and high loads. Traditional blade tip trimming technology, because its design principles are not specifically aimed at the exceptionally strong leakage flow / vortex problems caused by the unique load distribution in the blade tip region of low-reaction rotors, cannot provide an effective and reliable solution. Other stability enhancement measures are either not directly applicable or are too complex and costly, making them less than ideal choices. Summary of the Invention

[0006] In view of this, the present invention aims to propose a flow stability control method for low-reaction compressor tip cutting, in order to solve the problem that the existing conventional tip cutting technology is not designed to directly address this specific flow problem, and the cutting form and design criteria cannot effectively solve or may even worsen the flow instability risk faced by the low-reaction rotor.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a flow stabilization control method for low-reaction compressor blade tip cutting, the method comprising: Three-dimensional flow field analysis was performed on the original rotor blades to identify the high-load regions where the tip leakage flow started and developed. In the high-load region, the blade tip is locally cut to change the local pressure distribution and leakage flow path at the blade tip; The cutting position is arranged along the chord of the blade within a range of 10% to 90% of the chord length at the blade tip; The cutting form is an asymmetrical, directional local cutting structure performed on the side closer to the pressure surface or the side closer to the suction surface.

[0008] Furthermore, a preferred embodiment is proposed in which the cutting position is located within 10% to 50% of the chord length at the blade tip.

[0009] Furthermore, a preferred method is proposed, wherein the cutting parameters involved in the cutting are determined through collaborative optimization, and the cutting parameters include at least the cutting depth and the cutting width. The collaborative optimization takes at least one of the following as optimization objectives: compressor rotor peak efficiency, stability margin, total pressure loss in the blade tip region, and core strength of the leakage vortex.

[0010] Furthermore, a preferred method is proposed, wherein the cutting form is suction-side cutting, pressure-side cutting, or a combination of cutting. The suction side cutting involves forming a chamfered cutting surface at the blade tip position near the suction side. The pressure surface side cutting is to form a local cutting surface at the blade tip position near the pressure surface; The composite cutting involves performing local cutting on the side near the pressure surface and the side near the suction surface, respectively, and connecting them through an intermediate transition surface.

[0011] Furthermore, a preferred embodiment is proposed, wherein when the cutting method is suction-side cutting, the angle between the chamfered cutting surface and the original blade tip plane is 20° to 45°.

[0012] Furthermore, a preferred embodiment is proposed in which the cutting area is located at the blade tip along the blade height direction and covers the area corresponding to the blade tip gap, and is continuously transitioned to the blade tip platform or blade tip working surface.

[0013] Furthermore, a preferred embodiment is proposed in which a smooth transition is adopted between the cutting area and the uncut area.

[0014] Based on the same inventive concept, the present invention also proposes a rotor blade, wherein the rotor blade is a low-reaction-force high-load compressor rotor blade, and its tip has a locally cut structure formed by any of the methods described above.

[0015] Based on the same inventive concept, the present invention also proposes a compressor rotor, including a disk and a plurality of rotor blades as described in claim 8, wherein the plurality of rotor blades are circumferentially mounted on the disk.

[0016] Based on the same inventive concept, the present invention also proposes a compressor, including a compressor rotor as described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The low-reaction compressor tip cutting flow stabilization control method provided by this invention effectively weakens the intensity of tip leakage vortices by reconstructing the local pressure distribution and flow path in the tip region, delaying their expansion and rupture towards the flow channel center, thereby postponing the occurrence of rotating stall, significantly widening the compressor's stable operating range, and improving stability margin. Simultaneously, this method reduces the total pressure loss in the tip region caused by the strong mixing of leakage flow and mainstream flow, improving the compressor rotor's peak efficiency near the design operating conditions.

[0018] The method proposed in this invention requires no additional active control components, fluid lines, or complex casing structures within the compressor flow channel. It only requires controllable geometric cutting of a localized area at the tip of the existing rotor blades, or direct forming during the blade manufacturing stage. This passive flow control avoids introducing new failure points and does not increase system complexity or additional energy consumption. By preferentially placing the cutting area in the high-load region of the blade's middle section and ensuring a smooth transition with the original profile, this method achieves significant aerodynamic benefits while minimizing potential impacts on the blade's structural integrity and strength.

[0019] The method proposed in this invention acts directly on the rotor blades themselves. Its design criteria are strongly correlated with the specific aerodynamic parameters of low-reaction rotors, such as tip load distribution and leakage vortex evolution characteristics. Therefore, it can be applied to the design of low-reaction compressors with different reaction force distribution forms and different tip clearance levels, mainly in the fields of turbomachinery, aero-engine and gas turbine compressor aerodynamic design. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The diagram shows the prototype of the low-reaction compressor rotor and the cutting of the pressure surface according to the present invention. (a) is the prototype of the low-reaction compressor rotor, and (b) is the cutting of the pressure surface blade tip. TE is the trailing edge, PS is the pressure surface, LE is the leading edge, HUB is the blade tip, and Groove is the circumferential groove. Figure 2 The diagram shows the characteristic curves of a prototype low-reaction compressor rotor described in this invention at the same speed as the pressure surface cutting, where (a) is a schematic diagram of the total pressure rise and (b) is a schematic diagram of the efficiency. Figure 3 The diagram shows the flow field parameters at the point of highest efficiency of the pressure surface cutting of a prototype low-reaction compressor rotor according to the present invention. (a) is a schematic diagram of the flow field parameters at the point of highest efficiency of the prototype low-reaction compressor rotor, and (b) is a schematic diagram of the flow field parameters at the point of highest efficiency of the pressure surface cutting. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0022] Implementation Method 1: This implementation method addresses the limitations of existing conventional blade tip trimming technology. Since its design is not directly aimed at this specific flow problem, its cutting methods and design criteria cannot effectively solve, and may even worsen, the flow instability risk faced by low-response compressor blade tip trimming. Therefore, a flow stabilization control method for low-response compressor blade tip trimming is proposed. The method includes: Three-dimensional flow field analysis was performed on the original rotor blades to identify the high-load regions where the tip leakage flow started and developed. In the high-load region, the blade tip is locally cut to change the local pressure distribution and leakage flow path at the blade tip; The cutting position is arranged along the chord of the blade within a range of 10% to 90% of the chord length at the blade tip; The cutting form is an asymmetrical, directional local cutting structure performed on the side closer to the pressure surface or the side closer to the suction surface.

[0023] Preferably, the cutting position is located in the high-load region from the leading edge of the blade to near the maximum thickness, and more preferably, the cutting position is located within 10% to 50% of the chord length at the blade tip.

[0024] In this embodiment, the cutting parameters involved in the cutting are determined through collaborative optimization. The cutting parameters include at least the cutting depth and the cutting width. The collaborative optimization takes at least one of the following as the optimization objective: compressor rotor peak efficiency, stability margin, total pressure loss in the blade tip region, and core strength of the leakage vortex.

[0025] In practical applications, the cutting depth *h* represents the local removal amount from the original blade tip surface along the normal or a design-given direction, while the cutting width *b* is the characteristic dimension of the cutting region along the spanwise direction of the blade tip surface or the local surface expansion direction. *h* and *b* are determined through synergistic optimization based on the load distribution, clearance height, inlet distortion level, and target operating point of a specific low-reaction airfoil. The cutting position, cutting depth, cutting width, and cutting angle are determined through numerical simulation, experimentation, or a combination of both, thereby reducing tip leakage flow, decreasing tip leakage vortex intensity, and improving compressor rotor efficiency and stability margin.

[0026] In this embodiment, the cutting method is suction side cutting, pressure side cutting, or a combination of cutting. The suction side cutting involves forming a chamfered cutting surface at the blade tip position near the suction side. The pressure surface side cutting is to form a local cutting surface at the blade tip position near the pressure surface; The composite cutting involves performing local cutting on the side near the pressure surface and the side near the suction surface, respectively, and connecting them through an intermediate transition surface.

[0027] Specifically, the chamfered bevel of the suction surface forms a guide surface. This guide surface deflects the velocity vector of the leaking fluid passing through the gap from the pressure surface, changing it from an impact that is approximately perpendicular to the main flow of the suction surface to an adhering flow with a larger axial component along the bevel direction. This delays the intense shearing and entrainment process between the leaking flow and the boundary layer of the suction surface, thereby directly weakening the vortex core strength of the tip leakage vortex and making its vortex core trajectory closer to the suction surface.

[0028] The pressure-side cutting, by locally removing material at the pressure-side source of the leakage flow, essentially locally modifies the pressure gradient distribution on the blade surface. This locally reduces the effective pressure differential across the gap for the driving fluid near the cutting region, thereby reducing the mass flow rate and momentum of the tip leakage flow at its source.

[0029] Furthermore, when the cutting method is suction-side cutting, the angle between the chamfered cutting surface and the original blade tip plane is 20° to 45°. This chamfer guides the leakage flow to transition more smoothly from the pressure surface to the suction surface, reduces the impact angle between the leakage jet and the main flow of the suction surface, reduces local mixing losses, and weakens the leakage vortex intensity.

[0030] In this embodiment, the cutting can be constructed using a linear inclined plane, a circular arc transition surface, a spline transition surface, or a combination thereof; the cutting area is located at the blade tip along the blade height direction and covers the area corresponding to the blade tip gap, and is continuously transitioned to the blade tip platform or blade tip working surface.

[0031] In this embodiment, a smooth transition is used between the cutting area and the uncut area.

[0032] Implementation Method 2, see below Figures 1 to 3 This embodiment describes a complete implementation process for the flow stabilization control method for low-reaction compressor blade tip cutting described in Embodiment 1, including: Taking a low-reaction, high-load compressor rotor as the research object, and while keeping the rotor blade profile curvature, thickness distribution, installation angle, and nominal tip clearance constant, a local cutting design was implemented in the blade tip region. First, a three-dimensional flow field model of the original rotor was established, and the flow structure in the blade tip region was analyzed under design speed and near-stall conditions. The results show that the rotor exhibits a significant leakage flow initiation region and a tip leakage vortex development region within the 10%–50% chord length range at the blade tip, and this region is located at a high-load position near the blade tip.

[0033] Based on the above analysis, it was determined that the local cutting zone at the blade tip should be set within the range of 10%–90% of the chord length at the blade tip, and preferably arranged in the high-load area of ​​10%–50% of the chord length. The cutting zone is continuously distributed in the chord direction, smoothly transitions to the working surface of the blade tip in the span direction, and covers the local area corresponding to the blade tip clearance in the blade height direction.

[0034] Option 1 involves side cutting near the suction surface: a chamfered cutting surface is provided on the side closest to the suction surface, with the angle α between the chamfered surface and the original blade tip plane set at 30°. The cutting depth h and cutting width b are determined based on the original blade tip load distribution and numerical optimization results, allowing the leakage flow to smoothly change direction along the inclined plane after the gap, reducing the tendency for direct collision with the main flow of the suction surface. Calculation results show that this option can reduce the tip leakage vortex intensity and reduce the total pressure loss in the tip region.

[0035] Option 2 involves cutting the blade tip near the pressure surface: this method locally removes material from the blade tip to reduce the local pressure differential driving force between the pressure and suction surfaces, thereby reducing clearance leakage flow. This option is particularly suitable for situations where the original blade profile has a strong local pressure rise in front of the pressure surface, resulting in a large leakage flow.

[0036] Option 3 is a composite cutting method: local cutting structures are arranged simultaneously on both the pressure and suction sides, and smoothly connected through an intermediate transition surface. This option has the dual effect of reducing leakage flow and optimizing leakage direction, which can further alleviate clogging in the blade tip area.

[0037] The three schemes described above were compared and analyzed with the original blade. The results show that, compared with the original blade, the blade tip cutting scheme of this invention results in a more reasonable static pressure distribution in the blade tip region, a reconstructed leakage flow path, and a decrease in the vortex core intensity and its intrusion into the mainstream region of the blade tip leakage vortex. The accumulation of low-energy fluid at the blade tip is reduced under near-stall conditions, and channel blockage is delayed. Under both design and near-stall conditions, the compressor rotor efficiency and stability margin are improved.

[0038] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A flow stabilization control method for low-reaction compressor blade tip cutting, characterized in that, The method includes: Three-dimensional flow field analysis was performed on the original rotor blades to identify the high-load regions where the tip leakage flow started and developed. In the high-load region, the blade tip is locally cut to change the local pressure distribution and leakage flow path at the blade tip; The cutting position is arranged along the chord of the blade within a range of 10% to 90% of the chord length at the blade tip; The cutting form is an asymmetrical, directional local cutting structure performed on the side closer to the pressure surface or the side closer to the suction surface.

2. The flow stabilization control method for low-reaction compressor blade tip cutting according to claim 1, characterized in that, The cutting position is located within 10% to 50% of the chord length at the blade tip.

3. The flow stabilization control method for low-reaction compressor blade tip cutting according to claim 1, characterized in that, The cutting parameters involved in the cutting are determined through collaborative optimization. The cutting parameters include at least the cutting depth and the cutting width. The collaborative optimization takes at least one of the following as the optimization objective: compressor rotor peak efficiency, stability margin, total pressure loss in the blade tip region, and core strength of the leakage vortex.

4. The flow stabilization control method for low-reaction compressor blade tip cutting according to claim 1, characterized in that, The cutting method is suction side cutting, pressure side cutting, or a combination of cutting. The suction side cutting involves forming a chamfered cutting surface at the blade tip position near the suction side. The pressure surface side cutting is to form a local cutting surface at the blade tip position near the pressure surface; The composite cutting involves performing local cutting on the side near the pressure surface and the side near the suction surface, respectively, and connecting them through an intermediate transition surface.

5. The flow stabilization control method for low-reaction compressor blade tip cutting according to claim 4, characterized in that, When the cutting method is suction side cutting, the angle between the chamfered cutting surface and the original blade tip plane is 20° to 45°.

6. The flow stabilization control method for low-reaction compressor blade tip cutting according to claim 1, characterized in that, The cutting area is located at the blade tip along the blade height direction and covers the area corresponding to the blade tip clearance, and is continuously transitioned to the blade tip platform or blade tip working surface.

7. A flow stabilization control method for low-reaction compressor blade tip cutting according to any one of claims 1-6, characterized in that, A smooth transition is used between the cut area and the uncut area.

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