Aerodynamic design method for a compressor with a slotted endwall

Abstract

The application discloses a jet flow velocity maximized compressor end wall gap structure and a design method, and belongs to the field of turbomachinery; the end wall gap structure is located on the end wall of the blade root in the cascade passage, and comprises a gap inlet located on the end wall on the pressure surface side of the blade, a gap outlet located on the end wall on the suction surface side of the blade, and an airflow channel connected between the gap inlet and the gap outlet, so as to realize the local connection of the end walls on both sides of the blade root; the fluid near the pressure side end wall enters the airflow channel from the gap inlet and is ejected from the gap outlet, and the transition cooperation of the upper and lower wall surfaces of the airflow channel with the gap inlet and the gap outlet makes the jet flow of the gap adhere to the end wall and flow. The application solves the defects of the end wall active jet flow control technology, such as the need of external additional devices and the consumption of additional energy, and enriches the passive control means for the serious three-dimensional angle area separation in the blade passage of the high-load compressor.

Description

Technical Field

[0001] The present invention belongs to the field of impeller machinery, and in particular relates to a compressor end wall gap structure and a design method for maximizing jet velocity. Background Art

[0002] The current trend toward high thrust-to-weight ratios and low fuel consumption in aircraft engines has led to increasing design loads for axial-flow compressors. However, this continued increase in compressor load per stage leads to increased axial and lateral pressure gradients within the flow path. The resulting complex flow phenomena in the end zone can adversely affect compressor aerodynamic performance. Three-dimensional corner separation, a common complex flow phenomenon in the end zone of highly loaded axial-flow compressors, has long been a focus of research.

[0003] To date, a basic consensus has been reached: three-dimensional corner separation not only increases compressor losses, lag angles, and blockage, resulting in a decrease in aerodynamic efficiency, but can also induce rotating stall or surge, seriously affecting compressor operating stability and restricting further improvements in compressor aerodynamic performance. Therefore, based on a deep understanding of the complex flow mechanisms of compressors, delaying or eliminating corner separation through various feasible flow control technologies, thereby enabling compressors to maintain high aerodynamic efficiency and a wide stable operating range while maintaining high load levels, has become one of the important research directions in compressor aerodynamics in recent years.

[0004] Jet control technology generates jets through slits or circular holes in the endwall or blade surface. This re-energizes the low-energy boundary layer accumulated in the corners, thereby enhancing the boundary layer's ability to withstand adverse pressure gradients and effectively controlling corner separation. Consequently, jet control technology has been extensively researched and developed in recent years. Three mainstream jet control technologies are currently available: steady jets, unsteady jets, and synthetic jets.

[0005] Both steady and unsteady jets require additional piping systems and an external air supply. Synthetic jets, driven by an external force through an actuator, periodically reciprocate within a cavity, periodically drawing in and out air at the orifice. While this eliminates the need for complex piping systems, it still requires an external drive system. Therefore, all three of these jet technologies are considered active flow control technologies, requiring additional external equipment and energy consumption, resulting in lower economic and engineering feasibility.

[0006] In addition to the three active jet technologies mentioned above, a passive jet technology, namely blade slotted jet technology, also exists in the prior art. For example, the prior art discloses compressor stator blades with equal-width arc slots at the blade root. These slots can spontaneously generate passive jets driven by pressure differentials through the slot structure on the blades. However, as a component with relatively low structural strength in the compressor, slotting the compressor blades further reduces the blade strength, potentially having a serious adverse impact on the compressor's operating stability.

[0007] Therefore, it is very necessary to invent a passive jet device applied to the end wall (hub and casing) with higher structural strength. Summary of the Invention

[0008] Technical issues to be solved:

[0009] To overcome the shortcomings of the prior art, the present invention provides a compressor endwall slot structure and design method that maximizes jet velocity. Through a rational endwall slot structure, the slot inlet and outlet are connected to the pressure and suction sides of the endwall, maximizing the pressure differential between the slot inlet and outlet. The pressure differential across the endwall draws a portion of the fluid near the pressure side of the endwall into the slot, where it is accelerated by the pressure differential and the slot convergence section into a passive jet with maximized velocity. This effectively re-energizes the low-energy fluid accumulated in the blade suction / endwall corner region, improving its ability to resist adverse pressure gradients and achieving maximum control over severe three-dimensional angular separation. The present invention addresses the drawbacks of active endwall jet control technology, which requires external devices and consumes additional energy, and enriches the passive control methods for severe three-dimensional angular separation in high-load compressor blade passages. At the same time, it improves the economic efficiency, engineering practicality, and control effectiveness of jet control technology while avoiding significant adverse effects on the overall structural strength of the compressor.

[0010] The technical solution of the present invention is: a compressor end wall gap structure that maximizes the jet velocity, characterized in that: the end wall gap structure is located on the end wall of the blade root in the blade channel, including a gap inlet located on the end wall on the pressure side of the blade, a gap outlet located on the end wall on the suction side of the blade, and an airflow channel connecting the gap inlet and outlet, thereby realizing local connection between the end walls on both sides of the blade root; the fluid near the pressure side end wall enters the airflow channel from the gap inlet and is ejected from the gap outlet, and the gap jet flows in close contact with the end wall through the transition between the upper and lower wall surfaces of the airflow channel and the gap inlet and outlet.

[0011] A further technical solution of the present invention is that the slot inlet starts from the leading edge of the blade, and the slot outlet is located within the range of 10%-20% of the axial chord length Ca behind the starting point of the corner zone separation under design conditions.

[0012] A further technical solution of the present invention is that the inlet and outlet of the gap are respectively fitted to the pressure surface and suction surface of the blade root, and the cross-sectional contour line along the chord direction is consistent with the corresponding blade profile to ensure that the pressure difference between the inlet and outlet of the gap is maximized.

[0013] A further technical solution of the present invention is that the radial direction of any point in the airflow channel is perpendicular to the blade profile at the relative position to ensure that the jet direction is consistent with the blade profile, thereby enhancing the re-stimulation effect of the jet on the low-energy fluid accumulated in the corner area.

[0014] A further technical solution of the present invention is: the air flow channel includes an inlet end, a convergent section and an outlet end, the gap inlet area is larger than the gap outlet area, and the gap inlet throat area is larger than the gap outlet throat area, so as to ensure the overall convergence of the gap and thereby more fully accelerate the fluid introduced into the gap.

[0015] A further technical solution of the present invention is: the air flow channel relative to the slit outlet is the outlet end, and its starting point is located at 30% Ca behind the leading edge of the blade; the two ends of the convergent section are respectively connected to the inlet end and the outlet end, and its axial length is 10% Ca, and is located in the range of 20% Ca-30% Ca behind the leading edge of the blade; the air flow channel relative to the slit inlet is the inlet end, starting at the leading edge of the blade, and is located in the range of 0-20% Ca behind the leading edge of the blade, and can suck away sufficient proximal wall pressure side fluid into the end wall gap.

[0016] A further technical solution of the present invention is that the axial length of the slit outlet is 20% Ca, and the slit outlet is located in the range of 30% Ca-50% Ca behind the leading edge of the blade.

[0017] A further technical solution of the present invention is: the lower wall surface of the inlet end of the air flow channel is tangent to the pressure side end wall and smoothly transitions to reduce the loss caused by the air flow introduced into the gap; the upper and lower wall surfaces of the outlet end of the air flow channel are tangent to the suction side end wall respectively and smoothly transition to reduce the mixing loss between the gap jet and the mainstream and enhance the flow control effect.

[0018] A further technical solution of the present invention is: the widths of the slot inlet and outlet are 5%Ca and 2.5%Ca respectively, the slot inlet throat width is 2.0 times the slot outlet throat width, so that the overall slot convergence ratio is 4:1, so as to fully accelerate the airflow introduced into the slot; the depths of the lowest points of the upper and lower walls of the airflow channel are 1% of the blade height H and 4% H respectively.

[0019] A design method for compressor end wall gap structure to maximize jet velocity:

[0020] Construct a three-dimensional digital model of the endwall and blades based on the prototype cascade channel;

[0021] An end wall gap is opened on the end wall of the blade root to partially connect the end walls of the suction and pressure sides of the blade;

[0022] The inlet of the end wall slit is located on the end wall on the pressure side of the blade, and the outlet is located on the end wall on the suction side of the blade. The inlet and outlet of the slit are respectively in contact with the pressure side and suction side of the blade root. The cross-sectional contour line along the chord direction is consistent with the corresponding blade profile to ensure that the pressure difference between the inlet and outlet of the slit is maximized.

[0023] The lower wall surface at the inlet end of the end wall slot is tangent to the pressure side end wall and smoothly transitions to reduce the loss caused by the airflow introduced by the slot; the upper and lower wall surfaces at the outlet end of the end wall slot are tangent to the suction side end wall and smoothly transition to reduce the mixing loss between the slot jet and the mainstream and enhance the flow control effect;

[0024] The radial direction of any point of the gas channel in the end wall gap is perpendicular to the blade profile at the relative position to ensure that the jet direction is consistent with the blade profile, thereby enhancing the re-stimulation effect of the jet on the low-energy fluid accumulated in the corner area.

[0025] Numerical simulation calculations are performed to obtain the flow field and aerodynamic parameters of the compressor end wall gap structure.

[0026] A further technical solution of the present invention is: the numerical simulation calculation steps are as follows:

[0027] Step 1: Set boundary conditions;

[0028] The blade computational domain inlet was set at 2.5Ca from the leading edge, and the computational domain outlet was set at 1.5Ca from the trailing edge. Periodic boundary conditions were applied on both sides of the cascade channel so that the numerical simulation was performed within one blade channel. Symmetrical boundary conditions were applied in the middle of the blade span to model a flow field with only half the blade height, and a convergence acceleration method was used. The CFL condition number was set to 3.0, and the SA turbulence model was selected as the turbulence model.

[0029] Step 2: blade mesh division;

[0030] The prototype high-load compressor cascade mesh generated a mesh topology in the software, containing 1.43 million mesh nodes. In the IGG module of the software, an endwall slot mesh with 310,000 mesh nodes was implanted into the prototype high-load compressor cascade mesh to obtain a high-load compressor cascade mesh with an endwall slot structure. The slot inlet and outlet meshes were completely non-matched with the pressure-side endwall mesh and the suction-side endwall mesh, respectively.

[0031] Step 3: numerical simulation calculation;

[0032] The EURANUS solver in NUMECA Fine / Turbo software is used to solve the three-dimensional Reynolds-averaged Stokes equations in finite volume form in the Cartesian coordinate system. The central difference scheme with second-order accuracy is used for spatial discretization, and the explicit fourth-order Runge-Kutta method is used for temporal discretization for iterative solution. During the calculation process, a total temperature of 288.15 K, a total pressure of 101325 Pa, and an inlet airflow angle are given at the inlet of the computational domain. The static pressure at the outlet of the computational domain is adjusted to make the inlet Mach number 0.6.

[0033] Beneficial effects

[0034] The beneficial effects of the present invention are as follows: a high-load compressor blade cascade with endwall slot jets can maximize the acceleration of the fluid introduced into the slots through the endwall slot structure, under the influence of the slot inlet and outlet pressure differential and the convergent slot structure, and generate a high-speed jet at the endwall slot outlet, significantly stimulating the low-energy boundary layer accumulated in the blade suction surface / endwall corner area, enhancing its ability to resist adverse pressure gradients, thereby minimizing severe three-dimensional corner separation, reducing the degree of blockage and total pressure loss in the blade channel, and improving the blade's expansion capacity and operating stability. Compared to existing jet control technologies, the present invention does not require the introduction of external devices or the consumption of additional energy, has a smaller negative impact on the overall structural strength of the compressor, and has better control effect on corner separation, with higher economy and engineering practicality.

[0035] Numerical studies have shown that at an inlet Mach number of 0.6 and an inlet angle of attack of 0° and 4°, respectively, the endwall slot jet can significantly reduce the three-dimensional angular separation in the prototype high-load compressor cascade. The total pressure loss of the high-load compressor cascade with the endwall slot structure is reduced by 46.3% and 51.1%, respectively, compared to the prototype high-load compressor cascade, and the static pressure coefficient is increased by 34.3% and 47.9%, respectively. This shows that the high-load compressor cascade with the endwall slot structure has significantly lower total pressure loss and significantly enhanced pressure expansion capability than the prototype high-load compressor cascade at both angles of attack, which is extremely beneficial for improving the compressor's overall pressure ratio and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A three-dimensional schematic diagram of a high-load compressor blade with an end wall gap structure, where the end wall gap structure is marked in red.

[0037] Figure 2 Schematic diagram of the two-dimensional top view of the end wall gap structure.

[0038] Figure 3 It is a two-dimensional plan view schematic diagram of the end wall gap structure, where AB and CD represent the lower and upper walls of the gap, respectively.

[0039] Figure 4 The flow fields of the prototype high-load compressor cascade and the high-load compressor cascade with endwall slot structure in the embodiment are compared at 0° and 4° angles of attack, including the limiting streamlines on the suction surface and endwall of the blade, axial velocity contours at different positions in the blade channel, and the endwall slot jet.

[0040] Explanation of the accompanying symbols: 1—blade leading edge, 2—blade trailing edge, 3—blade middle, 4—blade suction surface, 5—blade pressure surface, 6—end wall, 7—end wall gap inlet, 8—end wall gap convergence section, 9—end wall gap outlet, 10—end wall gap upper wall surface, 11—end wall gap lower wall surface, 12—gap inlet length, 13—gap convergence section length, 14—gap outlet length, 15—gap inlet width, 16—gap outlet width, 17—gap upper wall depth, 18—gap lower wall depth, 19—gap inlet throat, 20—gap outlet throat, 21a—fluid entering the gap, 21b—end wall gap jet. DETAILED DESCRIPTION

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0043] Based on the drawbacks of existing technologies, such as the need for external additional devices and extra energy consumption, the present invention provides a compressor endwall slot structure that maximizes jet velocity. The endwall slot structure is located on the endwall at the root of the blade within the cascade channel and includes a slot inlet located on the endwall on the pressure side of the blade, a slot outlet located on the endwall on the suction side of the blade, and an airflow channel connecting the slot inlet and outlet, thereby achieving local connectivity of the blade root endwall. Fluid near the pressure-side endwall enters the airflow channel from the slot inlet and is ejected from the slot outlet. The transition between the upper and lower walls of the airflow channel and the slot inlet and outlet allows the slot jet to flow along the endwall. A reasonable endwall slot structure connects the slot inlet and outlet to the pressure side and suction side of the endwall, maximizing the pressure difference between the slot inlet and outlet. The pressure difference on both sides of the end wall draws part of the fluid on the pressure side near the end wall into the gap, and under the action of the pressure difference and the gap convergence section, it is accelerated into a passive jet with maximum velocity, thereby effectively re-stimulating the low-energy fluid accumulated in the suction surface / end wall corner area of ​​the blade, improving its ability to resist adverse pressure gradients, and thus achieving maximum control over severe three-dimensional corner separation. The specific plan is as follows:

[0044] Reference Figure 1-3 As shown, the compressor end wall slot structure for maximizing the jet velocity mainly includes a prototype high-load compressor blade, a slot inlet 7, an end wall slot convergence section 8, a slot outlet 9, a slot upper wall surface 10 and a slot lower wall surface 11; the slot inlet 7 is located on the pressure side of the end wall, and the slot outlet 9 is located on the suction side of the end wall, thereby partially connecting the end walls on both sides of the blade.

[0045] The slot inlet starts from the leading edge of the blade and is connected to the slot outlet through the slot convergence section. The slot outlet is located within the range of 10% Ca-20% Ca after the starting point of the corner zone separation under the design working condition to obtain the best control effect on the corner zone separation.

[0046] Specifically, the position of the slit outlet is selected based on the position of the starting point of the corner zone separation under the design working conditions, and is selected as the position 30% Ca behind the leading edge of the blade, which is located after the corner zone separation point and close to the corner zone separation point to achieve better flow control effect. The slit convergence section is located before the slit outlet and is connected to it. The length of the slit convergence section is set to a maximum of 10% Ca to fully accelerate the fluid entering the slit. Therefore, the slit convergence section is located in the range of 20% Ca-30% Ca behind the leading edge of the blade. The slit inlet starts at the leading edge of the blade and is connected to the slit convergence section. Therefore, the slit inlet is located in the range of 0-20% Ca behind the leading edge of the blade, which can suck away sufficient pressure side proximal wall fluid into the slit. In order to ensure sufficient jet flow, the slit outlet length is set to a maximum of 20% Ca. Therefore, the slit outlet is located in the range of 30% Ca-50% Ca behind the leading edge of the blade.

[0047] Specifically, the shapes of the inlet and outlet of the gap are the parts of the blade profile corresponding to the inlet and outlet lengths. The inlet and outlet of the gap are respectively close to the pressure side and suction side of the blade, so as to maximize the pressure difference between the inlet and outlet of the gap, so as to more fully accelerate the airflow and enhance the re-excitation effect of the jet on the low-energy fluid.

[0048] Specifically, the slot inlet and outlet widths are selected to be 5%Ca and 2.5%Ca, respectively. The slot inlet throat width is set to 2.0 times the slot outlet throat width, resulting in an overall slot convergence ratio of 4:1 to fully accelerate the airflow entering the slot. To meet the actual compressor casing or hub thickness requirements, the slot upper and lower wall depths are set relatively small, at 1%H and 4%H, or 1 mm and 4 mm, respectively.

[0049] Specifically, the width of the gap is perpendicular to the blade profile at the location thereof, so as to ensure that the jet direction is consistent with the blade profile, thereby enhancing the re-stimulation effect of the jet on the low-energy fluid accumulated in the corner area.

[0050] Specifically, the inlet area of ​​the slit is larger than the outlet area of ​​the slit, and the throat area of ​​the slit inlet is larger than the throat area of ​​the slit outlet, so as to ensure the convergence of the entire slit and thus more fully accelerate the fluid introduced into the slit.

[0051] Specifically, the lower wall surface of the slot is substantially tangent to the pressure side of the end wall and smoothly transitions thereto, so as to reduce the loss caused by the airflow introduced into the slot.

[0052] Specifically, the upper and lower walls of the slot are basically tangent to the suction side of the end wall and smoothly transition to ensure that the slot jet flows basically along the end wall, reducing the mixing loss between the slot jet and the mainstream and enhancing the flow control effect.

[0053] Specifically, the end wall may have one or more slot structures.

[0054] Specifically, the profile of the slot wall is fitted by a Bezier curve, and the lower slot wall is substantially tangent to the pressure side end wall and smoothly transitions to reduce the loss caused by the airflow introduced into the slot.

[0055] The effects of the above technical solution are further verified through specific experiments and accompanying drawings.

[0056] This embodiment is based on a high-load compressor blade grid, and its main design parameters are shown in Table 1. It is worth noting that the blade density (c / t) is a relatively small value of 1.48. Low-density design is conducive to reducing the number of single-stage compressor blades, thereby reducing the weight of the engine and increasing the thrust-to-weight ratio. However, lower density often also means higher load, which will cause the three-dimensional angular separation to become serious. Therefore, although the blade bending angle is only 36°, which is relatively small, its angular separation is very serious. In the numerical simulation, the blade inlet Mach number is selected as 0.6, the inlet angle of attack is selected as 0° and 4°, and the Reynolds number based on the blade chord length is 9.2×10 5 See also Figures 1 to 3 The present invention partially connects the pressure side end wall and the suction side end wall of the prototype high-load compressor blade through the end wall gap structure marked in red.

[0057] Table 1 Main design parameters of high-load compressor cascade

[0058]

[0059] This example describes a design method for a compressor end wall gap structure that maximizes jet velocity. The specific steps are as follows:

[0060] Construct a three-dimensional digital model of the endwall and blades based on the prototype cascade channel;

[0061] An end wall gap is opened on the end wall of the blade root to partially connect the end walls of the suction and pressure sides of the blade;

[0062] The inlet of the end wall slit is located on the end wall on the pressure side of the blade, and the outlet is located on the end wall on the suction side of the blade. The inlet and outlet of the slit are respectively in contact with the pressure side and suction side of the blade root. The cross-sectional contour line along the chord direction is consistent with the corresponding blade profile to ensure that the pressure difference between the inlet and outlet of the slit is maximized.

[0063] The lower wall surface at the inlet end of the end wall slot is tangent to the pressure side end wall and smoothly transitions to reduce the loss caused by the airflow introduced by the slot; the upper and lower wall surfaces at the outlet end of the end wall slot are tangent to the suction side end wall and smoothly transition to reduce the mixing loss between the slot jet and the mainstream and enhance the flow control effect;

[0064] The radial direction of any point of the gas channel in the end wall gap is perpendicular to the blade profile at the relative position to ensure that the jet direction is consistent with the blade profile, thereby enhancing the re-stimulation effect of the jet on the low-energy fluid accumulated in the corner area.

[0065] Numerical simulation calculations are performed to obtain the flow field and aerodynamic parameters of the compressor end wall gap structure.

[0066] The specific settings are as follows:

[0067] 1. The slot outlet is located within the range of 10% Ca to 20% Ca behind the starting point of the corner separation to enhance the control effect of the slot jet on the corner separation. In this embodiment, the slot outlet is located 30% Ca behind the leading edge of the blade.

[0068] 2. The slot outlet length is selected to be longer to obtain sufficient jet flow. In this embodiment, the slot outlet length is selected to be 20% Ca, and the slot outlet is located on the suction side end wall within the range of 30%-50% Ca behind the leading edge of the blade.

[0069] 3. The slot convergence section is located before and connected to the slot outlet. The slot convergence section should be long to fully accelerate the airflow. In this embodiment, the slot convergence section length is selected to be 10% Ca, that is, the slot convergence section is located in the range of 20% Ca-30% Ca behind the leading edge of the blade.

[0070] 4. The slot inlet starts from the leading edge of the blade and is connected to the slot convergent section. In this embodiment, the slot inlet is located on the pressure side end wall within the range of 0-20% Ca behind the leading edge of the blade, which can suck away sufficient fluid near the pressure side end wall.

[0071] 5. The slot inlet and outlet shapes are selected to correspond to the portion of the blade profile corresponding to their respective lengths. This helps ensure that the jet direction aligns with the blade suction-side profile, enhancing the jet's re-energizing effect on low-energy fluid accumulated in the corners. In this embodiment, the slot inlet shape is selected to correspond to the pressure-side blade profile within the range of 0-20% Ca behind the blade leading edge, and the slot outlet shape is selected to correspond to the suction-side blade profile within the range of 30% Ca-50% Ca behind the blade leading edge.

[0072] 6. To ensure that the slot jet flows along the suction side of the blade in the suction surface / end wall corner area, thereby better stimulating the low-energy boundary layer accumulated in the corner area, the width of the slot in the embodiment is set to be perpendicular to the blade profile at the local position.

[0073] 7. The inlet width of the slit should be larger than the outlet width to ensure that the convergence section of the slit is relatively convergent. In the embodiment, the inlet and outlet widths of the slit are set to 5% Ca and 2.5% Ca respectively.

[0074] 8. The gap depth should meet the actual thickness requirements of the compressor casing or hub. In the embodiment, the upper and lower walls of the gap are fitted by Bezier curves, with the upper wall depth set to 1%H and the lower wall depth set to 4%H.

[0075] 9. The width of the slot inlet throat should be greater than the width of the outlet throat to ensure that the slot convergence section is more convergent. In the embodiment, the ratio of the slot inlet throat to the outlet throat width is set to 2:1.

[0076] 10. In order to reduce the loss of fluid introduced into the proximal end wall of the pressure side, in the embodiment, the lower wall surface of the gap is configured to be substantially tangent to the pressure side end wall at point A for a smooth transition.

[0077] 11. In order to ensure that the slot jet flows basically along the end wall, reduce the mixing loss between the slot jet and the mainstream, and enhance the flow control effect, in the embodiment, the upper and lower walls of the slot are basically tangent to the suction side end wall at points D and B respectively and smoothly transition.

[0078] like Figure 1 As shown, fluid 21a near the pressure-side end wall is smoothly introduced into the slot at slot inlet 7. Driven by the pressure differential between the slot inlet and outlet and the acceleration of the slot convergence section, it forms a high-momentum jet 21b at the suction-side end wall slot outlet 9. Jet 21b significantly excites the low-energy boundary layer accumulated in the blade suction surface / end wall corner, increasing its kinetic energy and reducing its separation, thereby effectively controlling severe three-dimensional corner separation.

[0079] The numerical calculation process for the prototype high-load compressor cascade and the high-load compressor cascade with endwall slot structure is as follows:

[0080] 1. The blade calculation domain inlet is set to 2.5 times the chord length (c) from the leading edge of the blade to allow the inlet boundary layer to develop fully; and the calculation domain outlet is set to 1.5c from the trailing edge of the blade to allow the airflow behind the cascade to mix evenly. Periodic boundary conditions are given on both sides of the cascade channel so that the numerical simulation is carried out in one blade channel. In order to accelerate the convergence rate of the numerical solution, due to the symmetry of the compressor stator cascade flow along the middle of the blade span, symmetric boundary conditions are given in the middle of the blade span to model the flow field of only half the blade height. At the same time, convergence acceleration methods such as multi-grid method and implicit residual smoothing are adopted. In addition, the CFL condition number is taken as 3.0 in the calculation, and the turbulence model is selected as the SA turbulence model.

[0081] 2. The prototype high-load compressor blade grid mesh uses the AutoGrid5 module under FINE / TURBO software to generate an "O4H" type grid topology structure containing 1.43 million grid nodes. In the IGG module, the end wall slot grid with 310,000 grid nodes is implanted into the prototype high-load compressor blade grid to obtain a high-load compressor blade grid with an end wall slot structure. The slot inlet and outlet grids are completely non-matched with the pressure side end wall grid and the suction side end wall grid, respectively. At the same time, the grids at the slot inlet and outlet are encrypted to ensure the reliability of numerical transfer. The solid wall surface, including the blade surface, end wall and slot wall surface, is set as an adiabatic no-slip wall, and the grid close to the solid wall surface is also encrypted to more accurately capture the boundary layer.

[0082] 3. Numerical calculations were performed using the EURANUS solver in NUMECA Fine / Turbo software to solve the three-dimensional Reynolds-averaged Stokes equations in finite volume form in a Cartesian coordinate system. Spatial discretization employed a central difference scheme with second-order accuracy, while temporal discretization employed an explicit fourth-order Runge-Kutta iterative solution. The calculations were performed using a set total temperature of 288.15 K, a total pressure of 101,325 Pa, and an inlet flow angle at the computational domain inlet. The static pressure at the computational domain outlet was adjusted to maintain an inlet Mach number of 0.6.

[0083] Reference Figure 4 As shown, the prototype high-load compressor cascade is in a corner-stalling condition. The spanwise and circumferential extent of the corner-stalling separation is large, resulting in severe channel blockage. The degree of corner-stalling increases as the angle of attack increases from 0° to 4°. Compared to the prototype high-load compressor cascade, the high-speed jet from the high-load compressor cascade with the endwall slot structure significantly re-energizes the low-energy fluid accumulated in the blade suction surface / endwall corner region. This significantly reduces the severe three-dimensional corner-stalling separation at both 0° and 4° angles of attack, significantly reducing the recirculation range and blockage in the blade channel and avoiding corner-stalling. This significant reduction in the recirculation range means a reduction in total pressure loss, while the reduction in blade channel blockage represents an increase in the expansion of the blade channel, which in turn improves the pressure diffusion capability. Furthermore, the endwall slot jet velocity increases with increasing angle of attack, which is extremely beneficial for effectively controlling corner-stalling under higher load conditions. The proposed compressor endwall slot structure and design method for maximizing jet velocity are highly beneficial for overcoming load limitations and further improving the overall pressure ratio and efficiency of future compressors with higher loads. Furthermore, compared to blade slotting, which targets compressor blades with lower structural strength, the proposed slot structure is primarily targeted at compressor hubs or casings with higher structural strength, minimizing the negative impact on the overall structural strength of the compressor and offering greater engineering practicality.

[0084] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A compressor end wall gap structure for maximizing jet velocity, characterized by: The end wall slot structure is located on the end wall of the blade root in the cascade channel, and includes a slot inlet located on the end wall on the pressure side of the blade, a slot outlet located on the end wall on the suction side of the blade, and an airflow channel connecting the slot inlet and outlet, thereby achieving partial communication between the end walls on both sides of the blade root; the fluid near the pressure side end wall enters the airflow channel from the slot inlet and is ejected from the slot outlet, and the slot jet flows along the end wall through the transition between the upper and lower wall surfaces of the airflow channel and the slot inlet and outlet; The slot inlet starts at the leading edge of the blade, and the slot outlet is located within the range of 10%-20% of the axial chord length Ca behind the starting point of the corner zone separation under the design working condition; the slot inlet and outlet are respectively attached to the pressure surface and suction surface of the blade root, and the cross-sectional contour line along the chord direction is consistent with the corresponding part of the blade profile; The air flow channel includes an inlet end, a convergent section and an outlet end, the inlet area of ​​the slit is larger than the outlet area of ​​the slit, and the throat area of ​​the slit inlet is larger than the throat area of ​​the slit outlet; The airflow channel opposite to the slit outlet is the outlet end, and its starting point is located 30% Ca behind the blade leading edge; the two ends of the convergent section are respectively connected to the inlet end and the outlet end, and its axial length is 10% Ca, and is located in the range of 20% Ca-30% Ca behind the blade leading edge; the airflow channel opposite to the slit inlet is the inlet end, starting at the blade leading edge and located in the range of 0-20% Ca behind the blade leading edge, and can suck away sufficient proximal end wall pressure side fluid into the end wall slit; The inlet and outlet widths of the slit are 5%Ca and 2.5%Ca respectively, and the throat width of the slit inlet is 2.0 times the throat width of the slit outlet, so that the overall convergence ratio of the slit is 4:1, so as to fully accelerate the airflow introduced into the slit; the lowest point depths of the upper and lower walls of the airflow channel are 1% of the blade height H and 4%H respectively.

2. The compressor end wall gap structure for maximizing jet velocity according to claim 1, characterized in that: The radial direction of any point in the airflow channel is perpendicular to the profile line of the blade at the relative position.

3. The compressor end wall gap structure for maximizing jet velocity according to claim 2, characterized in that: The axial length of the slit outlet is 20%Ca, and is located in the range of 30%Ca-50%Ca behind the leading edge of the blade.

4. The compressor end wall gap structure for maximizing jet velocity according to claim 3, characterized in that: The lower wall surface of the airflow channel inlet end is tangent to the pressure side end wall and smoothly transitions; the upper and lower wall surfaces of the airflow channel outlet end are tangent to the suction side end wall and smoothly transitions respectively.

5. A method for designing a compressor end wall gap structure for maximizing jet velocity according to any one of claims 1 to 4, characterized in that: Construct a three-dimensional digital model of the endwall and blades based on the prototype cascade channel; An end wall gap is opened on the end wall of the blade root to partially connect the end walls of the suction and pressure sides of the blade; The inlet of the end wall slit is located on the end wall on the pressure side of the blade, and the outlet is located on the end wall on the suction side of the blade, wherein the inlet and outlet of the slit are respectively attached to the pressure side and the suction side of the blade root, and the cross-sectional contour line along the chord direction is consistent with the corresponding part of the blade profile; The lower wall surface of the end wall slot inlet is tangent to the pressure side end wall and smoothly transitions; the upper and lower wall surfaces of the end wall slot outlet are tangent to the suction side end wall and smoothly transitions respectively; The radial direction of any point of the gas passage in the end wall gap is perpendicular to the blade profile at the relative position to ensure that the jet direction is consistent with the blade profile; Numerical simulation calculations are performed to obtain the flow field and aerodynamic parameters of the compressor end wall gap structure.

6. The method for designing a compressor end wall gap structure for maximizing jet velocity according to claim 5, characterized in that: The numerical simulation calculation steps are as follows: Step 1: Set boundary conditions; The blade computational domain inlet was set at 2.5Ca from the leading edge, and the computational domain outlet was set at 1.5Ca from the trailing edge. Periodic boundary conditions were imposed on both sides of the cascade channel so that the numerical simulation was performed within one blade channel. Symmetrical boundary conditions were imposed in the middle of the blade span to model a flow field with only half the blade height, and a convergence acceleration method was used. In the calculation, the CFL condition number is taken as 3.0, and the turbulence model is selected as the SA turbulence model; Step 2: blade mesh division; The prototype high-load compressor cascade mesh generated a mesh topology in the software, containing 1.43 million mesh nodes. In the IGG module of the software, an endwall slot mesh with 310,000 mesh nodes was implanted into the prototype high-load compressor cascade mesh to obtain a high-load compressor cascade mesh with an endwall slot structure. The slot inlet and outlet meshes were completely non-matched with the pressure-side endwall mesh and the suction-side endwall mesh, respectively. Step 3: numerical simulation calculation; The EURANUS solver in NUMECA Fine / Turbo software is used to solve the three-dimensional Reynolds-averaged Stokes equations in finite volume form in the Cartesian coordinate system. The central difference scheme with second-order accuracy is used for spatial discretization, and the explicit fourth-order Runge-Kutta method is used for temporal discretization for iterative solution. During the calculation process, a total temperature of 288.15 K, a total pressure of 101325 Pa, and an inlet airflow angle are given at the inlet of the computational domain. The static pressure at the outlet of the computational domain is adjusted to make the inlet Mach number 0.6.

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