Centrifugal compressor end wall with concave-convex structure and implementation method thereof

Abstract

The invention belongs to the field of impeller machinery, and provides a centrifugal compressor end wall with a concave-convex structure and an implementation method thereof, and the implementation method comprises the following steps: constructing a centrifugal compressor plane graph, drawing a circle M1, drawing a circle M2, determining a convex structure T1, determining a concave structure T2 and manufacturing an improved centrifugal compressor. The inner wall surface of the casing is provided with the convex and concave structures, so that the flowing state in the gas compressor can be effectively improved, and meanwhile, the inhibition effect on the leakage flow of the gas compressor can be improved.

Description

Technical Field

[0001] The invention relates to the field of impeller machinery, and in particular to a centrifugal compressor end wall with a concave-convex structure and a realization method thereof. Background Art

[0002] With the advancement of science and technology, centrifugal compressors are developing towards high speed, high pressure ratio, high efficiency and miniaturization. During this development process, centrifugal compressors are prone to unstable flow phenomena such as flow separation, backflow, vortex and rotating stall under certain operating conditions. The reason is that due to the existence of blade tip clearance in centrifugal compressors, the blade basin and blade back area are affected by the pressure difference, and part of the fluid passes through the blade tip clearance to form a leakage flow. During the operation of the compressor, the leakage flow in the blade tip clearance will also mix with the mainstream, and mutual entrainment will occur, forming a blade tip leakage vortex. The above-mentioned complex secondary flow categories will have a negative blocking effect on the mainstream, accelerate flow separation, and cause rotating stall to occur in advance, thereby causing the compressor efficiency to decrease and the blade vibration amplitude to increase, causing great damage to the safe and stable operation of the entire centrifugal compressor system. In order to further improve the working performance of centrifugal compressors and broaden their stable working range, end wall treatment technology is favored by experts and scholars. Through research, it is found that end wall treatment technology can well broaden the safe and stable operating range of impeller machinery.

[0003] However, the current end wall treatment technology is still not perfect. Some end wall structural treatments will improve the compressor performance at the cost of some efficiency losses, and the leakage flow suppression capability is not strong, resulting in poor overall performance. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a centrifugal compressor end wall with a concave-convex structure and a method for implementing the same, so as to improve the problems in the prior art that the centrifugal compressor end wall structure has weak ability to suppress blade tip leakage flow and poor operating stability.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A centrifugal compressor end wall with a concave-convex structure, characterized in that it comprises: a hub, a compressor blade fixedly connected to the hub, and a casing that wraps the compressor blade in the air; the inner wall surface of the casing is provided with the convex structure T1 and the concave structure T2;

[0007] The gap between the inner wall of the casing and the blade tip of the compressor blade is l; the axial length, radial length and radial thickness of the casing are L, H and h respectively; the raised structure T1 is located at the intersection of the perpendicular line y and the inner wall of the casing at the preset proportional position of the radial H and h of the outer surface of the casing; the recessed structure T2 is located at the intersection of the normal line x at the radial h position of the outer surface of the casing and the blade tip.

[0008] Preferably, a method for realizing a centrifugal compressor end wall having a concave-convex structure comprises:

[0009] Construct a centrifugal compressor plan;

[0010] Take the preset proportional position of the radial H and h of the outer surface of the casing as the perpendicular line y and intersect the inner wall of the casing at point O1, and take the point O1 as the center and extend 1 / 5 times l toward the blade tip along the normal direction of the inner wall of the casing to obtain a circle M1;

[0011] Take the radial position h of the outer surface of the casing as the normal line x and intersect the blade tip at point O2, and take point O2 as the center and extend it along the meridian normal direction of the outer wall of the casing by 2 times l to make a circle M2;

[0012] The intersection points of the circle M1 and the inner wall of the casing are taken as A1 and B1, the midpoint C1 of A1 and B1 is taken, and a sphere tangent to the circle M1 is made with the midpoint C1 as the center to obtain a sphere N1, and the portion of the sphere N1 exposed outside the inner wall of the casing is determined as the protruding structure T1;

[0013] The intersection points of the circle M2 and the inner wall of the casing are taken as A2 and B2, the midpoint C2 of A2 and B2 is taken, and a sphere tangent to the circle M2 is made with the midpoint C2 as the center to obtain a sphere N2, and the portion of the sphere N2 embedded in the inner wall of the casing is determined as the concave structure T2;

[0014] A centrifugal compressor is manufactured according to the centrifugal compressor plan view with the convex structure T1 and the concave structure T2 to obtain an improved centrifugal compressor.

[0015] The present invention discloses the following technical effects:

[0016] The present invention provides a centrifugal compressor end wall with a concave-convex structure and a method for realizing the same. By providing convex and concave structures on the inner wall of a casing, the problems of weak blade tip leakage flow suppression capability and poor operating stability of the centrifugal compressor end wall structure in the prior art are solved, thereby achieving an improvement in the flow state inside the compressor and an enhancement in the compressor leakage flow suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A meridian schematic diagram of the overall structure of a centrifugal compressor provided by an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of the protrusion and recessed structure at the end wall of a centrifugal compressor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The purpose of the present invention is to provide a centrifugal compressor end wall with a concave-convex structure and a method for realizing the same, so as to improve the problems in the prior art that the centrifugal compressor end wall structure has a weak ability to suppress blade tip leakage flow and has poor operating stability.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 A meridian schematic diagram of the overall structure of a centrifugal compressor provided by an embodiment of the present invention, Figure 2 A schematic diagram of the protrusion and recess structure at the end wall of a centrifugal compressor provided by an embodiment of the present invention is shown in FIG. Figure 1 and Figure 2 As shown, the present invention provides a centrifugal compressor end wall with a concave-convex structure, comprising: a hub, a compressor blade fixedly connected to the hub, and a casing wrapping the compressor blade in the air; the inner wall surface of the casing is provided with the convex structure T1 and the concave structure T2;

[0024] The gap between the inner wall of the casing and the blade tip of the compressor blade is l; the axial length, radial length and radial thickness of the casing are L, H and h respectively; the raised structure T1 is located at the intersection of the perpendicular line y and the inner wall of the casing at the preset proportional position of the radial H and h of the outer surface of the casing; the recessed structure T2 is located at the intersection of the normal line x at the radial h position of the outer surface of the casing and the blade tip.

[0025] Preferably, a method for realizing a centrifugal compressor end wall having a concave-convex structure comprises:

[0026] Construct a centrifugal compressor plan;

[0027] Take the preset proportional position of the radial H and h of the outer surface of the casing as the perpendicular line y and intersect the inner wall of the casing at point O1, and take the point O1 as the center and extend 1 / 5 times l toward the blade tip along the normal direction of the inner wall of the casing to obtain a circle M1;

[0028] Take the radial position h of the outer surface of the casing as the normal line x and intersect the blade tip at point O2, and take point O2 as the center and extend it along the meridian normal direction of the outer wall of the casing by 2 times l to make a circle M2;

[0029] The intersection points of the circle M1 and the inner wall of the casing are taken as A1 and B1, the midpoint C1 of A1 and B1 is taken, and a sphere tangent to the circle M1 is made with the midpoint C1 as the center to obtain a sphere N1, and the portion of the sphere N1 exposed outside the inner wall of the casing is determined as the protruding structure T1;

[0030] The intersection points of the circle M2 and the inner wall of the casing are taken as A2 and B2, the midpoint C2 of A2 and B2 is taken, and a sphere tangent to the circle M2 is made with the midpoint C2 as the center to obtain a sphere N2, and the portion of the sphere N2 embedded in the inner wall of the casing is determined as the concave structure T2;

[0031] A centrifugal compressor is manufactured according to the centrifugal compressor plan view with the convex structure T1 and the concave structure T2 to obtain an improved centrifugal compressor.

[0032] Preferably, the key structural functions are defined as:

[0033] Raised structure: 1) The raised structure can guide and deflect the leakage flow through the local acceleration effect, which can reduce the intensity of the tip leakage vortex and suppress the shock wave / boundary layer interference under transonic conditions; 2) The structure can achieve the effect of pressure field regulation, and by forming a local high-pressure area in the leading edge area, it has the function of delaying the starting position of the suction surface flow separation; 3) The structure can reduce the starting flow of the rotating stall through asymmetric circumferential pressure disturbance, thereby achieving the effect of improving the stall margin.

[0034] Recessed structure: 1) The recessed structure forms a low-speed recirculation zone in the groove, capturing a certain proportion of high-entropy fluid in the tip leakage flow, thereby reducing the mainstream mixing loss and realizing the function of low-energy fluid accumulation; 2) The groove volume effect can also attenuate the amplitude of the tip clearance excitation force, thereby improving the rotor dynamics stability margin.

[0035] Synergistic effect: On the one hand, the coupling effect of T1 and T2 can improve the isentropic efficiency of the design point and broaden the stable working range of the compressor; on the other hand, it can weaken the amplitude of the exciting force to improve the structural stability of the compressor blades.

[0036] Specifically, the radius of the circle M1 on the meridian plane of the casing is 1 / 5l, and the radius of the circle M2 is 2l.

[0037] Preferably, the intersection points of the circle M1 and the inner wall of the casing are A1 and B1, the straight lines A1 and B1 are connected, the midpoint C1 of the straight line A1B1 is taken, and a circle M3 is drawn with C1 as the center. The distance from the intersection point of M3 and M1 to C1 is the radius of the circle M3. The circle M3 is rotated with A1B1 as the rotation axis to form a sphere N1 with a radius of n1. The part of the sphere N1 exposed on the outer side of the inner wall of the casing is taken as the protruding structure T1; the intersection points of the circle M2 and the inner wall of the casing are A2 and B2, and A1 and B2 are connected. 2. Line B2, take the midpoint C2 of line A2B2, draw a circle M4 with C2 as the center, the distance from the intersection of M4 and M2 to C2 is the radius of circle M4, rotate circle M4 with A2B2 as the rotation axis to form a sphere N2, the radius of the sphere is n2, and take the part of sphere N2 embedded in the inner wall of the casing as the concave structure T2. This concave structure increases the surface roughness, promotes airflow adhesion, reduces flow separation, and increases kinetic energy exchange between fluids, thereby achieving control of the fluid in the flow field.

[0038] Furthermore, the specific method for obtaining the convex and concave structures is as follows: on the premise that the ball N1 and the ball N2 have been obtained, the balls N1, N2 and the inner wall of the casing will form closed curves k1 and k2, and cutting is performed along the closed curves k1 and k2, and the part of the ball N1 that is biased towards the outer wall of the casing is removed, and the solid part of the ball N1 that is biased towards the inner wall of the casing is retained (K1 is a closed curve between the ball N1 and the inner wall of the casing, and because the ball N1 can be used as a convex structure, it is not necessary to remove along k1); the ball N2 and the casing will have an intersection surface K2, and the part of the casing that is biased towards the inner wall of the casing and the part of the casing between the surface K2 and the intersection line k2 are removed to obtain the concave surface K2;

[0039] Preferably, when the airflow passes through the concave structure T2 and the convex structure T1 of the end wall, a local rotational flow is generated, which changes the structure of the boundary layer, specifically affecting the boundary layer area around the balls N1 and N2. Through these disturbances, the kinetic energy of the airflow is locally enhanced, and the thickness of the boundary layer is therefore reduced. This phenomenon enables the fluid to adhere more closely to the blade end wall, thereby reducing the risk of flow separation. Reducing the presence of low-energy fluid in the boundary layer helps prevent airflow separation, especially in the end area of ​​the blade. The reduction in the thickness of the boundary layer means that the energy of the airflow has been improved, making it better able to overcome resistance and remain attached. This enhancement of the airflow attachment effect can delay or avoid flow separation, thereby improving the flow field characteristics of the entire compressor.

[0040] Furthermore, the blade end wall area in the centrifugal compressor often becomes a high-incidence area of ​​flow separation and energy loss due to the existence of centrifugal force. With the cooperation of the concave structure T2 and the convex structure T1, the centrifugal force on the airflow is regulated. The convex structure T1 guides the airflow to adhere quickly to the surface, while the concave structure T2 effectively guides the local turbulence, allowing the fluid to better adhere to the blade surface and reduce the flow separation caused by centrifugal force. Through this method, the flow path in the end wall area can be further optimized, the flow loss can be reduced, and the compressor efficiency can be improved.

[0041] Specifically, in a centrifugal compressor, leakage flow usually occurs in high pressure difference areas, which are prone to form irregular flows and affect the efficiency of the compressor. By designing a concave structure T2 and a convex structure T1 on the end wall, the local pressure distribution near the blade can be effectively adjusted. The combination of concave and convex structures not only changes the airflow path, but also has a micro-regulatory effect on the pressure of the airflow. The convex structure T1 can increase the local pressure and block the free leakage of the airflow; the concave structure T2 guides the airflow into a specific flow path by reducing the local pressure. This type of structural design forms a stronger airflow guidance and control effect, prevents the free development of the leakage flow, and avoids the efficiency loss caused by the leakage flow. In addition, this embodiment only explains the specific implementation method of the convex and concave structures in a method for processing the end wall of a centrifugal compressor with a concave and convex structure, including but not limited to the number and position of processing along the radial and circumferential directions of the casing.

[0042] The beneficial effects of the present invention are as follows:

[0043] The present invention improves the problems existing in the prior art, such as the weak ability of certain end wall structures of centrifugal compressors to suppress blade tip leakage flow and poor operating stability, by providing protrusions and recesses on the inner wall of the casing. The present invention has a simple structure and wide applicability, and can effectively improve the flow state inside the compressor while improving the inhibitory effect on the compressor leakage flow.

[0044] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0045] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A centrifugal compressor end wall with a concave-convex structure, characterized in that: include: A wheel hub, a compressor blade fixedly connected to the wheel hub, and a casing wrapping the compressor blade in the air; The inner wall surface of the casing is provided with the convex structure T1 and the concave structure T2; The gap between the inner wall of the casing and the blade tip of the compressor blade is l; the axial length, radial length and radial thickness of the casing are L, H and h respectively; the raised structure T1 is located at the intersection of the perpendicular line y and the inner wall of the casing at the preset proportional position of the radial H and h of the outer surface of the casing; the recessed structure T2 is located at the intersection of the normal line x at the radial h position of the outer surface of the casing and the blade tip.

2. A method for realizing a centrifugal compressor end wall with a concave-convex structure, characterized in that: Applied to the centrifugal compressor end wall with a concave-convex structure as claimed in claim 1, the implementation method comprises: Construct a centrifugal compressor plan; Take the preset proportional position of the radial H and h of the outer surface of the casing as the perpendicular line y and intersect the inner wall of the casing at point O1, and take the point O1 as the center and extend 1 / 5 times l toward the blade tip along the normal direction of the inner wall of the casing to obtain a circle M1; Take the radial position h of the outer surface of the casing as the normal line x and intersect the blade tip at point O2, and take point O2 as the center and extend it along the meridian normal direction of the outer wall of the casing by 2 times l to make a circle M2; The intersection points of the circle M1 and the inner wall of the casing are taken as A1 and B1, the midpoint C1 of A1 and B1 is taken, and a sphere tangent to the circle M1 is made with the midpoint C1 as the center to obtain a sphere N1, and the portion of the sphere N1 exposed outside the inner wall of the casing is determined as the protruding structure T1; The intersection points of the circle M2 and the inner wall of the casing are taken as A2 and B2, the midpoint C2 of A2 and B2 is taken, and a sphere tangent to the circle M2 is made with the midpoint C2 as the center to obtain a sphere N2, and the portion of the sphere N2 embedded in the inner wall of the casing is determined as the concave structure T2; A centrifugal compressor is manufactured according to the centrifugal compressor plan view with the convex structure T1 and the concave structure T2 to obtain an improved centrifugal compressor.

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