An air entrainment structure with shallow grooves on the back of a centrifugal impeller

Abstract

The present invention discloses an air bleed structure with shallow grooves on the back of a centrifugal impeller disk, comprising: a centrifugal impeller, a stator, and shallow grooves; the centrifugal impeller disk back is provided with multiple shallow grooves circumferentially; the centrifugal impeller rotates about its central axis, with a stator provided on the right side. The present invention processes shallow grooves on the back of the impeller disk by milling, a simple, low-cost, and time-efficient process. The shallow grooves on the back of the impeller disk can reduce the weight of centrifugal impeller components by 4.5-6%, thereby improving the engine's power-to-weight ratio / thrust-to-weight ratio. The Coriolis force of the radially inward-flowing air bleed acts on the protruding ribs of the shallow grooves on the back of the impeller disk, reducing engine power loss. It also achieves pre-cooling of the bleed air, creating a more favorable thermal environment for cooling downstream components, sealing the turbine rotor-static stage, and sealing the bearing cavity.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation engines, and in particular relates to an air entrainment structure of a centrifugal impeller disk with shallow grooves. Background Art

[0002] Conventional centrifugal impeller back cavity air induction scheme is as follows Figure 1 As shown, the centrifugal impeller is a rotating part, and the back of the impeller disk is a smooth transition wall. Air is induced from the root of the centrifugal impeller outlet, and the induced air passes radially inward through the radial disk cavity between the centrifugal impeller and the stator component, and is used for cooling and sealing the subsequent components.

[0003] For the existing technical solutions, when the bleed air flows radially inward, it is driven to rotate by the centrifugal impeller. There is a significant speed difference between the bleed air flow and the rotating centrifugal impeller, which not only consumes the engine friction work, but also absorbs the friction work, causing the bleed air flow to rise in temperature due to wind resistance along the way, which is not conducive to the cooling of downstream parts.

[0004] The axial force of the impeller back cavity is obtained by integrating the inner and outer diameter pressure areas along the radial direction, such as Figure 2 As shown, the bleed air flow is driven by the rotating side of the impeller back cavity, and the axial swirl velocity of the air flow is always lower than the wheel speed. The low swirl velocity and the small radial pressure drop of the back cavity result in a large static pressure at the low radius of the back cavity. The greater the forward axial force of the back cavity, when the forward axial force of the engine rotor is already very large, the increase in the forward axial force of the impeller back cavity will bring additional load to the bearing and reduce the bearing service life. Summary of the Invention

[0005] In order to solve the above problems, the present invention discloses an air entrainment structure of a centrifugal impeller with shallow grooves, comprising: a centrifugal impeller, a stator and shallow grooves;

[0006] The centrifugal impeller disc is provided with a plurality of shallow grooves on the back circumference;

[0007] The centrifugal impeller rotates around the central axis, and a stator is arranged on the right side.

[0008] Furthermore, the number of the shallow grooves is 10 to 30.

[0009] Furthermore, the shallow groove includes a first side wall, a second side wall and a third side wall;

[0010] The first side wall is a raised rib wall;

[0011] The second side wall and the third side wall are arc-shaped, the second side wall is shorter than the third side wall, and the third side wall is located outside the second side wall;

[0012] The first side wall, the second side wall, the first side wall and the third side wall are connected in sequence to form a shallow groove.

[0013] Furthermore, the raised rib wall is a straight blade or a curved blade;

[0014] The raised rib wall includes a raised rib wall first end and a raised rib wall second end, the raised rib wall first end is connected to the second side wall, and the raised rib wall second end is connected to the third side wall;

[0015] The second end of the raised rib wall is wider than the first end of the raised rib wall.

[0016] Furthermore, the inner diameter of the centrifugal impeller is 167 mm, and the outer diameter of the centrifugal impeller is 425 mm.

[0017] Furthermore, the inner diameter of the shallow groove is 1.1 to 1.3 times the inner diameter of the centrifugal impeller disk back.

[0018] Furthermore, the outer diameter of the shallow groove is 0.85 to 0.985 times the outer diameter of the back of the centrifugal impeller disk.

[0019] Furthermore, the axial distance between the back side of the centrifugal impeller disc and the stator is 2 to 6 mm.

[0020] Furthermore, the depth of the shallow groove is 1 to 4 mm.

[0021] Furthermore, the top and bottom ends of the second side wall and the third side wall are rounded, and the rounding radius is 1 / 2 of the shallow groove depth.

[0022] Compared with the prior art, the embodiments of the present invention have at least the following advantages:

[0023] 1) Based on the integral impeller disc, shallow grooves are machined on the back of the impeller disc by milling. This method is simple, low-cost, and time-saving. At the same time, the shallow groove design on the back of the impeller disc can reduce the weight of the centrifugal impeller parts by 4.5-6%, thereby improving the engine power-to-weight ratio / thrust-to-weight ratio;

[0024] 2) The Coriolis force of the radial inward bleed air acts as a positive force on the raised ribs of the shallow grooves on the back of the impeller disk, which can reduce engine power loss and simultaneously achieve bleed air pre-cooling, creating a more favorable thermal environment for cooling downstream components, sealing the turbine rotor and stator stages, and sealing the bearing cavity.

[0025] 3) The bleed air flow is constrained by the rotating shallow groove, and the circumferential swirl of the air flow in the shallow groove is 1, which can increase the radial pressure drop of the back cavity air flow, reduce the average cavity pressure of the impeller back cavity, and reduce the forward axial force of the rotor of the engine.

[0026] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of conventional centrifugal impeller back cavity air bleed is shown;

[0029] Figure 2 A schematic diagram of the static pressure distribution of the airflow in the back cavity of a centrifugal impeller according to an embodiment of the present invention is shown;

[0030] Figure 3 A schematic structural diagram of an air entrainment structure according to an embodiment of the present invention is shown;

[0031] Figure 4 A schematic diagram of a shallow groove structure according to an embodiment of the present invention is shown;

[0032] Figure 5 The diagram shows the shallow grooves and velocity triangle distribution on the back of a centrifugal impeller according to an embodiment of the present invention;

[0033] Figure 6 A schematic diagram of Coriolis force work according to an embodiment of the present invention is shown;

[0034] Figure 7 A schematic cross-sectional view of a centrifugal impeller according to an embodiment of the present invention is shown;

[0035] Figure 8 A schematic diagram of a curved shallow groove according to an embodiment of the present invention is shown;

[0036] Figure 9 A schematic diagram of swirl coefficients of different structures according to an embodiment of the present invention is shown;

[0037] Figure 10 A schematic diagram of the static pressure coefficient of the impeller back cavity with different structures according to an embodiment of the present invention is shown;

[0038] Figure 11 The absolute total temperature (unit: K) of the impeller back cavity with different structures according to the embodiment of the present invention is shown.

[0039] Figure numerals: 1, centrifugal impeller; 2, stator; 3, shallow groove; 31, first side wall; 32, second side wall; 33, third side wall; 34, first end of raised rib wall; 35, second end of raised rib wall. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making creative efforts shall fall within the scope of protection of the present invention.

[0041] like Figure 3 As shown, the present invention proposes an air entrainment structure of a centrifugal impeller disc with shallow grooves, comprising: a centrifugal impeller 1, a stator 2 and a shallow groove 3;

[0042] The centrifugal impeller 1 is provided with a plurality of shallow grooves 3 on the circumference of the back of the disc;

[0043] The centrifugal impeller 1 rotates around the central axis, and a stator 2 is provided on the right side.

[0044] The centrifugal impeller 1 is used to rotate the airflow and increase the airflow pressure in the main channel (left side). A certain gap must be maintained between the centrifugal impeller 1 and the stator 2 to prevent collision and friction. Therefore, air is often introduced at the root of the impeller outlet to cool and seal the downstream parts.

[0045] The shallow groove 3 is used to increase the swirl of the air introduced at the outlet of the centrifugal impeller 1, reduce the static pressure of the impeller back cavity, and reduce the forward axial force of the engine rotor.

[0046] In some embodiments, the number of the shallow grooves 3 is 10 to 30.

[0047] A circle of shallow grooves 3 is arranged along the circumferential direction on the back of the centrifugal impeller 1, which can reduce the weight of the centrifugal impeller 1 by 4.5-6% and improve the power-to-weight ratio / thrust-to-weight ratio of the engine.

[0048] like Figure 4 As shown, in some embodiments, the shallow groove 3 includes a first side wall 31, a second side wall 32 and a third side wall 33;

[0049] The first side wall 31 is a raised rib wall;

[0050] The second side wall 32 and the third side wall 33 are arc-shaped, and the second side wall 32 is shorter than the third side wall 33 , and the third side wall 33 is located outside the second side wall 32 ;

[0051] The first side wall 31, the second side wall 32, the first side wall 31 and the third side wall 33 are connected in sequence to form a shallow groove 3;

[0052] The joints between the first side wall 31, the second side wall 32 and the third side wall 33 are all partially rounded, with a rounding radius of 1 / 2 the depth of the shallow groove 3. The local rounding can reduce the local stress level and prevent stress concentration.

[0053] Figure 5 The figure shows the shallow groove and velocity triangle distribution diagram of the back of the centrifugal impeller according to an embodiment of the present invention. Figure 5 As shown, in some embodiments, the raised rib wall is a straight blade or a curved blade;

[0054] The raised rib wall includes a raised rib wall first end 34 and a raised rib wall second end 35, wherein the raised rib wall first end 34 is connected to the second side wall 32, and the raised rib wall second end 35 is connected to the third side wall 33;

[0055] The second end 35 of the raised rib wall is wider than the first end 34 of the raised rib wall.

[0056] Figure 8 FIG. 1 shows a schematic diagram of a curved shallow groove according to an embodiment of the present invention. Figure 8 As shown, when the raised ribs are curved blades, their inlet blade angle deflects toward the rotational side, essentially aligning with the relative velocity W0 of the bleed air inlet, thus reducing the bleed air's angle of attack loss. Under conditions of consistent bleed air flow, the geometric shape of the raised ribs between adjacent shallow grooves 3 has little effect on the work performed by the Coriolis force.

[0057] Although the above description uses the example of straight blades and curved blades as examples of the raised ribs formed by the shallow grooves 3 on the back of the impeller disk, the present invention is not limited thereto. The raised ribs can be of various shapes, such as an arcuate shape. Those skilled in the art can make comprehensive considerations based on the principles of the present invention and actual application situations, as long as the principles of the present invention can be implemented.

[0058] When the shallow groove 3 is a straight shallow groove, the raised rib wall is a straight blade; when the shallow groove 3 is a curved shallow groove, the raised rib wall is a curved blade.

[0059] Although the above description uses straight or curved shallow grooves as examples, the present invention is not limited thereto. The shallow grooves 3 can be of various types, such as having a deep outer diameter and a shallow inner diameter (to reduce centrifugal force and increase lifespan). Those skilled in the art can make comprehensive considerations based on the principles of the present invention and actual application scenarios, and any design that can implement the principles of the present invention will suffice.

[0060] Figure 7 FIG. 2 shows a cross-sectional schematic diagram of a centrifugal impeller according to an embodiment of the present invention. Figure 7 As shown, in some embodiments, the inner diameter of the disc back of the centrifugal impeller 1 is 167 mm, and the outer diameter of the disc back is 425 mm.

[0061] In some embodiments, the inner diameter of the shallow groove 3 is 1.1 to 1.3 times the inner diameter of the back of the centrifugal impeller 1 .

[0062] In some embodiments, the outer diameter of the shallow groove 3 is 0.85 to 0.985 times the outer diameter of the back of the centrifugal impeller 1 .

[0063] The radial distance between the outer and inner diameters of shallow groove 3 determines the area where the rib grooves increase airflow swirl, thereby affecting the extent to which the impeller back cavity pressure is reduced. The outer diameter is limited to 0.985 of the disc back outer diameter, given the need for a certain thickness between the rib grooves and the outer edge of the disc. The inner diameter of shallow groove 3 should be slightly higher than the disc center.

[0064] In some embodiments, the axial distance between the back side of the centrifugal impeller 1 and the stator 2 is 2 to 6 mm. The centrifugal impeller 1 is a rotating component, and there is a gap between it and the stator 2 to prevent collision and friction.

[0065] The axial distance between the back rotating side of the centrifugal impeller disc (outside the raised rib wall of the shallow groove 3) and the right stator component 2 is controlled at 2 to 6 mm to reduce the radial inward leakage of radial inward flow through the axial gap between the raised rib wall and the stator component 2, thereby ensuring the ability of the Coriolis force to work on the raised rib wall of the adjacent shallow groove 3.

[0066] In some embodiments, the depth of the shallow groove 3 is 1 to 4 mm. The deeper the groove, the more significant the pressure reduction effect. However, considering the strength factor, the depth of the shallow groove 3 is in the range of 1 to 4 mm.

[0067] The Coriolis force can do work on the raised rib wall of the adjacent shallow groove 3. The work capacity of the Coriolis force is related to the circumferential projection area of the raised rib wall of the shallow groove 3 (the area depends on the inner and outer diameters of the shallow groove 3 and the depth of the shallow groove 3). The specific parameter value needs to be determined according to the actual engine design requirements.

[0068] In some embodiments, the top and bottom ends of the second side wall 32 and the third side wall 33 are rounded, and the rounding radius is 1 / 2 of the depth of the shallow groove 3. Local rounding reduces the local stress level and prevents stress concentration.

[0069] The intersection of the shallow groove 3 and the inner disk surface of the centrifugal impeller 1 is also provided with a chamfer, which plays a guiding role for the airflow entering and exiting the shallow groove.

[0070] The radial disc cavity air induction velocity triangle is as follows Figure 5 shown.

[0071] Subscript 0: air induction parameters at the outlet root of centrifugal impeller 1;

[0072] Subscript 1: represents the cross-sectional parameters of the impeller back cavity air inlet;

[0073] Subscript 2: represents the cross-sectional parameters of the impeller back cavity bleed air outlet;

[0074] C: absolute velocity; U: velocity involved in the rotating coordinate system; W: relative velocity.

[0075] The present invention designs a technical solution of opening shallow grooves on the back circumference of the impeller disc, such as Figure 4 and Figure 5 As shown, a circle of shallow grooves 3 are opened upward on the back of the centrifugal impeller disk. When the centrifugal impeller 1 rotates, the relative velocity W (relative to the coordinate system) of the bleed air flow in the shallow grooves 3 is perpendicular to the center of rotation. Since the flow rate of the engine bleed air is very small compared to the flow area of the shallow grooves 3, the relative velocity W is also very small. According to the law of vector composition, the absolute velocity C in the absolute coordinate system is basically consistent with the entrainment velocity U, that is, the swirl coefficient of the airflow in the shallow grooves 3 on the back of the centrifugal impeller disk is equal to 1 (equal to the tangential velocity of the local radius of the centrifugal impeller disk). This can increase the radial pressure drop of the bleed air in the impeller disk back cavity, reduce the average cavity pressure of the impeller back cavity, and thus reduce the forward axial force of the rotor of the engine.

[0076] At the same time, the right-hand rule can be used to determine that the direction of the Coriolis force of the radial inflow of the centrifugal impeller back cavity is perpendicular to the paper surface and outward (such as Figure 7 As shown), that is, the Coriolis force generated by the radial inward flow of the bleed air pushes the convex rib wall of the adjacent shallow groove 3 on the back of the impeller disk to do work (as shown Figure 6 As shown in the figure, the bleed air can work on the impeller back cavity, which can reduce the power loss of the engine and realize the bleed air pre-cooling.

[0077] Taking a centrifugal impeller with an outer diameter of 425 mm as an example, the CFD numerical verification of the technical solution of the present invention was carried out. The results showed that the arrangement of multiple shallow grooves 3 (depth 3 mm) on the back circumference of the centrifugal impeller 1 improved the swirl coefficient of the radial inward flow ( Figure 9 , Figure 9 (a) is a schematic diagram of the swirl coefficient without shallow grooves. Figure 9 (b) is a schematic diagram of the swirl coefficient of the straight shallow groove. Figure 9 (c) is a schematic diagram of the swirl coefficient of a curved shallow groove). Figure 9 (b) Straight shallow groove and Figure 9 (c) The swirl coefficient of the impeller back cavity with curved shallow grooves is further improved compared to the scheme without shallow grooves, reaching 1, and the circumferential velocity of the airflow is equivalent to the local tangential velocity of the impeller. Multiple shallow grooves 3 (depth 3mm) are set on the back circumference of the centrifugal impeller 1, and the radial pressure drop of the impeller back cavity increases (static pressure coefficient CP = local static pressure / bleed air inlet static pressure, used to measure the local static pressure. The smaller the value, the greater the radial pressure drop and the lower the static pressure at the inner diameter. Figure 10 , Figure 10 (a) is a schematic diagram of the static pressure coefficient of the disc cavity without shallow grooves. Figure 10 (b) is a schematic diagram of the static pressure coefficient of the disc cavity of the straight shallow groove. Figure 10(c) is a schematic diagram of the static pressure coefficient of the disc cavity with curved shallow grooves). The static pressure coefficient of the straight shallow groove bleed air outlet is reduced from 0.75 to 0.45 compared with the scheme without shallow grooves. The static pressure coefficient of the curved shallow groove bleed air outlet is further reduced to 0.4 based on the straight shallow groove scheme. A plurality of shallow grooves 3 (depth 3mm) are set on the back circumference of the centrifugal impeller 1 to achieve pre-cooling of the impeller back cavity bleed air ( Figure 11 , Figure 11 (a) is a schematic diagram of the absolute total temperature of the back cavity without shallow grooves. Figure 11 (b) is a schematic diagram of the absolute total temperature of the back cavity of the straight shallow groove. Figure 11 (c) is a schematic diagram of the absolute total temperature of the back cavity of the curved shallow groove (unit: K). In the straight shallow groove scheme, the airflow does the most work on the impeller, so the bleed air temperature drops the most, and the absolute total temperature is the lowest among all schemes, at 691K. The airflow in the curved shallow groove does 18.3 kW of work on the impeller, and the absolute total temperature of the bleed air is 710K. In the conventional scheme without shallow grooves, the circumferential speed of the centrifugal impeller is higher than the circumferential speed of the bleed air flow. The impeller does work on the bleed air flow, and the airflow has a temperature rise. The absolute total temperature of the outlet airflow reaches 860K.

[0078] Table 1 shows the calculation result parameters. The impeller disc back shallow groove design technology scheme recovers 18 to 22 kW of cold air power, achieves bleed air pre-cooling of about 100K, and can reduce the forward axial force of the impeller back cavity by about 20%. The impeller disc back shallow groove 3 reduces the weight of the centrifugal impeller 1 part by 4.5 to 6%.

[0079] Table 1 CFD numerical verification calculation results

[0080]

[0081] The present invention proposes an air induction structure with shallow grooves on the back of a centrifugal impeller disk. By arranging shallow grooves 3 circumferentially on the back of the centrifugal impeller 1, the Coriolis force of the radial inward flow air can perform positive work on the raised rib walls of the shallow grooves 3 on the back of the impeller disk, thereby reducing the power loss of the engine and achieving air pre-cooling. At the same time, the air flow of the air is constrained by the shallow grooves 3, and the circumferential swirl of the air flow in the shallow grooves 3 is 1, which can reduce the average cavity pressure of the impeller back cavity and reduce the forward axial force of the rotor of the engine. In addition, the circumferential shallow grooves 3 on the back of the impeller disk can reduce the weight of the centrifugal impeller to a certain extent and improve the power-to-weight ratio / thrust-to-weight ratio of the engine.

[0082] In the description of the embodiments of the present invention, it should be understood that the terms "inside" and "outside" and the like 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 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 a limitation on the invention.

[0083] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified with "first," "second," etc., may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0084] The terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0085] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An air entrainment structure with shallow grooves on the back of a centrifugal impeller disk, characterized in that: include: A centrifugal impeller (1), a stator (2) and a shallow groove (3); The centrifugal impeller (1) is provided with a plurality of shallow grooves (3) on the circumference of the back of the disc; The centrifugal impeller (1) rotates around a central axis, and a stator (2) is provided on the right side; The shallow groove (3) comprises a first side wall (31), a second side wall (32) and a third side wall (33); The first side wall (31) is a raised rib wall; The second side wall (32) and the third side wall (33) are arc-shaped, the second side wall (32) is shorter than the third side wall (33), and the third side wall (33) is located outside the second side wall (32); The first side wall (31), the second side wall (32), the first side wall (31) and the third side wall (33) are connected in sequence to form a shallow groove (3); The shallow groove (3) is a straight shallow groove or a curved shallow groove; The inner diameter of the shallow groove (3) is 1.1 to 1.3 times the inner diameter of the back of the centrifugal impeller (1); The outer diameter of the shallow groove (3) is 0.85 to 0.985 times the outer diameter of the back of the centrifugal impeller (1); The depth of the shallow groove (3) is 1-4 mm.

2. The centrifugal impeller disc with shallow groove air entrainment structure according to claim 1, characterized in that: The number of the shallow grooves (3) is 10 to 30.

3. The air entrainment structure of the centrifugal impeller disc with shallow grooves according to claim 1, characterized in that: The raised rib walls are straight blades or curved blades; The raised rib wall comprises a raised rib wall first end (34) and a raised rib wall second end (35), wherein the raised rib wall first end (34) is connected to the second side wall (32), and the raised rib wall second end (35) is connected to the third side wall (33); The second end (35) of the raised rib wall is wider than the first end (34) of the raised rib wall.

4. The air entrainment structure of the centrifugal impeller disc with shallow grooves according to claim 3, characterized in that: The inner diameter of the disc back of the centrifugal impeller (1) is 167 mm, and the outer diameter of the disc back is 425 mm.

5. The centrifugal impeller disc with shallow groove air entrainment structure according to claim 1, characterized in that: The axial distance between the back side of the centrifugal impeller (1) and the stator (2) is 2 to 6 mm.

6. The centrifugal impeller disc with shallow groove air entrainment structure according to claim 1, characterized in that: The top and bottom ends of the second side wall (32) and the third side wall (33) are rounded, and the rounding radius is 1 / 2 of the depth of the shallow groove (3).

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