Front-mounted centrifugal impeller cover

Abstract

The invention relates to the technical field of small and medium-sized aero-engine compressors, and particularly discloses a front-mounted centrifugal impeller cover which comprises a flaring-shaped cover body, a mounting flange is arranged on the outer wall of the flaring head of the cover body, a protrusion is arranged on the outer wall of the flaring tail of the cover body, and a limiting step is arranged at the position, close to the flaring tail, of the protrusion. The inner wall of the middle of the cover body is provided with a pressure-stabilizing anti-scraping cavity. The front-mounted centrifugal impeller cover can be suitable for application occasions where the requirement for gaps of small and medium-sized aero-engine compressor centrifugal impellers is high, the requirement for compact structure and portability is high, assembly and disassembly are convenient, the requirement for process wrench space is harsh, the requirement for heat dissipation of centrifugal impeller outlets is high, the requirement for deformation coordination control is high, and the requirement for safety and stability is high.

Description

Technical Field

[0001] The invention relates to the technical field of small and medium-sized aircraft engine compressors, in particular to a front-mounted centrifugal impeller cover. Background Art

[0002] The impeller covers of existing small and medium-sized compressors are mostly installed in the middle or at the rear. Fig.11 and Fig.12 . The central installation structure has relatively uniform deformation along the flow channel and relatively good heat dissipation at the hot and cold ends. However, under the same conditions, the natural frequency is relatively low and the risk of critical passing is relatively high. Due to factors such as the structural limitations of the matching connecting casing, its overall mass is generally relatively large, and there are relatively more disassembly and assembly related parts. The risk of scraping is better than that of the rear installation structure, but worse than that of the front installation structure.

[0003] The post-installation structure has a smaller outlet deformation and a smaller error in the calculation of the outlet clearance. The cold end has better heat dissipation, while the hot end has poorer heat dissipation. However, under the same conditions, the overall mass is also relatively large, and the risk of scraping is greater. For this reason, the post-installation structure with elastic structure is common, such as Fig.13 shown. Summary of the invention

[0004] The purpose of the present invention is to provide a front-mounted centrifugal impeller cover, which can be used in applications where the requirements for the size limit of the rear part of the impeller cover are relatively high, the structure requires to be relatively compact and light, the assembly and disassembly requires to be relatively convenient and flexible, the heat dissipation requirements of the centrifugal impeller outlet are high, the deformation coordination control requirements are good, and the safety and reliability requirements are high.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A front-mounted centrifugal impeller cover comprises a flared cover body, the outer wall of the flared head of the cover body is provided with a mounting flange, the outer wall of the flared tail of the cover body is provided with a protrusion, the protrusion is smoothly connected to the outer wall of one end of the cover body close to the mounting flange through a concave arc surface, the protrusion is provided with a limiting step near the flared tail, and the middle inner wall of the cover body is provided with a pressure-stabilizing and scratch-proof cavity.

[0007] In a further solution, the height of the protrusion is smaller than the height of the limiting step.

[0008] In a further embodiment, the protrusion is an arc-shaped protrusion or a trapezoidal protrusion, and the concave arc surface is formed between one inclined surface of the trapezoidal protrusion and the outer wall of the cover body by chamfering, the trapezoidal protrusion and the upper end surface of the limiting step are connected through another inclined surface of the trapezoidal protrusion, the concave arc surface is formed between one side of the arc-shaped protrusion and the outer wall of the cover body, and the other side of the arc-shaped protrusion is connected to the limiting step through an arc surface.

[0009] In a further solution, the pressure-stabilizing and scratch-resistant cavity cross-section layer includes a wear-resistant scratch layer, a warning layer and a base layer arranged in sequence, the wear-resistant scratch layer is used to generate friction with the turbine blades, and the warning layer is used to issue a warning after the wear-resistant scratch layer is worn.

[0010] In a further solution, the thickness of the warning layer is 0.02-0.15 mm, and the thickness of the wear-resistant scratch layer is 0.62±0.04 mm.

[0011] In a further solution, the pressure-stabilizing and scratch-proof cavity has a drainage surface at one end close to the limiting step, and a wide angle a is formed between the drainage surface and the vertical surface, and the wide angle a is smaller than a tail angle b of the pressure-stabilizing and scratch-proof cavity.

[0012] In a further embodiment, the wide angle a has an angle range of 10±2°.

[0013] In a further solution, a limiting notch is provided on the outer wall of the flared head of the cover body, and the limiting notch is located at an end of the cover body away from the limiting step.

[0014] In a further solution, the mounting flange has a waist-shaped mounting hole, and the aperture of one end of the waist-shaped mounting hole is larger than the aperture of the other end.

[0015] In a further solution, the end with a larger aperture of the waist-shaped mounting hole has a notch; the mounting flange and the outer wall of the flared head are smoothly connected by a circular arc; the mounting flange and the outer wall of the flared head are smoothly connected by a circular arc.

[0016] Beneficial effects of the present invention:

[0017] The present invention can make the rear end of the impeller cover freely connected by installing the mounting flange in front, so that the rear end (hot end) heat dissipation is better, and the surge margin is increased to a certain extent. The flared design can make the drainage and pressure diffusion effect of the intake air good. The tail protrusion can effectively coordinate and control the overall thermal deformation of the cover body, reduce the complexity of the tail structure, and optimize the dynamic characteristics of the impeller cover. The limit step can be mutually abutted with the corresponding structure on the matching casing, thereby limiting the backward displacement of the entire centrifugal impeller cover and the extension size of the thermal deformation of the tail end. Through the setting of the pressure-stabilizing and scratch-proof concave cavity, the inter-leaf gap between the impeller cover and the impeller is appropriately slightly increased, and the gap between the impeller cover and the centrifugal impeller at medium and low speeds can be increased, the surge margin at medium and low speeds can be improved, and the medium and low speeds, especially the critical passing pressure, are guaranteed to be stable; when the design task speed is reached, the cavity disappears, thereby ensuring the preset (gap state) performance at high speeds. Moreover, when local friction occurs, due to the setting of the wear-resistant scratch layer of the pressure-stabilizing and scratch-proof concave cavity, its wear resistance can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces 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 creative work.

[0019] Figure 1 is a three-dimensional schematic diagram of a front-mounted centrifugal impeller cover in an embodiment of the present invention;

[0020] Figure 2 is a schematic axial cross-sectional view of a front-mounted centrifugal impeller cover in an embodiment of the present invention;

[0021] Figure 3 1 is an enlarged schematic diagram of the voltage-stabilizing and scratch-proof cavity at the beginning and the end in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the connection at the drainage surface in an embodiment of the present invention;

[0023] Figure 5 It is a partial cross-sectional schematic diagram of the voltage-stabilizing and scratch-proof cavity in an embodiment of the present invention;

[0024] Figure 6 is a schematic diagram of installing a mounting flange in an embodiment of the present invention;

[0025] Figure 7 is a front view schematic diagram of a front mounted centrifugal impeller cover along the axial direction of the engine in an embodiment of the present invention;

[0026] Figure 8 is a schematic diagram of a mounting flange with a notch in an equivalent embodiment of the present invention;

[0027] Fig. 9 It is a front view schematic diagram of a front mounted centrifugal impeller cover in the related art viewed along the axial direction of the engine;

[0028] Fig.10 is a partial schematic diagram of two arc-shaped protrusions c and d in some embodiments of the present invention;

[0029] Fig.11 It is a schematic diagram of a rear mounted centrifugal impeller cover in the related art;

[0030] Fig.12 It is a schematic diagram of a centrally mounted centrifugal impeller cover in the related art;

[0031] Fig.13 It is a schematic diagram of a centrifugal impeller cover with a rear elastic structure in the related art;

[0032] Fig.14is a schematic diagram of an axial cross section of a front mounted centrifugal impeller cover in the related art;

[0033] In the figure: 1. mounting flange; 10. waist-shaped mounting hole; 101. notch; 2. protrusion; 3. limiting step; 4. pressure-stabilizing and scratch-proof cavity; 41. wear-resistant scratch layer; 42. warning layer; 43. base layer; 5. drainage surface; 6. limiting notch. DETAILED DESCRIPTION

[0034] 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.

[0035] like Figure 1 As shown, a front mounted centrifugal impeller cover comprises a flared cover body, a scratch and abrasion resistant layer, and a warning layer. The outer wall of the flared head of the cover body is provided with a mounting flange 1, and the outer wall of the flared tail of the cover body is provided with a protrusion 2. The protrusion 2 is smoothly connected to the outer wall of the cover body near the mounting flange 1 through a concave arc surface, as shown in FIG. Figure 2 As shown, the protrusion 2 has a limiting step 3 near the expanded tail, and the middle inner wall of the cover body has a pressure-stabilizing and scratch-proof cavity 4.

[0036] See also Figure 1 and Figure 2 As shown, the flared cover body can facilitate airflow diversion, and the mounting flange 1 can be used for quick installation of the front end of the cover body. This front-mounted fixation can make the rear end free and not restricted by fixation, and the deformation compensation space is increased, which increases the surge margin to a certain extent. The rear end can prevent the tail of the wheel cover from moving too much by the limiting step 3, and the main dimensions of the tail, such as the installation dimension and the working dimension, are well restricted to avoid scraping and friction between the tail and the impeller when the centrifugal blade cover is deformed by heat. The strength of the tail of the cover body can be enhanced by the protrusion 2, and the deformation of the tail of the cover body can be reduced. At the same time, it does not affect other dynamic characteristics and can also increase the thrust characteristics to a certain extent. The pressure-stabilizing and scratch-proof cavity 4 can increase the deformation margin of the middle part of the impeller cover, increase the distance between the impeller and the impeller, and strengthen the passage of air intake. Once friction with the impeller occurs, its wear-resistant coating can also improve the wear resistance. The pressure-stabilizing and scratch-proof cavity is set in the middle part. When working at high temperature, the two ends of the cover body are respectively limited by the mounting flange 1 and the limit step 3, and the gap between the middle part of the cover body and the impeller is reduced. The setting of the pressure-stabilizing and scratch-proof cavity 4 can compensate for the reduced gap value to the greatest extent.

[0037] Those skilled in the art should also appreciate that the cross-sectional view of the front mounted centrifugal impeller cover can also be as follows: Fig.14As shown, the tail end is set to be wedge-shaped, but the limiting ability of this shape is insufficient, and the tail end diffusion effect is also insufficient.

[0038] According to the above working principle, some example structures or implementations are provided, and the height of the protrusion 2 is less than the height of the limiting step 3. In this way, when the tail of the cover body deforms or moves backward, the limiting step 3 can first contact with the corresponding structure on the casing to limit the deformation size of the tail, and prevent the gap with the impeller tip from increasing. Because the limiting step 3 is L-shaped, the deformation direction of the impeller cover can be well limited, so that it moves vertically or away from the impeller, and friction with the impeller is avoided to the greatest extent.

[0039] In some embodiments, the protrusion 2 may be an arc-shaped protrusion, such as Fig.10 As shown in the partial examples of the two arc-shaped protrusions shown in Figures c and 10d, one side of the arc-shaped protrusion forms a concave arc surface with the outer wall of the housing, and the other side of the arc-shaped protrusion is connected to the limiting step 3 through an arc surface. Figure 2 As shown, the protrusion 2 is a trapezoidal protrusion, one inclined surface of the trapezoidal protrusion and the outer wall of the housing body form a concave arc surface through rounding, and the trapezoidal protrusion is connected to the upper end surface of the limiting step 3 through another inclined surface of the trapezoidal protrusion. This can facilitate the passage of air flow and avoid turbulence.

[0040] like Figure 5 As shown, the cross-sectional layer at the voltage-stabilizing and scratch-proof cavity 4 includes a wear-resistant scratch layer 41, a warning layer 42 and a base layer 43 arranged in sequence. The wear-resistant scratch layer 41 is used to generate friction with the turbine blades, and the warning layer 42 is used to issue a warning after the wear-resistant scratch layer 41 is worn. The wear-resistant scratch layer 41 is used to improve its wear resistance, and the setting of the warning layer 42 makes it easy to observe and issue a warning in time. In order to improve the installability of the impeller cover and accommodate the scraping and running-in caused by accumulated errors and insufficient concentricity, this three-layer structure is more conducive to coordinated deformation uniformity and is also conducive to sulfuric acid anode hardening of the coating.

[0041] The thickness of the warning layer 42 is 0.02-0.15 mm, and the thickness of the wear-resistant scratch layer 41 is 0.62±0.04 mm. Such thickness does not affect the weight of the cover body, and can enable the cover body to undergo controlled benign deformation.

[0042] like Figure 4 As shown, the pressure stabilizing and scratch-proof cavity 4 has a drainage surface 5 at one end near the limiting step 3, and there is a wide angle a between the drainage surface 5 and the vertical surface, and the wide angle a is smaller than the tail angle b of the pressure stabilizing and scratch-proof cavity 4. The structure of the wide angle a has a certain contraction rectification and pressure expansion effect, which can enhance the dynamic characteristics of the compressor.

[0043] The angular range of the wide angle a is 10 ± 2°. This angular range has a good effect of expanding and compressing the flow. It can avoid the situation that when the wide angle is too large, the clearance between the limiting step 3 and the impeller is too small, which is prone to excessive deformation and wear between the impeller and the impeller after high temperature, and when the wide angle is too small, the effect of guiding and expanding the flow cannot be achieved.

[0044] As Figure 2 shown, there is a limiting notch 6 on the outer wall of the flared head of the cover body. The limiting notch 6 is located at one end of the cover body away from the limiting step 3. The limiting notch 6 can be used for further assembly and limiting with the casing and the like.

[0045] As Figure 7 shown, the mounting flange 1 has a kidney-shaped mounting hole 10, and the aperture at one end of the kidney-shaped mounting hole 10 is larger than that at the other end. The aperture of the larger-diameter end is larger than the maximum dimension of the mounting surface of the mounting bolt. After the larger-diameter end passes through the maximum dimension of the mounting surface of the mounting bolt or the maximum dimension of the mounting tool first, then rotate the cover body so that the screw rod is located at the smaller-diameter end, and then tighten the nut through the tool, which can avoid the need to use a specific tool to drive the screw rod to align with the mounting hole on the casing, facilitating the assembly of the cover body.

[0046] As Figure 8 , there is a notch 101 at the larger-diameter end of the aperture of the kidney-shaped mounting hole 10; the mounting flange 1 and the outer wall of the flared head are smoothly connected by an arc. The notch 101 can make it more convenient for the nut or the pin part to enter.

[0047] Refer to Figure 7 shown, the mounting flange can be integrally arranged with the cover body itself in a uniformly distributed or non-uniformly distributed form. Generally, the radial edge thickness dm satisfies 2 < dm < 2R, where R is the radius of the smaller-diameter end hole of the kidney-shaped mounting hole. In addition, the kidney-shaped mounting hole is convenient for alignment and has a good misalignment prevention effect, and more base material with mass can be cut and removed.

[0048] When using the conventional impeller cover mounting edge as Fig. 9 shown, it is often limited by the structure of the impeller cover itself and often requires the use of shorter mounting bolts, or as Figure 6 shown, a professional special tool is used for disassembly and assembly. When disassembling and assembling, it is necessary to move the current position indicated by the dotted line contour backward to the solid line part to avoid interference of the mounting bolt, but the movement limit is very small. The short bolts not only reduce part of the connection strength, but also the disassembly and assembly operations of the special tool complicate the relevant process procedures.

[0049] By adopting the scheme of the present invention, the bolt can be installed first, then the impeller cover is screwed in, and then the bolt is tightened. This not only ensures the connection strength but also simplifies the use of the special tool.

[0050] To ensure that there are no reverse steps between adjacent parts of the flow channel impeller, when adjusting the clearance of the compressor impeller, it is often necessary to move the installation position of the impeller cover backward by a certain amount. However, excessive backward movement may cause a certain degree of scraping risk. And by adopting the present invention as Figure 2The structure of the tail limit step 3 shown has a one-way limit function, which can effectively prevent the impeller cover from excessive displacement during installation, and to a certain extent avoid the risk of insufficient flushness, impeller cover impeller scraping and jamming due to calculation and processing errors. On the other hand, since the structure adopts a one-way limit structure, sufficient deformation margin is retained in the axial forward direction. When small-scale surge, eccentric scraping, etc. occur, the entire compressor still has a high safety reliability.

[0051] Since the temperature changes along the flow path, the compressor intake gradually increases along the flow path. Under the same expansion coefficient, the deformation of each microelement segment is different. If a non-uniform wall thickness design is used to prevent deformation, the cumulative error of deformation calculation is large, and the calculation and machining process are complicated. The use of the protrusion at the tail of the present invention can not only better control the overall deformation, but also optimize the dynamic characteristics of the impeller cover to a certain extent.

[0052] The voltage-stabilizing and scratch-resistant cavity structure of the present invention is as follows: Figure 3 As shown. At medium and low speeds, the surge margin is improved to a certain extent, and the smoothness of critical passing is improved. For centrifugal compressors, when other conditions are the same, the larger the gap, the higher the surge margin, and the easier it is to pass the critical smoothly. The inlet height of the pressure-stabilizing and scratch-proof cavity is generally D1 = 0.13 ± 0.02mm, and the outlet height of the pressure-stabilizing and scratch-proof cavity is generally D2 = 0.33 ± 0.02mm. The size of the base layer 43 depends on the design task. The bottom warning layer 42 is generally 0.02-0.15mm, and the scraping and abrasion containment layer is generally 0.62 ± 0.04mm.

[0053] like Figure 5 As shown, this voltage-stabilizing and scratch-proof cavity structure can also change its shape to adjust the gap between the impeller cover and the impeller through the different expansion coefficients of different materials in the wear-resistant scratch layer 41, the early warning layer 42 and the base layer 43 at its cross-section. For example, the material of the scratch-resistant layer 41 can be an aluminum silicon layer, and the material of the base layer 43 can be stainless steel. The two materials have different linear expansion coefficients. At low speeds, a tiny annular cavity is formed between the impeller cover and the impeller, which improves the surge margin and the smoothness of the critical pass. As the speed increases, the cavity gradually decreases due to the difference in linear expansion coefficients. When the design task speed is reached, the cavity disappears, thereby ensuring the preset (clearance state) performance at high speeds.

[0054] like Figure 4 As shown, the invention relates to a wide angle a structure of the tail drainage surface 5. It has a certain contraction rectification and pressure expansion effect. Generally, the wide angle A is set to be 10±2°, and the tail drainage wide angle A should be smaller than the tail angle of the pressure stabilizing and scratch-proof cavity structure.

[0055] Through the above comparison and description, it can be concluded that the present invention has the following significant improvements:

[0056] 1. More compact and lightweight structural design features;

[0057] 2. Easier, more convenient and feasible disassembly and assembly features;

[0058] 3. Limit control of scraping caused by process errors, etc., and the front installation form, the flange installation edge radius is smaller and the rigidity is better;

[0059] 4. Higher one-way safety margin;

[0060] 5. Higher deformation control margin;

[0061] 6. Meet certain surge and anti-scratch safety requirements;

[0062] 7. Meet certain requirements for steady flow and performance;

[0063] 8. Certain deformation coordination, multi-layer structure combined with stability characteristics.

[0064] It should be noted that the terms "first", "second", etc. in this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so as to describe the embodiments of the present application described here.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0066] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A front mounted centrifugal impeller cover, characterized in that: The invention comprises a flared cover body, wherein the outer wall of the flared head of the cover body is provided with a mounting flange (1), the outer wall of the flared tail of the cover body is provided with a protrusion (2), the protrusion (2) is smoothly connected to the outer wall of one end of the cover body close to the mounting flange (1) through a concave arc surface, the protrusion (2) is provided with a limiting step (3) near the flared tail, and the middle inner wall of the cover body is provided with a pressure-stabilizing and scratch-resistant cavity (4).

2. A front mounted centrifugal impeller cover according to claim 1, characterized in that: The height of the protrusion (2) is smaller than the height of the limiting step (3).

3. A front mounted centrifugal impeller cover according to claim 1, characterized in that: The protrusion (2) is an arc-shaped protrusion or a trapezoidal protrusion, and the concave arc surface is formed between one inclined surface of the trapezoidal protrusion and the outer wall of the cover body by chamfering, and the trapezoidal protrusion is connected to the upper end surface of the limiting step (3) through another inclined surface of the trapezoidal protrusion, and the concave arc surface is formed between one side of the arc-shaped protrusion and the outer wall of the cover body, and the other side of the arc-shaped protrusion is connected to the limiting step (3) through an arc surface.

4. A front mounted centrifugal impeller cover according to claim 1, characterized in that: The cross-sectional layer of the voltage-stabilizing and scratch-resistant cavity (4) comprises a wear-resistant scratch layer (41), a warning layer (42) and a base layer (43) which are arranged in sequence, wherein the wear-resistant scratch layer (41) is used to generate friction with turbine blades, and the warning layer (42) is used to issue a warning after the wear-resistant scratch layer (41) is worn.

5. A front mounted centrifugal impeller cover according to claim 4, characterized in that: The thickness of the warning layer (42) is 0.02-0.15 mm, and the thickness of the wear-resistant scratch layer (41) is 0.62±0.04 mm.

6. A front mounted centrifugal impeller cover according to claim 1, characterized in that: The pressure-stabilizing and scratch-proof concave cavity (4) has a drainage surface (5) at one end close to the limiting step (3), and a wide angle a is formed between the drainage surface (5) and the vertical surface, and the wide angle a is smaller than a tail angle b of the pressure-stabilizing and scratch-proof concave cavity (4).

7. A front mounted centrifugal impeller cover according to claim 6, characterized in that: The wide angle a has an angle range of 10±2°.

8. The front mounted centrifugal impeller cover according to claim 1, characterized in that: A limiting notch (6) is provided on the outer wall of the flared head of the cover body, and the limiting notch (6) is located at an end of the cover body away from the limiting step (3).

9. The front mounted centrifugal impeller cover according to claim 1, characterized in that: The mounting flange (1) has a waist-shaped mounting hole (10), and the diameter of one end of the waist-shaped mounting hole (10) is larger than the diameter of the other end.

10. A front mounted centrifugal impeller cover according to claim 9, characterized in that: The end of the waist-shaped mounting hole (10) with a larger hole diameter is provided with a notch (101); the mounting flange (1) is smoothly connected to the outer wall of the flared head through an arc.

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