A closed centrifugal impeller with a double-sided irregular notch structure

Abstract

This invention discloses a closed centrifugal impeller with a double-sided irregular notch structure. A notch is provided on the edge of the impeller cover at the air outlet between every two adjacent blades, and a notch is provided on the edge of the impeller disk at the air outlet between every two adjacent blades. The projection shape of the notch on the disk completely covers the shape of the notch on the disk. Based on the edge line of the cover, the radial depth of the notch is less than or equal to 18% of the impeller radius; based on the edge line of the disk, the radial depth of the notch is less than or equal to 12% of the impeller radius. This structure reduces the mass of the closed centrifugal impeller, decreases its rotational inertia, and lowers the static stress level caused by centrifugal loads. This results in good vibration characteristics for the closed centrifugal impeller, with high first-order vibration frequencies at the '0' node diameter and '1' node diameter, and good fatigue resistance.

Description

Technical Field

[0001] This invention belongs to the field of centrifugal compressors and relates to closed centrifugal impellers, specifically to a closed centrifugal impeller with a double-sided irregular notch structure. Background Technology

[0002] Centrifugal compressors have wide applications in aerospace, metallurgy, petrochemicals, environmental protection, and pharmaceuticals. A centrifugal compressor works on gas through a high-speed rotating impeller. Within the flow channels of the impeller and diffuser, it utilizes centrifugal pressure boosting and deceleration diffusion to convert mechanical energy into gas pressure energy.

[0003] The impeller is the most critical component in a centrifugal compressor, and its reliability directly affects the safe and stable operation of the entire unit. During operation, the impeller is subjected not only to centrifugal loads but also to airflow-induced vibration loads. With the increasing size and speed of impeller structures, the stress on the impeller structure rises, while rigidity decreases with increasing size. This easily induces airflow-induced vibration, leading to impeller vibration fatigue. Therefore, higher requirements are placed on the design of the impeller's structural dynamic characteristics.

[0004] The prior art discloses a serrated disc wind turbine impeller, the purpose of which is to reduce the rotational inertia of the wind turbine impeller. However, its applicability is significantly limited, mainly as follows: (A) This patent only implements the serrated disc on the disc itself, without making structural optimization designs for the disc cover; (B) The patent states that "the leading edge of the serrations is parallel to the blades," indicating that the serrations are only applicable to impeller structures with straight blades. If the blades are curved or spatially twisted, this cannot be implemented; (C) This patent only qualitatively indicates an increase in impeller life, but does not provide quantitative analysis to give optimization results, and cannot provide relatively accurate "notch" shapes, implementation schemes, or better impeller structural dimensions. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a closed centrifugal impeller with a double-sided irregular notch structure, which solves the technical problem that the existing impellers are prone to airflow vibration due to insufficient rigidity, resulting in short fatigue life of the impeller.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A closed centrifugal impeller with a double-sided irregular notch structure includes a disc, blades and a cover, with multiple blades disposed between the disc and the cover. A notch is provided on the edge of the cover at the impeller outlet between every two adjacent blades, and a notch is provided on the edge of the disc at the impeller outlet between every two adjacent blades.

[0008] The projection shape of the wheel cover notch on the wheel disc completely covers the shape of the wheel disc notch;

[0009] With the edge line of the wheel cover as a reference, the radial depth of the wheel cover notch is less than or equal to 18% of the impeller radius; with the edge line of the wheel disk as a reference, the radial depth of the wheel disk notch is less than or equal to 12% of the impeller radius.

[0010] The present invention also has the following technical features:

[0011] The profile of the wheel cover notch is composed of a tangentially connected oblique line segment, a first small radius arc segment, and a first large radius arc segment along the impeller rotation direction; the profile of the wheel disk notch is composed of a tangentially connected second large radius arc segment and second small radius arc segment along the impeller rotation direction.

[0012] If the baseline is set as a radial straight line with an inner angle of 41.5° to the oblique line segment of the wheel cover notch and passing through the center of the impeller, then the profile of the wheel cover notch and the profile of the wheel disc notch have the following constraints:

[0013] The distance from the starting point of the disc notch to the baseline is 71 / 260 of the impeller radius, and the difference between the distance from the starting point of the disc notch to the baseline and the distance from the starting point of the wheel cover notch to the baseline is 20 / 260 of the impeller radius.

[0014] The radius of the first small radius arc segment is 40 / 260 of the impeller radius, the radius of the first large radius arc segment is 40 / 260 of the impeller radius; the radius of the second large radius arc segment is 145 / 260 of the impeller radius, and the radius of the second small radius arc segment is 30 / 260 of the impeller radius.

[0015] The distance from the center of the first small radius arc segment to the baseline is 117 / 260; the distance from the center of the first large radius arc segment to the baseline is 121 / 260; the distance from the center of the second small radius arc segment to the baseline is 132 / 260; the distance between the projection of the center of the second small radius arc segment onto the baseline and the projection of the starting point of the wheel notch onto the baseline is 13 / 260.

[0016] The wheel cover notch and the edge of the wheel cover are smoothly transitioned by rounded corners; the wheel disc notch and the edge of the wheel disc are smoothly transitioned by rounded corners.

[0017] The wheel cover has multiple identical wheel cover notches, and the wheel disc has multiple identical wheel disc notches.

[0018] The closed centrifugal impeller is either a welded impeller structure or an integrally milled impeller structure.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] (I) This invention features multiple notches corresponding to the edges of the impeller cover and the impeller disk, respectively. The projection shape of these notches onto the impeller cover completely covers the shape of the notches themselves. This structure reduces the mass of the closed-type centrifugal impeller, decreases its moment of inertia, and lowers the static stress level caused by centrifugal loads. This results in good vibration characteristics for the closed-type centrifugal impeller, with high first-order vibration frequencies at both the '0' and '1' section diameters, and good fatigue resistance.

[0021] (II) The closed centrifugal impeller with double-sided irregular notch structure does not change the connection method between the impeller and the main shaft, nor does it change the assembly process of the impeller.

[0022] (III) Closed impellers are widely used in centrifugal compressors. The blades on the impellers include straight blades, circular arc blades, and spatially twisted blades. This invention aims to provide a toothed closed impeller applicable to all blade types. Finite element simulation results show that it can effectively enhance the rigidity of the impeller structure, thereby improving the fatigue life of the impeller. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the closed centrifugal impeller with a double-sided irregular notch structure of the present invention.

[0024] Figure 2 This is a front view schematic diagram of the closed centrifugal impeller with a double-sided irregular notch structure according to the present invention.

[0025] Figure 3 This is a schematic diagram of the blade distribution on the wheel cover of the present invention.

[0026] Figure 4 This is a schematic diagram of the blade distribution on the wheel of the present invention.

[0027] Figure 5 for Figure 2 The enlarged structural diagram at point A is a schematic diagram of the layout of the wheel cover notch and the wheel cover notch of the present invention.

[0028] Figure 6 The stress cloud diagram is for the closed centrifugal impeller with a double-sided irregular notch structure in Example 1.

[0029] Figure 7 The first mode shape cloud diagram (side front view of the impeller cover) of the closed centrifugal impeller model with double-sided irregular notch structure in Example 1 is shown at the '0' pitch diameter.

[0030] Figure 8 The first mode shape cloud diagram (side front view of the impeller) of the closed centrifugal impeller model with double-sided irregular notch structure in Example 1 is shown at the '0' pitch diameter.

[0031] Figure 9 The stress cloud diagram is for the conventional closed centrifugal impeller of Comparative Example 1.

[0032] Figure 10 The first mode shape contour diagram (side front view of the impeller cover) of the conventional closed centrifugal impeller model with '0' pitch diameter is shown in Comparative Example 1.

[0033] Figure 11 The first mode shape contour diagram (side front view of the impeller) of the conventional closed centrifugal impeller model with '0' pitch diameter is shown in Comparative Example 1.

[0034] Figure 12 The stress contour plot is for the closed centrifugal impeller with a double-sided isomorphic notch structure in Comparative Example 2.

[0035] Figure 13 The first mode shape contour diagram (side front view of the impeller cover) of the closed centrifugal impeller model with a double-sided isomorphic notch structure is shown for Comparative Example 2, with a pitch diameter of '0'.

[0036] Figure 14 The stress cloud diagram is for the closed centrifugal impeller with a double-sided isomorphic notch structure in Comparative Example 3.

[0037] Figure 15 The first mode shape contour diagram (side front view of the impeller cover) of the closed centrifugal impeller model with a double-sided isomorphic notch structure is shown for Comparative Example 3 at the '0' pitch diameter.

[0038] Figure 16 The stress contour plot is for the closed centrifugal impeller with a double-sided isomorphic notch structure in Comparative Example 4.

[0039] Figure 17 The first mode shape contour diagram (side front view of the impeller cover) of the closed centrifugal impeller model with a double-sided isomorphic notch structure in Comparative Example 4 is shown below.

[0040] The meanings of the labels in the diagram are as follows: 1-disc, 2-blade, 3-disc cover, 4-disc cover notch, 5-disc notch, 6-baseline, 7-disc notch start point, 8-disc cover notch start point;

[0041] 401 - oblique line segment, 402 - first small radius arc segment, 403 - first large radius arc segment;

[0042] 501 - Second largest radius arc segment; 502 - Second smallest radius arc segment;

[0043] O is the impeller center, Oxy is the coordinate system, and Oy is the baseline corresponding to one of the notches;

[0044] R is the impeller radius, and θ is the inner angle between the baseline and the oblique line segment of the impeller cover notch.

[0045] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0046] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0047] Example 1:

[0048] This embodiment provides a closed centrifugal impeller with a double-sided irregular notch structure, such as Figures 1 to 5 As shown, it includes a disc 1, blades 2 and a cover 3. Multiple blades 2 are arranged between the disc 1 and the cover 3. A cover notch 4 is provided on the edge of the cover 3 at the impeller outlet between each pair of adjacent blades 2. A disc notch 5 is provided on the edge of the disc 1 at the impeller outlet between each pair of adjacent blades 2.

[0049] The projection shape of the wheel cover notch 4 onto the wheel disc 1 completely covers the shape of the wheel disc notch 5;

[0050] With the edge line of the wheel cover 3 as a reference, the radial depth of the wheel cover notch 4 is less than or equal to 18% of the impeller radius; with the edge line of the wheel disk 1 as a reference, the radial depth of the wheel disk notch 5 is less than or equal to 12% of the impeller radius.

[0051] Furthermore, the projection shape of the wheel cover notch 4 on the wheel disk 1 completely covers the shape of the wheel disk notch 5, that is, the projection area of ​​the wheel cover notch 4 on the wheel disk 1 is larger than the projection area of ​​the wheel disk notch 5 on the wheel disk 1, and the projection of the profile of the wheel cover notch 4 on the wheel disk 1 does not coincide with the profile of the wheel disk notch 5.

[0052] As a specific embodiment, the profile of the wheel cover notch 4 is composed of a tangential connection of a diagonal line segment 401, a first small radius arc segment 402, and a first large radius arc segment 403 along the impeller rotation direction; the profile of the wheel disk notch 5 is composed of a tangential connection of a second large radius arc segment 501 and a second small radius arc segment 502 along the impeller rotation direction.

[0053] As a preferred embodiment, the baseline 6 is set to be a radial straight line with an inner angle of 41.5° with the oblique line segment 401 of the wheel cover notch 4 and passing through the center of the impeller. Then, the profile of the wheel cover notch 4 and the profile of the wheel disc notch 5 have the following constraints:

[0054] The distance from the starting point 7 of the wheel disc notch to the baseline 6 is 71 / 260 of the impeller radius, and the difference between the distance from the starting point 7 of the wheel disc notch to the baseline 6 and the distance from the starting point 8 of the wheel cover notch to the baseline 6 is 20 / 260 of the impeller radius.

[0055] The radius of the first small radius arc segment 402 is 40 / 260 of the impeller radius, the radius of the first large radius arc segment 403 is 40 / 260 of the impeller radius; the radius of the second large radius arc segment 501 is 145 / 260 of the impeller radius, and the radius of the second small radius arc segment 502 is 30 / 260 of the impeller radius.

[0056] The distance from the center of the first small radius arc segment 402 to the baseline 6 is 117 / 260; the distance from the center of the first large radius arc segment 403 to the baseline 6 is 121 / 260; the distance from the center of the second small radius arc segment 502 to the baseline 6 is 132 / 260; the distance between the projection of the center of the second small radius arc segment 502 onto the baseline 6 and the projection of the starting point 7 of the wheel notch onto the baseline is 13 / 260.

[0057] As a preferred embodiment, the wheel cover notch 4 and the edge of the wheel cover 3 are smoothly transitioned by rounded corners; the wheel disc notch 5 and the edge of the wheel disc 1 are smoothly transitioned by rounded corners.

[0058] As a preferred embodiment, the multiple wheel cover notches 4 provided on the wheel cover 3 have the same structure, and the multiple wheel disc notches 5 provided on the wheel disc 1 have the same structure.

[0059] As a preferred embodiment, the closed centrifugal impeller is a welded impeller structure or an integrally milled impeller structure.

[0060] In the closed centrifugal impeller with a double-sided irregular notch structure of the present invention, the number of blades, the number of impeller cover notches 4, and the number of impeller disc notches 5 are equal. The impeller cover notches 4 and the impeller disc notches 5 correspond one-to-one.

[0061] Comparative Example 1:

[0062] This comparative example presents a conventional closed centrifugal impeller, which differs from the closed centrifugal impeller with a double-sided irregular notch structure in Example 1 only in that the impeller cover notch 4 and the impeller disc notch 5 are absent in this comparative example.

[0063] Comparative Example 2:

[0064] This embodiment provides a closed centrifugal impeller with a double-sided identical notch structure. The only difference between this impeller and the closed centrifugal impeller with a double-sided irregular notch structure in Embodiment 1 is that the shape of the wheel cover notch 4 in this comparative example is exactly the same as the shape of the wheel disk notch 5. That is, the projection shape of the wheel cover notch 4 on the wheel disk 1 completely coincides with the shape of the wheel disk notch 5. Both adopt the shape of the wheel cover notch 4 defined in Embodiment 1. That is, the profile is composed of a tangential connection of a diagonal line segment 401, a first small radius arc segment 402 and a first large radius arc segment 403 along the impeller rotation direction.

[0065] Comparative Example 3:

[0066] This embodiment provides a closed centrifugal impeller with a double-sided identical notch structure. The only difference between this impeller and the closed centrifugal impeller with a double-sided irregular notch structure in Embodiment 1 is that the shape of the wheel cover notch 4 in this comparative example is exactly the same as the shape of the wheel disk notch 5. That is, the projection shape of the wheel cover notch 4 on the wheel disk 1 completely coincides with the shape of the wheel disk notch 5. Both adopt the shape of the wheel disk notch 5 defined in Embodiment 1. That is, the profile is composed of the second largest radius arc segment 501 and the second smallest radius arc segment 502 connected tangentially along the impeller rotation direction.

[0067] Comparative Example 4:

[0068] This embodiment provides a closed centrifugal impeller with a double-sided identical notch structure. The only difference between this impeller and the closed centrifugal impeller with a double-sided irregular notch structure in Embodiment 1 is that the shape of the wheel cover notch 4 in this comparative example is exactly the same as the shape of the wheel disk notch 5, that is, the projection shape of the wheel cover notch 4 on the wheel disk 1 completely coincides with the shape of the wheel disk notch 5.

[0069] In this comparative example, the profile of the disc notch 5 is composed of oblique line segments and circular arc segments along the impeller rotation direction. The baseline 6 is defined as a radial straight line passing through the impeller center, with an internal angle of 41.5° to the oblique line segment 401 of the wheel cover notch 4. The profiles of the wheel cover notch 4 and the disc notch 5 are subject to the following constraints: the distance from the starting point 7 of the disc notch to the baseline 6 is 36 / 260 of the impeller radius; the radius of the circular arc segment is 40 / 260 of the impeller radius; and the distance from the center of the circular arc segment to the baseline 6 is 127 / 260.

[0070] Effect comparison and verification:

[0071] Modal analysis was conducted on a closed centrifugal impeller to study the first-order mode shape contour plot at the '0' pitch diameter. The closed centrifugal impeller has an impeller radius of 260 mm and employs 19 circular arc blades.

[0072] The stress cloud diagram of the closed centrifugal impeller with double-sided irregular notch structure in Example 1 is as follows: Figure 6 As shown, the first-order mode shape contour diagram of the '0' node diameter is as follows: Figure 7 and Figure 8 As shown. The stress contour diagram of the traditional closed centrifugal impeller in Comparative Example 1 is as follows. Figure 9 As shown, the first-order mode shape contour diagram of the '0' node diameter is as follows: Figure 10 and Figure 11 As shown.

[0073] from Figures 6 to 11As can be seen, the maximum stress Von Mises of the closed centrifugal impeller with double-sided irregular notch structure of the present invention is 503.53 MPa, which is 10.52% lower than the stress of 562.74 MPa of the conventional closed centrifugal impeller in Comparative Example 1; the frequency of the first mode shape of the '0' pitch diameter of the closed centrifugal impeller of the present invention is 1128.8 Hz, which is 3.6% higher than the frequency of 1089.1 Hz of the conventional closed centrifugal impeller in Comparative Example 1.

[0074] The comparative analysis of Embodiment 1 and Comparative Example 1 shows that the closed centrifugal impeller with a double-sided irregular notch structure of the present invention can effectively reduce the stress level of the impeller structure, and at the same time, effectively increase the frequency of the first-order vibration mode of the 0' pitch diameter of the impeller structure. This increases the excitation difficulty of the impeller structure, thereby improving the fatigue life of the impeller.

[0075] like Figures 6 to 8 As shown, the finite element simulation results of Example 1 show that the maximum Von Mises stress of the impeller is 503.53 MPa, and the frequency of the first mode of vibration of the '0' pitch diameter is 1128.8 Hz.

[0076] like Figures 12 to 13 As shown, the finite element simulation results of Comparative Example 2 show that the maximum Von Mises stress of the impeller is 524.99 MPa, and the frequency of the first mode shape of the '0' pitch diameter is 1139.8 Hz.

[0077] like Figures 14 to 15 As shown, the finite element simulation results of Comparative Example 3 show that the maximum Von Mises stress of the impeller is 492.25 MPa, and the frequency of the first mode of vibration of the '0' pitch diameter is 1115.6 Hz.

[0078] like Figures 16 to 17 As shown, the finite element simulation results of Comparative Example 4 show that the maximum Von Mises stress of the impeller is 513.11 MPa, and the frequency of the first mode of vibration of the '0' pitch diameter is 1071.6 Hz.

[0079] As can be seen from the comparison between Example 1 and Comparative Examples 2 to 4, in Comparative Example 2, the frequency of the first mode shape with the '0' node diameter increased the most, but the stress was also high; in Comparative Example 3, the stress level was low, but the frequency increase of the first mode shape with the '0' node diameter was not significant, and the effect was not obvious; in Comparative Example 4, the stress level was low, and the frequency of the first mode shape with the '0' node diameter did not increase, but instead decreased.

Claims

1. A closed centrifugal impeller with a double-sided irregular notch structure, comprising a disc (1), blades (2), and a cover (3), wherein multiple blades (2) are disposed between the disc (1) and the cover (3), characterized in that, A notch (4) is provided on the edge of the impeller cover (3) at the air outlet of each two adjacent blades (2), and a notch (5) is provided on the edge of the impeller disc (1) at the air outlet of each two adjacent blades (2). The projection shape of the wheel cover notch (4) on the wheel disk (1) completely covers the shape of the wheel disk notch (5); With the edge line of the wheel cover (3) as a reference, the radial depth of the wheel cover notch (4) is less than or equal to 18% of the impeller radius; with the edge line of the wheel disk (1) as a reference, the radial depth of the wheel disk notch (5) is less than or equal to 12% of the impeller radius. The profile of the wheel cover notch (4) is composed of a tangential connection of a diagonal line segment (401), a first small radius arc segment (402), and a first large radius arc segment (403) along the impeller rotation direction; the profile of the wheel disk notch (5) is composed of a tangential connection of a second large radius arc segment (501) and a second small radius arc segment (502) along the impeller rotation direction. If the baseline (6) is set to be a radial straight line with an inner angle of 41.5° with the oblique line segment (401) of the wheel cover notch (4) and passing through the center of the impeller, then the profile of the wheel cover notch (4) and the profile of the wheel disk notch (5) have the following constraints: The distance from the starting point (7) of the wheel rim opening to the baseline (6) is 71 / 260 of the impeller radius, and the difference between the distance from the starting point (7) of the wheel rim opening to the baseline (6) and the distance from the starting point (8) of the wheel cover opening to the baseline (6) is 20 / 260 of the impeller radius. The radius of the first small radius arc segment (402) is 40 / 260 of the impeller radius, and the radius of the first large radius arc segment (403) is 40 / 260 of the impeller radius; the radius of the second large radius arc segment (501) is 145 / 260 of the impeller radius, and the radius of the second small radius arc segment (502) is 30 / 260 of the impeller radius; The distance from the center of the first small radius arc segment (402) to the baseline (6) is 117 / 260; the distance from the center of the first large radius arc segment (403) to the baseline (6) is 121 / 260; the distance from the center of the second small radius arc segment (502) to the baseline (6) is 132 / 260; the distance between the projection of the center of the second small radius arc segment (502) onto the baseline (6) and the projection of the starting point (7) of the wheel notch onto the baseline is 13 / 260; The wheel cover notch (4) and the edge of the wheel cover (3) are smoothly transitioned by rounded corners; the wheel disc notch (5) and the edge of the wheel disc (1) are smoothly transitioned by rounded corners; The multiple wheel cover notches (4) provided on the wheel cover (3) have the same structure, and the multiple wheel disc notches (5) provided on the wheel disc (1) have the same structure; The closed centrifugal impeller is either a welded impeller structure or an integrally milled impeller structure.

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