Circumferentially non-uniform casing, method of designing the same, compressor, aeroengine

Abstract

The application discloses a circumferential non-uniform casing, a design method thereof, a compressor and an aero-engine. The design method of the circumferential non-uniform casing comprises the following steps: according to the variation of the tip clearance in the circumferential direction of a circumferential uniform casing, a first circular arc segment is drawn in the region with the largest tip clearance reduction amount and has a radius greater than that of the circumferential uniform casing, a second circular arc segment is drawn in the region with the largest tip clearance increase amount and has a radius smaller than that of the circumferential uniform casing, the first circular arc segment and the second circular arc segment are connected through a smooth arc segment to form a closed ring structure, and the size of the closed ring structure is used as the circumferential cross-sectional size of the inner wall of the circumferential non-uniform casing. The circumferential non-uniform casing is designed so that the rotor tip clearance distribution in each circumferential direction is more uniform during engine operation, the inter-stage leakage flow can be controlled, the circumferential distortion is reduced, and the compressor efficiency and the compressor surge margin are improved.

Description

Technical Field

[0001] This invention relates to the field of aviation technology, and in particular to a circumferentially non-uniform compressor casing and its design method, a compressor, and an aero-engine. Background Technology

[0002] In actual production, compressor casings are typically designed and manufactured into a circular structure, forming a circumferentially uniform casing. During aero-engine operation, due to the combined effects of gravity, centrifugal force, and aerodynamic heat on the compressor rotor blades, the elongation of the blades at different circumferential positions within the compressor casing is inevitably non-uniform. This results in non-uniform blade tip clearance at different circumferential positions within the compressor casing during engine operation, leading to localized excessive clearance. This increases interstage leakage and circumferential airflow distortion, ultimately reducing compressor efficiency and surge margin. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects in the prior art and provide a circumferential non-uniform compressor casing and its design method, a compressor, and an aero engine.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] This invention provides a method for designing a circumferentially non-uniform casing, comprising the following steps:

[0006] S1. Determine the variation of the blade tip clearance in the circumferential direction of the uniformly circumferential casing;

[0007] S2. Based on the change in the blade tip clearance in the circumferential direction of the circumferentially uniform casing, with the center position of the circumferentially uniform casing as the reference center, draw a first arc segment at the position corresponding to the first region with the largest decrease in blade tip clearance, and draw a second arc segment at the position corresponding to the second region with the largest increase in blade tip clearance. The radius of the first arc segment is larger than the radius of the circumferentially uniform casing, and the radius of the second arc segment is smaller than the radius of the circumferentially uniform casing.

[0008] S3. Connect the first circular arc segment and the second circular arc segment with a smooth arc segment to form a closed ring structure;

[0009] S4. Using the dimensions of the closed annular structure as the circumferential cross-sectional dimensions of the inner wall of the circumferentially non-uniform casing, a circumferentially non-uniform casing is manufactured.

[0010] In this scheme, when designing a non-circumferentially uniform casing, based on the variation in blade tip clearance in the circumferential direction of the circumferentially uniform casing, the radius of the region corresponding to the largest decrease in blade tip clearance in the circumferentially non-uniform casing is increased, and the radius of the region corresponding to the largest increase in blade tip clearance in the circumferentially non-uniform casing is decreased. This optimizes the rotor blade tip clearance distribution, making the rotor blade tip clearance distribution more uniform in each circumferential direction during engine operation. This enables more effective control of interstage leakage flow, effectively reduces circumferential distortion, and improves compressor efficiency and compressor surge margin.

[0011] Preferably, step S1 includes: determining the variation of the blade tip clearance in the circumferential direction of the circumferential uniform casing by conducting a blade tip clearance measurement test using the circumferential uniform casing or by using numerical simulation calculation results.

[0012] In this scheme, the variation of blade tip clearance in the circumferential direction of the circumferentially uniform casing is obtained through experiments. The design results are more accurate through experimental data analysis. The blade tip clearance distribution is more uniform and the effect is better when the designed circumferentially non-uniform casing is in operation. The variation of blade tip clearance in the circumferential direction of the circumferentially uniform casing is determined through numerical simulation calculation results, which is faster and cheaper.

[0013] Preferably, when the test obtains the blade tip clearance change data, step S1 includes spraying a coating uniformly on the inner wall of the circumferential casing, analyzing the amount of coating scraping on the inner wall of the circumferential casing, and judging the change of blade tip clearance by the amount of coating scraping; step S2 includes assigning the area with the largest amount of coating scraping to the first area and the area with the smallest amount of coating scraping to the second area.

[0014] In this scheme, by uniformly spraying a coating on the inner wall of the casing in the circumferential direction, the change in blade tip clearance is judged by the amount of coating scraping. The operation is simple and can more intuitively determine the change in blade tip clearance at different positions. The area with the largest amount of coating scraping corresponds to the first area, and the area with the smallest amount of coating scraping corresponds to the second area. This can accurately correspond the area with the largest amount of coating scraping to the first area with the largest decrease in blade tip clearance, and the area with the smallest amount of coating scraping to the second area with the largest increase in blade tip clearance, thereby increasing or decreasing the radius at the corresponding position.

[0015] Preferably, in step S3, the smooth arc segment is tangent to the connection point of the first arc segment and / or the second arc segment.

[0016] In this design, the smooth arc segment is tangent to the connection point of the first and / or second circular arc segments, thereby ensuring a smooth inner wall of the non-uniform casing and facilitating airflow. Furthermore, this structural arrangement effectively reduces stress concentration, thus improving the strength of the circumferentially non-uniform casing.

[0017] Preferably, the circumferential cross-sectional dimensions of the casing inner wall corresponding to different stages of rotor blades are designed according to steps S1-S4.

[0018] In this scheme, the circumferential cross-sectional dimensions of the inner wall of the casing corresponding to different stages of rotor blades are designed according to steps S1-S4, and a circumferentially non-uniform casing with a multi-stage structure can be designed according to the above design method.

[0019] Preferably, the circumferentially non-uniform casings corresponding to different stages of rotor blades include: a front-stage circumferentially non-uniform casing corresponding to the front-stage rotor blades, an intermediate-stage circumferentially non-uniform casing corresponding to the intermediate rotor blades, and a rear-stage circumferentially non-uniform casing corresponding to the rear-stage rotor blades, wherein the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the front-stage circumferentially non-uniform casing is less than the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the rear-stage circumferentially non-uniform casing.

[0020] In this scheme, since centrifugal force plays a major role in the change of blade tip clearance of the preceding rotor blades, and aerodynamic heat plays a major role in the change of blade tip clearance of the following rotor blades, the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the preceding circumferential non-uniform casing is less than the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the following circumferential non-uniform casing. This makes the blade tip clearance distribution more uniform in the circumferential direction of the entire circumferential non-uniform casing, thereby improving the overall performance of the casing.

[0021] Preferably, the increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the pre-stage circumferentially non-uniform casing is greater than the increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the post-stage circumferentially non-uniform casing.

[0022] In this scheme, the centrifugal force plays a major role in the change of blade tip clearance of the front rotor blades, while aerodynamic heat plays a major role in the change of blade tip clearance of the rear rotor blades. This makes the increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the front circumferential non-uniform casing greater than the increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the rear circumferential non-uniform casing. This further makes the blade tip clearance distribution more uniform in the circumferential direction of the entire circumferential non-uniform casing, thereby further improving the performance of the entire casing.

[0023] Preferably, the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the pre-stage circumferentially non-uniform casing corresponding to the pre-stage rotor blade is 0.05~0.1mm; the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the intermediate stage circumferentially non-uniform casing corresponding to the intermediate rotor blade is 0.1~0.2mm; and the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the rear stage circumferentially non-uniform casing corresponding to the rear stage rotor blade is 0.2~0.3mm.

[0024] In this scheme, by combining the variation of the blade tip clearance in the circumferential direction of the uniform casing, the amount of reduction in the radius of the second arc segment is determined, which can effectively ensure that the blade tip clearance is in an optimal state during operation.

[0025] Preferably, the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the pre-stage circumferentially non-uniform casing corresponding to the pre-stage rotor blade is 0.1~0.15mm; the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the intermediate stage circumferentially non-uniform casing corresponding to the intermediate rotor blade is 0.05~0.1mm; and the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the rear stage circumferentially non-uniform casing corresponding to the rear stage rotor blade is 0.05~0.1mm.

[0026] In this scheme, by combining the change in the blade tip clearance in the circumferential direction of the uniform casing, the increase in the radius of the first arc segment is determined, which can further ensure that the blade tip clearance is in an optimal state during operation.

[0027] Preferably, the first region is located in the range of 270°-0° of the circumferential cross section of the circumferentially uniform casing, and the second region is located in the range of 90°-180° of the circumferential cross section of the circumferentially uniform casing.

[0028] The present invention also provides a circumferentially non-uniform casing, which is a circumferentially non-uniform casing designed using the above-described circumferentially non-uniform casing design method.

[0029] In this design, the circumferentially non-uniform casing can make the circumferential blade tip gap distribution more uniform during operation.

[0030] Preferably, the circumferential non-uniform casing includes a pre-stage circumferential non-uniform casing, an intermediate-stage circumferential non-uniform casing, and a post-stage circumferential non-uniform casing, and the pre-stage circumferential non-uniform casing, intermediate-stage circumferential non-uniform casing, and post-stage circumferential non-uniform casing are integrated into one structure.

[0031] This scheme enables the production of a circumferentially non-uniform casing with a multi-level structure.

[0032] The present invention also provides a compressor comprising the aforementioned circumferentially non-uniform casing.

[0033] The present invention also provides an aircraft engine comprising the above-described compressor.

[0034] The positive and progressive effects of this invention are as follows: Based on the variation of the blade tip clearance in the circumferential direction of the circumferentially uniform casing, a first arc segment with a radius greater than that of the circumferentially uniform casing is drawn in the region where the blade tip clearance decreases the most, and a second arc segment with a radius smaller than that of the circumferentially uniform casing is drawn in the region where the blade tip clearance increases the most. The first and second arc segments are connected by a smooth arc segment to form a closed ring structure. The size of the closed ring structure is used as the circumferential cross-sectional size of the inner wall of the circumferentially non-uniform casing. This results in a circumferentially non-uniform casing, which makes the rotor blade tip clearance distribution more uniform in each circumferential direction when the engine is working. This allows for more effective control of interstage leakage flow, effectively reduces circumferential distortion, and improves compressor efficiency and compressor surge margin. Attached Figure Description

[0035] Figure 1 A flowchart illustrating a circumferentially non-uniform casing design method according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the circumferential cross-section of a uniformly circumferentially oriented casing.

[0037] Figure 3 This is a schematic diagram of the circumferential cross-section of a non-uniform circumferential casing.

[0038] Figures 4A-4C The amount of coating scraping is shown for the front stage, intermediate stage and rear stage of a multi-stage axial compressor.

[0039] Explanation of reference numerals in the attached figures

[0040] Circumferential uniform casing 1

[0041] Circumferential non-uniform casing 2

[0042] Area 3

[0043] Second Zone 4 Detailed Implementation

[0044] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments.

[0045] Existing compressor casings are typically designed and manufactured to form a circumferentially uniform casing, meaning their circumferential cross-section is circular, such as... Figure 2 As shown; under engine operating conditions, this circumferentially uniform casing with uneven blade tip distribution around its circumference can cause localized excessive clearance, increasing interstage leakage and circumferential airflow distortion. To address this, as... Figure 1 As shown, the present invention provides a circumferentially non-uniform casing design method, comprising the following steps:

[0046] S1. Determine the variation of the blade tip clearance in the circumferentially uniform casing in one circumferential direction;

[0047] S2. Based on the change of blade tip clearance in the circumferential direction of the uniform casing 1, with the center of the uniform casing 1 as the reference center, draw a first arc segment at the position corresponding to the first region 3 where the blade tip clearance decreases the most, and draw a second arc segment at the position corresponding to the second region 4 where the blade tip clearance increases the most. The radius of the first arc segment is larger than the radius of the uniform casing 1, and the radius of the second arc segment is smaller than the radius of the uniform casing 1.

[0048] S3. Connect the first circular arc segment and the second circular arc segment with a smooth arc segment to form a closed loop structure;

[0049] S4. Using the dimensions of the closed annular structure as the circumferential cross-sectional dimensions of the inner wall of the circumferentially non-uniform casing 2, fabricate the circumferentially non-uniform casing 2.

[0050] In this embodiment, the change in tip clearance of the circumferentially uniform casing 1 is obtained through multi-stage axial compressor component testing. A coating is sprayed onto the inner wall of the circumferentially uniform casing 1, and the amount of coating abrasion on the inner wall of the circumferentially uniform casing 1 is analyzed. The change in tip clearance is determined by the amount of coating abrasion. Of course, in other embodiments, the change in tip clearance of the circumferentially uniform casing 1 can be obtained by other means, such as determining the change in tip clearance of the circumferentially uniform casing 1 through numerical simulation calculations.

[0051] In this embodiment, the circumferential uniform casing includes a front-stage circumferential uniform casing, an intermediate-stage circumferential uniform casing, and a rear-stage circumferential uniform casing. The front-stage circumferential uniform casing, the intermediate-stage circumferential uniform casing, and the rear-stage circumferential uniform casing are the casings corresponding to the front-stage rotor blades, the intermediate rotor blades, and the rear-stage rotor blades, respectively. The front-stage circumferential uniform casing has the largest circumferential cross-sectional dimension, and the rear-stage circumferential uniform casing has the smallest dimension. Figure 4A , 4B The 4C models respectively demonstrate the coating scraping amount of the front-stage circumferential uniform casing, intermediate-stage circumferential uniform casing, and rear-stage circumferential uniform casing of a multi-stage axial compressor at different speeds. Figure 4A , 4B As shown in 4C, the coating scraping amount is the largest in the circumferential uniform casing of the pre-stage, intermediate, and post-stage, and the blade tip clearance decreases the most in this region. The coating scraping amount is the smallest in the circumferential uniform casing of the pre-stage, intermediate, and post-stage, and the blade tip clearance increases the most in this region. The corresponding non-uniform pre-stage casing will be designed based on the coating scraping condition of the pre-stage casing.

[0052] Using the center position of the pre-stage circumferentially uniform casing as the reference center, in the first area corresponding to the largest amount of coating scraping, such as... Figure 4AThe region corresponding to the 270°-0° range on the circumferential cross-section of the pre-stage circumferential uniform casing, and based on the amount of coating scraping on the circumferential uniform casing in this direction, with the radius appropriately increased relative to the radius of the pre-stage circumferential uniform casing, is drawn as the first arc segment. In the second region corresponding to the smaller amount of coating scraping, such as... Figure 4A In the pre-stage circumferentially uniform casing, a second arc segment is drawn within the 90°-180° range of the circumferential cross-section, with a radius appropriately reduced relative to the pre-stage circumferentially uniform casing. A smooth arc segment connects the first and second arc segments to form a closed ring structure. The dimensions of this closed ring structure serve as the circumferential cross-sectional dimensions of the pre-stage circumferentially non-uniform casing's inner wall. Preferably, the smooth arc segment is tangent to the connection point of the first and / or second arc segments, ensuring a smooth inner wall for the non-uniform casing, facilitating airflow, and effectively reducing stress concentration.

[0053] The design of the intermediate stage circumferential non-uniform casing and the subsequent stage circumferential non-uniform casing follows the same steps and will not be repeated here. However, the front stage circumferential non-uniform casing, the intermediate stage circumferential non-uniform casing, and the subsequent stage circumferential non-uniform casing are arranged sequentially along the airflow direction. Since the rotor blades of each stage are subjected to different centrifugal forces and aerodynamic and thermal forces, the increase in the radius of the first arc segment of the circumferential non-uniform casing relative to the circumferential uniform casing, and the decrease in the radius of the second arc segment of the circumferential non-uniform casing relative to the circumferential uniform casing, are all related to the stage in which they are located.

[0054] Since centrifugal force plays a major role in the change of blade tip clearance of the preceding rotor blades, and aerodynamic heat plays a major role in the change of blade tip clearance of the following rotor blades, the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the preceding circumferential non-uniform casing is less than the reduction in radius of the second arc segment on the circumferential cross-section of the inner wall of the following circumferential non-uniform casing. This makes the blade tip clearance distribution more uniform in the circumferential direction of the entire circumferential non-uniform casing, thereby improving the overall performance of the casing.

[0055] Similarly, considering that centrifugal force plays a major role in the change of blade tip clearance of the preceding rotor blades, and aerodynamic heat plays a major role in the change of blade tip clearance of the following rotor blades, the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the preceding circumferential non-uniform casing is greater than the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the following circumferential non-uniform casing. This can further make the blade tip clearance distribution more uniform in the circumferential direction of the entire circumferential non-uniform casing, and further improve the performance of the entire casing.

[0056] Preferably, the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the front-stage non-uniform casing corresponding to the front-stage rotor blade is 0.05~0.1mm; the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the middle-stage non-uniform casing corresponding to the middle rotor blade is 0.1~0.2mm; and the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the rear-stage non-uniform casing corresponding to the rear-stage rotor blade is 0.2~0.3mm, ensuring that the blade tip clearance is in an optimal state during operation.

[0057] Preferably, the radius of the first arc segment on the circumferential cross-section of the inner wall of the front-stage circumferential non-uniform casing corresponding to the front-stage rotor blades increases by 0.1~0.15mm; the radius of the first arc segment on the circumferential cross-section of the inner wall of the intermediate-stage circumferential non-uniform casing corresponding to the intermediate-stage rotor blades increases by 0.05~0.1mm; and the radius of the first arc segment on the circumferential cross-section of the inner wall of the rear-stage circumferential non-uniform casing corresponding to the rear-stage rotor blades increases by 0.05~0.1mm, ensuring that the blade tip clearance is in a better condition during operation.

[0058] The present invention also discloses a circumferentially non-uniform casing 2, which is a circumferentially non-uniform casing 2 designed based on the above-described design method. Figure 3 A schematic diagram of the circumferential cross-section of the circumferentially non-uniform casing 2 is shown. This circumferentially non-uniform casing 2, under operating conditions, enables a more uniform distribution of blade tip clearance in the circumferential direction. The circumferentially non-uniform casing 2 includes a pre-stage circumferentially non-uniform casing, an intermediate-stage circumferentially non-uniform casing, and a post-stage circumferentially non-uniform casing. These three casings are integrated into a single structure, with the pre-stage circumferentially non-uniform casing having the largest circumferential cross-sectional dimension and the post-stage circumferentially non-uniform casing having the smallest dimension.

[0059] The present invention also provides a compressor comprising the aforementioned circumferentially non-uniform casing.

[0060] The present invention also provides an aircraft engine comprising the above-described compressor.

[0061] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A design method for a circumferentially non-uniform casing, characterized in that, Includes the following steps: S1. Determine the variation of the blade tip clearance in the circumferential direction of the uniform casing. Spray a coating on the inner wall of the uniform casing. Analyze the amount of coating scraping on the inner wall of the uniform casing. The area with the largest amount of coating scraping corresponds to the first area, and the area with the smallest amount of coating scraping corresponds to the second area. S2. Based on the change in the blade tip clearance in the circumferential direction of the circumferential uniform casing, with the center position of the circumferential uniform casing as the reference center, draw a first arc segment at the corresponding position of the first region and a second arc segment at the corresponding position of the second region, wherein the radius of the first arc segment is larger than the radius of the circumferential uniform casing, and the radius of the second arc segment is smaller than the radius of the circumferential uniform casing. S3. Connect the first circular arc segment and the second circular arc segment with a smooth arc segment to form a closed ring structure; S4. Using the dimensions of the closed annular structure as the circumferential cross-sectional dimensions of the inner wall of the circumferentially non-uniform casing, a circumferentially non-uniform casing is manufactured.

2. The design method of the circumferentially non-uniform casing as described in claim 1, characterized in that, In step S3, the smooth arc segment is tangent to the connection point of the first arc segment and / or the second arc segment.

3. The design method of the circumferentially non-uniform casing as described in claim 1, characterized in that, The circumferential cross-sectional dimensions of the inner wall of the casing corresponding to different stages of rotor blades are designed according to steps S1-S4.

4. The design method for a circumferentially non-uniform casing as described in claim 3, characterized in that, The circumferential non-uniform casing includes: a front-stage circumferential non-uniform casing corresponding to the front-stage rotor blades, an intermediate-stage circumferential non-uniform casing corresponding to the intermediate-stage rotor blades, and a rear-stage circumferential non-uniform casing corresponding to the rear-stage rotor blades, wherein the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the front-stage circumferential non-uniform casing is less than the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the rear-stage circumferential non-uniform casing.

5. The design method for a circumferentially non-uniform casing as described in claim 4, characterized in that, The increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the pre-stage circumferentially non-uniform casing is greater than the increase in radius of the first arc segment on the circumferential cross-section of the inner wall of the post-stage circumferentially non-uniform casing.

6. The design method of the circumferentially non-uniform casing as described in claim 4, characterized in that, The radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the pre-stage non-uniform casing corresponding to the pre-stage rotor blade is 0.05–0.1 mm; the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the intermediate stage non-uniform casing corresponding to the intermediate stage rotor blade is 0.1–0.2 mm; and the radius reduction of the second arc segment on the circumferential cross-section of the inner wall of the rear stage non-uniform casing corresponding to the rear stage rotor blade is 0.2–0.3 mm.

7. The design method for a circumferentially non-uniform casing as described in claim 5, characterized in that, The radius increase of the first arc segment on the circumferential cross-section of the inner wall of the pre-stage circumferential non-uniform casing corresponding to the pre-stage rotor blade is 0.1–0.15 mm; the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the intermediate stage circumferential non-uniform casing corresponding to the intermediate rotor blade is 0.05–0.1 mm; and the radius increase of the first arc segment on the circumferential cross-section of the inner wall of the rear stage circumferential non-uniform casing corresponding to the rear stage rotor blade is 0.05–0.1 mm.

8. The design method of the circumferentially non-uniform casing as described in claim 1, characterized in that, The first region is located within the 270°-0° range of the circumferential cross section of the circumferentially uniform casing, and the second region is located within the 90°-180° range of the circumferential cross section of the circumferentially uniform casing.

9. A circumferentially non-uniform casing, characterized in that, It is a circumferential non-uniform casing designed using the design method of any one of claims 1-8.

10. The circumferentially non-uniform casing as described in claim 9, characterized in that, The circumferential non-uniform casing includes a pre-stage circumferential non-uniform casing, an intermediate-stage circumferential non-uniform casing, and a post-stage circumferential non-uniform casing, which are integrally formed.

11. A compressor, characterized in that, It includes the circumferentially non-uniform casing as described in any one of claims 9-10.

12. An aircraft engine, characterized in that, It includes the compressor as described in claim 11.

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