Aero-engine high-pressure turbine blade tip clearance control method

Abstract

The invention relates to a blade tip clearance control method for a high-pressure turbine of an aero-engine, and solves the problem that an existing outer ring block theoretical profile determination method only introduces a rotor deflection component and does not consider the influence of coaxiality, so that the optimal solution of a counter-rotor and stator clearance cannot be realized. According to the method, two influence factors including high-pressure rotor deflection and high-pressure rotor rear supporting casing bearing seat coaxiality are introduced, a high-pressure turbine outer ring theoretical profile curve is determined, and therefore the blade tip clearance is controlled; according to the theoretical outer ring curve radius, the value a is calculated according to known conditions, the theoretical runout delta = a-r of the point is obtained, the runout of the n point of the outer ring of the high-pressure turbine is measured according to the repair standard requirement, the angle corresponding to the first point is 360 degrees / n, the theoretical runout values of the n points are calculated through analogy, and the fast theoretical profile of the outer ring of the high-pressure turbine is obtained by connecting the theoretical runout of the n points end to end. By means of the method, rotor and stator collision and abrasion faults can be reduced, and the product repairing quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine manufacturing and maintenance technology, and relates to a method for controlling the tip clearance of high-pressure turbine blades in aero-engines. Background Technology

[0002] In actual maintenance and support of aero engines, rubbing failures between the high-pressure turbine blade tip and the high-pressure turbine outer ring are frequent, causing engine malfunction alarms due to excessive vibration and affecting operation. The root cause of rotor-stator rubbing is the reduction of rotor-stator clearance in pursuit of engine performance. However, due to limitations in rotor-stator clearance control technology, the rotor-stator clearance cannot be adjusted accordingly when the engine's operating conditions change.

[0003] For aero-engines, if the tip clearance of high-pressure turbine blades is reduced in pursuit of engine performance, rotor-stator rubbing is highly likely to occur due to mismatch in the linear expansion ratio of rotor and stator materials, rotor or casing deformation, and poor coaxiality. Severe rubbing can lead to excessive engine vibration. Conversely, if the tip clearance is increased to avoid rotor-stator rubbing, the airflow loss at the blade tips is large, the turbine blade working efficiency is low, and the engine thrust is reduced, which also affects engine operation. Therefore, how to reasonably control the tip clearance of high-pressure turbine blades has become a major challenge in aero-engine repair.

[0004] The rubbing between the rotor and stator of a high-pressure turbine in an engine is related to the rotor-stator clearance, rotor deflection, and coaxiality. Existing methods for determining the theoretical profile of the outer ring block only incorporate the rotor deflection component and do not consider the influence of coaxiality. Therefore, they cannot achieve an optimal solution for the rotor-stator clearance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to introduce two influencing factors: high-pressure rotor deflection and high-pressure rotor rear support casing bearing housing coaxiality, to study and determine the theoretical surface calculation method of high-pressure turbine outer ring, and to develop a set of calculation tools for easy use in production operations.

[0006] The above methods can optimize the blade tip clearance of high-pressure turbines, reduce vibration failures, and maximize engine efficiency.

[0007] This invention is achieved through the following technical solutions:

[0008] A method for controlling the tip clearance of a high-pressure turbine blades in an aero-engine introduces two influencing factors: high-pressure rotor deflection and coaxiality of the high-pressure rotor rear support casing bearing housing. This method determines the theoretical profile curve of the high-pressure turbine outer ring, thereby controlling the tip clearance. The calculation method for the theoretical profile curve of the outer ring is as follows:

[0009] Theoretically, the outer ring of the high-pressure turbine of the engine consists of two semicircles with radius r. The center of the lower semicircle is eccentrically downwards by c. Therefore, the radius of the lower semicircle is R = r + c / 2. The entire high-pressure turbine outer ring is assembled and machined on the main combustion chamber unit. The concentricity eccentricity of the high-pressure turbine relative to the front bearing of the high-pressure rotor is d, and the phase angle is β. The calculation process is as follows:

[0010] In a rectangular coordinate system

[0011] (x-(-c+dcosβ)) 2 +(y-dsinβ) 2 =b 2

[0012] x 2 +2(c-dcosβ)x+(c-dcosβ) 2 +y 2 -2dsinβy+(dsinβ) 2 =b 2

[0013] In polar coordinates

[0014] a 2 =x 2 +y 2

[0015] x = acosα

[0016] y = -acosα

[0017] The theoretical curve for the outer ring block calculated in polar coordinates is as follows:

[0018] a 2 +2(cosα(c-dcosβ)+dsinβcosα)a+(c-dcosβ) 2 +(dsinβ) 2 -b 2 =0

[0019] The theoretical outer loop curve radius corresponds to different β angle radii:

[0020]

[0021] In the above formula, r is given by design, c is the measured value, b = R = r + c / 2, α = 360° / n, the angle of the later point is accumulated from the angle of the previous point, d and β are the given results of coaxiality measurement calculation, the value of a is calculated according to the known conditions, and the theoretical runout δ = ar is obtained at this point. The repair standard requires the measurement of the runout of n points on the outer ring of the high-pressure turbine, so the angle corresponding to the first point is 360° / n, and so on, to calculate the theoretical runout values ​​of n points. Connecting the theoretical runouts of the n points end to end gives the fast theoretical profile of the outer ring of the high-pressure turbine.

[0022] In the above formula, n is taken as 126.

[0023] Generally, the upper boundary of δ is +0.075, and the lower boundary of δ is -0.025.

[0024] This invention comprehensively considers two factors, namely the high-pressure rotor deflection and the coaxiality of the high-pressure rotor rear support casing bearing seat, to determine the theoretical profile of the high-pressure turbine outer ring, reduce rotor-stator rubbing failures, and improve product repair quality. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the engine rotor and fulcrum of the present invention;

[0026] In the diagram, 1-intermediate casing; 2-front bearing of high-pressure rotor; 3-high-pressure rotor; 4-high-pressure turbine blade; 5-outer ring block of high-pressure turbine; 6-rear support roller bearing of low-pressure turbine rotor;

[0027] Figure 2 This is a schematic diagram of the calculation of the high-pressure turbine outer ring theoretical curve considering rotor deflection and casing coaxiality in this invention;

[0028] Figure 3 This is the theoretical outer ring runout curve of the present invention with coaxiality b=0.0;

[0029] Figure 4 This is the theoretical outer ring runout curve of the present invention with coaxiality b = 0.1 and phase angle β = 0°;

[0030] Figure 5 This is the theoretical outer ring runout curve diagram of the present invention with coaxiality b = 0.1 and phase angle β = 90°;

[0031] Figure 6 This is the theoretical outer ring runout curve of the present invention with coaxiality b = 0.1 and phase angle β = 180°;

[0032] Figure 7 This is the theoretical outer ring runout curve of the present invention with coaxiality b = 0.1 and phase angle β = 270°;

[0033] Figure 8 This is a comparison chart of the actual measured values ​​and theoretical values ​​of the outer ring block of the present invention. Detailed Implementation

[0034] The technical problem this invention aims to solve is to introduce two influencing factors—high-pressure rotor deflection and the coaxiality of the high-pressure rotor rear support casing bearing—to study and determine a theoretical calculation method for the outer ring profile of the high-pressure turbine, and to develop a calculation tool for easy use in production operations. This method can optimize the high-pressure turbine blade tip clearance, reduce vibration failures, and maximize engine efficiency.

[0035] This invention is achieved through the following technical solutions:

[0036] 1. Factors affecting high-pressure turbine tip clearance

[0037] like Figure 1 As shown, the high-pressure rotor of the engine has two support points. The front support point is the No. 3 bearing in the intermediate casing. This bearing housing is the reference for measuring the coaxiality of each support point of the engine. The rear support point is the intermediate bearing between the high and low pressure rotors. It is supported on the rear bearing of the low-pressure turbine through the low-pressure turbine shaft. Because the engine rotor is a flexible rotor, it has downward deflection during operation, which will cause the turbine rotor to be eccentric downward relative to the outer ring block of the high-pressure turbine, affecting the rotor-stator clearance.

[0038] Meanwhile, the rear bearing housing of the low-pressure turbine has a certain coaxiality deviation relative to the reference. This deviation will be transmitted to the turbine rotor through components such as the low-pressure turbine shaft, intermediate bearing, and high-pressure turbine, causing the turbine rotor to have a coaxiality deviation relative to the outer ring block of the high-pressure turbine.

[0039] In the actual process of determining the rotor-stator clearance, the tip runout of each blade of the high-pressure turbine rotor relative to the standard rotor radius is first measured, and then the runout of the turbine outer ring block relative to its theoretical curve is measured to calculate the tip clearance in the assembled state. Since the theoretical surface changes with the rotor deflection and coaxiality, the core of controlling the tip clearance is to determine the theoretical radius curve of the outer ring block.

[0040] 2. Calculation method for theoretical outer ring surface curve

[0041] Based on the design specifications and related drawings, the high-pressure turbine outer ring (stator casing) of this type of engine theoretically consists of two semicircles with a radius of r (as specified in the design). The lower semicircle has a downward eccentricity of c = 0.24 mm and a radius of R = r + 0.12 mm. The entire high-pressure turbine outer ring is assembled and machined on the main combustion chamber unit. The concentricity eccentricity of the high-pressure turbine relative to the front bearing of the high-pressure rotor is d, with a phase angle of β. The calculation diagram is shown below. Figure 2 .

[0042] In a rectangular coordinate system

[0043] (x-(-c+dcosβ)) 2 +(y-dsinβ) 2 =b 2

[0044] x 2 +2(c-dcosβ)x+(c-dcosβ) 2 +y 2 -2dsinβy+(dsinβ) 2 =b 2

[0045] In polar coordinates

[0046] a 2 =x 2 +y 2

[0047] x = acosα

[0048] y = -acosα

[0049] The theoretical curve for the outer ring block calculated in polar coordinates is as follows:

[0050] a 2 +2(cosα(c-dcosβ)+dsinβcosα)a+(c-dcosβ) 2 +(dsinβ) 2 -b 2 =0

[0051] The theoretical outer loop curve radius corresponds to different β angle radii:

[0052]

[0053] r = 366.1 (design given), c = 0.24 mm, b = R = r + 0.12, α = 360° / 126 (the angle of the next point is accumulated from the angles of the previous points), d and β are the given results of coaxiality measurement calculation. Based on the known conditions, the value of a can be calculated, and the theoretical runout δ = ar is obtained. The repair standard requires the measurement of the runout of 126 points on the outer ring of the high-pressure turbine. The angle corresponding to the first point is 360° / 126. By analogy, the theoretical runout value of 126 points is calculated. Connecting the first and last theoretical runouts of 126 points gives the theoretical profile of the outer ring of the high-pressure turbine.

[0054] 3. Theoretical runout value of outer ring block

[0055] Calculate the theoretical jump based on different b and β values.

[0056]

[0057] Let δ+0.075 be the upper boundary and δ-0.025 be the lower boundary.

[0058] Use Excel to calculate and plot curves for different coaxiality b and phase angle β, as shown below. Figure 3-7 As shown.

[0059] Verification:

[0060] (I) Calculation of the value of d

[0061] like Figure 1As shown, let the concentricity eccentricity of the low-pressure turbine rear support point relative to the high-pressure rotor front bearing be D, and the phase angle be β. Let the concentricity eccentricity of the high-pressure turbine relative to the high-pressure rotor front bearing be d (illustrated). Figure 1 If the height of the high-pressure turbine blades relative to the front bearing is h, and the height of the low-pressure turbine relative to the front bearing of the high-pressure rotor is H, then...

[0062] (II) Verification by Substituting Measured Values

[0063] Figure 8 The figures show the actual runout measurements of a certain engine. Green represents the theoretical runout (b = 0.1, β = 120°), and red represents the actual runout measured by the outer ring block. It can be seen that additional processing is needed for measurement points 1-57 and 100-126 to ensure that no rubbing occurs in the right-side area. At the same time, the runout of the outer ring block near measurement points 61-95 is too large, and the outer ring block needs to be replaced to ensure that the clearance is minimized in order to meet the engine performance requirements.

[0064] The beneficial effects of this invention are:

[0065] 1. Through this invention, the calculation of engine stator clearance is more reasonable, which can effectively guarantee engine performance parameters, increase thrust by an average of 100 kgf, and effectively improve aircraft performance;

[0066] 2. This invention reduces engine vibration failures caused by rotor-stator rubbing, thus reducing the engine return rate due to vibration failures by up to 50%.

[0067] 3. This invention reduces engine failures due to vibration and performance defects, and increases the first-time test pass rate by 5%.

Claims

1. A method for controlling the tip clearance of a high-pressure turbine blade in an aero-engine, characterized by: introducing... Two influencing factors, high-pressure rotor deflection and high-pressure rotor rear support casing bearing coaxiality, are used to determine the theoretical profile curve of the high-pressure turbine outer ring, thereby controlling the blade tip clearance. The calculation method for the theoretical profile curve of the outer ring is as follows: Theoretically, the outer ring of the high-pressure turbine of the engine consists of two semicircles with radius r. The center of the lower semicircle is eccentrically downwards by c. Therefore, the radius of the lower semicircle is R = r + c / 2. The entire high-pressure turbine outer ring is assembled and machined on the main combustion chamber unit. The concentricity eccentricity of the high-pressure turbine relative to the front bearing of the high-pressure rotor is d, and the phase angle is β. The calculation process is as follows: In a rectangular coordinate system (x-(-c+dcosβ)) 2 +(y-dsinβ) 2 =b 2 x 2 +2(c-dcosβ)x+(c-dcosβ) 2 +y 2 -2dsinβy+(dsinβ) 2 =b 2 In polar coordinates to 2 =x 2 +and 2 x = acosα y = -acosα The theoretical curve for the outer ring block calculated in polar coordinates is as follows: a 2 +2(cosα(c-dcosβ)+dsinβcosα)a+(c-dcosβ) 2 +(dsinβ) 2 -b 2 =0 The theoretical outer loop curve radius corresponds to different β angle radii: In the above formula, r is given by design, c is the measured value, b = R = r + c / 2, α = 360° / n, the angle of the later point is accumulated from the angle of the previous point, d and β are the given results of coaxiality measurement calculation, the value of a is calculated according to the known conditions, and the theoretical runout δ = ar is obtained at this point. The repair standard requires the measurement of the runout of n points on the outer ring of the high-pressure turbine, so the angle corresponding to the first point is 360° / n, and so on, to calculate the theoretical runout values ​​of n points. Connecting the theoretical runouts of the n points end to end gives the fast theoretical profile of the outer ring of the high-pressure turbine.

2. The method for controlling the tip clearance of a high-pressure turbine blade in an aero-engine according to claim 1, characterized in that: n is 126.

3. The method for controlling the tip clearance of a high-pressure turbine blade in an aero-engine according to claim 1, characterized in that: The upper boundary of δ is +0.075, and the lower boundary of δ is -0.025.

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