A guide vane for an air turbine starter with a low excitation frequency

Abstract

The present invention belongs to the field of aerodynamic design of a guide vane, and discloses a guide vane for an air turbine starter with a low excitation frequency. The guide vane has 15 to 20 blades, and all the blades are evenly distributed along the circumference of the guide vane body. The axial chord length of the guide vane is 19 to 20 mm, the geometric inlet angle is 100° to 110°, the geometric outlet angle is 15° to 16°, the leading edge radius is 2.4 to 2.6 mm, the trailing edge radius is 0.3 to 0.4 mm, and the trailing edge turning angle is 5 to 6.5°. The wake excitation frequency of the guide vane of the present invention is lower than the resonance frequency of the turbine blade, completely avoiding the wake excitation problem. Moreover, the cross-sectional parameters of the guide vane blades are reasonably designed, and the use of 17 guide vane blades can meet the pneumatic requirements of the air turbine starter. Compared with the method of using a crowned turbine, etc., the production cost of the present invention is lower and it is suitable for mass production and use.

Description

Technical Field

[0001] The present invention belongs to the field of aerodynamic design of a guide vane, and relates to the design of an air turbine starter, and particularly to a guide vane for a low excitation frequency air turbine starter. Background Art

[0002] An air turbine starter is an important accessory of an engine starting system. Its working principle is to extract the internal energy of a high-temperature and high-pressure gas source and convert it into mechanical shaft power to drive the high-pressure rotor of the engine to a predetermined speed, and it is mainly used for ground starting, cold running, unsealing, oil sealing and false starting of the engine.

[0003] A turbine rotor is an extremely important key component of an air turbine starter, which directly determines the output torque characteristics of the air turbine starter. And the output torque characteristics of the air turbine starter are crucial for the acceleration of the high-pressure rotor of the engine, which in turn affects the control timing of the engine.

[0004] Fluid excitation, especially the wake excitation of the guide vane, is one of the main reasons for the reduction of the fatigue life of the turbine rotor blades and even the fracture of the turbine blades, and is also one of the main factors affecting the safety and service life of the air turbine starter.

[0005] Influence of Guide Vane Blades Figure 4 As shown, the pressure at the outlet of the guide vane is not uniform, and there are alternating high-pressure areas and low-pressure areas. Therefore, the turbine is excited once by the high and low pressure areas every time it rotates through the angle of one blade. The more the number of guide vanes, the more times the turbine blade is excited during one revolution. During each start-up process of the air turbine starter, the turbine accelerates from rest to the target speed. If the number of excitations that the turbine blade experiences during one revolution is the same as or close to the natural resonance frequency of the turbine blade itself, the maximum alternating stress is generated at the leading edge, trailing edge, and back of the blade root.

[0006] Under the action of the resonant alternating stress, a fatigue source is generated at the maximum stress position of the blade root of the turbine blade. With the accumulation of use time, each start-up experiences resonance once, and the blade finally cannot withstand the centrifugal force and breaks instantaneously.

[0007] Reducing the number of guide vane blades can effectively reduce the excitation frequency of the guide vane wake on the turbine blade, but it reduces the overall starting efficiency of the turbine stage (guide vane and turbine), making the air turbine starter not meet the use requirements or have low efficiency.

[0008] Using a guide vane with non-uniform blades or a crowned turbine can also solve this problem, but the production and processing costs of such a guide vane with non-uniform blades and a crowned turbine are extremely high, and it is difficult to use in large quantities in practice. Summary of the Invention

[0009] To solve the above problems, the present invention provides a guide vane for an air turbine starter with a low excitation frequency. On the premise of ensuring the normal operation of the air turbine starter, the excitation frequency of the guide vane is always lower than the turbine resonance frequency, and the batch production cost is lower than the above two methods.

[0010] The technical solution adopted by the present invention is as follows:

[0011] A guide vane for an air turbine starter with a low excitation frequency, the guide vane has 15 to 20 blades, all the blades are evenly distributed along the circumference of the guide vane body, the axial chord length of the guide vane is 19 to 20 mm, the geometric inlet angle is 100° to 110°, the geometric outlet angle is 15° to 16°, the leading edge radius is 2.4 to 2.6 mm, the trailing edge radius is 0.3 to 0.4 mm, and the trailing edge turning angle is 5 to 6.5°.

[0012] Further, the guide vane has 17 blades.

[0013] Further, the blades of the guide vane are designed according to the following key coordinate points:

[0014]

[0015] Further, the above key coordinate points take the intersection point of the tangents on both sides of the trailing edge of the blade at the installation angle as the origin.

[0016] Further, the above key coordinate points are smoothly connected by curves.

[0017] Further, the blade pitch of the guide vane is 29 to 30 mm, the blade chord length is 42 to 43 mm, the installation angle of the blade is 25° to 26°, the throat width between the blades is 6 to 7 mm, and the single-channel throat area is 90 to 100 mm 2 .

[0018] Further, the blade pitch of the guide vane is 29.48 mm, the blade chord length of the blade is 42.4 mm, the installation angle of the blade is 25.5°, the throat width between the blades is 6.33 mm, and the single-channel throat area between the blades is 97.69 mm 2 .

[0019] Further, the axial chord length of the guide vane body is 19.86 mm, the diameter of the maximum thickness circle is 6.3 mm, the geometric inlet angle is 105°, the geometric outlet angle is 15.4°, the leading edge radius is 2.5 mm, the trailing edge radius is 0.35 mm, and the trailing edge turning angle is 6°.

[0020] Beneficial effects:

[0021] 1. The excitation frequency of the guide vane wake is lower than the resonance frequency of the turbine blade, completely avoiding the wake excitation problem.

[0022] 2. The cross-section parameters of the guide vane are reasonably designed, and the pneumatic requirements of the air turbine starter can be met with a relatively small number of 17 guide vanes.

[0023] 3. Compared with the method of using crowned turbines, etc., the production cost of the present invention is relatively low and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 3D schematic diagram of the guide vane for the embodiment of the present invention;

[0026] Figure 2 Another perspective 3D schematic diagram of the guide vane for the embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the blade profile coordinates for the embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the guide vane wake for the embodiment of the present invention;

[0029] Figure 5 Campbell diagram of the coupled vibration of the turbine stage blade disk for the embodiment of the present invention;

[0030] Figure 6 Schematic diagram of the output torque characteristics of the air turbine starter for the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] This part is an embodiment of the present invention, used to explain and illustrate the technical solutions of the present invention. Without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicating directions or positional relationships are the azimuth or positional relationships given in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include more than one such feature. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0033] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled" should be interpreted in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0034] Please refer to Figure 1 As shown, the present invention provides a guide vane for an air turbine starter. The guide vane has 17 straight vanes evenly distributed along the circumference. The vane profile determines the key coordinate points through a rectangular coordinate system, such as Figure 3 and shown in Table 1, and the key coordinate points are smoothly connected by curves. The vane profile of the guide vane is characterized in that the axial chord length is 19.86 mm, the diameter of the maximum thickness circle is 6.3 mm, the geometric inlet angle is 105°, the geometric outlet angle is 15.4°, the leading edge radius is 2.5 mm, the trailing edge radius is 0.35 mm, and the trailing edge turning angle is 6°. The guide vane is characterized in that the number of vanes is 17, the pitch is 29.48 mm, the chord length is 42.4 mm, the installation angle is 25.5°, the throat width is 6.33 mm, and the single-channel throat area is 97.69 mm 2 .

[0035] Table 1 Coordinate Table of Key Points of Guide Vane

[0036]

[0037]

[0038] The working principle of the above technical solution is as follows: The fundamental way to eliminate the resonance of turbine blades is to reduce the wake excitation frequency of the guide vane or increase the resonance frequency of the turbine blades so that there is no resonance point within the operating speed range of the turbine. By comparing the resonance frequencies of existing turbine blades, a technical solution of reducing the wake excitation frequency of the guide vane is adopted, and the number of guide vane blades is designed to be 17. On the premise of ensuring the service performance, with the maintenance of the usage requirements of the air turbine starter as the constraint condition, the cross-sectional shape, axial chord length, maximum thickness circle diameter, geometric inlet angle, geometric outlet angle, leading edge radius, trailing edge radius, trailing edge turning angle, pitch, chord length, installation angle, throat width, and single-channel throat area parameters of the guide vane are matched and designed.

[0039] The maximum turbine operating speed of a certain type of air turbine starter is between 33237 and 35450 r / min, and the resonance frequencies of different orders are 11510 - 14308 Hz. The guide vane of the present invention can effectively avoid the problem of the coincidence of the wake excitation frequency of the guide vane and the resonance frequency of the turbine blade, as Figure 5 shown. At the same time, the starting efficiency of the turbine stage of the air turbine starter is ensured, as Figure 6 shown.

[0040] For the present invention, an experimental method is used to verify the effect of the above technical solution. A certain type of air turbine starter is subjected to cyclic operation and durability tests. After using the guide vane described in this patent, the service life is extended from 427 starts to 2726 starts. The curves of the output torque characteristics of the air turbine starter, etc. are shown in Figure 6 , the solid line is the characteristic curve of using a guide vane with 22 blades, and the dashed line is the characteristic curve of using a guide vane with 17 blades, which basically coincide. It can be seen that the starting efficiency of the turbine stage of the air turbine starter basically remains unchanged after implementing the guide vane described in the present invention.

[0041] The above results show that the device of the present invention has achieved the expected goal and is practical and feasible.

[0042] Based on the above verification, it can be known that the guide vane of the air turbine starter provided in this embodiment has a simple structure, is convenient to process, and is easy to be integrated into the existing air turbine starter, and can effectively avoid the problem of the coincidence of the wake excitation frequency of the guide vane and the resonance frequency of the turbine blade. At the same time, it has basically no influence on the torque characteristic curve of the air turbine starter.

[0043] In addition, there are many specific implementation methods and ways for the present invention, and the above description is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A guide vane for an air turbine starter with a low excitation frequency, characterized in that, The guide vane has 15 to 20 vanes, and all vanes are evenly distributed along the circumference of the guide vane body. The axial chord length of the guide vane is 19 to 20 mm, the geometric inlet angle is 100° to 110°, the geometric outlet angle is 15° to 16°, the leading edge radius is 2.4 to 2.6 mm, the trailing edge radius is 0.3 to 0.4 mm, the trailing edge turning angle is 5 to 6.5°, the vane pitch of the guide vane is 29 to 30 mm, the vane chord length is 42 to 43 mm, the installation angle of the vane is 25° to 26°, the throat width between vanes is 6 to 7 mm, and the throat area of a single channel is 90 to 100 mm 2 .

2. The guide vane for an air turbine starter with a low excitation frequency according to claim 1, characterized in that, The guide vane has 17 blades.

3. The guide vane for an air turbine starter with a low excitation frequency according to claim 2, characterized in that, The guide vane blades are designed according to the following key coordinate points:

4. The guide vane for an air turbine starter with a low excitation frequency according to claim 3, characterized in that The above key coordinate points take the intersection point of the tangents on both sides of the trailing edge of the blade at the installation angle as the origin.

5. The guide vane for an air turbine starter with a low excitation frequency according to claim 3, characterized in that, The above key coordinate points are smoothly connected by curves.

6. The guide vane for an air turbine starter with a low excitation frequency according to claim 1, characterized in that, The blade pitch of the guide vane is 29.48 mm, the blade chord length is 42.4 mm, the blade installation angle is 25.5°, the throat width between blades is 6.33 mm, and the single-channel throat area between blades is 97.69 mm 2 .

7. A guide vane for an air turbine starter with a low excitation frequency according to claim 1, characterized in that, The axial chord length of the guide vane body is 19.86 mm, the diameter of the maximum thickness circle is 6.3 mm, the geometric inlet angle is 105°, the geometric outlet angle is 15.4°, the leading edge radius is 2.5 mm, the trailing edge radius is 0.35 mm, and the trailing edge turning angle is 6°.

Images