Structure and method for suppressing thermoacoustic oscillations in a gas turbine combustor

Abstract

The application discloses a structure and method for inhibiting thermal acoustic oscillation of a gas turbine combustor, relates to the field of inhibiting thermal acoustic oscillation of a gas turbine combustor, and is applied to a combustor and comprises an outer layer pipe and an inner layer pipe, wherein the inner layer pipe is located in the outer layer pipe and the inner layer pipe and the outer layer pipe are coaxial; a back cavity is formed between the inner layer pipe and the outer layer pipe; a plurality of acoustic holes are arranged on the inner layer pipe and the acoustic holes are communicated with the back cavity; the space corresponding to the acoustic holes in the back cavity is a resonance cavity; and each acoustic hole and the resonance cavity form a resonance system. The application can effectively inhibit thermal acoustic oscillation of the gas turbine combustor and reduce the influence caused by the thermal acoustic oscillation.

Description

Technical Field

[0001] This invention relates to the field of suppressing thermoacoustic oscillations in gas turbine combustors, and in particular to a structure and method for suppressing thermoacoustic oscillations in gas turbine combustors. Background Technology

[0002] The burner is one of the three core components of a gas turbine. Fuel and air mix and undergo a violent combustion chemical reaction within it, forming high-temperature, high-pressure gas that provides the power source for the turbine to perform work. Thermoacoustic oscillation is a major factor limiting the advancement of burners and even gas turbines towards higher efficiency and higher temperature performance. Thermoacoustic oscillation originates from the coupling effect between the flame heat release rate and pressure disturbance. The pressure disturbance affects the local instantaneous heat release rate, and conversely, changes in the heat release rate generate pressure disturbances with a certain time (phase) delay from the initial disturbance. Subsequently, the pressure disturbance wave is reflected at the flame tube boundary, ultimately forming a closed-loop feedback circuit.

[0003] When the rate at which the combustion process provides energy to the sound field exceeds the dissipation of sound energy, it causes significant pressure fluctuations, including circumferential, axial, radial, and combined oscillations of different modes. This can lead to backfire or flameout, causing component ablation or even shutdown. When resonance occurs with the structure, it can exacerbate low-cycle or high-cycle fatigue of components, shorten component life, or even cause component failure. It can also interfere with the operation of the control system and endanger the safe operation of the gas turbine. Therefore, how to suppress the thermoacoustic oscillation of the gas turbine combustor is a problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a structure and method for suppressing thermoacoustic oscillations in gas turbine combustors, which can effectively suppress thermoacoustic oscillations and reduce the impact of thermoacoustic oscillations, in order to address the problems mentioned above.

[0005] The technical solution adopted in this invention is as follows: A structure for suppressing thermoacoustic oscillations in a gas turbine combustor, applied in the combustor, includes an outer tube and an inner tube, wherein the inner tube is located inside the outer tube and the inner tube and the outer tube are coaxial; a back cavity is formed between the inner tube and the outer tube; a plurality of acoustic holes are provided on the inner tube, the acoustic holes are connected to the back cavity, and the space corresponding to the acoustic holes in the back cavity is a resonance cavity, and each acoustic hole and the resonance cavity form a resonance system.

[0006] Furthermore, both ends of the back cavity are provided with sealing plates, which are fixed between the end of the inner tube and the inner wall of the outer tube.

[0007] Furthermore, several acoustic holes are evenly arranged along the circumference and axial direction of the inner tube.

[0008] Furthermore, the outer tube has several cooling holes, which are connected to the back cavity.

[0009] Furthermore, several cooling holes are evenly arranged along the circumference and axial direction of the outer tube.

[0010] A method for suppressing thermoacoustic oscillations in a gas turbine combustor, using the aforementioned structure for suppressing thermoacoustic oscillations in a gas turbine combustor, includes the following steps:

[0011] S1: Install the structure coaxially inside the flame tube;

[0012] S2: The incident sound wave generated by the vibration source enters the back cavity through the acoustic hole;

[0013] S3: Sound waves resonate at the acoustic aperture, consuming and absorbing sound wave energy with the same or similar resonant frequency as the resonant system.

[0014] Furthermore, by changing the shape and position of the system composed of the inner tube and the back cavity, it is possible to consume and absorb sound waves generated by different excitation sources.

[0015] Furthermore, by adjusting the height and length of the back cavity, as well as the diameter and number of acoustic holes, it is possible to consume and absorb sound waves of different frequencies.

[0016] Furthermore, the cold flow enters the back cavity from the cooling holes and then flows through the acoustic holes to form a deflection flow. The presence of the deflection flow enhances the absorption effect of sound wave energy.

[0017] Furthermore, cold air enters the back cavity through the cooling holes to cool the inner tube, reducing dimensional changes in the inner tube and acoustic holes.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] This invention utilizes a back cavity formed by an inner tube and an outer tube, with several acoustic holes on the inner tube. The acoustic holes and the back cavity space at the acoustic holes form a resonance system, and the acoustic holes and the entire back cavity form an acoustic damping system. The acoustic damping system is equivalent to multiple resonance systems connected in parallel. Sound waves will resonate at the acoustic holes of the resonance system, thereby consuming and absorbing sound energy and achieving the purpose of suppressing thermoacoustic oscillations. Attached Figure Description

[0020] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a schematic diagram of the structure disclosed in this invention;

[0022] Figure 2 This is a schematic diagram of the circumferential arrangement of cooling holes disclosed in this invention;

[0023] Figure 3This is a schematic diagram of the circumferential arrangement of the acoustic apertures shared by the present invention;

[0024] The markings in the diagram are: 1-outer tube; 11-cooling hole; 2-inner tube; 21-acoustic hole; 3-back cavity; 31-resonance cavity; 4-sealing plate. Detailed Implementation

[0025] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0026] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0027] Example 1

[0028] like Figures 1-3 As shown, a structure for suppressing thermoacoustic oscillations in a gas turbine combustor is applied in the combustor and installed inside the combustion chamber. It includes an outer tube 1 and an inner tube 2. The inner tube 2 is located inside the outer tube 1 and is coaxial with the outer tube 1. A gap exists between the outer wall of the inner tube 2 and the inner wall of the outer tube 1, which serves as a back cavity 3, i.e., a back cavity 3 is formed between the inner tube 2 and the outer tube 1. Several acoustic holes 21 are provided on the inner tube 2, and these acoustic holes 21 communicate with the back cavity 3. Each acoustic hole 21 and the space within the back cavity 3 at that location form a resonance system. In fact, the resonance system consists of a resonance cavity 31 and acoustic holes 21. The resonance cavity 31 is actually the portion of the space corresponding to the acoustic hole 21 within the back cavity 3, a part of the back cavity 3, located at the corresponding acoustic hole 21 position. The acoustic damping system formed by the acoustic holes 21 and the back cavity 3 is equivalent to being formed by several resonance systems connected in parallel.

[0029] In this embodiment, sound waves enter the back cavity 3 through the acoustic hole 21. If the frequency of the sound waves is the same as the resonant frequency of the resonant system, the sound waves will resonate at the position of the acoustic hole 21, and the sound energy will be consumed and absorbed. The acoustic damping system composed of the acoustic hole 21 and the back cavity 3 is formed by several resonant systems connected in parallel. Under the action of the acoustic damping system, the frequency of the sound waves in the flame tube that are absorbed and have their energy consumed is also wider than that of a single resonant system.

[0030] In this embodiment, the resonant frequency of a single resonant system is calculated as follows:

[0031]

[0032] in:

[0033] c: Velocity of sound; N: Number of acoustic apertures; D: Diameter of acoustic apertures; V: Total volume of back cavity 3; L eq : Resonance equivalent length.

[0034] The method for determining the resonance equivalent length is as follows:

[0035] L eq =t+0.8d

[0036] in:

[0037] T: Thickness of the inner tube; d: Diameter of acoustic hole 21; 0.8d: Correction amount; Since the air near both ends of the air column at acoustic hole 21 also participates in the vibration, a correction is required, and the correction value is generally taken as 0.8d.

[0038] In summary, in this embodiment, the back cavity 3 is formed by the inner tube 2 and the outer tube 1, and several acoustic holes 21 are provided on the inner tube 2. The acoustic holes 21 and the space of the back cavity 3 at the acoustic holes 21 form a resonance system. The acoustic holes 21 and the entire back cavity 3 form an acoustic damping system. The acoustic damping system is equivalent to multiple resonance systems connected in parallel. The sound waves will resonate at the acoustic holes 21 of the resonance system, thereby consuming and absorbing the sound energy, achieving the purpose of suppressing thermoacoustic oscillation, and significantly improving the stability and safety of the burner operation.

[0039] Example 2

[0040] Based on Example 1, further feasible implementation methods are proposed.

[0041] In one feasible implementation, a sealing plate 4 is provided at both ends of the back cavity 3. The sealing plate 4 seals the back cavity 3 and is fixed between the end of the inner tube 2 and the inner wall of the outer tube 1, so that the back cavity 3 is an independent space, effectively preventing sound waves from entering the back cavity 3 from both ends and causing interference.

[0042] In one feasible implementation, a number of acoustic holes 21 are evenly arranged along the circumference and axial direction of the inner tube 2, so that the pressure loss of the sound waves is more uniform.

[0043] In one feasible implementation, the acoustic hole 21 can be cylindrical, square, or other shapes. In a preferred embodiment, the cross-sectional shape of the acoustic hole 21 is conical, and the small diameter section of the acoustic hole 21 is close to the back cavity 3; this can increase the frequency band that can be consumed and absorbed by sound waves.

[0044] Furthermore, when the acoustic aperture 21 is conical, the diameter D of the acoustic aperture 21 in Example 1 can be selected as the middle diameter of the cone as the diameter of the acoustic aperture 21.

[0045] Example 3

[0046] Based on any one of the implementation methods in Examples 1-2, further feasible specific implementation methods are proposed.

[0047] In one feasible implementation, a plurality of cooling holes 11 are provided on the outer tube 1, and the cooling holes 11 are connected to the back cavity 3; a relatively low temperature cold flow enters the back cavity 3 through the cooling holes 11. In this embodiment, the introduction of the cold flow has at least the following beneficial effects.

[0048] One beneficial effect is that the cold flow can cool the inner tube 2, reducing the heat in the combustion chamber and causing changes in the geometric dimensions of the inner tube 2 and the acoustic hole 21. This ensures that the inner tube 2 and the acoustic hole 21 are close to and maintain the designed dimensions. Since the resonant frequency of the resonance system is related to the aperture of the acoustic hole 21, the thickness of the inner tube 2, and the total volume of the back cavity 3, ensuring that the inner tube 2 and the acoustic hole 21 are close to and maintain the designed dimensions guarantees the resonant frequency of the resonance system. For a certain frequency of sound wave, this ensures the ability to consume and absorb sound energy, further guaranteeing the effect of suppressing thermoacoustic oscillations.

[0049] Secondly, after the cold flow enters the back cavity 3, it forms a deflection flow at the acoustic hole 21. The deflection flow can enhance the velocity disturbance and viscosity effect at the acoustic hole 21, accelerate the conversion of acoustic energy into vortex energy, and thus enhance the sound absorption effect of the resonance system.

[0050] The third beneficial effect is that the cooling performance of the burner can be improved by utilizing the deflected cold air.

[0051] Furthermore, a plurality of cooling holes are arrayed circumferentially along the outer tube 1, so that the cold flow can enter the back cavity 3 uniformly from the circumference of the outer tube 1, thereby achieving the purpose of uniformly cooling the inner tube 2 circumferentially; a plurality of cooling holes 11 are arrayed along the axis of the outer tube 1, so that the cold flow can enter the back cavity 3 uniformly from the axial direction of the outer tube 1, thereby achieving the purpose of uniformly cooling the inner tube 2 axially; uniform cooling in both the circumferential and axial directions achieves the purpose of uniform cooling of the whole.

[0052] In this embodiment, the cold stream is cooling air, which can be relatively low-temperature air.

[0053] Example 4

[0054] A method for suppressing thermoacoustic oscillations in a gas turbine combustor, using the structure for suppressing thermoacoustic oscillations in a gas turbine combustor as described in any one of the embodiments of Examples 1-3, includes the following steps:

[0055] S1: Install the structure coaxially inside the flame tube;

[0056] S2: The incident sound wave generated by the vibration source enters the back cavity 3 through the acoustic hole 21;

[0057] S3: The sound wave resonates at the acoustic hole 21, consuming and absorbing the sound wave energy that is the same as or similar to the resonant frequency of the resonant system.

[0058] In this embodiment, the method for obtaining the resonant frequency of the resonant system can be found in the description of Embodiment 1, and will not be described in detail here.

[0059] Furthermore, by changing the shape and position of the system composed of the inner tube 2 and the back cavity 3, it is possible to consume and absorb sound waves generated by different excitation sources.

[0060] Furthermore, by adjusting the height and length of the back cavity 3, and the aperture, number, and arrangement of the acoustic holes 21, sound waves of different frequencies can be consumed and absorbed. According to the formula in Example 1, adjusting the height and length of the back cavity 3 is actually adjusting the total volume of the back cavity 3. By comprehensively adjusting the aperture and number of the acoustic holes 21, the resonant frequency of the resonant system can be adjusted, thereby achieving the consumption and absorption of sound waves of different frequencies.

[0061] In this embodiment, cooling holes 11 are formed on the outer tube 1. The cold flow enters the back cavity 3 from the cooling holes 11 and then flows through the acoustic hole 21 to form a deflection flow. The presence of the deflection flow enhances the absorption effect of sound wave energy and further improves the effect of suppressing thermoacoustic oscillation. In addition, the inner tube 2 is cooled to reduce the size change of the inner tube and the acoustic hole 21 and ensure the resonance frequency of the resonance system. For a sound wave of a certain frequency, the ability to consume and absorb sound energy can be guaranteed, further ensuring the effect of suppressing thermoacoustic oscillation.

[0062] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method of suppressing thermoacoustic oscillations in a combustion chamber of a gas turbine engine, characterized by: The application discloses a structure for inhibiting thermal acoustic oscillation of a gas turbine combustor, which is installed in the combustor and comprises an outer tube (1) and an inner tube (2) located in the outer tube (1) and coaxial with the outer tube (1); a back cavity (3) is formed between the inner tube (2) and the outer tube (1); a plurality of acoustic holes (21) are arranged on the inner tube (2) and are communicated with the back cavity (3), a corresponding space in the back cavity (3) at the acoustic holes (21) is a resonance cavity (31), each acoustic hole (21) and the resonance cavity (31) form a resonance system; a closing plate (4) is arranged at each end of the back cavity (3) and is fixed between the end of the inner tube (2) and the inner wall of the outer tube (1). The application discloses a structure for inhibiting thermal acoustic oscillation of a gas turbine combustor, which is installed in the combustor and comprises an outer tube (1) and an inner tube (2) located in the outer tube (1) and coaxial with the outer tube (1); a back cavity (3) is formed between the inner tube (2) and the outer tube (1); a plurality of acoustic holes (21) are arranged on the inner tube (2) and are communicated with the back cavity (3), a corresponding space in the back cavity (3) at the acoustic holes (21) is a resonance cavity (31), each acoustic hole (21) and the resonance cavity (31) form a resonance system; a closing plate (4) is arranged at each end of the back cavity (3) and is fixed between the end of the inner tube (2) and the inner wall of the outer tube (1). S1: installing the structure coaxially in the flame tube; S2: incident sound waves generated by a vibration source enter the back cavity (3) through the acoustic holes (21); S3: the sound waves resonate at the acoustic holes (21) and consume and absorb sound wave energy with the same or / and similar resonance frequency as the resonance system; The calculation formula of the resonance frequency of a single resonance system is as follows: f = c / (2 * L eq) wherein: c: sound velocity; N: the number of acoustic holes; D: the diameter of the acoustic hole; V: the total volume of the back cavity; Leq: resonance equivalent length; The determination formula of the resonance equivalent length is as follows: L eq = (N * D) / (4 * V) wherein: T: the thickness of the inner tube; d: the diameter of the acoustic hole 21; 0.8d: correction amount. The plurality of acoustic holes (21) are uniformly arranged along the circumferential direction and the axial direction of the inner tube (2). The outer tube (1) is provided with a plurality of cooling holes (11) communicated with the back cavity (3). The plurality of cooling holes (11) are uniformly arranged along the circumferential direction and the axial direction of the outer tube (1). Changing the shape and position of the system composed of the inner tube (2) and the back cavity (3) can consume and absorb sound waves generated by different excitation sources.

2. The method of claim 1, wherein: Adjusting the height and length of the back cavity (3) and the diameter and number of the acoustic holes (21) can consume and absorb sound waves with different frequencies.

3. The method according to any one of claims 1-2, characterized in that: Cold flow enters the back cavity (3) from the cooling holes (11) and then forms a bias flow through the acoustic holes (21), and the existence of the bias flow enhances the absorption effect of sound energy.

4. The structure of claim 3, wherein: Cold flow enters the back cavity (3) from the cooling holes (11) to cool the inner tube (2) and weaken the size change of the inner tube (2) and the acoustic holes (21).

5. The method of claim 1, wherein: ​ 6. The method of claim 1, wherein: ​ 7. The method of claim 3, wherein: ​ 8. The method of claim 7, wherein: ​

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