Multi-head fan-shaped combustion chamber test piece with sound-absorbing cavity and sound-absorbing adjustment method

Abstract

The application provides a multi-head fan-shaped combustion chamber test piece with a sound-absorbing cavity and a sound-absorbing adjusting method. The test piece comprises a bearing casing between an air inlet pipe and an air outlet pipe; an air inlet assembly arranged in the bearing casing, wherein the air inlet assembly comprises a flow regulation pipe and a diffuser pipe, the flow regulation pipe comprises an inlet baffle and a flow regulation pipe, the diffuser pipe comprises a fixed plate, a flow guide pipe, a flow expansion pipe and a conical wall, the upper and lower ends and the left and right ends of the flow regulation pipe and the diffuser pipe are connected with the bearing casing, a plurality of first acoustic damping holes are formed in the flow regulation pipe, and a plurality of second acoustic damping holes are formed in the conical wall; and a flame tube assembly arranged at an air outlet of the air inlet assembly. The frequency of a first Helmoltz resonator formed by the flow regulation pipe and the bearing casing is the same as the disturbance frequency of the airflow in the air inlet pipe; and the frequency of a second Helmoltz resonator formed by the diffuser pipe and the bearing casing is the same as the combustion oscillation frequency in the flame tube assembly. The application can effectively suppress combustion oscillation, maintain stable airflow and reduce noise.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature and high-pressure combustion chamber test piece design, and particularly relates to a multi-head fan-shaped combustion chamber test piece with a sound-absorbing cavity and a sound-absorbing adjusting method. BACKGROUND

[0002] With the development of aviation technology, higher requirements are put forward for the temperature ratio, pressure ratio, thrust-to-weight ratio and combustion efficiency of an aero-engine. As a key component of an aero-engine, a combustion chamber undertakes the important task of converting chemical energy into power and directly affects the performance of the engine. In the development process of an aero-engine, the combustion chamber of the aero-engine needs to be verified from paper design to application in core engine / whole engine test to verify the performance indexes of the combustion chamber component, such as combustion efficiency, temperature distribution, pressure change and the like, so as to ensure that it meets the design requirements, and needs to carry out technical verification through single-head combustion chamber test, multi-head fan-shaped combustion chamber test and full annular combustion chamber test.

[0003] In the three tests, the shape and layout of the single-head combustion chamber are single, the combustion process is only carried out in one area, and the distribution of the combustion process in the combustion chamber is not uniform enough. The single-head combustion chamber is generally used for combustion chamber multi-scheme screening, so as to select one to several schemes with better comprehensive performance from multiple schemes, and then carry out further test verification in a fan-shaped combustion chamber or even a full annular combustion chamber. In the selection of multi-head fan-shaped combustion chambers and full annular combustion chambers, although the full annular combustion chamber test can realize the distribution of the combustion chamber along the entire engine circumference and provide more comprehensive combustion, the structure is more complex, and the manufacturing and maintenance costs are higher. Therefore, the multi-head fan-shaped combustion chamber test is more commonly used.

[0004] For a low-emission combustion chamber, in the fan-shaped combustion chamber test thereof, pressure waves may be caused due to reflection and interference of the gas, leading to unstable combustion, so as to cause fluctuations of engine thrust, power and fuel consumption rate, reduce the combustion efficiency, make it difficult to achieve the expected fuel supply parameters, affect the precision and repeatability of the test, cause the test working condition parameters to be unable to meet the verification requirements, result in test failure, and even cause damage to the test equipment itself.

[0005] Chinese invention CN115930260A discloses an air bleed structure for an auxiliary power unit, which includes a casing and a flame tube. The casing is a double-shell structure, including an inner shell and an outer shell located on the outer periphery of the inner shell, forming a casing cavity between the outer shell and the inner shell. An inner shell air bleed port is provided on the inner shell, and an outer shell air bleed port is provided on the outer shell. The outer shell air bleed port supplies air to the main engine's air supply passage through an air bleed pipe. The flame tube is located inside the inner shell, and its outer wall has a flame tube air inlet. An air intake channel is formed between the inner shell and the outer wall of the flame tube. The angle between the opening direction of the inner shell air bleed port and the air intake direction of the air intake channel is no greater than 75°. For airflow passing through the vent holes in the inner casing, since the inner and outer casings are integrated and the opening angle of the vent holes is consistent with the airflow direction, the airflow is evenly dispersed by the vent holes after passing through them. This prevents the airflow from flowing randomly within the casing, increases the orderliness of the airflow, and effectively reduces the excitation effect caused by the initial vibration and unevenness of the venting. The above invention disperses the mainstream flow instability through the design of a double-layer casing, thereby reducing the initial flow disturbance. However, this design has high structural complexity and increases design costs. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-head fan-shaped combustion chamber test piece with a silencing cavity and a silencing adjustment method to solve the above-mentioned problems. It can effectively suppress combustion oscillations, maintain stable gas flow in the combustion chamber, and reduce noise during combustion chamber operation.

[0007] This invention proposes a multi-head sector-shaped combustion chamber test piece with a silencing cavity, comprising:

[0008] The load-bearing casing is located between the intake pipe and the exhaust pipe;

[0009] An air intake assembly, disposed within the load-bearing casing, introduces and diffuses airflow. The air intake assembly includes a rectifier pipe and a diffuser pipe. The rectifier pipe includes an inlet baffle and a rectifier tube. The diffuser pipe includes a fixed plate, a guide pipe, a diffuser tube, and a conical wall. The inlet baffle includes two vertical plates, one end of which is connected to the load-bearing casing, and the other end of which is connected to one end of the rectifier tube. The other end of the rectifier tube is connected to the fixed plate. The upper and lower ends of the fixed plate are respectively connected to the load-bearing casing. One end of the guide pipe is connected to the fixed plate, and the other end is connected to one end of the diffuser tube. The conical wall is circumferentially arranged around the outer wall of the diffuser tube and close to the inner wall of the load-bearing casing. The rectifier tube has several first acoustic damping holes, and the conical wall has several second acoustic damping holes.

[0010] The flame tube assembly is disposed within the load-bearing casing and located at the exhaust port of the air intake assembly, receiving diffused airflow;

[0011] The rectifier pipe and the load-bearing casing form a first Helmoltz resonator, the frequency of which is the same as the frequency of the incoming flow disturbance in the intake pipe. The diffuser pipe and the load-bearing casing form a second Helmoltz resonator, the frequency of which is the same as the combustion oscillation frequency in the flame tube assembly.

[0012] In one embodiment, the load-bearing casing includes a first transition casing, an air bleed section casing, a test section casing, a measurement section casing, and a second transition casing;

[0013] One end of the first adapter casing is connected to the intake pipe, and the other end is connected to one end of the bleed section casing. The other end of the bleed section casing is connected to one end of the test section casing. The other end of the test section casing is connected to one end of the measurement section casing. The other end of the measurement section casing is connected to one end of the second adapter casing. The other end of the second adapter casing is connected to the exhaust pipe.

[0014] The cross-section of the first adapter casing gradually decreases from one end connected to the intake pipe to the other end connected to the bleed section casing. The cross-sections of the bleed section casing, the test section casing, and the measurement section casing remain unchanged along the axial direction. The cross-section of the second adapter casing gradually increases from one end connected to the measurement section casing to the other end connected to the exhaust pipe.

[0015] In one embodiment, both the bleed section casing and the test section casing have a fan-shaped cross-section;

[0016] The bleed section casing includes a first outer ring casing, a first inner ring casing, and two first side casings. The first outer ring casing and the first inner ring casing are both arc-shaped. The arc radius of the first outer ring casing is larger than that of the first inner ring casing. The two first side casings are both semicircles, which are respectively connected to the two ends of the first outer ring casing and the first inner ring casing, forming a closed pipeline with the first outer ring casing and the first inner ring casing.

[0017] The test section casing includes a second outer ring casing, a second inner ring casing, and two second side casings. Both the second outer ring casing and the second inner ring casing are arc-shaped, with the arc radius of the second outer ring casing being larger than that of the second inner ring casing. The two second side casings are semicircles, respectively connecting the two ends of the second outer ring casing and the second inner ring casing, forming a closed pipeline with the second outer ring casing and the second inner ring casing.

[0018] In one embodiment, the rectifier pipe is disposed inside the bleed section casing, the rectifier pipe further includes a mounting plate, the inlet baffle further includes two horizontal plates, the two horizontal plates face the first outer ring casing and the first inner ring casing respectively, and have a gap G1 between them and the first outer ring casing and the first inner ring casing respectively, one end of each of the two vertical plates is connected to the horizontal plate, and the other end is connected to one end of the rectifier pipe, the other end of the rectifier pipe is connected to the mounting plate, the cross-section of the rectifier pipe remains unchanged along the axial direction, and the mounting plate is bolted to the fixing plate.

[0019] In one embodiment, the rectifier tube has a fan-shaped cross-section and includes an outer ring rectifier plate, an inner ring rectifier plate, and two side rectifier plates. The first acoustic damping hole includes a first outer ring damping hole and a first inner ring damping hole.

[0020] Both the outer ring rectifier plate and the inner ring rectifier plate are arc-shaped, and the arc radius of the outer ring rectifier plate is larger than that of the inner ring rectifier plate. The first outer ring damping hole is disposed on the outer ring rectifier plate, and the first inner ring damping hole is disposed on the inner ring rectifier plate.

[0021] Two side rectifier plates are respectively connected to the two ends of the outer ring rectifier plate and the inner ring rectifier plate, and extend radially to connect with the first outer ring casing and the first inner ring casing;

[0022] The outer ring rectifier plate, the first outer ring casing, and the two side rectifier plates form a third cavity V1, which forms a first outer ring Helmoltz resonator. The inner ring rectifier plate, the first inner ring casing, and the two side rectifier plates form a fourth cavity V2, which forms a first inner ring Helmoltz resonator.

[0023] In one embodiment, the diffuser pipe is disposed inside the test section casing, and the two ends of the fixing plate are respectively bolted to the second outer ring casing and the second inner ring casing;

[0024] The cross-section of the guide tube is fan-shaped and remains unchanged along the axial direction. The guide tube includes an outer ring guide plate, an inner ring guide plate, and two side guide plates. Both the outer ring guide plate and the inner ring guide plate are arc-shaped. The arc radius of the outer ring guide plate is larger than that of the inner ring guide plate. The two side guide plates are respectively connected to the two ends of the outer ring guide plate and the inner ring guide plate, and extend radially to connect with the second outer ring casing and the second inner ring casing.

[0025] The other end of the diffuser tube faces the flame tube assembly. The cross-section of the diffuser tube gradually increases from the end connected to the guide tube to the other end facing the flame tube assembly, thereby diffuser and compressing the airflow and introducing the diffused airflow into the flame tube assembly.

[0026] The outer ring guide plate, the second outer ring casing, and the two side guide plates form a fifth cavity V3, which forms a second outer ring Helmoltz resonator. The inner ring guide plate, the second inner ring casing, and the two side guide plates form a sixth cavity V4, which forms a second inner ring Helmoltz resonator.

[0027] In one embodiment, the conical wall includes an outer ring conical wall and an inner ring conical wall. The outer ring conical wall is close to the second outer ring housing and has a gap G2 between it and the second outer ring housing. The inner ring conical wall is close to the second inner ring housing and has a gap G2 between it and the second inner ring housing.

[0028] The second acoustic damping orifice includes a second outer ring damping orifice and a second inner ring damping orifice. The second outer ring damping orifice is disposed on the outer ring conical wall, and the second inner ring damping orifice is disposed on the inner ring conical wall.

[0029] In one embodiment, the flame tube assembly includes a flame tube outer wall, a flame tube inner wall, and two flame tube side walls;

[0030] Both the outer wall and the inner wall of the flame tube are arc-shaped, and the arc radius of the outer wall of the flame tube is greater than that of the inner wall of the flame tube.

[0031] The two flame tube sidewalls are respectively connected to the two ends of the outer wall of the flame tube and the inner wall of the flame tube, and extend radially to connect with the second outer ring casing and the second inner ring casing;

[0032] The flame tube assembly also includes multiple flame tube heads, which are located within the area enclosed by the outer wall of the flame tube, the inner wall of the flame tube, and the two side walls of the flame tube, and are evenly arranged along the circumference of the flame tube assembly.

[0033] In one embodiment, the multi-head sector-shaped combustion chamber test piece with a silencing cavity further includes a fuel nozzle, an ignition nozzle, and a pulsating pressure sensing element, wherein the fuel nozzle, the ignition nozzle, and the pulsating pressure sensing element are all disposed on the second outer ring casing;

[0034] The fuel nozzle is connected to the flame tube assembly, and fuel is injected into the flame tube assembly to mix and burn with the diffused airflow.

[0035] The ignition nozzle is installed on the flame tube head in the middle position and is used to ignite the fuel and diffuse the airflow;

[0036] The pulsating pressure sensing components are installed on the flame tube head at a non-central position to measure the dynamic pressure of the gas during combustion.

[0037] The present invention also proposes a noise reduction adjustment method, which is applied to the multi-head sector-shaped combustion chamber test piece with a noise reduction cavity as described above, and includes the following steps:

[0038] The frequency of the first outer ring Helmoltz resonator is adjusted by changing the volume of the third cavity, the diameter and number of the first outer ring damping holes, so that the frequency of the first outer ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe.

[0039] The frequency of the first inner ring Helmoltz resonator is adjusted by changing the volume of the fourth cavity, the diameter and number of the first inner ring damping holes, so that the frequency of the first inner ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe.

[0040] The frequency of the second outer ring Helmoltz resonator is adjusted by changing the volume of the fifth cavity, the diameter and number of the second outer ring damping holes, so that the frequency of the second outer ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly.

[0041] The frequency of the second inner ring Helmoltz resonator is adjusted by changing the volume of the sixth cavity, the diameter and number of the second inner ring damping holes, so that the frequency of the second inner ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly.

[0042] Compared with the prior art, the beneficial effects of the multi-head sector-shaped combustion chamber test piece with silencing cavity and the silencing adjustment method of the present invention are as follows:

[0043] 1) This invention can effectively suppress combustion oscillations, help maintain stable gas flow in the combustion chamber, reduce noise during combustion chamber operation, maintain combustion efficiency, and ensure that engine performance remains at the design level, thereby ensuring that the combustion chamber operating conditions can achieve the expected verification goals.

[0044] 2) This invention helps to reduce the vibration amplitude of combustion chamber components and related structures, improve the stability of the entire combustion test, maintain the controllability of the engine under various operating conditions, reduce the risk of instability, thereby reducing the risk of fatigue and stress concentration, and improving the reliability and life of the structure. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a multi-head sector-shaped combustion chamber test piece with a sound-absorbing cavity according to an embodiment of the present invention;

[0046] Figure 2 for Figure 1 Enlarged view of M;

[0047] Figure 3 for Figure 2 Sectional view of AA;

[0048] Figure 4 This is a schematic diagram of the rectifier pipe in a multi-head sector-shaped combustion chamber test piece with a silencing cavity according to an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the diffuser pipe in a multi-head sector-shaped combustion chamber test piece with a sound-absorbing cavity according to an embodiment of the present invention;

[0050] Figure 6 for Figure 2 BB section view;

[0051] Figure 7 for Figure 2 CC section view;

[0052] Figure 8 This is a schematic diagram of the first outer ring damping hole, the first inner ring damping hole, the second outer ring damping hole, and the second inner ring damping hole in a multi-head fan-shaped combustion chamber test piece with a sound-absorbing cavity according to an embodiment of the present invention.

[0053] Figure Labels

[0054] 1. Intake pipe; 10. First cavity; 2. Exhaust pipe; 20. Second cavity; 31. First transition casing; 32. Bleed air section casing; 321. First outer ring casing; 322. First inner ring casing; 323. First side casing; 33. Test section casing; 331. Second outer ring casing; 332. Second inner ring casing; 333. Second side casing; 34. Measurement section casing; 35. Second transition casing; 4. Fuel nozzle; 5. Flame tube assembly; 50. Combustion cavity; 51. Flame tube outer wall; 52. Flame tube inner wall; 53. Flame tube side wall; 61. Ignition electrode; 62. Pulsating pressure sensor; 7. Intake assembly; 71. Rectifier pipe; 711. Inlet baffle. 712, Rectifier tube; 7121, Outer ring rectifier plate; 7122, Inner ring rectifier plate; 7123, Side rectifier plate; 713, Mounting plate; 72, Diffuser pipe; 721, Fixing plate; 722, Guide pipe; 7221, Outer ring guide plate; 7222, Inner ring guide plate; 7223, Side guide plate; 723, Diffuser pipe; 724, Conical wall; 7241, Outer ring conical wall; 7242, Inner ring conical wall; P, Inlet cavity; V1, Third cavity; V2, Fourth cavity; V3, Fifth cavity; V4, Sixth cavity; G1, Gap between inlet baffle and first outer ring casing and first inner ring casing; G2, Gap between conical wall and second outer ring casing and second inner ring casing; f up The frequency of the incoming flow disturbance in the intake manifold, f c The combustion oscillation frequency within the flame tube assembly. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the specific embodiments described herein are for the purpose of aiding understanding the invention and do not constitute a limitation thereof.

[0056] This invention proposes a multi-head sector-shaped combustion chamber test piece with a silencing cavity, including a load-bearing casing, an air intake assembly 7, and a flame tube assembly 5. See [link to relevant documentation]. Figure 1 .

[0057] The load-bearing casing is composed of several casings arranged together and is located between the intake pipe 1 and the exhaust pipe 2.

[0058] The intake assembly 7 is disposed within the load-bearing casing and is used to introduce and diffuse airflow. The intake assembly 7 includes a rectifier duct 71 and a diffuser duct 72. The rectifier duct 71 includes an inlet baffle 711 and a rectifier tube 712. The diffuser duct 72 includes a fixed plate 721, a guide tube 722, a diffuser tube 723, and a conical wall 724. The inlet baffle 711 includes two vertical plates, each connected at one end to the load-bearing casing and at the other end to one end of the rectifier tube 712. The other end of the rectifier tube 712 is connected to the fixed plate 721, and the upper and lower ends of the fixed plate 721 are respectively connected to the load-bearing casing. One end of the guide tube 722 is connected to the fixed plate 721, and the other end is connected to one end of the diffuser tube 723. The conical wall 724 is circumferentially arranged around the outer wall of the diffuser tube 723 and close to the inner wall of the load-bearing casing. The rectifier tube 712 has several first acoustic damping holes, and the cone wall 724 has several second acoustic damping holes.

[0059] The flame tube assembly 5 is located inside the load-bearing casing and at the exhaust port of the air intake assembly 7, that is, the air intake assembly 7 is located upstream of the flame tube assembly 5.

[0060] The inner flow channel of the intake pipe 1 forms a first cavity 10 for supplying intake air. The flame tube assembly 5 forms a combustion cavity 50, in which fuel injected from the fuel nozzle 4 and diffused airflow from the intake assembly 7 are combusted. The inner flow channel of the exhaust pipe 2 forms a second cavity 20 for discharging the combusted gases.

[0061] The rectifier pipe 71 and the load-bearing casing form a first Helmoltz resonator, the frequency of which is the same as the frequency of the incoming flow disturbance in the intake pipe 1. The diffuser pipe 72 and the load-bearing casing form a second Helmoltz resonator, the frequency of which is the same as the combustion oscillation frequency in the flame tube assembly 5.

[0062] It's important to note that a Helmholtz resonator is a device used to adjust acoustic frequencies. It controls the frequency of sound waves by controlling the relative dimensions and shape between the neck of the container and the cavity. When sound waves enter the resonator, they interact with the air inside, causing the resonator to resonate at a specific frequency. This specific frequency is usually called the resonant frequency and can be changed by adjusting the resonator's geometric parameters. Helmholtz resonators exhibit a strong resonant response to specific sound frequencies, making them widely used in acoustic engineering and architectural acoustics for purposes such as sound absorption, noise reduction, and sound tuning.

[0063] The following is a detailed description of each component in the multi-head sector-shaped combustion chamber test piece with a silencing cavity described above.

[0064] One embodiment of the present invention includes a load-bearing casing comprising a first transfer casing 31, an air bleed section casing 32, a test section casing 33, a measurement section casing 34, and a second transfer casing 35.

[0065] One end of the first adapter casing 31 is connected to the intake pipe 1, and the other end is connected to one end of the bleed section casing 32. The other end of the bleed section casing 32 is connected to one end of the test section casing 33. The other end of the test section casing 33 is connected to one end of the measuring section casing 34. The other end of the measuring section casing 34 is connected to one end of the second adapter casing 35. The other end of the second adapter casing 35 is connected to the exhaust pipe 2.

[0066] The cross-section of the first transition casing 31 gradually decreases from one end connected to the intake pipe 1 to the other end connected to the bleed section casing 32. The cross-sections of the bleed section casing 32, the test section casing 33, and the measurement section casing 34 remain unchanged along the axial direction. The cross-section of the second transition casing 35 gradually increases from one end connected to the measurement section casing 34 to the other end connected to the exhaust pipe 2.

[0067] like Figure 3 , Figure 6 , Figure 7 As shown, in one embodiment of the present invention, both the bleed section casing 32 and the test section casing 33 have a fan-shaped cross-section.

[0068] The bleed air section casing 32 includes a first outer ring casing 321, a first inner ring casing 322, and two first side casings 323. Both the first outer ring casing 321 and the first inner ring casing 322 are arc-shaped, with the arc radius of the first outer ring casing 321 being larger than that of the first inner ring casing 322. The two first side casings 323 are semicircular, connecting the two ends of the first outer ring casing 321 and the first inner ring casing 322 respectively, forming a closed pipeline with the first outer ring casing 321 and the first inner ring casing 322.

[0069] The test section casing 33 includes a second outer ring casing 331, a second inner ring casing 332, and two second side casings 333. Both the second outer ring casing 331 and the second inner ring casing 332 are arc-shaped, with the arc radius of the second outer ring casing 331 being larger than that of the second inner ring casing 332. The two second side casings 333 are semicircles, connecting the two ends of the second outer ring casing 331 and the second inner ring casing 332 respectively, forming a closed pipeline with the second outer ring casing 331 and the second inner ring casing 332.

[0070] like Figure 2 , Figure 4 As shown, in one embodiment of the present invention, the rectifying pipe 71 is disposed inside the bleed section casing 32, and the rectifying pipe 71 also includes a mounting plate 713. The inlet baffle 711 also includes two horizontal plates, which face the first outer ring casing 321 and the first inner ring casing 322 respectively. The two horizontal plates have a certain installation gap G1 between them and the first outer ring casing 321 and the first inner ring casing 322, which is to ensure that the rectifying pipe 71 can be smoothly installed into the bleed section casing 32, but this gap G1 must be small enough. One end of each of the two vertical plates is connected to the horizontal plate, and the other end is connected to one end of the rectifying pipe 712. The other end of the rectifying pipe 712 is connected to the mounting plate 713. The cross-section of the rectifying pipe 712 remains unchanged along the axial direction, and the mounting plate 713 is bolted to the fixing plate 721.

[0071] like Figure 7 As shown, the rectifier tube 712 of one embodiment of the present invention has a fan-shaped cross-section and includes an outer ring rectifier plate 7121, an inner ring rectifier plate 7122, and two side rectifier plates 7123. Both the outer ring rectifier plate 7121 and the inner ring rectifier plate 7122 are arc-shaped, with the arc radius of the outer ring rectifier plate 7121 being larger than that of the inner ring rectifier plate 7122. The wall thickness of the outer ring rectifier plate 7121 is b1, and the wall thickness of the inner ring rectifier plate 7122 is b2. The two side rectifier plates 7123 are respectively connected to the two ends of the outer ring rectifier plate 7121 and the inner ring rectifier plate 7122, and extend radially to connect with the first outer ring casing 321 and the first inner ring casing 322.

[0072] like Figure 8 As shown, the first acoustic damping orifice includes a first outer ring damping orifice and a first inner ring damping orifice, both of which are circular through holes. The first outer ring damping orifice is evenly distributed on the outer ring rectifier plate 7121, with a diameter of d1 and a quantity of N1. The first inner ring damping orifice is evenly distributed on the inner ring rectifier plate 7122, with a diameter of d2 and a quantity of N2.

[0073] The outer ring rectifier plate 7121, the first outer ring casing 321 and the two side rectifier plates 7123 form a third cavity V1, forming a first outer ring Helmoltz resonator; the inner ring rectifier plate 7122, the first inner ring casing 322 and the two side rectifier plates 7123 form a fourth cavity V2, forming a first inner ring Helmoltz resonator.

[0074] like Figure 2 , Figure 5 , Figure 6 As shown, in one embodiment of the present invention, the diffuser pipe 72 is disposed inside the test section casing 33. The two ends of the fixing plate 721 are bolted to the second outer ring casing 331 and the second inner ring casing 332, respectively. The connection needs to be sealed to prevent air in the first cavity 10 from leaking from the connection to the combustion cavity 50.

[0075] The guide tube 722 has a fan-shaped cross-section that remains constant along the axial direction, and includes an outer ring guide plate 7221, an inner ring guide plate 7222, and two side guide plates 7223. Both the outer ring guide plate 7221 and the inner ring guide plate 7222 are arc-shaped, with the arc radius of the outer ring guide plate 7221 being larger than that of the inner ring guide plate 7222. The two side guide plates 7223 connect to the two ends of the outer ring guide plate 7221 and the inner ring guide plate 7222, respectively, and extend radially to connect with the second outer ring casing 331 and the second inner ring casing 332.

[0076] The outer ring guide plate 7221, the second outer ring casing 331 and the two side guide plates 7223 form a fifth cavity V3, which forms a second outer ring Helmoltz resonator; the inner ring guide plate 7222, the second inner ring casing 332 and the two side guide plates 7223 form a sixth cavity V4, which forms a second inner ring Helmoltz resonator.

[0077] The other end of the diffuser 723 faces the flame tube assembly 5. The cross-section of the diffuser 723 gradually increases from the end connected to the guide pipe 722 to the other end facing the flame tube assembly 5, thereby diffuser and guide the diffused airflow into the flame tube assembly 5.

[0078] The inner flow channels of the rectifier tube 712 and the guide tube 722 constitute the intake cavity P, which is used to rectify and transport gas. The connection between the mounting plate 713 and the fixing plate 721 needs to be sealed to prevent air in the third cavity V1 and the fourth cavity V2 from leaking into the intake cavity P from the connection.

[0079] like Figure 5As shown, in one embodiment of the present invention, the conical wall 724 includes an outer ring conical wall 7241 and an inner ring conical wall 7242. The outer ring conical wall 7241 is close to the second outer ring casing 331, has a wall thickness of b3, and has a certain installation gap G2 between it and the second outer ring casing 331. The inner ring conical wall 7242 is close to the second inner ring casing 332, has a wall thickness of b4, and has a certain installation gap G2 between it and the second inner ring casing 332. The installation gap G2 is designed to ensure that the diffuser pipe 72 can be smoothly installed into the interior of the test section casing 33, but this gap G2 must be small enough to simulate the real combustion chamber as much as possible.

[0080] like Figure 8 As shown, the second acoustic damping orifice includes a second outer ring damping orifice and a second inner ring damping orifice, both of which are circular through holes. The second outer ring damping orifice is evenly distributed on the outer ring conical wall 7241, with a diameter of d3 and a quantity of N3. The second inner ring damping orifice is evenly distributed on the inner ring conical wall 7242, with a diameter of d4 and a quantity of N4.

[0081] like Figure 3 As shown, a flame tube assembly 5 according to an embodiment of the present invention includes an outer flame tube wall 51, an inner flame tube wall 52, and two flame tube side walls 53. Both the outer flame tube wall 51 and the inner flame tube wall 52 are arc-shaped, with the arc radius of the outer flame tube wall 51 being larger than that of the inner flame tube wall 52. The two flame tube side walls 53 are respectively connected to the two ends of the outer flame tube wall 51 and the inner flame tube wall 52, and extend radially to connect with the second outer ring casing 331 and the second inner ring casing 332. The flame tube assembly 5 also includes a plurality of flame tube heads, which are located within the area enclosed by the outer flame tube wall 51, the inner flame tube wall 52, and the two flame tube side walls 53, and are uniformly arranged circumferentially along the flame tube assembly 5 to receive diffused airflow.

[0082] An embodiment of the present invention provides a multi-head sector-shaped combustion chamber test piece with a silencing cavity, further comprising a fuel nozzle 4, an ignition electrode 61, and a pulsating pressure sensor 62, all mounted on a second outer ring casing 331. The fuel nozzle 4 is connected to a flame tube assembly 5, injecting fuel into the flame tube assembly 5 to mix and burn with the diffused airflow. The ignition electrode 61 is mounted on the flame tube head at the middle position, used to ignite the fuel and diffused airflow. The pulsating pressure sensor 62 is mounted on the flame tube heads at non-middle positions, used to measure the dynamic gas pressure during combustion. Figure 3 The diagram shows five flame tube heads and four pulse pressure sensors 62. The ignition nozzle 61 is positioned directly above the center of the middle flame tube head, and the four pulse pressure sensors 62 are positioned directly above the centers of the other four flame tube heads. Of course, the number of flame tube heads and the number of pulse pressure sensors 62 can be adjusted according to actual conditions.

[0083] This invention also proposes a noise reduction adjustment method, which is applied to the above-mentioned multi-head sector-shaped combustion chamber test piece with a noise reduction cavity, and includes the following steps:

[0084] The frequency of the first outer ring Helmoltz resonator is adjusted by changing the volume of the third cavity, the diameter and number of the first outer ring damping holes, so that the frequency of the first outer ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe.

[0085] The frequency of the first inner ring Helmoltz resonator is adjusted by changing the volume of the fourth cavity, the diameter and number of the first inner ring damping holes, so that the frequency of the first inner ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe.

[0086] The frequency of the second outer ring Helmoltz resonator is adjusted by changing the volume of the fifth cavity, the diameter and number of the second outer ring damping holes, so that the frequency of the second outer ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly.

[0087] The frequency of the second inner ring Helmoltz resonator is adjusted by changing the volume of the sixth cavity, the diameter and number of the second inner ring damping holes, so that the frequency of the second inner ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly.

[0088] The following section will elaborate on the methods for noise reduction adjustment.

[0089] The airflow from the inlet pipe 1 of the test apparatus is unstable, and its characteristic flow frequency, i.e., the incoming flow disturbance frequency, is f. up The disturbance propagates downstream via convection. The frequency of the incoming flow disturbance is f. up The calculation formula is: Where Sr is the Strouhal number, U up D is the average flow velocity of intake pipe 1. up Let Sr be the characteristic diameter of intake pipe 1. The Strouhal number Sr can be obtained through cold eddy simulation.

[0090] The inherent thermoacoustic instability within the combustion chamber flame tube 5 has a characteristic frequency, i.e., the combustion oscillation frequency, f. c It propagates upstream or downstream in the form of sound waves, and undergoes absorption, emission, and scattering at the solid wall boundary. The combustion oscillation frequency is f. c It can be obtained through three-dimensional thermoacoustic finite element method, where the flame transfer function required in the three-dimensional thermoacoustic finite element method tool can be obtained through thermal eddy simulation.

[0091] The third cavity V1, the fourth cavity V2, the fifth cavity V3, and the sixth cavity V4 respectively form a first outer ring Helmoltz resonator, a first inner ring Helmoltz resonator, a second outer ring Helmoltz resonator, and a second inner ring Helmoltz resonator. These Helmoltz resonators can eliminate disturbances at the corresponding frequencies.

[0092] The frequency f of the Helmoltz resonator H,i The calculation formula is: Where: c is the speed of sound, which is related to the temperature of the incoming airflow to the test specimen; N i d i These represent the number of openings and the diameter of the openings in the acoustically damped orifice wall, respectively; V i Let i be the volume of the i-th cavity; the value of i can be 1, 2, 3 or 4.

[0093] When i = 1 or 2, by designing N i d i and V i , making f H,i with f up Similarly, this is to reduce flow instability disturbances from upstream of the intake duct, thereby reducing the convection of these disturbances to the combustion chamber and triggering thermoacoustic instability.

[0094] When i = 3 or 4, by designing N i d i and V i , making f H,i with f c Similarly, this reduces the emission of sound waves from the inherent thermoacoustic instability of the combustion chamber onto the cone wall, and reduces the impact of reflected waves on the combustion chamber flame tube.

[0095] In short, by designing multiple acoustic cavities between the intake assembly 7 and the load-bearing casing, an array of acoustic damping holes is opened on its wall, and the characteristic frequency of the acoustic cavity upstream of the intake assembly is the same as the incoming flow disturbance frequency, while the characteristic frequency of the acoustic cavity downstream of the intake assembly is the same as the combustion oscillation frequency, the purpose of suppressing combustion oscillation is achieved through acoustic design.

[0096] It should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. Such expressions are only for the purpose of making the description of the present invention simpler and more convenient, and do not indicate or imply that the component referred to must have a specific orientation or be constructed and operated in a specific orientation.

[0097] Furthermore, in this application, unless otherwise expressly specified and limited, terms such as "installation," "connection," and "setting" should be interpreted broadly. For example, "connection" 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; it can also refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In addition, the terms "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0098] The present invention has the following beneficial effects:

[0099] 1) This invention can effectively suppress combustion oscillations, help maintain stable gas flow in the combustion chamber, reduce noise during combustion chamber operation, maintain combustion efficiency, and ensure that engine performance remains at the design level, thereby ensuring that the combustion chamber operating conditions can achieve the expected verification goals.

[0100] 2) This invention helps to reduce the vibration amplitude of combustion chamber components and related structures, improve the stability of the entire combustion test, maintain the controllability of the engine under various operating conditions, reduce the risk of instability, thereby reducing the risk of fatigue and stress concentration, and improving the reliability and life of the structure.

[0101] The embodiments described above are merely further illustrations of the present invention and are not intended to limit the present invention in any other way. The present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding modifications and changes based on the present invention, but all such modifications and changes should fall within the protection scope of the present invention.

Claims

1. A multi-head sector-shaped combustion chamber test specimen with a sound-absorbing cavity, characterized in that, include: The load-bearing casing is located between the intake pipe and the exhaust pipe; An air intake assembly, disposed within the load-bearing casing, introduces and diffuses airflow. The air intake assembly includes a rectifier pipe and a diffuser pipe. The rectifier pipe includes an inlet baffle and a rectifier tube. The diffuser pipe includes a fixed plate, a guide pipe, a diffuser tube, and a conical wall. The inlet baffle includes two vertical plates, one end of which is connected to the load-bearing casing, and the other end of which is connected to one end of the rectifier tube. The other end of the rectifier tube is connected to the fixed plate. The upper and lower ends of the fixed plate are respectively connected to the load-bearing casing. One end of the guide pipe is connected to the fixed plate, and the other end is connected to one end of the diffuser tube. The conical wall is circumferentially arranged around the outer wall of the diffuser tube and close to the inner wall of the load-bearing casing. The rectifier tube has several first acoustic damping holes, and the conical wall has several second acoustic damping holes. The flame tube assembly is disposed within the load-bearing casing and located at the exhaust port of the air intake assembly, receiving diffused airflow; The rectifier pipe and the load-bearing casing form a first Helmoltz resonator, the frequency of which is the same as the frequency of the incoming flow disturbance in the intake pipe. The diffuser pipe and the load-bearing casing form a second Helmoltz resonator, the frequency of which is the same as the combustion oscillation frequency in the flame tube assembly.

2. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 1, characterized in that, The load-bearing casing includes a first transition casing, a bleed air section casing, a test section casing, a measurement section casing, and a second transition casing; One end of the first adapter casing is connected to the intake pipe, and the other end is connected to one end of the bleed section casing. The other end of the bleed section casing is connected to one end of the test section casing. The other end of the test section casing is connected to one end of the measurement section casing. The other end of the measurement section casing is connected to one end of the second adapter casing. The other end of the second adapter casing is connected to the exhaust pipe. The cross-section of the first adapter casing gradually decreases from one end connected to the intake pipe to the other end connected to the bleed section casing. The cross-sections of the bleed section casing, the test section casing, and the measurement section casing remain unchanged along the axial direction. The cross-section of the second adapter casing gradually increases from one end connected to the measurement section casing to the other end connected to the exhaust pipe.

3. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 2, characterized in that, Both the bleed section casing and the test section casing have a fan-shaped cross-section; The bleed section casing includes a first outer ring casing, a first inner ring casing, and two first side casings. The first outer ring casing and the first inner ring casing are both arc-shaped. The arc radius of the first outer ring casing is larger than that of the first inner ring casing. The two first side casings are both semicircles, which are respectively connected to the two ends of the first outer ring casing and the first inner ring casing, forming a closed pipeline with the first outer ring casing and the first inner ring casing. The test section casing includes a second outer ring casing, a second inner ring casing, and two second side casings. Both the second outer ring casing and the second inner ring casing are arc-shaped, with the arc radius of the second outer ring casing being larger than that of the second inner ring casing. The two second side casings are semicircles, respectively connecting the two ends of the second outer ring casing and the second inner ring casing, forming a closed pipeline with the second outer ring casing and the second inner ring casing.

4. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 3, characterized in that, The rectifier pipe is disposed inside the bleed section casing. The rectifier pipe also includes a mounting plate. The inlet baffle also includes two horizontal plates, which face the first outer ring casing and the first inner ring casing respectively, and have a gap G1 between them. One end of each of the two vertical plates is connected to the horizontal plate, and the other end is connected to one end of the rectifier pipe. The other end of the rectifier pipe is connected to the mounting plate. The cross-section of the rectifier pipe remains unchanged along the axial direction. The mounting plate is bolted to the fixing plate.

5. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 3, characterized in that, The rectifier tube has a fan-shaped cross-section and includes an outer ring rectifier plate, an inner ring rectifier plate, and two side rectifier plates. The first acoustic damping hole includes a first outer ring damping hole and a first inner ring damping hole. Both the outer ring rectifier plate and the inner ring rectifier plate are arc-shaped, and the arc radius of the outer ring rectifier plate is larger than that of the inner ring rectifier plate. The first outer ring damping hole is disposed on the outer ring rectifier plate, and the first inner ring damping hole is disposed on the inner ring rectifier plate. Two side rectifier plates are respectively connected to the two ends of the outer ring rectifier plate and the inner ring rectifier plate, and extend radially to connect with the first outer ring casing and the first inner ring casing; The outer ring rectifier plate, the first outer ring casing, and the two side rectifier plates form a third cavity V1, which forms a first outer ring Helmoltz resonator. The inner ring rectifier plate, the first inner ring casing, and the two side rectifier plates form a fourth cavity V2, which forms a first inner ring Helmoltz resonator.

6. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 3, characterized in that, The diffuser pipe is located inside the test section casing, and the two ends of the fixing plate are bolted to the second outer ring casing and the second inner ring casing, respectively. The cross-section of the guide tube is fan-shaped and remains unchanged along the axial direction. The guide tube includes an outer ring guide plate, an inner ring guide plate, and two side guide plates. Both the outer ring guide plate and the inner ring guide plate are arc-shaped. The arc radius of the outer ring guide plate is larger than that of the inner ring guide plate. The two side guide plates are respectively connected to the two ends of the outer ring guide plate and the inner ring guide plate, and extend radially to connect with the second outer ring casing and the second inner ring casing. The other end of the diffuser tube faces the flame tube assembly. The cross-section of the diffuser tube gradually increases from the end connected to the guide tube to the other end facing the flame tube assembly, thereby diffuser and compressing the airflow and introducing the diffused airflow into the flame tube assembly. The outer ring guide plate, the second outer ring casing, and the two side guide plates form a fifth cavity V3, which forms a second outer ring Helmoltz resonator. The inner ring guide plate, the second inner ring casing, and the two side guide plates form a sixth cavity V4, which forms a second inner ring Helmoltz resonator.

7. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 3, characterized in that, The conical wall includes an outer ring conical wall and an inner ring conical wall. The outer ring conical wall is close to the second outer ring casing and has a gap G2 between it and the second outer ring casing. The inner ring conical wall is close to the second inner ring casing and has a gap G2 between it and the second inner ring casing. The second acoustic damping orifice includes a second outer ring damping orifice and a second inner ring damping orifice. The second outer ring damping orifice is disposed on the outer ring conical wall, and the second inner ring damping orifice is disposed on the inner ring conical wall.

8. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 3, characterized in that, The flame tube assembly includes an outer wall of the flame tube, an inner wall of the flame tube, and two side walls of the flame tube. Both the outer wall and the inner wall of the flame tube are arc-shaped, and the arc radius of the outer wall of the flame tube is greater than that of the inner wall of the flame tube. The two flame tube sidewalls are respectively connected to the two ends of the outer wall of the flame tube and the inner wall of the flame tube, and extend radially to connect with the second outer ring casing and the second inner ring casing; The flame tube assembly also includes multiple flame tube heads, which are located within the area enclosed by the outer wall of the flame tube, the inner wall of the flame tube, and the two side walls of the flame tube, and are evenly arranged along the circumference of the flame tube assembly.

9. The multi-head sector-shaped combustion chamber test specimen with a silencing cavity according to claim 8, characterized in that, It also includes a fuel injector, an ignition nozzle, and a pulsating pressure sensor, all of which are mounted on the second outer ring casing. The fuel nozzle is connected to the flame tube assembly, and fuel is injected into the flame tube assembly to mix and burn with the diffused airflow. The ignition nozzle is installed on the flame tube head in the middle position and is used to ignite the fuel and diffuse the airflow; The pulsating pressure sensing components are installed on the flame tube head at a non-central position to measure the dynamic pressure of the gas during combustion.

10. A noise reduction adjustment method, characterized in that, The method, applied to the multi-head sector-shaped combustion chamber test specimen with a silencing cavity as described in any one of claims 1-9, includes the following steps: The frequency of the first outer ring Helmoltz resonator is adjusted by changing the volume of the third cavity, the diameter and number of the first outer ring damping holes, so that the frequency of the first outer ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe. The frequency of the first inner ring Helmoltz resonator is adjusted by changing the volume of the fourth cavity, the diameter and number of the first inner ring damping holes, so that the frequency of the first inner ring Helmoltz resonator is the same as the frequency of the incoming flow disturbance in the intake pipe. The frequency of the second outer ring Helmoltz resonator is adjusted by changing the volume of the fifth cavity, the diameter and number of the second outer ring damping holes, so that the frequency of the second outer ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly. The frequency of the second inner ring Helmoltz resonator is adjusted by changing the volume of the sixth cavity, the diameter and number of the second inner ring damping holes, so that the frequency of the second inner ring Helmoltz resonator is the same as the combustion oscillation frequency in the flame tube assembly.

Images