A combustion chamber and method for suppressing oscillatory combustion based on 4D printing technology

Abstract

The application provides a combustion chamber and method for suppressing oscillating combustion based on 4D printing technology, the combustion chamber comprises a flame tube casing and a flame tube head, a flame tube is coaxially arranged in the flame tube casing, an air passage is formed between the outer wall of the flame tube and the flame tube casing, during the combustion process, the intelligent corrugated unit arranged on the inner wall of the flame tube improves the speed of sound wave attenuation and dissipation at the boundary, restrains the coupling of pulsating sound wave and pressure fluctuation, and then suppresses the oscillating combustion in the initial stage, and the intelligent corrugated unit made by the 4D printing technology can produce surface deformation under the excitation of the predetermined excitation temperature, and reduces the interference of the intelligent corrugated unit on normal combustion in the stable combustion process.

Description

Technical Field

[0001] The present invention belongs to the technical field of combustion chamber structure design, and specifically relates to a combustion chamber and method for suppressing oscillating combustion based on 4D printing technology. Background Art

[0002] Combustion is a common way of energy conversion. In aviation, aerospace and other engines, combustion occurs in the combustion chamber. The high temperature environment in the combustion chamber is conducive to the formation of nitrogen oxides (NOx), and the emission of nitrogen oxides will cause serious environmental pollution. With the improvement of nitrogen oxide emission standards, lean premixed combustion technology has been widely used because it can effectively control nitrogen oxide emissions. However, this technology is prone to combustion instability. Because the gradient of heat release in its equivalence ratio range is relatively large, any small disturbance can easily cause heat release pulsation, thereby inducing oscillatory combustion. Oscillatory combustion can cause resonance in the combustion chamber or components and cause damage, seriously affecting the safety and reliability of the engine. In order to meet both emission requirements and engine reliability requirements, it is urgent to address the problem of oscillatory combustion.

[0003] In recent years, domestic and foreign scholars have proposed many solutions to this problem, but the following problems still exist:

[0004] 1. Oscillating combustion is a complex physical and chemical phenomenon that couples combustion heat release, turbulent pulsation, and acoustic pressure resonance. Current mature methods for solving the problem of oscillating combustion focus on weakening the effect after oscillation occurs, but fail to truly solve the problem from the root.

[0005] 2. The effect of weakening after oscillation is generated is currently very limited. It can only respond according to the predetermined circuit and is confined to a narrow oscillation frequency band, resulting in the suppression of oscillating combustion failing to adapt to complex and changing working environments. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing lean premixed combustion technology cannot fundamentally suppress the oscillating combustion phenomenon during application, and the existing suppression means cannot adapt to complex and changeable combustion conditions, seriously affecting the safety and reliability of the engine.

[0007] In order to solve the above technical problems, the present invention provides a combustion chamber for suppressing oscillating combustion based on 4D printing technology, comprising a flame tube casing and a flame tube head, wherein a flame tube is coaxially installed in the flame tube casing, an air channel is formed between the outer wall of the flame tube and the flame tube casing, a mixing hole is provided at one section of the exhaust outlet of the flame tube, and an intelligent wrinkle unit composed of shape memory alloy is provided on the inner wall of the flame tube, fixing devices are provided at both ends of the intelligent wrinkle unit, and the intelligent wrinkle unit is fixedly mounted on the inner wall of the flame tube by fixing devices on both sides, and the intelligent wrinkle unit can produce surface deformation under the excitation of a predetermined excitation temperature.

[0008] Furthermore, a plurality of extension traction edges are evenly arranged in the middle section of the smart wrinkle unit, and the smart wrinkle unit can generate directional deformation at the extension traction edges when the surface is extended.

[0009] Furthermore, the intelligent wrinkle unit is made of NiTi shape memory alloy.

[0010] Furthermore, a plurality of intelligent wrinkle units are provided on the inner wall of the flame tube, and the predetermined excitation temperatures of the intelligent wrinkle units are different, and the intelligent wrinkle units are staggeredly arranged according to the gradient of the predetermined excitation temperature values.

[0011] A method for suppressing oscillating combustion based on 4D printing technology, the method using the above-mentioned combustion chamber for suppressing oscillating combustion based on 4D printing technology, specifically comprising the following steps:

[0012] S1: Before combustion, the internal and external temperatures of the flame tube are both ambient temperature, and the intelligent pleated units on the inner wall of the flame tube are densely pleated.

[0013] S2: In the early stages of combustion, the mixed gas enters the flame tube through the combustion chamber head. After ignition and combustion, due to environmental disturbances, heat release becomes unstable, emitting non-steady-state sound waves. The sound waves propagate inside the flame tube to the inner wall of the flame tube. The densely corrugated smart corrugated units on the inner wall of the flame tube absorb the sound waves, suppressing the coupling of pulsating sound waves and pressure fluctuations. As combustion progresses, the temperature in the flame tube rises. When the smart corrugated units reach the preset excitation temperature, surface deformation begins. Under the combined action of the preset extension traction edge and the thermal stress and pressure in the combustion chamber, they gradually extend to a pseudo-smooth state.

[0014] S3: During the steady-state combustion period, the preset excitation temperature values ​​of each intelligent pleated unit are different. If the stable combustion is disturbed again by the outside world, the intelligent pleated unit that has not reached the preset excitation temperature value will absorb the generated sound waves. The intelligent pleated unit will produce a preset deformation according to the temperature change in the flame tube, forming a dynamically stable combustion mechanism.

[0015] The technical effects of the present invention are:

[0016] (1) Compared with the existing combustion chamber, the present invention can suppress oscillating combustion under various complex actual combustion conditions by introducing 4D printing technology. When unstable combustion occurs, the intelligent pleating unit set in the combustion chamber can respond in time, curbing the oscillating combustion in the bud stage and maintaining the dynamic stability of combustion.

[0017] (2) Compared with existing combustion chambers, this combustion chamber is highly compatible with lean premixed combustion technology and can meet both emission requirements and engine reliability requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the schematic diagram of the overall structure of the present application;

[0019] Figure 2 is the schematic diagram of the combined structure of the intelligent wrinkle unit of the present application;

[0020] Figure 3 is the schematic diagram of the intelligent wrinkle unit structure of the present application;

[0021] Figure 4 is the schematic diagram of the change state one of the intelligent wrinkle unit of the present application;

[0022] Figure 5 is the schematic diagram of the change state two of the intelligent wrinkle unit of the present application;

[0023] Figure 6 is the schematic diagram of the change state three of the intelligent wrinkle unit of the present application;

[0024] In the figure: 1, flame tube; 2, fixing device; 3, intelligent wrinkle unit; 4, extension traction edge one; 5, extension traction edge two; 6, mixing hole; 7, air passage; 8, flame tube casing. DETAILED DESCRIPTION

[0025] In order to better explain the present application, so as to be understood, the technical solutions and effects of the present application are described in detail through specific embodiments in combination with the accompanying drawings.

[0026] The working principle of suppressing oscillation combustion based on the 4D printing technology of the present application is as follows:

[0027] 4D printing refers to using "programmable matter" and 3D printing technology to manufacture a three-dimensional object that can self-transform physical properties under a predetermined stimulus. Among them, "programmable matter" refers to matter that can change properties such as shape, density, conductivity, color, optical properties, electromagnetic properties, etc. in a programmed manner. The fourth dimension of 4D printing refers to the shape or performance of the object after being manufactured, which can self-transform.

[0028] Thermoacoustic oscillation coupling Rayleigh criterion points out that in a combustion system, the interaction between the heat release pulsation of the flame and the periodic fluctuation of the sound pressure, when the energy speed provided by the heat release to the sound wave is greater than the speed of the sound wave boundary attenuation and dissipation, makes the combustion thermoacoustic coupling continue, and produces oscillation. The key core idea of the combustion chamber based on the 4D printing technology to suppress oscillation combustion is to improve the speed of sound wave boundary attenuation and dissipation, so that the energy provided by the heat release pulsation to the sound wave is dissipated as much as possible in the boundary impedance link, and the coupling of the pulsation sound wave and the pressure fluctuation is suppressed, and the characteristics of the 4D printing technology are used to reduce the interference of the oscillation suppression component on the normal combustion in the stable combustion process.

[0029] As Figures 1 to 6As shown, a combustion chamber for suppressing oscillating combustion based on 4D printing technology includes a flame tube casing 8 and a flame tube head, a flame tube 1 is coaxially installed in the flame tube casing 8, a mixing hole 6 is provided at one section of the exhaust outlet of the flame tube 1, an air channel 7 is formed between the outer wall of the flame tube 1 and the flame tube casing 12, and an intelligent wrinkle unit 3 composed of NiTi shape memory alloy is provided on the inner wall of the flame tube, a fixing device 2 is provided at both ends of the intelligent wrinkle unit 3, and the intelligent wrinkle unit 3 is fixedly installed on the inner wall of the flame tube 1 by the fixing devices 2 on both sides, the middle section of the intelligent wrinkle unit 3 is provided with an extended traction edge 5 and an extended traction edge 6, and by adjusting the surface wrinkle structure at the extended traction edge, the surface stress resistance of the intelligent wrinkle unit 3 at the extended traction edge is different from that at other positions.

[0030] The smart pleated unit 3 has a shape memory effect. The surface of the smart pleated unit 3 can maintain a dense pleated state at a lower temperature value. The smart pleated unit 3 begins to deform after being stimulated by a predetermined temperature value. The deformation is divided into two processes, such as Figure 4 In the first process shown, the wrinkles on the surface of the smart wrinkle unit 3 begin to extend, and the extended traction edge 1 5 and the extended traction edge 2 6 undergo directional deformation under the action of surface stress; Figure 5 In the second process shown, the surface wrinkles of the intelligent wrinkle unit 3 continue to extend, and finally gradually extend to the shape shown in FIG. Figure 6 The pseudo-smooth state shown reduces the interference of the large-area intelligent pleated unit 3 on the stable combustion during the stable combustion process.

[0031] like Figure 2 As shown, considering the complex and changeable actual combustion conditions, in this embodiment, an intelligent pleated unit combination consisting of 16 intelligent pleated units 3 is provided on the inner wall of the flame tube 1, and the predetermined excitation temperature of each intelligent pleated unit 3 is different. The intelligent pleated units 3 are staggered according to the gradient of the predetermined excitation temperature value, and the intelligent pleated units 3 can undergo preset deformation according to the temperature change in the flame tube 1.

[0032] The specific steps of the present invention for suppressing oscillating combustion based on 4D printing technology are as follows:

[0033] S1: Before combustion, the internal and external temperatures of the flame tube 1 are both at ambient temperature, and the intelligent pleated units 3 on the inner wall of the flame tube 1 are in a densely pleated state;

[0034] S2: In the early stage of combustion, the mixed gas enters the flame tube 1 through the head of the combustion chamber. After ignition and combustion, due to environmental disturbances, the heat release is unstable and acoustic pressure energy is generated. The sound wave propagates in the flame tube 1 to the inner wall of the tube. The intelligent pleated unit 3 on the inner wall of the flame tube 1 can absorb the sound wave through the dense pleats on its surface, thereby suppressing the thermal-acoustic coupling of combustion in the flame tube 1. As the combustion progresses, the temperature in the flame tube 1 increases, and the intelligent pleated unit 3 that reaches the preset excitation temperature value begins to deform on the surface. Under the combined action of the preset extension traction edge and the thermal stress and pressure in the combustion chamber, it gradually extends into a pseudo-smooth state, avoiding new oscillating combustion induced by large-area intelligent pleats, thereby ensuring stable combustion in the early stage of combustion.

[0035] S3: During the steady-state combustion period, the preset excitation temperature values ​​of each intelligent pleated unit 3 are different. If the stable combustion is disturbed again by the outside world, the intelligent pleated unit 3 that has not reached the preset excitation temperature value will absorb the sound waves generated by the disturbance. The intelligent pleated unit 3 will undergo a preset deformation according to the temperature change in the flame tube 1, forming a dynamically stable combustion mechanism.

[0036] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A combustion chamber for suppressing oscillatory combustion based on 4D printing technology, comprising a flame tube casing (8) and a flame tube head, wherein a flame tube (1) is coaxially mounted in the flame tube casing, an air passage (7) is formed between the outer wall of the flame tube and the flame tube casing (8), and a mixing hole (6) is provided at an exhaust outlet of the flame tube (1), characterized in that: An intelligent wrinkle unit (3) composed of a shape memory alloy is provided on the inner wall of the flame tube, fixing devices (2) are provided at both ends of the intelligent wrinkle unit (3), and the intelligent wrinkle unit (3) is fixedly mounted on the inner wall of the flame tube (1) via the fixing devices (2) on both sides, and the intelligent wrinkle unit (3) can undergo surface deformation under the stimulation of a predetermined stimulation temperature; the intelligent wrinkle unit (3) is composed of a NiTi shape memory alloy; A plurality of intelligent wrinkle units (3) are provided on the inner wall of the flame tube, and each intelligent wrinkle unit (3) has a different predetermined excitation temperature, and the intelligent wrinkle units (3) are arranged in a staggered manner according to a gradient of predetermined excitation temperature values; A plurality of extension traction edges are evenly arranged in the middle section of the intelligent wrinkle unit (3), and when the surface of the intelligent wrinkle unit (3) is extended, directional deformation can be generated at the extension traction edge; In the first deformation process, the wrinkles on the surface of the intelligent wrinkle unit (3) begin to extend, and the extended traction edge 1 (4) and the extended traction edge 2 (5) undergo directional deformation under the action of surface stress; in the second process, the wrinkles on the surface of the intelligent wrinkle unit (3) continue to extend; finally, under the combined action of the extended traction edge and the thermal stress and pressure in the combustion chamber, the wrinkles gradually extend into a pseudo-smooth state.

2. A method for suppressing oscillating combustion based on 4D printing technology, the method using the combustion chamber for suppressing oscillating combustion based on 4D printing technology according to claim 1, specifically comprising the following steps: S1: Before combustion, the internal and external temperatures of the flame tube (1) are both at ambient temperature, and the intelligent wrinkle units (3) on the inner wall of the flame tube (1) are in a dense wrinkle state; S2: At the initial stage of combustion, the mixed gas enters the flame tube (1) through the head of the combustion chamber. After ignition and combustion, due to environmental disturbances, the heat release is unstable and non-steady-state sound waves are emitted. The sound waves propagate inside the flame tube (1) to the inner wall of the flame tube (1). The intelligent wrinkle units (3) in a dense wrinkle state on the inner wall of the flame tube (1) absorb the sound waves and suppress the thermal-acoustic coupling of combustion. As the combustion progresses, the temperature in the flame tube (1) rises, and the intelligent wrinkle units (3) that reach the preset excitation temperature value begin to deform on the surface. Under the combined action of the preset extension traction edge and the thermal stress and pressure in the combustion chamber, they gradually extend into a pseudo-smooth state. S3: During the steady-state combustion period, the preset excitation temperature values ​​of the intelligent pleated units (3) are different. If the intelligent pleated units (3) are disturbed again by the outside world during the stable combustion, the intelligent pleated units (3) that have not reached the preset excitation temperature value absorb the generated sound waves. The intelligent pleated units (3) undergo preset deformation according to the temperature change in the flame tube (1), forming a dynamic and stable combustion mechanism.

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