Precise excitation test device of laminar flame transverse and longitudinal superposition sound field

Abstract

The invention discloses a precise excitation test device for a laminar flame transverse and longitudinal superposition sound field, which belongs to the technical field of combustion test and acoustics and comprises a sound wave excitation system, a combustor system and an optical shooting system. The sound wave excitation system can simultaneously generate and independently regulate and control transverse and longitudinal sound fields through a signal generator, a power amplifier and four symmetrically-arranged loudspeakers, and various acoustic excitation modes including transverse standing waves, longitudinal standing waves and transverse and longitudinal superposed sound fields are achieved. The combustor system is of a coaxial co-flow structure, fuel and air supply is accurately controlled through a mass flow controller, and stable laminar flame is formed. The optical shooting system is used for recording dynamic response of the flame under sound field excitation; according to the invention, a complex multidirectional acoustic environment in a real combustion chamber can be highly restored, accurate and repeatable tests of combustion characteristics and stability of laminar flame in a superposed sound field are realized, and an effective experimental platform is provided for combustion acoustic regulation and thermoacoustic instability research.

Description

Technical Field

[0001] This invention belongs to the field of combustion testing and acoustic technology, and in particular relates to a precise excitation test device for laminar flame transverse and longitudinal superimposed sound fields. Background Technology

[0002] In the energy and power sector, the combustion efficiency and operational stability of high-intensity power systems directly affect the performance and service life of core power units. The thermoacoustic instability within the combustion chamber of these core power units has become a key bottleneck restricting technological upgrades in this field. When thermoacoustic instability occurs, the sound waves generated by combustion are reflected by the internal walls of the combustion chamber, and these reflected sound waves then act on the flame again. At certain sound wave frequencies or amplitudes, this can lead to poor combustion performance and even severely damage the internal structure of the combustion chamber. However, proper acoustic field organization can promote fuel-air mixing and enhance heat and mass transfer. In actual combustion chambers, the self-excited oscillation signals caused by thermoacoustic instability are often masked by interference signals such as combustion noise and structural vibration, resulting in an extremely low signal-to-noise ratio. Furthermore, the high-temperature and high-pressure working environment of the combustion chamber limits the placement and long-term operation of high-precision sensors, making it difficult to achieve synchronous and accurate measurement of acoustic field parameters and combustion states. Therefore, the research method of applying external acoustic excitation to the flame has been widely used by scholars. Based on sound wave propagation characteristics, common sound wave forms in combustion systems include traveling waves and standing waves. In a real engine combustion chamber, traveling waves and standing waves do not exist independently, but rather superimpose and influence each other, forming a complex acoustic field environment that directly affects flame stability and combustion performance. However, current research is limited to applying a single acoustic excitation to the flame, which cannot realistically reproduce the complex acoustic field environment inside the engine combustion chamber. This leads to a certain difference between the flame response patterns obtained in experiments and actual engineering conditions, making it difficult for the research results to directly guide the design optimization of the combustion system.

[0003] Therefore, in view of the limitations of existing single-direction acoustic excitation devices, this invention proposes a laminar flow flame test device that can accurately superimpose the transverse standing wave sound field and the longitudinal traveling wave sound field. It can construct a multi-directional superimposed sound field environment with highly controllable acoustic conditions, and provide a test platform for the acoustic control of jet flame combustion. Summary of the Invention

[0004] The purpose of this invention is to provide a precise excitation test device for the superimposed sound field of laminar flames, which has the advantages of reasonable structure, precise sound field control and comprehensive monitoring. It realizes the controllable test of multi-directional sound wave excitation of laminar flames, can effectively reproduce the complex multi-directional sound field environment in the combustion chamber of an actual engine, and provides a reference for revealing the interaction mechanism between superimposed sound field and laminar flame.

[0005] To achieve the above objectives, the present invention provides a precise excitation test device for the superimposed sound field of laminar flame, comprising: a burner system, an acoustic excitation system, and an optical imaging system; The burner system is used to generate a stable laminar flame and includes a coaxial burner, a fuel supply unit, and an air supply unit; The acoustic excitation system includes a signal generator, a power amplifier, and four loudspeakers. The signal output port of the signal generator is connected to the signal input port of the power amplifier via a cable, and the multiple power output channels of the power amplifier are respectively connected to the input interfaces of the left loudspeaker, right loudspeaker, upper loudspeaker, and lower loudspeaker via cables. The left and right speakers are fixed to the test platform by their respective mounting brackets and are arranged horizontally symmetrically about the flame center axis, with their lower edges flush with the burner fuel outlet plane; the upper and lower speakers are fixed by vertical brackets and are arranged vertically coaxially along the flame center axis, with the sound wave radiation centers of the four speakers located in the same plane perpendicular to the flame axis. Optical imaging systems are used to record the dynamic response of flames under acoustic excitation, and include high-speed cameras and computer systems.

[0006] Preferably, the fuel supply unit includes a fuel cylinder, a first pressure reducing valve, a fuel-side mass flow controller, and a fuel pipeline; the outlet of the fuel cylinder is sequentially connected to the inlet of the first pressure reducing valve via a fuel pipeline with a connector, the outlet of the first pressure reducing valve is connected to the inlet of the fuel-side mass flow controller, and the outlet of the fuel-side mass flow controller is connected to the inlet of the fuel straight pipe of the coaxial burner.

[0007] Preferably, the coaxial burner consists of an internal fuel straight pipe and an external annular air passage arranged coaxially, and the two are fixed together by a mechanical structure to maintain an annular gap.

[0008] Preferably, the air supply unit includes an air cylinder, a second pressure reducing valve, an air-side mass flow controller, and an air duct; wherein, the outlet of the air cylinder is sequentially connected to the inlet of the second pressure reducing valve via an air duct with a connector, the outlet of the second pressure reducing valve is connected to the inlet of the air-side mass flow controller, and the outlet of the air-side mass flow controller is connected to the inlet of the annular air passage of the coaxial burner.

[0009] Preferably, the data output interface of the high-speed camera is connected to the data acquisition card or corresponding input interface of the computer system via a data communication cable, for transmitting the captured flame image sequence to the computer system for storage and processing.

[0010] Preferably, the signal generator is a multi-channel independently controllable device, and the waveform, frequency, amplitude and phase parameters of each output channel can be set independently. It drives the specified loudspeaker through the corresponding channel of the power amplifier, thereby realizing multiple sound field excitation modes such as transverse standing wave, longitudinal standing wave, superposition of transverse and longitudinal standing waves, superposition of transverse standing wave and longitudinal traveling wave, and single traveling wave.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) By constructing a transverse and longitudinal sound wave excitation system composed of four loudspeakers and placing the sound wave radiation center in the same plane perpendicular to the flame axis, the present invention achieves precise superposition and spatial coordination of the transverse and longitudinal sound fields, solves the problem that traditional test devices can only apply sound wave excitation in a single direction and cannot truly simulate the complex multi-directional sound field environment in the engine combustion chamber, and significantly improves the correspondence between the test scenario and the real working conditions. (2) The present invention uses a multi-channel independently controllable signal generator and power amplifier to achieve independent adjustment of the frequency, amplitude and phase of the sound wave of each loudspeaker, so that the sound field parameters have high controllability and repeatability, overcome the limitations of unstable acoustic conditions and difficulty in quantitative control in traditional acoustic excitation test, and improve the accuracy and reliability of test data. (3) This invention integrates a coaxial burner and a high-precision mass flow control system, combined with a high-speed camera optical imaging device, to achieve stable generation and synchronous observation of the laminar flame morphology and dynamic response under precise acoustic excitation, providing a comprehensive, intuitive and quantifiable experimental means to reveal the mechanism of the interaction between superimposed sound field and flame.

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of a precise excitation test device for a laminar flame transverse and longitudinal superimposed sound field provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a standing wave sound field provided in an embodiment of the present invention; Figure Labels 1. Signal generator; 2. Power amplifier; 3. Left speaker; 4. Right speaker; 5. Coaxial burner; 6. Air-side mass flow controller; 7. Second pressure reducing valve; 8. Fuel-side mass flow controller; 9. First pressure reducing valve; 10. Fuel pipe; 11. Air pipe; 12. Air cylinder; 13. Fuel cylinder; 14. High-speed camera; 15. Computer system; 16. Fuel straight pipe; 17. Upper speaker; 18. Lower speaker; 19. Annular air passage. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0015] It should be noted that the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0016] Similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0017] In the description of this invention, 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, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0018] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] This embodiment provides a precise excitation test device for the superimposed sound field of laminar flame, the structure of which is as follows: Figure 1 As shown, it mainly includes a burner system, an acoustic excitation system, and an optical imaging system.

[0020] The burner system is used to generate a stable laminar flame and includes a coaxial burner 5, a fuel supply unit, and an air supply unit. The coaxial burner 5 is composed of an internal fuel straight pipe 16 and an external annular air passage 19, which are coaxially connected and fixed by a mechanical structure to maintain a uniform annular gap.

[0021] The fuel supply unit includes a fuel cylinder 13, a first pressure reducing valve 9, a fuel-side mass flow controller 8, and a fuel pipeline 10. The outlet of the fuel cylinder 13 is connected to the inlet of the first pressure reducing valve 9 via the fuel pipeline 10. The outlet of the first pressure reducing valve 9 is connected to the inlet of the fuel-side mass flow controller 8 via the fuel pipeline 10. The outlet of the fuel-side mass flow controller 8 is connected to the inlet of the fuel straight pipe 16 of the coaxial burner 5 via the fuel pipeline 10.

[0022] The air supply unit includes an air cylinder 12, a second pressure reducing valve 7, an air-side mass flow controller 6, and an air duct 11. The outlet of the air cylinder 12 is connected to the inlet of the second pressure reducing valve 7 via the air duct 11. The outlet of the second pressure reducing valve 7 is connected to the inlet of the air-side mass flow controller 6 via the air duct 11. The outlet of the air-side mass flow controller 6 is connected to the inlet of the annular air passage 19 of the coaxial burner 5 via the air duct 11.

[0023] The acoustic excitation system is used to apply a controllable superimposed sound field in the transverse and longitudinal directions to the flame. It consists of a signal generator 1, a power amplifier 2, a left speaker 3, a right speaker 4, an upper speaker 17, and a lower speaker 18.

[0024] The signal output port of signal generator 1 is connected to the signal input port of power amplifier 2 via a cable. The four power output channels of power amplifier 2 are connected to the input terminals of four speakers via speaker cables. Left speaker 3 and right speaker 4 are fixed to the optical platform surface via mounting brackets with grooves. They are arranged in a strictly horizontally symmetrical manner about the flame center axis. Their horizontal spacing and symmetry can be finely adjusted using knobs to ensure their lower edges are flush with the burner fuel outlet plane. Upper speaker 17 and lower speaker 18 are fixed via vertical brackets with scales, allowing for precise height adjustment to ensure they are vertically aligned along the flame center axis. Finally, the four speakers are adjusted so that they are located in the same plane perpendicular to the flame axis. The two symmetrically placed speakers each generate two traveling waves with the same frequency and amplitude but opposite propagation directions. The superposition of these two traveling waves forms a standing wave. When the diameter of the fuel straight pipe 16 is less than 0.5 times the wavelength of the sound wave, the sound wave propagating within the fuel straight pipe 16 can be considered a plane harmonic wave.

[0025] In this embodiment, signal generator 1 is a four-channel independently controllable device, allowing independent setting of the output frequency, amplitude, and phase of each channel. The standing wave sound field is as follows: Figure 2As shown, the transverse and longitudinal acoustic wave excitation system can realize multiple acoustic wave operating modes, as detailed below: Lateral standing wave mode: When the left speaker 3 and the right speaker 4 are turned on at the same time, a lateral standing wave sound field excitation mode can be realized. The flame is at the antinode of the wave, and the amplitude of the sound pressure is twice that of the single-column traveling wave.

[0026] Longitudinal standing wave mode: When the upper speaker 17 and the lower speaker 18 are turned on at the same time, the longitudinal standing wave mode can be realized.

[0027] Transverse and longitudinal standing wave mode: When the left speaker 3, right speaker 4, upper speaker 17, and lower speaker 18 are turned on simultaneously, a complex sound field can be formed by the superposition of transverse and longitudinal standing waves.

[0028] Transverse standing wave + longitudinal traveling wave mode: The left speaker 3 and the right speaker 4 are turned on first, and then the upper speaker 17 is turned on, which can realize a complex sound field where transverse standing waves and traveling waves coexist. Single-sided traveling wave mode: When any one of the left speaker 3, right speaker 4 and upper speaker 17 is turned on, a simple traveling wave excitation can be applied to the flame.

[0029] An optical imaging system, comprising a high-speed camera 14 and a computer system 15, is used to record the dynamic response of the flame under acoustic excitation. The high-speed camera 14 is mounted on the experimental platform and is equipped with an adjustable-focus lens, the central axis of which is aligned with the flame stabilization region above the fuel outlet of the coaxial burner 5. The data output interface of the high-speed camera 14 is connected via a data cable to the built-in image acquisition card or a corresponding interface of the computer system 15.

[0030] The specific working method of this embodiment is as follows: Test preparation phase: Check the connection status of each system, ensure that the burner system piping is well sealed, and that the acoustic excitation system and optical imaging device are unobstructed.

[0031] Flame generation stage: Open the valves of fuel cylinder 13 and air cylinder 12. The fuel-side mass flow controller 8 and the air-side mass flow controller 6 precisely control the flow rates of the two gases according to preset parameters, so that the fuel and air form a stable ratio of co-flowing gas in the coaxial burner 5. The fuel is ignited by the ignition device, and a laminar flame with a regular shape is generated at the burner outlet. It runs continuously for 5-10 minutes to ensure that the flame state is stable.

[0032] Acoustic excitation stage: The corresponding acoustic operating mode can be selected according to the acoustic field being studied. The acoustic excitation system is activated, and signal generator 1 outputs an electrical signal to power amplifier 2 according to the preset acoustic frequency and amplitude. Multidirectional acoustic waves act on the flame, effectively replicating the coupling effect of combustion and acoustic waves within a real engine combustion chamber.

[0033] Data acquisition phase: Start the optical imaging device, set the shooting frame rate of the high-speed camera 14, and start continuous shooting at the core area of ​​the flame. Transmit the morphological image of the flame under the superimposed sound field and action to the computer system 15 in real time.

[0034] In summary, this invention provides a precise excitation test device for the superimposed sound fields of laminar flames. It achieves precise superposition and flexible construction of the transverse and longitudinal sound fields through a symmetrically arranged four-speaker array, realizes controllable excitation of acoustic parameters through a multi-channel independently adjustable signal generation and amplification system, and achieves high-resolution observation of stable flame generation and dynamic response through an integrated coaxial burner and high-speed optical imaging system. This forms a complete, precise, and comprehensive combustion acoustic test solution, which significantly improves the experimental capability and reliability of studying the combustion characteristics of laminar flames in complex multi-directional sound field environments.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A precise excitation test device for the superimposed sound field of laminar flame, characterized in that, include: Combustion system, acoustic excitation system, and optical imaging system; The burner system is used to generate a stable laminar flame and includes a coaxial burner, a fuel supply unit, and an air supply unit; The acoustic excitation system includes a signal generator, a power amplifier, and four loudspeakers. The signal output port of the signal generator is connected to the signal input port of the power amplifier via a cable, and the multiple power output channels of the power amplifier are respectively connected to the input interfaces of the left loudspeaker, right loudspeaker, upper loudspeaker, and lower loudspeaker via cables. The left and right speakers are fixed to the test platform by their respective mounting brackets and are arranged horizontally symmetrically about the flame center axis, with their lower edges flush with the burner fuel outlet plane; the upper and lower speakers are fixed by vertical brackets and are arranged vertically coaxially along the flame center axis, with the sound wave radiation centers of the four speakers located in the same plane perpendicular to the flame axis. Optical imaging systems are used to record the dynamic response of flames under acoustic excitation systems, and include high-speed cameras and computer systems.

2. The precise excitation test device for the superimposed sound field of laminar flame according to claim 1, characterized in that: The fuel supply unit includes a fuel cylinder, a first pressure reducing valve, a fuel-side mass flow controller, and a fuel pipeline. The outlet of the fuel cylinder is sequentially connected to the inlet of the first pressure reducing valve via a fuel pipeline with a connector. The outlet of the first pressure reducing valve is connected to the inlet of the fuel-side mass flow controller, and the outlet of the fuel-side mass flow controller is connected to the inlet of the fuel straight pipe of the coaxial burner.

3. The precise excitation test device for the superimposed sound field of laminar flame according to claim 2, characterized in that: The coaxial burner consists of an internal fuel straight pipe and an external annular air passage arranged coaxially, and the two are fixed together by a mechanical structure to maintain an annular gap.

4. The precise excitation test device for the superimposed sound field of laminar flame according to claim 3, characterized in that: The air supply unit includes an air cylinder, a second pressure reducing valve, an air-side mass flow controller, and an air duct; wherein, the outlet of the air cylinder is sequentially connected to the inlet of the second pressure reducing valve via an air duct with a connector, the outlet of the second pressure reducing valve is connected to the inlet of the air-side mass flow controller, and the outlet of the air-side mass flow controller is connected to the inlet of the annular air passage of the coaxial burner.

5. The precise excitation test device for the superimposed sound field of laminar flame according to claim 4, characterized in that: The high-speed camera's data output interface is connected to the computer system's data acquisition card or corresponding input interface via a data communication cable, used to transmit the captured flame image sequence to the computer system for storage and processing.

6. The precise excitation test device for the superimposed sound field of laminar flame according to claim 5, characterized in that: The signal generator is a multi-channel independently controllable device. The waveform, frequency, amplitude and phase parameters of each output channel can be set independently. It drives the specified loudspeaker through the corresponding channel of the power amplifier, thereby realizing multiple sound field excitation modes such as transverse standing wave, longitudinal standing wave, transverse and longitudinal standing wave superposition, transverse standing wave and longitudinal traveling wave superposition, and single traveling wave.

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