Ignition and flameout modeling combustion chamber test device and system and flame characteristic research method

Abstract

The invention discloses an ignition and flameout modeling combustion chamber testing device and system and a flame characteristic research method, and belongs to the technical field of gas turbine combustion chamber testing. The test device comprises a combustion chamber, a swirler assembly, a fuel nozzle and a plurality of igniter mounting ports respectively corresponding to key flow field positions such as an inner backflow area, a main backflow area and an outer backflow area. A tower-type cyclone or a rotary sliding arc exciter can be selected as the cyclone assembly, and a gas supply system, an oil supply system, an ignition system and an optical test system are integrated in the test system. The method comprises the following steps of: igniting by using different igniters or at different positions, capturing a flame development process by utilizing high-speed imaging, and performing flame mode diagnosis by combining image processing, flame mode diagnosis based on a non-dimensional number, POD, DMD and other methods. Influences of different ignition modes and ignition positions on a flame propagation path, an ignition success rate, ignition delay, flame stability and lean-burn ignition limit and internal physical mechanisms thereof are systematically analyzed.

Description

Technical Field

[0001] The present invention is entitled "Ignition-Quenching Model Combustion Chamber Test Device, System and Flame Characteristics Research Method", which belongs to the field of combustion chamber technology of gas turbine test machine. Background Technology

[0002] In the fields of gas turbines and aero-engines, the ability to ignite and reignite after flameout is a critical requirement for combustion chamber design. Especially under extreme boundary conditions such as high altitude, low temperature, and lean fuel conditions, ignition performance becomes a core indicator determining engine operational stability. To study these complex combustion phenomena, academia and industry have developed various combustion test rigs. Relevant patent documents retrieved: This document, published in China (CN109164203A) on January 8, 2019, discloses a low-heat-loss turbulent combustion visualization test rig with a rotating inflow channel. The rig is primarily used to study turbulent premixed combustion. Its core structure includes a combustion chamber enclosed by quartz glass, a cyclone generator to produce rotating airflow, and a long mixing tube for thorough mixing of fuel gas and air. A particle image velocimetry (PIV) device is installed outside the observation window to measure the combustion conditions within the combustion chamber and transmit the collected data to a connected computer for analysis.

[0003] This document, published in China (CN115728067A) on March 3, 2023, discloses a visual high-pressure combustion chamber test device. The device employs a double-layer quartz glass pressure-bearing structure, which solves the problem that a single layer of quartz glass cannot withstand the full pressure under high temperature and pressure conditions in the combustion chamber. It aims to detect the internal flow field information of the combustion chamber under actual operating conditions using laser diagnostic technology.

[0004] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: Regarding the aforementioned patent document CN109164203A, the design focus of this device is to provide an ideal entry condition for observing stable combustion. It is an observation platform and does not provide a means for systematically studying the impact of the ignition process itself on the subsequent development of the flame. Specifically, it lacks a mechanism to controllably change the initial ignition conditions and cannot establish a clear causal relationship between the ignition location and flame propagation, stabilization, or even extinction.

[0005] The aforementioned patent document CN115728067A focuses on the structural reliability of the device and does not propose a specific design scheme for the transient process of ignition. Therefore, it also lacks a clear causal relationship between the ignition position and the flame propagation, stability and even extinguishing.

[0006] Therefore, existing combustion test benches either focus on providing an ideal observation environment for stable flames or on solving structural load-bearing problems under high-pressure environments. However, neither provides an integrated test platform or a systematic research methodology to establish an integrated test system for the entire process of flame development, from initial flame nucleus formation to extinction, linking ignition spatial location with the flame's evolution. There is an urgent need for a new technical solution that can actively and controllably alter the initial ignition boundary conditions and, combined with advanced diagnostic analysis methods, deeply reveal the intrinsic mechanism by which ignition location affects the entire flame development process. This would provide a scientific basis for optimizing igniter design and expanding the stable operating boundaries of the combustion chamber. Summary of the Invention

[0007] The purpose of this invention is to address the lack of experimental platforms and methods in the existing technology that can systematically study the influence of ignition position on the entire flame development process, and to provide an ignition-quenching modeled combustion chamber test device, system, and flame characteristic research method.

[0008] In a first aspect, the present invention provides a test apparatus for a simulated combustion chamber with flameout capability, comprising: a combustion chamber, wherein a combustion area is defined inside the combustion chamber, and a window for optical observation is provided on the inner side wall of the combustion chamber; A swirler assembly is disposed at one end of the combustion chamber and is used to form an incoming air swirling flow with a specific flow field structure, the flow field structure including an inner recirculation zone, a main recirculation zone and an outer recirculation zone; A fuel nozzle, located at the center of the cyclone assembly, is used to inject fuel into the combustion zone; Multiple igniter mounting ports are respectively disposed at predetermined positions corresponding to the swirling flow field structure, for selectively generating an ignition core at one or more of at least three locations: Location A is located at the widest point of the external reflux zone; Position B is located at the geometric center of the inner recirculation zone; Position C is located at the head of the inner recirculation zone, near the outlet end face of the hydrocyclone assembly.

[0009] Furthermore, the cyclone assembly is a tower cyclone or a tower rotating sliding arc exciter.

[0010] Furthermore, the optical diagnostic window is a quartz glass window, and is fixedly sealed to the combustion chamber by a cover plate and a sealing gasket.

[0011] Furthermore, the outlet pipe section of the combustion chamber is equipped with a back pressure regulating valve, and pressure and temperature measuring points are arranged in the outlet pipe section.

[0012] Furthermore, the test device is mounted on a support platform with a hydraulic tilting and protractor structure, and the support platform can be stopped horizontally, vertically, and at any angle.

[0013] Furthermore, the fuel nozzle is a pressure swirl atomizing nozzle.

[0014] In a second aspect, the present invention also provides a ignition-quenching modeled combustion chamber test system, comprising: the ignition-quenching modeled combustion chamber test device described in the first aspect; An air supply system, wherein the air supply system is connected to the air inlet and fuel nozzle of the test apparatus; A fuel supply system, which is connected to the air inlet and fuel nozzle of the test apparatus; An ignition system for generating an ignition core; the ignition system is connected to one or more igniter mounting ports of the test apparatus; or the ignition system is electrically connected to a tower-type rotating sliding arc exciter in the cyclone assembly. A high-speed imaging system is arranged outside the optical diagnostic window of the test device to acquire continuous time-series images of the combustion area from the generation of the ignition core to the stabilization or extinction of the flame. A data acquisition and processing unit, which is connected to the high-speed imaging system, is used to receive and process the continuous time series images.

[0015] Furthermore, the high-speed imaging system includes a high-speed camera, an image intensifier, and an OH* filter mounted on the image intensifier, wherein the center wavelength of the OH* filter is approximately 308±10nm.

[0016] Furthermore, the system also includes a particle image velocimetry (PIV) system and a laser particle size analyzer (LPSA) for acquiring the cold velocity field and the Sotel average particle size (SMD) of the spray droplets, respectively.

[0017] Furthermore, the data acquisition and processing unit is used to synchronously control and trigger the laser, camera, and ignition signals.

[0018] Furthermore, the ignition system is a high-energy electric spark igniter or a rotary sliding arc exciter.

[0019] Thirdly, the present invention provides a method for studying flame characteristics using the test system described in the second aspect, comprising: A1. As needed for the research, select one of the igniter installation ports A, B or C on the test device and start the ignition system to generate an initial flame core in the combustion zone; or activate the rotating sliding arc exciter to ignite at the head. A2. Using the high-speed imaging system, acquire continuous time-series OH* chemiluminescence images from the moment the initial ignition nucleus is generated until the flame develops into stable combustion or extinguishing; A3. Process the continuous time series images, extract the flame normalized projection area of ​​each frame image, and plot the flame normalized projection area change curve over time. A4. Based on the characteristics of the flame normalized projected area change curve over time, the flame development process is divided into one or more of the following six states: S1: initial flame core, S2: flame core decay, S3: flame propagation, S4: flame dwell, S5: flame growth, S6: stable combustion. A5. Based on the flame development state sequence corresponding to different ignition positions, determine the impact of ignition position on flame propagation path, ignition success rate and ignition delay time.

[0020] Furthermore, it also includes step A6, which combines the pre-obtained cold velocity field and component field data to calculate the Damkolle number Da and Karowitz number Ka on the flame front during the flame propagation process, and determines the turbulent flame mode of the flame front based on Da and Ka, thereby analyzing the physical mechanism that leads to the fire core decay S2 or the flame propagation S3.

[0021] Furthermore, the turbulent flame mode includes one or more of the following: laminar flame mode, pleated flame mode, pouched thickened flame mode, thickened pleated flame mode, potentially extinguishable thickened flame mode, and thick flame mode.

[0022] Furthermore, it also includes step A7: after the flame enters a stable combustion state S6, the intrinsic orthogonal decomposition (POD) method is applied to the acquired continuous time series images to extract the main spatial modes of the flame and their energy distribution, so as to identify the large-scale coherent structure of the flame.

[0023] Furthermore, it also includes step A8: after the flame enters a stable combustion state S6, the dynamic mode decomposition (DMD) method is applied to the acquired continuous time series images to extract the dynamic modes, oscillation frequency and growth rate of the flame in order to evaluate the combustion stability of the flame.

[0024] Furthermore, under constant airflow conditions, by gradually reducing the fuel flow and repeating steps A1 to A5 until ignition fails, the lean ignition limit corresponding to different ignition positions is determined. Furthermore, by analyzing the flame state sequence during the ignition failure process, the failure mode leading to lean combustion and flameout was diagnosed.

[0025] The present invention has at least the following beneficial effects: 1. By combining a tower-type cyclone separator with a pressure cyclone atomizing nozzle, this invention can reproduce the atomization, evaporation, and two-phase mixing process of liquid fuel in the combustion chamber of an aero-engine, providing a physical environment consistent with actual operating conditions for the study of liquid fuel ignition.

[0026] 2. By setting multiple calibrated ignition positions, this invention transforms the ignition position from a fixed one into a movable and controllable variable, enabling researchers to systematically and repeatably study the impact of initial ignition conditions on the entire combustion process, which is impossible with existing technologies.

[0027] 3. This invention can be directly applied to the testing of lean ignition limit (LLO) and lean blowout limit (LBO), and can reveal the specific physical mechanisms that lead to ignition or blowout failure, which is of great significance for optimizing ignition system design and improving overall engine performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the planar structure of the experimental device according to Embodiment 1 of the present invention.

[0029] Figure 2 This is a schematic diagram of the support platform structure according to Embodiment 1 of the present invention.

[0030] Figure 3 This is a schematic diagram of the hydrocyclone structure used in Embodiment 1 of the present invention.

[0031] Figure 4 This is a schematic diagram of the cold flow field in the combustion chamber according to Embodiment 1 of the present invention.

[0032] Figure 5 This is a schematic diagram of the test system according to Embodiment 2 of the present invention.

[0033] Figure 6 This is a schematic diagram of the ignition device according to Embodiment 2 of the present invention.

[0034] Figure 7 This is a schematic diagram of the high-speed imaging system layout according to Embodiment 2 of the present invention.

[0035] Figure 8 This is a schematic diagram of the numerical simulation computational domain in Embodiment 3 of the present invention.

[0036] Figure 9 This is a graph showing the results of the mesh independence verification in Embodiment 3 of the present invention.

[0037] Figure 10 This is a comparison and verification diagram of the cold flow field velocity distribution in numerical simulation and PIV experiment of Embodiment 3 of the present invention.

[0038] Figure 11 This is a schematic diagram of the flame image processing flow in Embodiment 4 of the present invention.

[0039] Figure 12 This is a comparison diagram of ignition characteristics at different ignition positions in Embodiment 4 of the present invention, including... Figure 12 (a) Ignition boundary, Figure 12 (b) Changes in flame area Figure 12 (c) Ignition success rate and delay time.

[0040] Figure 13 This is the curve showing the change of the normalized projected area of ​​the flame over time when ignition at point A is successful in Embodiment 4 of the present invention.

[0041] Figure 14 This is the flame development sequence of the ignition process at point A in Embodiment 4 of the present invention, specifically a comparison image of experimental and numerical simulation.

[0042] Figure 15 This is the curve showing the change of the normalized projected area of ​​the flame over time when ignition at point B is successful in Embodiment 4 of the present invention.

[0043] Figure 16 This is the flame development sequence of the ignition process at point B in Embodiment 4 of the present invention, specifically a comparison image of experimental and numerical simulation.

[0044] Figure 17 This is the curve showing the change of the normalized projected area of ​​the flame over time when ignition at point C is successful in Embodiment 4 of the present invention.

[0045] Figure 18 This is the flame development sequence of the ignition process at point C in Embodiment 4 of the present invention, specifically a comparison image of experimental and numerical simulation.

[0046] Figure 19 This is a schematic diagram of the ideal fire core propagation path assumed for analyzing flame patterns in Embodiment 5 of the present invention, including... Figure 19 (a) Ideal fire core propagation path diagram for ignition at point A. Figure 19 (b) Ideal fire core propagation path diagram for ignition at point B. Figure 19 (c) Ideal fire core propagation path diagram for ignition at point C.

[0047] Figure 20 This is a Borghi diagram used for flame mode diagnosis in Embodiment 5 of the present invention.

[0048] Figure 21 This is a distribution diagram of key physical quantities for the ideal fire nucleus propagation path in Embodiment 5 of the present invention.

[0049] Figure 22 This is a graph showing the propagation speed of C12H26 laminar flame versus the thickness of laminar flame in Embodiment 5 of the present invention.

[0050] Figure 23This is a distribution diagram of flame patterns on the initial fire core front at 0.2ms for different ignition positions in Embodiment 5 of the present invention.

[0051] Figure 24 This is a diagram showing the evolution of the distribution of Da and Ka on the flame front during the ignition process at point A in Embodiment 5 of the present invention.

[0052] Figure 25 This is a diagram showing the evolution of the flame pattern distribution on the flame front during the ignition process at point A in Embodiment 5 of the present invention.

[0053] Figure 26 This is a diagram showing the evolution of the distribution of Da and Ka on the flame front during the ignition process at point B in Embodiment 5 of the present invention.

[0054] Figure 27 This is a diagram showing the evolution of flame pattern distribution on the flame front during the ignition process at point B in Embodiment 5 of the present invention.

[0055] Figure 28 This is a diagram showing the evolution of the distribution of Da and Ka on the flame front during the ignition process at point C in Embodiment 5 of the present invention.

[0056] Figure 29 This is a diagram showing the evolution of flame pattern distribution on the flame front during the ignition process at point C in Embodiment 5 of the present invention.

[0057] Figure 30 This is a visualization of the POD and DMD mode decomposition results of the flame during the stable combustion stage in Embodiment Six of the present invention.

[0058] Figure 31 This is a POD mode energy distribution diagram of the flame during the stable combustion stage in Embodiment Six of the present invention.

[0059] Figure 32 This is a distribution diagram of the DMD characteristic values ​​of the flame in the stable combustion stage of Embodiment 6 of the present invention on the complex plane unit circle. Detailed Implementation

[0060] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0061] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0062] This invention discloses a test apparatus, system, and method for studying flame characteristics of a simulated combustion chamber with flameout capability.

[0063] Example 1 This embodiment provides a test apparatus for a simulated combustion chamber with flameout capability, such as... Figure 1 and Figure 2 As shown, the ignition-quenching simulated combustion chamber test device mainly consists of a combustion chamber, an optical observation window, a swirler assembly, a fuel nozzle, multiple igniter mounting ports, and a support platform. The main body of the device is a combustion chamber with a square cross-section, which defines the combustion zone. A large optical diagnostic window is provided on the inner side wall of the combustion chamber. In this embodiment, this window is preferably a quartz glass window, which has good optical transparency and high temperature resistance. The quartz glass window is fixed and sealed to the wall surface by a cover plate and a high-temperature resistant sealing gasket to ensure airtightness. The outlet pipe section of the combustion chamber is equipped with a back pressure regulating valve to control the operating pressure in the combustion chamber, and pressure and temperature measuring points are arranged in the outlet pipe section. In this embodiment, the fuel flow rate is preferably measured using a Coriolis flow meter with an uncertainty of ±0.1%; the pressure measurement uses a PSI 9116 pressure system device.

[0064] The swirler assembly and fuel nozzle together form the combustion chamber head, a key component for creating a specific fuel-air mixture field. The swirler assembly and fuel nozzle are located at the head of the combustion chamber. This embodiment preferably uses a tower-type swirler. Alternatively, the swirler assembly can be replaced in situ with a tower-type rotating sliding arc exciter to study the rotating sliding arc ignition and combustion characteristics.

[0065] like Figure 3 As shown, after passing through the swirler, air forms a swirling flow field with a specific structure within the combustion zone. This flow field has been verified by PIV measurements and numerical simulations, such as... Figure 4 As shown, several key aerodynamic regions are presented: the inner recirculation zone (IRZ) and main recirculation zone (MRZ) near the central axis for entraining high-temperature combustion gas; and the outer recirculation zone (ORZ) located outside the combustion chamber. The fuel nozzle is positioned on the central axis of the cyclone assembly. In this embodiment, a pressure cyclone atomizing nozzle is used, with a spray cone angle of 80° and a nozzle diameter of 0.25 mm. Furthermore, to systematically study the influence of the initial ignition position on flame development, multiple igniter mounting ports are installed at predetermined and sealed locations on the combustion chamber. Preferably, this embodiment includes at least the following three locations, with the center of the cyclone blade root, i.e., the center of the nozzle outlet surface, as the origin of the coordinate system: Location A: Located at the widest point of the flow field in the outer recirculation zone (ORZ), with coordinates (0, 83, 145).

[0066] Location B: Located at the geometric center of the inner reflux zone (IRZ), with coordinates (0, 0, 145).

[0067] Location C: Located at the head of the inner reflux zone (IRZ), adjacent to the hydrocyclone outlet end face, with coordinates (0, 0, 75).

[0068] Finally, to facilitate experimental operation and optical path alignment, the entire experimental setup was mounted on a support platform. For example... Figure 2 As shown, the platform integrates a hydraulic tilting and protractor structure. The hydraulic cylinder operates at a pressure of 10 MPa, enabling the device to be adjusted and stopped at horizontal, vertical, and any intermediate angle. The angle can be easily read using the protractor.

[0069] Example 2 This embodiment provides a flameout-modified combustion chamber test system, the overall structure of which is shown in the schematic diagram below. Figure 5 As shown. This system is an integrated experimental platform, mainly composed of a gas supply system, a fuel supply system, an ignition-quenching simulated combustion chamber test device, an ignition system, an optical testing system, and a data acquisition and processing unit. In this embodiment, all experimental conditions are preferably set at room temperature (approximately 300K) and atmospheric pressure (101kPa).

[0070] In this embodiment, the ignition-quenching simulated combustion chamber test apparatus mentioned in Embodiment 1 is preferably used. The air supply system provides stable, dry, and precisely flowable air. It includes an air compressor (e.g., rated pressure 0.8 atm, flow rate 2480 L / min), an air tank, a dryer, and a mass flow meter. The air flow rate is precisely measured by a Coriolis mass flow meter with a measurement uncertainty of ±0.1%. The fuel supply system delivers liquid fuel. It includes a pressure-type fuel pump with a maximum fuel supply pressure of 0.8 MPa and a maximum fuel flow rate of 20 g / s, a filter, and a Coriolis mass flow meter with a measurement uncertainty of ±0.1%. The fuel used in this embodiment is Chinese RP-3 aviation kerosene.

[0071] In this embodiment, during the rotating sliding arc point quenching test, the swirler in the combustion chamber is replaced in situ with a rotating sliding arc exciter. Its ignition and combustion-supporting principle is that when the fuel spray passes through the rotating sliding arc, it is ignited under the high temperature of the plasma. On the other hand, the plasma thermal effect promotes further atomization and cracking of the fuel, and the active particles generated during the discharge process are mixed with the atomized fuel under the action of the swirler, thereby enhancing combustion.

[0072] In this embodiment, the ignition system is a high-energy electric spark ignition unit, such as... Figure 6As shown, the system consists of a voltage generator, a surface discharge ignition nozzle (12mm in diameter), and a shielded cable. The instantaneous output voltage of the igniter is 2500VDC, and the discharge frequency is 3.5Hz. The device stores 7J of energy, with an energy utilization efficiency of 30%, therefore the energy released in a single spark is approximately 2.1J. The generated spark is spherical, approximately 15mm in diameter, and located approximately 5mm from the ignition nozzle. The system is connected to the selected igniter mounting port on the test apparatus via the shielded cable.

[0073] In this embodiment, the optical testing system includes a high-speed imaging system, a particle image velocimetry (PIV) system, and a laser particle size analyzer (LPSA).

[0074] The high-speed imaging system is arranged perpendicular to the combustion chamber axis, such as... Figure 7 As shown, it consists of a high-speed camera (e.g., NAC-3M16), an image intensifier, and a Nikon UV lens (F=50mm, f / 1.8) and an OH* filter (center band 308±10nm) mounted on the image intensifier. The camera is equipped with a 12-bit monochrome sensor with a spectral sensitivity range of 350 to 1000nm. The image intensifier's exposure time is set to 1 microsecond, and the frame rate can reach up to 1MHz, used to capture the chemiluminescence signal of the key free radical OH* during combustion.

[0075] Particle image velocimetry (PIV) systems are used to acquire two-dimensional velocity distributions within the combustion chamber, such as... Figure 6 As shown, it includes a dual-path Nd:YAG laser (generating laser pulses with a power of 200 mJ, a wavelength of 532 nm, and a thickness of 1 mm), a CCD camera (12-bit monochrome sensor, resolution 1376 × 1024 pixels) with a 532 ± 10 nm bandpass filter, and a programmable timing unit (PTU) for synchronization control. Di-Ethyl-Hexyl-Sebacat atomized droplets with a diameter of 1–3 µm are seeded into the airflow as tracer particles. The camera performs double-exposure imaging at a frequency of 15 Hz, and the velocity field is calculated through a multi-iteration cross-correction algorithm. Finally, the time-averaged velocity field is obtained by processing 200 pairs of transient images. A laser particle size analyzer is used to measure the Sauter mean diameter (SMD) of the fuel spray droplets and for input / correction model parameters.

[0076] The data acquisition and processing unit (TIU) is the control core of the entire system. It uses a programmable timing unit (PTU) to precisely synchronize and trigger the laser, camera, and ignition signal. Pressure measurement employs a PSI 9116 pressure system with an uncertainty of ±0.05%; air and fuel temperature measurements use Pt100RTD sensors with an uncertainty of ±0.25%. All measuring devices underwent zero-point calibration and verification before the formal experiment. Simultaneously, it is connected to a high-speed imaging system to receive, store, and process the acquired image data, preparing for subsequent flame characteristic analysis.

[0077] Example 3 To interpret and analyze the experimental results, this invention also employs numerical simulation to calculate the cold flow field, component distribution, and flame propagation process within the burner. The simulation conditions, including the inlet temperature and pressure, are identical to the experimental conditions. This numerical simulation method is not only a supplement to the experiment but also an indispensable part of the overall research methodology, providing local transient information (such as local equivalence ratio and turbulence intensity) that is difficult to obtain experimentally. The simulation conditions, including the inlet temperature and pressure, are consistent with the experimental conditions.

[0078] Its computational domain is as follows Figure 8 As shown, calculations were performed using FLUENT software. The turbulence model selected was the DDES-Realizable k-ε model, and the combustion model was the flame thickening combustion model (TFM). C++ was used. 12 H 26 As an alternative fuel to kerosene, the chemical reaction employs a framework chemical reaction mechanism involving 36 substances and 96 reactions. The spray pattern is described using a hollow cone combined with a Rosin-Rammler logarithmic model. Based on experimental results obtained from LPSA, the minimum, average, and maximum droplet diameters are set to 30µm, 45µm, and 50µm, respectively. Boundary conditions are a mass flow inlet and a pressure outlet; the radiation model is the DO model; and the pressure-velocity coupling uses the PISO algorithm.

[0079] like Figure 9 As shown, to ensure computational accuracy, mesh independence verification was performed, and the final element count was determined to be 3.35 million. To reproduce the electric spark ignition process in the simulation, an energy source term was added to the energy equation using a UDF to simulate the formation of the initial flame core. The principle is that in the numerical simulation, it can be assumed that each time the electric spark releases heat, it is a heat source term with a Gaussian distribution in time and space. The expression for the constructed spark energy source term is:

[0080] in It is the energy released by a single electric spark, σ t The duration of the electric spark is set to 0.16 ms in this paper, σr This is the initial fire core radius, which is set to 5mm in this paper. (x) 0， y 0， z0) is the ignition position coordinate, t is the current flow time, and t0 is the ignition start time.

[0081] To analyze the impact of turbulence on the flame while balancing computational costs for control, and to capture the interaction between the flame front and vortex, an adaptive mesh re-division (AMR) algorithm was employed. This algorithm uses OH* mass fraction and equivalent vorticity to identify the flame front and vortex, and then refines the mesh for this region using these criteria. After multiple refinements, the minimum mesh size reached 0.08 mm, sufficient to analyze the key structures of the flame front.

[0082] Finally, rigorous verification was conducted to ensure the reliability of the numerical simulation. (The following is a continuation of the previous sentence:) Figure 10 As shown, the axial and radial velocity distributions measured by the PIV experiment under cold flow field are compared with the numerical simulation results at three different cross sections (L1, L2, L3). The results show that the two are in good agreement, thus confirming that the numerical simulation method can accurately predict the complex swirling flow field in the combustion chamber, laying a solid foundation for subsequent flame model analysis based on the simulation results.

[0083] Example 4 This embodiment provides a method for studying flame characteristics using the above-mentioned system, which focuses on the macroscopic division and analysis of the flame development process.

[0084] First, an ignition port is selected. In this embodiment, the preferred ignition ports are those located at positions A, B, and C as set in Embodiment 1. After setting the operating conditions (e.g., air flow rate 1400 L / min, equivalence ratio 0.55), the ignition system is started to generate an initial fire nucleus. Simultaneously, the high-speed imaging system begins acquiring OH* chemiluminescence image sequences. After the experiment, the image sequences are processed according to the following procedure: Figure 11 As shown, the process includes background subtraction, bilateral filtering, image sharpening, Gaussian filtering, Otsu thresholding binarization, erosion, and Canny edge detection. Finally, the normalized projected area of ​​the flame in each frame is calculated, and its change over time is plotted. Figure 12 As shown in (b), based on the morphological characteristics of the curve, the flame development process is divided into six states: S1: initial flame core, S2: flame core decay, S3: flame propagation, S4: flame dwell, S5: flame growth, and S6: stable combustion. S1: Initial Flame Core: The igniter discharge generates a high-temperature spark, which ignites the fuel and forms the initial flame core; S2: Flame core decay: The flame of the initial flame core decreases under the influence of the flow field; S3: Flame propagation: The flame migrates under the influence of the flow field and ignites the surrounding fuel, increasing the flame area; S4: Flame Dwell: The flame area is maintained at a low level; S5: Flame Growth: After the dwell phase, the flame intensity suddenly increases and grows rapidly; S6: Stable Combustion: The flame core enters stable combustion, and the flame intensity begins to change periodically.

[0085] By comparing the state sequences corresponding to different ignition positions, their impact on flame propagation path, ignition success rate, and ignition delay time can be quantitatively assessed, such as... Figure 12 As shown. For example, ignition at point A, as... Figure 13 and Figure 14 As shown, the flame development sequence is S1→S3→S4→S5→S6, characterized by a distinct flame dwell stage. Ignition at point B, as... Figure 15 and Figure 16 As shown, the sequence is S1→S3→S5→S6, lacking a residence phase, indicating a closer connection between the propagation and growth processes. Ignition at point C, as... Figure 17 and Figure 18 As shown, the sequences are S1→S2 and S3→S5→S6. The initial stage is accompanied by significant ignition core decay, making successful ignition more challenging.

[0086] Example 5 This embodiment aims to further analyze the propagation process of the flame core during ignition, revealing the intrinsic mechanism leading to the success or failure of flame propagation from a physical perspective. This paper employs a method based on Karlovitz (… )and ( ) Dimensionless numbers are used to evaluate flame patterns, where Defined as the local stretching ratio of the flow field ( ) and flameout elongation ( The ratio of ). The smaller the value, the less the flow field stretches the flame, and the higher the flame stability. For turbulent time scale ( ) and chemical timescale ( The ratio of ). The smaller the number, the greater the chemical reaction rate is on a timescale greater than that of the fluid, meaning the reaction dominates the flame state, the flame front propagation is determined by the reaction rate, and the flame stability is high. The two dimensionless numbers are calculated using the following formula:

[0087]

[0088] In the formula The length of the large eddy integral. For turbulent pulsation, For the thickness of the flame, This represents the propagation speed of a laminar flame. Calculate using the following method:

[0089] Fitting based on experimental data:

[0090] and It is obtained through the following equation:

[0091]

[0092] In the formula For local equivalent ratio, For turbulent kinetic energy, For turbulent dissipation rate, Instantaneous velocity This is the time-averaged speed. , , Calculate using the following method:

[0093]

[0094]

[0095] in For dynamic viscosity, The viscosity coefficient of the subgrid eddy is... For the velocity gradient tensor, , , , respectively representing C in the gas phase 12 H 26 Mass fractions of O2 and N2.

[0096] In order to obtain and Using the skeletal mechanism, C was calculated via Chemkin at T=400K, 1 atm. 12 H 26 of and The result is as follows Figure 22 As shown. Among them Calculate using the following formula:

[0097] in The final temperature of the flame. The initial temperature of the mixture. For temperature gradient.

[0098] Through C 12 H 26 At T=400K, 1atm and Nonlinear fitting was performed to obtain its variation with equivalence ratio. The nonlinear semi-empirical formula for change:

[0099]

[0100] Project the calculated Da and Ka values ​​onto, as shown in the figure Figure 20 The Borghi diagram shown indicates that the turbulent flame patterns in the local area of ​​the flame front include: FM1: laminar flame, FM2: pleated flame, FM3: thickened flame with pockets, FM4: thickened pleated flame, FM5: thickened flame that may be extinguished, and FM6: thick flame.

[0101] The combustion stability of these turbulent flame modes, ranked from highest to lowest, and their respective characteristics are as follows: FM1: Laminar Flow Flame , The flame front is smooth and continuous, and the combustion rate is dominated by molecular diffusion and chemical reaction, exhibiting strong convective heat transfer characteristics.

[0102] FM2: Wrinkled Flame: Turbulent vortices distort the flame surface, creating wrinkles that increase the surface area of ​​the flame front, thereby improving mixing efficiency and combustion rate, and accelerating flame propagation. The heat from the flame front can spread and ignite the surrounding unburned gas mixture.

[0103] FM3: Thickened flame with pouches: , Turbulent shear forces split the flame into isolated combustion zones with unburned mixture at the edges. Turbulence accelerates mixing, but the distribution of these pockets is random. The unburned mixture is easily entrained and isolated by turbulence, causing localized interruptions in the reaction and leading to a chain reaction of flameout.

[0104] FM4: Thickened Wrinkled Flame: , The flame thickens significantly, the folds on the flame front are blurred by small-scale turbulence, and the flame edge shows obvious curling and expansion, exhibiting strong turbulence characteristics. The flame propagation speed decreases, and the flame stability decreases.

[0105] FM5: Potentially Extinguished Thick Flames: Continue to increase, when At this time, the flow field stretches the flame, forming highly fragmented flame pieces, resulting in localized extinguishing gaps. The combustion zone inside the flame is unstable and easily extinguished under external disturbances.

[0106] FM6: Thick Flame Turbulence completely suppresses the flame structure, resulting in complete flame dispersion and the disappearance of the boundary between the reaction zone and the turbulent mixing zone. The flame surface is non-uniform and difficult to maintain stability. Any disturbance in the airflow or temperature fluctuation may cause the flame to extinguish.

[0107] By analyzing the ideal propagation path of the flame, such as... Figure 19 As shown, and the distribution of flame patterns on the flame front at different times, as shown in the figure. Figure 23 , Figure 24 , Figure 25 , Figure 26 , Figure 27 , Figure 28 and Figure 29 As shown, the key factors for successful ignition can be revealed. For example, the analysis shows that the initial flame core stability at point C is the highest (mainly FM3 / FM5), but the Ka number increases sharply along its propagation path, making it easily stretched and quenched by the flow field; while the initial flame core stability at point A is the worst (mainly FM5 / FM6), but its propagation path is conducive to the flame entering the main recirculation zone and stabilizing (transforming into the more stable FM4 mode).

[0108] Example 6 After the flame develops to the stable combustion stage S6, in order to quantitatively describe the effect of sliding arc plasma discharge on the swirling flame and to study the influence of ignition position on the final stable flame structure and stability, POD and DMD analyses were performed on the OH* measurement results.

[0109] Applying the POD method to the image sequence of stage S6, the complex flame field is decomposed into a set of orthogonal spatial modes ordered by energy (e.g., Figure 30 As shown). The highest energy mode represents the largest-scale coherent structure in the flame. By analyzing the energy proportion of each mode (e.g. Figure 31 As shown in the figure, the macroscopic dynamic structure of a flame can be quantitatively understood.

[0110] For example, under the no-slip arc condition, a pair of counter-rotating vortex structures can be observed in POD mode 1, which are approximately symmetrically distributed near the flame zone. This indicates that the strong reaction region alternates radially up and down, exhibiting a radial oscillation form of self-excited vortex flow, which is the main pulsating form of the externally excited motion of the vortex flame. The strong reaction region of POD mode 2 alternates left and right, and the combustion reaction in the combustion chamber belongs to the axial oscillation mode, which is related to the vortex shedding and propagation of the vortex flame in the axial direction. The strong reaction regions of POD modes 3, 4, and 5 alternate in the upper, middle, and lower axial positions, reflecting higher-order axial motion modes, which is mainly influenced by the precession of the vortex core. Under the rotating slip arc combustion condition, the strong reaction regions of POD modes 1 and 2 oscillate radially in the upper and lower positions of SJZ. The strong reaction region of POD mode 2 alternates left and right, which is the result of the coupling effect of vortex shedding and the thermal effect of the slip arc. POD modes 4 and 5 reflect the increased energy of higher-order axial motion due to the influence of the slip arc, the increased turbulence, and the increased number of small-scale vortex structures.

[0111] POD analysis yields the POD coefficient (sometimes also called the time coefficient), which can quantitatively characterize the energy distribution in a flame. Figure 31 The paper presents the energy distribution of different modes of an undisturbed flame under conditions of no slip arc and with slip arc. Figure 31 It can be seen that, due to the effect of sliding arc discharge, the average energy proportion of the flame increases from 75.7% to 81.8%. Correspondingly, the proportion of coherent structural energy (POD coefficients of modes 1-5) changes from 18.0% to 8.2%. The energy proportion of transition state and turbulent dynamics (modes 6 and above) increases from 6.3% to 10%. Thus, under the action of sliding arc discharge, about 10% of the coherent modes are converted into average mode energy and transition state and turbulent dynamic energy, which reduces the axial oscillation energy of the flame, enhances turbulence, and makes the combustion reaction more intense.

[0112] The DMD method is applied to image sequences in the S6 phase to identify dynamic modes with a single oscillation frequency and growth / decay rate in the data. The analysis results in a series of eigenvalues, when plotted on the unit circle of the complex plane (e.g., ...). Figure 32 As shown in the diagram, the position of the eigenvalue directly reflects the stability of the mode: an eigenvalue inside the unit circle indicates a stable decaying mode, an eigenvalue on the unit circle indicates a neutral periodic mode, and an eigenvalue outside the unit circle indicates an unstable growing mode. DMD analysis can accurately identify whether there are unstable oscillation frequencies in the combustion process, thereby assessing combustion stability.

[0113] Example 7 This embodiment is applied to the test of lean ignition limit. Under constant air flow conditions, the fuel flow rate is gradually reduced, and repeated ignition is performed at each operating point (recommended ≥10 times / point, preferably ≥30 times / point) until ignition fails multiple times consecutively. The corresponding equivalence ratio at this point is the lean ignition limit at that ignition location. By analyzing the complete flame state sequence of the last successful ignition and the first failed ignition near the limit operating condition, based on the S1~S6 sequence and the Da / Ka field, the modes of ignition failure and lean quenching (such as the flame core being quenched by high tension at the IRZ head, failure to effectively ignite SJZ fuel, etc.) can be identified. In addition, the structure and energy distribution of the stable combustion stage can be analyzed by combining POD / DMD, so that the specific failure mode leading to lean quenching can be clearly determined.

[0114] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A test apparatus for a simulated combustion chamber with flameout capability, characterized in that: Includes a combustion chamber, the interior of which defines a combustion zone, and the inner sidewall of the combustion chamber is provided with an optical diagnostic window; A swirler assembly is disposed at the head of the combustion chamber to form an incoming air flow field with a specific swirling structure, the flow field structure including an inner recirculation zone, a main recirculation zone and an outer recirculation zone; A fuel nozzle, located at the center of the cyclone assembly, is used to inject fuel into the combustion zone; Multiple igniter mounting ports are respectively disposed at predetermined positions corresponding to the swirling flow field structure, for selectively generating an ignition core at one or more of at least three locations: Location A is located at the widest point of the external reflux zone; Position B is located at the geometric center of the inner recirculation zone; Position C is located at the head of the inner recirculation zone, near the outlet end face of the hydrocyclone assembly.

2. The ignition-quenching model combustion chamber test device according to claim 1, characterized in that: The cyclone assembly is a tower cyclone or a tower rotating sliding arc exciter.

3. The ignition-quenching model combustion chamber test device according to claim 1, characterized in that: The optical diagnostic window is a quartz glass window, and is fixedly sealed to the combustion chamber by a cover plate and a sealing gasket.

4. The ignition-quenching model combustion chamber test device according to claim 1, characterized in that: The combustion chamber outlet pipe section is equipped with a back pressure regulating valve, and pressure and temperature measuring points are arranged in the outlet pipe section.

5. The ignition-quenching model combustion chamber test device according to claim 1, characterized in that: The test device is mounted on a support platform with a hydraulic tilting and protractor structure, and the support platform can be stopped horizontally, vertically, and at any angle.

6. The ignition-quenching model combustion chamber test apparatus according to claim 1, characterized in that: The fuel nozzle is a pressure swirl atomizing nozzle.

7. A simulated combustion chamber test system for ignition and extinction, characterized in that: Includes the ignition-quenching model combustion chamber test apparatus as described in any one of claims 1 to 6; An air supply system, wherein the air supply system is connected to the air inlet and fuel nozzle of the test apparatus; A fuel supply system, which is connected to the air inlet and fuel nozzle of the test apparatus; The ignition system is used to generate the ignition core; The ignition system is connected to one or more igniter mounting ports of the test apparatus; or the ignition system is electrically connected to the tower-type rotating sliding arc exciter in the cyclone assembly. A high-speed imaging system is arranged outside the optical diagnostic window of the test device to acquire continuous time-series images of the combustion area from the generation of the ignition core to the stabilization or extinction of the flame. A data acquisition and processing unit, which is connected to the high-speed imaging system, is used to receive and process the continuous time series images.

8. The ignition-quenching simulated combustion chamber test system according to claim 7, characterized in that: The high-speed imaging system includes a high-speed camera, an image intensifier, and an OH* filter mounted on the image intensifier, wherein the center wavelength of the OH* filter is approximately 308±10nm.

9. The ignition-quenching simulated combustion chamber test system according to claim 7, characterized in that: The system also includes a particle image velocimetry (PIV) system and a laser particle size analyzer (LPSA) for acquiring the cold velocity field and the Sotel mean particle size (SMD) of the spray droplets, respectively.

10. The ignition-quenching simulated combustion chamber test system according to claim 7, characterized in that: The data acquisition and processing unit is used to synchronously control and trigger the laser, camera, and ignition signals.

11. The ignition-quenching simulated combustion chamber test system according to claim 7, characterized in that: The ignition system is a high-energy electric spark igniter or a tower-type rotary sliding arc exciter.

12. A method for studying flame characteristics using a flameout-modified combustion chamber test system according to any one of claims 7 to 11, characterized in that: include: A1. According to the research needs, select the ignition method and position, select an igniter installation port position A, position B or position C on the test device, and start the ignition system to generate an initial flame core in the combustion area; or enable the rotating sliding arc exciter to ignite at the head; A2. Using the high-speed imaging system, acquire continuous time-series OH* chemiluminescence images from the moment the initial ignition nucleus is generated until the flame develops into stable combustion or extinguishing; A3. Process the continuous time series images, extract the flame normalized projection area of ​​each frame image, and plot the flame normalized projection area change curve over time. A4. Based on the characteristics of the flame normalized projected area change curve over time, the flame development process is divided into one or more of the following six states: S1: initial flame core, S2: flame core decay, S3: flame propagation, S4: flame dwell, S5: flame growth, S6: stable combustion. A5. Based on the flame development state sequence corresponding to different ignition positions, determine the impact of ignition position on flame propagation path, ignition success rate and ignition delay time.

13. The method for studying flame characteristics according to claim 12, characterized in that: It also includes step A6, which combines the pre-obtained cold velocity field and component field data to calculate the Damköhler number Da and Karlovic number Ka on the flame front during the flame propagation process, and determines the turbulent flame mode of the flame front based on Da and Ka, thereby analyzing the physical mechanism that leads to the fire core decay S2 or the flame propagation S3.

14. The method for studying flame characteristics according to claim 13, characterized in that: The turbulent flame mode includes one or more of the following: laminar flame mode, pleated flame mode, thickened flame mode with pockets, thickened pleated flame mode, potentially extinguishable thickened flame mode, and thick flame mode.

15. The method for studying flame characteristics according to claim 12, characterized in that: It also includes step A7: after the flame enters a stable combustion state S6, the intrinsic orthogonal decomposition (POD) method is applied to the acquired continuous time series images to extract the main spatial modes of the flame and their energy distribution in order to identify the large-scale coherent structure of the flame.

16. The method for studying flame characteristics according to claim 12, characterized in that: It also includes step A8: after the flame enters a stable combustion state S6, the dynamic mode decomposition (DMD) method is applied to the acquired continuous time series images to extract the dynamic modes, oscillation frequency and growth rate of the flame in order to evaluate the combustion stability of the flame.

17. The method for studying flame characteristics according to any one of claims 12 to 16, characterized in that: Under constant airflow conditions, by gradually reducing the fuel flow and repeating steps A1 to A5 until ignition fails, the lean ignition limit LLO corresponding to different ignition positions is determined. Furthermore, by analyzing the flame state sequence during the ignition failure process, the failure mode leading to lean combustion and flameout was diagnosed.

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