Three-dimensional diagnosis method for combustion behavior of water-based monopropellant fuel droplets

Abstract

The invention provides a water-based single-component fuel droplet combustion behavior three-dimensional diagnosis method, and relates to the technical field of combustion diagnosis, and the method comprises the following steps: dropwise adding a water-based single-component fuel to a metal plate controlled by an electric heating furnace in a single droplet form through an injector; in the process that the liquid drops make contact with the metal plate and are heated and combusted, temperature data, combustion images and infrared spectrum signals of combustion products are synchronously collected in real time, and the collection frequency is larger than or equal to 500 Hz; the ignition response time, the combustion time and the minimum ignition temperature are calculated through the temperature data and the combustion image, and the types of combustion products are identified through infrared spectrum signals; the stability of fuel droplet combustion and the difficulty degree of self-sustaining combustion are judged by monitoring the temperature change of the center position of the metal plate. According to the method, the image, the temperature and the gas phase product of the fuel process of the water-based single-component fuel single liquid drop can be analyzed in real time, and the ignition response time and the liquid drop combustion period of different formulas of the water-based single-component fuel can be calculated.

Description

Technical Field

[0001] This invention relates to the field of combustion diagnostics, and more particularly to a three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets. Specifically, it involves simultaneous sampling of multiple parameters of droplet combustion through microsecond-level time-resolved temperature measurement, image acquisition, and infrared spectral analysis, and calculation of the ignition response time, combustion time, and minimum ignition temperature of the fuel droplets, thereby screening water-based monocomponent fuel formulations. Background Technology

[0002] The three-dimensional diagnostic method for fuel droplet combustion behavior is a method that simultaneously acquires images, temperatures, and infrared spectral signals of combustion products during the droplet combustion process, calculates the combustion ignition response time, combustion time, and minimum ignition temperature, and uses this method to screen water-based monocomponent fuel formulations.

[0003] Since the droplet combustion process lasts only a few seconds, the time resolution of image, temperature, and infrared spectrum acquisition must be at the millisecond level. By using droplet combustion behavior diagnostic methods to comprehensively analyze the combustion images, temperature, and infrared spectral data of water-based monocomponent fuel droplets of various formulations, the minimum ignition temperature of the corresponding fuel formulation, as well as the ignition response time (i.e., the time from droplet contact with the hot metal plate to the droplet generating a flame), combustion time (the time from the appearance of the flame to the flame extinguishing), and types of combustion products at different temperatures can be obtained.

[0004] Water-based monocomponent fuel is a novel high-energy monocomponent fuel containing energetic ionic liquids. It features high energy density, rapid and stable decomposition, no solid residue after combustion, clean fuel, low fuel characteristic signal, and low toxicity. Water-based monocomponent fuel mainly consists of an oxidant, a propellant, and water as a solvent, and can sustain combustion in oxygen-free environments such as space or underwater. Common oxidant components include hydroxylamine nitrate (HAN), ammonium dinitrate (ADN), and hydrogen peroxide (H2O2); common propellants include triethanolamine nitrate (TEAN), N,N-diethylhydroxylamine nitrate (DEHAN), hydrazine nitrate (HN), ethylhydrazine nitrate (EHN), hydroxyethylhydrazine nitrate (HEHN), ammonium nitrate (AN), ammonia (AH), and methanol (MeOH). Typical water-based monocomponent fuels include AF-M315E (main components are 44.5% HAN, 44.5% HEHN, and 11% water), SHP-163 (main components are 73.6% HAN, 16.3% methanol, 3.9% AN, and 6.2% water), and ADN-LMP103S (main components are 63% ADN, 18.4% methanol, and 18.6% ammonia solution).

[0005] In contrast, the most typical oil-based monocomponent fuel is OTTO-II type fuel, whose main components are 76% propylene glycol dinitrate (PGDN, as an energy agent), 22.5% dibutyl sebacate (DBS, as a diluent), and 1.5% 2-nitroaniline (2-NPA, as a stabilizer). The single-droplet combustion of oil-based monocomponent fuels is similar to that of ordinary oil-based fuels (gasoline, diesel), primarily involving gas-phase combustion. During combustion, the droplet surface first vaporizes to generate gas, which then burns on the droplet surface. As combustion progresses, the droplet gradually shrinks. Therefore, oil-based monocomponent fuels are generally easy to ignite and have relatively stable combustion.

[0006] In contrast, water-based monocomponent fuels, due to their water solvent, generate a large amount of water vapor on the droplet surface upon heating. Since water vapor is non-combustible and water has a high latent heat of vaporization, a single droplet needs to absorb a significant amount of heat before combustion. As the water-based monocomponent fuel droplet evaporates and concentrates, the entire droplet absorbs heat and heats up. When the temperature reaches the decomposition temperature, the entire droplet decomposes and burns within a very short time, releasing a large amount of heat. Therefore, the droplet combustion mechanism of water-based monocomponent fuels differs fundamentally from that of oil-based monocomponent fuels. Because water vaporization involves a large amount of heat absorption and release rapidly, water-based monocomponent fuels are more difficult to ignite and sustain stable combustion. Therefore, studying the evaporation-concentration-decomposition-combustion process of water-based monocomponent fuel droplets is of great significance for their engineering applications.

[0007] However, there are currently few reports on methods for diagnosing the combustion behavior of droplet fuels. Ao Wen et al. from Northwestern Polytechnical University reported a high-temperature, high-pressure, multi-atmosphere single-droplet combustion experimental device (CN113391022A). This device mainly provides the atmosphere and high pressure, igniting single droplets through an automatic droplet generation device and a U-shaped ignition plate, but lacks real-time acquisition equipment for temperature, images, and infrared spectra. Huang Ronghua et al. from Huazhong University of Science and Technology reported a three-dimensional reconstruction method and experimental device for flame temperature in single-droplet combustion (CN110608889B). This device uses spark plug ignition, a fiber optic imaging bundle, an optical lens system, and a high-speed camera to mainly acquire images and temperature information; it uses spark ignition, a blackbody furnace to calibrate the temperature, and an algorithm to reconstruct the three-dimensional flame temperature field.

[0008] In the existing technology, the single-droplet combustion diagnostic method has the following technical defects: Although the existing device can realize droplet ignition under high pressure and multi-atmosphere environment, it lacks the real-time acquisition function of temperature, image and infrared spectrum, and cannot obtain multi-dimensional dynamic data of the combustion process; although the three-dimensional reconstruction of the flame temperature field and image acquisition are realized through the optical system, the infrared spectral analysis module is not integrated, so it is impossible to determine the species information of combustion products. Moreover, neither method is designed for the characteristic of water-based monocomponent fuels that do not require an external oxygen source, and it is impossible to calculate its minimum ignition temperature, ignition response time, combustion time and other key parameters, which makes it difficult to support the accurate screening and optimization of fuel formulation. Summary of the Invention

[0009] To address the technical problem that existing single-droplet combustion diagnostic methods cannot calculate key parameters such as minimum ignition temperature, ignition response time, and combustion time, this invention provides a three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets. This invention can perform real-time analysis of images, temperatures, and gaseous products of the fuel process of single water-based monocomponent fuel droplets. By analyzing images from a high-speed camera, the ignition response time and droplet combustion cycle of different water-based monocomponent fuel formulations can be calculated, thereby optimizing the ignition responsiveness of various formulations.

[0010] The technical means employed in this invention are as follows: A three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets includes the following steps: Water-based monocomponent fuel is added in single droplet form to a metal plate controlled by an electric heating furnace using a syringe. During the process of droplets contacting the metal plate and being heated and burned, temperature data, combustion images and infrared spectral signals of combustion products are collected in real time simultaneously at a frequency of ≥500Hz. Ignition response time, combustion time and minimum ignition temperature are calculated using temperature data and combustion images, and the types of combustion products are identified using infrared spectral signals. By monitoring the temperature change at the center of the metal plate, the stability of fuel droplet combustion and the ease of self-sustaining combustion can be determined.

[0011] Furthermore, the dripping angle of the syringe is less than 15 degrees from the vertical direction, and the dripping height is 1cm-10cm from the syringe needle tip to the metal plate, to ensure that the droplet size and dripping speed are consistent.

[0012] Furthermore, the ignition response time is the time from the droplet contacting the metal plate to the appearance of a flame, calculated using high-speed camera images, specifically as follows: The first frame of the image where the droplet contacts the metal plate is taken as the starting point, and the first frame of the image where the flame appears is taken as the ending point; Calculate the number of images n1 between two frames, the acquisition frequency of the high-speed camera n0Hz, and obtain the ignition response time t1=n1 / n0, in seconds.

[0013] Furthermore, the combustion time, defined as the time from the appearance of the flame to its disappearance, is calculated using high-speed camera images. Specifically: The first frame of the image where the flame appears is taken as the starting point, and the first frame of the image where the flame disappears is taken as the ending point; Calculate the number of images n2 between two frames, the acquisition frequency of the high-speed camera n0Hz, and obtain the burning time t2=n2 / n0, in seconds.

[0014] Furthermore, the minimum ignition temperature is the lowest temperature at which the metal plate can ignite the droplets, and is determined by gradually lowering the temperature of the metal plate until the droplets can no longer be ignited.

[0015] Furthermore, the types of combustion products are identified by characteristic peaks in infrared spectroscopy, including one or more of H2O, CO2, CO, NO, N2O, NO2, CH4, and NH3.

[0016] Furthermore, by measuring the temperature change at the center of the metal plate during combustion using thermocouple signals, the heat absorption and release during the droplet combustion process can be analyzed to determine the stability of fuel droplet combustion and the ease with which it can maintain stable combustion.

[0017] Furthermore, the water-based monocomponent fuel is composed of an oxidant, a combustion agent, and a solvent water, wherein: The oxidizing agent is one or more of hydroxylamine nitrate, dinitramide ammonium, and hydrogen peroxide; The propellant is one or more of the following: triethanolamine nitrate, N,N-diethylhydroxylamine nitrate, hydrazine nitrate, ethylhydrazine nitrate, hydroxyethylhydrazine nitrate, ammonium nitrate, hydrazine, and methanol.

[0018] Compared with the prior art, the present invention has the following advantages: This invention addresses the droplet combustion characteristics of water-based monocomponent fuels and designs a method for diagnosing the droplet combustion behavior of these fuels. Besides acquiring temperature and image information with millisecond-level time resolution, it also utilizes infrared spectroscopy to measure combustion product species. Furthermore, taking advantage of the characteristics of water-based monocomponent fuels (which do not require an external oxygen source), this method can calculate the minimum ignition temperature, ignition response time at different temperatures, combustion time, and combustion product types for different formulations of water-based monocomponent fuels, enabling the screening and optimization of water-based monocomponent fuel formulations.

[0019] This method enables real-time analysis of images, temperatures, and gaseous products of the fueling process of a single droplet of water-based monocomponent fuel. By analyzing images from a high-speed camera, the ignition response time and droplet combustion cycle of different water-based monocomponent fuel formulations can be calculated, allowing for optimization of the ignition response of various formulations. Analysis of temperature curves can determine the self-sustaining combustion behavior of different formulations, thereby selecting water-based monocomponent fuel formulation components that are prone to self-sustaining combustion. Analysis of combustion products can determine whether the oxygen-fuel ratio in the water-based monocomponent fuel formulation is appropriate, allowing for further optimization of the oxygen-fuel ratio.

[0020] In summary, the method of the present invention can optimize the design of water-based monocomponent fuel formulations from multiple aspects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of a three-dimensional diagnostic device for the combustion behavior of water-based monocomponent fuel droplets.

[0023] Figure 2 Images of the ignition and combustion cycle of water-based monocomponent fuel droplets are obtained at a frequency of 2000 Hz.

[0024] Figure 3 Images of the ignition and combustion cycle of oil-based monocomponent fuel droplets are shown, with an image acquisition frequency of 2000 Hz.

[0025] Figure 4 This is a temperature curve of the combustion process of water-based monocomponent fuel droplets.

[0026] Figure 5 This is a temperature curve of the combustion process of oil-based monocomponent fuel droplets.

[0027] Figure 6 shows the infrared spectra of the combustion products of water-based monocomponent fuel droplets. Figure 6(a) shows the background signal, Figure 6(b) shows the infrared spectrum of a typical water-based monocomponent fuel, and Figure 6(c) shows the infrared spectrum of another water-based monocomponent fuel formulation.

[0028] Figure 7 The infrared spectrum of the combustion products of oil-based monocomponent fuel droplets is shown.

[0029] In the diagram: 1. Infrared spectrometer; 2. Fixed bracket; 3. Lifting platform; 4. Electric heating furnace; 5. Metal plate; 6. Thermocouple; 7. Spotlight; 8. Syringe; 9. Temperature acquisition module; 10. High-speed camera; 11. Computer. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0035] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0036] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0037] like Figure 1 As shown, this invention provides a three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets, comprising the following steps: Water-based monocomponent fuel is added in single droplet form to a metal plate controlled by an electric heating furnace using a syringe. During the process of droplets contacting the metal plate and being heated and burned, temperature data, combustion images and infrared spectral signals of combustion products are collected in real time simultaneously at a frequency of ≥500Hz. Ignition response time, combustion time and minimum ignition temperature are calculated using temperature data and combustion images, and the types of combustion products are identified using infrared spectral signals. By monitoring the temperature change at the center of the metal plate, the stability of fuel droplet combustion and the ease of self-sustaining combustion can be determined.

[0038] Control the drop height and angle of the syringe to ensure that the droplet size and speed are consistent each time.

[0039] Water-based monocomponent fuel droplets are ignited by a metal plate on an electric heating furnace. The temperature throughout the process is recorded by thermocouple signals, the combustion is recorded by a high-speed camera, and the combustion products are collected in real time by an infrared spectrometer.

[0040] The ignition response time is the time between the moment the water-based monocomponent fuel droplet contacts the high-temperature metal plate and the moment the flame appears. The ignition response time t1 is calculated using images from a high-speed camera. It starts from the frame image where the droplet just contacts the metal plate and ends from the frame image where the flame just appears. The number of images n1 taken during this period is divided by the sampling frequency n0Hz of the high-speed camera, i.e., t1=n1 / n0, in seconds.

[0041] The combustion time is the time from the moment the water-based monocomponent fuel droplet appears to the moment the flame disappears. The combustion time t2 is calculated using images from a high-speed camera, starting from the frame where the flame just appears and ending with the frame where the flame just disappears. The number of images n2 taken during this period is divided by the sampling frequency n0Hz of the high-speed camera, i.e., t1=n2 / n0, in seconds.

[0042] The minimum ignition temperature is the lowest temperature at which the droplets of water-based monocomponent fuel can be ignited and no flame will appear because the temperature of the metal plate is too low. This temperature is the lowest ignition temperature of the water-based monocomponent fuel formulation.

[0043] Combustion product types can be identified by the characteristic peaks of infrared spectra acquired in real time, allowing for the identification of gaseous products with infrared characteristic peaks in the combustion products of water-based monocomponent fuels.

[0044] Water-based monocomponent fuels are mainly composed of oxidant, propellant and solvent water.

[0045] The angle between the syringe tip and the vertical direction should be controlled to be less than 15 degrees. An excessively large angle will cause random fluctuations in droplet size, which is positively correlated with ignition response time. The droplet height should be within the range of 1cm-10cm between the syringe needle tip and the high-temperature metal plate. Too small a distance will cause the droplet to be prematurely heated by the metal plate, affecting measurement accuracy; too large a distance will result in excessively fast droplet falling, causing the droplet to break upon impact with the metal plate, forming numerous small droplets and affecting the measurement of ignition response time.

[0046] Thermocouple signals can be used to measure the temperature change at the center of the metal plate during combustion. This can reflect the heat absorption and release during the combustion of the droplets, and determine the stability of the fuel droplet combustion and the ease with which it can sustain stable combustion.

[0047] The gaseous products with infrared characteristic peaks are one or more of H2O, CO2, CO, NO, N2O, NO2, CH4, and NH3.

[0048] The oxidizer of the water-based monocomponent fuel is one or more of hydroxylamine nitrate, ammonium dinitrate, and hydrogen peroxide. The propellant of the water-based monocomponent fuel is one or more of triethanolamine nitrate, N,N-diethylhydroxylamine nitrate, hydrazine nitrate, ethylhydrazine nitrate, hydroxyethylhydrazine nitrate, ammonium nitrate, hydrazine, and methanol.

[0049] Water-based monocomponent fuel is added drop by drop using a syringe, and the temperature of the metal plate is controlled by an electric heating furnace. During the process of the water-based monocomponent fuel droplets contacting the metal plate and being heated and burned, the temperature, combustion images and infrared spectra of the combustion reaction products are collected and recorded in real time at a frequency of ≥500Hz. Figure 1 A schematic diagram of a three-dimensional diagnostic device demonstrating the combustion behavior of water-based monocomponent fuel droplets is shown.

[0050] The device consists of three parts: a water-based monocomponent fuel dripping system, a heating and temperature control system, and a data acquisition system. The infrared spectrometer 1 can complete the infrared spectrum acquisition of combustion gas products on a microsecond timescale. The fixed bracket 2 is used to fix the spotlight 7, syringe 8, metal plate 5, and high-speed camera 10, among other equipment. The lifting platform 3 is used to remove the electric heating furnace 4 when the temperature of the metal plate 5 reaches a preset value, preventing the high-temperature heating wire from affecting the metal plate 5. The electric heating furnace 4 is used to control the heating of the metal plate 5 to a specified temperature. The metal plate 5 is used to heat and ignite the fuel droplets. Thermocouple 6 is fixed in the center of the metal plate 5 to collect temperature information during the combustion process of the fuel droplets. The spotlight 7 is used to provide supplementary lighting for the high-speed camera 10. The syringe 8 is used to control the single-droplet application of fuel to the metal plate 5. The temperature recording module 9 is used to store and record the temperature information of the thermocouple 6. The high-speed camera 10 is used to capture images of the fuel droplet combustion. The computer 11 is used to control the infrared spectrometer 1, the high-speed camera 10, and the temperature recording module 9.

[0051] The data acquisition system can simultaneously acquire three signals: temperature, image, and infrared spectrum. The thermocouple 6 is a K-type armored thermocouple 6, the combustion image is captured by a high-speed camera 10, and the infrared spectrum is captured by a time-resolved infrared spectrometer 1. The sampling frequencies of temperature, combustion image, and infrared spectrum are all ≥500Hz. When the high-speed camera 10 is set to a frequency of 500Hz during shooting, the image size is ≥640×480. The sampling resolution of the infrared spectrometer 1 is ≥1cm-1.

[0052] The fuel dripping system consists of a fixed bracket 2, a clamp, and a syringe 8, which can adjust the dripping position, angle, and height; the angle between the syringe 8 and the vertical direction is <15°; the distance between the syringe tip and the metal plate 5 is 1cm~10cm.

[0053] The temperature control system consists of an electric heating furnace 4, a metal plate 5, and a temperature measuring thermocouple 6. The temperature control accuracy is not less than ±0.5℃. The thermocouple 6 is a K-type armored thermocouple with a diameter of less than or equal to 0.5mm. Its measuring end is formed into a spherical structure by laser welding and fixed to the center of the metal plate 5. It is configured to collect temperature data at a frequency of ≥500Hz and transmit it to the storage computer 11 through direct memory access (DMA).

[0054] Example 1: First, the metal plate 5 is heated to the required temperature using an electric heating furnace 4. Then, the lifting platform 3 is operated to lower the electric heating furnace, moving it away from the metal plate 5 to avoid the influence of the high-temperature heating element on ignition. Next, water-based monocomponent fuel is added dropwise to the surface of the metal plate 5 using a syringe 8, while simultaneously acquiring data on temperature, high-speed imaging, and infrared spectroscopy. The ignition response time and combustion time of the water-based monocomponent fuel at different temperatures are calculated using the high-speed imaging images; the temperature change at the center of the metal plate 5 during combustion is measured using the thermocouple signal 6; and the types of combustion products are determined using the infrared spectroscopy.

[0055] Figure 2 These are typical high-speed camera images of water-based monocomponent fuels. They show that after the fuel droplets contact the metal plate 5, the droplets first heat up, then the water evaporates, and the droplets concentrate and shrink. A flame appears only after 9258 ms. Therefore, the ignition response time of this water-based monocomponent fuel formulation is 9258 ms. For comparison, Figure 3 This is a typical high-speed photographic image of an oil-based monocomponent fuel droplet. The image shows that the oil-based fuel's ignition response time is 793 ms, recorded as 0 ms from contact with metal plate 5. Similarly, the combustion time of various fuel formulations can be tested using a similar method.

[0056] Figure 4The figure shows the temperature curve of the water-based monocomponent fuel droplet combustion process. As can be seen from the figure, the initial temperature (i.e., ignition temperature) of metal plate 5 is also 300.0℃. After the droplet contacts metal plate 5, a significant cooling phenomenon occurs, with the lowest temperature of metal plate 5 reaching 279.7℃, a drop of 20.3℃. Subsequently, the water-based monocomponent fuel begins to partially decompose and release heat, and the temperature rises slightly. At 9361 ms, the droplet is ignited, and the temperature of metal plate 5 rapidly rises to its maximum value of 655.4℃, then quickly falls back. Compared with oil-based monocomponent fuels, water-based monocomponent fuels exhibit a significant endothermic process with a longer duration. Although the instantaneous temperature reached during combustion is higher, the duration is short. This combustion characteristic makes it difficult to achieve self-sustaining stable combustion.

[0057] In contrast. Figure 5 This is the temperature curve corresponding to the combustion process of oil-based monocomponent fuel droplets. As can be seen from the figure, the initial temperature (i.e., ignition temperature) of metal plate 5 is 300.0℃. After the droplets contact metal plate 5, there is no significant cooling behavior. Since the oil-based monocomponent fuel is ignited at 793ms, the temperature of metal plate 5 rapidly rises to its first maximum value of 437.2℃ after 793ms. Subsequently, due to combustion fluctuations, the temperature of metal plate 5 fluctuates, reaching a maximum of 512.6℃. Overall, the entire combustion process is exothermic; although the temperature fluctuates, it is easily self-sustaining.

[0058] Figure 6 shows the infrared spectrum of the combustion products of water-based monocomponent fuel droplets. Figure 6(a) shows the background signal at 3200 cm⁻¹. -1 Up to 3600cm -1 Within the range, there is a broad and strong hydroxyl association peak, which is the OH stretching vibration peak, in the range of 1600-1700 cm⁻¹. -1 A moderate-intensity peak can be observed, representing the bending vibration peak of the OH group; these two OH peaks correspond to water vapor in the air. At 2350 cm⁻¹ -1 The C=O symmetric stretching vibration peak can be observed at 667 cm⁻¹. -1 We can see the C=O asymmetric stretching vibration peaks; these correspond to CO2 gas in the air.

[0059] Figure 6(b) shows a typical infrared spectrum of a water-based monocomponent fuel. From the figure, it can be seen that at 3200 cm⁻¹... -1 Up to 3600cm -1 Range of hydroxyl association peak and 1600-1700 cm -1 The bending vibration peak of OH is slightly enhanced; these two OH peaks correspond to water vapor in the droplet combustion products; at 2334 cm⁻¹ -1 2353cm -1 The C=O symmetric stretching vibration peak can be observed at 668 cm⁻¹. -1We can see the C=O asymmetric stretching vibration peaks; these peaks are significantly enhanced, corresponding to the CO2 gas produced by the combustion of fuel droplets; at 2117 cm⁻¹ -1 and 2166cm -1 At 3016 cm⁻¹, a relatively strong C=O stretching vibration peak appeared, corresponding to CO in the droplet combustion products; at 3016 cm⁻¹... -1 The peak at 1304 cm⁻¹ represents the CH stretching vibration. -1 The peak at this location corresponds to the CH bending vibration, which is a CH4 gaseous product. The above analysis shows that although water vapor and CO2 are present in the background air, the peak intensities corresponding to water vapor and CO2 increase significantly after fuel combustion, indicating the presence of these two gaseous products in the combustion products. Furthermore, characteristic peaks for CO and CH4 were observed, confirming that these gases are also included in the combustion products.

[0060] Figure 6(c) shows the infrared spectrum of another water-based single-component fuel formulation. From the figure, it can be seen that at 3200 cm⁻¹... -1 Up to 3600cm -1 Range of hydroxyl association peak and 1600-1700 cm -1 The bending vibration peaks of OH are slightly different from those at these two locations, which correspond to water vapor in the droplet combustion products; at 2340 cm⁻¹ -1 2361cm -1 The peak is a C=O symmetrical stretching vibration peak at 670 cm⁻¹. -1 These are C=O asymmetric stretching vibration peaks, and these peaks are significantly enhanced, corresponding to CO2 gas produced by the combustion of fuel droplets; at 2234 cm⁻¹ -1 2210cm -1 The peak represents the antisymmetric stretching vibration of the NNO bond; 1298 cm⁻¹ -1 1268cm -1 The peaks represent the symmetrical stretching vibrations of N2O, confirming the presence of N2O gaseous products in the droplet combustion products.

[0061] In contrast. Figure 7 This is the infrared spectrum of the combustion products of oil-based monocomponent fuel droplets, at 2328 cm⁻¹. -1 2368cm -1 The C=O symmetric stretching vibration peak can be observed, corresponding to the CO2 gas produced by the combustion of fuel droplets; at 2111 cm⁻¹ -1 and 2174cm -1 At 3016 cm⁻¹, a relatively strong C=O stretching vibration peak appeared, corresponding to CO in the droplet combustion products; at 3016 cm⁻¹... -1 The peak at 1304 cm⁻¹ represents the CH stretching vibration. -1The peak at this position corresponds to the CH bending vibration, which is a CH4 gaseous product. Compared to the spectrum of water-based monocomponent fuel 6(b), the CO2 peak is significantly weaker, while the CO and CH4 peaks are much stronger, indicating that CO and CH4 constitute a larger proportion of the combustion products of oil-based monocomponent fuel. Almost no H2O absorption peak was observed, indicating that the proportions of H2O and CO2 in the combustion products of oil-based monocomponent fuel are significantly reduced.

[0062] Depend on Figures 2-7 As can be seen, this method can perform real-time analysis of the fuel process of a single droplet of water-based monocomponent fuel, including images, temperature, and gaseous products. By analyzing images from the high-speed camera 10, the ignition response time and droplet combustion cycle of different water-based monocomponent fuel formulations can be calculated, thereby optimizing the ignition response of various formulations. By analyzing the temperature curves, the self-sustaining combustion behavior of different formulations can be determined, thus selecting water-based monocomponent fuel formulation components that are easy to achieve self-sustaining combustion. By analyzing the combustion products, the suitability of the oxygen-fuel ratio in the water-based monocomponent fuel formulation can be determined, thereby further optimizing the oxygen-fuel ratio. In summary, the method of this invention can optimize the design of water-based monocomponent fuel formulations from multiple aspects.

[0063] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-dimensional diagnostic method for the combustion behavior of water-based single-component fuel droplets, characterized in that, Includes the following steps: Water-based monocomponent fuel is added in single droplet form to a metal plate controlled by an electric heating furnace using a syringe. During the process of droplets contacting the metal plate and being heated and burned, temperature data, combustion images and infrared spectral signals of combustion products are collected in real time simultaneously at a frequency of ≥500Hz. Ignition response time, combustion time and minimum ignition temperature are calculated using temperature data and combustion images, and the types of combustion products are identified using infrared spectral signals. By monitoring the temperature change at the center of the metal plate, the stability of fuel droplet combustion and the ease of self-sustaining combustion can be determined.

2. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The dripping angle of the syringe is less than 15 degrees from the vertical direction, and the dripping height is 1cm-10cm from the syringe needle tip to the metal plate to ensure that the droplet size and dripping speed are consistent.

3. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The ignition response time is the time from droplet contact with the metal plate to the appearance of a flame, calculated using high-speed camera images. Specifically: The first frame of the image where the droplet contacts the metal plate is taken as the starting point, and the first frame of the image where the flame appears is taken as the ending point; Calculate the number of images n1 between two frames, the acquisition frequency of the high-speed camera n0Hz, and obtain the ignition response time t1=n1 / n0, in seconds.

4. The three-dimensional diagnostic method for the combustion behavior of water-based single-component fuel droplets according to claim 1, characterized in that, The burning time is the time from the appearance of the flame to its disappearance, calculated using images from a high-speed camera. Specifically: The first frame of the image where the flame appears is taken as the starting point, and the first frame of the image where the flame disappears is taken as the ending point; Calculate the number of images n2 between two frames, the acquisition frequency of the high-speed camera n0Hz, and obtain the burning time t2=n2 / n0, in seconds.

5. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The minimum ignition temperature is the lowest temperature at which the metal plate can ignite the droplets, and it is determined by gradually lowering the temperature of the metal plate until the droplets can no longer be ignited.

6. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The combustion products are identified by characteristic peaks in infrared spectroscopy, including one or more of H2O, CO2, CO, NO, N2O, NO2, CH4, and NH3.

7. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The temperature change at the center of the metal plate during combustion is measured by thermocouple signals. The temperature change reflects the heat absorption and release during the combustion of the fuel droplets, which helps to determine the stability of the fuel droplet combustion and the ease with which it can sustain stable combustion.

8. The three-dimensional diagnostic method for the combustion behavior of water-based monocomponent fuel droplets according to claim 1, characterized in that, The water-based single-component fuel consists of an oxidant, a fuel, and water as a solvent, wherein: The oxidizing agent is one or more of hydroxylamine nitrate, dinitramide ammonium, and hydrogen peroxide; The propellant is one or more of the following: triethanolamine nitrate, N,N-diethylhydroxylamine nitrate, hydrazine nitrate, ethylhydrazine nitrate, hydroxyethylhydrazine nitrate, ammonium nitrate, hydrazine, and methanol.

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