Method and system for analyzing factors influencing radial expansion of flash jet flow of oil sprayer

Abstract

The invention discloses a method and system for analyzing factors influencing radial expansion of flash jet flow of an oil injector, and relates to the field of oil injectors. Flash evaporation spraying images of the single-hole oil sprayer under different thermal working conditions are collected; the thermal working condition comprises injection temperature and environment pressure; obtaining a spraying width within a preset axial distance from a nozzle outlet according to the flash evaporation spraying image; establishing a nucleation rate model according to the injection temperature and the environment pressure; determining a nucleation rate index according to the nucleation rate model; taking the spray width as a measurement index of radial expansion, and establishing an incidence relation between the spray width and a nucleation rate index; according to the incidence relation, determining a factor influencing radial expansion: when the spray width is increased along with the increase of the nucleation rate index, the influence factor is the nucleation rate; when the spray width tends to be stable along with the increase of the nucleation rate index, the influence factor is heat energy required by vaporization.

Description

Technical Field

[0001] This invention relates to the field of fuel injectors, and more specifically, to a method and system for analyzing factors affecting the radial expansion of flash jets in fuel injectors. Background Technology

[0002] Flash evaporation is a phase transition process in which a liquid rapidly transforms into a gaseous state when suddenly exposed to an environment with a pressure lower than its saturation pressure. Flash evaporation has been widely observed and applied in fields such as automobiles, seawater desalination, spray cooling, and ice making. Flash evaporation involves several physical sub-processes, including nucleation, bubble growth, and bubble collapse. Fundamental research on the characteristics of flash jets has been extensively conducted.

[0003] Multi-jet injectors are now widely used in gasoline direct-injection (GDI) engines due to their ease of fuel distribution control. However, due to significant differences in thermal conditions within the combustion chamber, the spray exhibits various characteristics, one of which is the collapse phenomenon of multi-jet spray under flash conditions. Spray collapse significantly alters the expected air-fuel mixture distribution and can lead to negative effects such as fuel splatter. Fuel splatter results in fuel film buildup and increased smoke emissions, as well as dilution of the lubricating oil, which is considered one of the causes of super knock.

[0004] Numerous researchers have dedicated themselves to exploring the influencing factors and mechanisms of spray collapse, finding that superheat and nozzle structure are two key factors affecting spray collapse, with injectors having a higher number of nozzles and a more symmetrical structure exhibiting more severe spray collapse. Spray collapse is closely related to the interaction between multiple jets, and jet overlap caused by jet radial expansion is one of the necessary conditions for spray collapse. Therefore, to understand the jet overlap process, an important issue is the radial expansion of the jet and its influencing factors. However, using multi-orifice injectors makes it difficult to distinguish individual jets and assess their radial expansion. Therefore, further research using single-orifice GDI injectors is necessary.

[0005] Existing technologies contain numerous studies on flash jets from single-orifice nozzles. However, most of these studies were conducted under lower injection pressures compared to GDI injector operating conditions, or the nozzles used differed significantly in geometry from actual GDI injectors. Differences in injection pressure range and nozzle geometry lead to significant variations in flow states (such as nucleation rate and cavitation mode), which in turn significantly impact jet behavior, preventing the direct application of these findings to GDI injectors. Therefore, this application proposes a method for analyzing factors influencing the radial expansion of flash jets in injectors. The method characterizes the n-hexane jet ejected from a single-orifice GDI injector, analyzes the jet structure under a wide thermal operating range (injection temperature from 20°C to 100°C, ambient pressure from 4 kPa to 101 kPa), and identifies the factors affecting the radial expansion of the jet. Summary of the Invention

[0006] This invention provides a method and system for analyzing factors affecting the radial expansion of the flash jet of an injector, thereby overcoming at least one technical problem existing in the prior art.

[0007] On one hand, the present invention provides a method for analyzing factors affecting the radial expansion of the flash jet in an injector, comprising:

[0008] Install a single-hole injector inside a constant-volume container;

[0009] Flash spray images of the single-hole injector under different thermal conditions were acquired; the thermal conditions included injection temperature and ambient pressure.

[0010] The spray width within a predetermined axial distance from the nozzle outlet is obtained based on the flash spray image;

[0011] A nucleation rate model was established based on the injection temperature and ambient pressure.

[0012] Based on the nucleation rate model, determine the nucleation rate index;

[0013] Using the spray width as a measure of radial expansion, a correlation is established between the spray width and the nucleation rate index.

[0014] Based on the aforementioned correlation, the factors affecting radial expansion are determined as follows: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

[0015] Optionally, the injection temperature ranges from 20°C to 100°C, and the ambient pressure ranges from 4 kPa to 101 kPa.

[0016] Optionally, the spray width at a predetermined distance from the nozzle outlet is obtained based on the flash spray image, specifically as follows:

[0017] The spray image is preprocessed;

[0018] Determine the binarization threshold based on the preprocessed image;

[0019] A binary image is generated based on the binarization threshold.

[0020] Extract the spray edges from the binarized image;

[0021] The spray width is obtained by counting the number of pixels between the two edges of the spray.

[0022] Alternatively, the nucleation rate model can be expressed as:

[0023] Where σ represents surface tension, m represents the molecular mass of the liquid, and ΔG * K represents the free energy barrier. B T represents the Boltzmann constant. inj Indicates the injection temperature.

[0024] Alternatively, the nucleation rate index can be expressed as:

[0025] in, Δμ represents the chemical potential difference between the liquid and gas phases, v m Δμ represents the specific volume of a liquid; K B ·T inj ·ln(R p ), v m =m / (ρ l ·N A ), R p ρ represents the pressure ratio. l N represents the density of a liquid. A denoted as Avogadro's constant.

[0026] Optionally, the predetermined axial distance is 4 mm.

[0027] Optionally, when the influencing factor is the heat energy required for vaporization, the spray width increases with the increase of the spray temperature.

[0028] Optionally, a correlation is established between the spray width and the nucleation rate index, specifically as follows:

[0029] Plot the relationship curve between the spray width and the nucleation rate index;

[0030] Identify the linear growth phase and plateau phase of the relationship curve.

[0031] Optionally, the point between the linear growth phase and the plateau phase is a transition value, which increases with the increase of the injection temperature.

[0032] On the other hand, the present invention also provides a system for analyzing factors affecting the radial expansion of the flash jet of an injector, comprising:

[0033] Mounting module for mounting a single-hole injector within a constant-volume container;

[0034] The acquisition module is used to acquire flash spray images of the single-hole injector under different thermal conditions; the thermal conditions include injection temperature and ambient pressure.

[0035] The acquisition module is used to acquire the spray width within a predetermined axial distance from the nozzle outlet based on the flash spray image;

[0036] The first module is used to establish a nucleation rate model based on the injection temperature and ambient pressure.

[0037] The first determining module is used to determine the nucleation rate index based on the nucleation rate model;

[0038] The second module is used to establish a correlation between the spray width and the nucleation rate index, using the spray width as a measure of radial expansion.

[0039] The second determining module is used to determine the factors affecting radial expansion based on the correlation: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

[0040] The innovative aspects of this invention include:

[0041] In this embodiment, by correlating the nucleation rate with the spray width, it is analyzed that when the spray width increases with the increase of the nucleation rate index, the factor affecting radial expansion is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the factor affecting radial expansion is the heat energy required for vaporization, which is one of the innovative points of this embodiment. Attached Figure Description

[0042] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1A flowchart of a method for analyzing factors affecting the radial expansion of a fuel injector flash jet, provided by an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the internal geometry of a single-hole injector provided in an embodiment of the present invention;

[0045] Figure 3 A flowchart for obtaining spray width provided in an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of the spray image processing process;

[0047] Figure 5 Schematic diagram of spray patterns under different spray temperatures and ambient pressures;

[0048] Figure 6 This is a schematic diagram illustrating the effect of spray temperature on the spatially resolved spray width.

[0049] Figure 7 A schematic diagram illustrating the effect of environmental pressure on spatially resolved spray width;

[0050] Figure 8 The curves showing the relationship between spray width and nucleation rate under different axial distances;

[0051] Figure 9 This is a schematic diagram of a system for analyzing factors affecting the radial expansion of the flash jet of an injector, provided as an embodiment of the present invention. Detailed Implementation

[0052] 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. 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.

[0053] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0054] This invention discloses a method and system for analyzing factors affecting the radial expansion of flash jets in fuel injectors. These will be described in detail below.

[0055] Figure 1A flowchart illustrating a method for analyzing factors influencing the radial expansion of the flash jet in an injector, provided in an embodiment of the present invention, is provided below. Figure 1 The method for analyzing factors affecting the radial expansion of the flash jet in an injector, provided in this embodiment of the invention, includes:

[0056] Step 1: Install a single-hole injector inside the constant volume container;

[0057] Step 2: Acquire flash spray images of the single-hole injector under different thermal conditions; thermal conditions include injection temperature and ambient pressure;

[0058] Step 3: Obtain the spray width within a predetermined axial distance from the nozzle outlet based on the flash spray image;

[0059] Step 4: Establish a nucleation rate model based on the injection temperature and ambient pressure;

[0060] Step 5: Determine the nucleation rate index based on the nucleation rate model;

[0061] Step 6: Using spray width as a measure of radial expansion, establish the correlation between spray width and nucleation rate.

[0062] Step 7: Based on the correlation, determine the factors affecting radial expansion: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

[0063] For details, please refer to Figure 1 The method for analyzing factors affecting the radial expansion of the flash jet of a fuel injector, provided in this embodiment of the invention, analyzes the jet structure of a single-hole gasoline direct injection injector through experiments. Therefore, firstly, in step 1, a single-hole fuel injector is installed in a constant-volume container, and experiments are conducted in this container. In this embodiment, the single-hole gasoline direct injection injector is installed at the top of the container, and its internal geometry is as follows. Figure 2 As shown, the nozzle diameter is 0.176 mm and the length-to-diameter ratio (L / D) is 0.682.

[0064] In step 2, flash spray images of the single-hole injector under different thermal conditions were acquired. These thermal conditions included injection temperature and ambient pressure. The injection temperature was controlled by a heating element inserted into the container, and the ambient pressure was regulated by a centrifugal vacuum pump and monitored by an electronic pressure gauge with a sensitivity of 0.1 kPa. In the experiment, a high-speed camera (Phantom v7.3) combined with backlighting was used to capture the spray images, with a 150-watt LED as the light source. The spatial resolution of the images was 25 micrometers per pixel, and the exposure time was 1.0 microsecond.

[0065] In this invention, n-hexane is used as a single-component alternative fuel to gasoline. The experimental conditions are shown in Table 1, with injection temperature T... inj The temperature range is 20°C to 100°C, and the ambient pressure is P. amb The range is from 4 kPa to 101 kPa, with the injection pressure fixed at 10.0 MPa. The superheat is characterized by the ratio of ambient pressure to saturation pressure at the injection temperature, i.e., the pressure ratio Rp, and the specific values ​​are shown in Table 1.

[0066] Table 1

[0067]

[0068] As can be seen from the acquired spray images, the spray width provides more spatial resolution information. Therefore, in this invention, the spray width is used to determine the jet pattern. In step 3, the spray width is obtained based on the acquired spray images. It should be noted that, since the downstream spray is greatly affected by aerodynamics, this invention only discusses the spray width within a predetermined axial distance from the nozzle outlet. This predetermined distance can be, for example, 4 mm.

[0069] The spray width can be extracted using MATLAB. Figure 3 This is a flowchart illustrating how to obtain the spray width according to an embodiment of the present invention. Figure 4 (a) is a typical spray image. First, in step 31, the spray image is preprocessed, for example, by removing the background and enhancing the contrast, to obtain the image shown below. Figure 4 (b) shows the preprocessed image.

[0070] After obtaining the preprocessed image, in step 32, the optimal binarization threshold for distinguishing the spray area from the background area is determined. Here, the threshold can be determined using the Otsu method. In step 33, a binarized image is generated based on the binarization threshold, resulting in the image shown below. Figure 4 (c) shows the binarized image.

[0071] After obtaining the binarized image, the spray edge can be extracted from the binarized image in step 34, as shown below. Figure 4 (d) shows the spray edge image. After obtaining the spray edge image, in step 35, the spray width is obtained by counting the number of pixels between the two sides of the spray edge.

[0072] Figure 5The diagram illustrates the spray pattern under different injection temperatures and ambient pressures, with the corresponding pressure ratio (Rp) labeled for each condition. Generally, the jet can be divided into three regions based on superheat, as labeled A, B, and C in the diagram. Region A represents a subcooled fuel state, with a relatively small spray width. Region B corresponds to Rp between 1 and 2; in this region, the jet exhibits only slight radial expansion because the intensity of bubble generation is insufficient to trigger a significant burst. Region C corresponds to Rp greater than 2; in this region, significant radial expansion is observed, and the degree of radial expansion intensifies with increasing injection temperature and decreasing ambient pressure.

[0073] Figure 6 A schematic diagram illustrating the effect of injection temperature on spatially resolved spray width is shown, illustrating two cases with ambient pressures (Pamb) of 101 kPa and 20 kPa. Figure 6 (a) and Figure 6 In (b), the curves from top to bottom correspond to temperatures from top to bottom. For example, the top curve corresponds to 100℃, the second curve corresponds to 80℃, and so on. Figure 6 (a) It can be seen that under supercooled conditions (20°C to 60°C), the spray width is relatively similar; as the spray temperature (T) increases... inj As the temperature rises further, the liquid enters a superheated state, reaching 80℃ (R). p At 1.39°C, the spray width did not change significantly; however, at 100°C, the spray width increased significantly, indicating that the jet underwent radial expansion. Figure 6 In (b), the difference in spray width between the supercooled state (20°C) and the low superheat state (40°C, Rp=1.86) is also small, and the spray width increases sharply as the temperature further increases.

[0074] Figure 7 A schematic diagram illustrating the effect of ambient pressure on spatially resolved spray width is shown, illustrating two scenarios with spray temperatures of 60℃ and 100℃. Figure 7 (a) and Figure 7 (b) The curves from bottom to top correspond to a gradual decrease in environmental pressure, that is, the environmental pressure gradually decreases in the direction shown by the arrows in the figure.

[0075] exist Figure 7 In (a), the supercooled state (101 kPa and 80 kPa) and the low superheat (60 kPa, R) p The spray width is similar under the condition of R = 1.26; as the ambient pressure further decreases, the spray width increases. However, when the ambient pressure is below 20 kPa, the spray width within 1.0 mm of the nozzle outlet remains relatively stable with changes in ambient pressure, indicating that although the pressure ratio (R = 1.26) is relatively stable, the spray width is relatively stable with changes in ambient pressure. pThe pressure changed (from 3.79 to 18.96), but the bubble burst intensity remained relatively stable. When the ambient pressure decreased from 20 kPa to 4 kPa, the spray width increased beyond 1.0 mm from the nozzle exit. Since the bubble burst intensity was relatively stable, the increase in spray width was mainly attributed to the decrease in ambient resistance. The results also showed that within 1.0 mm of the nozzle exit, the effect of ambient resistance was not significant. Figure 7 A similar trend is also observed in (b).

[0076] To further explain the effects of injection temperature and ambient pressure on spray width, in step 4, a nucleation rate model is established based on the injection temperature and ambient pressure. Where σ represents surface tension, m represents the molecular mass of the liquid, and ΔG * K represents the free energy barrier. B T represents the Boltzmann constant. inj Indicates the injection temperature.

[0077] The nucleation rate is mainly determined by the exponential term, so the exponential term can be used as an indicator of the nucleation rate. However, for better presentation, in step 5, [the exponential term is omitted]. As an indicator of nucleation rate, among which... Δμ represents the chemical potential difference between the liquid and gas phases, v m The specific volume of a liquid is expressed as Δμ = K. B ·T inj ·ln(R p ), v m =m / (ρ l ·N A ), R p ρ represents the pressure ratio. l N represents the density of a liquid. A denoted as Avogadro's constant.

[0078] In step 6, spray width is used as a measure of radial expansion. A correlation is established between spray width and nucleation rate, and a curve showing the relationship between spray width and nucleation rate is plotted. Figure 8 (a) and (b) show the relationship curves between spray width and nucleation rate at different axial distances, and the linear growth stage and plateau stage are identified based on these curves.

[0079] After obtaining the relationship curve, in step 7, the factors influencing radial expansion can be determined based on the correlation. In this graph, two stages can be distinguished as Y increases. In the first stage, when Y is relatively low, the spray width increases almost linearly with Y. In the second stage, when Y exceeds a certain value, the spray width reaches a plateau, and the sensitivity to Y decreases. This trend is consistent with... Figure 7The results are consistent with those in the previous studies, indicating that the spray width remains relatively stable at low ambient pressure within a 1.0 mm range from the nozzle outlet. Furthermore, the spray width during both the transition and plateau periods increases with increasing injection temperature; that is, when the influencing factor is the heat energy required for vaporization, the spray width increases with increasing injection temperature.

[0080] Therefore, it can be determined that when the spray width increases with the increase of the nucleation rate index, the factor affecting radial expansion is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the factor affecting radial expansion is the heat energy required for vaporization.

[0081] When the nucleation rate is relatively low, the thermal energy in the fluid is sufficient to allow all bubbles to grow rapidly. The bubble bursting intensity is mainly determined by the number of bubbles, and the number of bubbles is positively correlated with the nucleation rate. Therefore, as Y increases, radial expansion is enhanced, and the spray width increases, which is related to... Figure 8 This corresponds to the first stage in the process. However, when the nucleation rate reaches a critical value, the thermal energy in the fluid is insufficient to allow all bubbles to grow rapidly. In this case, the nucleation rate is no longer the rate-controlling factor for bubble bursting; instead, the thermal energy required for vaporization becomes the determining factor. Figure 8 This corresponds to the second stage. Higher injection temperatures result in higher thermal energy, leading to increased bubble burst intensity and a higher plateau phase in the second stage. Furthermore, the higher thermal energy allows for more rapid bubble growth, thus increasing the transition value between the linear growth stage and the plateau phase.

[0082] Based on the same inventive concept, the present invention also provides a system for analyzing factors affecting the radial expansion of the flash jet in a fuel injector. Figure 9 A schematic diagram of a system for analyzing factors affecting the radial expansion of the flash jet in an injector, provided in an embodiment of the present invention, is shown below. Figure 9 The system for analyzing factors affecting the radial expansion of the flash jet in an injector, provided in this embodiment of the invention, includes:

[0083] Mounting module for mounting a single-hole injector within a constant-volume container;

[0084] The data acquisition module is used to acquire flash spray images of the single-hole injector under different thermal conditions; the thermal conditions include injection temperature and ambient pressure.

[0085] The acquisition module is used to acquire the spray width within a predetermined axial distance from the nozzle outlet based on the flash spray image;

[0086] The first module is used to establish a nucleation rate model based on the injection temperature and ambient pressure.

[0087] The first determining module is used to determine the nucleation rate index based on the nucleation rate model;

[0088] The second module is used to establish the relationship between spray width and nucleation rate, using spray width as a measure of radial expansion.

[0089] The second determining module is used to determine the factors affecting radial expansion based on the correlation: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

[0090] For details, please refer to Figure 9 The system provided in this embodiment of the invention analyzes the factors affecting the radial expansion of the flash jet of a fuel injector. Through experiments, the jet structure of a single-hole gasoline direct injection injector is analyzed. Therefore, firstly, a single-hole injector is installed in a constant-volume container using an installation module, and experiments are conducted within this container. In this embodiment, the single-hole gasoline direct injection injector is installed at the top of the container, and its internal geometry is as follows... Figure 2 As shown, the nozzle diameter is 0.176 mm and the length-to-diameter ratio (L / D) is 0.682.

[0091] The acquisition module captured flash spray images of the single-hole injector under different thermal conditions, including injection temperature and ambient pressure. The injection temperature was controlled by a heating element inserted into the container, while the ambient pressure was regulated by a centrifugal vacuum pump and monitored by an electronic pressure gauge with a sensitivity of 0.1 kPa. In the experiment, a high-speed camera (Phantom v7.3) combined with backlighting was used to capture spray images, with a 150-watt LED as the light source. The spatial resolution of the images was 25 micrometers per pixel, and the exposure time was 1.0 microsecond.

[0092] As can be seen from the acquired spray images, the spray width provides more spatial resolution information. Therefore, in this invention, the spray width is used to determine the jet pattern, and the acquisition module obtains the spray width based on the acquired spray images. It should be noted that, since the downstream spray is greatly affected by aerodynamics, this invention only discusses the spray width within a predetermined axial distance from the nozzle outlet, which can be, for example, 4 mm.

[0093] When obtaining the spray width, the spray image is first preprocessed, for example, by performing background subtraction and contrast enhancement, to obtain the following: Figure 4 (b) shows the preprocessed image.

[0094] After obtaining the preprocessed image, the optimal binarization threshold for distinguishing the spray area from the background area is determined. Here, the threshold can be determined using Otsu's method, and a binarized image is generated based on the binarization threshold, resulting in the image shown below. Figure 4 (c) shows the binarized image.

[0095] After obtaining the binarized image, the spray edge can be extracted from the binarized image to obtain, as shown below. Figure 4 (d) shows the spray edge image. After obtaining the spray edge image, the spray width is obtained by counting the number of pixels between the two sides of the spray edge.

[0096] refer to Figure 5 Based on superheat, the jet can be divided into three regions, as marked in the figure: region A, region B, and region C. Region A represents a subcooled fuel state, with a relatively small spray width. Region B corresponds to an Rp value between 1 and 2, where the jet exhibits only slight radial expansion because the intensity of bubble generation is insufficient to trigger a significant burst. Region C corresponds to an Rp value greater than 2, where significant radial expansion can be observed, and the degree of radial expansion intensifies with increasing injection temperature and decreasing ambient pressure.

[0097] exist Figure 6 (a) and Figure 6 In (b), the curves from top to bottom correspond to temperatures from top to bottom. For example, the top curve corresponds to 100℃, the second curve corresponds to 80℃, and so on. Figure 6 (a) It can be seen that under supercooled conditions (20°C to 60°C), the spray width is relatively similar; as the spray temperature (T) increases... inj As the temperature rises further, the liquid enters a superheated state, reaching 80℃ (R). p At 1.39°C, the spray width did not change significantly; however, at 100°C, the spray width increased significantly, indicating that the jet underwent radial expansion. Figure 6 In (b), the difference in spray width between the supercooled state (20°C) and the low superheat state (40°C, Rp=1.86) is also small, and the spray width increases sharply as the temperature further increases.

[0098] exist Figure 7 (a) and Figure 7 In (b), the curves from bottom to top correspond to a gradual decrease in environmental pressure, that is, the environmental pressure gradually decreases in the direction indicated by the arrows in the figure. Figure 7 In (a), the supercooled state (101 kPa and 80 kPa) and the low superheat (60 kPa, R) p The spray width is similar under the condition of R = 1.26; as the ambient pressure further decreases, the spray width increases. However, when the ambient pressure is below 20 kPa, the spray width within 1.0 mm of the nozzle outlet remains relatively stable with changes in ambient pressure, indicating that although the pressure ratio (R = 1.26) is relatively stable, the spray width is relatively stable with changes in ambient pressure. pThe pressure changed (from 3.79 to 18.96), but the bubble burst intensity remained relatively stable. When the ambient pressure decreased from 20 kPa to 4 kPa, the spray width increased beyond 1.0 mm from the nozzle exit. Since the bubble burst intensity was relatively stable, the increase in spray width was mainly attributed to the decrease in ambient resistance. The results also showed that within 1.0 mm of the nozzle exit, the effect of ambient resistance was not significant. Figure 7 A similar trend is also observed in (b).

[0099] To further explain the effects of injection temperature and ambient pressure on spray width, the first module establishes a nucleation rate model based on injection temperature and ambient pressure. Where σ represents surface tension, m represents the molecular mass of the liquid, and ΔG * K represents the free energy barrier. B T represents the Boltzmann constant. inj Indicates the injection temperature.

[0100] The nucleation rate is mainly determined by the exponential term, so the exponential term can be used as an indicator of the nucleation rate. However, for better presentation, the first determination module will... As an indicator of nucleation rate, among which... Δμ represents the chemical potential difference between the liquid and gas phases, v m The specific volume of a liquid is expressed as Δμ = K. B ·T inj ·ln(R p ), v m =m / (ρ l ·N A ), R p ρ represents the pressure ratio. l N represents the density of a liquid. A denoted as Avogadro's constant.

[0101] The second module establishes the relationship between spray width and nucleation rate as a measure of radial expansion, plots the relationship curve between spray width and nucleation rate, and identifies the linear growth stage and plateau stage based on the relationship curve.

[0102] After obtaining the relationship curve, the second determination module can identify the factors affecting radial expansion based on the correlation. In this graph, two stages can be distinguished as Y increases. In the first stage, when Y is relatively low, the spray width increases almost linearly with Y. In the second stage, when Y exceeds a certain value, the spray width reaches a plateau, and the sensitivity to Y decreases. This trend is consistent with... Figure 7The results are consistent with those in the previous studies, indicating that the spray width remains relatively stable at low ambient pressure within a 1.0 mm range from the nozzle outlet. Furthermore, the spray width during both the transition and plateau periods increases with increasing injection temperature; that is, when the influencing factor is the heat energy required for vaporization, the spray width increases with increasing injection temperature.

[0103] Therefore, it can be determined that when the spray width increases with the increase of the nucleation rate index, the factor affecting radial expansion is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the factor affecting radial expansion is the heat energy required for vaporization.

[0104] When the nucleation rate is relatively low, the thermal energy in the fluid is sufficient to allow all bubbles to grow rapidly. The bubble bursting intensity is mainly determined by the number of bubbles, and the number of bubbles is positively correlated with the nucleation rate. Therefore, as Y increases, radial expansion is enhanced, and the spray width increases, which is related to... Figure 8 This corresponds to the first stage in the process. However, when the nucleation rate reaches a critical value, the thermal energy in the fluid is insufficient to allow all bubbles to grow rapidly. In this case, the nucleation rate is no longer the rate-controlling factor for bubble bursting; instead, the thermal energy required for vaporization becomes the determining factor. Figure 8 This corresponds to the second stage. Higher injection temperatures result in higher thermal energy, leading to increased bubble burst intensity and a higher plateau phase in the second stage. Furthermore, the higher thermal energy allows for more rapid bubble growth, thus increasing the transition value between the linear growth stage and the plateau phase.

[0105] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0106] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0107] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing factors affecting the radial expansion of flash jets in fuel injectors, characterized in that, include: Install a single-hole injector inside a constant-volume container; Flash spray images of the single-hole injector under different thermal conditions were acquired; the thermal conditions included injection temperature and ambient pressure. The spray width within a predetermined axial distance from the nozzle outlet is obtained based on the flash spray image; A nucleation rate model was established based on the injection temperature and ambient pressure. Based on the nucleation rate model, determine the nucleation rate index; Using the spray width as a measure of radial expansion, a correlation is established between the spray width and the nucleation rate index. Based on the aforementioned correlation, the factors affecting radial expansion are determined as follows: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

2. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, The spray temperature ranges from 20°C to 100°C, and the ambient pressure ranges from 4 kPa to 101 kPa.

3. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, The spray width at a predetermined distance from the nozzle outlet is obtained based on the flash spray image, specifically as follows: The spray image is preprocessed; Determine the binarization threshold based on the preprocessed image; A binary image is generated based on the binarization threshold. Extract the spray edges from the binarized image; The spray width is obtained by counting the number of pixels between the two edges of the spray.

4. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, The nucleation rate model is expressed as: Where σ represents surface tension, m represents the molecular mass of the liquid, and ΔG * K represents the free energy barrier. B T represents the Boltzmann constant. inj Indicates the injection temperature.

5. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 4, characterized in that, The nucleation rate index is expressed as: in, Δμ represents the chemical potential difference between the liquid and gas phases, v m Δμ represents the specific volume of a liquid; K B ·T inj ·ln(R p ), v m =m / (ρ l ·N A ), R p ρ represents the pressure ratio. l N represents the density of a liquid. A denoted as Avogadro's constant.

6. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, The predetermined axial distance is 4 mm.

7. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, When the influencing factor is the heat energy required for vaporization, the spray width increases with the increase of the spray temperature.

8. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 1, characterized in that, The correlation between the spray width and the nucleation rate index is established as follows: Plot the relationship curve between the spray width and the nucleation rate index; Identify the linear growth phase and plateau phase of the relationship curve.

9. The method for analyzing factors affecting the radial expansion of the flash jet in an injector according to claim 8, characterized in that, The point between the linear growth phase and the plateau phase is a transition value, which increases as the injection temperature increases.

10. A system for analyzing factors affecting the radial expansion of flash jets in fuel injectors, characterized in that, include: Mounting module for mounting a single-hole injector within a constant-volume container; The acquisition module is used to acquire flash spray images of the single-hole injector under different thermal conditions; the thermal conditions include injection temperature and ambient pressure. The acquisition module is used to acquire the spray width within a predetermined axial distance from the nozzle outlet based on the flash spray image; The first module is used to establish a nucleation rate model based on the injection temperature and ambient pressure. The first determining module is used to determine the nucleation rate index based on the nucleation rate model; The second module is used to establish a correlation between the spray width and the nucleation rate index, using the spray width as a measure of radial expansion. The second determining module is used to determine the factors affecting radial expansion based on the correlation: when the spray width increases with the increase of the nucleation rate index, the influencing factor is the nucleation rate; when the spray width tends to stabilize with the increase of the nucleation rate index, the influencing factor is the heat energy required for vaporization.

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