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Article

Experimental Research on the Atomization Characteristics of Air-Induction Spray Based on Oil-Based Emulsion

by
Mingzhi Yan
1,
Fujun Chen
1,
Chen Gong
1,* and
Can Kang
2,*
1
School of Agricultural Engineering, Jiangsu University, Zhenjiang 212013, China
2
School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
*
Authors to whom correspondence should be addressed.
Agronomy 2025, 15(4), 936; https://doi.org/10.3390/agronomy15040936
Submission received: 20 March 2025 / Revised: 8 April 2025 / Accepted: 9 April 2025 / Published: 11 April 2025
(This article belongs to the Special Issue Advances in Precision Pesticide Spraying Technology and Equipment)
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Abstract

:
Spray drift is one of the major factors that causes pesticide loss and environmental pollution. Air-induction spray is an important anti-drift technology; however, the atomization characteristics of air-induction spray, particularly when the spray liquid is an oil-based emulsion, are not yet fully understood. In this paper, high-speed photography, PIV (particle image velocimetry) and image processing techniques are used to study the atomization characteristics of the air-induction spray under the oil-based emulsion condition. The structure of liquid sheet, the spatial distributions of the spray droplets size and the velocity are captured and measured. Additionally, the effects of spray pressure and nozzle configuration on atomization characteristics are discussed. The results indicate that, compared to water, air-induction spray under oil-based emulsion conditions exhibits a larger spray angle, a smaller droplet size, a narrower droplet size distribution and a higher droplet velocity. It is indicated that the oil-based emulsion reduces the size of bubbles within the liquid sheet, thereby decreasing the size of bubble-containing droplets. Furthermore, the oil-based emulsion alters the breakup mode of the liquid sheet, leading to an increase in droplet velocity and a narrower droplet size distribution. Both spray pressure and nozzle configuration have significant effect on the atomization characteristics. When the spray pressure changes from 0.1 MPa to 0.3 MPa and 0.5 MPa, the droplet size decreases by 10.56% and 15.67%, respectively, while the droplet velocity increases by 46.12% and 91.06%, respectively. When the nozzle changes from ID120-01 to ID120-03 and ID120-05, the droplet size increases by 20.64% and 33.99%, respectively, while the droplet velocity increases by 3.71% and 14.15%, respectively.

1. Introduction

Spraying is a commonly used method to deliver pesticides in agricultural contexts [1,2,3]. During the process of pesticide application, spray drift is a significant factors contributing to water and soil contamination [4,5,6]. To mitigate drift, air-induction nozzles are widely used in agricultural spray [7,8,9], and they have been recognized and recommended by the U.S. Environmental Protection Agency (EPA) [10]. However, our current understanding of the atomization characteristics of air-induction sprays is still insufficient, particularly when the spray medium is pesticide. Pesticides may change the physicochemical properties of the spray liquid, which is supposed to have an important effect on the atomization characteristics [11].
Air-induction nozzles feature a Venturi structure [12]. Due to their special structural design, during spray atomization, air can be automatically sucked in according to the Venturi effect, and then mixed with the liquid in the flow channel inside the nozzle, forming a gas–liquid flow [13]. The atomization of the gas–liquid flow is supposed to produce spray droplets with air bubbles inside [14,15], thus having a relatively larger droplet size. Larger droplets are beneficial for suppressing spray drift and achieving better drift reduction effects. At the same time, when the liquid droplets with air bubbles hit the target crops, the breakup of air bubbles promotes droplet deposition [16,17].
For water or water-based solutions, the droplet size distribution, droplet mean velocity and drift potential of air-induction spray has been widely investigated [16,18]. For oil-based emulsion spray, the studies are limited. Previous researchers compared the spray characteristics of oil-based emulsions and pure water under standard flat-fan nozzles [19,20,21,22]. It was found that oil-based emulsion spray has a relatively larger droplet size compared with water. The generation of perforation in the spray sheet is supposed to be responsible for the difference between water and oil-based emulsions spray [11,21]. In addition to droplet size, droplet velocity is another important parameter for characterizing atomization characteristics. PIV (particle image velocimetry) is widely used to measure the velocity distribution in flow fields [22,23,24]. Dorr et al. used PIV to measure the velocity of liquid sheet and droplets of air-induction nozzles and standard fan nozzles [24]. The research results showed that the initial velocity of droplets from air-induction nozzles was lower than that of standard fan nozzles.
In this paper, the atomization characteristics of air-induction spray based on oil-based emulsion were investigated. High-speed microscopy was used to capture the sheet structure and spray droplets. Image processing methods were used to quantitatively measure the atomization angle and the spatial distribution of spray droplet size. The spatial distribution of droplet velocities was measured using particle image velocimetry. The relationship between spray structure, spray angle and the spatial distribution of the spray droplets was discussed. In addition, the effects of spray pressure and nozzle configuration on the sheet structure and spray droplets were investigated. The research results help deepen our understanding of the atomization characteristics of air-induction spray.

2. Materials and Methods

2.1. Experimental Equipment and Method

The experimental setup and the nozzles used in this study are shown in Figure 1. The experimental setup consists of a high-speed camera (Olympus Co., Shinjuku-ku, Tokyo, Japan) equipped with a macro lens (Tokina Macro 100 F2.8 D, Olympus Co., Shinjuku-ku, Tokyo, Japan), an adjustable bracket, three air-induction nozzles (ID-120-01, ID-120-03, ID-120-05, Lechler Inc., Metzingen, Germany), a diffuser (to make the background illumination more uniform), a backlight source, a regulator valve (SMC AR-3000, SMC China Co., Shanghai, China, the precision of the regulator valve is 0.02 MPa), a spray solution pressure vessel (with a capacity of 10 L), an air compressor (JB-750 × 3-65 L) and liquid piping. In the experiments, three spray pressures of 0.1 MPa, 0.3 MPa and 0.5 MPa were selected, covering the commonly used pressure range in agricultural spraying (Table 1).
Water and an oil-based emulsion were used as spray solutions, which were stored in a pressure vessel pressurized by an air compressor. The oil-based emulsion was prepared by mixing water and pre-emulsified herbicide butachlor, with a spray concentration of 0.1% v/v in the experiment. The butachlor used in this study was produced by Jiangsu Lvlai Co., Ltd., (Jiangsu, China) with a total active ingredient content of 60% butachlor emulsion. Under room temperature conditions of 23–25 °C, the static surface tension of the water and oil-based emulsion were measured using a contact angle measuring device, as shown in Figure 2. The measuring device included an OCA optical contact angle measuring instrument (OCA25, German Dataphysics KRUSS BP100, A.KRÜSS Optronic GmbH, Hamburg, Germany) and a software system. The liquid surface tension was measured using the pendant drop method [25]. The measured static surface tension of water and the oil-based emulsion were 0.07 N m−1 and 0.04 N m−1, respectively. A total of six sets of experiments were designed in this study. Groups 1 and 2 discussed the differences between water and oil-based emulsion sprays. Groups 2 to 4 evaluated the effect of spray pressure on air-induction spray based on oil-based emulsion. Groups 3, 5 and 6 evaluated the effect of nozzle configuration on the air-induction spray based on the oil-based emulsion. The parameters under different experimental conditions are shown in Table 2.

2.2. Capturing of Liquid Sheet and Spray Droplets

The center point of the nozzle exit was defined as the origin of all coordinates, with the right horizontal direction (transverse direction) being the X direction, the vertical downward direction (flow direction) being the Y direction, and the Z direction perpendicular to the XOY plane, as shown in Figure 3. High-speed photography was used to capture spray images at different Y distances. Taking Figure 3 as an example, the first image ① near the nozzle exit was captured (as shown by the blue-dashed rectangle). Then, the second image ② was captured at a downstream interval of 100 mm (represented by the solid rectangle). This process was repeated 5 times, capturing images of the spray atomization structure within the range of 0–500 mm. During the process, the spray conditions were kept constant. To capture transient spray structures, the exposure time of the high-speed camera was set to 2.16 μs. The frame rate was set to 2000 f/s; therefore, the time interval between adjacent images was 0.5 ms. Under these conditions, the image resolution was 1280 × 1024 pixels. Before the experiment, the actual length of each nozzle was measured with a ruler. The pixel length of the nozzle in the spray image was measured using commercial image analysis software IPP v7.1 (Image Pro Plus, Meyer Instruments, Houston, TX, USA). The ratio of the two measured lengths was defined as the scale factor SF (SF = actual length/pixel length).

2.3. Measurement of Spray Angles

The spray angle significantly affects the atomization area and deposition distribution characteristics, and is a typical parameter for describing atomization performance [26]. The spray angle was measured as shown in Figure 4. Two red lines were drawn along the edges of the liquid sheet, and the angle formed by these two lines was defined as the spray angle. To reduce random error, the spray angles of 100 liquid sheets at different times were measured, and the average value was used.

2.4. Measurement of Droplet Size

In this paper, the size of the droplets was measured based on image processing. A typical image processing process is shown in Figure 5. The captured sampling window size was 10 × 10 mm. First, the original image was enhanced based on the Retinex theory to highlight the edge strength gradient between the background and the target droplets. Then, the Otsu algorithm was used to determine the segmentation threshold, resulting in a binary image, after which the image was inverted based on pixel values. Finally, median filtering and hole-filling functions were used to remove noise in the image and fill holes in the droplets. After image preprocessing, the Bwlabel and Regionprops functions in MATLAB (MATLAB R2023a) software were used to detect and measure the size of the spray droplets. Then, a set of image batch-processing code was independently developed based on the commercial code software MATLAB to calculate the volume median diameter (DV50) of the spray droplets [27]. To reduce random errors and ensure a sufficient sample, multiple images were processed and measured under the same experimental conditions. Under each experimental condition, at least 100 spray images and 3000 spray droplets were processed and measured.

2.5. Measurement of Droplet Mean Velocity

The PIV measurement system was used to measure the mean velocities of droplets is shown in Figure 6a. The PIV system mainly consists of a laser, a CCD camera, a power supply, a synchronizer and a software system (TSI, Shoreview, MN, USA).
Spray droplets have a relatively small size; therefore, they can be used as tracer particles. The frame rate of the CCD camera was set to 40 f/s, and the time interval (∆t) between two consecutive laser double pulses was set to 50 μs. The captured area of the CCD camera was 150 mm × 100 mm. The principle of PIV velocity measurement is to capture two consecutive frames of images of the same tracer particle (droplet) in the flow field, then calculate the droplet velocity based on the displacement of droplet and time interval, as shown in Figure 6 [28]. Ultimately, the Tecplot software (Tecplot 360 EX2020 R1, American Tecplot, Bellevue, WA, USA), a flow field visualization tool, was employed to analyze and process the captured droplet velocity data, resulting in velocity field contour plots and vector diagrams.

3. Results and Analysis

3.1. Comparison of Atomization Characteristics Between Water and Oil-Based Emulsion Air-Induction Spray

The liquid sheet images and spray angle distributions for water and oil-based emulsion sprays are shown in Figure 7. The nozzle is ID120-03, and the spray pressure is 0.1 MPa for both. Under water spray conditions, there are many bubbles with different sizes in the liquid sheet, as shown in Figure 7a (elevation view of the liquid sheet). There are also some perforations in the liquid sheet. When the oil-based emulsion was used, the size of bubbles in the liquid sheet significantly decreased. Unlike the water spray, a mesh-like structure appeared in the liquid sheet, and this structure caused the early breakup of the liquid sheet.
The side-view images of water and oil-based emulsion liquid sheets are compared in Figure 7b. The fluctuation amplitude of the water spray is greater than that of the oil-based emulsion spray, and the liquid sheet of oil-based emulsion spray breaks up earlier. The spray angles were measured and compared in Figure 7c,d. The average spray angle for water spray was 72.17° (with a standard deviation of 5.06), while that for oil-based emulsion spray was 79.19° (with a standard deviation of 5.54). Compared to water, the oil-based emulsion increased the spray angle by 9.73%. A possible reason for this is that the oil-based emulsion solution has a smaller surface tension. This favors the extension of the liquid sheet in the X direction, thereby increasing the spray angle.
The spatial distributions of spray droplets under different spray liquids were compared, as shown in Figure 8. From the droplet images, it can be seen that at the same Y direction, the average droplet size of water spray is larger than that of the oil-based emulsion spray, while the droplet number for the water spray is lower than that of the oil-based emulsion spray. The average droplet size decreases with Y distance for both the water and oil-based emulsion spray.
The volume median diameter (DV50) is commonly used to quantitatively describe the droplet size in agricultural spray. The droplet size distribution of the water and oil-based emulsion spray were measured and compared, and are shown in Figure 9. It can be seen that the droplet sizes of both water and oil-based emulsion sprays decrease with the increase in Y distance. Interestingly, at the same Y distance, the droplet size of the water spray is larger than that of oil-based emulsion spray, but the difference in droplet size between water and oil-based emulsion sprays decreases with the increase in Y distance. The oil-based emulsion spray reduced the DV50 of droplets by 12.73%. Furthermore, at the position of Y = 100 mm, the size distribution of droplets for water and oil-based emulsion sprays was measured. It can be seen that water spray has a relatively bigger droplet size, while the droplet size of oil-based emulsion spray distributes in a narrower range.
The reasons for the larger droplet size of water spray are proposed here. One is due to the larger surface tension. It can be seen from Table 2 that the surface tension of the water spray liquid is larger than that of oil-based emulsion spray liquid. A smaller surface tension helps the extension of the liquid sheet, which decreases the thickness of the liquid sheet, and generates smaller spray droplets. The second reason is due to the decrease in bubble size in the liquid sheet. The average bubble size in the liquid sheet of water spray is obviously larger than the oil-based emulsion spray; see Figure 8. Air-induction spray is supposed to produce droplets with air bubbles inside. Clearly, bigger bubbles correspond to a bigger droplet size.
The droplet mean velocity of water and the oil-based emulsion spray are compared in Figure 10. From the velocity cloud images, it can be seen that the atomization flow fields of different spray solutions are approximately symmetrically distributed, with the maximum velocity being near the nozzle exit. The maximum velocities for the water spray and oil-based emulsion spray were approximately 9.14 m/s and 9.38 m/s, respectively. In the rear region of the flow field far from the nozzle, the velocity is lower, and the velocity in the front and rear flow field regions shows a decreasing trend. When it was water spray, the range of the high-speed mainstream region of droplets was narrower, mainly concentrated in the area where −20 mm ≤ X ≤ 20 mm, and the velocity field fluctuated within a certain range. For oil-based emulsion spray, the range of the high-speed mainstream region of droplets expanded, mainly concentrated in the area where −30 mm ≤ X ≤ 30 mm. The velocity cloud image of the high-speed mainstream region of the flow field had a uniform color scale distribution, indicating that the velocity field distribution was more stable.
In order to quantitatively analyze the differences in the spatial velocity distribution of spray droplets under different spray liquids, the distribution of droplet spatial velocity along the axial and radial directions was extracted based on the velocity cloud images. The droplet velocity distributions of the two sprays along the centerline of the nozzle exit are shown in Figure 11a. The droplet velocities of water and the oil-based emulsion spray both gradually decrease with Y distance. The velocity of the oil-based emulsion spray decreases more gently. The distributions of droplet velocity along the radial direction at different axial positions (Y = 30 mm, Y = 50 mm, Y = 70 mm) under different spray liquids are shown in Figure 11b,c. The overall distribution of droplet velocity shows a trend of being higher in the center and gradually decreasing towards the edges. The decay in droplet velocity from the center to the edge for the oil-based emulsion spray is greater than that for the water spray. This is because the atomization angle of the oil-based emulsion spray is larger, and droplets take a longer time to reach the edge of the atomization, resulting in greater velocity decay. At the same time, as the Y distance increases, the droplet velocity decays towards the edge. After the velocity decays to a certain radial position (outside the high-speed mainstream region), the trend of droplet velocity distribution changes, and the larger the Y distance, the greater the edge droplet velocity. This is due to the fact that the spray atomization flow field is distributed in a fan shape. As the Y distance increases, the expansion amplitude in the X direction increases, and the high-speed mainstream region also expands, with the proportion of the span increasing. Therefore, when a certain radial position is reached, the velocity increases.

3.2. The Effect of Spray Pressure on the Atomization Characteristics of Oil-Based Emulsion Air-Induction Sprays

The liquid sheets and spray angle of the oil-based emulsion air-induction spray at different spray pressures are compared in Figure 12. From the liquid sheet images, it can be seen that when the spray pressure is relatively low (0.1 MPa), the liquid sheet is more intact, with fewer holes and mesh-like structures. As the spray pressure increases, the liquid sheet breaks up more severely, with more holes and mesh-like structures generated. The spray angles at spray pressures of 0.1 MPa, 0.3 MPa, and 0.5 MPa were 79.19°, 102.08°, and 114.78°, respectively, with standard deviations of 5.54, 5.30, and 7.42. When the spray pressure increased from 0.1 MPa and 0.5 MPa, the atomization spray angles increased by 28.91% and 44.94%, respectively. The larger the spray pressure, the greater the kinetic energy of the spray liquid; therefore, the liquid sheet has more energy to extend and lead to larger spray angle. Spray is a turbulence flow, and the spray angle fluctuates within a certain range. When the spray pressure is low, the kinetic energy of liquid sheet is small, and the standard deviation of the spray angle is small. An alternative reason is that at high pressures, the volume expansion of the outflowing air bubbles increases, which may contribute to the observed fluctuations in the spray angles.
The spatial distribution images of spray droplets at different spray pressures are compared in Figure 13. From the droplet images, it can be seen that at different spray pressures, the droplet size decreases with the increase in the Y distance. At the same Y distance, the droplet size decreases with the increase in spray pressure. From the liquid sheet images at different spray pressures in Figure 13, it can be seen that the increase in spray pressure enables the liquid sheet to obtain higher atomization momentum, leading to more severe breakup and reducing the initial droplet size of the droplet group. The initial droplet size determines the size distribution of droplets in the entire space.
At different spray pressures, the droplet size decreases with the axial distance, as shown in Figure 14. As the spray pressure increases, the droplet size significantly decreases. When the spray pressure changes from 0.1 MPa to 0.3 MPa and 0.5 MPa, the droplet size decreases by 10.56% and 15.67%, respectively. The reduction rate of droplet size in the axial direction is different at different spray pressures. When the spray pressure was 0.1 MPa, 0.3 MPa and 0.5 MPa, the reduction rates of droplet size in the axial direction were 8.99%, 9.00% and 12.60%, respectively. As the spray pressure increased, the reduction rate in the axial direction gradually increased. This means that higher spray pressure gives the spray liquid higher kinetic energy, making the atomization more intense and resulting in a higher droplet size reduction rate.
The mean velocity cloud images of oil-based emulsion air-induction sprays at different spray pressures are shown in Figure 15. The overall distribution of the spatial velocity distribution cloud images under each spray pressures shows the maximum velocity near the nozzle exit. The maximum droplet velocities under the spray pressures of 0.1 MPa, 0.3 MPa, and 0.5 MPa are 9.28 m/s, 13.56 m/s, and 17.73 m/s, respectively. The maximum droplet velocities increased by 46.12% and 91.06% with the increase in spray pressure. In the rear region of the flow field far from the nozzle, the velocity is smaller and shows a uniform decay distribution. When the atomization flow field reaches a certain axial distance, the expansion in the radial direction weakens, and a significant reduction can be seen at the edges of the flow field. The width of the high-speed mainstream region of the flow field also differs at different spray pressures. At spray pressures of 0.1 MPa, 0.3 MPa and 0.5 MPa, the range of the high-speed mainstream region of the flow field can reach X = ±20 mm, X = ±25 mm and X = ±40 mm, respectively. This indicates that the range of the mainstream region of the flow field increases with the increase in spray pressure.
The spatial distribution of the mean velocity of oil-based emulsion sprays at different spray pressures is shown in Figure 16. The distribution of droplet spatial velocity along the axial direction at different spray pressures is shown in Figure 16a. The droplet velocity decreases with the increase in Y distance. At spray pressures of 0.1 MPa, 0.3 MPa and 0.5 MPa, the maximum axial velocities of the flow field are 9.28 m/s, 13.56 m/s and 17.73 m/s, respectively. When the spray pressure changes from 0.1 MPa to 0.3 MPa and 0.5 MPa, the increases in velocity along the axial direction are 44.97% and 90.05%, respectively. The decrease in spatial velocity along the axial direction at different spray pressures is gentle, with almost no fluctuation.
The distribution of droplet velocity along the radial direction at different axial positions (Y = 30 mm, Y = 50 mm, Y = 70 mm) at different spray pressures was measured, as shown in Figure 16b–d. The overall distribution of droplet velocity shows a trend of being higher in the center and gradually decreasing towards the edges. The increase in spray pressure does not change the trend of velocity distribution. Within the range of the velocity mainstream region, the velocity decreases with the increase in Y distance. When the velocity develops beyond the mainstream region, significant changes occur, and the edge velocity further away from the nozzle is greater than the edge velocity closer to the nozzle.

3.3. The Effect of Nozzle Configuration on the Atomization Characteristics of Oil-Based Emulsion Air-Induction Sprays

The liquid sheet and spray angles of different nozzle configuration were compared are shown in Figure 17. As the nozzle configuration changes from ID120-01 to ID120-03 and ID120-05, the liquid sheet breakup length moves away from the nozzle exit, and the liquid sheet area significantly increases. The liquid sheet is characterized by a mesh-like porous structure. Based on the liquid sheet structure, the spray angles were measured for ID120-01, ID120-03 and ID120-05 nozzles, which were found to be 94.44°, 102.08° and 104.63°, respectively, with standard deviations of 4.55, 5.30 and 5.34. The spray angles increased by 8.09% and 10.79%, respectively. Under a certain spray pressure, the change in nozzle configuration increases the spray atomization angle, which is due to the impact of the differences in the internal structural dimensions of the nozzle. However, the increase in the spray angle is also subject to certain limitations.
The spatial distribution images of spray droplets at different nozzle configurations are compared in Figure 18. When the nozzle changes from ID120-01 to ID120-03 and ID120-05, the average droplet size and the droplet number generally increases. The size difference in nozzle exit is supposed to be responsible for the difference in spray droplets. The nozzle ID120-05 has a larger nozzle exit; therefore, it produces a thicker liquid sheet. As a result, larger spray droplets are produced. At the same spray pressure, a large nozzle exit corresponds to a large volume flow rate, which means that more liquid is atomized into droplets. The quantitative information of droplet size along the Y direction is shown in Figure 19. When the nozzle configuration changes from ID120-01 to ID120-03 and ID120-05, the DV50 of the oil-based emulsion spray increased by 20.64% and 33.99%, respectively.
The mean velocity cloud images of oil-based emulsion sprays at different nozzle configuration are shown in Figure 20. The overall distribution of the spatial velocity distribution cloud images at different nozzle configurations shows the maximum velocity being near the nozzle exit. The maximum velocities for ID120-01, ID120-03 and ID120-05 nozzles are 13.14 m/s, 13.56 m/s and 14.76 m/s, respectively. It can also be seen that as the nozzle configuration changes, the mainstream region of the mean velocity gradually expands and the velocity increases. The nozzle configuration has a significant effect on the velocity field.
The variation in spatial velocity along the axial direction for different nozzle configurations is shown in Figure 21a. When the nozzle changes from ID120-01 to ID120-03 and ID120-05, the maximum velocities increase from 12.93 m/s to 13.41 m/s and 14.76 m/s, respectively. The velocity increase ratios are 3.71% and 14.15%. This indicates that under a certain spray pressure, the change in nozzle configuration can significantly enhance the droplet velocity.
The radial distribution maps of spatial velocity at different nozzle configurations are shown in Figure 21b–d. It can be seen that the trend of spatial velocity distribution in the radial direction is generally the same at different nozzle configurations, with the maximum velocity appearing near the center of the nozzle exit, at 12.71 m/s, 13.27 m/s and 14.59 m/s, respectively, and gradually decreasing in the axial and radial directions. For the velocity atomization fields at different nozzle configurations, there are slight variations in the trend of spatial velocity changes in the radial direction. Taking the velocity atomization field at the ID120-01 nozzle as an example, the velocity significantly decreases as it moves away from the center of the X-axis. From the liquid sheet image in Figure 17, it can be seen that its sheet length and area are relatively small, leading to the early breakup of the liquid sheet and the earlier formation of droplets. As a result, the velocity decays earlier during atomization in the radial direction, making the trend of velocity changes in the radial direction more pronounced.

4. Conclusions

In this study, the atomization characteristics of air-induction spray based on oil-based emulsion were investigated. The structure of the liquid sheet, spray angle, droplet size, and velocity distribution were captured and measured. The effects of spray pressure and nozzle configuration on the atomization characteristics were discussed. The main conclusions drawn from this study are as follows:
1.
When the spray liquid changes from water to oil-based emulsion, the atomization characteristics of air-induction spray significantly change. For the water spray, the liquid sheet features relatively bigger bubbles and holes. For the oil-based emulsion spray, the bubble size is significantly reduced, and the presence of oil droplets causes the liquid sheet to break up into a mesh-like structure, promoting the early formation of droplets.
2.
The oil-based emulsion spray had a larger angle, which was 9.73% larger than that of water spray. Furthermore, the oil-based emulsion spray had a smaller droplet size; the DV50 of oil-based emulsion spray droplets was 12.73% smaller than that of water spray droplets. The droplet velocity of oil-based emulsion spray is larger than water spray, and its velocity distribution is more stable.
3.
The increase in spray pressure intensified the atomization and breakup of the liquid sheet of oil-based emulsion air-induction spray. As the spray pressure increases, the liquid sheet breaks up more severely, with more holes and mesh-like structures generated. When the spray pressure increased from 0.1 MPa to 0.3 MPa and 0.5 MPa, the spray angle increased by 28.91% and 44.94%, respectively, and the DV50 of droplets decreased by 10.56% and 15.67%, respectively. The maximum velocity increased by 46.12% and 91.06%, respectively.
4.
The change in nozzle configuration had a relatively small impact on the change in spray angle. When the nozzle configuration changed from ID120-01 to ID120-03 and ID120-05, the spray angle increased by 8.09% and 10.79%, respectively. The nozzle configuration did not change the form of atomization and breakup, but it had a significant impact on droplet size and velocity. When the nozzle changed from ID120-01 to ID120-03 and ID120-05, the droplet size increased by 20.64% and 33.99%, respectively, while the droplet velocity increased by 3.71% and 14.15%.

Author Contributions

Methodology, C.G.; data acquisition, F.C.; writing—original draft preparation, M.Y.; writing—review and editing, C.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (nos. 51905220, 52311540154), Natural Science Foundation of Jiangsu Province, China (no. BK20231325) and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (no. PAPD-2023-87).

Data Availability Statement

Data will be made available on request.

Acknowledgments

The authors thank the College of Agricultural Engineering of Jiangsu University for the experimental equipment.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Schematic diagram of the experimental device; (b) nozzle side view; (c) nozzles.
Figure 1. (a) Schematic diagram of the experimental device; (b) nozzle side view; (c) nozzles.
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Figure 2. Contact angle measuring system. Red dashed circle indicates the syringe.
Figure 2. Contact angle measuring system. Red dashed circle indicates the syringe.
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Figure 3. Schematic diagram of image capture.
Figure 3. Schematic diagram of image capture.
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Figure 4. Measurement of spray angle.
Figure 4. Measurement of spray angle.
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Figure 5. Image processing process.
Figure 5. Image processing process.
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Figure 6. PIV measure system: (a) experimental apparatus for droplet velocity measurement; (b) PIV velocity measuring principle.
Figure 6. PIV measure system: (a) experimental apparatus for droplet velocity measurement; (b) PIV velocity measuring principle.
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Figure 7. Comparison of water and oil-based emulsion liquid sheet: (a) elevation view of water and oil-based emulsion liquid sheet; (b) side view of water and oil-based emulsion liquid sheet; (c) water spray angle; (d) oil-based emulsion spray angle.
Figure 7. Comparison of water and oil-based emulsion liquid sheet: (a) elevation view of water and oil-based emulsion liquid sheet; (b) side view of water and oil-based emulsion liquid sheet; (c) water spray angle; (d) oil-based emulsion spray angle.
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Figure 8. Spatial distribution image of droplets for different spray liquids.
Figure 8. Spatial distribution image of droplets for different spray liquids.
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Figure 9. Comparison of droplet size of water and oil-based emulsion spray. (a) Variation in volume along the Y distance. (b) Droplet size distribution at the position of Y = 100 mm.
Figure 9. Comparison of droplet size of water and oil-based emulsion spray. (a) Variation in volume along the Y distance. (b) Droplet size distribution at the position of Y = 100 mm.
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Figure 10. Mean velocity distribution of air-induction spray at different spray liquid: (a) water spray; (b) oil-based emulsion spray.
Figure 10. Mean velocity distribution of air-induction spray at different spray liquid: (a) water spray; (b) oil-based emulsion spray.
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Figure 11. (a) Mean velocity distribution along the axial direction; (b) mean velocity distribution of water spray along the radial distribution; (c) mean velocity distribution of oil-based emulsion spray along the radial distribution.
Figure 11. (a) Mean velocity distribution along the axial direction; (b) mean velocity distribution of water spray along the radial distribution; (c) mean velocity distribution of oil-based emulsion spray along the radial distribution.
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Figure 12. (a) Liquid sheets of the oil-based emulsion air-induction spray at different spray pressures; (b) spray angle of the oil-based emulsion air-induction spray at different spray pressures.
Figure 12. (a) Liquid sheets of the oil-based emulsion air-induction spray at different spray pressures; (b) spray angle of the oil-based emulsion air-induction spray at different spray pressures.
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Figure 13. Spatial distribution image of droplets at different spray pressure.
Figure 13. Spatial distribution image of droplets at different spray pressure.
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Figure 14. Axial distribution of droplet size at different spray pressures.
Figure 14. Axial distribution of droplet size at different spray pressures.
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Figure 15. Mean velocity distribution of air-induction spray at spray pressure: (a) 0.1 MPa; (b) 0.3 MPa; (c) 0.5 MPa.
Figure 15. Mean velocity distribution of air-induction spray at spray pressure: (a) 0.1 MPa; (b) 0.3 MPa; (c) 0.5 MPa.
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Figure 16. Spatial distribution of mean velocity at different spray pressures: (a) spatial velocity at different spray pressures along the axial distribution; (b) radial distribution at 0.1 MPa pressure; (c) radial distribution under 0.3 MPa pressure; (d) radial distribution under 0.5 MPa pressure.
Figure 16. Spatial distribution of mean velocity at different spray pressures: (a) spatial velocity at different spray pressures along the axial distribution; (b) radial distribution at 0.1 MPa pressure; (c) radial distribution under 0.3 MPa pressure; (d) radial distribution under 0.5 MPa pressure.
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Figure 17. Spray image and spray angle at different nozzle configurations.
Figure 17. Spray image and spray angle at different nozzle configurations.
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Figure 18. Spatial distribution images of droplets at different nozzle configurations.
Figure 18. Spatial distribution images of droplets at different nozzle configurations.
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Figure 19. Axial distribution of droplet size at different nozzle configurations.
Figure 19. Axial distribution of droplet size at different nozzle configurations.
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Figure 20. Mean velocity cloud images at different nozzle configuration: (a) ID120-01; (b) ID120-03; (c) ID120-05.
Figure 20. Mean velocity cloud images at different nozzle configuration: (a) ID120-01; (b) ID120-03; (c) ID120-05.
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Figure 21. (a) Spatial velocity at different nozzle configuration along the axial distribution; (b) spray spatial velocity along the radial distribution for the ID120-01 nozzle; (c) spray spatial velocity along the radial distribution for the ID120-03 nozzle; (d) spray spatial velocity along the radial distribution for the ID120-05 nozzle.
Figure 21. (a) Spatial velocity at different nozzle configuration along the axial distribution; (b) spray spatial velocity along the radial distribution for the ID120-01 nozzle; (c) spray spatial velocity along the radial distribution for the ID120-03 nozzle; (d) spray spatial velocity along the radial distribution for the ID120-05 nozzle.
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Table 1. Main parameters of air induction nozzle.
Table 1. Main parameters of air induction nozzle.
Nozzle TypeLiquid Inlet Diameter
Dl/mm		Air Inlet
Diameter
Da/mm		V-Notch
Angle
a/°		Long Axis Diameter of Nozzle Outlet
DL/mm		Short Axis Diameter of Nozzle Outlet
DS/mm
ID120-010.721.41262.100.50
ID120-031.291.54312.980.99
ID120-051.731.96344.121.19
Table 2. Parameters of different experimental conditions.
Table 2. Parameters of different experimental conditions.
Test NumberFlat-Fan
Nozzle		Pressure/
MPa		Flow Rate/
mL·s−1		Concentration/
% v/v		Surface Tension/
N m−1
①ID120-030.112.76 ± 0.4300.07
②ID120-030.112.76 ± 0.430.10.04
③ID120-030.322.00 ± 0.130.10.04
④ID120-030.530.34 ± 0.480.10.04
⑤ID120-010.37.44 ± 0.190.10.04
⑥ID120-050.314.37 ± 0.660.10.04
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MDPI and ACS Style

Yan, M.; Chen, F.; Gong, C.; Kang, C. Experimental Research on the Atomization Characteristics of Air-Induction Spray Based on Oil-Based Emulsion. Agronomy 2025, 15, 936. https://doi.org/10.3390/agronomy15040936

AMA Style

Yan M, Chen F, Gong C, Kang C. Experimental Research on the Atomization Characteristics of Air-Induction Spray Based on Oil-Based Emulsion. Agronomy. 2025; 15(4):936. https://doi.org/10.3390/agronomy15040936

Chicago/Turabian Style

Yan, Mingzhi, Fujun Chen, Chen Gong, and Can Kang. 2025. "Experimental Research on the Atomization Characteristics of Air-Induction Spray Based on Oil-Based Emulsion" Agronomy 15, no. 4: 936. https://doi.org/10.3390/agronomy15040936

APA Style

Yan, M., Chen, F., Gong, C., & Kang, C. (2025). Experimental Research on the Atomization Characteristics of Air-Induction Spray Based on Oil-Based Emulsion. Agronomy, 15(4), 936. https://doi.org/10.3390/agronomy15040936

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