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Article

Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets

by
Jing Shi
1,
Changhao Wang
1,*,
Wei Zhang
2 and
Kesheng Meng
2,3,*
1
School of Aviation Maintenance Engineering, Chengdu Aeronautic Polytechnic University, Chengdu 610100, China
2
Department of Aviation and Low-Altitude Economics, Anhui Communications Vocational & Technical College, Hefei 230051, China
3
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230026, China
*
Authors to whom correspondence should be addressed.
Processes 2025, 13(8), 2646; https://doi.org/10.3390/pr13082646
Submission received: 15 July 2025 / Revised: 14 August 2025 / Accepted: 18 August 2025 / Published: 21 August 2025
(This article belongs to the Special Issue Advances in Engineering Thermodynamics and Numerical Simulation)
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Abstract

Under the continuous tightening of global carbon emission policies, the search for sustainable low-emission energy sources is of great significance to reduce the reliance on the use of fossil fuels and to save energy and reduce emissions. Biodiesel–ethanol–graphene mixed fuel has high combustion efficiency and low emission characteristics, and an in-depth study of its evaporation and microexplosion characteristics during the heating process can help to better understand the characteristics of this fuel. In this paper, the evaporation, microexplosion, sub-droplet distribution and kinematic properties of biodiesel–ethanol–graphene droplets under different temperatures, volumes and mixing ratios were investigated by simulating the air atmosphere using a modified tube furnace experimental platform. It was found that the BD50E50 (1%G) droplet produced a weak microexplosion under 600 °C, and three secondary droplets were formed, with the largest secondary droplet area reaching 5.28 mm2. The BD50E50 (1%G) droplet produced strong microexplosion under 800 °C conditions, and 10 secondary droplets were formed, with the largest secondary droplet area of 3.02 mm2. Different intensities of microexplosion and ejection phenomena produced by the biodiesel–ethanol–graphene droplets during the heating process were found, and it was found that the temperature and droplet volume determine whether the microexplosion of the mixed droplets can occur or not, while the intensity of the microexplosion determines the number of secondary droplets and the speed of movement. Additionally, the velocity and acceleration of secondary droplets produced by ejection were significantly greater than those produced by microexplosion. These studies provide a theoretical basis for the application of this fuel.

1. Introduction

According to the World Energy Outlook 2024, the global oil energy consumption in 2024 was about 100 million barrels per day, and this huge energy consumption has increased environmental pollution [1]. Therefore, it is of great significance to find alternative renewable fuels [2,3,4,5,6] with low emissions.
Biodiesel and ethanol can be obtained from corn sugarcane, waste cooking oil [7,8,9,10,11,12,13], etc., and have low emission characteristics, so biodiesel and ethanol are considered as the most promising renewable energy sources. Currently, ethanol fuel is widely used as automotive fuel in countries such as Japan and Brazil, and biodiesel from waste oil is widely used as an alternative aviation fuel in countries such as the United States, Brazil, and China, which has shown great potential application value [14,15,16,17]. The addition of graphene to the fuel can play an important role in reducing the ignition delay and improving the premixed combustion conditions [18]. It has been found that the addition of graphene to the engine fuel can improve the thermal efficiency of the engine and reduce the emissions of hydrocarbons, carbon oxides, nitrogen oxides and other gases [19].
Droplets of mixed fuel with different boiling points will break up rapidly during heating, which is called microexplosion, as shown in Figure 1 [20]. After microexplosion, droplets can form a large number of secondary droplets with different velocities and directions. The movement direction of secondary droplets is related to the surface rupture point of droplets, and the velocity is directly proportional to the vapor pressure inside droplets. By measuring the velocity and acceleration of the droplet, we can study the characteristics of steam pressure and the law of rupture in the droplet. The temperature and the proportion of mixed fuel is a prerequisite for the occurrence of a microexplosion [21,22,23], homogeneous nucleation is the mechanism of the microexplosion of fuels [24,25], and microexplosion intensity is the most interesting research direction for researchers [26,27,28,29,30]. Qiu et al. [30] calculated the microexplosion intensity of biodiesel–ethanol–aluminum powder particle droplets. When the content of aluminum powder is 20%, the microexplosion intensity is maximum. Liu et al. [29] proposed the full life cycle microexplosion intensity of the mixed droplets and analyzed the effect of different intensities of microexplosion on the atomization of fuel.
Due to the role of microexplosions in promoting fuel combustion and reducing emissions, a large number of researchers have conducted detailed studies on microexplosion mechanisms using different fuels [31,32,33]. The addition of graphene to mixed fuels can significantly enhance combustion efficiency and reduce harmful gas and particulate emissions. This not only helps to reduce environmental pollution but also opens up new possibilities for the development of clean energy technologies. For example, the addition of graphene to aluminum powder can significantly improve the explosive intensity of aluminum powder [34], and the addition of graphene to biodiesel–diesel blends can reduce carbon monoxide, carbon dioxide and nitrogen oxide gas emissions by 2–8% [19]. Using biodiesel–graphene fuel in a diesel engine to study the engine performance and emission characteristics, it was found that the addition of graphene increased the thermal efficiency by 2.5% and reduced the emission level of carbon monoxide by 34% [18].
Currently, a large number of scholars have focused on the combustion and emission characterization of biodiesel and its mixed fuels, and few scholars have investigated the combustion and microexplosion characteristics of biodiesel–ethanol–graphene mixed fuels. This paper is a further study on the basis of previous research [20,27]. In a simulated atmospheric environment, the microexplosion and evaporation characteristics of diesel–ethanol–graphene mixed fuel droplets were studied with temperature and graphene concentration as variables, and the concept of volume reduction was put forward to distinguish microexplosion and ejection through quantitative analysis. Meanwhile, the distribution and velocity characteristics of sub-droplets produced by microexplosion with different intensities were deeply studied. These studies could provide a certain theoretical basis for developing sustainable fuels.

2. Materials and Methods

2.1. Selection of Materials

In this experiment, biodiesel, ethanol and graphene were used as the basic energy fuels to study the evaporation of droplets under different temperatures, different volumes and different ratios, in addition to microexplosions and the dynamic characteristics of sub-droplets, whose physicochemical properties are shown in Table 1 and Table 2. Four mixed fuels were formulated for the experiment, BD for biodiesel, E for ethanol and G for graphene particles (Xiamen Xicheng material technology Co., Ltd., Xiamen, China), and their nomenclature is shown in Table 3.

2.2. Experimental Equipment

The experimental platform was improved on the basis of previous studies [39,40,41] by adding a flue gas discharge device, while the focal point position was adjusted in order to further reduce the error. The experimental principle is shown in Figure 2: the experimental platform is mainly composed of a heating system, an exhaust system, a guide rail system and a data acquisition system. The heating system is mainly composed of a vertical combustion furnace, which comes from Yixing Zhongyang Machinery Manufacturing Co., Ltd. in Yixing, China, with an upper limit of 1200 °C, which mainly provides an ambient temperature for the droplets. The exhaust system is mainly composed of an exhaust fan, which mainly excludes the waste gas in the combustion chamber. The guide rail system consists of guide rails and stepping motors to transport the droplets. The data acquisition system consists of a high-speed camera and analysis software to track the droplets and analyze the data.

2.3. Experimental Setups for Observation of Microexplosion

In order to simulate the air atmosphere, the flow meter control panel knob was set to 2.1 L/min for oxygen and 7.9 L/min for the nitrogen cylinder before the experiment, and the experiment was started after waiting for about 5 min. The specific steps can be referred to in previous studies [39].

2.4. Data Analysis

Firstly, the original series of images taken by the high-speed camera were batch cut using Adobe Photoshop. Then, the cut images were binarized, and finally the images were imported into MATLAB (2021) for equivalent circle processing to obtain the droplet normalized diameter; the processing flow is shown in Figure 3 [20]. The area and motion speed of the sub-droplets were analyzed using Image-proplus and the Thousand Eyes Wolf particle image velocimetry system.

3. Results and Discussion

3.1. Evaporation and Microexplosion Mechanism of Mixed Droplets

3.1.1. Evaporation and Microexplosion Characteristics of BD50E50 (G1%) Droplets (“Designated Nomenclature” for BD50E50 (G1%) and Others as in Table 3) During the Suspension Process

The BD50E50 (G1%) droplets produced a weak microexplosion and a strong microexplosion under 600 °C conditions, of which the weak microexplosion was generated in the suspension process and the strong microexplosion was generated in the free-fall process. The weak microexplosion is shown in Figure 4. During the heating process, with the gradual increase in droplet temperature, the irregular thermal motion of ethanol molecules inside the droplet intensified, leading to the continuous aggregation of ethanol molecules and the acceleration of homogeneous nucleation, which in turn created a prerequisite for the microexplosion of BD50E50 (G1%) droplets. When heated to 366 ms, homogeneous nucleation of ethanol vaporization led to the creation of a small bubble inside the droplet, and then the droplet began to expand rapidly. At 390 ms, the droplet generated a weak microexplosion, which produced five secondary droplets. Microexplosion intensity could be defined and calculated by parameters such as microexplosion duration and the number of secondary droplets [40]. Mixed droplets usually underwent several microexplosions during the evaporation process [41]. The vaporization point of ethanol was one of the most important factors determining the intensity of the microexplosion. The closer to the center of the droplet, the higher the pressure inside the bubble, and therefore the higher the intensity of the microexplosion.

3.1.2. Evaporation and Microexplosion Characteristics of BD50E50 (G1%) Droplets During Free Fall

The microexplosion process of a BD50E50 (G1%) droplet during free fall at 600 °C is shown in Figure 5. The evaporation of the free-fall droplet was more in line with the actual engine operation [42], the ethanol vapor inside the bubble of the BD50E50 (G1%) droplet during free fall gradually increased and the droplet volume increased with the increasing pressure inside the bubble. At 411 ms, a bubble appeared below the droplet interior, which was in the form of an irregular long strip, followed by a long strip above the droplet. The upper and lower bubbles started to come together under the pressure inside the bubble, and at 425 ms, the bubbles were completely fused. After the formation of new bubbles, the droplet expanded rapidly, and at 442 ms the droplet produced a high-intensity microexplosion, forming string-like secondary droplet groups. The evaporation area of the droplet increased significantly, and the droplet evaporated rapidly and completely. As can be seen in Figure 5, a secondary droplet produced after the microexplosion of the BD50E50 (G1%) droplet experienced a low-speed expansion stage, a medium-speed expansion stage and a high-speed expansion stage in free fall. At 398 ms–413 ms, there was less ethanol vapor vaporized in the droplet, and the bubble internal pressure was small, so the droplet volume increased slowly. According to the ideal gas state equation, the droplet volume increased with the increase in temperature. Meanwhile, a large amount of ethanol inside the droplet vaporized to form ethanol vapor, and the internal pressure of the droplet increased rapidly, which further led to the increase in the expansion rate of the droplet.

3.2. Effect of Graphene Content on Evaporation and Microexplosion of BD50E50 Droplets

The concentration of solid particles affected the microexplosion intensity and evaporation process of mixed droplets, and the evaporation and microexplosion curve of BD50E50 droplets with different graphene mass concentrations ((a: 0.5%), (b: 1%), (c: 2%), and (d: 5%)) are shown in Figure 6 at 800 °C. As seen in Figure 6, with the increase in graphene content, the color of the droplet in the expansion process gradually deepened, and the normalized diameter of the droplet first increased and then decreased, reaching a maximum of 6.4. The droplet of BD50E50 (G0.5%) experienced two obvious expansions before the microexplosion, and the intensity of the second expansion was 1.14 times that of the first one. Then, the droplet generated the third obvious expansion at 169 ms, and the expansion intensity of the droplet was 1.76 times that of the first one. The droplets produced a strong microexplosion in the interval of 172 ms–179 ms, causing the droplet to split into a large number of sub-droplets, which were distributed in a linear manner. The droplet evaporated completely due to the expansion of the evaporation area and the rapid enhancement of airflow convection. After two expansions, the volume of the BD50E50 (0.5%G) droplet had no obvious change, which indirectly indicated that the droplet produced an ejection phenomenon. Droplet ejection was another physical phenomenon different from microexplosion: droplet ejection was a process in which ethanol vapor inside a droplet was released along the weak part of the droplet surface under the action of internal pressure. After a strong microexplosion, a large number of secondary droplets quickly evaporated, and the normalized diameter decreased by 0.61 compared with that before microexplosion, which is strong evidence that BD50E50 (G0.5%) droplets generated microexplosion during heating. In the process of strong microexplosion, the droplets produced a large number of secondary droplets with a certain initial velocity, which led to the enhancement of convective heat exchange between secondary droplets and hot air, and the overall evaporation area of droplets increased significantly. Therefore, the volume of droplets decreased significantly after strong microexplosion. The BD50E50 (G1%) droplet also experienced two obvious expansions before microexplosion, but the difference was that the expansion intensity was higher than that of the BD50E50 (G0.5%) droplet. Meanwhile, the normalized diameter of the BD50E50 (G1%) droplet before microexplosion reached 6.4, while that of the BD50E50 (G0.5%) droplet before microexplosion was 3.65. The normalized diameter reduction of the BD50E50 (G1%) droplet was 1.34, which was significantly higher than that of the D50E50 (G0.5%) droplet by 0.61. These phenomena indicated that BD50E50 (G1%) droplets produced microexplosions with higher intensity than D50E50 (G0.5%) droplets. A similar phenomenon occurred for the BD50E50 (G2%) droplet and the BD50E50 (G5%) droplet, except that the BD50E50 (G2%) droplets did not produce a microexplosion, while the BD50E50 (G5%) droplets experienced one expansion before microexplosion.

3.3. Effect of Droplet Volume on Evaporation and Microexplosion of BD60E40 (G1%) Droplet

The mixed droplet volume affected the evaporation rate of droplets and microexplosion characteristics. In order to facilitate an intuitive comparison, the evaporation and microexplosion characteristic curves of BD60E40 (G1%) droplets with different volumes at 600 °C were obtained by pairwise comparison, as shown in Figure 7. The droplets of BD60E40 (G1%) with different volumes expanded at different degrees during the heating process. With the increase in volume, the normalized diameter of the BD60E40 (G1%) droplets first increased and then decreased, and the normalized diameter of droplets reached the maximum value of 3.167 when the droplet volume reached 2.0 μL. There was an optimal volume (2.0 microliters in this experiment) for mixed droplets with different proportions, so that the volume expansion value of the mixed droplets could reach the maximum during the heating process at this temperature. This volume was also the optimal volume for microexplosion, and the microexplosion intensity of mixed droplets was the highest at this volume. When the droplet volume of mixed fuel was less than this volume (2.0 microliters), the droplet expansion rate gradually decreased with the decrease in droplet volume, because the smaller the droplet volume, the faster the heat conduction and the faster the droplet surface evaporation. Meanwhile, due to the small volume of droplets, the content of low-boiling components in the droplets was low. Therefore, the smaller the expansion rate of the droplets, the weaker the microexplosion intensity of the droplets. When the volume of the mixed fuel was larger than this volume (2.0 microliters), with the increase in droplet volume, the expansion rate of the droplets also decreased gradually, which was mainly because the homogeneous nucleation rate of the same component in the droplets was slow, the ethanol vapor in the droplets constantly pushed bubbles to the edge of the droplets and ruptured them under the action of internal liquid pressure and the microexplosion intensity also decreased gradually.

3.4. Effect of Temperature on Evaporation and Microexplosion of BD50E50 (G1%) Droplet

Temperature was an important condition to promote the homogeneous nucleation of the same components in mixed droplets during heating. The higher the temperature, the faster the rate of homogeneous nucleation. The evaporation and microexplosion curves of the BD50E50 (1%G) droplets under 600 °C, 700 °C and 800 °C were obtained by pairwise comparison, as shown in Figure 8. With the increase in temperature, the normalized diameter of the BD50E50 (1%G) droplet gradually increased, and the droplet reached the maximum value of 6.43 at 800 °C. The BD50E50 (1%G) droplet appeared to expand at 600 °C, but there was no microexplosion phenomenon. This was mainly due to the slow formation rate of ethanol vapor inside the droplet, and the bubbles inside the droplet moved to the edge of the droplet under the action of uneven internal pressure during the expansion process; finally, the internal vapor was released at the edge of the droplet. The BD50E50 (G1%) droplets under 700 °C and 800 °C produced a more significant expansion. The normalized diameter of the droplets was 3.657 at 700 °C and 6.43 at 800 °C. It can be seen from Figure 8 that transparency of the droplet was more uniform at 800 °C, indicating that the liquid layer of the droplet was more uniform, the pressure in the bubble was greater and the microexplosion was stronger during the expansion process. The BD50E50 (G1%) droplet produced a strong microexplosion after expansion, and the droplet was torn by the internal vapor pressure into a number of several sub-droplets of varying volume. In a certain range, the higher the temperature (the experimental temperatures in this study were 600 °C, 700 °C and 800 °C), the faster the vaporization rate of low-boiling components inside the droplet, and the more nucleation sites inside the droplet, resulting in a more balanced internal force of a large number of droplets and a slower bubble movement rate. This not only provided important conditions for the expansion of the droplet but also significantly improved the pressure inside the droplet, thus forming a microexplosion with higher intensity.

3.5. The Sub-Droplet of BD50E50 (G1%) Area and Distribution Characteristics

Mixed droplets can produce different numbers and volumes of sub-droplets during microexplosion or ejection. The greater the microexplosion intensity of droplets, the more sub-droplets, the more completely destroyed droplets and the faster the evaporation rate of droplets. The number and area of sub-droplets when the BD50E50 (1%G) droplets generated a weak microexplosion and strong microexplosion at 600 °C and 800 °C, respectively, are shown in Figure 9. The BD50E50 (1%G) droplets at 600 °C produced a weak microexplosion, forming three sub-droplets with the maximum area of 5.28 mm2. The BD50E50 (1%G) droplets at 800 °C produced a strong microexplosion, forming 10 sub-droplets, with the largest secondary droplet area of 3.02 mm2. The higher the ambient temperature, the faster the vaporization speed of low-boiling components inside the droplet, the higher the internal pressure of the droplet, the higher the intensity of the microexplosion generated by the droplet and the more sub-droplets generated by the microexplosion [20,26,27]. The mixed droplets produced a large number of sub-droplets with different volumes in the process of microexplosion, resulting in a significant increase in the evaporation area of the droplets, further promoting the evaporation and combustion of droplets and significantly improving the combustion efficiency of fuel.

3.6. Dynamic Characteristics of Sub-Droplets

The mixed droplets could produce sub-droplets by both microexplosion and the ejection of droplets during heating, but the dynamic characteristics of the sub-droplets produced by the different phenomena were significantly different. The sub-droplet dynamic characteristics of a BD50E50 (1%G) droplet with a volume of 2.0 microliters and a BD60E40 (1%G) droplet with a volume of 1.5 microliters at 600 °C are shown in Figure 10. The maximum velocity of three sub-droplets produced by microexplosion was 17.0 mm/s, and the minimum velocity of sub-droplets produced by ejection was 305.5 mm/s. Moreover, the velocity and acceleration of sub-droplets produced by ejection were significantly higher than those produced by microexplosion. In the process of microexplosion, the vapor inside the droplet was released along the spherical surface, and a plurality of vapor release points was formed on the spherical surface. In the process of ejection formation, the ethanol vapor inside the droplet was ejected along a fixed point on the spherical surface. Therefore, the vapor pressure and time acting on the sub-droplets during microexplosion were significantly less than those acting on the sub-droplets during ejection formation. The acceleration of three sub-droplets moving in different directions formed in the process of microexplosion was much lower than that of gravity and remained basically constant, indicating that the airflow generated by microexplosion had a significant impact on the surrounding environment, which may be the continuous effect of shock waves generated by microexplosion on droplets.

4. Conclusions

In this paper, the microexplosions of biodiesel–ethanol–graphene mixed fuel droplets and the dynamic characteristics of sub-droplets were investigated, which had certain reference significance for developing alternative fuels. The main research contents are as follows:
  • The BD50E50 (1%G) droplets produced a weak microexplosion during suspension and a strong microexplosion during free fall. In the process of the strong microexplosion, the droplet volume experienced three different rates of expansion. The microexplosion intensity was positively correlated with the number of sub-droplets and the evaporation rate. The higher the microexplosion intensity, the faster the droplet evaporation.
  • The mixed droplets may occur several times ejection before microexplosion. Microexplosion could significantly reduce the droplet volume, but the contribution of ejection phenomenon to reducing the droplet volume was limited. The graphene content affected the microexplosion intensity of droplets, and BD50E50 (G1%) had the highest microexplosion intensity. Before microexplosion, the normalized diameter of droplets had reached 6.4, and the reduction in the normalized diameter was 1.34.
  • There was an optimal volume droplet (the volume of this experiment was 2.0 microliters) in the different proportions of mixed droplets, and the volume expansion rate and microexplosion intensity reached the maximum value during heating. When the volume of mixed droplets was less than or greater than this volume, both the droplet expansion rate and microexplosion intensity showed a decreasing trend.
  • An appropriate temperature and droplet size were prerequisites for the microexplosion of mixed droplets. In a certain range, the higher the temperature, the faster the vaporization rate of low-boiling components in droplets, and the more nucleation sites in droplets, the higher the microexplosion intensity.
  • In the process of microexplosion, the vapor inside the droplet was released along the spherical surface, and a plurality of vapor release points was formed on the spherical surface. In the process of ejection formation, the ethanol vapor inside the droplet was ejected along a fixed point on the spherical surface, so the vapor pressure and time acting on the secondary droplet during microexplosion were significantly less than those acting on the secondary droplet during ejection formation. Therefore, the velocity and acceleration of secondary droplets produced by ejection are significantly higher than those produced by microexplosion.
Future research can aim for different oxygen conditions at the same time to analyze the effect of different microexplosion intensities on emissions, which will be very meaningful; this is the goal of our next work.

Author Contributions

J.S.: Conceptualization, Methodology, Software, Investigation, Formal Analysis, Writing—Original Draft; C.W.: Data Curation, Writing—Original Draft; W.Z.: Visualization, Investigation; K.M.: Resources, Supervision, Software. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by the Natural Science Major Project in Anhui Province (Kesheng Meng No. 2022AH040314) and Research on energy management strategy of compound wing unmanned oil-electric hybrid power system (No. ZZX0624098).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author(s).

Conflicts of Interest

The authors declare that they have no conflicts of interest.

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Figure 1. Microexplosions during droplet heating and their classification.
Figure 1. Microexplosions during droplet heating and their classification.
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Figure 2. Schematic of the experimental setup.
Figure 2. Schematic of the experimental setup.
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Figure 3. Treatment process of droplet diameter.
Figure 3. Treatment process of droplet diameter.
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Figure 4. The weak microexplosion process of BD50E50 (G1%) droplet at 600 °C.
Figure 4. The weak microexplosion process of BD50E50 (G1%) droplet at 600 °C.
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Figure 5. The Strong microexplosion process of BD50E50 (1%G) droplets under 600 °C.
Figure 5. The Strong microexplosion process of BD50E50 (1%G) droplets under 600 °C.
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Figure 6. Evaporation and microexplosion curves of BD50E50 droplets with different graphene mass concentrations ((a): 0.5%, (b): 1%, (c): 2%, and (d): 5%)) at 800 °C.
Figure 6. Evaporation and microexplosion curves of BD50E50 droplets with different graphene mass concentrations ((a): 0.5%, (b): 1%, (c): 2%, and (d): 5%)) at 800 °C.
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Figure 7. Evaporation and microexplosion curves of BD50E50 droplets of different volumes ((a): 1.0 μL and 1.5 μL, (b): 1.5 μL and 2.0 μL, (c): 2.0 μL and 2.5 μL, and (d): 2.5 μL and 3.0 μL)) at 600 °C.
Figure 7. Evaporation and microexplosion curves of BD50E50 droplets of different volumes ((a): 1.0 μL and 1.5 μL, (b): 1.5 μL and 2.0 μL, (c): 2.0 μL and 2.5 μL, and (d): 2.5 μL and 3.0 μL)) at 600 °C.
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Figure 8. Evaporation and microexplosion curves of BD50E50 (1%G) droplets at 600 °C, 700 °C and 800 °C.
Figure 8. Evaporation and microexplosion curves of BD50E50 (1%G) droplets at 600 °C, 700 °C and 800 °C.
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Figure 9. Number and area of sub-droplets of BD50E50 (1%G) droplets in weak and strong microexplosion under 600 °C and 800 °C.
Figure 9. Number and area of sub-droplets of BD50E50 (1%G) droplets in weak and strong microexplosion under 600 °C and 800 °C.
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Figure 10. The sub-droplet dynamic characteristics of a BD50E50 (G1%) droplet (a) with a volume of 2.0 μL and a BD60E40 (G1%) droplet (b) with a volume of 1.5 μL at 600 °C.
Figure 10. The sub-droplet dynamic characteristics of a BD50E50 (G1%) droplet (a) with a volume of 2.0 μL and a BD60E40 (G1%) droplet (b) with a volume of 1.5 μL at 600 °C.
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Table 1. Physical properties of fuels [35,36].
Table 1. Physical properties of fuels [35,36].
PropertiesBiodieselEthanol
Molecular formulaR-COO-RC2H5OH
Density(kg/m3)881789
Boiling point(°C)315–35778.4
Flash point(°C)13013
Surface tension (mN/m)29.321.97
Viscosity (20 °C)/(mm2/s)4.321.21
Table 2. Thermal conductivity of graphene and chemically modified graphene.
Table 2. Thermal conductivity of graphene and chemically modified graphene.
Types of GrapheneThermal ConductivityUnits
Single-layer graphene [37]5300 ± 480W·m−1·K−1
4 layers of graphene [38]1100W·m−1·K−1
2-layer graphene [38]970W·m−1·K−1
Table 3. Composition and nomenclature of 4 kinds of mixed fuel.
Table 3. Composition and nomenclature of 4 kinds of mixed fuel.
Composition of Fuel Mixture of Biodiesel and Ethanol (Volume Basis)Graphene
(Mass Ratio)		Designated Nomenclature
50%BD, 50%ethanol0.5%BD50E50 (G0.5%)
50%BD, 50%ethanol1.0%BD50E50 (G1%)
50%BD, 50%ethanol2.0%BD50E50 (G2%)
50%BD, 50%ethanol5.0%BD50E50 (G5%)
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Shi, J.; Wang, C.; Zhang, W.; Meng, K. Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets. Processes 2025, 13, 2646. https://doi.org/10.3390/pr13082646

AMA Style

Shi J, Wang C, Zhang W, Meng K. Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets. Processes. 2025; 13(8):2646. https://doi.org/10.3390/pr13082646

Chicago/Turabian Style

Shi, Jing, Changhao Wang, Wei Zhang, and Kesheng Meng. 2025. "Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets" Processes 13, no. 8: 2646. https://doi.org/10.3390/pr13082646

APA Style

Shi, J., Wang, C., Zhang, W., & Meng, K. (2025). Effects of Biodiesel–Ethanol–Graphene Droplet Volume and Graphene Content on Microexplosion: Distribution, Velocity and Acceleration of Secondary Droplets. Processes, 13(8), 2646. https://doi.org/10.3390/pr13082646

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