# Analysis of Flame Evolution Generated from Methyl Laurate Droplet Using Deep Learning
## 2 Materials and Methods
### Droplet Combustion Testing  
The experiment was carried out under normal gravity, at atmospheric pressure, and at room temperature. The droplet combustion test chamber was a rectangular chamber that was isolated from the influence of ambient airflow during the test. The fuel undergoing the droplet combustion test was placed on a temperature-measuring sensor in the form of a junction thermocouple, which also functioned as a droplet buffer. The thermocouple used was a type R thermocouple (Pt\(-\)Pt/Rh wire) with a diameter of 0.1 mm. The combustion \begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Methyl Laurate** & **Diesel** \\ \hline Molecular formula & C\({}_{13}\)H\({}_{26}\)O\({}_{2}\) & C\({}_{10}\)-C\({}_{15}\) \\  & & (hydrocarbons) \\ Oxygen content (wt\%) & 14.9 & \textless{}1 \\ Molecular weight (gr/mol) & 214.34 & 150 to 250 \\ Higher heating value (MJ/kg) & 37.22 & 42 to 46 \\ Boiling point (\({}^{\circ}\)C) & 262 & 150 to 380 \\ Melting point (\({}^{\circ}\)C) & 5 & \textasci{}30 to \textasci{}18\) \\ Flash point (\({}^{\circ}\)C) & 139 & 52 to 96 \\ Density (gr/cm\({}^{3}\)) & 0.869 (at 15 \({}^{\circ}\)C) & 0.8375 (at 15 \({}^{\circ}\)C) \\ Kinematic viscosity (mm\({}^{2}\)/s) & 2.40 (at 40 \({}^{\circ}\)C) & 2.0–4.1 (at 40 \({}^{\circ}\)C) \\ Cetane number & 61.99 & 45 to 55 \\ Sulfur content (ppm) & \textless{}10 & \textless{}15 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical and physical properties of methyl laurate and diesel fuel [5; 31; 32; 33; 34; 35; 36]. process, starting with heating the droplets using a heater coil until the flame went out, was recorded using a Nikon D5300 camera with an AF-S Mikro-Nikkor 40 mm f/2.8D macro lens. The video recording had a shooting rate of 60 fps. The droplet temperature during the droplet heating and combustion process was measured using a type R thermocouple (200 \(\upmu\)m diameter of 13%Pt-Rh wire, The Nilaco Corp., Tokyo, Japan) connected to an Advantech USB-4718 data logger, which was linked to a computer for data acquisition. The data logger and computer recorded droplet temperature data during the combustion process with a sampling rate of 10 Hz (100 ms) and a maximum error of \(\pm\)2.5 \({}^{\circ}\)C in comma-separated value (csv) format files. The technique used to capture video footage of the droplet combustion test employed the self-illuminated direct imaging method, similar to several prior studies [22; 37]. In this research, the burning of methyl laurate droplets was observed with two types of video capture variations, namely backlight and flame. When taking backlight videos, the camera focuses on the droplets with additional light from behind. The purpose of taking a video with a backlight is so that the process of the droplet burning out can be observed perfectly without being influenced by the light from the fire. When taking a flame video, the aim is to observe the flame evolution from start to finish. In addition, the temperature during the combustion process was also monitored using a type R thermocouple. Data collection was carried out using the research installation, as shown in Figure 1.  
The droplet combustion test utilized the suspended droplet method in conjunction with an isolated single droplet combustion technique. In this setup, a fuel droplet is created at the tip of an R-type thermocouple. In the droplet combustion test, the heating phase begins either when the wire temperature stabilizes or 6.5 s after the power supply is activated. Droplets with a volume of 3.05 \(\upmu\)L were created using 10 \(\upmu\)L of liquid fuel and a microsyringe to achieve a diameter of 1.82 \(\pm\) 0.05 mm. Data collection began by heating the droplet using a heater coil, which was connected to a power supply. The droplets were heated by a heater positioned 3 mm above them, maintaining a temperature of 720 \({}^{\circ}\)C. This process occurred simultaneously with video recording using a Nikon D5300 camera, while the data logger was activated to capture temperature data throughout the combustion process.