Non-premixed combustion with fuel droplet injection simulation provides a thorough grasp of the complex processes that influence combustion dynamics. This simulation illuminates critical phenomena such as evaporation, mixing, and chemical reactions by carefully modeling the interaction of fuel droplets with the surrounding air. The non-premixed nature emphasizes the lack of pre-mixing of fuel and oxidizer before ignition, which is common in many real combustion systems. Given the importance of simulating such fuel droplets, non-premixed combustion in a combustion chamber is simulated in this project using ANSYS Fluent software. The fuel is pentane modeled as liquid droplets.

Figure 1: C5H12 combustion inside the chamber using DPM

Simulation Process

The 2D geometry is simple to draw. Due to the symmetric feature of the combustion chamber, only half of it is modeled. Next, a structured grid is generated, giving 5200 cells. The solver requires several main steps to simulate the reaction of pentane considering fuel droplets. Non-premixed combustion and  Species Transport models are used. As a result, a PDF is established to summarize the properties of the combustion. Moreover, Discrete Phase Model (DPM) is employed to model fuel droplets. A two-way DPM method considers interactions between the discrete and continuous phases. The particle`s type of Droplets is utilized.

Post-Processing

The temperature contour tells an intriguing story of the combustion process, showing how the heat develops and spreads throughout the chamber. Near the entrance where the fuel droplets first meet the oxidizer, we see temperatures soaring up to an impressive 2280K (about 2007°C), marked by the bright yellow regions. This intense heat zone is where the magic of combustion really happens – the pentane droplets are rapidly evaporating and reacting with the surrounding air. As we move downstream, the temperature gradually decreases but maintains a consistent pattern, showing how effectively the heat is distributed through the chamber.

Figure 2: a) Temperature b) Velocity pattern inside the combustion chamber due to fuel droplets injection

What’s particularly interesting is the formation of various chemical species during this process. Looking at the mass fraction contours, we can track how water vapor (H2O) is produced, with concentrations reaching up to 7.56e-02 at their peak. The distribution pattern shows a clear correlation with the high-temperature zones, which makes perfect sense – these are the areas where our pentane droplets are most actively burning and converting into products. The DPM (Discrete Phase Model) really shines here, letting us see how the liquid fuel droplets transform through evaporation, mix with the oxidizer, and ultimately react to create these combustion products. The symmetrical nature of these patterns validates our decision to model just half of the chamber, as the behavior mirrors perfectly across the centerline.

Figure 3: a) H2o Mass fraction b) DPM evaporation rate in Non-premixed Combustion