# Liquid Fuel Combustion Modeling ANSYS Fluent

## Simulation of Liquid Fuel Combustion Using Dispersed Phase Modeling

In this tutorial, we provide guidelines for modeling and simulation of liquid fuel combustion employing the dispersed phase modeling. Using this model, it is possible to simulate the physics of coupled gas flow and liquid spray. In order to simulate the combustion of the vaporized fuel, we use mixture-fraction/PDF (probability density function) equilibrium chemistry model.

### You will also learn how to do the following through this tutorial:

• Modeling a liquid fuel system and creating a PDF file
• Set inputs for probability density function chemistry model
• Define a discrete second phase of evaporating liquid droplets
• Using the pressure-based solver to calculate the flow field. Note: We consider the coupling between discrete liquid fuel droplets and the continuous phase.

### Mixture-fraction/PDF modeling

One advantage of using mixture-fraction/PDF modeling is that it allows us to model non-premixed turbulent combustion by finding the solution of a transport equation for a single conserved scalar. It is also possible to include radicals and intermediate species in our simulations. In addition, using the assumption of equilibrium chemistry, we are able to derive the concentrations of intermediate species from the predicted mixture fraction. Property data for the species is available in the chemical database. We use a β-PDF to model turbulence-chemistry interaction.

### Problem Description of Liquid Fuel Combustion

We model a 2D duct in which air is flowing at 650 K and 1.0 m/s. The Length and height of the duct are 10m and 1m respectively. We also simulate a liquid spray of pentane consisting of 100 micron diameter liquid droplets injected at 300 K over a filled spray half-angle of 30 degrees at the duct centerline. The mass flow rate of liquid fuel is 0.004 kg/s. The duct walls are held at a constant temperature of 1200 K. The Reynolds number based on inlet conditions is approximately 100,000. Therefore, the flow is turbulent. The reaction starts when pentane evaporates and enters the gas phase. We model the combustion using the mixture-fraction/PDF approach, with the equilibrium mixture of chemical species.