Diesel Fuel in a Gas Turbine Combustion Chamber, ANSYS Fluent Training

Diesel Fuel Combustion in a Gas Turbine Combustion Chamber Project Description

The problem is simulating the combustion process of diesel fuel inside a combustion chamber of a gas turbine system by ANSYS Fluent software. The function of the combustion chamber is such that the airflow enters the chamber from the space around the chamber and then passes through a diffuser duct with blades, becomes disturbed, and enters the special combustion space in order to better mix with the fuel.

On the other hand, the fuel flow is injected into the space inside the chamber through a nozzle and is mixed with the gas flow, and as a result, the combustion process takes place. The fuel used in this process is diesel (C16H29), which reacts with airflow.

The present model includes a combustion reaction between fuel and air, which is as follows:

According to the above combustion reaction equation, there are four species in the reaction, which include diesel, hydrogen, oxygen, and carbon. Therefore, the Species Transport model has been used to define gaseous species. Also, the volumetric reaction model has been used to define the reaction between these species.

Airflow enters the combustion chamber at a velocity of 3 m.s-1 and a temperature of 300 K, and diesel is sprayed into the interior of the chamber at a velocity of 4 m.s-1 and a temperature of 300 K.

The aim of the present study is to investigate the mass fraction of reactants and combustion reaction products.

Gas Turbine Combustion Chamber Geometry & Mesh

The present 3-D model is designed using Design Modeler software. To simplify the model, only part of the original model (cylinder) is drawn. The air enters the inner part of the chamber through a diffuser duct, including the blade, and the fuel inlet is through the small circular cross-section inside the chamber. The following figure shows a view of the geometry.

The meshing is done using ANSYS Meshing software. The mesh type is unstructured and has 348,8057 cells. The following figure shows a view of the mesh.

CFD Simulation

Several assumptions have been used to simulate the present model:

• The solver is a pressure-based.
• The simulation is steady-state.
• The effect of gravity has been ignored.

A summary of the steps for defining the model is shown in the following table:

Models (diesel fuel)
k-epsilon	Viscous model
standard	k-epsilon model
standard wall function	near-wall treatment
Species transport			Species model
volumetric	reactions
C16H29, O2, CO2, H2O	volumetric species
on			Energy
Boundary conditions (diesel fuel)
Velocity inlet	Inlet type
4 m.s-1	velocity magnitude	air
300 K	temperature
0.23	O2 mass fraction
0	C16H29, CO2, H2O mass fraction
3 m.s-1	velocity magnitude	fuel
300 K	temperature
1	C16H29 mass fraction
0	O2, CO2, H2O mass fraction
Pressure outlet	Outlet type
0 Pa	gauge pressure	outlet
wall			Walls type
stationary wall	wall motion	outer wall
0 W.m-2	heat flux
zero diffusive flux	species boundary condition (C16H29, O2, CO2, H2O)
Solution Methods (diesel fuel)
coupled	Pressure-velocity coupling
second-order	pressure		Spatial discretization
first-order upwind	momentum
first-order upwind	energy
first-order upwind	turbulent kinetic energy
first-order upwind	turbulent dissipation rate
first-order upwind	C16H29
first-order upwind	CO2
first-order upwind	H2O
first-order upwind	O2
Initialization (diesel fuel)
Hybrid	Initialization method

Results

At the end of the solution process, two-dimensional and three-dimensional contours of pressure, temperature, velocity, and mass fraction of diesel, oxygen, carbon dioxide, and water vapor were obtained.

You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.