Gas Turbine Combustion Chamber (2-D), ANSYS Fluent CFD Simulation Training

Gas turbine introduction

A gas turbine is a rotating machine that operates on the energy of combustion gases. Each gas turbine includes a compressor to compress the air, a combustion chamber to mix the air with the fuel and ignite this mixture, and a turbine to convert the energy of hot and compressed gases into mechanical energy. Part of the mechanical energy produced in the turbine is spent on turning the compressor itself, and the rest of the energy, depending on the application of the gas turbine, may spin the generator (turbo-generator), accelerate the air (turbojet and turbofan) or be used in other applications.

The fuel system in gas turbines is constantly changing and engineers and designers in the field of mechanical engineering have tried to improve this important part in gas turbines. The use of gas turbine injectors in the fueling section of gas turbines is one of the most important and at the same time efficient methods in this field.

Project description

In this project, methane-air fuel mixture combustion inside a gas turbine combustion chamber is simulated by ANSYS Fluent software. Methane and oxygen are injected inside the combustion chamber with the velocity of 128.9304m/s and 12.0396m/s and the temperature of 286K and 109K, respectively. The fuel mixture is then ignited and energy and heat are generated. Energy model is activated. Also, the species transport model is used to analyze the combustion process.

Eddy-Dissipation method has been used to investigate the chemical-turbulent interaction of combustion reactants and the standard k-ε viscosity model with the use of standard wall functions is exploited to solve the fluid flow. The real gas equation has also been used to determine the water vapor’s density changes due to changes in temperature

Gas Turbine Geometry and Mesh

The geometry required for this analysis, which includes only the gas turbine injector part, is designed in ANSYS Design Modeler® and mesh inside ANSYS Meshing®. The mesh type used for this geometry is structured and the element number is 197006.

CFD Simulation Settings

The key assumptions considered in this project are:

• Simulation is done using density based solver.
• The present simulation and its results are considered to be steady and do not change as a function time.
• The effect of gravity has not been taken into account.

The applied settings are summarized in the following table.

(gas turbine)	Models
Viscous model		k-epsilon
	k-epsilon model	standard
	near wall treatment	standard wall function
Energy		on
Species		Species transport
	Reactions	Volumetric
	Chemistry solver	None-explicit source
	Mixture material	Methane-air
	Turbulence chemistry interaction	Eddy-dissipation
(gas turbine)	Boundary conditions
Inlet		velocity inlet
Oxygen inlet	Velocity magnitude	12.0396 m/s
	Turbulent intensity	1 %
	Hydraulic diameter	0.005715m
	Temperature	109 K
	Species (mass fraction)	O2 à 1
Methane inlet	Velocity magnitude	128.9304 m/s
	Turbulent intensity	1 %
	Hydraulic diameter	0.0012192 m
	Thermal	286 K
	Species (mass fraction)	CH4 = 1
Outlet		Pressure outlet
	Gauge pressure	0 Pa
(gas turbine)	Turbulent intensity	5 %
	Hydraulic diameter	0.012 m
	Temperature	286 K
Walls
ISO-thermal wall	wall motion	stationary wall
	Wall temperature	286 K
	Species (boundary condition)	Zero diffusive flux
Adiabatic and rocket walls	wall motion	stationary wall
	Heat flux	0 W/m2
	Species (boundary condition)	Zero diffusive flux
(gas turbine)	Solution Methods
Formulation		Implicit
Flux-type		Roe-FDS
Spatial discretization	Flow	second order upwind
	turbulent kinetic energy	second order upwind
	turbulent dissipation rate	second order upwind
(gas turbine)	Initialization
Initialization method		Standard
	gauge pressure	0 Pa
	Axial velocity	52.48457 m/s
	Radial velocity	0 m/s
	temperature	200 K
	Turbulent kinetic energy	0.8769719 m2/s2
	Turbulent dissipation rate	2623.847 m2/s3
	CH4	0.3460065
	O2	0.6539935
	Other species	0

Results

Contours of density, pressure, temperature, velocity and species mass fractions are presented.

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