Combustion Inside the Boiler, Ansys Fluent CFD Simulation Training

Description

Combustion Inside the Boiler Project Description

The present simulation is about the combustion inside a boiler via ANSYS Fluent. Boilers are pressurized tanks that carry out the boiling or heating fluid. Boiling is a process that brings the temperature of a fluid to the boiling point. Therefore, the combustion reaction must occur inside these boilers. The combustion reaction occurs in the computational zone of the boiler, and the desired species are defined using the species transport model. Nine different species are defined to define the combustion reaction, and five combustion reactions between these species are defined as volumetric. The current boiler consists of two different inputs, airflow inlet, and fuel flow inlet. Airflow with the temperature of 303.15 K and mass flow rate of 3.375 kg.s^-1 enters from the side of the boiler, and a combination of several different fuels with the temperature of 300 K and mass flow rate of 0.6135 kg.s^-1 enters from the narrow pipes of the lower part of the boiler.

Geometry & Mesh

The present model is designed in 3D via SpaceClaim. The boiler is designed so that airflow enters from the side panel of the boiler, and a combination of fuel flows enter through the narrow pipes of the lower part of the boiler, and the boiler outlet is related to the upper pipe of the boiler.

The mesh of the present model has been done via ANSYS Meshing. Mesh is done unstructured, and the number of cells equals 4694637. Figure 2 shows the mesh of the model.

Set-Up & Solution

Assumptions used in this simulation  :

• Pressure-based solver is used.
• The present simulation is steady.
• The effect of gravity is ignored.

 

Models
Viscous		k-epsilon
	k-epsilon model	realizable
	near-wall treatment	standard wall function
Species Model		Species Transport
	number of volumetric species	9 (C4H10, iC4H10, C3H4, C2H4 , Ch4, O2, CO2, H2O, N2)
	reactions	volumetric
Energy		On
Boundary conditions
Inlet – Air		Mass Flow Inlet
	mass flow rate	3.375 kg.s-1
	temperature	303.15 K
	O2 mass fraction	0.21
	N2 mass fraction	0.79
	other species mass fraction	0
Inlet – Pipe		Mass Flow Inlet
	mass flow rate	0.6135 kg.s-1
	temperature	300 K
	CH4 mass fraction	0.704
	C3H4 mass fraction	0.074
	C2H4 mass fraction	0.035
	iC4H10 mass fraction	0.063
	C4H10 mass fraction	0.025
	other species mass fraction	0
Outlet		Pressure Outlet
	gauge pressure	0 pascal
Outer Walls		Wall
	wall motion	wall motion
	heat flux	0 W.m-2
Inner Walls		Wall
	wall motion	stationary wall
	thermal conditions	coupled
Methods
Pressure-Velocity Coupling		Coupled
	pressure	second-order
	momentum	second-order upwind
	turbulent kinetic energy	second-order upwind
	turbulent dissipation rate	second-order upwind
	energy	second-order upwind
	species mass fraction	second-order upwind
Initialization
Initialization methods		Standard
	gauge pressure	0 pascal
	x-velocity	1.573 m.s-1
	y-velocity & z-velocity	0 m.s-1
	temperature	303.15 K
	O2 mass fraction	0.21
	other species mass fraction	0

Combustion Inside the Boiler Results

After solution, 2D and 3D contours related to each defined species’ temperature, velocity, and mass fraction, including oxygen, carbon dioxide, water vapor, CH₄, C₂H₄, C₃H₄, and C₄H_10, are obtained. The contours show that after combining carbohydrates with oxygen, a combustion reaction occurs, and, as a result, the boiler interior temperature rises. Also, as the combustion reaction begins, carbohydrates and oxidants decrease at the boiler inlet, and in turn, carbon dioxide and vapor are produced as reaction products, and their amount increases. The results are shown in Figures.

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