CFD SIMULATION OF HYDROGEN

COMBUSTION

INTRODUCTION

Hydrogen as alternative fuel

Evaluation of Hydrogen combustion using CFD

OBJECTIVES AND SCOPEUnderstanding of the basics of Hydrogen-

oxygen reaction mechanism.To develop a two dimensional numerical

mesh and flow model.To prepare a mathematical model for

hydrogen-air combustion system.The objective of this is to study CFD-

package FLUENT.

HYDROGEN AS A FUEL It readily combines with oxygen to form

water.It has a high-energy content per weight. Hydrogen is highly flammable.Hydrogen burns with a pale-blue, almost-

invisible flame.The combustion of hydrogen does not

produce carbon dioxide (CO2), particulate, or sulfur emissions.

Hydrogen can be produced from renewable resources.

Table : Properties of fuels

PROPERTIES OF HYDROGEN AS A FUEL Limits of FlammabilityMinimum Ignition EnergyQuenching Gap or Distance Self Ignition Temperature Flame SpeedDiffusivityDensityFlame characteristics 

Figure : Invisible Hydrogen Flame Igniting Broom 

Figure : Hydrogen Flame from Ruptured Fuel Cylinder

 

BENEFITS OF HYDROGEN ECONOMY Strengthen National Energy Security Reduce Greenhouse Gas Emissions Reduce Air Pollution Improve Energy Efficiency

HYDROGEN STORAGE AND DELIVERY Compressed Gas and Cryogenic Liquid

StorageMaterials-based Hydrogen StorageCurrent Technology

COMBUSTION

Combustion accounts for approximately 85% of the worlds energy usage.

Eg: Gas turbine and jet engine. Rocket propulsion. Piston engines.Combustion is a complex interaction of

physical and chemical processes.

The general characteristics of combustion:The first and second limits are ones that

correspond to conditions of very low pressures .

As the pressure increases, the initial densities of the reactants increase and a lower temperature is necessary for the reactions to become fast enough for explosion.

Hydrogen Combustion 

GRID GENERATION AND MATHEMATICAL MODELING Model geometry

Grid Generation

MATHEMATICAL MODELLING

  Continuity Equation

Momentum Equations

Boundary conditions •Inlet temperature of hydrogen and air

=300 k•velocity 90 m/s •Exit a pressure =101325.0 Pa

CFD SIMULATION A number of numerical simulations have

been performed to study the combustion phenomena under adiabatic wall conditions when hydrogen air mixture changes from lean to rich and also at different mass flow rate of mixture. Figure. shows the contours of temperature (K) on the cross section along central axis of combustion chamber at stoichiometric air fuel ratio i.e. at Ф=1.

Figure : Temperature Contours at Ф=1  

Figure : Contours of Mole fraction of h2O  

Figure : Contours of Mole fraction of N2

Figure : Contours of Mole fraction of O2

Figure : Contours of Mole fraction of H2

Figure : Contours of Mole fraction of OH

Figure : Contours of Mole fraction of O

CONCLUSION•CFD based combustion simulations have

been done.•The combustor performance is evaluated

by predicting the temperatures of exit gas of the combustor and outer wall of the combustor.