CFD SIMULATION OF HYDROGEN COMBUSTION

1. CFD SIMULATION OF HYDROGEN COMBUSTION

2. INTRODUCTION • Hydrogen as alternative fuel • Evaluation of Hydrogen combustion using CFD

3. OBJECTIVES AND SCOPE • Understanding 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.

4. 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.

5. Hydrogen can be produced from renewable resources.

6. Table : Properties of fuels

7. PROPERTIES OF HYDROGEN AS A FUEL • Limits of Flammability • Minimum Ignition Energy • Quenching Gap or Distance •  Self Ignition Temperature •  Flame Speed • Diffusivity • Density • Flame characteristics 

8. Figure : Invisible Hydrogen Flame Igniting Broom

9. Figure : Hydrogen Flame from Ruptured Fuel Cylinder

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

11. HYDROGEN STORAGE AND DELIVERY • Compressed Gas and Cryogenic Liquid Storage • Materials-based Hydrogen Storage • Current Technology

12. 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.

13. 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.

14. Hydrogen Combustion

15. GRID GENERATION AND MATHEMATICAL MODELINGModel geometry

16. Grid Generation

17. MATHEMATICAL MODELLINGContinuity Equation

18. Momentum Equations

19. Boundary conditions • Inlet temperature of hydrogen and air =300 k • velocity 90 m/s • Exit a pressure =101325.0 Pa

20. 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.

21. Figure : Temperature Contours at Ф=1

22. Figure : Contours of Mole fraction of h2O

23. Figure : Contours of Mole fraction of N2

24. Figure : Contours of Mole fraction of O2

25. Figure : Contours of Mole fraction of H2

26. Figure : Contours of Mole fraction of OH

27. Figure : Contours of Mole fraction of O

28. 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.