Combustion simulation of gas diffusion mixing

• Main Author: Chee, Yin Yong.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Aeronautical engineering::Aircraft motors and engines; DRNTU::Engineering::Aeronautical engineering::Jet propulsion
• Online Access: http://hdl.handle.net/10356/46144
• Institution: Nanyang Technological University

Numerical simulation of combustion processes has become a viable means in many modern engine designs, with advantages such as lower costs and higher efficiency. However, numerical methods are greatly limited by the physics and mathematics of the governing equations. The solutions yield may be totally different from the realistic problem if there is a lack of understanding on the limitations of the models used. This project will study the gas diffusion mixing modelling process and investigate on the widely used k-ε turbulence models, the Eddy Dissipation model and the Mixture Fraction Theory approach. Two different cases of Jet Flame, Hydrogen and Methane flame, are studied and modelled in FLUENT 6.3. Parameter studies on the model constants, the turbulent Prandtl and Schmidt number are conducted using these cases. This study has shown how combustion process is greatly affected by both the turbulence and chemistry of the flow problem. Governing equations of different turbulence and combustion models are limited in describing different flow and flame problems. The violation of the assumptions used in the models would greatly affect the accuracy of the results. Thus it is important to understand and check for the validity of these assumptions and limitations. Also, the various default empirical constants used may not be the optimal values in obtaining the most accurate solution. This project would demonstrate how with the understanding on the effects of the various parameters have on the numerical solution, a more accurate result can be achieved. Nevertheless, the process of mesh generation and model setup in the solver program is equally important in combustion modelling. Grid convergence tests and wall y+ values are some checks and indicators that can be done to ensure a more accurate numerical solution.