Numerical simulations of combustion instability in Rijke-Zhao tube

• Main Author: Liu, Xiaoyang.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/51087
• Institution: Nanyang Technological University

In this report, a numerical model is developed to investigate the combustion instability in a Rijke-Zhao tube. This study is carried out in an attempt to better understand the internal coupling among pressure and velocity oscillations and heating element changes. Combustion instabilities or oscillations occur in confined geometries and are caused by the interactions between unsteady heat release and acoustic waves [1-4]. However, instabilities occur if the phase shifts between the pressure and heat flux is less than ±90 degree [5]. For a given combustion system, when the Rayleigh criterion [19] is satisfied, the unsteady heat release rate will be increased by amplified pressure fluctuations, and the oscillation amplitude will grow until it reaches the limit cycle. The mechanisms of instability are numerous, and there is no reliable technique which can express how to predict the occurrence of instability. However, some understanding may be gained on the control mechanisms and characterization of the processed instabilities. Numerical simulation will help to further understand the combustion instabilities. In this project Ansys Fluent 14® was used to numerically simulate the combustion instability in a Rijke-Zhao tube. The project resulted in successfully simulating the combustion instability (limit cycle) in several different design patterns of Rijke-Zhao tubes, and it also contrasted and compared the results for further study.