CFD study of dynamic response of a diffusion flame of methane to standing waves in a longitudinal tube
Tay, Koong Jye
Date of Issue2016-05-16
School of Mechanical and Aerospace Engineering
In this report, Computational Fluid Dynamics (CFD) was utilized to study the dynamic response of a methane-fueled diffusion flame to standing waves in a longitudinal tube. Since the operation of combustion engines is a loud and noisy process, there is definitely a large degree of interaction between the flame and acoustic waves within the combustor. Research was done and it was revealed to the author that this interaction is able to cause acoustic combustion instabilities that might lower the efficiency of the combustor. Thus, a CFD simulation was conducted in this study whereby a diffusion flame of methane is exposed to acoustic standing waves in a longitudinal tube so as to simulate a situation within an operating combustor. Three key simulations were carried out where different parameters were changed so as to investigate the changes in the flame dynamics. The three parameters are namely; axial location of the fuel nozzle, frequency and amplitude of the standing wave applied. The results revealed that the axial location of the fuel nozzle have significant effects on the dynamics of the flame. An interesting mushroom-shaped flame front was even observed. By changing the frequency of the sound waves, different observations were drawn with respect to factors such as axial velocity, pressure and heat release. A variation in the magnitudes of gain and phase difference were seen when the amplitude of the sound wave was changed. A comparison of results was then done with another study which used propane instead of methane. This study also includes how selected variables vary in the radial direction of the tube in a single time period of oscillation. Another comparison was then done to assess if the fuel nozzle’s axial location, frequency and amplitude of standing wave applied had any effect on the variation of those variables in the radial direction.
Final Year Project (FYP)
Nanyang Technological University