• acoustic
• CFD
• combustion chamber
• combustor
• entropy
• lean burn
• Rolls-Royce
• rumble
• thermoacoustic

New combustion methods, aimed to reduce emissions, are shown to be susceptible to instability. To reduce nitrogen oxides, the traditional diffusion flame is replaced by lean combustion, where fuel-air are partially premixed, and combustion conditions are set to keep the flame temperature cooler, producing the minimum amount of NOx. However they are more sensitive to unsteady combustion that generates acoustic waves which alter the mixture fraction; at a certain conditions the self-excited oscillations may grow showing the rumble phenomena.
This work has been carried on in Rolls-Royce plc, in Combustion & Casings department, while a six month internship by Aerothermal Methods team.
The task is aimed to improve the acoustic in-house program, coming to a new entropy convection model for rumble prediction.