ABSTRACT
Combustion systems are susceptible to thermo-acoustic instabilities, which occur when acoustic pressure oscillations are in phase with the unsteady heat release rates. When grown substantially to large amplitudes, these instabilities cause a serious structural damage, thereby reducing life span of the combustion system. The aim of this work is to utilize a passive control method using Helmholtz resonator with porous inserts to suppress thermo-acoustic instabilities in lean premixed (LPM) combustors to better improve the performance of traditional resonators. In the study, experiments are carried out on a Rijke tube connected to a plenum chamber. A tube with an inner diameter of 80 mm and a length of 800 mm was used for characterization of thermo-acoustic instabilities of the second mode. A liquid petroleum gas (LPG) burner was used as the heat source, and a blower was used to move the air into the system, with a flow rate of 25 lpm. After the characterization, a Helmholtz resonator with a cylindrical cavity was designed for the system and a suitable porous media was selected. Polyurethane foam with 1.45 PCF was selected as the porous material. The results showed a decrease of close to 9% in cavity volume with the help of porous media used along with Helmholtz resonator.
