Suppression of thermo-acoustic instabilities in horizontal Rijke tube using pulsating radial jets.

Thermo-acoustic instability has been observed in gas turbines, rocket engines, and aero-engines. Acoustic perturbations grow and change the characteristics of the flow due to instability. The present work describes the use of pulsating air jets to suppress the thermo-acoustic instabilities. In present study pulsatile micro-jets are placed downstream of the burner radially which breaks the coupling between acoustic waves and unsteady heat release. A microphone connected to LIFA (LabVIEW Interface for Arduino) was used to detect the sound pressure levels. By controlling the airflow rate of the pulsatile jets, the sound pressure levels were suppressed down to the background noise level using minimum energy and time. A closed-loop control system is developed for this purpose, which works on the feedback signal acquired from microphone. To simulate the one dimensional combustion phenomenon, an experimental setup called Rijke tube was used. The suppression was most effective for the pulsatile jets of 27-33 Hz pulsation frequency range and at a flow rate of 6.8 LPM. This control strategy effectively controlled the combustion instability of around 35-42 dB.•The closed loop control method is built on DAQ and Arduino using the LabVIEW interface for Arduino (LIFA).•Developed closed loop active control method was observed to be effective for suppression of thermo-acoustic instability.•Optimum position of the radial planes of micro-jets with respect to the burner was decided to improve the efficacy of the pulsatile jets towards suppression of thermo-acoustic instability.

Experimental method for temperature measurement on lateral planes along a Rijke tube to assess efficacy of control method.

The thermo-acoustic instabilities developed inside the combustor causes serious structural damage and reduces the life of power producing devices. The present work involves experimental investigation to assess effect of radial micro-jets air injection on thermo-acoustic instabilities and temperature in lateral planes. A co-axial pre-mixed gas burner used as the heat source inside the Rijke tube with variable location. Two types of Rijke tubes were used for experimental study, one is of steel with 75 mm internal diameter and 750 mm in length for the measurement of wall pressure, temperature and acoustics. •In the first part of the study, acoustic instability zone for different inlet mass flow rates was identified.•In the second part of study, the entire cross-sectional of Rijke tube was divided into 193 subzones and temperatures were measured at 193 locations when instability was present.•In third part, again temperatures were measured at 193 locations with implementation of control method with complete suppression of thermo-acoustic instabilities.