Research on Active Control of Combustion Instability Based on Pulsed Fuel Injection

An experimental investigation on open-loop active control of combustion instability in a spray swirling flame is conducted using pulsed fuel injection. A photomultiplier tube is employed to record the flame OH* chemiluminescence, the two-microphone method was utilized to measure air and fuel velocity fluctuations, and a high-speed camera was used to capture the dynamic processes of the flame structure. The suppression performance on combustion instability is investigated at various excitation phase delays with a pulsed fuel injection frequency of 175 Hz. Results demonstrate that pulsed fuel injection significantly suppresses combustion instability, achieving a maximum reduction of 7.8 dB in the combustor pressure fluctuation amplitude. The excitation phase delay is identified as a critical parameter for active control effectiveness. The flame heat release rate fluctuation is almost completely suppressed at an excitation phase delay of 40°, while the combustion instability is intensified at 220°. Moreover, pulsed fuel injection can effectively reduce flame structure pulsations. At the 40° phase delay, the flame length variation and center of mass are both reduced by 69%.