Prof. Fei Qi
Project Description and Objectives:
Combustion diagnostics techniques based on laser spectroscopy are accurate and nonintrusive techniques that have emerged to become an indispensable tool of combustion science and development of combustion technology. In this study, a swirl-stabilized burner is constructed to investigate flame dynamics and thermoacoustic instability. It consists of a driver unit, a settling chamber, a contraction ended by a constant diameter duct, a horizontal end piece and an enclosed chamber. The rotation of the flow is induced by an axial swirler equipped with eight twisted airfoil vanes. A small bluff body is used to stabilize the flame during the unsteady motion of the flow. A loud speaker installed at the bottom of the setup provides acoustic excitation to the flame. Air and fuel are premixed and then enter the bottom of the burner through two tubes.
To investigate the response of the swirling flame to the acoustic excitation, both the unsteady flow field and the evolution of the flame surface are measured simultaneously. The measurement techniques mainly depend on a high-speed burst mode Nd:YAG laser with a repetition rate of up to 100 kHz and two intensified high-speed CMOS cameras. High speed PIV is used for the measurement of the unsteady flow field. PLIF for the distribution of CH2O/acetone is used to capture the evolution of the flame front. Tunable diode laser absorption spectroscopy is adopted for the measurement of flame temperature and concentrations of CO2/ H2O. A hot wire is equipped in the downstream of the swirler used to measure the flow velocity variation due to the acoustic excitation. Raman scattering techniques have also been used in this study.