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The International Conference on
Aerospace System Science and
Engineering

JULY 06-07, 2023

SHANGHAI, CHINA

Invited speech

Yi Gao

Associate Professor in the School of Aeronautics and Astronatics,
Shanghai Jiao Tong University
Research Interest: Laser diagnostic and optical imaging

Title: Study on the blow-off characteristics of bluff-body stabilized premixed flame utilizing high-speed PIV/OH-PLIF measurements

Abstract: In recent years, the bluff-body stabilized flames have been widely used in practical combustion devices due to their excellent flame-holding capability. However, local extinctions and even global blow-off events occur frequently due to the high turbulence of the practical combustion environments and the harsh flame temperatures. There is still a lack of deep understanding of the mechanism behind lean blow-off (LBO) events. It will be helpful to avoid this kind of danger to the engines if we can recognize the precursor and predict the LBO event, and further control can be applied immediately and adequately. In this study, the LBO dynamics and instability behavior of a 2D bluff-body stabilized premixed flame were investigated. Experimentally, 5 kHz OH* chemiluminescence, 10 kHz particle image velocimetry (PIV), and 10 Hz OH planar laser-induced fluorescence (OH-PLIF) were applied to acquire the simultaneous information on the velocity and combustion characteristics from the flame. It is found that a significant change of the flame structure, the "necking" of flame in the stagnation-point region (SPR) followed by "pinch-off" of the flame, is considered a typical precursor of the blow-off event. The causes of the "necking" and "pinch-off" were analyzed under stable and near LBO conditions. Meanwhile, the investigations utilizing the CPIV were conducted under varying equivalence ratios from stable combustion to near LBO. The difference between the flame fronts extracted by CPIV and OH-PLIF methods can be used to estimate the preheat layers and local extinctions that are filled with CH2O radicals, especially under conditions close to the LBO. And last, we further demonstrated that increasing the bluff-body temperature leads to an enhanced turbulent flame speed and strengthened strain rates, and as a result, the local extinction can be suppressed, and the blow-off limit can be extended.

Short-biography: Dr. Gao received her doctoral degree in 2013 at the University of Erlangen-Nuremberg, Germany. From 2014 to 2016, she worked as a postdoctoral fellow at the University of Cambridge, UK. Since 2017 Dr. Gao has been working as an associate professor at Shanghai Jiao Tong University. Dr. Gao has devoted more than ten years to working in the research field of advanced laser diagnostics with ultra-high spatial and temporal resolution and their applications for fundamental research in modal/industrial combustors.