Staff

The lean premixed combustion concept is considered as a promising combustion strategy in gas turbine combustors due to its lower pollutant emissions compared to conventional combustion modes. However, lean premixed combustion can be highly affected by flame oscillations and instability. Specifically, the presence of lean blow-off (LBO) due to the decrease of equivalence ratio, increase of turbulent intensity, or incomplete combustion is extremely harmful for the gas turbines and results in increased pollutants. Previously, several experimental and modeling investigations have been conducted to understand the fundamental mechanism of LBO under lean premixed combustion condition, and Damköhler number (Da), a parameter based on global time-scale estimates, has been widely used to describe and predict the LBO. However, detailed local flow and chemical information of the lean premixed flame near LBO and comprehensive experiment database that can be used to develop physical-based LBO model are insufficient.

To get further insight into the fundamental mechanism of LBO phenomenon, comprehensive onsite diagnostics of turbulent lean premixed flame dynamics and structures near blow-off at different Karlovitz numbers (Ka) will be conducted to further understand the dynamic and kinetic blow-off mechanisms, and develop an efficient and reliable combustion model for turbulent lean premixed flames near LBO. 1D Raman/Rayleigh scattering and OH-laser-induced-fluorescence (OH-LIF) will be employed to measure major species concentrations (N2, O2, CH4, H2O, CO, CO2, H2), temperature and OH radical, respectively. The experimental data will be evaluated by a hybrid method, which combines spectral fitting and matrix inversion of signals that are not spectrally resolved.