Investigation of lean blow off limits of a spray flame in a laboratory-scale RQL-type burner

Nagao, Jun, Rajendram Soundararajan, Preethi, Kurose, Ryoichi and Mastorakos, Epaminondas (2024) Investigation of lean blow off limits of a spray flame in a laboratory-scale RQL-type burner. In ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition. vol. GT2024-127205, ASME Turbo Expo. 10 pp . (doi:10.1115/GT2024-127205).

Abstract

This experimental study explores the stability of an ethanol spray flame under conditions close to lean blow-off (LBO) in a rich-quench-lean (RQL)-type combustor. The combustor has a primary inlet with a swirling air flow and four radially injected dilution air inlets. The split ratio (SR) of primary to dilution air was varied (10:0, 8:2, and 6:4) at different fuel mass flow rates to quantify the LBO conditions. Results showed that there was only a minor difference in the LBO conditions for SRs of 10:0 and 8:2 for all fuel mass flow rates. In contrast, the LBO equivalence ratio increased at SR of 6:4. This is attributed to the different blow-off mechanisms at SR of 6:4 compared to the case of lower dilution, as suggested by the analysis of the blow-off event obtained using high-speed OH* chemiluminescence imaging. Those revealed that the flame started to extinguish downstream and around the spray cone region for SR of 10:0 and 8:2, but the flame first lifted off and then extinguished close to the nozzle at SR of 6:4. The high-speed OH* images were analyzed with Proper Orthogonal Decomposition (POD), which demonstrated different modes of flame fluctuations between conditions far from and close to LBO. The results obtained from this study can be used for validating gas turbine combustor CFD models.

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Contributors

Author: Preethi Rajendram Soundararajan

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