Ignition and extinction characteristics of swirl spray flames at low temperatures

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Abstract

Lean blow-out (LBO) and lean light-off (LLO) in gas turbine combustors under high-altitude, low-temperature conditions have become critical issues for modern aircraft engines. In this study, a swirl spray combustion platform is employed to investigate the low-temperature LBO and LLO characteristics of Jet-A spray flames at atmospheric pressure. 

The air and fuel temperatures are varied either simultaneously or independently within the range of 253–293 K to examine the sensitivities of LBO limits, LLO limits, atomization, and evaporation to temperature. A phase Doppler particle analyzer (PDPA) is used to measure droplet velocity and Sauter Mean Diameter (SMD). The results show that as the fuel temperature decreases from 293 K to 256 K, the LBO and LLO limits increase by 7.8% and 6.9%, respectively, indicating comparable levels of deterioration. 

When both the fuel and air temperatures decrease simultaneously from 293 K to 253 K, the degradation of the LLO limit becomes significantly more pronounced than that of the LBO limit: the LLO limit increases by 43.4%, whereas the LBO limit increases by 14.4%. 

The mechanisms by which low fuel temperature and low air temperature influence the LBO are different: low fuel temperature affects LBO primarily by degrading atomization quality, whereas low air temperature reduces fuel evaporation. Under low-temperature conditions, ignition performance deteriorates due to poor atomization and increased heat loss, both of which impede the formation and propagation of a stable flame kernel.

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