射流扩散火焰在能源动力等领域的应用十分普遍，如工业窑炉、电站锅炉和燃气轮机等。稳定性是射流扩散火焰研究中的主要问题之一。该文针对气体射流推举扩散火焰向湍流转捩过程开展了落塔微重力实验，观测了微重力下推举扩散火焰的稳定行为，并通过与常重力下的实验结果进行比较，分析得出浮力对火焰稳定特性的影响。结果表明，火焰推举高度受到上游流动状态的影响较为显著，转捩过程中，层流射流发生间歇性破碎，火焰推举高度出现相应波动; 虽然微重力火焰的推举高度较小，但2种重力条件下推举高度波动具有相似的控制机制。转捩火焰和湍流火焰均表现出分裂现象，促使火焰振荡，火焰高度则随时间发生变化，由于微重力火焰高度远大于常重力火焰，火焰边缘剪切层不稳定性向下游区域的发展较为充分，火焰高度的变化范围更大。火焰分裂现象有着明显的随机性，在转捩阶段，微重力火焰的平均分裂频率略大于常重力火焰; 在湍流阶段，微重力火焰分裂频率相对较低并随着射流速度的增加而增大，这表明浮力可促进火焰分裂。此外，射流Froude数无法关联微重力火焰的分裂/振荡频率。该文有助于深化对推举火焰的转捩过程的认识，并进一步揭示浮力对火焰转捩和火焰稳定的影响。

Objective: Jet diffusion flames are widely used in industry, energy, and power, including industry kiln stoves, power station boilers, and gas turbines. Flame stabilization is an important problem in jet diffusion flames because of its involvement in the safety of combustion equipment, combustion efficiency, and pollutant emissions. Investigating the characteristics of flame stabilization and the related fire safety issues is important for the design of practical combustion equipment. Many investigations into the stabilization characteristics of laminar jet diffusion flames have been conducted. Our understanding of the characteristics of the flame shape and stabilization behavior of laminar flames is clear. However, for transitional and turbulent flames, especially for lifted flames, under normal gravity conditions, the coupling of buoyancy, jet flow, and Kelvin-Helmholtz (K-H) instability at the flame edge makes the problem more complex. Methods: Experiments were conducted on laminar-to-turbulent lifted jet diffusion flames under normal gravity and microgravity conditions. Variations in the flame lift-off height and length during the transitional process and the stabilization behavior of "non-buoyant flames" were observed. This study analyzes and discusses the stabilization characteristics of the lifted jet diffusion flames under microgravity conditions based on the experimental data of flame lift-off height and flame length. Compared with the results obtained under normal gravity conditions, the influences of buoyancy on the characteristics of flame stabilization were further analyzed. Results: Results showed that lifted flames under microgravity and normal gravity conditions yielded similar critical Reynolds numbers corresponding to the start and end of the transitional stage, respectively. During the transitional process, the flame lengths under microgravity conditions are approximately twice those under normal gravity conditions. The flame lift-off heights under microgravity conditions are always lower than those under normal gravity conditions; however, the differences between normal gravity and microgravity decrease as the jet flow velocity increases. The flame lift-off height is significantly influenced by the jet upstream of the flame base. In the transitional stage, the jet flow exhibits intermittent breakup, causing flame lift-off heights to oscillate. The transitional and turbulent flames all exhibit severe separation phenomena, resulting in the variation of the flame length with time. Because the flame lengths under microgravity conditions are longer than those under normal gravity conditions, the development of the K-H instability at the flame edge toward the downstream region is greater, and flame length varies over a wider range. Conclusions: Although flame lift-off heights under microgravity conditions were relatively low, the flame lift-off height fluctuations under the two gravity conditions had a similar control mechanism. Flame splitting is somewhat random. As Re=2 460 (transitional regime), the mean separation frequencies under the two gravity conditions have only a slight difference. In the turbulent stage, as Re also increases, the mean separation frequency under microgravity conditions increases. However, in the turbulent regime, the flame separation frequencies under microgravity conditions are relatively lower, indicating that buoyancy can promote flame splitting. Moreover, the relationship between the Strouhal and Froude numbers for the flame-splitting phenomenon indicates that the jet Froude number cannot correlate with the separation/oscillation frequency of the flames under microgravity conditions.