随着航天事业的快速发展和太空探索范围的不断扩大, 微重力、超重力等变重力环境下的燃烧研究逐渐成为航天领域的研究热点。其中, 射流预混火焰以其高效、低排放的特性在燃烧科学中备受瞩目。深入探究重力效应对射流预混火焰的影响机制, 对于优化空间环境中的燃烧过程至关重要。该文总结了国内外关于射流预混火焰重力效应的研究进展, 首先阐述了落塔实验、离心机实验、飞机失重实验等多种实验平台下的微、超重力研究环境。研究对象主要包括锥形火焰、中心钝体火焰以及多面体火焰等特殊形态的射流火焰。通过例如激光纹影、图像粒子测速、激光诱导荧光等新型实验技术手段和数值模拟方法, 揭示了重力效应对火焰形态、稳定性、闪烁现象等方面的影响。该文可为航天领域燃烧科学方向的研究提供理论支持。

Significance: With the accelerating pace of human aerospace endeavors and broadening horizons of space exploration, investigating combustion phenomena in variable-gravity environments, particularly microgravity and supergravity, has emerged as a research frontier in aerospace science. Comparing to diffusion flames, premixed flames makes more adequate combustion, which improves energy efficiency and generates much less pollutants. Thus it is essential to elucidate how gravity influences these flames to optimize combustion processes in space. This review aims to consolidate current knowledge on gravity's effect on premixed jet flames, fostering advancements in aerospace combustion technology. Progress: This article systematically surveys domestic and international research advancements on how gravity affects premixed jet flames. It encompasses various experimental setups designed to simulate microgravity and supergravity conditions, including tower drop experiments, centrifuge facilities, and aircraft weightlessness simulations. The focus is on various flame configurations, such as conical, rod-stabilized, and polyhedral jet flames. The effects of gravity on flame morphology, stability, flickering behavior are examined using multiple techniques such as laser imaging for flame visualization, particle image velocimetry for flow field measurements, planar-laser-induced fluorescence for species-concentration mapping, and computational fluid dynamics simulations for detailed mechanistic insights. These methodologies help explore the complex interactions among fluid dynamics, heat transfer, and chemical kinetics under altered-gravity conditions. Furthermore, the review examines different control parameters, such as the equivalence ratio, Reynolds number, and initial pressure, which influence the behavior of premixed flames. Attention is also given to experimental conditions that affect the reproducibility and generalizability of the findings, such as fuel type, combustion-chamber geometry, and specific flame initiation and stabilization procedures. The findings reveal that gravity significantly affects the characteristics of premixed jet flames, influencing their shape, stability, and dynamic behavior. In terms of flame shape, the review demonstrates how gravity significantly influences the geometric structure. Microgravity causes flames to become more spherical owing to reduced buoyancy effects, while supergravity elongates and distorts flames owing to intensified buoyancy-driven flows. In terms of flame stability, the stability boundaries of premixed flames are found to be highly dependent on the magnitude of gravity. Microgravity allows for a broader range of stable operations, while supergravity narrows these boundaries, leading to increased instability and flame extinguishment. The review also addresses buoyancy-induced flame flickering, highlighting that the flickering frequency is directly related to the magnitude of gravity. Lower gravity magnitudes lead to less frequent flickering owing to diminished buoyancy-induced shear-layer oscillations. Conversely, increased gravity magnitudes intensify these oscillations, increasing the flickering frequency. Conclusions and Prospects: This comprehensive review consolidates state-of-the-art knowledge on the effect of gravity on premixed jet flames, offering valuable insights for researchers. It underscores the significance of ongoing exploration in the aerospace domain, driven by advancements in experimental techniques and computational modeling. By providing theoretical underpinnings and practical guidance, this review aims to stimulate further research, driving the development of more efficient and environmentally friendly space propulsion systems.