单颗粒铁粉燃烧特性及产物形貌分析

Under the national goal of“carbon peaking and carbon neutrality”, the carbon-free alternative utilization of fossil fuels has become very important. Metal fuels are a new type of carbon-free fuels, among which micron iron powder is considered to be the most potential metal fuel. However, the current understanding of the combustion mechanism of iron powder is still in its infancy. In order to study the combustion characteristics of single iron particle, a new type of iron powder burner was designed based on the principle of vibration-entrainment flow. It realizes the single iron particle supply and ensures its rapid combustion in a hot environment. The ignition and combustion processes of single iron particle with the diameter mainly distributed within 50 μm to 65 μm in the fuel-lean methane/air flame environment were investigated. It was observed that the combustion process of single iron particle was mainly divided into three stages: combustion retardation, normal combustion and product solidification. The combustion history of single iron particle was captured by using a high-speed digital camera, and typical combustion brightness anomalies were found. The sharp variation of the motion speed of iron particle was observed in the later period of combustion. In addition, the intermediate and final products of combustion were analyzed. It indicates that single iron particle melts in the initial of combustion, then the gas generates and expands during the combustion process, and the product particle bursts and becomes a hollow thin-walled sphere eventually.