基于产物分析的铁粉燃烧器燃烧特性实验研究

Experimental Study on Combustion Characteristics of Iron Powder Burner Based on Product Analysis

关键词:  金属燃料  铁粉  金属燃烧器  燃烧产物  燃烧特性

Key words:  Metal fuel  Iron particles  Metal burner  Combustion products  Combustion characteristics

摘要:

铁粉是一种潜在的绿色可再生金属燃料。为了探索铁粉燃料使用的可行性，改进铁粉燃烧器的设计方法，研究铁粉的燃烧特性，进而实现铁粉燃烧后能量的有效利用，文中采用自主设计的金属铁粉燃烧器，实现了铁粉与空气在常压下的自持燃烧，进一步研究了铁颗粒燃烧后产物的变化规律。在点火燃烧实验中发现，铁粉的最佳点火浓度条件在0.95～1.28kg/m³。利用扫描电子显微镜（SEM）、激光粒度分析仪（LPSA）、聚焦离子束（FIB）和X射线衍射（XRD）等诊断手段对燃烧产物进行了分析。结果表明，铁颗粒燃烧后颗粒形貌由不规则形最终变成球形，在燃烧过程中生成的产物会直接包裹在金属液滴的表面导致产物的粒度增大，在空燃比为0.55时，粒度的增大率为1.2，富燃条件下，随着空燃比的提高，产物的增大率变大。使用相图预测了铁颗粒在燃烧过程中出现的多层结构，利用FIB方法进一步分析了铁颗粒在燃烧反应中间阶段的层结构由外向内分别为Fe₂O₃，Fe₃O₄，FeO和Fe。

Abstract:

The iron powder is considered as a potential green renewable metallic fuel. In order to explore the feasibility of using iron powder fuel， improve the design method of iron powder burner， study the combustion characteristics of iron powder and finally realize the effective use of energy after iron powder combustion， the self-sustained combustion of iron powder and air at atmospheric pressure was realized using the self-designed burner. The evolutionary law of the product and the combustion efficiency were researched as well. Results of the ignition and combustion experiments show that the optimum concentration of iron powder for ignition is 0.95～1.28kg/m³. The products were analyzed using scanning microscopy （SEM），laser particle size analyzer（LPSA），focused ion beam（FIB），X-ray diffraction（XRD）and other diagnostic methods. Results show that the morphology of iron particles would change from irregular to spherical after combustion. The products generated during the combustion process would be directly wrapped on the surface of the metal droplets， resulting in an increase of the product size. When the air-fuel ratio is 0.55， the increase rate of particle size is 1.2， which increases as the air-fuel ratio increases under fuel-rich condition. The multi-layer structure would form as the iron particle burns according to the analysis results of the phase diagram. The FIB method is used to further analyze the distribution of components from outside to inside， being Fe₂O₃， Fe₃O₄， FeO and Fe in the middle stage of combustion.