Characteristics of Char Cone Covered by Ash in Steady Smoldering of a Char Rod

ABSTRACT

A char cone, whose shape is similar to Bunsen flame and varies with oxidation conditions, was found in steady smoldering of biomass rods. In this short communication, characteristics of this char cone in natural downward smoldering of char rods with different diameters (2 – 7 mm) and ash contents (30–46%) were investigated via measuring propagation velocity and analyzing shape of char cone. Results showed that smoldering propagates steadily in all prepared char rods and the propagation velocity decreases with increasing diameter and ash content of char rods. Height of char cone is proportional to the mass flowrate of carbon, similar to the relationship between flame length and volume flowrate of gas fuel in laminar jet diffusion flame. It implies that oxygen diffusion through ash plays a dominant role in natural smoldering of char rod. This work provides some experimental basis for further investigation on mechanism of steady smoldering.

KEYWORDS:

• Steady smoldering
• char rod
• char cone
• propagation velocity
• height
• ash

Acknowledgments

The authors acknowledge the financial supports provided by National Natural Science Foundation of China (grant no. 51676115), Sino-German Center for Research Promotion (grant no. M-0183), Natural Science Foundation of Shandong (grant no. ZR2022ME038), and Innovation ability improvement project of small and medium-sized technology-based enterprises (grant no. 2021TSGC1114).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [51676115]; Natural Science Foundation of Shandong Province [ZR2022ME038]; Sino-German Center for Science [M-0183]; Department of Science and Technology of Shandong Province [2021TSGC1114].