Modeling the Effects of Equivalence Ratio on Carbon Nanotubes Diameter in Premixed Flame Based on Semi-Empirical Approach

Abstract In the combustion-based synthesis method, morphological control of carbon nanotubes (CNT) to meet specific demands for technological applications remains a challenge. The present study investigates the effect of equivalence ratio on CNT diameter in a premixed flat flame using a computational method validated by experimental investigations. Six cases were examined in the study by varying the equivalence ratio (∅), a combustion parameter that regulates the overall flame temperature, from 1 to 2 at intervals of 0.2. For each of the six cases, a comprehensive validation of the premixed flat flame temperature as predicted by computational fluid dynamics (CFD) is attained within a 10% deviation. A semi-empirical correlation between CNT diameter and flame temperature was established by deploying the computed flame temperature as the dependent variable in the empirical correlation of existing experimental work that the present study was based on. The findings indicate that the average flame temperature and CNT diameter increased by 5% and 20%, respectively, when the equivalence ratio ∅ was reduced from 2 to 1. Furthermore, only within 6 mm downstream of the flame site does the effect ∅ on CNT diameter become noticeable. According to actual microscopy findings, CNTs with greater diameters within 36–46 nm and smaller diameters within 29–41 nm are expected at high-temperature regions (T > 1300 K) and low-temperature regions (T < 1300 K) within the flame, respectively.