The effect of blend ratio on the combustion process of mutually stratified blended fuels pool fire

Author: Gao, Z. H., Wan, H. X., Ji, J.

Journal: Proceedings of the Combustion Institute

DOI: 10.1016/j.proci.2020.08.045

Keywords: Blend ratio, Blended fuels, n-heptane-methanol, Pool fire, Mass loss rate, feedback, gasoline, ethanol, surface, model

Abstract: 

The combustion characteristics of blended fuels pool fire were experimentally studied. Six square pools with length ranging from 5 cm to 20 cm were adopted, and mutually insoluble n-heptane-methanol blended fuels were used with different mixing proportions. In the experiments, burning rate and fuel temperature were measured and recorded during the whole combustion process. Results show that the special effect of azeotropism can influence the burning characteristics of n-heptane-methanol blended fuels to a large extent. For the cases with n-heptane fraction larger than the azeotropic proportion (0.485), there exists two burning stages of blended fuels and n-heptane, respectively; while if n-heptane fraction is smaller than 0.485, the two burning stages turn into blended fuels and methanol, respectively. In the steady burning stage of blended fuels, the fuels will burn together at the constant azeotropic proportion (0.485) regardless of the initial mixing proportions of liquid fuels. Due to the effect of azeotropism, the blended fuels are boiling at the azeotropic point (59.1 degrees C) lower than either boiling point of n-heptane and methanol, which leads to smaller mass loss rates compared to the pure fuel pool fires. That is, the azeotropism between n-heptane and methanol weakens the burning intensity of blended fuels compared to the pure fuel. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.