Mathematical modeling of heat transfer in a droplet of coal-water fuel leading to its fragmentation

Abstract

• Fragmentation model has been developed for heated droplets of fuel suspensions. • The main mechanisms of heat transfer are taken into account. • The heating conditions effect on the disintegration inertia has been determined. • Model allows for varying solid and liquid components concentrations in wide ranges. • Model is used to describe the conditions in the combustion chambers of power plants. Based on the results of the experimental studies performed, physical and mathematical models were developed to describe the processes of heat transfer in droplets of potential coal-water fuels (CWF) before their fragmentation caused by intense heating. The model is based on the solution of a system of heat transfer equations taking into account specific features of the CWF droplets fragmentation identified in the course of experiments. CWF droplet fragmentation delay times were recorded in the course of heating using the disintegration criterion identified in the experiments performed. In the case of CWF, complete evaporation of water from fuel composition droplet serves as the criterion. A series of experiments were carried out to test the model and to clarify the mechanism for implementing the processes investigated. The effect of a group of the following factors on the fragmentation delay times was determined: the temperature (773–2273 K), the initial droplet sizes (0.05–1.55 mm) and the component composition of the fuel (solid particles concentration varied between 40 and 60 wt%). The conditions for the intensification of the processes of fragmentation and ignition of potential fuel suspensions were singled out.