The experimental investigation carried out allowed one to determine the infl uence of the source coal grade, oven medium temperature, and of the CWF drop size on time and temperature correlations characterizing the process of individual fuel drop combustion in static air. It has been established that shortening of the total time of CWF drops combustion related to the oven medium temperature increase and the drop size decrease is governed by a power function. In identical conditions, the time of CWF drops combustion is shortened signifi cantly, when anthracite is replaced by the brown source coal. The research and processing of the obtained experimental data allowed establishing empirical dependences of the CWF drop combustion time on volatile content in the source coal, and on drops sizes, taking into account the oven medium temperature and the source coal grade. It was found that in the equation describing the dependence of the combustion time on the drops sizes the exponent of the size is equal to 1.6 and does not depend on the coal grade and oven medium temperature.
For the fuel ignition, the thermal conductivity and heat capacity are the key properties that determine the pre-ignition behavior of the drop of the fuel. The classic monophase fuels, such as natural gas, liquid propellants, or solid onecomponent fuels, have been investigated for a long time; and their thermophysical properties are well known in most of the cases. Composite fuels, which have recently attracted the attention of the researchers, have complex contents. In many cases, composite fuel is a mixture of solid and liquid components in the form of a slurry. Coal-water fuel and its derivatives with different additives are examples of such type fuels. For those fuels, the thermophysical properties are usually unknown. Nowadays, researchers use simple additivity theory for the calculation of the thermophysical properties of complex fuels for the first approach. Authors of this research believe that the simple additivity approach is not correct and can lead to the wrong results in the case of the numerical research of the ignition and burning processes of such a fuel. In the present research, the thermophysical properties of coalwater fuel with glycerol additives were experimentally obtained. It was found that the coefficient of thermal conductivity increases with temperature and varies in the range of 0.45 to 0.53 W/(mÁK). The heat capacity of the fuel also increases with the temperature and varies from 4.7 to 5.5 kJ/kgÁK. The higher the glycerol content, the lower the thermal conductivity and heat capacity of the composite fuel in the investigated temperature range. The results confirm the failure of the approach of the additivity law usage. Neither, thermal conductivity coefficient or heat capacity of the coal-water fuel with the addition of up to 20% glycerol complies with the additivity law. Differences between real values of the thermophysical properties and calculated ones are more than 30% No colors needed for a print copy of the manuscript.
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