Abstract
This article discusses the atomization of composite liquid fuels. A large group of injectors is considered. A comparative analysis of the atomization characteristics (droplet sizes and velocities, jet opening angles) and the influence of the fuel characteristics (density, viscosity, component composition) and the process parameters (the ratio of the fuel–air mass flow rates, the features of the jet formation) has been carried out. Finally, the most effective types of injectors, which provide for the necessary characteristics of fuel atomization for its combustion, have been determined. The most favorable conditions for the applicability of each type of atomization have been formulated. Possible mechanisms of secondary fragmentation of droplets of composite fuels have been analyzed: those resulting from mutual collisions of droplets in the flux and from the interaction with a solid surface as well as those resulting from thermal overheating in the presence of a phase boundary or a large gradient of component volatility. A conclusion is made about the need of using a synergistic effect of primary and secondary atomization of fuel suspension droplets.
Highlights
The scale of the problem is exacerbated by the fact that the share of coal power plants in world’s leading economies (China, India, USA)
composite liquid fuels (CLFs) are normally injected into the combustion chambers of power plants using injectors similar to those used for atomizing conventional liquid fuels
10 of 18the liquid fuel jet is subjected to aerodynamic impact from the gas flows, which results in the jet being converted to a polydisperse flux
Summary
The use of fuel compositions as an alternative to conventional combustible liquids is receiving more demand for a number of reasons. The use of natural gas as an energy source is considered the most environmentally friendly option It incurs high costs, and its transportation requires pipelines or ad hoc liquefaction plants. A possibility to recover a large group of combustible waste as fuel components; reduced fire and explosion hazard at power plants due to the presence of water in the composite fuel composition. In this regard, the research and development of the applicability of fuel compositions based on industrial wastes [7,8,9,10] and the technologies of direct coal liquefaction [11,12]. In order to prevent stratification of composite fuels by their components and to support rheological properties suitable for the power production industry, specialized surfactants (i.e., stabilizers) must be introduced into compositions [7,10,15]
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