Maryuch V. Improvement of the efficiency of dry chemical fire suppression of magnesium and its alloys

The dissertation is devoted to the solution of the actual scientific and technical problem – the development of the dry chemical powder for extinguishing fires of magnesium and its alloys (class D fires). The problem was solved by means of laboratory studies of magnesium chips extinguishing by various dry chemical powders and the development of a damping nozzle for the supply of extinguishing powder. The mathematical modeling was used for determination of its optimal construction. For this purpose, field testing of the developed dry chemical powder and the nozzle was carried out. Dry chemical powders were studied and a formulation of DCP for the class D fires extinguishing was developed. Laboratory investigations of extinguishing mixtures consisting of sodium chloride, ground slag and aerosol were carried out and the parameters of extinguishing were determined. The mathematical modeling of using different damping nozzles for the delivery of a DCP was carried out. A nozzle for the extinguishing of class D fire with two working surfaces – an elliptical top and a parabolic reflector was chosen. The studies revealed that the nozzle with two working surfaces is more efficient than a pre-cooler with one-way reflector and one working surface. It allowed delivering more (about 30%) DCP into the combustion zone. That can improve the effectiveness of extinguishing, allowing covering the combustion surface with larger layer of powder without blowing it from the surface of the combustible metal. The burning time of the model fire decreased from 20 seconds to 7 seconds. A draft methodology for determining of the fire-extinguishing efficiency of DCP was developed. The required amount of fuel for burning magnesium and its alloys was determined.