Zaitsev M. Improvement of gas dynamics in low-capacity fire tube boilers.

The scientific novelty of the obtained results lies in the performance of numerical modeling and experimental comparison of modern models of low-power heat generators when the heat load changes. For the first time it was found that the occurrence of a transverse vortex ring at a distance of 2 diameters of the axial pipe from its cross section, which has a negative impact on the efficiency of gas combustion in the furnace. For the first time it was found that it is most rational to use the proposed method of gas combustion with the formation of the aerodynamic structure of the axial direct flow jet of gas by an external swirling jet in the power range from 50 to 130 kW. In the first section of the dissertation the analysis of the current state of energy efficiency of low-power heat pipes is made, it is concluded that to improve the efficiency of low-power heat generators, when the heat load changes during the heating period, it is necessary to perform numerical modeling and experimental comparison of modern heat generators. The second section presents the results of numerical modeling and experimental comparison of modern models of low-power heat generators when the heat load changes. In the third section, theoretical data on the aerodynamic structure of flows in the furnace of a low-power boiler using a combined burner are obtained. Theoretically, it is found that in cases of exceeding the axial velocity over the velocity of the external swirling flow, there is a local velocity jump, which shifts along the length of the jet as it moves away from the central axis. This phenomenon is explained by the occurrence of a transverse vortex due to different conditions of opening of coaxial jets and, as a consequence, the formation of a corresponding zone of reduced pressure. In this case, the appearance of such a vortex is not observed in the opposite situation, when the speed of the axial jet is less than the external one. In the fourth section, experimental studies of the interaction of jets in a combined burner and their effect on the thermal intensity of the furnace are performed. The combined burner proposed on the basis of theoretical researches consists of two tangential branch pipes for air supply and an axial branch pipe for gas supply. Thus, the obtained data confirm the possibility of adjusting the uniformity of temperature distribution in the volume of the furnace by the proposed method. The proposed combined burner in the furnaces of low-power boilers allows to increase the average annual efficiency of the boiler by 20% compared to standard boilers.