Особливості аеродинаміки пальникових пристроїв з циліндричними стабілізаторами полум’я за наявності турбулізаторів потоку на їхніх зривних кромках

Анотація

Specifics of burner aerodynamic with cylindrical flame stabilizers in the presence of turbulence stimulators of flow on their stalling edges

N. Fialko, N. Maison, O. Tymoschenko, N. Meranova, G. Ivanenko, V. Yurchuk, M. Ganzha, M. Donchak,  M. Abdulin

In this paper the results of comparative studies of the flow structure of fuel and oxidizer in the burners with cylindrical flame stabilizers at the presence and absence of flat turbulence stimulators of the flow on the stabilizer stalling edges are presented. The features of the aerodynamic for the series of the burners with turbulence stimulators of the flow with a capacity of 30-200 kW are found.

Stabilized burners, based on the use of cylindrical elements, are widely used in the energy practice – modular elements of combustion chambers ABB, different tubular type burners, based on the cylindrical channels with expansion, and others. The results of the investigation of transfer processes in such burners that are characterized by a high degree of burning diffusivity are submitted in works of V.A. Khrystych, G.M. Lyubchyk, G.B. Varlamov, G.S. Marchenko, G.A. Mikulin and others. Thermophysical studies of burners with cylindrical flame stabilizers, in which workflow is characterized by relatively high degree of kinetic combustion, are limited. This causes the topical of detailed research of the workflow in such burners.

The purpose of this research work is to establish patterns of flow of fuel and oxidizer in burners with cylindrical flame stabilizer at the location of flat turbulence stimulators of the flow on their stalling edges.

Cylindrical flame stabilizer is positioned in a cylindrical channel coaxially. The air is supplied into entrance of the channel. Natural gas, which to be burning, through the system of the holes in the side surface of the stabilizer by penetration of is gone into blown off airflow. Flat turbulence stimulators are installed on the end of the stabilizer at 90 degrees to each other across the flow.

Solving this problem was carried out based on the RANS approach using RNG k-ε turbulence model. A comparative analysis of the flow pattern in the cylindrical burners in the presence and absence of the turbulence stimulators of the flow is done. It is shown that in the absence of the turbulence stimulators on the stalling edge of the flame stabilizer there is a one recirculation zone directly behind the end surface of the stabilizer. In the presence of the turbulence stimulators a recirculation zone takes place behind each of stimulation. The length of these zones downstream significantly exceeds the length of the recirculation zone behind the end face of the flame stabilizer provided when on his trailing edge are not installed the turbulence stimulators of flow. Significantly higher levels of velocity pulsation for large parts of the flow behind flame stabilizer is observed at present of the turbulence stimulators. The character of velocity fluctuations fields is significantly different also for compared situations. In the absence of the turbulence stimulators the zones with increased levels of pulsation are located in the central part of the channel corresponding to the stream recycle zone. In case of present of the turbulence stimulators on the stalling edge of the flame stabilizer maximum level of pulsation is observed on the boundaries circulating flow zones for each of the four turbulence stimulators of flow. Moving from the end of the stabilizer downstream the zone boundaries of increased turbulence of the flow are blurred somewhat. The results of computer simulation concern flow patterns of fuel and oxidizer for the series of the cylindrical burner with turbulence stimulators of flow with a capacity of 30 - 200 kW are given. It is established that for the different power burners the flow turbulence is the most significant near areas of return flows, which are formed behind all turbulence stimulators.

The analysis of changes in the intensity of turbulence along the axis of track after the flame stabilizer for the series of considered burners in the presence and absence of turbulence stimulators of flow is done. It is shown that the installation of turbulence stimulators of flow on the stalling edge of the flame stabilizer can cause essential increase in the intensity of turbulence. This increase is most significant near the end of the stabilizer in the areas corresponding to the maximum intensity of the turbulence. Turbulence intensity increases by more than 40% thanks to the turbulence stimulators of the flow.