Features of swirled flows in power plant chimneys

The results of computational studies of the cylindrical and conical chimneys operating modes are presented. It is shown that with opposite gas supplies, swirling flows appear. Their shape and intensity depend on the type of chimney stack and the gas supply conditions. Swirling flows significantly affect the fields of axial and tangential velocities and determine the conditions for the gas outflow from the chimney.

A MACHINE-LEARNT WALL FUNCTION FOR ROTATING DIFFUSERS

Data-driven techniques have proved their effectiveness in many engineering applications. Machine-learning has gradually become a paradigm to explore innovative designs in turbomachinery. However, industrial Computational Fluid Dynamics (CFD) experts are still reluctant to embed similar approaches in standard practice and very few solutions have been proposed so far. The aim of the work is to prove that standard wall treatments can obtain serious benefits from machine-learning modelling. Turbomachinery flow modelling lives in a constant compromise between accuracy and the computational costs of numerical simulations. One of the key factors of process is defining a proper wall treatment. Many works point out how insufficient resolutions of boundary layers may lead to incorrect predictions of turbomachinery performances. Wall functions are universally exploited to replicate the physics of boundary layers where grid resolution does not suffice. Despite their popularity, these functions are frequently applied in flows where the ground assumptions cease to be true, such as rotating passages or swirled flows. In these flows, the mathematical formulations of wall functions do not account for the distortion on the boundary layer due to the combined action of centrifugal and Coriolis forces. Here we will derive a wall function for rotating passages, through means of machine-learning. The algorithm is directly implemented in the N-S equations solver. Cross-validation results show that the machine-learnt wall treatment is able to effectively correct the turbulent kinetic energy field near the solid walls, without impairing the accuracy of the k-epsilon model.

Confined multiphase swirled flows in chemical engineering

Exploration of confined swirled flows in the former USSR and present-day Russia has a long history and is presented by numerous publications, mostly written in Russian. The obtained results have been put to practical use in different areas of chemical, energy, and processing industries. In view of the process intensification concept, such characteristics of confined swirled flows may be considered unique: high centrifugal gravity, elongation of trajectories, the presence of internal separation zones, energy separation phenomena, and efficient mass/heat transfer in the absence of any moving parts. For instance, high gravity provides an excellent opportunity for multiphase flow stabilization, preventing the appearance of nonuniformities and stability loss, while enhancement of various driving forces acting on the reaction medium takes place. This review is devoted to outlining the main research trends and to discuss the most essential practical implementations in the subject matter done up until now. It is not foreseen to embrace the whole area of swirled flow investigations in the world, but only covers most of the significant ideas and applications contributed in by former Soviet and Russian scientists and engineers. Shortcomings and difficulties of using swirled flows are also briefly discussed.

Dust Collecting System for the Cleaning of Atmospheric Ventilation Emissions

The paper gives a description of a dust collecting system for the cleaning of atmospheric ventilation emissions. The system includes two successively installed vortex dust collectors with countercurrent swirled flows. The exhaust is organized from the first-stage hopper. After the cleaning in the additional device of the same design, the exhaust dust-air mixture is delivered to the lower inlet of the second-stage dust collector. The forecast evaluation of the system efficiency was carried out on the basis of the solution of balance equations for dust flows. The experimental evaluation of the system efficiency was carried out in industrial conditions on the basis of the full factorial experiment. The dependence characterizing the efficiency of the suggested system was obtained on the basisof the investigation results, and the most rational modes of the system operation were determined.