Mathematical Modeling of a Power Line–Electric Drive–Pump–Pipeline Power Technological Complex

Статья из журнала.Abstract: In this paper, a block diagram of a power line–electric drive–pump–pipeline system consisting of individual interconnected elements that makes it possible to use the structural method for mathematical modeling is presented. The results of the modeling confirm the viability of the proposed mathematical models. It is shown that, due to a considerable inertia of turbo mechanisms, the electromagnetic phenomena in the electric drive can be neglected so as to simplify significantly the structure of the studied system. Soft acceleration of the asynchronous motor by means of a soft starter makes it possible almost to eliminate the shock surges of the moment, which has a positive effect on the turbo mechanism operation. However, the high-frequency component of voltage, which emerges due to the soft starter operation, can affect the operation of other energy consumers. The applicability and efficiency of using polar coordinates to construct mathematical models of complex technical systems containing three-phase electromechanical energy transducers is confirmed. © 2020, Allerton Press, Inc

Ignition and Self-Supporting Burning of Gas-Air Mixtures with Hydrogen Admixtures on Platinum Wire

The proposed work describes analytical identification of hydrogen admixture concentration and catalyst temperatures limit values beyond which catalytic flameless steady combustion of gas-air mixtures at ambient temperature at platinum wires is observed. Effect of gas-air slip velocity upon considered values is shown. Initial platinum wire preheating temperatures required for catalytic ignition are determined. Keywords: metallic oxidation catalysts, wire, hydrogen, heat and mass transfer hysteresis, self-ignition, fade, surface (flameless) combustion.</span

A conservative finite difference method and its application for the analysis of a transient flow around a square prism

Detailed results of numerical calculations of transient, 2D incompressible flow around and in the wake of a square prism at Re = 100, 200 and 500 are presented. An implicit finite‐difference operator‐splitting method, a version of the known SIMPLEC‐like method on a staggered grid, is described. Appropriate theoretical results are presented. The method has second‐order accuracy in space, conserving mass, momentum and kinetic energy. A new modification of the multigrid method is employed to solve the elliptic pressure problem. Calculations are performed on a sequence of spatial grids with up to 401 × 321 grid points, at sequentially halved time steps to ensure grid‐independent results. Three types of flow are shown to exist at Re = 500: a steady‐state unstable flow and two which are transient, fully periodic and asymmetric about the centre line but mirror symmetric to each other. Discrete frequency spectra of drag and lift coefficients are presented.</jats:p

Mathematical Model of an Induction Machine in Polar Coordinates Taking into Account the Saturation Process of the Main Magnetic Circuit

Статья из журнала.Mathematical models of induction machine in polar coordinates taking into account the saturation process of the main magnetic circuit are presented. Software implementations of the proposed mathematical models and numerical investigations of the processe