Numerical modelling of air flow attributes in a contractions chamber

Článek popisuje turbulentní charakteristiky proudu vzduchu ve vnitřním prostoru dýzy obdélníkového průřezu za účelem potvrzení jejího optimálního tvaru. Úloha je řešena numericky pomocí sofware Ansys Fluent. Vhodné modely byly vybrány na základě vyhodnocených výsledků na výstupu z dýzy, které byly porovnány s fyzikálním experimentemThe article describes air flow turbulent attributes in the enclosed chamber of a rectangular cross-section contraction for the purpose of confirming its optimal shape. The task is solved numerically using Ansys Fluent software. Right models were selected based on the evaluated results at a contraction’s outlet which were compared to the physics experimen

Influence of wood component on physical and chemical transformations during high temperature heating of composite fuel based on bituminous coal

Experimental studies of ignition delay time for mixtures of dispersed hard coal of two types and milled wood over a wide temperature range have been performed. Time of total completion of organic part pyrolysis of both components at different concentrations have been established in order to assess the prospects for such fuels application in large- and small-scale power engineering (combustion in boiler furnaces of different capacities). It has been established that simultaneous thermal decomposition of mixture of coal and wood particles leads to a significant change of pyrolysis temperature range and release of anthropogenic gases (sulfur and nitrogen oxides) in case of high-temperature heating of the mixture based on lean coal. The same effect, but in much smaller scale, has been recorded for a mixture based on long-flame coal. A hypothesis has been formulated on the mechanism of sulfur and nitrogen oxides precipitation during thermal decomposition of the mixture of lean coal and wood particles as a result of interaction between transitory gaseous and solid pyrolysis products of coal and wood in the temperature range up to 1000°C. Prospects of applying the milled coal and wood mixtures as fuel for steam and hot water boilers have been substantiated. With a small decrease of energy characteristics of such fuels, compared to homogeneous coals, significant improvement of ecological and economic characteristics of the fuel combustion processes can be achieved. It has been shown that vital synergistic effect of co-combustion of coal and wood particles is achieved only with certain coals

Modern understanding of "geoeconomic position" and the Saint Petersburg agglomeration

This article presents a modern interpretation of the concept of "geoeconomic situation" as applied to one of the most important centers of the Baltic region - the St. Petersburg agglomeration. The coastal location of the agglomeration and close connections with the Leningrad region make it possible to consider the Saint Petersburg coastal region (Baltic Area) as a whole. The article sets out not only to verify, confirm, and explain the features of the geoeconomic position of the coastal region, but also to describe the contiguous geoeconomic space. The position of the St. Petersburg coastal region is of crucial importance for ensuring a steady growth of regional economy, the propagation of industrialization impulses, and modernization in the heart of Russian Northwestern macroregion. At the same time, the specific features of the region's geoeconomic position magnify the "inherited" ad acquired effects of focal industrialization and space polarization, which creates additional prerequisites for the inversion of the Russian economic space - "Russia of the physical space" and "the economic space of Russia". The study uses traditional methodology of economic geography (the territorial, cluster, and spatial approaches) and the geoeconomic approach developed by the authors. The article also addresses recent findings in regional economy and spatial studies. It is aimed at the development of the geoeconomic paradigm in the framework of social geography and that of spatial science. An analysis of the geoeconomic position and the developing spatial relations can be of interest for researchers of geographic clusters, agglomerations, and such cross-border forms of cooperation, as growth triangles, for example

Inaccuracy Determination in Mathematical Model of Labsocs Efficiency Calibration Program

The study of radioactive materials quantitative inaccuracy determination caused by semiconductor detector aging is presented in the article. The study was conducted using a p- type coaxial GC 1518 detector made of a high-purity germanium produced by Canberra Company and LabSOCS mathematical efficiency calibration program. It was discovered that during 8 years of operation the efficiency of the detector had decreased due to increase of the dead layer of the germanium crystal. Increasing the thickness of the dead layer leads to 2 effects, which influence on the efficiency decrease: the shielding effect and the effect of reducing the active volume of the germanium crystal. It is found that the shielding effect contributes at energies below 88 keV. At energies above 88 keV the inaccuracy is connected with the decrease of the germanium crystal active volume, caused by lithium thermal diffusion

Applying composite fuels based on coal and finely dispersed wood in heat power engineering

Results of experimental research of thermal decomposition of composite fuels based on 2B brown coal (Borodinskoe deposit) and wastes of timber industry (finely dispersed wood) are presented. Elemental composition of researched fuels has been defined and technically analyzed. Kinetic constants have been calculated within Arrhenius model of the first order. It has been determined that with an increase of wood concentration up to 50% in composite fuel, its energy characteristics decrease by less than 2%, the maximum temperature of fuel thermal decomposition reduces by 9%, while SOx and NOx yield reduces by 50%, and fly ash – by 75%. An effective composite fuel composition of 50%/50% has been established. Results of performed experimental studies illustrate possible applications of composite fuels based on brown coal and wood at thermal power plants

Mechanical activation influence on the morphological properties of La[2]O[3]-TiO[2]-B

The influence of mechanical activation of the powder mixture used to obtain the high-perfomance cathode for accelerating engineering with the SHS-method has been explored. The mechanically processed mixtures have been morphologically analyzed. The optimal modes of mechanical activation have been determined for the mixture