Vol 52, No 9-10 (2017)

The objective of the study is to determine the effect produced by the design parameters of the elements of the flow-through part of an inertial vacuum dust collector on the efficiency of dust collection. Numerical experiments are conducted in the ANSYS CFX shell and these reveal a substantial dependence of the efficiency of the plant on the height of the divider and the length of the inlet pipe.

The problems of enhancing the efficiency of screw refrigeration compressors with speed control of refrigeration output are studied. Based on a mathematical model developed, it is demonstrated that compressor efficiency depends a great deal on the operation of the oil injection system. When an oil injection system that ensures optimal compressor operation under fixed conditions is chosen, change in operation conditions does not cause significant loss of efficiency. At the same time, if the oil injection system is non-optimal, change in operation conditions does not enhance compressor efficiency. This means that the configuration of the oil injection system determines the level of compressor efficiency, which remains practically unchanged if the operation conditions are changed.

The functioning of sections of a gas transporting system through which the gas is transported at low pressure with reduced compression ratio (compared to the rated ratio of 1.44) at compressor stations is analyzed. The results of assessment of energy efficiency indices of these sections of the gas transporting system for two options, namely, with replacement of flow passage (RFP) in centrifugal compressors of GPA-Ts-16 gas pumping units and without replacement of flow passage (as at present) are presented. The influence of technological risks on the indices is assessed. The results of the study have provided economic criteria that allow confirmation of the expediency of the steps taken for replacing flow passages of centrifugal gas compressors of the studied sections of the gas transporting system with reduced pressure ratio.

Results of a verification of a numerical technique for investigating the hydrodynamic characteristics of gases and liquids in the gap of metal-polymer sliding friction bearing assemblies that function in a dry friction regime are presented. The results of a comparison of numerical and experimental investigations confirm that the numerical technique used in engineering calculations is correct with error not greater than 10%.

An experimental study has been made of transformation of surface of drops of liquids used widely in chemical engineering (water, kerosene, and ethyl alcohol) during their motion in air with moderate velocities (up to 5 m/sec). The initial sizes (nominal diameters) of the drops varied in the 3–6 mm range. The typical “cycles of deformation” of liquid drops with specific duration, length, and amplitudes of size variation have been established. More than 10 successive deformations during 1-m passage of liquid drops through the air are investigated. The typical time of transition from one drop shape to another is determined. Two deformation conditions differing in drop shapes and time of the respective transition are distinguished.

Questions related to modeling of physicochemical processes in the interaction of sulfurous shale with an ash-based heat-transfer agent under low-temperature carbonization conditions in a drum reactor with solid (ash-based) heat-transfer agent are considered. Combustible gas, resinous substances, and semicoke are the basic products of low-temperature carbonization. Through use of these products, it is possible to expand the raw material base of enterprises in the chemical, energy, and construction industries. The results in the article are illustrated by concrete numerical calculations and are complemented with an analysis of the results obtained.

Studies of the hydrodynamics, mass exchange, and growth of active silt on two versions of a new type of gauze packing under fluidized conditions are conducted. Computational equations for determining the masstransfer coefficients in the liquid phase are obtained. It is found that Type IIM volumetric fluidized gauze packing is the more promising type of packing, and this version is recommended for use in bioscrubbers for the purpose of cleaning vent gases of organic matter.

An apparatus and method for isotopic analysis of ³He/⁴He for controlling the extraction of ³He from natural He were designed using a commercial industrial mass spectrometer. A modernized sample-injection system allowed the sample volume of rare and expensive gases for quantitative and isotopic analyses to be reduced by 3–5 orders of magnitude. The metrological characteristics of the developed analytical method including sampling and injection into the mass spectrometer were evaluated using model analyses of individual isotopes of Ar, Ne, and He.

On the basis of a modernized theoretical model, the effect of external action on the micro-inhomogeneous structure of liquid metal technology is developed for combined treatment of heat-resistant steel with modification by vibration. Steel manufacturing adaptability is improved as a result of introducing this technology.

Studies of the development of methodological bases for synthesizing polytetrafluoroethylene modified with detonation nanodiamonds using ultrasonic irradiation of a composite mixture during pressing determined the optimal modes of ultrasonic irradiation. Polytetrafluoroethylene modified with detonation nanodiamonds (0.5 wt.%) had the best combination of strength and tribological properties. The wear resistance of the developed material increased by 15.8% whereas the coefficient of friction decreased by 13.6%.

Regularities of medium-temperature nonoxidizing pyrolysis of oily waste at a municipal solid-waste utilization installation are investigated. Dependences of the pyrolysis time on the reference loading temperature of oily wastes and their weight and moisture content are found. It is shown that the hazard class of waste at this installation decreases from high to low as a result of pyrolysis.

The article analyzes conditions, causes of breakdown, and the main types of corrosion of elements exposed to the greatest wear, and also the classification of breakdowns using oil with different composition in the boilers of the most common designs. Recommendations are made aimed at improving operational reliability and data are provided optimizing planned and preventive boiler maintenance.

Uneven rotation of the bottom hole drill stem assembly (BHA) and the drill string is a source of torsion shocks that create high-frequency and high-amplitude vibration. A correlation between torsional and lateral vibrations is discovered. An analysis demonstrates that an increased vibration load on the drill string and the bottom hole drill stem assembly leads to a decrease in the mechanical on-bottom drilling rate and premature wear of equipment. A suitable selection of all the elements of BHA that takes into account the possibility that different types of vibrations may arise and an adjustment of the drilling parameters (bit load, rotational speed) together lead to an increase in the drilling rate, the reliability of the drilling equipment, and a decrease in the time needed to construct the well. Real-time monitoring for shocks, vibrations, and stick-slip will help to increase the precision of estimates of the state of downhole equipment.

Conditions are studied for the effect of carbonate ions on steel corrosion in relation to pH and temperature, and reasons are revealed for an increase in steel corrosion activity in the presence of CO2 and carbonate-ions.