Improvement of the Cargo Fleet Vessels Power Plants Ecological Indexes by Development of the Exhaust Gas Systems

Modernisation of the power plants of cargo fleet vessels to satisfy the requirements set out by the International Maritime Organisation is an urgent scientific and technical problem. The article presents the results of developing a solution to this problem that focuses on the exhaust gas system. We propose the use of ejection nozzles as part of this system. It was found that when the ejection coefficient in these nozzles is n = 3, it is possible to exclude the use of SCR reactors, thus reducing the operating costs of the marine power plant. Using a mathematical modelling method, the efficiency of operation of six types of nozzle as part of the exhaust gas system was investigated, and a constructive layout was proposed for the gas ducts and inlet louvres for supplying ambient air. To increase the efficiency of the proposed system, we consider several options for intensifying heat transfer processes through the use of dimple systems in the nozzles and nozzles with swirling flow. We found that these technical solutions would make it possible to further increase the efficiency of the systems by up to 19% abs.

Rationale for vacuum-pulse pump devices applied on cattle farms

One of the main elements to foster technological processes in animal husbandry are vacuumpulse pump devices designed to support dosing, mixing, transporting, lines for forage preparation and feeding, milking cows, milk processing, as well as a large number of technological processes in agriculture. The paper discusses a vacuum-pulse pumping device widely used in all industries and agriculture, a feature of which is to improve technical characteristics of the pump avoiding direct mechanical energy consumption and boasting a fairly simple design. In vacuum-pulse pumping devices, transient events are caused deliberately to increase ejection coefficient, productivity, etc. Oscillating flows of materials being transported are very diverse, due to an increased number of similarity criteria that determine flow patterns. Whereas superficial velocity and the Reynolds number are commonly used for a steady flow, for an oscillating flow, the relative frequency and the relative amplitude of oscillations are added. The objects of experimental research were ejectors with oscillating flows. The wider objective of the experiments was to determine the most effective performance indicators of the ejectors, including the degree of pressure increase, the ejection coefficient and the geometric parameter. Resulting from the experiments, a direct relationship was established between changes in the performance of a pulse-vacuum pumping device and valve material and magnitude of its oscillations. A pulse ejector is recommended to have metal-seated ball valves with a pulsation frequency of 90–100 min−1. Once applied, the proposed pulse ejector will eventually increase the transportation productivity by 14.5 %.

A study of flow characteristics in a low-pressure ejector installation

Production processes sometimes are accompanied by the release of hazardous substances, the composition and volume of which is determined by the production technology. When designing ventilation systems for paint departments, special attention is paid to safety concerns, since all paint coatings are corrosive and flammable substances. Besides, solvent vapors are explosive. For local ventilation of painting chambers, it is rational to use safe exhaust systems with an ejector, which works sturdily, regardless of the release of flammable and explosive impurities. The ejector is simple in design and can operate in a wide range of changes in the parameters of the state of airflow. The model of the ejection unit is synthesized using the universal modeling package ChemCad, which contains a highly developed database of airflow parameters, which allows for solving various applied problems. Numerical modeling was carried out using the software package - FLUENT. In work, a calculation was carried out and a low-pressure ejector was designed for a typical painting booth. The calculation results are presented in the form of graphs and tables of pressures, velocities, flow rates in characteristic sections, pressure losses in the sections of the ejector installation.The ejection coefficient was also calculated.

RESEARCH RESULTS OF THE IMPROVED HYDRAULIC JET PUMPING UNIT

The scientific article is aimed at substantiating the classification of hydraulic jet pumping units, developing an experimental model of an improved hydraulic jet pumping unit, conducting experimental studies - determining the useful flow Qгн depending on the flow rate of the centrifugal pump used Qн for two variants of the pumping unit operating according to the traditional and alternative technology of water lifting, determination of the head losses hснi and friction coefficients ξснi in jet pumps, increasing the ejection coefficient Ke from the swirl parameter S of water supply to the intake chamber of the jet pump and laboratory tests of the hydraulic jet pumping unit for agricultural water supply and irrigation of pastures. The results of experimental studies and laboratory tests of an experimental model of an improved water-jet pumping unit, developed at NAO KazNAU, are presented. An analysis is given of the results of comparative tests of a hydraulic jet pumping unit for two variants of the technological process: an alternative and a traditional one with an increase in the effective supply of an alternative option by 2-4 times, a decrease in the required pressure by 1.5-2 times and an increase in efficiency by 1.1-2 times. The aim of the study is to obtain results to substantiate the classification of hydraulic jet pumping units, to carry out experimental studies and laboratory tests of an improved hydraulic jet pumping unit operating according to an alternative water lifting technology, which allows to reduce the required head of the pumping unit, increase the useful flow and increase the efficiency of the improved hydraulic jet pumping unit. The work used patent research with a review of works that were carried out according to existing methods: identifying close analogues, analyzing existing works and using them in development. Experimental studies were carried out to study the technological process of water rise from wells, the processes occurring in the used jet pumps - determining the useful flow depending on the flow of a centrifugal pump, determining the pressure losses and friction coefficients in jet pumps, the ejection coefficient and checking the reliability of the theoretical assumptions obtained. Based on the analysis of the work performed and patent research on technologies for lifting water from underground water sources by hydraulic jet pumping units and designs developed for them, a substantiated classification of hydraulic jet pumping units is proposed, which allows, depending on the task at hand, to correctly choose the necessary structural and technological scheme, type of jet pump and its implementation in the development of the required effective standard sizes of the hydraulic jet pumping unit. The scheme of the test bench and the experimental model of the improved hydraulic jet pumping unit with measuring equipment and instruments for conducting experimental research and laboratory tests on a bench well is presented.

NUMERICAL MODELING AND EXPERIMENTAL RESEARCH OF A LIQUID-LIQUID EJECTORS WITH A CURVED INITIAL MIXING CHAMBER AREA AND WITH DIRECT MIXING CAMERA

The article presents the results of numerical simulations and experimental studies of a liquid-liquid ejector with a curved initial portion of the mixing chamber. The experiment was conducted on liquid-liquid ejectors, models of which are made on a 3D printer, by the method of layer-by-layer deposition. The influence of possible manufacturing errors of the ejector on its characteristics is estimated. The issues of the use of liquid ejectors designed to work in the field of various predetermined ejection coefficients are considered. The theoretical ejection coefficient and the reasons for reducing the ejection coefficient in real ejectors are determined. The obtained dependences make it possible to determine the optimal design parameters of a liquid ejector and thereby increase its ejection coefficient. The relative pressure drop is shown at a low coefficient and at a high ejection coefficient. The calculated and experimental results of determining the ejection coefficient for liquid ejectors, which are widely used in various fields of technology, are presented. The results of numerical simulation of internal processes in the ANSYS-Fluent hydro-gasdynamic application package flowing in a single-phase liquidliquid ejector based on the study of a small-sized model are presented. As a result of the simulation, a good agreement was obtained between the calculation results of the model corresponding to the real prototype and the experimental data and comparison with the results of other authors. Several conclusions can be drawn from the results of the study. For example, a region of values of the ejection coefficient was found in which the relative pressure drop created by the ejector increases with an increase in the ejection coefficient.

АНАЛІЗ ЕФЕКТИВНОСТІ ТЕПЛОВИКОРИСТОВУЮЧОЇ ТЕРМОПРЕСОРНО-ЕЖЕКТОРНОЇ ХОЛОДИЛЬНОЇ МАШИНИ

One of the ways to increase the energy efficiency of ejector refrigerating machines is to use of thermopressor technologies, which are based on to use of the process of thermogasdynamic compression. This process consists in contact cooling and at the same time increasing the gas or steam pressure. The thermopressor application in the ejector refrigerating machines cycle installed at the outlet of the ejector, allows, by increasing the pressure during vapour contact cooling to a saturation tempera-ture, to increase the ejection coefficient U and, accordingly, the thermal coefficient z. A number of refrigerants were chosen for analysis of cycle of ejector refrigerating machines, among which those traditionally is used for ejector refrigerating ma-chines, and a number of other refrigerants that can be used in ejector refrigerating machines based on the possibility of using the thermopressor. It is possible to in-crease the ejector refrigerating machines efficiency by using the thermopressor while ensuring a greater temperature difference. With the temperature difference 60–100 oC, the relative pressure increase is mostly positive. The following refrigerants have the most significance: R717, R134a, R227ea, R1234ze(E), R1234yf. Analysis of the ejector refrigerating machines scheme by using the thermopressor shows that the greatest efficiency at the highest possible boiling points in the generator tg is the refrigerants: R142b, R600, R1233zd(Е), R245fa.

Experimental Investigation and Numerical Simulation of Gas Ejector in a Combustor With Combustion Gases Recirculation

Sets of high-pressure ejection experiment were conducted to investigate the implementing of gases ejector with high-pressure condition. Numerical simulation was used to extend the study and overcome the limit of experiment facilities. Experiment shows that ejection coefficient of gases ejector was not sensitive to supply gas pressure changes. But which was affected greatly by backpressure in mixing cavity of ejector, as shown by simulation. The simulation result also implies that there are inherent relation between ejection coefficient, area ratio at inlet of mixing cavity and pressure different between supply gas pressure and the backpressure. And the relationship determines that in some range, the implementing of gas ejector was unstable.