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Numerical Simulations for the Optimization of the Position of the Regenerative Burner System for Tundish Preheating
No full textDETERMINING THE WORKING CHARACTERISTICS OF MECHANICALLY DRIVEN CENTRIFUGAL COMPRESSORS N-46-6
No full textThe paper presents a mathematical model and research methodology, i.e., determination of working characteristics of mechanically driven centrifugal compressors used in the process of supercharging special purpose high power diesel engines (780 HP) with intake air. A special research labor-atory installation was created for research with the aim to check and adapt compressors to the needs of the operating cycle of new or generally overhauled special purpose diesel engines. The paper provides a complete testing methodol-ogy and presents a mathematical model that can be very interesting and useful to other researchers in similar appli-cations of this compressor type. After determining the com-pressor operating characteristics on the research installa-tion, the compressor is then installed on the engine and the declared engine output parameters are monitored on a special research installation for engines
Multi-Pollutant Formation and Control in Pressurized Oxy-Combustion: SO , NO , Particulate Matter, and Mercury
No full textOxy-combustion is a promising carbon-capture technology, but atmospheric-pressure oxy-combustion has a relatively low net efficiency, limiting its application in power plants. In pressurized oxy-combustion (POC), the boiler, air separation unit, flue gas recirculation unit, and CO2 purification and compression unit are all operated at elevated pressure; this makes the process more efficient, with many advantages over atmospheric pressure, such as low NOx emissions, a smaller boiler size, and more. POC is also more promising for industrial application and has attracted widespread research interest in recent years. It can produce high-pressure CO2 with a purity of approximately 95%, which can be used directly for enhanced oil recovery or geo-sequestration. However, the pollutant emissions must meet the standards for carbon capture, storage, and utilization. Because of the high oxygen and moisture concentrations in POC, the formation of acids via the oxidation and solution of SOx and NOx can be increased, causing the corrosion of pipelines and equipment. Furthermore, particulate matter (PM) and mercury emissions can harm the environment and human health. The main distinction between pressurized and atmospheric-pressure oxy-combustion is the former’s elevated pressure; thus, the effect of this pressure on the pollutants emitted from POC—including SOx, NOx, PM, and mercury—must be understood, and effective control methodologies must be incorporated to control the formation of these pollutants. This paper reviews recent advances in research on SOx, NOx, PM, and mercury formation and control in POC systems that can aid in pollutant control in such systems
Cavitation Resistance of Laser-Sintered MS1 Steel
No full textThis study focuses on the determination of cavitation rate for samples produced by Direct Metal Laser Sintering (DMLS) of MS1 maraging steel powder without any post-processing thermal or mechanical treatment (as-built). The test samples, fabricated using an EOSINT M280 machine in a nitrogen atmosphere, were evaluated for their cavitation resistance using the ultrasonic vibration method as proposed by the ASTM G32 standard. Surface characterization to determine the duration of the experiment, as well as during and after the experiment to analyze changes in surface characteristics, was conducted using Scanning Electron Microscopy (SEM). Additionally, chemical analysis was performed using the Energy Dispersive X-ray Spectroscopy (EDS) method before and after the experiment to identify any changes and locations of significant surface damage. The mass loss of the samples over time was measured to calculate the cavitation rate. The goal of this research was to explore the potential applications of laser-sintered MS1 steel powder for manufacturing machine components and parts that are subject to cavitation erosion, due to the numerous benefits of additive manufacturing over traditional conventional technologies.Grant no. 451-03-65/2024-03/200105, Grant no. 451-03-65/2024-03/200135 and Grant no. 451-03-65/2024-03/20010
BURNING MIXTURES OF NATURAL GAS AND HYDROGEN – CHALLENGES
No full textHydrogen has been strongly proposed as one of the possible solutions to energy
transition lately. On the other hand, it is an accepted fact that fossil fuels will make up at least
50% of primary energy sources after 2050. Natural gas is considered a primary fuel that satisfies
the energy decarbonization concept to a certain level. Knowing the advantages and disadvantages
of natural gas and hydrogen, as gaseous fuels, mixtures of these two gases may appear as an
optimum solution during the energy transition period. This paper deals with the properties of
natural gas and hydrogen that affect the combustion process and burning systems. The effects
on combustion systems performance, are analyzed
CFD-Powered Ship Trim Optimization: Integrating ANN for User-Friendly Software Tool Development
No full textThis study presents a comprehensive approach to trim optimization as an energy efficiency improvement measure, focusing on reducing fuel consumption for one RO-RO car carrier. Utilizing Computational Fluid Dynamics (CFD) software, the methodology incorporates artificial neural networks (ANNs) to develop a mathematical model for estimating key parameters such as the brake power, daily fuel oil consumption (DFOC) and propeller speed. The complex ANN model is then integrated into a user-friendly software tool for practical engineering applications. The research outlines a seven-phase trim optimization process and discusses its potential extension to other types of ships, aiming to establish a universal methodology for CFD-based engineering analyses. Based on the trim optimization results, the biggest DFOC goes up to 10.5% at 7.5 m draft and up to 8% for higher drafts. Generally, in every considered case, it is recommended to sail with the trim towards the bow, meaning that the ship’s longitudinal center of gravity should be adjusted to tilt slightly forward
Impact of Nanocellulose Loading on the Crystal Structure, Morphology and Properties of PVDF/Magnetite@NC/BaTiO3 Multi-component Hybrid Ceramic/Polymer Composite Material
No full textThe hybrid multifunctional magnetic organic/inorganic composite materials, with addition of optimal filler type and quantities are attractive due to wide range of potential application, from various pressure sensors, through smart packaging, to tissue engineering and medicine. The structural, morphological and magnetic properties of polyvinylidene fluoride/nanocellulose/magnetite@BaTiO3 hybrid films were investigated. The presented study revealed significant impact of nanocellulose (NC) content on formation of the polymorphs of PVDF, responsible for ferro-, piezo- and pyroelectric properties. The structural characterization, XRD and Raman measurements confirmed enhancement of the β and γ phases when the loading of NC higher then 4 wt% in multi-component hybrid films. The saturation magnetization value gradually raises with increasing amount of NC and reaches its maximum value of 41.2 emu/g at content of 4 wt% NC. Further, addition of NC decreases saturation magnetization value regardless of constant amount of magnetite, indicating optimal content of NC substrate for co-precipitation of Fe3O4 onto NC matrix.Peer-reviewed version of the article:
[https://machinery.mas.bg.ac.rs/handle/123456789/7919
Cavitation erosion of samples based on cordierite-talc ceramics
No full textIn the paper, the cavitation resistance of cordierite samples with the addition of 10%, 15% and 20% talc, sintered at 1200ºC, was investigated. The ultrasonic vibration method with a stationary sample according to the ASTM G32 standard was applied. The formation and development of damage to the surface of the samples was monitored using a scanning electron microscope and the level of damage to the surface of the samples was quantified using image analysis. The change in the mass of the samples as a function of the cavitation time was monitored to determine the cavitation rate. By measuring the mass loss and morphological analysis of the pits formed on the surface of the sintered samples of the cordierite-talc ceramics, the mechanism of degradation and resistance to the effect of cavitation was monitored. The obtained results were compared with the results of earlier tests of cavitation resistance of sintered cordierite samples. The addition of talc in the mixture with cordierite significantly improved cavitation resistance of the sintered material compared to sintered pure cordierite. The tests were done to see the potential application of this material in hydrodynamic conditions, especially because of the strong corrosion resistance of these refractory materials
ГУБИТАК ЕНЕРГИЈЕ НА РЕШЕТКАМА
No full textВодозахвати пумпних постројења (водоводи, постројења за пречишћавање
отпадних вода, итд.) и хидроелектрана поседују решетке за спречавање уласка отпадних материја у проточни тракт постројења. Правилним: избором, конструисањем, одређивањем губитка и одржавањем решетке, знатно се утиче на енергетску ефикасност хидро постројења.
Локални губитак на решеткама је један од важних параметара при пројектовању пумпних и
турбинских постројења. Постоји већи број емпиријских израза различитих аутора за
одређивање губитка енергије на решетки. У раду је извршена упоредна анализа 10 израза, на
основу којих су одређени губици за решетку са кружним и решетку са правоугаоним обликом
профила шипки. Губици су одређени за углове нагиба решетке од: 90°, 45°, 35°, 25° и 15° и
брзине дострујавања воде од: 0,3; 0,5; 0,7; 0,9 и 1,1 m/s. Уочавају се одређена одступања
добијених резултата. Пошто се вредност губитка не решетки најпоузданије одређује
моделским испитивањем, приказано је и идејно решење инсталације за хидрауличка
испитивања у каналу са променљивим нагибом у лабораторији Катедре за хидрауличне
машине и енергетске системе, Машинског факултета.[https://ieep-2024.drustvo-termicara.com/content/files/c43d337.pdf
RAREFIED GAS FLOW IN CONVERGENT AND DIVERGENT MICROTUBE
No full textAn axisymmetric stationary isothermal flow of a rarefied gas through convergent and
divergent microtubes of circular cross-section was considered. The gas flow is
compressible, subsonic and occurs at moderately high values of the Reynolds number.
The flow is caused by the pressure difference between the inlet and outlet of the
microtube. As flow through micropipes is considered, rarefaction is included. Low
rarefied gas flows are examined, which implies low values of the Knudsen number - slip
gas flows. In this flow regime boundary conditions of gas slip on the wall for the velocity
field are applied. To reduce the dimensional system of equations (continuity, NavierStokes, equation of state of an ideal gas) to a form suitable for solving, it is necessary to
introduce appropriate reference quantities, reference dimensionless numbers and
assumptions based on the flow model. Also using a perturbation approach, velocity
components and pressure are expressed in the form of a perturbation series. The first
term in the perturbation series represents the continuum, while the second term
represents the influence of slip and inertia. It is shown that rarefaction decreases the
pressure along the microtubes, regardless of their geometry. The highest ratio of inlet
and outlet pressure is required for divergent microtubes, and the smallest ratio is
required for convergent microtubes. It is revealed that the presence of inertia increases
the pressure along the microtubes, for all considered geometries