Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Computational Fluid Dynamics Study of Biomass Moisture Content Impact on Particle Matter Emissions
No full textWood combustion is a significant energy source, but it also contributes to air pollution due to the emission of gaseous and particle matter. Understanding the formation and behaviour of gaseous and particle emissions is crucial for environmental and health concerns. To simulate and analyse beech wood combustion, a mathematical model for computational fluid dynamics (CFD) simulation was developed. This model considered various parameters such as fuel properties, combustion kinetics, and fluid dynamics. The model enables the prediction of temperature profiles, species concentrations, and soot particle emissions. To validate the accuracy of the CFD model, experimental measurements were conducted on an actual beech wood combustion setup. The experimental data, including flue gas temperature, CO2 and CO concentrations, and soot particle measurements, were compared with the simulation results. The validation process was aimed to ensure the reliability and fidelity of the CFD model for predicting beech wood combustion behaviour. Furthermore, a parametric analysis was performed using the validated model to investigate the influence of different moisture content levels in the fuel on the combustion process and emission characteristics. The moisture content varied from 10 to 40%, representing a range of realistic conditions. The results of the parametric analysis provided insights into the relationship between moisture content and combustion performance. The findings contributed to optimizing beech wood combustion processes, improving energy efficiency, and reducing emissions. The study emphasized the importance of considering moisture content as a critical parameter in designing and operating wood combustion systems to achieve sustainable and environmentally friendly practices. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Contract no.451-03-47/2023-01/20010
NUMERICAL SIMULATION OF ISOTHERMAL RAREFIED GAS FLOW BETWEEN TWO PLATES
No full textpo Ugovoru 451-03-136/2025-03/ 200105 оd 04.02.2025. god
Unsteady Fluid-Structure Interaction Characteristics of a Reversible Mixed-Flow Pump in Micro-Pumped Hydro Storage
No full textThe reversible mixed-flow pump (RMFP) is widely employed in micro-pumped hydro storage to efficiently meet the energy storage and generation demands of microgrids. However, frequent switching between operational conditions intensifies the fluid–structure interaction effects
in RMFP, leading to operational instability and blade fatigue damage. In this paper, the unsteady flow and dynamic characteristics of RMFP in pump and turbine modes are systematically investigated through numerical simulation and experimental verification. Comprehensive
comparative analysis was conducted on the pressure distribution, radial force, as well as the deformation and stress distribution at different locations of the impeller blades under various operational conditions in both pump and turbine modes. The results show that: In pump
mode, the pressure distribution on the blade’s pressure side is uniform, while in turbine mode, a localized high-pressure region forms at the inlet under high head condition (9 m). Significant fluctuations in radial force are observed under low flow rate pump condition (0.8Qd). The
maximum deformation of the impeller is 0.1236mm in pump mode under low flow rate condition (0.8Qd) and 0.184mm in turbine mode under high head condition (9 m). Equivalent stress concentrations predominantly are observed at the blade inlet in turbine mode and the
blade outlet in pump mode, with significant stress accumulation at the hub-bearing connection. These findings provide valuable insights for the operational stability of the RMFP rotor system and offer guidance for the structural optimization of impeller blades
Efficiency Assessment of a High-Speed Tracked Vehicle Hybrid Powertrain
No full textThe paper analyzes the difference in power balance and efficiency between a modernized, hybrid high-speed tracked vehicle powertrain model and a mechanical powertrain model corresponding to the real vehicle developed and verified in previous research. This is to prove the argument of the efficiency benefits of electrifying the vehicle turning mechanism and eliminating the friction elements slip. The simulation models of both powertrains presented in this paper are subjected to the same simulation conditions, with the powertrain design solutions being the only variables. The results presented show that the vehicle with a hybrid powertrain achieves the required turning radius about four seconds earlier, with about 50 % less internal combustion engine (ICE) power required for the analyzed working regime. The hybrid powertrain offers an infinite number of calculated turning radii within the range of electric motor rpm, instead of one calculated
turning radius in an existing powertrain. This results in a reduction in the total power required for the turning process as there are no losses due to friction element slip
TRANSIENT MODELING OF IMPINGING HEAT TRANSFER FROM AN ACOUSTICALLY MODULATED TURBULENT AIR JET TO A NORMALLY POSITIONED FLAT SURFACE
No full textThe subject of this study is the numerical investigation of the impingement of an axisymmetric turbulent air jet on a flat surface, the influence of acoustic modulations on the coherent structures that form around the jet, and the effects on the heat transfer from the jet to the heated surface. The study showed how controlled acoustic perturbations influence the exit velocity profile from the nozzle and the formation of vortices in the boundary-layer of the jet. Since vortices are responsible for the redistribution of thermal energy transferred from the jet to the surface in impinging jet flow configurations, it is crucial to investigate whether their for-mation and evolution can be controlled. The results of the numerical simulations indicated very good agreement with experimentally measured velocity field. How-ever, a problem arises in the prediction of the heat transfer because the standard k-ε model overestimates the values of the heat transfer coefficient in the stagnation zone because they were theoretically developed to use shear stresses for the gen-eration of the turbulent kinetic energy, while in reality normal stresses are responsible for their generation in this flow situation. Due to the unstructured mesh used for the calculations, there are discrepancies in the results at larger edge distances. The complex flow at the impingement surface, the occurrence of secondary vortices and re-circulation zones and their direct effect on the heat transfer cannot be fully captured by the mathematical model, even if the numerical errors are acceptable compared to experiments
FARADEJEV KAVEZ OD GRAFENA
No full textOvaj pronalazak se odnosi na Faradejev kavez izrađen od grafena. Grafen se koristi kao osnovni materijal zbog svoje visoke električne provodljivosti, mehaničke čvrstoće i fleksibilnosti. Faradejev kavez od grafena pruža efikasnu zaštitu od elektromagnetnih talasa, dok je znatno lakši i fleksibilniji od tradicionalnih metalnih kaveza. Grafen može biti korišćen u obliku jednog sloja ili više slojeva, a slojevi grafena odnosno ploče grafena koje naležu jedna na drugu celokupnom svojom površinom mogu biti spojene termički, elektrohemijski, laserski, ultrazvučno, polimerno ili na drugi pogodan način koji ne ugrožava čvrstoću kaveza i ne narušava električnu provodljivost kaveza. Grafenske ploče se mogu spajati po ivicama pomoću tehnika kovalentnog vezivanja, termičkog zavarivanja, provodljivog lepka, leksibilnih provodnih traka i na drugi pogodne načine kako bi se formirala kontinuirana stabilna i provodna struktura. Ovaj kavez se može koristiti u različitim industrijskim, medicinskim, telekomunikacionim, vojnim aplikacijama, kao i za zaštitu osoblja i opreme u rudarskim i istraživačkim okruženjima.Contract no. 451-03-47/2023-01/20010
Mašine alatke i roboti nove generacije
No full textMašine alatke i roboti nove generacije je izborni predmet na modulu za proizvodno mašinstvo na 1. godini Master akademskih studija Mašinskog inženjerstva (MAS-MI). Sadržaj knjige je koncipiran prema sadržaju predmeta koji je sistematizovan u 9 tematskih oblasti. Prvo poglavlje prikazuje kratak osvrt na istoriju i budućnost mašina alatki i robota. Obuhvata definicije i klasifikacije mašina alatki i robota, kao i kriterijume na osnovu kojih se izdvajaju mašine alatke i roboti nove generacije.
Drugo poglavlje polazeći od osnovnih pojmova modularnosti i rekonfigurabilnosti prikazuje rekonfigurabilne i prilagodljive mašine alatke i tehnološke sisteme.
U trećem poglavlju se razmatraju obradni sistemi za obradu velikim brzinama. Navode se primene i prednosti ovakvih obradnih sistema. Razmatra se tipičan predstavnik obradnog sistema za obradu glodanjem velikim brzinama. Četvrto poglavlje prikazuje definicije procesa brze izrade prototipova i klasifikaciju procesa sa dodavanjem materijala. Daju se primeri mašina za procese sa dodavanjem materijala, kao i primeri primene tih mašina. Peto poglavlje razmatra mašine alatke i robote sa paralelnom kinematikom kroz definicije, klasifikacije i mogućnosti primene. Dato je
i kinematičko modeliranje paralelnih mehanizama koje obuhvata rešavanje
i
Mašine alatke i roboti nove generacije
inverznog i direktnog kinematičkog problema, određivanje Jakobijan matrice
i analizu radnog prostora. Šesto poglavlja obuhvata mašine alatke za višeosnu obradu. Pokazuju
se primeri mašina alatki za višeosnu obradu glodanjem i analiziraju mogućnosti njihovog programiranja. Sedmo poglavlje prikazuje obradne sisteme za višeosnu obradu na bazi
robota kroz njihovo kinematičko modeliranje i analizu sistema upravljanja i programiranja.
Osmo poglavlja razmatra mikrotehnologije i adekvatne mašine alatke za te tehnologije, kao predstavnike nove generacije mašina alatki za mezo i mikroobradu. Deveto poglavlje kroz prikaz aktivnih nosećih struktura mašina alatki, primere etalona i primere kompenzacija u obradnom sistemu obuhvata mašine alatke visoke tačnosti.Рецензенти: др Бранко Кокотовић, ванредни професор и др Слободан Табаковић, редовни професор
За издавача: Декан, проф. др Владимир Поповић
Главни и одговорни уредник: проф. др Небојша Манић
Одобрено за штампу одлуком Декана Машинског факултета у Београду бр. 1/2025 од 20.02.2025. године
Штампа: Birograf comp doo, Београд
Тираж: 120 примерака
COBISS.SR-ID 16593383
Molecular “Yin-Yang” Machinery of Synthesis of the Second and Third Fullerene C60 Derivatives
No full textTo overcome the negative effects of the biochemical application of nano-substances in medicine (toxicity problem), using the example of fullerene C60’s first derivative (fullerenol, FD-C60), we show that their biophysical effect is possible through non-covalent hydrogen bonds when around FD-C60 water layers are formed. SD-C60 (Zeta potential is −43.29 mV) is much more stable than fullerol (Zeta potential is −25.85 mV), so agglomeration/fragmentation of the fullerol structure, due to instability, can cause toxic effects. When fullerol in solution was exposed to an oscillatory magnetic field with Re (real) part [250/−92 mT, H(ωt) = Acos(ωt)], water layers around FD-C60 (fullerenol) are formed according to the Penrose process of 3D tiling formation, and the second derivative, SD-C60 (or 3HFWC), is self-organized. However, when Im (imaginary) part [250/−92 mT, H(ωt) = Bisin (ωt)] of the external magnetic field is applied in addition to SD-C60, ordered water chains and bubbling of water (“micelle”) are formed as a third derivative (TD-C60). Fullerol (FD-C60) interacts with biological structures biochemically, while the second (SD-C60) and third (TD-C60) derivatives act biophysically via non-covalent hydrogen bond oscillation. SD-C60 and TD-C60 significantly increased water solubility and reduced toxicity. The paper explains the synthesis of SD-C60 and TD-C60 from FD-C60 (fullerol) as a precursor by the influence of an oscillatory magnetic field (“Yin-Yang” principle) on hydrogen bonds in order to create water layers around fullerol. Examples of biomedical applications (cancer and Alzheimer’s) of this synergetic complex are given. This study shows that the “Yin-Yang” machinery, based on the nanophysics of C60 molecules and non-covalent hydrogen bonds, is possible. The first attempt has been composed to synthesize nanomaterial for biophysical vibrational nanomedicine
Extension of the Throughflow Solver for Predicting the Aerodynamic Performance of Fans with Inlet Distortion
No full textNext-generation aircraft with boundary layer ingesting (BLI) engines can reduce fuel consumption but pose challenges for fan and compressor operation due to inlet distortion. To optimize the design of such engines, it is essential to assess the impact of non-uniform inlet flow on stability and performance, with the final result of a distortion-tolerant machine. One of the first steps in this process is estimating the aerodynamic performance using fast but reliable mathematical models. This paper presents an extension of the existing throughflow solver that predicts the effects of the upstream distortion. The proposed method, based on the parallel compressor theory, introduces multiple planes to accurately define and track the circumferential distribution of parameters as they advance through the machine. It applies to all types of distortion: total pressure, total temperature, and swirl. The model is demonstrated for a high-pressure, low hub-to-tip diameter ratio fan with nonuniform total pressure at the inlet. Flow physics associated with distortion is analyzed using results from full annulus unsteady RANS simulations for three operating points: near stall, design, and near choke. The flow field results are compared with the CFD data at the design point. The overall performance is evaluated against a clean inlet case
Optimal Trajectory Tracking of Robot Manipulator Using Resonant Controller
No full textControlling robotic manipulators remains a challenging research area due to their complex, nonlinear, and coupled dynamics [1]. Numerous tracking control methods have been proposed, particularly for tasks requiring repeated execution of closed trajectories in three-dimensional (3D) space - common in industrial applications like welding and painting. While resonant controllers are widely used in electrical systems, their potential in robotics has been largely overlooked. These controllers offer a key advantage: a structural term aligned with the fundamental frequency of the target trajectory. This paper proposes integrating a resonant controller with a particle swarm optimization (PSO) algorithm to minimize tracking error. The main contribution is the novel combination of PSO and resonant control for improved motion accuracy.No. 451-03- 137/2025-03/200105 from 4.2.2025