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Keywords = Laval rotor

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20 pages, 5489 KiB  
Article
Probabilistic Analysis of Orbital Characteristics of Rotary Systems with Centrally and Off-Center Mounted Unbalanced Disks
by Zdenko Šavrnoch, Milan Sapieta, Vladimír Dekýš, Barbora Drvárová, Katarína Pijáková, Alžbeta Sapietová and Milan Sága
Appl. Sci. 2024, 14(19), 8810; https://doi.org/10.3390/app14198810 - 30 Sep 2024
Viewed by 1100
Abstract
Rotor dynamics plays a crucial role in the performance and safety of rotating machinery, with disk position and unbalance significantly impacting system behavior. This study investigates the dynamic characteristics of two rotor configurations: a centrally mounted unbalanced disk (Rotor05un) and an off-center unbalanced [...] Read more.
Rotor dynamics plays a crucial role in the performance and safety of rotating machinery, with disk position and unbalance significantly impacting system behavior. This study investigates the dynamic characteristics of two rotor configurations: a centrally mounted unbalanced disk (Rotor05un) and an off-center unbalanced disk (Rotor025un). Using numerical simulations and Monte Carlo analysis, we examined critical speeds and orbital patterns for both configurations. Probability distributions of shaft orbital positions revealed distinct patterns for each configuration. Quantile analysis revealed approximate linear trends for Rotor025un, suggesting higher system stiffness and more predictable behavior near critical speeds. Cross-sectional analyses of the orbits provided insights into the complex interactions between disk position, gyroscopic effects, and system natural frequencies. These findings provide valuable insights for rotor system design, particularly for applications with non-ideal mass distributions. The study goes beyond traditional critical speed analysis to examine orbital patterns and point on orbit occurrence from a probabilistic perspective. Based on the simulation of the orbits, an orbital is determined that allows the probability of the shaft occurring at the analyzed distance from the origin to be determined. The paper also offers insights into the complex interaction behavior of chosen rotor configurations and highlights the importance of considering disk position in predicting and optimizing rotor dynamic behavior, contributing to the development of more robust and efficient rotating machinery. Full article
(This article belongs to the Section Mechanical Engineering)
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16 pages, 15529 KiB  
Article
Probabilistic Analysis of Critical Speed Values of a Rotating Machine as a Function of the Change of Dynamic Parameters
by Zdenko Šavrnoch, Milan Sapieta, Vladimír Dekýš, Petr Ferfecki, Jaroslav Zapoměl, Alžbeta Sapietová, Michal Molčan and Martin Fusek
Sensors 2024, 24(13), 4349; https://doi.org/10.3390/s24134349 - 4 Jul 2024
Cited by 2 | Viewed by 1261
Abstract
Real-world rotordynamic systems exhibit inherent uncertainties in manufacturing tolerances, material properties, and operating conditions. This study presents a Monte Carlo simulation approach using MSC Adams View and Adams Insight to investigate the impact of these uncertainties on the performance of a Laval/Jeffcott rotor [...] Read more.
Real-world rotordynamic systems exhibit inherent uncertainties in manufacturing tolerances, material properties, and operating conditions. This study presents a Monte Carlo simulation approach using MSC Adams View and Adams Insight to investigate the impact of these uncertainties on the performance of a Laval/Jeffcott rotor model. Key uncertainties in bearing damping, bearing clearance, and mass imbalance were modeled with probabilistic distributions. The Monte Carlo analysis revealed the probabilistic nature of critical speeds, vibration amplitudes, and overall system stability. The findings highlight the importance of probabilistic methods in robust rotordynamic design and provide insights for establishing manufacturing tolerances and operational limits. Full article
(This article belongs to the Section Physical Sensors)
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24 pages, 6864 KiB  
Article
Optimization of Flywheel Rotor Energy and Stability Using Finite Element Modelling
by Daniel Coppede, Fabio da Silva Bortoli, Joao Manoel Losada Moreira, Nadja Simao Magalhaes and Carlos Frajuca
Energies 2024, 17(12), 3042; https://doi.org/10.3390/en17123042 - 20 Jun 2024
Cited by 2 | Viewed by 1615
Abstract
An investigation on a flywheel is presented based on finite element modelling simulations for different geometries. The goal was to optimise the energy density (rotational energy-to-mass ratio) and, at the same time, the rotational energy of a flywheel rotor. The stress behaviour of [...] Read more.
An investigation on a flywheel is presented based on finite element modelling simulations for different geometries. The goal was to optimise the energy density (rotational energy-to-mass ratio) and, at the same time, the rotational energy of a flywheel rotor. The stress behaviour of flywheel rotors under the rotational speed at the maximum stress achievable by the flywheel was analysed. Under this condition, the energy density was obtained for the different geometries, as well as the rotational energy. The best energy density performance due to geometry was achieved with a flywheel rotor presenting a new Gaussian section, which is different from the known Laval disk shape. The best results using a single disk involved a rotational speed of nearly 279,000 rpm and a rotational energy density around 1584 kJ/kg (440 Wh/kg). These values still yielded low total energy; to increase its value, two or three rotors were added to the flywheel, which were analysed in regard to stability. In particular, the triple rotor energy density was ≈ 1550 kJ/kg (431 Wh/kg). As some instability was found in these rotors, a solution using reinforcement was developed to avoid such instabilities. The energy density of such a reinforced double rotor neared 1451 kJ/kg (403 Wh/kg), and the system achieved higher total energy. The material assumed for the devices was carbon fibre Hexcel UHM 12,000, a material kept constant throughout the simulations to allow comparison among the different geometries. Full article
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19 pages, 10055 KiB  
Article
Real Fluid Modeling and Simulation of the Structures and Dynamics of Condensation in CO2 Flows Shocked Inside a de Laval Nozzle, Considering the Effects of Impurities
by Harshit Bhatia and Chaouki Habchi
Appl. Sci. 2023, 13(19), 10863; https://doi.org/10.3390/app131910863 - 29 Sep 2023
Cited by 2 | Viewed by 1777
Abstract
Because of the currently changing climate, Carbon Capture and Storage (CCS) is increasingly becoming an important contemporary topic. However, this technique still faces various challenges. For the compression of CO2 to its supercritical condition for efficient transport, one of the important challenges [...] Read more.
Because of the currently changing climate, Carbon Capture and Storage (CCS) is increasingly becoming an important contemporary topic. However, this technique still faces various challenges. For the compression of CO2 to its supercritical condition for efficient transport, one of the important challenges is mastering the two-phase flow in the pump. Indeed, phase changes that appear on the blade tips of an impeller or rotor in such pumps can lead to performance and stability issues. Moreover, these phase change phenomena (vaporization and condensation) can be significantly modified by the presence of impurities (N2, O2, H2S, etc.) whose nature depends on the source of the CO2 production. In this work, we focus on analyzing the high pressure flow behavior of CO2 mixed with varying levels of impurities in a de Laval nozzle, for which experimental results are available. Numerical simulations are performed using a real-fluid model (RFM) implemented in the CONVERGE CFD solver. In this model, a tabulation approach is used to provide the thermodynamic and transport properties of the mixture of CO2 with the impurities. The study is carried out with different inlet conditions, and the results are in good agreement with the available experimental data. In addition, the results provide insights on the interaction of the shock wave with the observed condensation phenomenon, as well as its impact on the amount of condensation and other thermodynamic variables. The research indicates that the presence of impurities mixed with CO2 significantly affects the observed condensation in gas streams, which is a crucial factor that cannot be overlooked when implementing CCS systems. Full article
(This article belongs to the Special Issue Multiscale Modeling of Complex Fluids and Soft Matter)
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14 pages, 2020 KiB  
Article
Rotordynamic and Friction Loss Measurements on a High Speed Laval Rotor Supported by Floating Ring Bearings
by Rob Eling, Mathys Te Wierik, Ron Van Ostayen and Daniel Rixen
Lubricants 2017, 5(1), 7; https://doi.org/10.3390/lubricants5010007 - 15 Mar 2017
Cited by 7 | Viewed by 5770
Abstract
Floating ring bearings are the commonly used type of bearing for automotive turbochargers. The automotive industry continuously investigates how to reduce the bearing friction losses and how to create silent turbochargers. Many of these studies involve creating a numerical model of the rotor-bearing [...] Read more.
Floating ring bearings are the commonly used type of bearing for automotive turbochargers. The automotive industry continuously investigates how to reduce the bearing friction losses and how to create silent turbochargers. Many of these studies involve creating a numerical model of the rotor-bearing system and performing validation on a test bench on which a turbocharger is driven by hot gases. This approach, however, involves many uncertainties which diminish the validity of the measurement results. In this study, we present a test setup in which these uncertainties are minimized. The measurement results show the behavior of the floating ring bearing as a function of oil feed pressure, oil feed temperature, rotor unbalance and bearing clearances. Next to an increased validity, the test setup provides measurement data with good repeatability and can therefore represent a case study which can be used for validation of rotor-bearing models. Full article
(This article belongs to the Special Issue Bearings in Turbomachinery)
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19 pages, 8543 KiB  
Article
The Effect of Non-Circular Bearing Shapes in Hydrodynamic Journal Bearings on the Vibration Behavior of Turbocharger Structures
by Lukas Bernhauser, Martin Heinisch, Markus Schörgenhumer and Manfred Nader
Lubricants 2017, 5(1), 6; https://doi.org/10.3390/lubricants5010006 - 3 Mar 2017
Cited by 16 | Viewed by 8104
Abstract
Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (sub)components mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic [...] Read more.
Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (sub)components mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic bearings such as floating bearing rings. Particularly, the study of self-excited non-linear vibrations of the rotor-bearing systems is crucial for the understanding, prevention or reduction of the noise and, consequently, for a sustainable engine acoustics development. This work presents an efficient modeling approach for the investigation, optimization, and design improvement of complex turbocharger rotors in hydrodynamic journal bearings, including floating bearing rings with circular and non-circular bearing geometries. The capability of tonal non-synchronous vibration prevention using non-circular bearing shapes is demonstrated with dynamic run-up simulations of the presented model. These findings and the performance of our model are compared and validated with results of a classical Laval/Jeffcott rotor-bearing model and a specific turbocharger model found in the literature. It is shown that the presented simulation method yields fast and accurate results and furthermore, that non-circular bearing shapes are an effective measure to reduce or even prevent self-excited tonal noise. Full article
(This article belongs to the Special Issue Bearings in Turbomachinery)
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18 pages, 4488 KiB  
Article
Towards Accurate Prediction of Unbalance Response, Oil Whirl and Oil Whip of Flexible Rotors Supported by Hydrodynamic Bearings
by Rob Eling, Mathys Te Wierik, Ron Van Ostayen and Daniel Rixen
Lubricants 2016, 4(3), 33; https://doi.org/10.3390/lubricants4030033 - 8 Sep 2016
Cited by 16 | Viewed by 7052
Abstract
Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the [...] Read more.
Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its comprehensiveness. In this study, we construct three bearing models of increasing modeling comprehensiveness and use these to predict the response of two different rotor-bearing systems. The main goal is to evaluate the correlation with measurement data as a function of modeling comprehensiveness: 1D versus 2D pressure prediction, distributed versus lumped thermal model, Newtonian versus non-Newtonian fluid description and non-mass-conservative versus mass-conservative cavitation description. We conclude that all three models predict the existence of critical speeds and whirl for both rotor-bearing systems. However, the two more comprehensive models in general show better correlation with measurement data in terms of frequency and amplitude. Furthermore, we conclude that a thermal network model comprising temperature predictions of the bearing surroundings is essential to obtain accurate predictions. The results of this study aid in developing accurate and computationally-efficient models of flexible rotors supported by plain journal bearings. Full article
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