Rotation Frequency Research Articles

Observation and characterisation of trapped electron modes in Wendelstein 7-X 21

Abstract Abstract. In the past, quasi coherent modes were reported for nearly all tokamaks.
The general definition describes modes as quasi coherent when the magnitude squared
coherence is in the range of 0.3 to 0.6. Quasi coherent modes are observed in the
plasma core as well as in the plasma edge and can have quite different physical origins.
The one in the core are observed in plasmas with low collisionality, where the electron
temperature exceeds the ion temperature in the plasma core. This is the case for
electron cyclotron heating in general. The origin of these modes are electrons trapped
within a magnetic mirror, as reported in the past from various fusion devices. The
so-called trapped-electron modes (TEMs) belong to drift wave instabilities and can be
destabilized by electron-temperature gradients in the plasma core. From the diagnostic
point of view, quasi coherent modes appear as fluctuations in electron density and
temperature. Therefore, the microwave reflectometer is very well suited to monitor
these modes.
This paper describes experiments, conducted at the Wendelstein 7-X stellarator (W7-
X), which aim at detecting quasi coherent modes at low wave numbers. A Poloidal
Correlation Reflectometer (PCR) installed at W7-X, is able to
R measure low wave
numbers (k⊥ ≤ 3.5 cm−1 ). For medium line-averaged densities ( ne ≤ 6 × 1019 m−2 )
the plasma core is accessible for this diagnostic. For different magnetic configurations
and plasma parameters, broad quasi-coherent structures are observed in the coherence
spectra. From the analysis of the rotation and the poloidal structure, these quasi
coherent (QC) modes show the properties of electron-temperature-gradient driven
TEMs. A linear relation between the mode velocity and the rotation frequency is
found. The relation is uniform and confirms the nature of QC-mode observation as
TEM in tokamaks, too.

Study on the one-year accuracy of pulsar time-scale

Abstract Determining accurate pulsar timing model parameters is essential for establishing TT(PT), a realization of Terrestrial Time(TT) based on a pulsar time-scale(PT). This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters. Using observations of PSR J0437-4715, J1909-3744, J1713+0747, and J1744-1134 from the second data release of the International Pulsar Timing Array (IPTA II, Version A), we compare the accuracy of the timing model parameters determined by these observations with different data spans. The results show for PSR J0437-4715, J1713+0747, and J1909-3744, the amplitude fluctuations of rotational frequency remain within $10^{-15}$, $10^{-14}$, and $10^{-14}$ Hz, respectively, when the data spans for determining pulsar timing model parameters exceed 13, 14, and 6 years. Additionally, the one-year accuracy of TT(PT) is crucial for its application in timekeeping. By comparing the frequency deviations of TT(PT) relative to TT(BIPM) under both ideal ($k_{r}$) and actual ($k_{p}$) conditions across different data spans, we find that when the data span reaches the duration above, the accuracy of TT(PT) surpasses that of TT(TAI) under ideal conditions, slightly inferior under actual conditions. This suggests with improved observational technologies, the accuracy of TT(PT) can be further enhanced.

Bearing faults diagnostic in permanent magnets synchronous motor

With the widespread use of MSAPs in fields such as robotics, automotive, aerospace, medical equipment, renewable energy, etc., the preventive diagnosis of faults affecting these types of motors has become essential to avoid unplanned shutdowns that could lead to considerable financial losses. Even though the permanent magnet synchronous motor is well known for its robustness and efficiency, however it suffers from electrical or mechanical faults. Spectral analysis has become a very important tool for the detection of these faults and we will use this method to determine the frequencies characterizing the fault in MSAPs. It is important to note that the exact distribution of failures can vary depending on the specific motor and its operating conditions. The characteristic frequencies of the bearing failure are a function of the geometric parameters of the bearing and the motor rotation frequency. Unlike the induction motor, the rotation frequency of the PMSM is fixe, which makes it easier to locate the characteristic frequencies of the bearing fault. This work presents the application of spectral analysis for the diagnosis of the bearing defect and more specifically, that of the outer ring. The experimental results obtained show the interest and effectiveness of spectral analysis for the detection of bearing defects.

Is it Possible to Detect a Rotating Spherical Colloidal Particle?

A single micrometer‐size spherical colloid has been set in rotation by transfer of light orbital angular momentum. This particle is floating at an air–water interface. Steady‐state rotational frequencies of the order of one hertz have been observed, depending on the topological charge of the beam and on its power, in agreement with expected values. The detection is performed using the rotational Doppler shift of the diffused light. Two time constants have been evidenced in the rotational velocity dynamics. The first one is related to the friction of the colloid with the fluid (air and water), whereas the other one is principally associated with the wall friction of the air–liquid interface with the container. This measurement technique makes it possible to identify dynamic parameters of the rotational movement of any spherical object, which is usually impossible to detect.

Experimental investigation on gas-liquid two-phase flow patterns and vibration characteristics of an inducer pump

Inducers typically enhance centrifugal pump performance in two-phase flow regimes by producing more uniform mixtures and increasing pressure before the impeller. Their impact is most pronounced under part-load conditions compared to overload situations. This study experimentally investigates air-water two-phase flow behavior within a pump inducer. Using high-speed photography and grayscale image processing, five distinct gas-liquid flow patterns were identified: bubble flow, strip bubble flow, agglomerated bubble flow, gas pocket flow, and segregated flow. The inducer's head and vibration characteristics were also measured. Results show that flow pattern transitions significantly affect performance degradation and vibration. Specifically, the head decreases as the liquid flow rate increases at a constant gas volume fraction (λ) and generally follows a downward trend as λ increases at a constant liquid flow rate. Bubble flow, representing minimal λ, has a negligible effect on performance. However, with higher λ, a sharp decline in head occurs within the agglomerated bubble flow range, followed by a gradual decrease during gas pocket flow under both optimal and overload conditions. In part-load conditions, the head decreases sharply during strip bubble and segregated flow. While bubble flow mitigates vibration fluctuations, increasing GVF leads to higher vibration amplitude, particularly in the range of 2–8 times the inducer's rotational frequency, due to flow pattern instability.

МОДЕЛЬНЫЙ РЯД УНИФИЦИРОВАННЫХ СИЛОВЫХ ЭЛЕКТРОПРИВОДОВ ДЛЯ КОММЕРЧЕСКОГО ЭЛЕКТРОТРАНСПОРТА

The article considers the creation of a model range of unified electric power drives for commercial electric vehicles. The peculiarity of the work is the realization of the concept of reducing the cost of production of electromechanical power units (EMPU) of electric vehicles by unification of units and components included in its composition. When forming a number of unified electric power drives, the components were subjected to a set of design, layout, technological and economic requirements ensuring the production on their basis of cargo or passenger electric vehicles with gross weight from 3.5 to 12 t, which corresponds to vehicle categories N1, N2, M2, M3. The developed main components of the unified EMPU include: asynchronous three-phase traction electric motors with power range from 80 to 300 kW, torque range from 250 to 1,000 N·m respectively, output shaft rotation frequency of 9,000 rpm and liquid cooling of stator and rotor; inverters designed to control traction motors with input voltage range from 300 to 900 V, output phase current range from 200 to 600 A and liquid-cooled power keys; reduction gearboxes with gear ratio from 3 to 4.5 and step gearboxes with the number of gears from 2 to 4. The result of works on unification of electric power drives for commercial transport also is a number of standard designs of parts and units and assembly units; normative and technical support of control (tests, analysis, measurements) of certification and quality assessment of products; establishment of requirements for technological processes, including for reduction of material, energy and labor intensity to ensure the use of low-waste technologies. When creating the electric truck MAZ-4381EE, corresponding to the vehicle category N2, the EMPU was used as a part of electric motor TAEM 130 with capacity of 130 kW and two-stage shaft gearbox. The created prototype of electric truck is characterized by almost complete localization, providing import independence of most components and intellectual component of the car.

Zonal flow instability induced by nonlinear inertial waves in a librating cylinder with sloping ends

This paper compares the nonlinear dynamics of two key types of motion observed in a rotating liquid-filled cavity subject to external forcing: an inertial wave attractor and resonant inertial oscillations (inertial modes). Experiments are performed with a cavity having a specific shape of a truncated circular cylinder delimited by plane-parallel end walls inclined with respect to the cylinder base. The cavity rotation axis coincides with the axis of the cylindrical surface. Libration-type forcing is introduced by harmonic modulation of the background rotation frequency. The sloping end walls break the axial symmetry of the liquid domain: the shape of the axial-radial cross sections varies from parallelogram to rectangle depending on the azimuthal angle. It is found that, regardless of the liquid response type (wave attractor or inertial modes), the transition from linear to nonlinear dynamics follows the scenario of triadic resonance instability. However, the time-averaged zonal flow responds differently to the primary wave instability. Inertial-mode instability generates a system of azimuthally periodic averaged vortices, whose frequency coincides with the subharmonic frequency of the triadic resonance. At high libration amplitudes, a low-frequency component appears in the azimuthal velocity spectrum, being associated with excitation of the retrograde system of vortices. The development of the weakly nonlinear regime of the wave attractor is accompanied by the instability of the viscous boundary layers—fine-scale pattern formation occurs close to the reflection zones of the attractor branches at the cylindrical sidewall. In the strongly nonlinear wave regime, coherent vortex structures are excited, performing azimuthal and radial drifts.

A Novel Detection Scheme for Motor Bearing Structure Defects in a High-Speed Train Using Stator Current.

Railway traction motor bearings (RTMB) are critical components in high-speed trains (HST) that are particularly susceptible to failure due to the high stress and rotational frequency they experience. To address the challenge of high false-positive rates in existing monitoring systems, this paper introduces a novel sensorless monitoring scheme that leverages stator current to detect fault-related characteristics, eliminating the need for additional sensors. This approach employs a hybrid signal preprocessing algorithm that integrates adaptive notch filtering (ANF) with envelope spectrum analysis (ESA) to effectively sparse the stator current and extract relevant fault features. A deep belief network (DBN) is utilized for the classification of the health status of the RTMB. To validate the scheme's feasibility and effectiveness, we conducted experiments on a 1:1 scale high-speed railway traction motor, demonstrating that mechanical defects in RTMB can be reliably indicated by changes in stator current. Based on the analysis of experimental results, it was concluded that the fault detection accuracy of RTMB based on stator current is at least 17.3% higher than that of the fault diagnosis methods based on vibration in diagnosing whether the system has a fault. Among them, the method proposed in this paper is the best in diagnosing the presence and type of faults, with an accuracy that is at least 8.9% higher than other methods. This study not only presents a new method for RTMB monitoring but also contributes to the field by offering a more accurate and efficient alternative to current practices.

STUDY OF LOADER TRANSMISSION DYNAMICS WITH HIGH TORQUE STEP-ADJUSTABLE HYDROMOTOR-WHEELS

Goal. The purpose of the article is to analyze the dynamics of the hydraulic fluid power of the forklift transmission equipped with radial-piston high- torque multi-cycle hydraulic motors with a step change in working volume. Such a transmission is offered as a gearless one compared to the use of traditional transmissions with axial-piston hydraulic motors and gearboxes in front of the drive wheel hub. Research methodology. The traction-speed characteristic of a serial wheel loader is built taking into account the constant power of the drive internal combustion engine for rotation of the axial- piston reversible adjustable transmission pump. The dependence of the torque on the wheel hub of the loader depending on its speed was analyzed. The selection of a high-torque radial-piston hydraulic motor of multi-cycle action, which satisfies the parameters of the transmission in terms of torque and maximum rotation frequency and does not have an intermediate gearbox on the hub, has been made. To reduce the set power of the drive motor of the loader pump and fuel consumption, the hydraulic motors of the transmission are also equipped with a two-stage regulator for changing the working volume. Constructed block diagrams in the VisSim application program package for the solution of nonlinear differential equations for determining the speed of the loader, the pressure in the hydraulic drive and its useful power. The results. The analysis of oscillograms of dynamic processes in the hydraulic drive of the loader showed that by means of modeling the pump supply modes and step change of the working volume of the multi-cycle radial piston hydraulic motor, it is possible to detect extreme modes that lead to fluctuations in the speed and power of the loader, as well as pressure in the hydraulic drive.

ЕЛЕКТРОМЕХАНІЧНІ ХАРАКТЕРИСТИКИ БЕЗКОНТАКТНОГО ДВИГУНА З ПОСТІЙНИМИ МАГНІТАМИ ПРИ ШИРОТНО-ІМПУЛЬСНОМУ ЖИВЛЕННІ

The paper is devoted to the study of the characteristics and operating modes of a brushless permanent magnet motor in the structure of an electric drive with a two-wire external power supply from a voltage source with pulse-width regulation. The dependences of the motor rotation frequency, the stator current effective value and the average value of the current in the DC link of the voltage inverter, as well as the dependences of the torque coefficient on the average value of the motor torque are given. The influence of the frequency of the pulse supply voltage on the operating modes of the motor is studied. The current and torque limitation modes of the motor in a system with a single-position relay controller and a fixed transistor shutdown interval former are studied. Ref. 12, fig. 16.

GDTE-based crack diagnosis for planetary gear: Mechanism, validation, and advantages compared to vibration-based technology

Effective health monitoring and fault diagnosis technologies are crucial to timely grasping the operation status of the planetary gear train (PGT). In this study, the mechanism for global dynamic transmission error (GDTE)-based crack diagnosis of PGT is revealed from dynamic responses and validated through experiments, and the advantages of this new technique are compared with the commonly used vibration-based technology. Initially, a dynamic model of the PGT considering various crack degrees and transfer path effects is established, and the effectiveness of the model response is verified through experiment. Subsequently, GDTE and vibration signals under different crack conditions are statistically analyzed in time domain and frequency domain to evaluate the differences in the ability to reveal gear failure information. Ultimately, the reasons for the different distribution of fault characterization information in the two signals are explained from a dynamic perspective. The results show that GDTE-based fault diagnosis exhibits greater sensitivity to gear crack degree compared to vibration-based monitoring technology, with both time and frequency domain responses containing richer fault characteristic information, particularly in low-frequency regions. The fault characteristics concentrated in higher-frequency regions in the vibration signal are mainly caused by the modulation between gear crack shock and the gear single and double tooth alternating meshing shock. Conversely, fault frequencies in GDTE signals are mainly found in low-frequency regions, as fault shocks in GDTE signals directly correlate with the rotational frequency of the cracked gear. Modulation effects and attenuation on the transfer path are identified as the main reasons for the weaker representation of gear fault information in vibration signals compared to GDTE signals.

Examining the Rotation of the Planet-hosting M Dwarf GJ 3942

Abstract Based on radial velocities, EXORAP photometry, and activity indicators, the HArps-n red Dwarf Exoplanet Survey (HADES) team reported a 16.3 days rotation period for the M dwarf GJ 3942. However, an estimate of the magnitude-squared coherence between the HADES RV and Hα time series has significant peaks at frequencies 1/16 day−1 and 1/32 day−1. We turn to TESS photometry to test the hypothesis that the true rotation period is 32 days with 16 days harmonic. Although the average TESS periodogram has peaks at harmonics of 1/16 day−1, the harmonic sequence is not fully resolved according to the Rayleigh criterion. The TESS observations suggest a 1/16 day−1 rotation frequency and a 1/32 day−1 subharmonic, though resolution makes the TESS rotation detection ambiguous.

Numerical investigation on rotation accumulation and natural frequency degradation for offshore wind turbine in clays

Prolonged lateral cyclic loading leads to soil stiffness degradation around offshore wind turbine (OWT) foundations, which reduces the system's natural frequency and increases the accumulation of foundation rotation angle. Proper evaluation of natural frequency and rotation angle is crucial for the design of OWT foundations. This study develops a two-stages numerical approach to calculate the fundamental frequency of OWT systems considering the foundation stiffness degradation by integrating a stiffness degradation model of soft clays with a simplified three-spring model. Subsequently, it investigates the evolution of accumulated rotation and natural frequency for three foundation types—monopile, monopod bucket, and hybrid monopile-bucket—throughout their service life. It is observed that the hybrid foundation shows the smallest rotation in the first cycle, attributable to its relatively high initial stiffness compared to the other two foundations with the same steel consumption. However, it also exhibits the highest rate of cumulative rotation growth. At the same load level, the monopod bucket foundation exhibits the largest cumulative rotation angle due to its lower bearing capacity, and the degradation of natural frequency is most pronounced for monopod bucket OWT. For all three foundation configurations, increasing either the pile diameter or the bucket diameter is the most effective approach to reduce the cumulative rotation angle and improve natural frequency degradation, while maintaining the same steel consumption. These findings should be considered in the design of OWT foundations.

ON THE MECHANISM OF ICE MELTING

Based on the theory of the Jahn-Teller effect (JTE), a model of a possible mechanism of ice melting is proposed. The increase in the heat capacity of ice near 0 ⁰C by 1.5 times, compared with the Dulong and Petit law, suggests that the initial excitation of rotational vibrational modes of water molecules occurs in it. First, the excitation of the rotational low-frequency mode occurs, then the excitation of the intermediate mode. The effect of mode coupling and instability of rotational modes of molecule vibrations at an intermediate rotational frequency is associated with the presence of a connection between all low-frequency and high-frequency rotational modes of the molecule through the Euler equations. Therefore, excitation of the intermediate frequency in ice leads to the possibility of excitation of all rotational vibrational modes, which occurs in it at a temperature of 0 ⁰C after it receives the heat of fusion. Excitation of rotational vibrational modes leads to the emergence of possibilities for the addition of vibrational modes and their synchronization. The increase in the amplitude of rotational oscillations, the convergence of the frequencies of their oscillation modes and their subsequent synchronization leads to the appearance of rotations of hydrogen atoms of a water molecule around their axes of intermolecular bonds, to a stable bending of hydrogen bonds and their subsequent weakening in water. As a result of this weakening of the bond forces, we have a decrease in the rotational frequencies of oscillations for water molecules and their local charges. As a result of this decrease in frequencies, oscillations of local charges of water molecules become less radiating and less damped. Therefore, in the liquid phase of water, these rotational oscillation modes become new undamped independent oscillation modes of its molecules. The appearance of new oscillation modes in molecules leads to a doubling of the heat capacity of water compared to ice. Excitation of all three of its rotational oscillation modes during melting of ice leads to the appearance of an anomalously large value of the heat of fusion.

IMPGREENING AND MODERNIZATION OF EQUIPMENT FOR PROCESSING CONSTRUCTION WASTE INTO SECONDARY CRUSHED STONE

The article addresses the pressing issue of processing reinforced concrete structures that have resulted from the destruction of buildings in Ukraine. Accumulating in significant volumes, reinforced concrete debris holds substantial potential for further use but requires efficient processing methods. The main focus is on the greening of equipment and modernization of jaw crushers to ensure their capability to effectively crush this type of waste, which is a critical task in the context of sustainable development and the implementation of environmentally safe technologies in the construction industry. The study analyzes existing jaw crusher designs, their technical characteristics, and possibilities for modernization. A detailed examination of crusher operation parameters, such as the angle of capture, jaw stroke, eccentric shaft rotation frequency, and the strength and rigidity of the main components, was conducted. The research findings demonstrate that optimizing the angle of capture and adjusting the rotation parameters of the eccentric shaft can significantly enhance the crusher's performance, thereby confirming the effectiveness of the proposed modifications. To achieve the set objectives, the study also focused on the wear resistance of the jaw crusher's working elements, particularly the jaws and the eccentric shaft. An analysis of the main factors affecting the wear of these elements during the crushing of reinforced concrete debris was conducted, and measures to improve their durability were proposed. Specifically, the potential use of new, more wear-resistant materials for manufacturing the jaws was explored, as well as the optimization of the crusher's thermal regime to reduce the wear of the eccentric shaft. The results of the study confirmed that the application of these approaches not only increases the crusher's efficiency but also significantly extends the service life of its working elements, which contributes to reducing operational costs and enhancing the profitability of the reinforced concrete debris processing process. The scientific novelty of this research lies in the development of optimized solutions for the greening of equipment and modernization of jaw crushers, which ensure increased efficiency in processing reinforced concrete debris of varying strengths. Particular attention was paid to the importance of properly selecting the angle of the plates and other parameters that affect equipment productivity. The implementation of the obtained results could have a significant impact on the development of construction waste processing technologies and contribute to environmental safety in Ukraine's construction industry.

Enhancing Sustainable Automated Fruit Sorting: Hyperspectral Analysis and Machine Learning Algorithms

Recognizing and classifying localized lesions on apple fruit surfaces during automated sorting is critical for improving product quality and increasing the sustainability of fruit production. This study is aimed at developing sustainable methods for fruit sorting by applying hyperspectral analysis and machine learning to improve product quality and reduce losses. The employed hyperspectral technologies and machine learning algorithms enable the rapid and accurate detection of defects on the surface of fruits, enhancing product quality and reducing the number of rejects, thereby contributing to the sustainability of agriculture. This study seeks to advance commercial fruit quality control by comparing hyperspectral image classification algorithms to detect apple lesions caused by pathogens, including sunburn, scab, and rot, on three apple varieties: Honeycrisp, Gala, and Jonagold. The lesions were confirmed independently using expert judgment, real-time PCR, and 3D fluorimetry, providing a high accuracy of ground truth data and allowing conclusions to be drawn on ways to improve the sustainability and safety of the agrocenosis in which the fruits are grown. Hyperspectral imaging combined with mathematical analysis revealed that Venturia inaequalis is the main pathogen responsible for scab, while Botrytis cinerea and Penicillium expansum are the main causes of rot. This comparative study is important because it provides a detailed analysis of the performance of both supervised and unsupervised classification methods for hyperspectral imagery, which is essential for the development of reliable automated grading systems. Support Vector Machines (SVM) proved to be the most accurate, with the highest average adjusted Rand Index (ARI) scores for sunscald (0.789), scab (0.818), and rot (0.854), making it the preferred approach for classifying apple lesions during grading. K-Means performed well for scab (0.786) and rot (0.84) classes, but showed limitations with lower metrics for other lesion types. A design and technological scheme of an optical system for identifying micro- and macro-damage to fruit tissues is proposed, and the dependence of the percentage of apple damage on the rotation frequency of the sorting line rollers is obtained. The optimal values for the rotation frequency of the rollers, at which the damage to apples is less than 5%, are up to 6 Hz. The results of this study confirm the high potential of hyperspectral data for the non-invasive recognition and classification of apple diseases in automated sorting systems with an accuracy comparable to that of human experts. These results provide valuable insights into the optimization of machine learning algorithms for agricultural applications, contributing to the development of more efficient and accurate fruit quality control systems, improved production sustainability, and the long-term storage of fruits.

Effects of Wheel Flats on Vibration and Stress Response of the Wheel-Rail System in High-Speed Trains

With the advancement of high-speed and lightweight vehicles, the occurrence of wheel tread wear, including wheel flats, has escalated. The resulting impact loads on axle-end components and the dynamic response of the axle cannot be overlooked. On-track tests were conducted on wheel flats to obtain wheel-rail forces, axle box vibration accelerations, and axle stresses during service. Time–frequency analysis was employed to uncover patterns of variation with speed. Additionally, a dynamic model of the high-speed train–track system was developed to replicate test conditions, investigating the characteristics of wheel–rail loads and structural elastic vibrations under high-frequency excitation for various flat sizes and higher operating speeds. The findings reveal that under wheel flats, the time-domain response of the wheel–rail system exhibits periodic impacts, while the frequency-domain shows high-frequency energy comprising multiple harmonics of the wheel rotation frequency. Wheel–rail forces, axle box vibration accelerations, and axle stresses exhibit inflection points with increasing speed, particularly within the 120–160 km/h range. In the high-frequency domain, axle stresses display characteristic frequencies that remain unchanged with speed, attributed to the coupled vertical bending vibration modes of the wheel–rail system. These research results offer foundational support for predicting fatigue damage to axle-end components, assessing axle stress, and establishing tolerances for tread defect limits.

Toroidal torques due to n=1 magnetic perturbations in ITER baseline scenario

Abstract Toroidal torques, generated by the resonant magnetic perturbation (RMP) and acting on the plasma column, are numerically systematically investigated for an ITER baseline scenario. The neoclassical toroidal viscosity (NTV), in particular the resonant portion, is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER. While the electromagnetic torque always opposes the plasma flow, the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction. A peculiar double-peak structure for the net NTV torque is robustly computed for ITER, as the toroidal rotation frequency is scanned near the zero value. This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral (over the particle pitch angle) in the superbanana plateau NTV regime in ITER. These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity, the plasma pedestal flow and the assumed frequency of the rotating RMP field.

Numerical model of a top-blown rotary converter preheating and charge heating with an oxy-fuel burner

Background The present work is conducted in the framework of the SisAl Pilot EU project, which aims to optimize silicon production in Europe by recycling materials and using carbon-emission-friendly technology. Silicon production experiments were conducted on laboratory and pilot scales in different types of furnaces, including top-blown rotary converters (TBRC) used as chemical reactors for molten slag-metal mixtures. In addition to experimental work, process optimization also relies on numerical modelling. Methods In this study, COMSOL Multiphysics® was used for the numerical testing of a new thermal design of TBRC by simulating its preheating and charge heating owing to an external heat source provided by an oxy-fuel burner. Results and conclusions The risk of slag solidification in TBRC during the aluminothermic reduction of silica was assessed. The model predicts that, with a useful burner power of 600 kW, the empty TBRC can be preheated to 1650°C in less than 30 min. Based on this model, the optimum burner power for maintaining the TBRC charge in a liquid state was determined. The influence of the TBRC inclination angle and its rotation frequency was studied numerically.

On the evolution of the shock waves systems created by the fan blades

Fan is one of the noise sources in a modern engine. The fan noise is especially noticeable during takeoff at high angular rotation speeds. In such operating modes, supersonic flow around the tips of the fan blades is realized, which leads to the formation of shock waves that propagate upstream until they exit of the engine channel. As a result, a specific noise is emitted into the front hemisphere, consisting of harmonics that are multiples of the fan rotation frequency. The paper analyzes the described effect based on a simple model of the propagation of a shock waves system. By using energy analysis, it is shown that the system of shock waves with equal amplitude decays faster than a system of shock waves with a spread in amplitude.