Influence Of Rotational Speed Research Articles

Numerical investigation and optimization of the melting performance of latent heat thermal energy storage unit strengthened by graded metal foam and mechanical rotation

In this paper, a combined passive graded metal foam and active mechanical rotation strategy is proposed to simultaneously solve the problem of slow melting rate and non-uniform phase change problem of the latent heat thermal energy storage (LHTES) technology. The enthalpy-porosity method and fixed grid structure are employed to numerically investigate the effects of porosity range, the number of graded layers, and the rotational angular velocity. Moreover, the response surface method (RSM) is further selected to optimize the structural parameters and obtain the function of melting performance and various factors. The result shows that there is an optimal porosity range and the total melting time decreases first and then increases with the increase of porosity range. When the porosity range is 12 % and the graded layer is three, it can shorten the melting time by 35.54 % and increase the thermal energy storage rate (TESR) by 51.57 %. In addition, the melting performance is gradually improved as the number of graded layers increases. The strengthening effect of graded metal foam with just four layers is close to that of the maximum layers considered in this paper. The trend of the influence of rotation speed on the melting performance of the LHTES unit is consistent with the porosity range, indicating the existence of the optimal rotational speed. The RSM optimization structure, with a 14.969 % porosity range, 5-layer graded number, and 2.267 rpm rotational speed, shortens the melting time by 42.42 % and increases the TESR by 62.75 % compared with the stationary case with uniform metal foam. This work verifies the effectiveness of active rotation coupling with passive graded porous structures, which could provide a new strengthening approach to enhance LHTES.

DEM analysis of flow dynamics of cohesive particles in a rotating drum

Cohesive particles, prevalent in chemical and metallurgical industries, necessitate a comprehensive investigation of their behavior. This study employs the discrete element method to predict the motion of two distinct types of cohesive particles within a three-dimensional rotating drum, with the evaluation of the influence of rotational speed on particle-level parameters, encompassing velocities, angular velocities, dispersion coefficients, and contact forces. The findings reveal that wet particles treated with a honey-additive exhibit heightened inter-particle bonding, resulting in flatter surfaces on inclined planes. Cohesive particles within the active region attain greater translational velocities than their counterparts within the passive region. The x-direction dispersion intensity of water-additive particles in both the active and passive regions increases from 2.41 × 10−4 m2/s and 9.99 × 10−5 m2/s to 5.75 × 10−4 m2/s and 3.34 × 10−4 m2/s, respectively, with the increase in rotational speed from 5.6 RPM to 11.6 RPM. Particles with a honey-additive demonstrate larger dispersion coefficients along the x- and y-axes, as well as higher velocities and contact forces, albeit lower angular velocities in contrast to particles treated with a water-additive. Furthermore, an escalation in rotational speed amplifies the dispersion coefficients and contact forces of the cohesive particles. The rotating kinetic energy of the particles with water-additive and honey-additive increases from 0.005 J and 0.01 J to 0.01 J and 0.045 J, respectively.

Speed-based analysis and prediction of fatigue life for the crankshaft via genetic algorithm

To improve the accuracy of crankshaft fatigue life prediction, a new method for predicting the fatigue life of crankshafts was proposed, considering the influence of rotational speed on fatigue life. This study investigates the relationship between engine speed and crankshaft fatigue life, and the engine speed will obviously affect the fatigue life of the crankshaft. Considering the influence of different engine speeds, a crankshaft fatigue life prediction model considering the engine speed is proposed. The method first obtains the crankshaft force time domain data under different loads through multi-body dynamics simulation, and analyzes the relationship between different engine speeds and crankpins force. The crankshaft fatigue life under different loads of the engine is calculated based on fatigue damage accumulation theory. Genetic algorithm is used to find the optimization of the relevant parameters of the crankshaft fatigue life prediction model considering the engine speed and determine the values of the parameters. The fatigue life and remaining fatigue life of the crankshaft is calculated using the proposed crankshaft fatigue life prediction model according to the engine speed signal. The proposed model in this study demonstrates a higher level of accuracy, as evidenced by the result showing a prediction error of 3.45%.

Three-Dimensional Characterization of Dry Particle Coating Structures Originating from the Mechano-fusion Process.

Dry particle coating processes are of key importance for creating functionalized materials. By a change in surface structure, initiated during coating, a surface property change and thus functionalization can be achieved. This study introduces an innovative approach employing 3D X-ray micro-computed tomography (micro-CT) to characterize coated particles, consisting of spherical alumina particles (d50 = 45.64 μm), called hosts, surrounded by spherical polystyrene particles (d50 = 3.5 μm), called guests. The formed structures, hetero-aggregates, are generated by dry particle coating using mechano-fusion (MF). A deeper understanding of the influence of MF process parameters on the coating structures is a crucial step toward tailoring of coating structure, resulting surface property and functionalization. Therefore, the influence of rotational speed, process time, and total mechanical energy input during MF is explored. Leveraging micro-CT data, acquired of coated particles, enables non-stereologically biased and quantitative coating structure analysis. The guest's coating thickness is analyzed using the maximum inscribed sphere and ray method, two different local thickness measurement approaches. Particle-discrete information of the coating structure are available after a proper image processing workflow is implemented. Coating efficiency and guest's neighboring relations (nearest neighbor distance and number of neighbors inside search radius) are evaluated.

Thermo-Mechanical Characterization of Metal-Polymer Friction Stir Composite Joints-A Full Factorial Design of Experiments.

With the increasing demand for lighter, more environmentally friendly, and affordable solutions in the mobility sector, designers and engineers are actively promoting the use of innovative integral dissimilar structures. In this field, friction stir-based technologies offer unique advantages compared with conventional joining technologies, such as mechanical fastening and adhesive bonding, which recently demonstrated promising results. In this study, an aluminum alloy and a glass fiber-reinforced polymer were friction stir joined in an overlap configuration. To assess the main effects, interactions, and influence of processing parameters on the mechanical strength and processing temperature of the fabricated joints, a full factorial design study with three factors and two levels was carried out. The design of experiments resulted in statistical models with excellent fit to the experimental data, enabling a thorough understanding of the influence of rotational speed, travel speed, and tool tilt angle on dissimilar metal-to-polymer friction stir composite joints. The mechanical strength of the composite joints ranged from 1708.1 ± 45.5 N to 3414.2 ± 317.1, while the processing temperature was between 203.6 ± 10.7 °C and 251.5 ± 9.7.

Experimental and simulation investigation of the impact of rotational speed on the performance of radial-flow gas wave ejector

The gas wave ejector (GWE) is a device that enables energy transfer between gases at different pressures through pressure waves. We conduct an experimental and simulation study on a novel radial-flow GWE, named DUT-R1, designed to harness centrifugal force to enhance mass and energy transfer efficiencies. Considering the significant influence of rotational speed (n) on the pressure waves and flow losses, we examine the relationship between the n of the DUT-R1 and both its ejection rate (ξ) and total efficiency (ηT).Experimental data demonstrate that the GWE can attain the highest ξ and ηT at an optimal designed rotational velocity (nd) when the pressure ports remain fixed. Simulations suggest that the primary cause can be attributed to the disruption of the ideal wave system. And when the equipment is equipped with ports matched to the nd, a consistent increase ξ is observed as the nd increases from 2000 r/min to 4000 r/min, resulting in a maximum improvement of 13.25 %. The simulation results demonstrate that increasing n enhances the suction capacity of the equipment through the inputting of shaft power (P). However, ηT initially increases and then decreases as the nd increases, with a maximum improvement of 11.86 %. The simulation provides an explanation for the observed variations in ηT during the experimental investigation by illustrating that flow losses initially decrease and then subsequently increase with an increasing value of n.

Behavior of an aerodynamic sliding bearing with textured surface under turbulent conditions

Abstract Recent advancements in turbomachinery development aim to reduce components while improving performance and minimizing environmental impact. Aerodynamic bearings, supporting high-speed rotors by dissipating significant energies, are key elements requiring thorough understanding. In order to better predict the behavior of aerodynamic bearings operating under severe conditions, numerical models using computational fluid dynamics have been employed to study the thermal effect on the tribological behavior of these air-lubricated bearings. An analysis of surface texturing of the bearings has also been conducted to evaluate its influence on operational performance compared to non-textured surfaces, considering the influence of rotation speed, radial load, and textures on the tribological performance of plain bearings. The main results observed are as follows. First, there is a noticeable change in geometric characteristics, such as the application of micro-textures, lubrication and friction, compared with conventional plain bearings. This textured surface appears to have a significant influence on the pressure and velocity distribution of the lubricating fluid, leading to significant changes in the bearing's tribological and operational performance. In addition, numerical analysis also reveals significant variations in shear stresses in the vicinity of the bearing walls. These variations can potentially affect the strength and durability of the bearing under severe operating conditions. Additionally, the results show a downward trend in system temperature, suggesting improved thermal management thanks to the textured surface. Another essential aspect revealed by this analysis is the decrease in the coefficient of friction with increasing shaft speed. This observation underlines the importance of operating speed and applied radial load in the bearing's tribological behavior and suggests further optimization possibilities for reducing energy losses and extending the life of the aerodynamic sliding bearing.

Optimization of mechanical and surface properties of friction stir welded dissimilar joint of 2507 SDSS and 317L ASS by controlling process parameters

Stainless steel welding has been widely used in industrial manufacturing, and friction stir welding has been recognized to reduce production costs significantly. To fully utilize the different properties of 2507 super duplex stainless steel (SDSS) and 317L austenitic stainless steel (ASS), the mechanical and surface properties of 2507 SDSS and 317L ASS dissimilar stainless steel joints were improved using the friction stir welding (FSW) method. The influence of rotation speed on the microstructural characteristics, mechanical properties, and corrosion behavior of the weld joints was investigated by welding at a constant speed of 20 mm/min within the range of 300–600 rpm. Specifically, at 400 rpm, a welded joint with optimal performance was obtained. When the rotation speed is 400 rpm, the yield strength (YS) and ultimate tensile strength (UTS) of the welding joint are 493 and 692 MPa, respectively, and the elongation (EL) is 32 %. The tensile strength is higher than 317L ASS but lower than 2507 SDSS, the EL is lower than those of 317L ASS and 2507 SDSS, and the friction coefficient of the welded joint is 0.93, which is between 317L ASS and 2507 SDSS. Notably, the refinement of grains in the stirred zone significantly improved the corrosion resistance of the welded joint, considerably exceeding that of the 317L ASS but still lower than the 2507 SDSS. This work can provide a process reference for studying the mechanical and corrosion properties of dissimilar stainless steel FSW.

Research on the influence of rotational speed on the performance of high-speed permanent-magnet generator

Research on the influence of rotational speed on the performance of high-speed permanent-magnet generator

Based on Fluent, the numerical simulation of the flow field on the filter disk surface of the rotary filter device

The rotary screen filter is the most typical basic structural element in rotating mechanical devices. It is being widely applied in various fields of industrial production. Using a spinning disc as the research subject, this study utilizes Computational Fluid Dynamics (CFD) techniques to establish a physical model of the filter disc. Various parameters and their corresponding boundary conditions are set, followed by a comprehensive and detailed three-dimensional numerical simulation of the high-speed rotating disc using the Fluent software platform. The objective is to investigate the effects of disc rotation speed and liquid inlet velocity on the surface flow field, as well as the influence of rotational speed on the attachment of particle impurities to the surface. Finally, the computational results will be visualized and thoroughly analyzed.

RFIS-HI: a new health indicator for quantitative condition monitoring of the bearing under variable speed conditions

The health indicator (HI) plays a crucial role in the condition monitoring of the rolling bearing. However, most existing HIs exhibit significant fluctuations when the speed changes. To address the issue, this paper proposes a new HI namely reweighted fault impact strength (RFIS)-HI. First, sub-signals are obtained through a frequency division strategy, and corresponding resampled signals are derived using order tracking. Second, the average impact peak in the time domain is acquired to measure the impact of the signal. According to fault characteristic order (FCO), the ratio of FCOs summation to noise amplitude in the frequency domain is obtained to measure periodicity. Then, the FISgram is constructed for selecting the optimal frequency band. To better quantify the degradation degree of the bearing, different weights are assigned and optimized for constructing RFIS. Finally, the influence of rotational speed on RFIS is eliminated by utilizing prior knowledge. Taking the first 10% of the dataset as baseline data, RFIS-HI is constructed through relative similarity. In this paper, a bearing dataset under time-varying speed conditions and an XJTU-SY dataset are used for verification. Results show that the proposed HI can achieve better trendability, scale similarity, and stability.

Research on Rotor Loss and Rotor Structure Optimization of Rare Earth Permanent Magnet Synchronous Motors in the Weak Field Area

The rotor loss of rare earth permanent magnet synchronous motor (PMSM) affects the efficiency and reliability of the motor and is an important research direction of rare earth permanent magnet synchronous motors. In this paper, the influence of rotational speed on the loss of the rotor core and the permanent magnet is analyzed through the analysis of the motor magnetic field and rotor loss calculation. Specifically, with the increase in rotational speed, the weak magnetic current increases, the amplitude of flux density change in the rotor core decreases, and the loss of the rotor core also decreases. The greater the influence of the harmonic current magnetic field on the outside of the rotor, the greater the loss. The core loss on the rotor is mainly distributed on the outside of the rotor. For further engineering applications, this paper analyzes the loss composition of three kinds of motors with different rotor structures and judges the optimal scheme based on the minimum loss. Finally, the correctness of this research is verified by comparing the experimental and simulation results of two kinds of motors with different rotor structures. The research content of this paper can provide a reference for the loss analysis and optimization and rotor structure selection of rare earth permanent magnet synchronous motor rotor design.

Influence of Rotation Speed and Gas Content on the Transient Gas–Liquid Two-Phase Flow of an Electric Submersible Pump

In order to study the internal flow characteristics of the electric submersible pump (ESP) when the gas–liquid two-phase flow is conveyed by the variable frequency variable speed operation and the change of the imported gas content, the impeller of the Q10# ESP is taken as the research object, based on the Eulerian-Eulerian non-homogeneous phase. The flow model, the unsteady Reynolds time-averaged N-S equation, and the standard k-ε turbulence model are used for transient simulation calculations of the gas–liquid two-phase flow in the impeller of the ESP. Calculations show that with the rotation of the impeller, the gas phase is unevenly distributed in the flow channel. The gas phase is mainly concentrated on the inlet side of the flow channel near the front cover, and the gas phase exhibits periodic aggregation and diffusion in the flow channel. When the impeller speed increases, the period of periodic accumulation and diffusion of gas in the flow channel is shortened and the gas concentration in the impeller decreases, the overall flow velocity in the flow channel increases, and the pressure difference between the inlet and outlet increases. The pressure difference between the two sides of the blade is proportional to the speed of the impeller, and the fluctuation frequency of the blade surface also increases. As the gas content increases, the maximum concentration of gas phase in the flow channel increases. The area occupied by the high concentration of gas phase in the flow channel expands toward the blade’s working surface, and periodically accumulates, diffuses, and grows. The gas-liquid splitting area shrinks toward the front cover side and the pump. The internal pressure increases slightly, the main flow velocity increases, and the vortex action range increases.

Investigation on the microstructure and mechanical property of friction stir lap welded acrylonitrile butadiene styrene/polycarbonate produced by double-pin tool

Friction stir lap welding (FSLW) of dissimilar acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) was conducted using a double-pin tool. The formation process of the weld and the influences of rotational speed on the microstructure and mechanical property were investigated. It was found that the weld was generated accompanying with the closure of old cavities in the front of the pins and the simultaneous regeneration of new cavities in the rear of the pins. Annular material flow on the vertical and horizontal directions occurred during FSLW. With the increase of the rotational speed, the PC anchors resulted from the upflow of plasticized PC layer and the shoulder affected zone both enlarged. Microstructure analysis of the weld nugget showed that PC was fragmented into lamellar, columnar, and spherical particles and their dimensions decreased when rotational speed increased. Lap-shear tensile tests showed that the weld strength increased with higher rotational speed and the maximum strength of the weld produced under 800 r/min reached 19.38 MPa, which was comparable to the ABS/PC welds produced by a tapered pin under the optimal parameters. Through the further optimization of such FSLW process, it was potential to join dissimilar polymeric components in future industrial manufacturing field.

Influences of Rotational Speed on Friction Stir Welding Quality, Mechanical and Fatigue Behaviour of AA6061/SiC Composite

Influences of Rotational Speed on Friction Stir Welding Quality, Mechanical and Fatigue Behaviour of AA6061/SiC Composite

Cross influence of rotational speed and flow rate on pressure pulsation and hydraulic noise of an axial-flow pump

Axial-flow pumps may experience significant pressure pulsation and high hydraulic noise when deviating from design conditions, and this article investigates the cross influence of rotational speed and flow rate on inlet pressure pulsation and hydraulic noise of an axial-flow pump based on coherence theory through physical model experiments. The energy amplitude of pressure pulsation is directly proportional to rotational speed and inversely proportional to flow rate, as rotational speed increases, the energy distribution of the blade passage frequency (fBPF) within different frequency bands of pressure pulsation improves. Pressure pulsation and the overall natural frequency of the pump device work together to define the primary and secondary frequencies of the sound pressure level, as rotational speed increases, these frequencies eventually move toward 2fBPF, and the coherence coefficient at frequencies of fBPF and 2fBPF is above 0.9. To reduce hydraulic noise, both pressure pulsation and natural frequency should be given sufficient attention.

Vibration characteristics analysis of flexible helical gear system with multi-tooth spalling fault: Simulation and experimental study

Gear systems operating at high speeds and under heavy loads are susceptible to continuous multiple tooth surface spalling. The time-varying meshing stiffness (TVMS) model of helical gear pair with multi-tooth spalling fault is established by combining image recognition method and loaded tooth contact analysis (LTCA) method to target the actual form of the spalling fault, and its effectiveness was verified through finite element method (FEM). The flexible helical gear dynamic model is established by utilizing 8-node shell model and Timoshenko beam model to simulate the gear foundations and shafts, the TVMS in multi-tooth spalling fault condition is introduced as the excitation. The mapping relationship between the meshing process, TVMS and vibration response under the influence of rotational speed, spalling surface morphology scale, spalling depth and location of spalling occurrence is analyzed by combining simulation and experimental results. As the rotational speed increases, the specific meshing frequency coincides with the natural frequency of the gear system, leading to the phenomenon of superharmonic resonance. Continuous multi-tooth spalling fault results in continuous time-domain shocks and the meshing frequency modulation of the rotational frequency of the gear with spalling fault. In the absence of bottoming out, the increase in spalling surface morphology scale exerts a more pronounced influence on the vibration characteristics of the helical gear system compared to the increase in spalling depth. The research results can provide theoretical basis for gear system fault diagnosis.

Effects of High Rotational Speed on Leakage and Windage Heating of Staggered Labyrinth Seals With Smooth and Honeycomb Lands

Abstract Being an important component of aero-engines, the labyrinth seal has always been the focus of research for leakage characteristics. Rotation is usually neglected or taken for minimal effect on seal leakage in previous studies. However, the effect of high rotational speed is inevitable to understand the leakage characteristics of labyrinth seal accurately. Meanwhile, due to high rotational speed, viscous heat is generated massively to result in the rapid temperature rise of leakage flow. Also, the influence of rotational speed on windage heating inside the seal clearance has not been indicated completely. Therefore, the leakage and windage heating of staggered labyrinth seals with smooth and honeycomb lands were experimentally and numerically studied. The large-scale and multifunctional sealing test rig were employed to carry out the experiments with rotational speed 12,000 rpm and pressure ratio range 1.1–2.2. The simulation data obtained by three-dimensional computational fluid dynamics methodology show great agreement with experimental results. Notably, the leakage coefficient is not monotonically decreasing with increased rotational speed, but exists a maximum peak at RPM = 8000. The variation of axial kinetic energy in seal clearance entrances provides a clear explanation of the phenomenon. Rotational speed plays an important role in windage heating, and honeycomb cell size is of secondary importance. Based on simulation data, the calculating formula of windage heating is fitted and shows great performance. This study can provide theory and data support for the follow-up structural optimum design of the labyrinth seal.

Research on the Effect of Load and Rotation Speed on Resistance to Combined Wear of Stainless Steels Using ANOVA Analysis.

This research was carried out with the aim of obtaining appropriate principles for describing the influence of working parameters and the aggressive action of an acidic medium on the wear and corrosion resistance of martensitic stainless steels. Tribological tests were performed on induction-hardened surfaces of stainless steels X20Cr13 and X17CrNi16-2 under combined wear conditions at a load of 100 to 300 N and a rotation speed of 382 to 754 min-1. The wear test was carried out on a tribometer with the use of an aggressive medium in the chamber. After each wear cycle on the tribometer, the samples were exposed to corrosion action in a corrosion test bath. Analysis of variance revealed a significant influence of rotation speed and load due to wear on the tribometer. Testing the difference in the mass loss values of the samples due to corrosion using the Mann-Whitney U test did not show a significant effect of corrosion. Steel X20Cr13 showed greater resistance to combined wear, which had a 27% lower wear intensity compared to steel X17CrNi16-2. The increase in wear resistance of X20Cr13 steel can be attributed to the higher surface hardness achieved and the effective depth of hardening. The mentioned resistance is the result of the creation of a martensitic surface layer with dispersed carbides, which increases the resistance to abrasion, dynamic durability, and fatigue of the surface of the protective layer.

A study on the influences of journal axial vibration on ship shaft stern bearing dynamic characteristics

PurposeThis paper aim to take the ship shaft stern bearing as the research object, and studies the influence of journal axial vibration on bearing dynamic characteristics under different misaligned angles and rotation speeds.Design/methodology/approachComputational fluid dynamics (CFD) and harmonic excitation method were used to build bearing unstable lubrication model, and the dynamic mesh technology was used in calculation.FindingsThe results indicate that journal axial vibration has a significant effect on bearing dynamic characteristics, like maximum oil film pressure, bearing stiffness and damping coefficients, and the effect is positively correlated with journal misaligned angle. The effect of shaft rotation speed and journal axial vibration on bearing dynamics characteristics are independent; they have no coupling. Bearing axial stiffness is mainly affected by the journal axial displacement, bearing axial damping is mainly affected by journal axial velocity and they are positively correlated with the misaligned angle. The influence of rotational speed on bearing axial stiffness and axial damping is not obvious.Originality/valueThis paper establishes the bearing dynamic model by CFD and harmonic excitation method with consideration of cavitation effect and analyzing the influence of journal axial vibration on the dynamic characteristics. The results are benefit to the design of ship propulsion shaft and the selection of stern bearing. Also, they are of great significance to improve the operation stability of the shaft bearing system and the vitality of the ship.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0337/