Influence Of Rotational Speed Research Articles

Influence of rotation speed and frequency on the decision of Columba livia domestica (homing pigeon) to cross the rotor-swept area of paper blades mimicking a wind turbine

Abstract To reduce bird collisions with wind turbines, automatic detection systems have been developed to slow the blades down when a bird is approaching. We experimentally tested whether blade rotational speed (i.e., number of rotations per min) and frequency (i.e., number of times a blade passes a point per min) affected the decision time (i.e., time to take-off), path choice (i.e., the position in the aviary), and decision to cross the rotor-swept area in Columba livia domestica (rock dove [domestic variety]; aka homing pigeon; hereafter, pigeon). We used a homemade device with paper blades, mimicking the movement of wind turbine blades. We adjusted the paper blade dimensions and achromatic contrast with the background to match the visual capabilities of pigeons, increasing the probability of detection. Pigeons were less likely to cross the rotor-swept area at higher speeds and frequencies, independent of their decision time. When pigeons crossed the rotor-swept area (43 out of 160 trials), 63% collided with the blades, regardless of blade speed or frequency. Pigeons chose to avoid the rotor-swept area after they had travel half the distance to the wind turbine. Pigeons were not better able to avoid the rotor-swept area when blades were rotating at low speed and/or frequency and often collided with the blades. Thus, slowing blades to a low rotational speed may not reduce collisions with some species and a complete turbine shutdown may be necessary. The feasibility and economic costs of regular complete shutdowns after the deceleration triggered by the automatic detection systems need further investigation.

Research on the Hydrodynamic Characteristics of a Rectangular Otter Board in Different Work Postures Based on a Dynamic Model

This paper investigates the hydrodynamic characteristics of a rectangular otter board in different working postures by using a dynamic model. Dynamic models are mainly based on dynamic mesh techniques. The results of the dynamic model are, compared to the model test, carried out in a flume tank. Furthermore, different rotation speeds of dynamic model were analyzed. The research results are as follows: compared to flume tank results, the maximum error of the dynamic model is 23.77%. Moreover, the influence of rotation speed on the hydrodynamic board is not obvious, and 2 deg./s was chosen as the rotation speed. When the board is tilted slightly (including four working postures), its lift-to-drag ratio first increases slightly and then gradually decreases. Compared with the other three working postures, the pressure center coefficient of the board does not change significantly when it is tilted inward. When studying different working angles (including AOA and tilt angle) of the otter board, the numerical dynamic model significantly reduces repetitive setup work, making simulations more efficient. Its ability to provide continuous curves and a large volume of results offers researchers a more detailed and comprehensive understanding of the board’s hydrodynamics. Additionally, the dynamic model supports innovative fishery equipment development by allowing more accurate and continuous numerical simulations.

Fatigue reliability analysis methodology based on fatigue life and failure mechanism for carburized gear

Gears are one of the important components in mechanical products, and their fatigue reliability determines the safety performance of mechanical products. In this paper, the fatigue characteristics of carburized gears under different torque and constant rotational speed conditions are investigated by using a gear contact fatigue testing machine, and combined with the dynamic maximum contact stress distribution on the subsurface of the meshing gears, the very-high cycle fatigue P-S-N curves of carburized gears under a stress ratio of −1 is established. Local stress concentration in the surface or subsurface of carburized gears causes grain dislocation movement under the combined influence of maximum contact and residual stresses, and then causes dislocation pileup and transcrystalline rupture after being hindered by grain boundaries, ultimately leading to pitting and fatigue failure of gears. Based on the dislocation energy method and combined with the fatigue failure mechanism of gears, a life prediction model of gears with good prediction results is established by considering the interaction of factors such as dynamic load, grain size, initial crack length, residual stress, slip band length and width. A fatigue reliability analysis method of gears is established based on the life state equation of gears considering the life prediction model. Further analyses of the influence of rotational speed, grain size, residual stress, slip band width, slip band length and initial crack size on the fatigue life reliability index of the gears resulted in the conclusion that the fatigue reliability of the gears not only decreases with the increase of the above-mentioned parameters, but also shows decreasing trend with the increase of time. This is of significance for evaluating the fatigue reliability of gears under very-high cycle fatigue conditions.

Full-size experimental investigations on planetary gear journal bearings in high-power wind turbines

Abstract To satisfy the large-scale and high-power demands of wind turbines, planetary gear journal bearings (PGJBs) have been applied in large wind turbine gearboxes (WTGs), as an alternative to traditional rolling bearings, due to their higher reliability and smaller size. To simulate the actual lubrication behaviors of PGJBs and investigate their hydrodynamic performance, a full-size test rig for PGJBs was built in this paper. A multi-parameter detection system coupled with the ultrasonic testing method was developed. Four ultrasonic piezoelectric elements, eight thermistors, two pressure transducers, and one torque sensor were used to obtain the film thickness, oil temperature, oil pressure, and friction torque data of the test PGJB. The rated condition experiment was conducted to investigate the variation of measured lubrication performance with the operating time. Three-dimensional predictions of oil film pressure, temperature, and thickness were presented to analyze the steady-state lubrication characteristic at the rated condition. Moreover, a series of steady-state experiments were also carried out to simulate the normal operations of the test PGJB at different conditions. And the measured results were verified by the numerical predictions. The influence of rotational speed, input load, oil supply temperature, and oil supply flow on the hydrodynamic performance of the test PGJB were explored.

Validation of a Methodology To Assess The Flutter Limit Cycle Oscillation Amplitude of Low-Pressure Turbine Bladed-Disks - Part II: Rotational Speed Effects

Abstract The effect of the operating conditions on the vibration amplitude trends of an isolated low-pressure turbine rotor is described. The study utilizes an analytical model correlating the aerodynamic and dry-friction work introduced in Part I of the paper. In this Part II, the analysis has been extended to incorporate the influence of rotational speed. The force distribution and the penetration length of the fir-tree contact surfaces are key parameters within the heuristic micro-slip model used to characterize the friction forces. These parameters change with rotational speed, consequently influencing the dry-friction work involved in the process. The model is closed with numerical simulations to compute the aerodynamic damping, and it is compared against experimental data gathered from the experimental campaign detailed in Part I. The results demonstrate a significant impact of the shaft speed on flutter vibration amplitude. The vibration amplitude has been observed to reach a maximum near the on-design conditions. The analytical model can correctly capture this trend indicating that the essential physics is retained in it. Nonlinear friction, mistuning and 3D unsteady aerodynamics have shown to play a predominant role to explain the change of vibration amplitude with the shaft speed.

A novel efficient calculation method for rotor aeroacoustic characteristics based on multiple aerodynamic surfaces source model

Based on the simplified acoustic source model of multiple aerodynamic surfaces, an efficient calculation method for rotor aeroacoustic characteristics has been established. Firstly, the aerodynamic characteristics database of the airfoil is obtained based on the Computational Fluid Dynamics (CFD) method. The inflow environment of each blade element is calculated using the free wake method, and the distribution of chord-wise loading is obtained by combining the established database. Subsequently, based on the F1A equation, a simplified formula for loading noise with pressure difference as a parameter is derived. The thickness noise is obtained from the blade shape and operating conditions, and the blade surface mesh is constructed by using the adaptive curvature distribution strategy of airfoil points. The validation is carried out by comparing with experimental values in the hover and forward flight states. Then, A hybrid weighted interpolation scheme is proposed based on inverse distance weighted interpolation (IDW) and bidirectional linear interpolation method, which is suitable for capturing blade/vortex interaction (BVI) noise. A set of parameters suitable for engineering applications is obtained through the parametric sensitivity analysis. The computational time and memory usage are reduced to 1/47 and 1/4 of the original amount, respectively. Finally, Using the above method, the influence of rotational speeds (ω) on rotor aeroacoustic characteristics are studied. The results show that ω and sound pressure level (SPL) are linearly related and the SPL decreases by approximately 5 dB for every 0.1 Ω decrease in ω. The rotational speed ω≈90 %Ω can effectively suppress rotor aeroacoustic levels, benefiting the stealth design of helicopters.

Influence of rotational speed on the microstructural, mechanical and wear behaviour of FSPed cast AZ91 magnesium alloy

ABSTRACT In this study, the Magnesium AZ91 alloy underwent a process known as Friction Stir Processing (FSP) at different tool rotational speeds: 1160 r.p.m., 850 r.p.m., and 580 r.p.m. subjected to a constant transverse speed/feed rate (50 mm/min). The average grain size of the FSP-processed samples fell dramatically due to dynamic recrystallisation (DRX), from 43.65 μm in the as-received Mg AZ91 to less than 4.21 μm in the alloy processed at 850 rotational speed. The UTS was enhanced from 145.49 MPa to 184.51 MPa for as-received material to alloy processed at 850 rotational speeds due to the dissolution of secondary phases and the grain refinement. Also, this increase in rotational speed resulted in an increase in total elongation (TE), which increased from 5.465% to 9.92% due to the removal of defects during the processing. The wear resistance of FSPed materials was better than that of the as-received material at all tool rotational speeds. Better wear resistance was observed in the case of samples processed at 850 r.p.m. All these alterations in properties were found due to the existence of refined grains and the removal of defects due to stirring action.

Investigation on submerged friction stir welding of AZ31B magnesium alloy under the influence of rotation speed

In this study, submerged friction stir welding (SFSW) was performed to weld 6 mm thick AZ31B Mg alloy plates, aiming to explore the impact of rotation speed on microstructure and tensile behavior. The water medium was used to submerge the samples. The SFSW was conducted at three different speeds (815, 960, and 1200 rpm), to assess the impact of rotation speed on SFSWed joint performance. As the rotation speed increased from 815 to 960 rpm, tensile strength increased plateauing over a range of the rotation speed. However, a significant drop in tensile strength occurred at 1200 rpm due to the formation of void defects. The SZ exhibits a size and width increment in the lower part with increasing rotation speed. The hardness of the stir zone (SZ) gradually rose with increasing rotation speed from 815 to 960 rpm. Fracture locations were observed in the thermal-mechanically affected zone (TMAZ) adjacent to the SZ at a rotation speed of 815 rpm, and in the heat-affected zone (HAZ) adjacent to the TMAZ at a rotation speed of 960 rpm. The joint welded at 1200 rpm fractured within the SZ. This study offers valuable insights into the welding and joining field, particularly regarding their mechanical characteristics.

Research on Temperature Rise Characteristics Prediction of Main Shaft Dual-Rotor Rolling Bearings in Aircraft Engines

Traditional aero-engine bearings rotate simultaneously with their inner and outer rings, which makes the temperature rise prediction model computationally large with low accuracy, and it cannot be accurately verified due to the means of testing. This paper presents a method for predicting the temperature rise characteristics of aero-engine bearings under composite load conditions. Firstly, the local method is used to calculate the heat generation from heat sources such as bearing spin, lubricant drag, and the differential sliding of steel ball and collar, respectively, then finite element modelling and steady-state thermal analysis are carried out for aero-engine bearings under the simultaneous action of axial and radial external loads, a double-rotor test setup is designed and the predictive model is validated, and finally, the influences of rotational speed and load on the temperature rise characteristics of the bearings are investigated. The study shows that the aero-engine bearing prediction model proposed in this paper has high accuracy; with the increase in the rotational speed of the inner ring of the bearing, the temperatures of both the inner and outer rings of the bearing increase significantly; the temperatures of the inner and outer rings of the bearing increase with the increase in the axial load, and the effect of the radial load on the temperature of the bearing is not obvious.

Investigating the influence of rotational speed in wire electric discharge machining of cylindrical workpieces: an experimental and simulation study

Investigating the influence of rotational speed in wire electric discharge machining of cylindrical workpieces: an experimental and simulation study

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

Numerical simulation and result analysis of deformation tubing of P110 steel milled by flat-bottomed shoe grinding and milling

To investigate the influence of rotational speed and drilling pressure on the milling efficiency of flat-bottomed milling shoes, a three-dimensional milling model of flat-bottomed milling shoes and deformed casing was established by using ABAQUS finite element software, and the optimal parameter combinations of milling efficiency were investigated at rotational speeds of 70~90r/min and drilling pressures of 5~25kN. The results show that: with the increase of drilling pressure and rotational speed, the mass loss of casing and the amount of footage of the grinding shoe increase, and the grinding and milling efficiency is optimal under the process parameters of rotational speed of 90r/min and drilling pressure of 15kN. This paper provides an analytical method for the subsequent optimization and improvement of the evaluation of the pipe repair process and promotes the technological development of the research on the casing change mechanism and prevention and control countermeasures in shale gas wells.