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A rotating closed loop pulsating heat pipe (RCLPHP) was experimentally investigated as a passive heat sink for rotary equipment cooling. The effects of heat input, rotational speed, filling ratio, and working fluid on the thermal resistance of RCLPHP were studied. Pure water and ethanol were used as working fluids with filling ratios of 30%, 50%, and 70% by volume, and the RCLPHP was tested at four rotational speeds: 200, 400, 600, and 800 rpm. The results showed that the best filling ratio for both water and ethanol is 50% and proved that the RCLPHP is able to work efficiently in a wide range of rotational speed. Moreover, it was observed that at the optimum filling ratio for ethanol and water, which is 50%, the decrease in thermal resistance at 800 rpm compared to 200 rpm was 5.4% and 13%, respectively. Such an enhancement in thermal performance indicates that these types of heat pipes are applicable for the purpose of cooling rotating devices. Moreover, a correlation is presented to estimate the amount of heat flow in RCLPHP with a maximum estimated error of 20%. [ABSTRACT FROM AUTHOR]

Centrifugal investment casting is an attractive method of producing orthopedic implants. This study investigated the effects of low rotational speed of vertical centrifugal investment casting on the microstructural characteristics, porosities and hardness of a titanium femoral knee. The centrifugal investment casting was conducted at 45-65 rpm. The microstructure, defects and microhardness of titanium resulting from centrifugal investment casting were discussed. Experimental results showed that centrifugal casting at a rotational speed of 45-65 rpm could obtain the casting without damaging the surface. The largest inner defect was typically the shrinkage because of the solidification process beneath the smallest parts. The microstructure transformed from a fine grain on the subsurface to a slightly coarse one in the inner region. Microhardness profiles on the cross section presented a decreasing tendency from the surface to the inner region because of the shift of the microstructure. [ABSTRACT FROM AUTHOR]

With the development of micro electro mechanical system (MEMS), the application of micro components is becoming increasingly wide. Micro electrical discharge machining (micro EDM) is one of the most effective manufacturing processes for micro components. During past few decades, some innovative methods for improving micro EDM performance have been proposed. Using special-shaped electrode is just one of them. Although micro EDM with helical electrode has been proposed and the availability has been proved for several years, relatively little is known about the precise effect of helical electrode rotation on micro EDM performance. In this study, micro through-holes were machined on Ti6Al4V sample with a cylindrical electrode and helical electrode. The helical electrode achieves better machining performance overall compared to the cylindrical electrode due to its favorable debris removal ability. The higher the rotational speed of helical electrode, the higher the material removal rate (MRR). When using the cylindrical electrode, the MRR first increases and then decreases after reaching a peak at 3000 rpm. Higher MRR is obtainable with the helical electrode with reverse rotation; with forward rotation, it yields higher machining precision (lower overcut and taper rate). [ABSTRACT FROM AUTHOR]

There have been developments on surface texturing methods providing benefit in a great many engineering applications. Especially, influence on surface texturing in lubrication applications related to frictional properties have been cause of concern. In the present study, it was aimed to work on the computational fluid dynamics (CFD) study of the lubrication system consisting of two parallel plates. While one of the plates was sliding, the other one was stationary and an incompressible two-dimensional single phase flow was assumed between those plates. The scope of the CFD analysis was to determine the relationship between drag force and operating fluid properties (i.e., oil types), rotational speed and the amount of the cavities. It was realized that SAE 0W-30 was found to be the best fluid among the seven studied oil types providing optimal conditions such as high drag reduction and less drag force. It was noticed that the drag coefficient thus, drag force appeared to be increasing as the rotating disk speed rose. The influence of the number of the cavities along the textured surface was also investigated in the present study and it was found that drag reduction was not associated with the number of cavities because 0, 1, 2 and 3 cavities nearly gave the same drag force values. [ABSTRACT FROM AUTHOR]

In this study, a basic mathematical model is presented to describe the flow through the turbine of solar chimney. A 3D CFD simulation of the prototype solar chimney power plant of the Manzanares, considering turbine blades, was performed. The CFD simulation was verified by comparison with the experimental data of the Manzanares solar chimney power plant. Then, to show the effects of the turbine rotational speed, the quantity of turbine blades, the collector diameter and the chimney height, 12 cases of CFD simulations were run. These runs were based on 3, 4 and 5 blades, rotational speeds of 40, 80 and 100 rpm, chimney heights of 100, 200 and 300 m and collector diameters of 122, 244 and 366 m. According to the results of the simulation, the outlet air velocity, the air mass flow rate, the torque and the power are reported. The results show that, with a fixed number of blades, increasing the rotational speed would decrease the mass flow rate of air, and increase the torque and power generated by the turbine. Also, in a constant angular velocity, increasing the blade quantity would decrease the mass flow rate of air and increase the torque and power. Moreover, increasing the chimney height and collector diameter intensifies the mass flow rate and power output. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wave rotor is tried as pressure exchanger for supercritical carbon dioxide. • Unsteady pressure waves in wave rotor does not take high rim speed to do work. • Wave rotor reduce turbomachinery's rotational speed to 8 % and shaft work to 4 % • Wave rotor achieve comparable efficiency and size to turbomachinery. Supercritical carbon dioxide Brayton cycle is emerging as a solution to effective and clean power resources, and the pressure exchanger is a critical part of such cycle. While turbomachinery is the conventional technology of such pressure exchangers, it sustains high shaft work and suffers from especially high rotational speed, which is a key challenge. This work proposed a wave rotor for supercritical carbon dioxide pressure exchanger as an alternative technology of the turbomachinery. Numerical simulation results demonstrate that a wave rotor compresses and expands supercritical carbon dioxide with unsteady pressure waves, so it does not take a high rim speed to do the compression or expansion work like turbomachinery, and a low rotational speed and a low shaft work are available then. According to the design results for a practical compression ratio at 1.93 and a massflow rate at 2.30 kg/s, the wave rotor reduces the rotational speed to 8 % and the shaft work to 4 % of equivalent turbomachines, and the wave rotor has comparable efficiency and size to equivalent turbomachines. This work provides the special advantage and suitability of the wave rotor as a pressure exchanger of the supercritical carbon dioxide Brayton cycle. [ABSTRACT FROM AUTHOR]

• The spray characteristics and droplet distribution of a slinger nozzle were experimentally studied by supplying water and Jet A-1 to understand the slinger nozzle atomization characteristics in actual gas turbine combustors. • The spray behavior was varied as column-, sheet-, and ligament-shaped sprays, due to the nozzle rotational speed and the liquid physical properties. • The change in droplet size of water and Jet A-1 with respect to the rotational speed was crossed at 17,000 rpm, and the dominant variables affecting droplet formation were changed. • As the fuel temperature decreased, the fuel viscosity dominantly affected the atomization process, and the atomized droplet size gradually increased. • The expressions for predicting the droplet size of slinger nozzle were derived, which is applicable to determine the ignition condition of the slinger-type gas turbine combustor, and the R2 values were high in range from 0.94 to 0.96. A slinger nozzle is a device that atomizes fuel using centrifugal force generated by rotation of the gas turbine shaft. This nozzle is easy to design and manufacture and has excellent atomization performance at high speed rotation, making it suitable for small gas turbine engines. In this experimental study, the spray characteristics of a slinger nozzle were investigated using a high-speed camera and a 2-dimensional phase Doppler anemometry (PDA) system, and the velocity components and the mean droplet size (SMD) of the spray were obtained at rotational speeds of 5000 to 30,000 rpm. Water and Jet A-1 were used as working fluids, and due to the difference in the physical properties of the fluids, column- and sheet-shaped sprays appeared, respectively. The sheet-shaped spray was found to be favorable for initial droplet generation. Accordingly, Jet A-1 disintegrated and formed initial droplets faster than water at the spray center of Y/d o = −1 to +1. The droplet sizes of the water and Jet A-1 sprays crossed at a nozzle rotational speed of 17,000 rpm, and thereby, the dominant variables that affect droplet formation, such as viscosity and surface tension, could be identified based on this rotational speed. As the temperature of the Jet A-1 decreased, the sheet-shaped spray changed to ligament-shaped sprays at the nozzle orifice exit, and the droplet size increased due to the increased viscosity, which disturbed the ligament breakup. Finally, mathematical expressions were presented to predict the mean droplet size (SMD) of slinger nozzle sprays based on the previous results and experimental data. These apply to the determination of the ignition condition of the slinger-type gas turbine combustor. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient power supply for hypersonic vehicles, effective cooling of the power generation turbine blades is required. The air is too hot to act as a coolant, so the hydrocarbon fuel carried by the hypersonic vehicle becomes the only coolant. For the problem of low heat transfer capacity of hydrocarbon fuel inside the U-shaped channel with constant cross-section under high rotational speed conditions, a novel trapezoidal channel structure is proposed to enhance the heat transfer capacity under rotational conditions. The numerical results show that the trapezoidal channel with an inclination angle of 2° has the highest thermal performance considering the inlet temperature and rotation speed. Compared with straight channels, trapezoidal channels with an inclination angle of 2° can improve thermal performance by a maximum of 1.5 times. The Coriolis force causes the offset of the hydrocarbon fuel, which can significantly enhance the heat transfer capacity of the channel. For straight channels, the Coriolis force only has a significant effect on the first flow channel. However, for trapezoidal channels, the Coriolis force has a significant effect on both the first and second flow channels. • A novel hydrocarbon fuel trapezoidal cooling structure is established. • Channels with 2° inclination angle can improve thermal performance by a maximum of 1.5 times. • Trapezoidal channels reduce the "wing type counterflow" region. • Coriolis force affects both the first and second flow channels. • The convective heat transfer coefficient rises with the increase of the inclination angle. [ABSTRACT FROM AUTHOR]

The rotational speeds of an electromagnetic stirrer was varied to control the growth of particle size of neodymium-doped yttrium aluminum garnet (Nd:YAG) precursors into calcined powder. First, the Nd:YAG precursors were prepared using a chemical co-precipitation technique with different electromagnetic stirrer's rotational speeds, and then the precursors were calcined at different temperatures to obtain Nd:YAG nanoparticles. The precursors obtained from different co-precipitation conditions were heated from room temperature to 1000 °C, and then the phase evolution was analyzed through differential scanning calorimetry. The formation of YAG phase at different calcination temperatures was analyzed through X-ray diffraction. The size of Nd:YAG nanoparticles prepared at different electromagnetic stirrer's rotational speeds were analyzed using by particle size analyzer and scanning electron microscope. The experimental results indicated that the size of Nd:YAG nanoparticles could be controlled at approximately 300 nm when the Nd:YAG precursors were prepared from an electromagnetic stirrer rotational speed at 400 rpm and then calcined at 1300 °C. The obtained smaller particles size can be attributed to a homogeneous flow field within the mixing solution. [ABSTRACT FROM AUTHOR]

Centrifugal slurry pump is widely used for transportation of solids through pipeline in many chemical and mining industries. Erosion wear considered as one of the important parameter which plays significant role in slurry transportation system by affecting both initial cost and life of its components. In the present work, erosion wear due to solid–liquid mixture has been investigated using a slurry erosion pot tester. The erosion tests have been conducted on centrifugal slurry pump material stainless steel (SS304) to establish the influence of rotational speed, particle size, solid concentration and time duration. Sand and fly ash were taken as erodent materials with solid concentrations ranging from 30 to 60% (by weight). The experiments were performed at four different speeds namely 600, 900, 1200 and 1500 rpm with time duration of 90, 120, 150 and 180 minutes. WC–10Co–4Cr and Ni–20Cr 2 O 3 coating powders were used to increase the erosion wear resistance. Coating powders are deposited on pumping material by supersonic flame of high velocity oxygen fuel (HVOF) coating. Experimental results indicate that erosion wear has high dependence on rotational speed, time duration and nature of erodent solid particles. Significant improvement in erosion wear resistance was also observed by using WC–10Co–4Cr coating over Ni-20Cr 2 O 3 . [ABSTRACT FROM AUTHOR]

In this work, nonequilibrium molecular dynamics (NEMD) simulations are performed to investigate liquid argon flow past rotating carbon nanotube and to estimate flow forces on the nanotube. In molecular dynamics simulation, fluid forces on a floating body are calculated directly from summation of the molecular forces exerted on solid atoms by fluid atoms and this method is used also herein. Based on this method, an in-house, parallel MD code was developed to calculate drag and lift forces exerted on a carbon nanotube and investigate fluid atoms positioning around it, in a uniform flow of liquid argon. The simulation is 3-dimensional and consists of 33,669 liquid argon atoms which represent the fluid and 240 carbon atoms as the nanotube for different domain setups used in this work. The single walled carbon nanotube is simulated as a rigid cylinder of fixed carbon atoms. For simulation of rotating nanotube, carbon atoms are rotated around axis of the nanotube in each time step according to its rotational speed. Both argon-argon and carbon-argon interactions are modeled by the Lennard-Jones potential function. Periodic boundary condition is used for the whole system. Flow is driven by rescaling atoms velocity at inlet region each 50 time steps. Drag coefficient on stationary carbon nanotube in some situations are compared with that of Tang and Advani (2006) and so the in-house code is verified. Results indicate that when the nanotube is stationary, drag force increased with inlet flow velocity and lift force almost fluctuated around zero value. At higher inlet velocities, these fluctuations damped and lift force converged to exact zero value. It was also found that drag coefficient exerted on carbon nanotube always reduced with its rotational speed. This reduction was more significant at lower inlet flow velocities and as flow velocity increased, this phenomenon occurred with a lower rate of reduction. Rotational speed did not have significant effects on lift force in comparison to its effects on drag force and so it is neglected. Rotation of carbon nanotube has changed atoms positioning around the nanotube and so atomic density in the nearby bins. [ABSTRACT FROM AUTHOR]

This paper investigates the variations of mode I stress intensity factor (KI) for inner penny-shaped and circumferential cracks in functionally graded solid and hollow thick walled cylinders, respectively with the changes of crack geometry, material gradation and loading conditions. The functionally graded material of cylinders consists of epoxy and glass. It is assumed that the mechanical properties vary with a power law in the radial direction of cylinders. Micromechanical models for conventional composites are used to estimate the material properties of functionally graded cylinders. The equations of motion obtained from the extended finite element discretization are solved by the Newmark method in the time domain. The interaction integral method is employed to calculate the mode I stress intensity factor (KI). The MATLAB programming environment was implemented to solve the problem. [ABSTRACT FROM AUTHOR]

In electrochemical machining (ECM), a passive film is generally present on the anode surface at low current density but is broken down at high current density in a passivating electrolyte. This film can impede unwanted metal dissolution in a low-current-density region and thereby improve the accuracy of ECM. However, it may sometimes affect metal dissolution at high current density. In this paper, the breakdown time of the passive film is determined for different current densities by varying the applied anodic potential pulses. It is found that the breakdown time has a significant magnitude of a few seconds, which can be long enough to affect metal dissolution in ECM. To illustrate the effect of the breakdown time of a passive film, ECM tests with cylindrical electrodes at different rotational speeds are conducted. The results indicate a correlation between the breakdown time and the rotational speed. At a high rotational speed, the surface of the anode workpiece is always in a passive state due to the existence of the breakdown time of a passive film, and hardly any material is removed. When a slower rotational speed is used, the steel passivity can be overcame, and a high material removal rate is obtained. A numerical simulation of the current density distribution on the cylindrical anode surface is performed, and the relationship between total metal dissolution time and breakdown time is found. It is seen that the breakdown time of the passive film can have a strong effect on the metal removal rate in ECM. [ABSTRACT FROM AUTHOR]

The effect of rotational and traverse speeds during dissimilar butt friction stir welding of Al 5083-H321 and 316L stainless steel plates was studied. The macrostructure and microstructure of the joints were examined using optical microscope and scanning electron microscope equipped with energy-dispersive X-ray analysis. The strength of the joints was measured using tensile test. The results showed that with increasing the rotational speed, the tensile strength of the joints increased up to a maximum value and then decreased. In addition, decreasing the traverse speed resulted in higher tensile strength. The 238-MPa maximum value of the tensile strength was achieved at rotational speed of 280 rpm and traverse speed of 160 mm/min. The formation of surface and cross section defects at lower rotational speeds and higher traverse speeds and existence of cracks and microcracks at higher rotational speeds were responsible for the lower tensile strengths of the corresponding joints. In addition, the FeAl intermetallic compound was detected in the interface of the steel particles and Al. [ABSTRACT FROM AUTHOR]

Interactive erosion and cavitation wear widely exist in engineering. Based on the principle of orthogonal experiment, flow pressure, erosion angle, and rotational speed are selected for the interactive erosion and cavitation wear experiment on plastic material 40Cr, 45 steel, and brittle material HT200 using the L9 (3x4) orthogonal experiment table. The wear loss and the SEM (scanning electron microscope) photo of the specimen are also analysed. The result shows that the main factors that influence interactive erosion and cavitation wear loss are flow pressure, erosion angle, and rotational speed from primary to secondary. For 40Cr and 45 steel, the difference in the R value between the three factors is small. For HT200, the R value of pressure on interactive wear is the highest, which is signifi- cantly different from the R value of rotational speed. Under the same rotational speed, erosion angle, flow pressure, and other environmental factors, cavitation caused by pressure is the major wear form for brittle materials with smaller elongation. The impact strength of micro-bubble collapse can easily reach its fatigue strength. Materials peel off in patches under repeated impacts of micro-bubble collapse and sand grains, which aggravates the degree of interactive wear. The anti-cavitation capacity of the plastic materials with large elongation is strong, with erosion wear, to a lesser degree. [ABSTRACT FROM AUTHOR]

This paper deals with numerical study of filter cake formation and fluid loss on the borehole walls during an over-balanced drilling operation. Filter cake formation is a result of three interlinked phenomena; free flow of drilling fluid in the annulus, porous flow of filtrate through the formation and mud solids deposition on the well's wall. A numerical approach is developed for modeling and simulation of the cake growth, in which, initially, a three-dimensional non-Newtonian flow field of power law drilling mud is computed using finite difference method, and then, radial permeation of the filtrate and the rate of cake growth is accomplished by an explicit Runge-Kutta method. Extensive computer runs was carried out to investigate the effect of free flow parameters on the cake thickness profile and the simulation results indicated that, unexpectedly, increasing drill string rotation in a concentric case (within the conventional range of parameters for drilling operation) has almost no effects on cake thickness and permeate velocity. By increasing eccentricity, the effect of drill string rotation increases and a maximum and minimum cake thickness occurs in widening and narrowing gap, respectively. However, this impact can be neglected in high rotation rate. The effect of drill string and particle radius was studied as well. [ABSTRACT FROM AUTHOR]

Disc cutter is the main rock breaking tool of TBM. It is angled worn frequently because of locked-rotor; as a result, monitoring relevant operating parameters of TBM disc cutter has become an urgent technical problem. This paper studies nondestructive and non-contact online detection disc cutter rotational speed method of based on eddy current sensor: applies eddy current sensor to detecting six 2 mm-high metal bumps setting on the disc cutter, so as to detect the rotational speed of disc cutter. K60 MCU is applied as the main control core. The experimental results show that the on-line rotational speed monitor system of disc cutter features high anti-jamming ability and is reliable. [ABSTRACT FROM AUTHOR]

The activity of wheel-throwing a ceramic vessel is governed by a number of physical forces. These are the rotational kinetic energy (expressed in terms of angular velocity and the moment of inertia) and manual pressures. Given the importance of the potter's wheel worldwide, and the frequently postulated socio-cultural meaning of wheel-throwing in particular, foundational research on the physics behind wheel-throwing has been under-represented, and there is a lack of understanding of the relationship between speed of wheel rotation, lifting speed and the orientation of clay pores or inclusions. The speed of rotation is highly relevant as different wheels can achieve different speeds. Thus, knowing the speed during manufacture may allow scholars to reconstruct the original device, manufacturing technique, and perhaps even the potter's level of skill. Two contrasting views can be found in the literature: a) there is a direct positive relationship between these variables, and that the angle of the inclusions/voids can therefore tell us about the wheel's speed at the time of making the pot and hence the device used; b) because pots are never thrown in one single motion, the angle of inclusions/voids is an averaging of all actions executed by the potter, and thus cannot provide meaningful inferences about speeds or device. Experiments with professional potters were devised to explore the relationship between these variables. They show that the interaction between the various physical forces, clay and potter is complex, leading to a large variance even within the work of a single potter, with finger pressure recognized as a major influencing variable. It is clear that angles of inclusions or voids cannot be used to project backwards to the wheel speed, lifting speed, skill level or device used. • Diagonal angle alignment of inclusions or voids identifies a vessel as wheel-thrown • Inclusion/void orientation does not allow retrospective deductions on wheel speed, lifting speed, the device used or a potter's skill • Inclusion or void orientation varies intra- and inter-potter • Finger pressure is most likely responsible for the steep inclusion or void orientation characteristic of wheel-throwing [ABSTRACT FROM AUTHOR]

Double-sided lapping process is a key technology for obtaining high efficiency and flatness in fabricating plane-parallel workpiece surfaces, such as wafers, optical windows, seal rings, etc. However, the formation of the concave and convex surface shapes of workpieces was rarely investigated in the previous research, and the mechanism was unknown. This paper establishes a new kinematic model to clarify the formation mechanism of concave and convex surface shapes, in which the workpiece eccentricity and rotation in the planetary wheel are considered for the first time. The measurement and control method of workpiece rotational speed in the planetary wheel is proposed. The formation of the concave and convex surface shapes is validated experimentally by adjusting the rotational speed of the workpiece, and the results show a good consistency with the calculation results. A flatness error convergency method is proposed based on the surface shape formation mechanism, and flatness superior to 5 µm is achieved on Φ200 × 2 mm thin copper substrates. [Display omitted] • The formation mechanism of convex and concave surface shapes is clarified. • Workpiece's eccentricity and rotation are supplemented to general kinematic model for the first time. • The measurement and control methods for workpiece rotational speed are developed. • A flatness error convergency method is proposed. • Flatness superior to 5 µm is achieved on Φ200 × 2 mm thin copper substrates. [ABSTRACT FROM AUTHOR]

The effect of the rotational speed and dwell time on the joint interface microstructure and tensile-shear strength of friction stir spot welded Al-5083 aluminum/St-12 steel alloy sheets was investigated. Joining of the sheets was performed using an alternative friction stir spot welding (FSSW) process in which the welding tool tip did not penetrate into the lower steel sheet. Rotational speeds of 900 and 1100 rpm were applied in association with the dwell times of 5 to 15 s to weld the samples. Thermal history was recorded during the joining process. Interfacial microstructure, formation of intermetallic compounds (IMCs) at the joint interface and the fracture locations were studied using stereo, optical and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The used alternative process was successful to join the sheets. For both of the applied rotational speeds, there were optimum dwell times (10 and 12 s for the rotational speeds of 1100 and 900 rpm, respectively) to reach the maximum failure loads. The increasing trend of the strength as a function of the dwell time was related to the formation of a thin intermetallic (IM) layer at the joint interface. The decreasing trend was attributed to the formation of a relatively thick IM layer at the joint interface as well as the grain growth of aluminum at the exit-hole periphery where the final fracture occurred. The IM reaction layer thickness of 2.3 μm was found to be a critical thickness. Compared to the rotational speed of 1100 rpm, stronger joints were achieved by application of 900 rpm rotational speed. [ABSTRACT FROM AUTHOR]

Aim To compare the shaping ability of four different nickel-titanium rotary instruments during the preparation of curved root canals in extracted teeth. Methodology A total of 80 root canals with curvatures ranging between 25° and 39° were divided into four groups of 20 canals. Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared to a final apical size of 40 using Mtwo, Pro Taper Universal, Pro Taper NEXT and BT- Ra Ce. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures and canal transportation were determined with a computer image analysis programme. Preparation time and instrument failures were also recorded. The data were analysed statistically using anova and Student- Newman- Keuls test. Results The use of BT- Ra Ce files resulted in significantly more straightening during instrumentation compared to Mtwo ( P < 0.05), whilst the differences between all other instruments were not significant ( P > 0.05). No significant differences were obtained between all four instruments regarding canal transportation ( P = 0.429). Instrumentation with Pro Taper NEXT files was significantly faster than with all other instruments ( P < 0.05). During the preparation of the curved canals, one BT2 instrument fractured, whilst no fracture occurred when using the other instruments ( P > 0.05). Conclusions Within the parameters of this study, all instruments maintained root canal curvature well and were safe. However, care should be taken when using the BT2 instrument due to its unique cylindrical design. [ABSTRACT FROM AUTHOR]

Study Design. In vitro animal cadaveric study. Objective. To identify the appropriate rotational speed and safe bone distance from neural tissue during bone burring in spinal surgery. Summary of Background Data. Bone burring is a common step in spinal surgery. Unwanted frictional heat produced during bone burring may result in thermal injury to the bone and adjacent neural structure. One of the important parameters influencing the bone temperature rise during bone burring is rotational speed. Methods. This laboratory-based animal study used bovine spine bones, and the tests were conducted using a steel round burr. The bone temperature was measured simultaneously with thermocouple at the distances of 1 mm, 3 mm, and 5 mm from the burring site during the burring process. The bone burring was done with 4 different rotational speeds of 35,000 revolutions per minute (rpm), 45,000 rpm, 65,000 rpm, and 75,000 rpm. Results. This study showed that increasing the rotational speed significantly elevated bone temperature. The threshold temperature of 47°C was reached when bone was burred for 10 seconds, with a rotational speed of 45,000 rpm. The mean bone temperature measured at a distance 1 mm from the burring site for all 4 rotational speeds was always higher than that measured at a distance of 3 mm and 5 mm and this difference was statistically significant (P < 0.001). There was no significant difference between the mean bone temperature measured at a distance of 3 mm and 5 mm (P > 0.05). Conclusion. Taking 47°C as the threshold temperature for causing significant impairment to the regenerative capacity of bone, a rotational speed of lower than 45,000 rpm is preferable so as to minimize thermal injury to bone tissue. We also concluded that a 3-mm distance between the site of burring and the neural tissue is a safe distance. [ABSTRACT FROM AUTHOR]

With reductions in the pressure ratio of the fan and increases in bypass ratio of the turbofan in recent years, the engine windmilling and relight capability have attracted more and more attention in aviation safety. This paper proposes a combination of the speed model and CFD to examine the internal flow evolution of the wide-chord fan under the windmilling condition. Firstly, we establish a semi-empirical speed model for predicting the fan rotational speed of a high-bypass ratio turbofan at any flight Mach number and altitude based on the flow characteristics of a windmilling fan. The model can provide an initial windmilling airflow at the specified speed for subsequent CFD calculations to reduce the number of iterations. Then, a three-dimensional CFD model is proposed to obtain the operating boundary of the windmilling fan according to the direction of energy transfer between the fan and the airflow. The mechanisms of fan internal flow evolution and tip leakage flow when it operates at a constant speed line were analyzed. The results show that the work distribution profiles along the blade span exhibited self-similarity. The fan blade operated in both spanwise and chordwise mixed configuration. The flow moved gradually from compressor-like regions near the hub to turbine-like regions near the shroud, where the stirrer mode was the transitional stage between them during windmilling. When the rotor entered the windmilling, it operated at a significantly off-design angle of attack, that caused a large area of flow separation to occur near the pressure surface (PS) instead of on the suction surface (SS). The flow separation and loss gradually increased from the hub to the shroud. Meanwhile, the direction of tip leakage flow also changed, a streamwise vortex core was observed on the PS near the blade tip. The core mixed with the low-energy fluid on the PS, resulting in flow blockage, that changed the working profile of the rotor. As the mass flow rate increased to the turbine operating point, the intensity of interaction and influence area between the leakage flow and the main flow further increased, and the aerodynamic loss increased significantly. [ABSTRACT FROM AUTHOR]

• Gas-liquid two-phase flows were studied in a centrifugal pump. • Effects of the rotational speed were thoroughly studied. • Hysteresis, head degradation, surging, and flow instabilities were considered. • The two-phase flow regimes were recorded and identified using a high-speed camera. • Increasing rotational speed leads to various improvements in two-phase pumping. This study presents experimental and numerical investigations on air-water flows in a centrifugal pump, extending our previous studies. The main objective of the present article is to examine the influence of rotational speed on pump performance. For that purpose, the pump performance was considered and extensively compared for two different rotational speeds, i.e., 650 rpm and 1000 rpm, covering different single and two-phase flow conditions. To allow flow visualization, the impeller and the pump body were manufactured from transparent materials, and a high-speed camera was employed for recording the two-phase flow regimes. The performance of the pump was illustrated and reported for either a constant gas volume fraction or a constant air flow rate at the pump inlet. The desired operating conditions at the inlet were achieved using various predetermined experimental procedures to study the performance hysteresis. Pump surging and breakdown conditions were also considered. Additionally, 3D URANS single-phase numerical simulations were performed to explain additional internal flow details. The moving-mesh approach combined with the k - ω SST turbulence model has been used for that purpose. The simulations agree well with the experiments in most cases. Overall, the results show that increasing the rpm enhances two-phase mixing, which leads to various and significant improvements regarding two-phase pumping performance. [ABSTRACT FROM AUTHOR]

Double groove ball-section ring is an important part of complex profiled-section rings and has been widely used in energy industries, and cold double groove ball-section ring rolling is a new plastic forming technology that can directly fracture seamless double groove ball-section rings with high-precision and high-performance. Because the speed parameters (including the rotational speed of driving roll and the feed rate of mandrel) affect the feed amount per revolution and play important roles in the stability of cold double groove ball-section ring rolling process and the quality of deformed double groove ball-section ring production, the effects of speed parameters on the variation of ring configuration and the variation of strain in cold double groove ball-section ring rolling process are investigated. The obtained results provide valuable guidelines for the selection of speed parameters in the practical cold double groove ball-section ring rolling process. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the effects of rotational speed on rolling wear and damage behaviors of wheel/rail materials using a rolling–sliding wear testing apparatus. The results indicate that, with the rotational speed increasing, the surface hardness of rail roller remains unchanged while the increase of surface hardness of wheel roller declines resulting in a decrease of wheel/rail hardness ratio. The wear loss of wheel roller increases while the wear loss of rail roller declines with increasing rotational speed. The worn surface of rail roller exhibits peeling and spalling damage. Fatigue cracks and adhesive wear are dominating for the worn surface of wheel roller. Furthermore, with the speed increasing the fatigue damage lightens and adhesive wear worsens for the wheel roller. Fatigue cracks of wheel rollers grow along with soft ferrite lines in plastic deformation area. Cracks of rail rollers tend to turn towards the worn surface. There are visible branch cracks and multilayer cracks on the surface of wheel/rail rollers. Branch cracks of wheel rollers are longer than that of rail roller, and the interlayer material of multilayer cracks is easy to break. Wear debris of wheel/rail rollers is composed of Fe 2 O 3 and martensite. The size of debris with flakes structure decreases and the martensite content increases with the rotational speed increasing. [ABSTRACT FROM AUTHOR]

The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant. Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500 rpm with original (∅ 250 mm), 10% trimmed (∅ 225 mm) and 20% trimmed (∅ 200 mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational speed in non-dimensional form. [ABSTRACT FROM AUTHOR]

Ethanol production from starchy cereal grains is increasing rapidly due to increasing demand for alternative fuels. In Canada, wheat is the primary feedstock in ethanol plants. To improve the productivity of the ethanol plants in terms of product quality and yield, debranning of wheat grains may be employed. Debranning is advantageous in two ways. Firstly, bran removal increases the starch content of the feedstock, improving the fermentation efficiency of the ethanol plants. Secondly, bran, a valuable co-product can be used as an animal feed ingredient. In this study, experiments to optimize the debranning process were carried out using two kinds of abrasive equipment, the Satake and the TADD (tangential abrasive dehulling device) mills. Wheat samples (30 and 200 g) were debranned in the Satake mill at 1 215, 1 412, and 1 515 r/min rotational speeds, 30, 36, and 40 grit sizes, and 30, 60, and 90 s retention times, and in the TADD mill at 900 r/min rotational speed, 30, 36, 50, and 80 grit sizes, and 120, 180, 240, and 300 s retention times. In addition to debranning efficiency, the starch separation efficiencies of the two mills were calculated in different debranning conditions. In the Satake mill, the 30 g and 200 g sample size, 1 412 r/min and 1 515 r/min rotational speeds, all grit sizes, and 60 s of retention time demonstrated the highest debranning efficiency. Correspondingly, optimal results in the TADD mill were obtained with 200 g sample size, 900 r/min rotational speed, 50 and 80 grit sizes, and 180 s and 240 s retention times. However, based on the experimental results, Satake mill provided better debranning values compared to the TADD mill. The starch separation efficiency values supported these results. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear vibration characteristics of spur gear-rotor system and the interactions among of gear shaft, and bearing with backlash subjected to internal/external excitation are systematically investigated. The two-degree-of-freedom purely torsional generalized lumped parameter model of the spur gear system with meshing stiffness, backlash, transmission error and external periodic excitation is established. The Newmark method is used to solve simultaneously the differential equations for analysis the vibration response characteristics as well as the effects of rotational speed, backlash and mesh damping coefficient on the dynamic characteristics of the spur gear system. The numerical results clearly reveal that the system exhibits an increase mesh damping coefficient and a decrease backlash can reduce the degree of gear nonlinearity effect, which makes the meshing state of spur gear system change from double-sided impact, single-sided impact to no impact. In addition, the rotational speed has a significant effect upon the dynamic response of the system, which shows that designing a gear system to operate at a high rotational speed should be avoided especially when the rotational speed is close to the system's natural frequency and half of the natural frequency. The results presented in this study provide an understanding of the operating conditions under which undesirable dynamic motion takes place in a spur gear system and therefore serve as a useful source of reference for engineers in designing and controlling such systems. [ABSTRACT FROM AUTHOR]

In this paper, the unsteady 3-D turbulent flow fields in an end-suction centrifugal pump with a vaneless volute are studied numerically at three different rotation speeds. The unshrouded impeller of the pump, as a reduced diameter version of the original full-size impeller, has five backswept blades and five pump-out blades. The results show that the flow rate and pressure vary with the rotational speed according to the similarity law, and the normalized internal flow fields at all speeds are very similar. Due to the reduced impeller diameter, the pump efficiency is relatively low. Flows discharged from the front and back blade passages interfere with each other and swirling motion exists in the volute. The pressure fluctuations on the casing wall near the impeller outlet are extracted, and their spectra show that the component at the blade passing frequency was prominent. This study sheds some light on the characteristics of the internal unsteady flow of a centrifugal pump at different rotational speeds, and forms a basis for future study of flow induced pump vibration and noise. [ABSTRACT FROM AUTHOR]

This paper presents the experimental observation results of contact-induced vibration (CIV) and its compensator design in dual-stage hard disk drive servo systems, where the vibration is caused by the continuous contact of read/write head and recording media. Consistent relationships between the center frequencies and magnitudes of the vibration modes and the tested fly height, rotation speed, and track position are clearly observed and analyzed. It reveals that the CIVs excite and amplify only the resonance modes of the system. In consequence, the so-called PQ method is adopted to perform the compensator design. As such, the relative contributions to system output from the voice coil motor and lead–zirconium–titanate actuator subsystems can be well assigned in the frequency domain. The remarkable performance of the well-designed compensator is demonstrated by simulation. [ABSTRACT FROM PUBLISHER]

The interaction between the Coriolis and mistuning effects on a finite-element model (FEM) of a simplified bladed drum compressor has been investigated in this paper. The Subset of Nominal Modes (SNM), the Component Mode Mistuning (CMM) and the Integral Mode Mistuning (IMM) techniques have been chosen and adapted to consider the reduction of the Coriolis matrix. Both free and forced responses of the ROMs have been validated using the FEM solutions as the benchmark. A new analysis using Monte Carlo simulations has been performed to consider disc and blade mistuning independently, and to study the domination of one over the other. The impact of the Coriolis effect has been highlighted through observation of the model with and without the Coriolis matrix. The evolution of the global dynamic behaviour with rotational speed has been investigated for the first time for different excitation frequencies and engine orders (EO). This in-depth investigation of a blisk allowed a better understanding of the interaction between the Coriolis and mistuning effects. The blade-dominated responses and the modes which remain close to the veering regions have strong mistuning effects, with significant localisation and amplitude magnification. The results mainly highlight that the disc-dominated and the blade–disc responses tend towards a tuned behaviour with the appearance of travelling waves. [Display omitted] • A validation of three ROMs with the Coriolis effect is conducted on a mistuned blisk. • The impact of the Coriolis effect on the response of a mistuned blisk is highlighted. • The IMM method allows to account for both blade and disc imperfections. • The behaviour of a mistuned blisk may tend to that of a tuned blisk due to Coriolis. [ABSTRACT FROM AUTHOR]

Phase demodulation is arguably the most used technique for the estimation of the instantaneous angular speed from vibration signals measured on rotating machinery. Although phase demodulation offers a straightforward approach to determine accurately the rotation speed of a particular shaft in a rotating machine, it does have strict limitations that can hinder the estimation accuracy and its overall reliability. In general, phase demodulation relies on the presence of a single harmonic with a high signal-to-noise ratio for the full duration of the measured vibration signal. Such a precondition hinders its applicability for a generic speed estimation approach for rotating machinery. There are copious real-world scenarios where this requirement is not met, especially given the increasing complexity and dynamic operating range of rotating machines nowadays. In such complex rotating systems, the deterministic signals are not necessarily all harmonically related to a fundamental harmonic. The presence of crossing harmonic orders from non-synchronous rotating components or of lightly damped structural resonances can significantly skew the instantaneous phase demodulation. This paper proposes a novel approach towards phase demodulation by both incorporating multiple harmonics in the demodulation process and also giving the individual harmonic phases time-dependent weighting. This combination of incorporating multiple harmonics and weighting them allows for fully exploiting the information contained within the vibration signal while also promising to be more robust to changing operating regimes. The proposed multi-harmonic demodulation method is investigated thoroughly by assessing its performance on simulated data, on two benchmark experimental data sets, and on a large wind turbine vibration data set consisting of thousands of vibration measurements. • Multi-harmonic extension of standard single harmonic phase demodulation. • Maximum likelihood weighting of harmonics improves accuracy and ease-of-use. • Validation on simulated and experimental data sets. • Good performance on complex non-stationary machine vibrations. [ABSTRACT FROM AUTHOR]

• Hollow Conical Frustum was used to ameliorate pool boiling heat transfer. • Heat transfer coefficient enhancement of 19.8% in stationary mode was obtained. • Heat transfer coefficient enhancement of 1302 % in rotating mode was obtained. • There is an optimum heat flux at which the maximum PBHTC occurs in rotating mode. • There is an optimum distance between the conical frustum and the boiling surface. Pool boiling heat transfer as a promising heat transfer mechanism that can provide ample heat dissipation for thermal management applications has been granted much attention. This study puts forward the idea of applying an Inner Corrugated Hollow Conical Frustum (ICHCF) to ameliorate pool boiling heat transfer. The performance of the ICHCF is experimentally investigated for both the stationary and rotating cases. Furthermore, the effect of various geometrical parameters such as the ICHCF height, thread depth, thread pitch, the gap between the ICHCF and boiling surface, and the rotational speed of the ICHCF are studied. Twelve different ICHCFs were fabricated and tested for the purpose of this study. The obtained results demonstrated that increasing the ICHCF height enhances the pool boiling heat transfer coefficient (PBHTC). It was also observed that there is an optimum distance between the conical frustum and the boiling surface. The results also revealed that using smaller pitches and higher thread depths can further improve the PBHTC. The PBHTC enhancement of up to 19.8 % in stationary and 1302 % in rotating modes was obtained compared to a plain surface. [ABSTRACT FROM AUTHOR]

To investigate the erosive wear-corrosion behavior of ZTA P ceramic reinforced high chromium cast iron matrix composites in two types of sand at various rotational speeds, the ZTA P /Fe composites were fabricated. The interface characteristics, erosion wear-corrosion and erosive wear mechanism have been investigated in a slurry condition at various erosion rotational speeds. The chemical composition of the matrix material was determined using a spark spectrometer. SEM, TEM, 3D laser scanning microscope and AFM were used to analyze the microstructure characteristics and worn surface morphology of the composites. Furthermore, the wear loss rate and relative erosive wear resistance of ZTA P /Fe composites and Cr15 standard specimen measurements were conducted. The results showed that the interface between the ZTA P ceramics and the Cr15 matrix exhibits a continuous transition layer without visible defects and close contacts. In the case of SiO 2 and SiC abrasive sand, the wear rate of ZTA P /Fe composites and Cr15 standard specimens increases with erosion time. The wear rate of ZTA P /Fe against SiO 2 sand is lower than that of against SiC sand. ZTA P /Fe composites was found to exhibit a better corrosion resistance property than that of Cr15 standard specimens. [Display omitted] • A continuous transition layer and tightly contacts without visible defects, ensuring an excellent interfacial bond. • The addition of the ZTA ceramics can improve the corrosion resistance performance of high chromium cast iron. • For SiO 2 sands, the relative erosive wear resistance of the composites reaches 1.68–2.43 times the reference Cr15matrix. • For SiO 2 sand, the erosive wear mechanism of composites is the fatigue wear and corrosion of the iron matrix. [ABSTRACT FROM AUTHOR]

Aim To develop a method to evaluate the cutting behaviour of nickel-titanium ( Ni Ti) coronal flaring instruments. Methodology Bio Ra Ce BR0 ( BR), Hy Flex CM 1 ( HY), Pro File OS No. 2 ( PF) and Pro Taper Sx ( PT) instruments were used in simulated coronal flaring using a lateral action against bovine dentine blocks, at 250 and 500 rpm. Cutting efficiency was assessed by three methods: first, areas of notches produced by instruments were directly measured under a stereomicroscope. Second, dentine specimens were then analysed by surface profilometry to determine the maximum cutting depth and finally by microcomputed tomography to assess the volume of removed dentine. Data were compared using parametric tests with the significance level set at 0.05. Results For all three methods, HY and PF were the most and the least cutting-efficient instruments, respectively ( P < 0.05). Significant differences were detected between 250 and 500 rpm for HY and PT (area); for BR, HY and PT (depth); and for BR and HY (volume). There were strong positive correlations between the results obtained with those three different methods with r-values ranging from 0.81 to 0.92. Conclusion Measuring the amount of material removed in a specific time under stereomicroscopy is a simple and rational way to assess the cutting behaviour of Ni Ti rotary instruments in lateral action. Hy Flex, manufactured with thermomechanically treated Ni Ti wire, was the most efficient instrument, and increased rotational speed was associated with increased cutting efficiency. [ABSTRACT FROM AUTHOR]

Aim To evaluate the effect of rotational speed on cyclic fatigue of Mtwo nickel-titanium files. Methodology A total of 120 new Mtwo rotary instruments sizes 10, 0.04 taper; 15, 0.05 taper; 20, 0.05 taper; and 25, 0.06 taper were randomly divided into three groups on the basis of the rotational speed used to shape nine standardized simulated canals: group A = 350 rpm; group B = 250 rpm; group C = 150 rpm. Each group consisted of 40 instruments, 10 for every size. The average preparation time (in seconds) and the average correlated numbers of cycles to instrument ( NCI) the nine standardized canals were recorded for each file. The resistance to cyclic fatigue was determined by counting numbers of cycles to failure ( NCF) with a rotational speed of 300 rpm in a 60° curve with a 5-mm radius. Data were analysed by two-way anova. Results Preparation time was significantly longer at 150 rpm than at 250 or 350 rpm. The average number of cycles needed for each file to instrument nine standardized canals was significantly higher at 350 and 250 rpm, than at 150 rpm. There were no significant differences in the NCF ( P > 0.05) between A, B and C groups for instruments of the same size. Conclusions Speed did not affect the cyclic fatigue of Mtwo instruments with the same size and taper. Preparation time was shorter at 350 or 250 rpm rather than at 150 rpm. However, there was no significant difference between 350 and 250 rpm rotational speed, neither in the preparation time of simulated canals nor in the resistance to fatigue fracture. [ABSTRACT FROM AUTHOR]

Nowadays, there has been an inercasing application of pruning robots for planted forests due to the growing concern on the efficiency and safety issues. Power consumption and working time of agricultural machines have become important issues due to the high value of energy in modern world. In this study, different multi-layer back-propagation networks were utilized for mapping the complex and highly interactive of pruning process parameters and to predict power consumption and cutting time of a force control equipped robotic pruning machine by knowing input parameters such as: rotation speed, stalk diameter, and sensitivity coefficient. Results showed significant effects of all input parameters on output parameters except rotational speed on cutting time. Therefore, for reducing the wear of cutting system, a less rotational speed in every sensitivity coefficient should be selected. [ABSTRACT FROM AUTHOR]

Rotational speed is a key parameter for the condition monitoring and control of rotating machineries, such as generators, electromotors, and centrifugal and machine tool spindles. It is essential for precision machining and early warning of faults to measure rotational speed in real time. This paper presents the principle and application of electrostatic sensors and correlation signal processing techniques to real-time measurement of rotational speed. The electrostatic sensors and signal conditioning and processing units were designed and implemented. Experimental tests were conducted on a laboratory-scale test rig under a range of conditions including different diameters of the shaft. The results obtained suggest that the distance between the electrodes and the surface of the rotating object is a key factor affecting the performance of the measurement system. The system performs better in terms of accuracy and repeatability at a higher rotational speed (>1000~r/min) as more electrostatic charge is produced on the rotating surface. High and stable correlation coefficients acquired during the tests suggest that the measurement system is capable of providing reliable measurement of rotational speed under realistic industrial conditions. [ABSTRACT FROM PUBLISHER]

This article reports the results of applying the response surface methodology to evaluate the tensile strength in joints obtained by the process of friction-stir welding (SFA), depending on the speed of rotation of the tool and welding speed. The joints were welded with a conventional milling machine capable DECKEL FP4M 3 HP and a threaded cylindrical pin. In the microscopic images clearly shows the effect of the dynamic recrystallization in the stirred zone (ZA). Microhardness profiles show the typical shape of W and with metallography performed on samples tested at tension that Heat Affected Zone (HAZ) is the weakest microstructural areas of the join. The greater tensile strength of the welded joints of the aluminum alloy AA 6261-T5 by SFA (191.63 MPa) was obtained using the threaded cylindrical pin, a welding speed 315 mm / min and a rotation speed of 1600 rpm. [ABSTRACT FROM AUTHOR]

To investigate the influence of Centrifugal Counter-gravity Casting (C3) process on the solidification microstructure and mechanical properties of the casting, A357 aluminum alloy samples were produced by different process conditions under C3. The results show that C3 has better feeding capacity compared with the vacuum suction casting; and that the mechanical vibration and the convection of melts formed at the centrifugal rotation stage suppress the growth of dendrites, subsequently resulting in the refinement of grains and the improvement of mechanical properties, density and hardness. A finer grain and higher strength can be obtained in the A357 alloy by increasing centrifugal radius and rotational speed. However, casting defects will appear near the rotational axis and the mechanical properties will decrease once the rotational speed exceeds 150 r·min-1. [ABSTRACT FROM AUTHOR]

Friction welding is widely used as a mass production method in various industries. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Pulsating heat pipes (PHPs) are interesting heat transfer devices. Their simple, high maintaining, and cheap arrangement has made PHPs very efficient compared to conventional heat pipes. Rotating closed loop PHP (RCLPHP) is a novel kind of them, in which the thermodynamic principles of PHP are combined with rotation. In this paper, effect of rotational speed on thermal performance of a RCLPHP is investigated experimentally. The research was carried out by changing input power (from 25W to 100W, with 15W steps) and filling ratio (25%, 50%, and 75%) for different rotational speeds (from 50rpm to 800rpm with an increment of 125rpm). The results presented that at a fixed filling ratio, thermal resistance of RCLPHP decreased with increasing heat input applied to evaporator. Above a certain range of heat input, probability of partial dry-out of evaporator existed, which led into thermal performance deterioration of RCLPHP. Moreover, thermal resistance of RCLPHP decreased with increasing rotational speed and probability of partial dry-out in the evaporating section reached to its least amount. [Copyright &y& Elsevier]

This article presents a method for detecting rotational speed by LC (inductor-capacitor) wireless sensors. The sensing system consists of two identical LC resonant tanks. One is mounted on the rotating part and the other, as a readout circuit, is placed right above the rotating part. When the inductor on the rotating part is coaxially aligned with the readout inductor during rotation, the mutual coupling between them reaches the maximum, resulting in a peak amplitude induced at the readout LC tank. The period of the readout signal corresponds to the rotation speed. ADS (Advanced Design System) software was used to simulate and optimize the sensing system. A synchronous detection circuit was designed. The rotational speed of an electric was measured to validate this method experimentally, and the results indicated that the maximum error of the rotation speed from 16 rps to 41 rps was 0.279 rps. [ABSTRACT FROM AUTHOR]

The D2 wheel steel rolling wear experiment was carried out on a double-disc wear test machine. By observing the polygonisation wear of the sample surface, measuring the vibration frequency, and analyzing sample microstructure and properties, the effects of rotational speed on the polygonisation formation mechanism, microstructure and property evolution of a D2 wheel steel were studied within a certain speed range. The results indicated that polygonisation wear was the result of the coupling of vibration and wear. The dominant vibration frequency (f) was constant at the three rotational speeds studied, and was equal to the product of the rotational speed (ω) and polygonisation order (K), that is, f = 1 60 K ω. When the number of rolling cycles was the same, the sample surface became subject to more times vibration and impact as the rotational speed decreased. This increased the intensity of the wear, and the polygonisation wear began to occur faster. Conversely, the polygonisation wear caused the vibration and impact load to increase, and the coupling effect of wear and vibration increased, further aggravating the polygonisation wear. After polygonisation wear occurred, the degree of crest oxidation wear was reduced in relation to the decreasing rotational speed. The degree of trough fatigue wear was also aggravated, causing the polygonisation wear gap to become larger, while the mass wearing quantity increased significantly given the same number of rolling cycles. The thickness of the obvious plastic deformation layer, the microstructure refinement, and the change in hardness of the surface layer all increased with the intensification of polygonisation wear. • F is constant at a certain speed range, and is equal to the product of ω and K. • The polygonisation wear appears faster as the rotational speed decreases. • The crest oxidative wear increases gradually, trough fatigue wear decreases. • The polygonisation gap become larger and the mass wearing quantity increases. • Microstructure refinement and hardness change of the surface layer all increase. [ABSTRACT FROM AUTHOR]

Due to the rapid growth of research in the field of thermal energy storage (TSE), optimization of these systems (especially the method of latent heat thermal energy storage (LHTES)) is significantly investigated in last couple of years. Using fins is one of the conventional ways to increase the heat transfer rate. In the present study, a numerical simulation is conducted to assess the combined effects of applying both fins and rotation. This study investigates the solidification and melting process by using the enthalpy porosity method. Solidification and melting time and heat transfer rate are two essential parameters in the operating of LHTES heat exchangers. Results show that rotational speed has a positive effect on the operating system, with a reduction in time for the solidification process of 83.21% and the increased heat transfer rate of 12.89 W. Additionally, increased rotational speed has a direct relationship to the improvement of the heat transfer ratio by 2.45 and 3.87 times in the charging and discharging process, respectively. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effects of drilling rotational speed and feed-rate on the stability of dental implants through in-vivo and ex-vivo experiments. To this end, a total of 16 identical dental implants were inserted in the mandible of four dogs. The osteotomies were made with two drilling rotational speeds, i.e., 800 and 1500 rpm, and two different feed-rates, i.e., 1 and 2 mm/s. Implant stability quotients (ISQs) were recorded immediately after inserting implants and then each week for four subsequent weeks. Then, all animals were euthanized, and a bone sample containing the implants was extracted from each hemi-mandible for the pull-out test. A two-way ANOVA was performed for ISQs, and pull-out strengths (PoS), and the significance level was set to <0.05. The effect of rotational speed and feed-rate, used in this study, on the primary stability quotients was not significant (P > 0.05). Increasing the rotational speed from 800 to 1500 rpm significantly increased both ISQ and PoS values at the end of the 4th week after the implantation (P = 0.022 and P = 0.001, respectively). Moreover, by decreasing the feed-rate from 2 to 1 mm/s, a significant increase in PoSs of the dental implants was observed four weeks after the implantation (P = 0.019). Results of this study showed that either by increasing drilling rotational speed, here from 800 to 1500 rpm, or by reducing feed-rate, here from 2 to 1 mm/s, the secondary stability would be reinforced. Further investigations are needed to see if and how the conclusions made in this study can be generalized. [ABSTRACT FROM AUTHOR]