Particle Rotational Speed Research Articles

Dynamics of rapidly rotating Bose–Einstein quantum droplets

This study presents a detailed analysis of the stationary properties and dynamics of an anharmonically trapped, rapidly rotating Bose–Einstein liquid droplet. We investigate the effects of the particle number, confining potential, and rotation speed on the formation of the energetically favored bead, multiple quantized vortex, off-center vortex, and center-of-mass states. The multi-periodic trajectories and breathing provide evidence of the collective excitations of the surface mode in the vortex states. Observation of the self-trapping phenomenon and tendency toward the lowest Landau level in rapid rotation regimes coincides well with the quantum-Hall limit. Modifying the topological charges and destroying the potential flow of the vortex state can occur if an external disturbance is imposed upon the quantum droplet.

DEM study on mixing behaviors of concave-shaped particles in rotating drum based on level-set method

Granular mixing is a complex phenomenon that is commonly encountered in various engineering disciplines. A large number of past studies have mainly focused on the mixing properties of convex-shaped granular materials, while the mixing behaviors of concave-shaped granular materials have not been well studied. In this study, spherical harmonic functions are used to describe the spherical and concave shapes of individual particles. The level set function is an implicit function consisting of a set of points that can be used to determine the contact points between particles. Then, the influences of the particle shape and rotational speed on the mixing behaviors of the granular material within a horizontal drum are analyzed by the discrete element method (DEM). Results indicate that concave particles have higher coordination numbers and closer contact patterns than spherical particles, which results in greater normal collision forces, larger dynamic angle of repose and lower mixability.

Scale-up of heat transfer in a rotary drum equipped with baffles

In this study, discrete element method (DEM) simulations were performed to investigate how baffles regulate heat transfer in a rotary drum. In order to scale up the system, we established an empirical relationship based on a new characteristic time for baffles that predicts the average particle bed temperature. Particle fill level, drum size, baffle size, baffle number, and rotation speed were adjusted to alter the operating conditions of the rotary drum. Thermal conductivity and particle size were also examined as influences on material properties. It was found that increasing the number and size of baffles significantly improved the rate of heat transfer but had no significant effect on particle temperature distribution and bed uniformity. Baffle effectiveness was found to be correlated with the fill level and rotational speed such that higher rotation speed generally increases temperature uniformity without significantly increasing the rate of heat transfer.

Experimental and modeling studies on dynamic barite sag and effects of particle size, shear rate, and fluid rheology

Barite is often utilized to control the weight of drilling muds. However, in inclined wellbores, barite particles settle out of the mud in a lateral direction and quickly reach the wellbore wall. Over time, deposited particles form unstable barite beds that slide intermittently downward, causing downhole pressure fluctuations. The observation is often referred to as barite sag, which occurs prominently when the system is in a dynamic state. Barite sag leads to density variation in the mud system, resulting in drilling issues such as stuck pipe, fluid loss and lost circulation, loss of well control, and wellbore instability. Various experimental studies have been conducted on barite sag, but limited mathematical modeling has been undertaken.This article presents the results of experimental and mathematical modeling studies on barite sag. First, particle size distribution tests were performed with API barite. Then, different oil-based muds (OBMs) were prepared using barite samples with various particle size distributions. Next, the apparent viscosities of the muds were measured with a rheometer. Then, the Viscometer Sag Shoe Test (VSST) method was used to study barite sag at 49 °C varying rotational speed and barite particle size distribution. Furthermore, the settling behavior of barite particles under dynamic conditions was simulated using a sedimentation-consolidation model. The model is solved numerically by applying a fully implicit finite difference method. The accuracy of the numerical solution is validated using simulation results presented in a previous study. The model has been improved to handle non-Newtonian fluids and simulate dynamic conditions.According to the apparent viscosity measurements, barite particle size has a minor effect on OBM rheology. The VSST results also show that barite sag increases with particle size and rotational speed. The improved model predicts VSST results fairly well. Additionally, a model-based parametric study indicates that barite sag decreases with increasing OBM rheological parameters (consistency index, yield stress, and fluid behavior index).

Online monitoring of dry powder mixing in a bin mixer

Dry powder mixing is a common process in the food industry. The aim of dry powder mixing is to improve the mixture quality within the optimum critical mixing time. Therefore, critical mixing time and mixture quality need to be monitored and quantified. An optical camera has advantages of high resolution, short image acquisition time and relatively large sampling area. An optical camera was used to online monitor the mixing process of the dairy-based powder and coffee powder of different sizes in a 5-L bin mixer. A new image analysis method including seven mixing indices and three dispersion indicators, has been developed. This method can provide precise results and identify different effects on mixing performance. This study confirms that the best mixing quality can be achieved when mixing particles of similar size. When the rotation speed is increased from 5 to 15 and 30 rpm, the critical mixing time is shortened. • Online monitoring of food powder mixing in a bin mixer by using optical technique. • A new method to quantify critical mixing time and mixture quality. • Both overall and local mixing change are crucial. • Seven mixing indices provide a comprehensive assessment of the mixing process. • Particle size and rotation speed significantly influence the mixing performance.

Composition Optimisation of Selected Waste Polymer-Modified Bitumen.

Waste plastomer disposal is currently a major challenge facing modern economies. This article reports on a study and analysis regarding the implementation of plastomers into bitumen, with a special focus on the influence of mixing process factors. Two plastomers were selected for analysis, PP and PET, and two bitumen types, 20/30 and 70/100, were modified. Determination of the basic characteristics, such as penetration, softening temperature, cohesion energy, and Fraass temperature, was complemented with advanced multiple-stress creep recovery (MSCR) rheological testing. The entire experimental process followed the Plackett-Burman design. Rheological effects of modified bitumen were evaluated using the generalized Maxwell model. Microstructural analysis with epi-fluorescence microscopy showed the ability of plastomer-modified bitumen to obtain a fine-grained structure with a particle size of <10 μm. In addition, creep susceptibility (Jnr) was found to be statistically significantly dependent on the polymer type and particle size, rotational speed, and bitumen type. In turn, the particle dispersion structure in the bitumen matrix significantly depended on the rotational speed, plastomer particle size, and mixing temperature. Ultimately, the process of bitumen 70/100 modification was optimized. It was demonstrated, following the experimental design, that by using fine-grained PP for a temperature of 160 °C, rotational speed of about 6300 rpm and time of 105 min, it is possible to obtain modified bitumen with rheological properties very similar to those of modified bitumen PmB 45/80-55.

DEM investigation of particle flow in a vertical rice mill: Influence of particle shape and rotation speed

The obscure milling mechanism, causing by diversity of rice grain shape, restricts appropriate selection of processing conditions for improving milling quality of different varieties. On this basis, the rice grain was represented as an axi-symmetric ellipsoid using discrete element method (DEM). Effects of particle shape and roller shaft rotation speed as well as the interplay of both on axial dispersion, radial exchange, spatial orientation and collision characteristics relating to the milling mechanism were analyzed. The results indicated that effects of aspect ratio on the milling uniformity depend on rotation speed, displaying the axial dispersion coefficient and mean effective collision rate increase with increasing aspect ratio in the lower rotation speed, whereas completely opposite in the higher rotation speed. Effects of aspect ratio on the milling intensity are independent of the rotation speed, showing radial ectopia number, variance of orientation distribution and mean collision energy all increase with increasing aspect ratio.

Alkali Depolymerization of Poly(ethylene terephthalate) in a Quasi‐solid‐solid Kneading Reaction

AbstractThe alkaline depolymerization reaction of poly(ethylene terephthalate) (PET) under quasi‐solvent‐free conditions was investigated. This is a new approach for recycling PET waste to its monomer building blocks: terephthalic acid and ethylene glycol. The influence of base particle size, reaction temperature, and rotational speed of the employed laboratory kneader on terephthalic acid yield in the quasi‐solid‐solid reaction was investigated. PET is depolymerized almost quantitatively in a reaction time of 5 min at moderate reaction temperatures, with intense mixing affecting the yield of terephthalic acid. The quality of the terephthalic acid monomer, assessed by color index measurements, indicated that the reaction temperature primarily influences the color index of the monomer. By balancing terephthalic acid yield versus color index, optimum reaction conditions were proposed.

Nonlinear accelerated orbiting motions of optical trapped particles through two-photon absorption.

Vortex beams carrying optical angular momentum (AM) could drive the orbital motion of a small particle around the optical axis. In general, the orbital rotation speed of trapped particles increases linearly with the increasing laser power. Beyond the linear optics regime, in this work, we investigate both the optical force and torque on a two-photon absorbing Rayleigh particle produced by the tightly focused femtosecond-pulsed circularly polarized vortex beam. Different from the trapping dynamics of particles without two-photon absorption (TPA), it is shown that the orbital motion of trapped particles with TPA accelerates nonlinearly as the laser power increases. Moreover, the orbital motion acceleration of trapped particles is proportional to the TPA coefficient. The corresponding underlying mechanism is discussed in detail. Our results may find interesting applications in the characterization of the optical nonlinearity of a single nanoparticle, and AM manipulation and particle transportation in the nonlinear optics regime.

Wall to particle bed contact conduction heat transfer in a rotary drum using DEM

Contact conduction heat transfer behavior in a rotary drum using the discrete element method (DEM)-based simulation codes MFIX-DEM (open-source) and EDEM (commercial) is investigated. Simulations are performed to compare the performance of open-source and commercial code models with experimental data. This study also aims to investigate the effects of particle size distribution (PSD), rotation speed, and rolling friction on overall wall–bed heat transfer using the validated codes. It is found that the variability in the PSD with same mean, μ, and standard deviation, σ, resulted in different heat transfer coefficients. Monodispersed particle beds exhibit better heat transfer when compared to polydispersed beds, because heat transfer is inhibited as the distribution broadens due to segregation. Rotation speed has minimal impact on conduction heat transfer. At lower values of rolling friction, particle circulation in the bed is enhanced and therefore better heat transfer is achieved.

Qualitative and quantitative analysis of Rhodobryum giganteum by using nonlinear oscillating chemical fingerprint technique

A new method for qualitative and quantitative analysis of Rhodobryum giganteum by using the nonlinear oscillating chemical was established for improving the quality control standard of R. giganteum. Its potential(E)/time(t) curve was recorded by electrochemical workstation in the oscillation reaction system of BrO~-_3-Ce(SO_4)_2-H_2SO_4-malonic acid/tartaric acid. The nonlinear oscillating chemical fingerprints were investigated for repeatability, and it was found that the RSD values of the four characteristic parameters of R. giganteum were less than 4.1%, indicating a good repeatability and high precision of this experiment. After optimizing the experimental parameters such as particle size, rotation speed and temperature, a new method based on nonlinear oscillating chemical was used for qualitative and quantitative analysis of R. giganteum. The results showed that there was a good linear relationship between the induction time/the period of oscillation and the dosage of herbs(0.1-1.1 g), with the relative coefficients of 0.978 and 0.975, respectively. Besides, the highest potential showed a nonlinear relationship with the dosage of herbs, with the relative coefficient of 0.999. This method was also used to discriminate the R. giganteum and R. roseum. They were similar in appearance, but their fingerprints were quite different. Independent sample t test results showed that there were significant differences in the oscillation time, the maximum amplitude and the induction time, providing a basis for the identification of the basic sources of Herba Rhodobryi Rasei.

Annular Surface Micromachining of Titanium Tubes Using a Magnetorheological Polishing Technique.

In this study, a novel magnetorheological (MR) polishing device under a compound magnetic field is designed to achieve microlevel polishing of the titanium tubes. The polishing process is realized by combining the rotation motion of the tube and the reciprocating linear motion of the polishing head. Two types of excitation equipment for generating an appropriate compound magnetic field are outlined. A series of experiments are conducted to systematically investigate the effect of compound magnetic field strength, rotation speed, and type and concentration of abrasive particles on the polishing performance delivered by the designed device. The experiments were carried out through controlling variables. Before and after the experiment, the surface roughness in the polished area of the workpiece is measured, and the influence of the independent variable on the polishing effect is judged by a changing rule of surface roughness so as to obtain a better parameter about compound magnetic field strength, concentration of abrasive particles, etc. It is shown from experimental results that diamond abrasive particles are appropriate for fine finishing the internal surface of the titanium-alloy tube. It is also identified that the polishing performance is excellent at high magnetic field strength, fast rotation speed, and high abrasive-particle concentration.

Liquid-solid mass transfer in a rotating trickle-bed reactor: Mathematical modeling and experimental verification

Liquid-solid mass transfer model is significant but deficient for the design of a rotating trickle-bed reactor (RTBR), which has great potential for process intensification of heterogeneous catalytic reactions. In this work, a mathematical model considering the wetting efficiency was first established to describe the liquid-solid mass transfer process in the RTBR. External static liquid holdup was referred to give a reasonable initial value for calculation. The profile of concentration boundary layer was obtained by mass balance analysis of an Eulerian element on a single sphere. The above model was then extended to predict the liquid-solid mass transfer coefficient (kLS) in the RTBR. A copper dissolution method was employed to measure the kLS, considering the effects of particle diameter, rotational speed, and liquid superficial mass velocity. The comprehensive comparison between predicted and experimental values of kLS was conducted and deviations were within ±25%.

A Review of Tunable Orbital Angular Momentum Modes in Fiber: Principle and Generation

Orbital angular momentum (OAM) beams, a new fundamental degree of freedom, have excited a great diversity of interest due to a variety of emerging applications. The scalability of OAM has always been a topic of discussion because it plays an important role in many applications, such as expanding to large capacity and adjusting the trapped particle rotation speed. Thus, the generation of arbitrary tunable OAM mode has been paid increasing attention. In this paper, the basic concepts of classical OAM modes are introduced firstly. Then, the tunable OAM modes are categorized into three types according to the orbital angular momentums and polarization states of mode carrying. In order to understand the OAM evolution of a mode intuitively, three kinds of Poincaré spheres (PSs) are introduced to represent the three kinds of tunable OAM modes. Numerous methods generating tunable OAM modes can be roughly divided into two types: spatial and fiber-based generation methods. The principles of fiber-based generation methods are interpreted by introducing two mode bases (linearly-polarized modes and vector modes) of the fiber. Finally, the strengths and weaknesses of each generation method are pointed out and the key challenges for tunable OAM modes are discussed.

Numerical investigation of the back-mixing and non-uniform characteristics in the three-dimensional full-loop circulating fluidized bed combustor with six parallel cyclones

The design and operation of circulating fluidized bed (CFB), which offers excellent heat and mass transfer, remain challenging because of the lack of a comprehensive understanding. CFD-DEM is used here for the high-fidelity simulation of the three-dimensional full-loop CFB with six parallel cyclones. Detailed information on the particle-scale information (i.e., solid dispersion, particle rotational speed, fluid and collision forces, mass distribution, and backing-mixing intensity) throughout the CFB are presented for the first time. Interesting results include: (i) the solid dispersion behavior is significantly different among the three directions; (ii) the solid loading in the middle cyclone on one side of the riser is twice that of the two adjacent ones, and this non-uniform distribution underscores the need for full-loop simulation for the CFB with multiple cyclones; (iii) the solid dispersion coefficients in all three directions, fluid force, collision force and particle rotational speed are similar among the six cyclones and correspondingly the standpipes; and (iv) approximately 50% and 48% of the total material are distributed respectively in the riser and standpipes. The results obtained provide valuable insights regarding the mass loading, particle-scale characteristics and non-uniform distribution of the solid phase throughout the entire CFB.

Numerical Simulation and Experimental Study of Cuttings Transport in Narrow Annulus

With the development of petroleum industry, it needs an efficient drill method such as under balanced drilling (UBD) to enhance the rate of penetration (ROP). However, borehole instability is a problem that UBD must face. The coiled tubing partial underbalanced drilling (CT-PUBD) is proposed to try to solve this problem while keeping an underbalanced condition with high ROP. This paper analyzes the laws of cuttings transport in the narrow annulus focus on this new technique through the simulations and experiments. From the results of simulations, it obtains that the particle velocity declines with the increase of rotational speed and increases with the increase of flow rate. The particles become concentrated as the flow rate increases, and the high flow rate limits particles in a small area. The particle distribution undergoes a process of concentration, dispersion, and concentration as the rotational speed increases. The high rotational speed makes particles deviate from the high fluid velocity area, which causes low particle velocity. The relationships between particle velocity and rotational speed and between particle velocity and flow rate are fitted through the equations, respectively. The phenomenon of collision of particles, sinking and rising of particles, and variation of particle velocity are observed in the experiments. The error between the particle velocity in the experiment and numerical simulation is less than 8.5%. This paper is an exploratory study conducted for the cuttings transport in narrow annulus.

Mechanism and Parameter Optimization in Grinding and Polishing of M300 Steel by an Elastic Abrasive.

In order to achieve high quality polishing of a M300 mold steel curved surface, an elastic abrasive is introduced in this paper and its polishing parameters are optimized so that the mirror roughness can be achieved. Based on the Preston equation and Hertz Contact Theory, the theoretical material removal rate (MRR) equation for surface polishing of elastic abrasives is obtained. The effects of process parameters on MRR are analyzed and the polishing parameters to be optimized are as follows: particle size (S), rotational speed (Wt), cutting depth (Ap) and feed speed (Vf). The Taguchi method is applied to design the orthogonal experiment with four factors and three levels. The influence degree of various factors on the roughness of the polished surface and the combination of parameters to be optimized were obtained by the signal-to-noise ratio method. The particle swarm optimization algorithm optimized with the back propagation (BP) neural network algorithm (PSO-BP) is used to optimize the polishing parameters. The results show that the rotational speed has the greatest influence on the roughness, the influence degree of abrasive particle size is greater than that of feed speed, and cutting depth has the least influence. The optimum parameters are as follows: particle size (S) = #1200, rotational speed (Wt) = 4500 rpm, cutting depth (Ap) = 0.25 mm and feed speed (Vf) = 0.8 mm/min. The roughness of the surface polishing with optimum parameters is reduced to 0.021 μm.

Slurry erosion behavior of plasma sprayed coating on turbine steel

PurposeThe purpose of this paper is to study the effect of slurry erosion at different parameters on plasma sprayed Cr3C2 coated 13Cr4Ni turbine steel and compare the results of coated steel with bare steel.Design/methodology/approachCr3C2 + 25NiCr coating was successfully developed on 13Cr4Ni turbine steel using plasma spraying method. The slurry erosion test was performed using a simulated erosion testing rig. The commercially available silica sand was used as abrasive media and the effect of concentration (ppm), average particle sizes and rotational speed on the slurry erosion behavior were studied at 300 and 900 impact angles. Developed coatings were characterized by scanning electron microscope, XRD, EDS and micro hardness tests and study of erosion wear.FindingsResults revealed that three times higher hardness of coatings was obtained because of the hard phases of chromium carbide and nickel carbide, which restricted the abrasive wear in comparison to uncoated steel. Lower abrasive wear was observed at 900 impact angle coupled with lower levels of slurry concentration and rotational speed. Further, it was observed that initially cumulative mass loss rate was high which gets stabilized after the surface become smooth and on exposing for higher periods. Overall results indicated that erosive wear was reduced significantly by the application of developed coating.Originality/valueThe developed plasma sprayed coating is very useful to enhance the service life of turbine steel by lowering the effect of slurry erosion.

Experimental investigation on size degradation of bridging material in drilling fluids

Solid particle size distribution (PSD) of drilling fluids is one of the key factors for the formation damage and lost circulation control. However, particle size degradation occurs during the long-term process of drilling fluid circulation in the wellbore, consequently resulting in severe formation damage. In this study, size degradation experiments of calcium carbonate solids in the period of drilling fluid circulation are conducted to understand the effect of initial particle size, rotation speed, shear time, fluid viscosity, temperature, pH, salinity, and solid concentration on size degradation of bridging material (BM). The size degradation rate of D90 is taken as the characterization of particle size degradation. The results show that ① the degree of size degradation sharply increases with increasing solid initial size, rotation speed, and shear time. Under the experimental conditions, size degradation rate of sample with D90 = 44.153 μm is up to 30%~40% at a rotation speed of 1000 rpm over 30 min; ② there is a critical particle size in the range 15–20 μm for size degradation over 90 min. When the particle size drops to this critical size, no size degradation occurs obviously; ③ size degradation decreases with increasing fluid viscosity; ④ fluid temperature, pH, salinity, and solid concentration have little effect on size degradation. The evaluation criterion of size degradation is established, and an empirical model is developed to calculate the size degradation. Two mechanisms of the formation damage induced by size degradation are revealed. Based on the particle size degradation, the strategy for the optimization of PSD and solid supplement is presented. We believe that this strategy will be of great significance to designing the particle size distribution of BM for drilling fluids in the field.

Taguchi approach to erosion wear optimization of WC-10Co-4Cr sprayed austenitic steel subjected to equisized slurry

PurposeThis paper aims to optimize the erosion wear analysis of slurry impeller material. Stainless steel (SS-410) was used as the pump impeller material. This erosion test was established to influence the rotational speed, solid concentration, time period and particle size. Fly ash was used as the erodent material.Design/methodology/approachThe erosion wear experiments were performed at different particle size, rotational speed, time duration and solid concentration (by weight). These tests were performed at four different speeds of 750, 1,000, 1,250 and 1,500 rpm, and the time durations of these experiments are 75, 120,165 and 210 min. For protective coating, high-velocity oxygen-fuel spray process was used for depositing WC-10Co-4Cr coating on stainless steel. To investigate the influence of controlled process parameters on slurry erosion wear of pump impeller material, Taguchi method was used.FindingsResults show that significant improvement in erosion wear resistance has been observed by using WC-10Co-4Cr coating. The process parameters affecting the erosion wear loss were in following order: time > rpm > concentration > particle size. The means of signal-to-noise ratio of stainless steel SS410 with and without coating vary from 93.56 to 54.02 and from 86.02 to 48.18, respectively.Originality/valueFor the erosion wear rate of both uncoated and coated stainless steel, the most powerful influencing factor was identified as time. The erosion test reveals that the coating exhibits ductile erosion mechanism and shows better erosion wear resistance (approximately two times) compared to uncoated stainless steel.