Increase In Rotational Speed Research Articles

Developing a rotation device in radio frequency systems for improving the heating uniformity in granular foods

A major obstacle for industrial radio frequency (RF) treatments is non-uniform and thermal runaway heating. This study aimed to improve the RF heating uniformity in granular products using a rotation device with sample mixing. After the run-out error of the rotation device met the allowable tolerance range, the RF heating uniformity was evaluated for mung bean, coix seed, peanut kernel and almond kernel under different rotating speeds, volume ratios and moisture contents (MCs). The results showed that the RF heating uniformity index decreased and then increased with increasing rotation speed, whereas the volume ratio presented the opposite effect. The RF heating uniformity index raised with increasing MCs. The heating uniformity in mung beans was the best because of their smallest particle size among the four selected samples. Therefore, the laboratory-scale rotation device applied in the RF system could provide a solid foundation for further large-scale industrial applications.

The investigation of wear on three-dimensional printed spur gears

Gears are commonly used in every field of industry as power and motion transmission elements. According to the usage areas, they are manufactured from materials such as steel, aluminium, plastics, cast and bronze. There are different manufacturing methods according to material type. Plastic gears are preferred in textile, automotive and aviation industries where the supported load is low, and corrosion and lightness are considerably important. They work more quietly than metal gears. Plastic gears are manufactured by an injection moulding or hobbing method. The disadvantages of the plastic injection method are high cost of the injection moulds and strength losses in the moulded parts due to the internal clearance faults, whereas the disadvantage of the hobbing method is defects in tooth profiles due to operational faults. In this study, wear strengths of plastic spur gears manufactured via a three-dimensional printer with the fused deposition modelling technique as an alternative manufacturing method were experimentally examined. In the experimental studies, polylactic acid pinion gear manufactured with the three-dimensional printer was subjected to wear tests with St37-2 gear. Wear strengths of plastic spur gears were compared in wear tests performed with Forschungsstelle für Zahnrader und Getriebebau equipment under various loads and rotational speeds. Wear depths that occurred in plastic gears were examined via coordinate measuring machine equipment. As a result of the experimental studies, it is found that wear is increased with the increase of load affecting the gear, and wear is decreased with the increase of rotational speed. As a result of this study, it was shown that plastic spur gears manufactured with three-dimensional printers can be used in areas where lightness and corrosion resistance is important under low loads.

Investigation and estimation on deagglomeration of nanoparticle clusters in teethed in-line high shear mixers

Experimental measurements and numerical studies with CFD method were performed to investigate the deagglomeration performance including the deagglomeration mechanism and the smallest attainable size of nano-clusters in in-line HSM under different operating conditions and structural parameters. The results indicate that the deagglomeration is dominated by rupture mechanism under lower energy input while controlled by erosion mechanism at higher energy input. Besides, the smallest size of nano-clusters is 131 nm, regardless of operating conditions and structural parameters of rotor–stator head. The deagglomeration performance can be effectively improved through increasing rotor speed, employing self-cycle mode and appropriately reducing residence time. In addition, the deagglomeration performance is also significantly impacted by the structural parameters involving rotor tooth number, shear gap and rotor teeth inclination. An ANN model is established to correlate the Sauter mean diameter d32 with the investigated parameters, and the comparison between estimated data and experimental data suggests that this method achieved an accurate prediction of d32 for the whole dispersion.

CFD Modeling of a Stirred Anaerobic Digestion Tank for Evaluating Energy Consumption through Mixing

The anaerobic digestion process is an effective means to eliminate the detrimental impacts of cattle manure discharge into the environment, i.e., biochemical contamination and substantial methane emissions, the latter leading to global warming. For proper operation of anaerobic digesters, an efficient mixing provides a relatively homogenous mixture of the feedstock within the tank. This study aims to investigate the mixing process and the total energy consumption needed for stirring by using an asymmetrical mixer. A further objective is to analyze the formation of stagnant volume and the velocity gradient in the digester in order to assure the mixing efficiency of the mixer type. The computational model is implemented as the finite volume method, and the rheological properties of the feedstock are considered. The results are validated by comparing the on-site power consumption of the mixer with the values obtained by the numerical torque. At various mixer speeds, the dead volume does not exceed 0.5% of the digester tank; however, with the increase of the mixer rotation speed, the energy consumption of the mixer increases drastically.

Gas dispersion in the oxygen delignification process

There has been very little knowledge about the state of gas dispersion in the oxygen delignification process, even though this has a major impact on the performance of the reactor. This paper presents a new continu-ous inline method for measuring oxygen bubble size distribution in the reactor, as well as results from studies con-ducted in softwood and hardwood lines. This new measurement worked well, and new information about oxygen bubble size, as well as how different reactor conditions affected the distribution, was obtained. For example: • In the softwood line, the mean volume-weighted bubble size was about 0.1 mm, whereas in the hardwood line, this size was almost 10 times higher. For both lines, there was considerable variation in the measured bubble size over the long term. • For both lines, an increase in mixer rotation speed caused a discernible decrease in the bubble size, and an increase in oxygen charge caused a discernible increase in the bubble size. • In the softwood line, no coalescence of the bubbles in the reactor was observed, but in the hardwood line, some coalescence of the larger bubbles occurred. • In the test conducted in the hardwood line, the use of brownstock washer defoamer caused a discernible increase in oxygen bubble size. • In the hardwood line, reactor pressure had a noticeable effect on the amount of delignification, which indicated that improving mass transfer of oxygen (e.g., by decreasing the oxygen bubble size, in this case) should also have an increasing effect on the delignification.

Dynamic Analysis of a Rotating FGM Beam with the Point Interpolation Method

The dynamic characteristics of a hub-functionally graded material beam undergoing large overall motions are studied. The deformation field of the flexible beam is described by using the assumed mode method (AMM), the finite element method (FEM) and the point interpolation method (PIM). Assuming that the physical parameters of functionally graded materials follow certain kind of power law gradient distribution and vary along the thickness direction. The longitudinal deformation and transversal deformation of the beam are both considered, and the nonlinear coupling term which is known as the longitudinal shortening caused by transversal deformation is also taken into account. The rigid-flexible coupling dynamics equations of the system described by three different discrete methods which have a uniform form are derived via employing Lagrange’s equations of the second kind. The validity of the point interpolation method established in this paper is verified by comparing with the numerical simulation results of the assumed mode method and the finite element method. On this basis, the influence of the functional gradient distribution rules on the dynamic characteristics of flexible beams undergoing large overall motions is discussed. The results show that the assumed mode method cannot deal with large deformation problem. Remaining other physical parameters of functionally graded materials beam unchanged, the maximum displacement of the beam increases with the increase of functionally graded materials index. The natural frequency of transverse bending of beam increases with the increase of rotational speed, when rotational speed is constant, the natural frequency will decrease with the increase of functional gradient index.

Numerical simulation on coal loading process of shearer drum based on discrete element method

The drum is the working mechanism of the coal shearer, and the coal loading performance of the drum is very important for the efficient and safe production of coal mine. In order to study the coal loading performance of the shearer drum, a discrete element model of coupling the drum and coal wall was established by combining the results of the coal property determination and the discrete element method. The movement of coal particles and the mass distribution in different areas were obtained, and the coal particle velocity and coal loading rate were analyzed under the conditions of different helix angles, rotation speeds, traction speeds and cutting depths. The results show that with the increase of helix angle, the coal loading first increases and then decreases; with the increase of cutting depth and traction speed, the coal loading rate decreases; the increase of rotation speed can improve the coal loading performance of drum to a certain extent. The research results show that the discrete element numerical simulation can accurately reflect the coal loading process of the shearer drum, which provides a more convenient, fast and low-cost method for the structural design of shearer drum and the improvement of coal loading performance.

Design and performance experiment of radial inflow turbine expander for organic Rankine cycle system

Abstract Expander is the core component of organic Rankine cycle (ORC) system. Taking R245fa as the organic working fluid, the miniaturization design of radial inflow turbine expander with theoretical maximum output power 20 kW and rotational speed of 30 000 r/min is carried out. The deflector and the moving impeller are simulated and designed. The ORC system with preheater and superheater is built for performance analysis of the designed turbine expander. The effects of temperature, pressure and rotational speed on the output power, temperature drop and efficiency of turbine expander are studied experimentally. The experimental results show that with the increase of the inlet temperature, the efficiency of the turbine expander has a minimum value, but the output power keeps increasing gradually. The analysis shows that the lowest efficiency is caused by the deterioration of expansion due to the rapid increase of flow rate. The turbine expander has the maximum efficiency of 0.886 at the inlet temperature 393.15 K and the inlet pressure 1.2 MPa. When the rotational speed increases from 12 000 r/min to 28 000 r/min, the temperature drop increases from 17.2 K to 32.7 K, and the output power increases from 7.04 kW to 17.3 kW. With the increase of rotational speed, the thermal power conversion capacity and temperature drop increase, so the output power increases. The system efficiency increases with the increase of turbine expander efficiency and has the same change rule.

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation.

The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.

First demonstration experiment of the neutron rotation method for detecting nuclear material

The rotation method is a novel method for detecting nuclear materials using a neutron source such as californium. In this method, while a neutron source is rotated rapidly nearby a measurement object, neutron measurement is carried out by synchronizing the rotation motion. If the object contains a nuclear material, as the rotation speed increases, the larger deformation of time distribution of neutron counts is observed, which in turn resulted to the detection of the nuclear material. In addition to its features of low cost and portability, this method is capable of detecting uranium that emits very few spontaneous fission neutrons. This study presents the fundamental principle of this method and its effectiveness for detecting nuclear materials through the experimental verifications.

Experimental evaluation of electrophoretic deposition-assisted polishing

The quest for precision in manufacturing sector is continuously evolving with the introduction of modern technologies and new techniques. In this research, the characteristics and influential parameters of a recently developed polishing process, known as electrophoretic deposition-assisted polishing (EPDAP), were investigated in external surface polishing of AISI 316 L stainless steel. The results revealed the improvement of surface roughness with increasing axial load up to the certain value of 11 N. The polishing time between 6 min and 12 min was recommended for polishing surfaces having a moderate initial roughness, close to 0.1 µm. Moreover, the increase of tool rotational speed led to the improvement of surface quality, while the variation of applied voltage had insignificant effects on the surface texture. In the second series of experiments, predictive equations of average surface roughness and material removal rate (MRR) were obtained based on analysis of variance. It was concluded that axial load and tool rotational speed are the most influential parameters on surface roughness and MRR, respectively. By performing a multi-response optimization, the optimum levels of control parameters at the same voltage of 15 V were calculated as axial load of 12 N, polishing time of 10 min, and tool rotational speed of 2000 rpm. This combination reduced the average surface roughness by 54.17% relative to the worst condition, which is characterized by the lowest axial loads, rotational speed, and polishing time at the design space. The maximum MRR of 3.975 mg/min was achieved at this optimum point. Assessment of the surface features indicated that the EPDAP process created uniform roughness profiles and resulted in an enhanced surface reflectance.

Analysis of Thermodynamic Parameter Variability in a Chamber of a Furnace for Thermo-Chemical Treatment

This paper presents results of research on unevenness of cylinder heating in a furnace for thermo-chemical treatment. Experimental research was conducted with respect to nitriding. Various heating speeds and settings of the fan operation in the furnace were considered. Boundary conditions were calculated in the form of temperature and the heat transfer coefficient (HTC) on the cylinder boundary in four planes along the cylinder length. Calculations were performed with the use of the inverse problem for non-linear and unsteady heat conduction equations. Boundary conditions from individual planes were compared with the mean value of them all. The variability of the calculated boundary conditions (temperature and HTC) along the cylinder length was investigated based on values of the absolute and relative differences for temperature and HTC. Estimates: mean value, mean value from the absolute value and the maximum values for the absolute and the relative differences of temperature and HTC were also calculated. Estimates were the measurements of the unevenness of cylinder heating in a furnace for thermo-chemical treatment. Based on the results of our research, it was found that an increase of the fan rotational speed from 50% to 100%, with the same heating speed, resulted in a significant leveling of temperature in the analyzed planes. The difference in temperature along the cylinder length was reduced from 6.8 °C to 3.3 °C. The increase of the heating speed from 5 °C/min to 10 °C/min resulted in an increase of the unevenness of the cylinder heating. Values of the absolute differences of temperature in the analyzed planes with reference to the mean temperature changed from an interval from −2.7 °C to 2.3 °C to a range from −4 °C to 5 °C. In processes with a heating speed greater than 5 °C/min, more intensive heating in the end part of the cylinder (close to the cylinder) was achieved than it was in other planes. It was proven by temperature values, which were higher, even, by 5.4 °C, and by HTC values, higher by 11.4 W/m2K, when compared with mean values. Obtained results can form the basis for nitriding process optimization.

Finite Element Simulation of Friction Stir Welding of Inconel 718 to Nimonic 80A

This paper presents results of simulation of friction stir dissimilar welding of 5 mm thick, Nickel-based super-alloys, Inconel 718, and Nimonic 80A using Abaqus software. Four different trials were done to understand the influence of tool rotation speed on temperature distribution in weld zone while travel speed remains constant. The temperature in the weld zone was found to increase with the increase in tool rotation speed and travel speed. The temperature on the advancing side of the tool was higher than that of the retreating side. The tensile strength of weldment was found, by simulation, to be 25% more than that of base metal, Inconel 718. This may be due to grain refinement and dynamic recrystallization during FSW. The simulated bend test revealed an adequate level of ductility of weldments.

Modern Biodegradable Plastics-Processing and Properties Part II.

Four different plastics were tested: potato starch based plastic (TPS-P)–BIOPLAST GF 106/02; corn starch based plastic (TPS-C)–BioComp BF 01HP; polylactic acid (polylactide) plastic (PLA)—BioComp BF 7210 and low density polyethylene, trade name Malen E FABS 23-D022; as a petrochemical reference sample. Using the blown film extrusion method and various screw rotational speeds, films were obtained and tested, as a result of which the following were determined: breaking stress, strain at break, static and dynamic friction coefficient of film in longitudinal and transverse direction, puncture resistance and strain at break, color, brightness and gloss of film, surface roughness, barrier properties and microstructure. The biodegradable plastics tested are characterized by comparable or even better mechanical strength than petrochemical polyethylene for the range of film blowing processing parameters used here. The effect of the screw rotational speed on the mechanical characteristics of the films obtained was also demonstrated. With the increase in the screw rotational speed, the decrease of barrier properties was also observed. No correlation between roughness and permeability of gases and water vapor was shown. It was indicated that biodegradable plastics might be competitive for conventional petrochemical materials used in film blowing niche applications where cost, recyclability, optical and water vapor barrier properties are not critical.

Thermal Characteristics Study of the Bump Foil Thrust Gas Bearing

In this paper, a thermo-hydrodynamic model of the bump foil thrust gas bearing is developed, which solves the coupled gas film three-dimensional energy equation, non-isothermal Reynolds equation, and the foil deformation equation. The effects of bearing speed, thrust load, and external cooling gas on the bearing temperature field are calculated and analyzed. The test rig of foil thrust gas bearing was built to measure the bearing temperature under different working conditions. Both simulation and experiment results show that there exist temperature gradients on the top foil both in the circumferential and radial directions. The simulation results also shows that the top foil side of the gas film has the highest temperature value in the entire lubrication field, and the position of highest temperature moves radially inward on the thrust plate side as the rotor speed increases. The gas film temperature increases with the increasing rotor speed and bearing static load, and rotor speed has greater effects on the temperature variation. Cooling air flow passing through the bump foil is also considered in the simulations, and the cooling efficiency decreases as the mass of gas flow increases.

Damping capacity of aluminium surface layers developed through friction stir processing

An attempt is made here to understand the role of tool rotational speed on the damping capacity of friction stir processed (FSP) commercial pure aluminium metal. The as-received metal plates were processed with a conical pin tool by keeping the tool traverse speed as constant and varying the rotational speed 600, 900 and 1200 rpm. Subsequently, samples extracted from the stir-zones were characterized for their microstructure, hardness, frequency-dependent and temperature-dependent damping capacities. The increase in rotational speed decreased the dislocation density and increased the average grain-size at the stir-zone, thus significantly influenced the damping capacity. The frequency-dependent damping capacity decreased with rotational speed owing to the reduction in dislocation density. High-temperature damping was significantly higher for the processed samples, but at the same time increase in rotational speed decreased the damping as there was an increase in grain size.

CFD-PBM and experimental investigation of a shear thinning fluid in a gas-liquid tank agitated by a helical ribbon impeller

• The hydrodynamics of an agitated gas-liquid reactor has been modelled using CFD-PBM method. • PIV measuring technique has been applied to verify simulation results. • The performance of a dual helical ribbon in non-Newtonian fluid with complex rheology has been investigated. • The influence of impeller speed on bubble size distribution, flow field, and viscosity of shear-thinning fluid have been studied. This study focuses on hydrodynamic characteristics of a shear thinning fluid agitated in a 3D multiphase reactor using a dual helical ribbon impeller. A combination of Computational Fluid Dynamics (CFD) simulation and Population Balance Model (PBM) were employed to study the gas-liquid interactions at various impeller speeds. The standard k - ε model and Eulerian multiphase approach were used to predict better quantities of turbulent flow parameters and its characteristics. Particle Image Velocimetry (PIV) was used to measure the velocity field for the model validation. Simulation results indicated that the bubble breakage and coalescence rate was intensified due to an increase in rotational speed. However, bubble breakage is still the dominant phenomenon since the bubbles would hit the walls and blads due to the turbulent intensity. Further, the helical ribbon impeller significantly reduces the viscosity of the fluid and improves the mixing efficiency that is confirming the authors’ previous experimental results. Furthermore, formation of static vortices adversely affects the efficiency of mixing process proving that an increase in impeller speed does not necessarily enhance the mixing perfiormance. Further, the helical ribbon impeller significantly reduced the viscosity of the fluid and enhanced mixing efficiency, thereby confirming the authors’ previous experimental results.

Joining of Advance Engineering Thermoplastic Using Novel Self-Heated FSW Tool

Friction stir welding (FSW) is an emerging technique for welding of thermoplastics. However, achieving proper welding of advanced engineering thermoplastics through the conventional FSW route is very challenging due to the necessity of high heat. Therefore, in the present study, a novel self-heated FSW tool was used to join advance engineering thermoplastic. Tool rotational speeds were varied at different levels keeping a constant tool traverse speed. The heat at the tool pin and material responses to tool for different rotational speeds were measured. Scanning electron microscopy revealed good weld surfaces with excellent material flow for welding with high tool rotational speed. A maximum ultimate tensile strength of about 29 MPa was achieved for a specimen welded at a tool rotational speed of 1450 rpm. Microhardness distribution of the welded specimens showed that the microhardness at the stir zone reduced with the increase of tool rotational speed due to reduction in crystallinity.

Evolution of microstructure, texture and mechanical properties of special friction stir welded T-joints for an α titanium alloy

T-joints of an α titanium alloy were successfully welded by friction stir welding, and the evolution of microstructure, texture and mechanical properties were investigated. Results show that dynamic recrystallization occurs in the stir zone, and the grain morphology depends on whether the welding temperature exceeds β transus. The microhardness of the welded joint shows a W-shaped profile, with the highest values in the stir zone and the lowest ones in the heat-affected zone. The joint tensile strength in the skin direction is significantly higher than that in the stringer direction. As the rotation speed or the welding speed increase, the tensile strength of the joint increases to a maximum, followed by a drop in both the skin and stringer directions. Similarly, the joint impact toughness increases first and then decreases with the increase of rotational speed or welding speed. The impact fracture of the typical joint with 850 rpm-50 mm/min is ductile dominated by dimples. In addition, the corrosion resistance of welded joint is improved compared to that of the base material.

Numerical investigation of the oil–air distribution inside ball bearings with under-race lubrication

Oil distribution inside the under-race lubricated bearing is crucial for lubrication and cooling of high-speed ball bearings. An under-race lubricated ball bearing is modeled to numerically investigate the effects of operating parameters and feed hole configuration on the distribution behavior of lubricant oil. The results of the numerical simulation indicate that the average oil volume fraction changes with a convex trend as the outer race rotating speed increases, while it changes monotonically with the inner race rotating speed, oil volume flow rate, and oil temperature. The extent of oil spreading on the outer race, cage, ball, and inner race decreases successively. Optimizing the feed hole configuration according to the average oil volume fraction is helpful to achieve precise lubrication of the under-race lubricated ball bearing.