scholarly journals Establishing the effect of a simultaneous reduction in the filling load inside a chamber and in the content of the crushed material on the energy intensity of self-oscillatory grinding in a tumbling mill

2021 ◽  
Vol 1 (1 (109)) ◽  
pp. 77-87
Author(s):  
Kateryna Deineka ◽  
Yuriy Naumenko
Keyword(s):  
Energy Intensity ◽  
Large Fraction ◽  
Fine Fraction ◽  
Sharp Decrease ◽  
Dynamic Effect ◽  
The Self ◽  
Cement Clinker ◽  
Solid Loading ◽  
Oscillatory Process ◽  
Crushed Material

The effect of a simultaneous change in the degree of filling a chamber with load κbr and in the content of the crushed material κmbgr on the efficiency of the self-oscillatory grinding process has been estimated. Using a method of numerical modeling based on the results of experimental visualization of the flow has helped establish an emergent dynamic effect of the sharp increase in the self-oscillatory action of two-faction loading at a joint reduction in κbr and κmbgr. A significant decrease in the passive quasi-solid loading motion zone has been detected, as well as an increase in the active pulsation zone and a growth of dilatancy. The manifestation of the effect is enhanced by the simultaneous interaction of increasing the scope of self-oscillations and weakening the coherent properties of particles in a loose large fraction under the influence of the particles of fine fraction. A significant decrease in the values of the inertial loading parameters has been established: maximum dilatancy υmax, the relative scale of self-oscillations ψRυ, the maximum share of the active part of κfammax, and the generalized complex degree of dynamic activation Ka. A 2.65-time growth of υmax was detected, ψRυ increased by 5 times, κfammax ‒ by 4.36 times, Ka ‒ by 18.4 times, at a joint decrease in κbr from 0.45 to 0.25, in κmbgr ‒ from 1 to 0. The synergistic technological effect of a sharp decrease in the specific energy intensity Еo/Еs has been established, as well as an increase in the relative performance Co/Cs in the self-oscillatory grinding, due to a significant increase in the dynamic action of loading, which is exacerbated by the joint interaction of reduced κbr and κmbgr. The process of the self-oscillatory grinding of cement clinker has been investigated. A 62 % reduction in Еo/Еs and a 125 % increase in Co/Cs were detected at a joint decrease in κbr from 0.45 to 0.25, in κmbgr ‒ from 1 to 0.125. The established effects make it possible to substantiate the parameters for the energy-efficient self-oscillatory process of grinding in tumbling mills with a conventional structure

scholarly journals ESTABLISHING THE ROTATION SPEED VARIATION RANGE LIMITS FOR AUTO-EXCITATION OF SELF-OSCILLATING GRINDING IN A TUMBLING MILL

2020 ◽  
Vol 4 ◽  
pp. 32-35
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko
Keyword(s):  
Visual Analysis ◽  
Rotation Speed ◽  
Relative Size ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
The Self ◽  
Cement Clinker ◽  
Crushed Material ◽  
Degree Of Filling ◽  
Tumbling Mill

The influence of the structure of a two-fraction polygranular feed of the chamber on the value of the drum rotation speed at auto-excitation of self-excited oscillations with a maximum swing is considered. Such a pulsating mode of movement of the charge is used in the self-oscillating process of grinding in a tumbling mill. The coarse fraction simulated the grinding bodies was steel bullets with a relative size ψdb=0.026. The fine fraction, simulated the particles of the crushed material, was a cement clinker with a relative particle size ψdm=0.00013. Variable factors of experimental studies were: the degree of filling the chamber in the state of rest κbr=0.25; 0.29; 0.33 and the degree of filling the gaps between the particles of the coarse fraction with particles of the fine fraction κmbgr=0.0625; 0.375; 0.6875; 1. The method of visual analysis of transient processes of self-oscillating modes of feed behavior in the cross section of the rotating drum chamber is applied. Measurements of the speed limits of the drum rotation were carried out with auto-excitation of self-oscillations of the filling. The magnitude of the self-oscillation swing was estimated by the increase in the difference between the maximum and minimum values of the filling dilatancy for one period of pulsations. An increase in the upper limit of the speed range ψω2 with a decrease in κbr and κmbgr was established. The growth rate of ψω2 increases at low values of κbr and κmbgr. Some increase in the lower limit of the ψω1 range with a decrease in κbr and κmbgr was revealed. An increase in the range of speeds of rotation was recorded at the maximum range of self-oscillations ψω1–ψω2 with a decrease in the connected interaction of the intra-mill filling. This coherent interaction is due to an increase in κbr and κmbgr. The value of the ψω1–ψω2 range varies from 1.01–1.03 at κbr=0.33 and κmbg=1 to 1.22–1.66 at κbr=0.25 and κmbgr=0.0625. The range gets its maximum value with fine and superfine grinding

scholarly journals INFLUENCE OF SMALL FRACTION OF POLYGRANULAR FILL OF ROTATING DRUM ON SELF-OSCILLATION SWING

2019 ◽  
pp. 31-37
Author(s):  
Deineka Kateryna
Keyword(s):  
Visual Analysis ◽  
Large Fraction ◽  
Relative Size ◽  
The Self ◽  
Spherical Particles ◽  
Rotating Drum ◽  
Crushed Material ◽  
Maximum Range ◽  
Size Of Particles ◽  
Degree Of Filling

The influence of the structure of two-fractional polygranular fill of a rotating drum on the self-oscillation swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of fill motion patterns in the cross section of a rotating chamber and measurement of dilatation was applied.Video of the fill pulsating flow was taken. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The maximum range of self-oscillation swing reached the value of 1.36. The change of the self-oscillation swing from zero at the beginning of self-excitation of pulsations to the maximum value with the greatest increase of dilatation was revealed. The effect of a decrease in the maximum range of self-oscillation swing with enhanced fill coherent properties has been registered. The attenuation of the spray of particles of large fraction in the chamber due to the coherent effect of the small fraction was established. An increase in the self-oscillation swing of single-grain fill was found with a decrease in the relative particle size and the chamber degree of filling. A decrease in the self-oscillation swing of two-fractional fill was found with an increase in the content of small fraction, a decrease in the relative size of particles of a large fraction, and an increase in the chamber degree of filling.

scholarly journals THE DRUM ROTATION VELOCITY VALUE WHEN AUTO-OSCILLATION SELF-EXCITATION WITH MAXIMUM SWING OF A POLYGRANULAR INTRACHAMBER FILL

2020 ◽  
pp. 61-69
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko ◽  
Anatolii Zmiievskyi
Keyword(s):  
Visual Analysis ◽  
Large Fraction ◽  
Relative Size ◽  
Experimental Studies ◽  
Rotation Velocity ◽  
The Self ◽  
Spherical Particles ◽  
Crushed Material ◽  
Fill Fraction ◽  
Degree Of Filling

The influences of the structure of two-fractional polygranular intrachamber fill on the drum rotation velocity value when auto-oscillation self-excitation with maximum swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of transient processes of self-oscillating fill flow modes in the cross section of a rotating chamber was applied. Measurements of the drum rotation velocity during fill self-excited self-oscillations were performed. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The magnitude of the relative drum rotation velocity at the maximum range of fill self-oscillation swing varied within 0.777-1.4. The effect of a decrease in the relative drum rotation velocity value, when the maximum polygranular intrachamber fill self-oscillations swing, with enhanced fill coherent properties has been registered. A decrease in the relative rotational velocity was established with a decrease in the relative particle size of large fill fraction and an increase in the content of small fill fraction and an increase in the chamber degree of filling. A sharp intensification of the decrease in the relative rotation velocity at a value of the relative size of large particles of less than 0.015 is revealed.

scholarly journals The influence of the fineness of metakaolin on the properties of self-compacting underwater concrete

2014 ◽  
Vol 13 (2) ◽  
pp. 093-098
Author(s):  
Stefania Grzeszczyk ◽  
Krystian Jurowski
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Fine Fraction ◽  
The Self ◽  
Concrete Mixture ◽  
Lower Content ◽  
Freeze Thaw ◽  
Underwater Concrete ◽  
Positive Effect ◽  
Scaling Resistance

The paper presents the research results of the influence of metakaolin of different fineness that is applied as a microfiller (20% of the cement mass) on the properties of self-compacting underwater concrete. It is demonstrated that the metakaolin with higher fineness improves the efficiency of antiwashout admixture and superplasticizer in concrete mixture. It was revealed that the higher resistance to washout of cement paste from the concrete mixture and higher flowability in comparison to the mixture containing metakaolin with lower content of fine fraction (below 10μm). In addition, the positive effect of the higher fineness of metakaolin on the compressive strength and freeze thaw scaling resistance was proven in the self-compacting underwater concrete.

scholarly journals Energy saving cement production by grain size optimisation of the raw meal

2009 ◽  
Vol 2 (2) ◽  
pp. 201-210
Author(s):  
B. Simons
Keyword(s):  
Grain Size ◽  
Energy Consumption ◽  
Lower Energy ◽  
Fine Fraction ◽  
Energy Resources ◽  
Cement Clinker ◽  
Cement Production ◽  
Grain Sizes ◽  
Natural Energy ◽  
Energy Consuming

The production of cement clinker is an energy consuming process. At about 50% of the energy is associated with grinding and milling of the raw meal, that normally is in the range 100% <200 μm with 90% <90 μm. Question: is it possible to use coarser components of the raw meal without reducing the clinker quality. With synthetic raw meals of various grain sizes the clinker formation was studied at static (1100 - 1450°C) and dynamic conditions (heating microscope). A routine to adjust the grain size of the components for industrial raw meals is developed. The fine fraction <90 μm should mainly contain the siliceous and argileous components, whereas the calcitic component can be milled separately to a grain size between 200-500 μm, resulting in lower energy consumption for milling. Considering the technical and economical realizability the relation fine/coarse should be roughly 1:1. The energy for milling can be reduced significantly, that in addition leads to the preservation of natural energy resources.

Effects of surface roughness on self-excited cavitating water jet intensity in the organ-pipe nozzle: Numerical simulations and experimental results

2019 ◽  
Vol 33 (27) ◽  
pp. 1950324
Author(s):  
Xiangdong Han ◽  
Yong Kang ◽  
Deng Li ◽  
Weiguo Zhao
Keyword(s):  
Numerical Simulation ◽  
Surface Roughness ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Energy Intensity ◽  
Volume Fraction ◽  
Water Jet ◽  
The Self ◽  
Simulation Results ◽  
Organ Pipe

This study was conducted to investigate effects of surface roughness on self-excited cavitating water jet intensity in an organ-pipe nozzle. Roughness average (Ra) values are 0.8, 1.6, 3.2, 6.3, 12.5, and 25 [Formula: see text]m, respectively. Numerical simulation results indicate that at inlet pressure of 10 MPa, the maximum, minimum, and real-time pressures in the self-excited oscillation chamber reach their respective peak values. The turbulent kinetic energy intensity in the external flow region is also most intense at this point, the vapor volume fraction in orifice is the highest, the vortex distribution scope in the orifice is the largest under [Formula: see text], and the self-excited cavitating water jet intensity is the strongest. The opposite variations emerge at [Formula: see text] compared to those of [Formula: see text], where the intensity is weakest. Pressure varies only slightly as Ra varies from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. Turbulent kinetic energy intensity behaves similarly as Ra increases from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m. At [Formula: see text], it was weaker than at Ra = 0.8–3.2 [Formula: see text]m. Similarly, there are only slight differences in vapor volume fraction and vortex distribution scope with Ra from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. The intensities at Ra = 0.8–3.2 [Formula: see text]m are similar, and weaker at Ra = 6.3 [Formula: see text]m. Pressure values are maximal at inlet pressure of 20 MPa, turbulent kinetic energy intensity is most intense, vapor volume fraction is highest, vortex distribution scope is largest under [Formula: see text] [Formula: see text]m, and intensity is strongest. Distinctions among pressure, turbulent kinetic energy intensity, vapor volume fraction, and vortex distribution scope values with Ra from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m are slight. Differences in the corresponding intensities are also slight; all decrease with Ra from 12.5 [Formula: see text]m to 25 [Formula: see text]m as the intensity gradually weakens. Numerical simulation results were validated by comparison against corresponding experimental phenomena.

scholarly journals Dynamic self-cleaning in gecko setae via digital hyperextension

2012 ◽  
Vol 9 (76) ◽  
pp. 2781-2790 ◽  
Author(s):  
Shihao Hu ◽  
Stephanie Lopez ◽  
Peter H. Niewiarowski ◽  
Zhenhai Xia
Keyword(s):  
Dynamic Model ◽  
Inertial Force ◽  
Dynamic Effect ◽  
Optimal Performance ◽  
The Self ◽  
Biomimetic Design ◽  
Dry Adhesives ◽  
Strong Adhesion ◽  
Self Cleaning ◽  
Gecko Feet

Gecko toe pads show strong adhesion on various surfaces yet remain remarkably clean around everyday contaminants. An understanding of how geckos clean their toe pads while being in motion is essential for the elucidation of animal behaviours as well as the design of biomimetic devices with optimal performance. Here, we test the self-cleaning of geckos during locomotion. We provide, to our knowledge, the first evidence that geckos clean their feet through a unique dynamic self-cleaning mechanism via digital hyperextension. When walking naturally with hyperextension, geckos shed dirt from their toes twice as fast as they would if walking without hyperextension, returning their feet to nearly 80 per cent of their original stickiness in only four steps. Our dynamic model predicts that when setae suddenly release from the attached substrate, they generate enough inertial force to dislodge dirt particles from the attached spatulae. The predicted cleaning force on dirt particles significantly increases when the dynamic effect is included. The extraordinary design of gecko toe pads perfectly combines dynamic self-cleaning with repeated attachment/detachment, making gecko feet sticky yet clean. This work thus provides a new mechanism to be considered for biomimetic design of highly reuseable and reliable dry adhesives and devices.

scholarly journals Investigation on the Self-synchronization of Dual Steady States for a Vibrating System with Four Unbalanced Rotors

2021 ◽  
Author(s):  
Zhao Chunyu ◽  
Mengchao Jiang ◽  
Chunyu Zhao ◽  
Yuanhao Wang ◽  
Weihai Duan
Keyword(s):  
Steady State ◽  
Design Method ◽  
Steady States ◽  
The Self ◽  
Parameter Determination ◽  
Parameter Method ◽  
Crushed Material ◽  
Rigid Frame ◽  
Coupling Equations ◽  
Cone Crusher

Abstract In the field of vibration utilization engineering, to achieve the maximum degree or the highest efficiency use of the excitation force is still a hotspot among researchers. Based on this, this paper has carried out a series of synchronous theoretical analysis on the four identical unbalanced rotors (IURs) symmetrically and circularly mounted on a rigid frame (RF) model, which is used to drive a cone crusher. The dimensionless coupling equations of the four IURs are established using the improved small parameter method. The analysis of the coupling dynamics characteristics of the system shows that the four motors of the system adjust the speed through the synchronous torque to achieve synchronization, and a parameter determination method for realizing offset self-synchronization to eccentric force was put forward under the steady state of ultra-resonance. Furthermore, the relationship between the equivalent stiffness of the crushed material and crushing force and compression coefficient is discussed, and the design method of the full-load crusher working under the steady state of sub-resonance is proposed. Finally, through a series of computer simulations, the correctness of the self-synchronization of dual steady states is verified.

scholarly journals Dispersion Change in Peat Mechanical Treatment

2018 ◽  
Vol 41 ◽  
pp. 01049 ◽  
Author(s):  
Vladimir Lebedev ◽  
Olga Puhova
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanical Treatment ◽  
Fine Fraction ◽  
Sharp Decrease ◽  
Coarse Fraction ◽  
Technological Parameters ◽  
Moisture Capacity ◽  
Processing Efficiency

The article discusses the research of peat physical and mechanical treatment which consists in determining technological parameters of peat stock. Size distribution and conditional specific surface area of peat particles are set. The relationship between processing efficiency and the content of peat fractions which size is less than 250 microns is derived. It proves to be linear. Treatment efficiency is found to be estimated by the data of a screen analysis alone and with satisfactory accuracy. Mechanical treatment has an effect on the values of total moisture capacity. The dependence is nonlinear and decreases insignificantly up to the conditional specific surface area of 350 m2/kg due to the partial grinding of fibrous coarse fractions. Mechanical treatment up to the conditional specific surface area of 500 m2/kg results in the sharp decrease of total moisture capacity due to the practically complete destruction of coarse fractions. With that of more than 500 m2/kg the values of total moisture capacity change insignificantly. Multiple peat treatment causes its mechanical consolidation and the reduction of coarse fraction content along with significant increase of fine fraction content.

scholarly journals MECHANISMS OF TRANSMISSION OF THE SPIN-SPIN INTERACTION OF CARBON-CARBON IN A SERIES OF BICYCLOBUTANE DERIVATIVES

2021 ◽  
Vol 2021 (1) ◽  
pp. 77-87
Author(s):  
Elena Chirkina ◽  
Leonid Krivdin
Keyword(s):  
Sharp Decrease ◽  
The Self ◽  
Substitution Effects ◽  
Spin Interaction ◽  
Unsaturated Alcohol ◽  
Consistent Theory ◽  
Good Correspondence ◽  
Self Consistent ◽  
Experimental Values ◽  
Hybrid Orbitals

Within the framework of the self-consistent theory of finite perturbations SCPT INDO, the calculation of the spin-spin interaction constants 13C-13C with preliminary optimization of geometric parameters in 17 bicyclo derivatives is carried out[1.1.0.] of Bhutan. There is a good correspondence of the calculated constants with the experimental values known in the literature and measured in this work. Based on the results of the calculations performed, the study of hybridization effects in the considered series of compounds was carried out. All bicyclobutane derivatives are characterized by an abnormally low s-character of endocyclic hybrid orbitals forming a bond between bridging carbon atoms. Substitution effects have a weak effect on the s-order of the bridge connection. The presence of an unsaturated alcohol structure in the 2-position of the bicyclo-butane fragment leads to a sharp decrease in the s-character of the endocyclic hybrid orbitals of the bridged carbon atoms.

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