Process parameters of desiccation in colliding jets of a gaseous suspension

Results are shown of studies concerning the desiccation of sewage water sediments, which have been dehydrated mechanically, in apparatus with colliding jets of gaseous suspension. Heat transfer relations and technological parameters of this desiccation process are analyzed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 641–645, October, 1972.     

Influence of mixing procedure and mixer type on fresh and hardened properties of concrete: a review

Mixing concrete is not yet a fully understood issue, with many parameters having an influence on the resulting fresh and hardened concrete properties. Even for the same composition, a somewhat different microstructure can be obtained by changing the mixing procedure and the mixer type. A mixing procedure can differ in mixing time, mixing speed, air pressure in the mixing pan, addition time of the superplasticizer, temperature, etc. The concrete industry shows a great interest in controlling these influences in order to produce a concrete of which the mechanical, rheological and durability properties are well known. In this overview, different concrete mixers, mixing times, mixing speeds, different addition times of the superplasticizer and a different air pressure in the mixing pan will be examined. A review of existing literature is presented, as well as some new experimental results.     

Influence of geometrical parameters on the elastic response of unidirectional composite materials

A numerical approach to predict the elastic properties of composite materials departing from the properties of the individual constituents is presented. Using a recently proposed algorithm which generates a random distribution of fibres emulating the real distribution in the transverse cross-section of composite materials, an estimate of the elastic properties is obtained by performing volumetric homogenisation of the results from micromechanical analyses. The influence of different geometrical parameters used in the generation of the random distribution of fibres is analysed, namely, the dimensions of the representative volume element, the fibre radius, and the interval between neighbouring fibres.     

Evaluation of the mixing effectiveness of a new powder mixer

The effectiveness of the new powder mixer Canguro J tumbler was evaluated using lactose, microcrystalline cellulose, and salicylic acid as chemical indicator with the ratio 88:10:2 (w/w). The mixing time, the speed of the tumbler (rpm), its inclination, and filling percentage were varied in order to assess the limits of the mixer and the best parameters to use for obtaining a mixture as uniform as possible. The same experiments were then repeated after addition of 1% (w/w) magnesium stearate to the mixture of powders. The efficiency in the distribution of this lubricant was estimated by the progressive hardness reduction of the tablets derived from the compression of the powders, at a constant applied force. Finally, a comparison between Canguro J and a very efficient V-shaped mixer of the same capacity was performed. The results show that all investigated parameters influenced the mixing capability of Canguro J. The best effectiveness of the mixer occurred at the filling rate of 50% and a rotation speed of 20 rpm; in this case, Canguro J is even a little more effective than the V-shaped mixer. However, even at the filling rate of 70%, the same distribution uniformity of the powders can be obtained after a mixing time protraction of a few minutes.     

Calculation of the characteristics of a mixing CO2 gasdynamic laser with a nozzle unit of honeycomb construction

A mathematical model of a gasdynamic laser with parallel supersonic mixing of the components and its applications to the choice of the geometrical characteristics of the nozzle unit of honeycomb construction are presented.Notation T static temperature - u velocity - P pressure - molecular weight - e_i average number of vibrational quanta - k amplification ratio for a weak signal - I radiation intensity - _i molar fraction of the component in the mixture - ^* displacement thickness - r, d current radius and diameter of the nozzle - angle of inclination of the generating profile of the nozzle and characteristic temperature - h enthalpy - G flow rate - L characteristic length - A/A* expansion ratio of the nozzle - T_w wall temperature - ¯T_w=¯T_w/T_o temperature factor - =E _a /E_* nozzle efficiency - E stored vibrational energy - X=X/(r_a1 + r_a2) dimensionless coordinate Indices 1 radiating gas stream - 2 exciting gas stream - 0 stagnation value - a, *, values at the cut of the nozzle, in its critical cross section, and beyond the compression shock in the cross section of the nozzle cut Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 53–59, July, 1984.     

Influence of certain operating and geometrical parameters on the flow structure in an air vortex

The results of measuring the tangential and axial velocity components in a laboratory model of an atmospheric vortex are presented for different values of the geometrical parameters and degrees of swirling of the stream.     

Simulation of the turbulent mixing of a passive impurity in a jet mixer

Results of numerical simulation of the mixing of a turbulent jet with a cocurrent incompressible-fluid flow (Schmidt number Sc ≈ 1000) in a cylindrical channel of circular cross section (axisymmetric mixer) with the use of the standard k-ε turbulence model and different models for the averaged value of the mixture fraction and its variance have been given. For the problem of mixing of an inert passive impurity, two regimes of flow — the regime with the formation of a recirculation zone and that without its formation — have been considered. The formulated statistical model has been verified with the use of experimental data and results of calculation by large-eddy simulation. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 666–681, July–August, 2008.     

Turbulent mixing in a system of plane nonisothermal jets

An examination is made of turbulent flow in the main section in an infinite system of plane nonisothermal jets. The results of calculation are compared with experimental data.     

Analysis of the process of mixing of a passive impurity in a jet mixer

The experimental results for two regimes of mixing of a passive impurity in an axisymmetric jet mixer — the mixing of a turbulent jet and a cocurrent flow to form a recirculation zone behind the nozzle and an analogous mixing without the formation of a recirculation zone (Re_d = 10,000) — have been presented. The velocity field has been measured in the mixer cross sections at different distances from the nozzle (0.1 < x/D < 9.1) with a one-component Doppler laser anemometer, whereas the scalar field (concentration of the passive impurity) has been diagnosed by the laser-induced fluorescence method. Based on the scalar distributions obtained, the autocorrelation function and the integral scale have been computed, the form of the probability density function has been restored, and the distributions of the asymmetry and excess coefficients have been constructed. Visualization of flow in the mixer has been carried out. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 46–59, March–April, 2007.     

Numerical study of the mixing process of binary-density particles in a bladed mixer

Discrete element method (DEM) simulations of binary mixing of particles with different densities were conducted to study the influence of density ratio, blade speed, and filling level on the particle dynamics and mixing performance in a bladed mixer. Four particles with different densities at different locations were tagged to discuss the influence of three factors on the particle trajectory and velocity field in the mixer. A method based on cubic polynomial fitting of relative standard deviation was used to determine the critical revolution during the mixing process. It was found that the non-dimensional tangential velocity decreases with the increase of the blade speed and filling level, the fluctuation of vertical velocity increases with the radial location, blade speed, and filling level, and it is more pronounced than the fluctuation of tangential and radial velocity during the mixing process. Results obtained indicate that the mixing performance of particles with different density increases with the decrease of density ratio and filling level, while it increases with the increase of blade speed.     

Conditions for mixing transverse CO2 jets with a supersonic nitrogen stream in a nozzle

A flow visualization experiment has been performed in a planar supersonic nozzle with strong transverse jet blowing of CO₂. The authors have established the existence of two regimes for interaction of the jets with the main stream and with themselves. They have determined the dimensions of the zone where this interaction is strongest.     

DEM simulation for optimal design of powder mixing in a ribbon mixer

A ribbon mixer is often employed in powder mixing in a wide range of engineering fields. The structure of the ribbon mixer is extremely complicated. This structure makes it difficult to understand the mixing mechanism by experimental approaches due to problems related to accurate sampling. At present, the mixing mechanism in the ribbon mixer is empirically identified as convection, despite a lack of precise assessment. Additionally, experimental investigations to find the optimal design of the ribbon mixer have not been sufficiently conducted because of its prohibitive cost. As such, there is a lack of sufficient discussion concerning the design for better mixing in the ribbon mixer. Numerical technologies represent a promising approach for solving the aforementioned problems. Significant improvements in computer hardware have enabled numerical models such as the discrete element method (DEM) to be positively employed in powder mixing. In the current study, an identification approach is developed for convective mixing, and besides, the study explores an effective parameter for better mixing in the ribbon mixer using the DEM. A swept volume measurement approach due to paddle movement is newly developed to identify the main mixing mechanism as convection. Sensitivity analyses are performed to find an effective parameter for better mixing. Through the sensitive analyses, the blade width is indicated as an important factor for achieving better mixing. Moreover, this study shows that the relationship between the swept volume and mixing index remains, even if the paddle width changes. Thus, the swept volume measurement method is revealed as useful for identifying the mechanism as convection in the ribbon mixer. Thus, not only novel finding regarding the blade width for better mixing but also the development of an approach for identifying convective mixing in the ribbon mixer is presented herein. Incidentally, convection being the dominant mechanism is consistent with the novel finding regarding blade width achieving better mixing.     

The effect of mixing time and mixer intensity on the compression properties of tablettose®

The effect of mixer intensity on the compression properties of Tablettose® is considered. Changes are evidenced ranging from the negligible effects of a low intensity process such as roller mixing to a substantial physical alteration of the constituent particles when a high intensity process is used. It is suggested that in order to optimise the use of this component for direct compression formulation, a balance must be established between mixer efficiency and an acceptable level of particle damage.     

微肋管结构对管内冷凝换热影响的研究

相对于光管，微肋管的结构参数相对较多，这些结构参数的变化会不同程度地影响微肋管的换热能力，国内外的很多学者进行了研究，但结论相差较大，甚至完全相反。因此本文对这些研究成果进行一定的分析和回顾，希望能为铜管生产厂商以及空调设计工程师提供相关的参考，也为今后的研究工作提供一定的借鉴。     

CO2 mixing gasdynamic laser with emitting molecules formed in the reacting CO-O2-H2 mixture

The measured values of the gain in a supersonic stream of a gasdynamic laser with emitting CO₂ molecules formed in the reacting Co-O₂-H₂ mixture are reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 5, pp. 840–845, November, 1990.     

Evaluation of the possibility of mixing of turbulent jets with a comoving flow in a bounded space by interference methods

Experimental results showing the possibility of using interference methods for studying mass and heat-transfer processes in the combustion chambers of power generating installations with different configuration are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 2, pp. 181–185, August, 1987.