Effect of the PLAZMAZER plasma ignition system on the fuel combustion regimes in combustion chambers of engines

An economically efficient method of combatting toxic products of incomplete fuel combustion in engines and other movable and stationary power installations by means of pulsed automatic control of the ignition and combustion processes carried out by the PLAZMAZER system is proposed. A new concept of the occurrence of motor knock in internal combustion engines with external carburetion, the stiff operating mode of diesel engines, erosion of turbine blades, burn-out of combustion-chamber and exhaust-line elements, and jet engine compression stalling are presented.     

A 3D fourth order fabric tensor approach of anisotropy in granular media

We propose a micromechanical approach for granular media, with a particular account of the texture-induced anisotropy and of the strain localization rule. The approach is mainly based on the consideration of a fourth order fabric tensor able to capture general anisotropy which can be induced by complex distribution of contacts. Incorporation of this fourth order fabric tensor in a suitable homogenization scheme allows to determine the corresponding macroscopic elastic properties of the granular material. For this purpose, in addition to the classical Voigt upper bound, a new kinematics-based localization rule is proposed. It generalizes the one formulated by Cambou et al. [B. Cambou, Ph. Dubujet, F. Emeriault, F. Sidoroff, Eur. J. Mech. A/Solids 14 (1995) 225–276] in the case of an isotropic contact distribution. The results of the complete model compare well to numerical simulations results when available [C.S. Chang, C.L. Liao, Appl. Mech. Rev. 47 (1 Part 2) (1994) 197–207] (case of isotropic distribution of contacts). Finally, the interest of the fourth order fabric tensor based approach combined with the proposed localization rule is shown for different distributions of contacts by comparing its predictions to those given by a second order fabric tensor approach.     

Experimental characterization of the chaotic dynamics of cohesionless particles: application to a V-blender

So far, most of the investigations of the dynamics of granular material in blenders have been done in 2D tumblers due to the current lack of accurate measurement methods for the investigation of complex 3D flows. However, recent advances in the field of non-intrusive methods have paved the way to the characterization of the chaotic dynamics in 3D blenders. This work aims to present such an analysis in the case of a V-blender using radioactive particle tracking (RPT). Special attention is given to the chaotic properties of mixing by performing a time-series analysis of the position of a single tracer in motion in this blender. An original investigation of the mixing properties is also presented. More generally, this work shows that the mixing properties of a blender can be characterized by using tools of dynamical systems theory through a time-series analysis of data obtained from non-intrusive measurements.     

Problem of determining the effective temperature in combustion chambers of heat and power installations

The effect of the dimensions of the constant temperature core in a radiating planar, nonisothermal, nonscattering layer on the magnitude of the effective temperature is examined. Computed effective temperatures of such a layer, obtained with the use of various methods, are also compared.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 1, pp. 109–114, January, 1981.     

Random walk approach to wave radiation in cylindrical and spherical domains

Two- and three-dimensional Helmholtz equations in the exterior cylindrical and spherical domains are addressed by the random walk method. The solutions of the Dirichlet problems in such domains are represented as mathematical expectations of specified functionals on trajectories of random motions running in designated domains of a multi-dimensional complex space. The numerical examples confirm the efficiency of the random walk approach to the analysis of wave radiation.     

Simulation of the packing of granular mixtures of non-convex particles and voids characterization

The simulation of granular materials has considerably developed in the last decades essentially with simple geometry particles. The purpose of this paper is to study granular systems of non-convex particles which are present in many industrial processes. Two shapes of large and two shapes of small non-convex particles resulting from the cutting of a hollow cylinder are modelled, and binary mixtures containing varying proportions of small and large particles are generated with a Monte Carlo simulation. Two different states of the granular systems are studied: suspensions and packings obtained after sedimentation. No contact force model is used and only steric repulsion is taken into account. The density, the pore size distribution and the tortuosity of the granular systems are studied. The results are compared to those obtained with granular systems of convex particles.     

An experimental investigation of the behavior of solid particles during their motion in smooth and dimpled pipes

Results are given of LDA measurements of averaged and fluctuation velocities of glass particles during their deposition in smooth and dimpled narrow pipes. Experiments reveal a decrease in the axial component of averaged velocity of particles and a significant increase in fluctuation velocities of particles during their motion in a pipe with dimples.     

An alternative approach to the ground motion prediction problem by a non-parametric adaptive regression method

Ground Motion Prediction Equations (GMPEs) are empirical relationships which are used for determining the peak ground response at a particular distance from an earthquake source. They relate the peak ground responses as a function of earthquake source type, distance from the source, local site conditions where the data are recorded and finally the depth and magnitude of the earthquake. In this article, a new prediction algorithm, called Conic Multivariate Adaptive Regression Splines (CMARS), is employed on an available dataset for deriving a new GMPE. CMARS is based on a special continuous optimization technique, conic quadratic programming. These convex optimization problems are very well-structured, resembling linear programs and, hence, permitting the use of interior point methods. The CMARS method is performed on the strong ground motion database of Turkey. Results are compared with three other GMPEs. CMARS is found to be effective for ground motion prediction purposes.     

Mechanical and electrical behaviors of polymer particles. Experimental study of the contact area between two particles. Experimental validation of a numerical model

The present paper is devoted to the analysis of mechanical and electrical behaviors observed on particulate polymer granular materials. The constituting particles obtained these physical properties by coating the polymer spherical substrate with a conducting polymer: polypyrrole (PPy) which confers electrical conducting properties to the particle, while preserving its mechanical properties. Particle contacts dominate the behavior of the granular media and, consequently, size, morphology, roughness and plasticity of the particles play a crucial role in this behavior. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to study the surface state and the contact area between neighbors. An experimental set up, based on the measurement of the displacement of contacting particles subjected to a normal force and of the variation of the electrical resistance of the packing, allowed the study of both the mechanical and electrical behaviors of the particle system. The experimental results took into account the plastic deformation under varying loading and unloading conditions; they were consistent with theories of contact mechanics, thus validating the existing models.     

Equation of motion approach to the Hubbard model in infinite dimensions

We consider the Hubbard model on the Bethe lattice with infinite Coordination number and construct (i) a systematic series of self-consistent approximations to the one-particle Green's function, G⁽ⁿ⁾(), n = 2,3,... and (ii) conduct an exact diagonalization study of the Hubbard star and the star of the stars. We present analytic and numerical results for the Mott-Hubbard transition at half filling. We find consistently (i) a critical U_c 2.5 and (ii) that the gap opens like (U-U_c)^3/2.     

A combined physical and DEM modelling approach to investigate particle shape effects on load movement in tumbling mills

The discrete element method (DEM) which is used to simulate granular flows often assumes spherical shape for particles. This assumption is legitimized by the added complexity of non-spherical shape representation, contact detection and computational cost. In this work, the difference between the dynamics of non-spherical and spherical particles was studied in detail by a combined physical and DEM modeling approach. An in-house developed DEM software called KMPC_DEM©, which was coded to handle non-spherical particles, was used to simulate the behavior of particles. To calibrate the model parameters, a model tumbling mill (100 cm diameter and 10.8 cm length) with one transparent end was used which made accurate photography possible. The tests were performed at filling of 20% and mill speed of 85% of critical speed with steel balls and wood cubes. In the simulation, each cubical particle was represented with clusters of spheres (with identical size) by particle packing algorithm for contact detection and contact-force calculation. Comparison of the simulation and experimental results showed that the difference between the measured and predicted impact toe, shoulder angle and bulk toe angle were 3, 4 and 5°, respectively. The significant change in the charge movement and structure on account of non-spherical particles was reflected in the amount of in-flight charge, and positions of shoulder, impact toe and bulk toe. It found that there was a 17% difference in the amount of in-flight of charge between cubical and spherical particles. The marked difference was attributed to higher interlocking of non-spherical particles in comparison to spherical balls. The results showed that cubical particles participated 5% more in the high energy impact action compared to that of the spherical particles. The simulation computation time increased by 35 times when the shape of particles changed from spherical to cubical.     

Heat transfer and the combustion temperature of coke particles in a fluidized bed

The temperature of carbon particles undergoing combustion in a fluidized bed is measured. Heat-transfer laws are ascertained.Notation a diffusivity of air - c heat capacity of air - D diffusion coefficient of oxygen in air - d₀, d initial and running diameters of carbon sphere - d_i diameter of inert particles - k rate constant for carbon monoxide combustion - q calorific value of carbon oxidation to CO₂ - T temperature difference between burning particle and fluidized bed - X, X_n oxygen concentration in the fluidized bed and on the surface of the burning particle - Z, Z_n running concentration of carbon monoxide and concentration on the surface of the burning particle - heat-transfer coefficient between fluidized bed and burning particle - _m maximum heat-transfer coefficient between fluidized bed and a stationary body submerged in the bed - masstransfer coefficient between fluidized bed and burning particle - thermal conductivity of air - kinematic viscosity of air - ₀, gr, ₄ density of oxygen, air, and inert material - relative thickness of burning gas layer - relative thickness of diffusion boundary layer Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 21–27, January, 1982.     

Determining the heat losses due to radiation in an axially symmetric high-temperature stream of spherical particles

The mean radiation losses in a diverging axially symmetric stream of spherical particles are determined on the basis of a probabilistic estimate.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 5, pp. 815–820, November 1971.     

Shear-induced melting and reentrant positional ordering in a system of spherical particles

Computer simulations of dense systems of soft spheres subjected to a shear flow show not only the phenomena of shear-induced melting—transition from a crytalline to an amorphous state—but, at high shear rates, a second nonequilibrium phase transition to a new positionally ordered state. The particles form strings parallel to the stream lines; the strings, in turn, are arranged in a hexagonal pattern. Simulation data on the rheological properties, non-Newtonian viscosity, shear dilatancy, and stress growth and values for the shear moduli are presented; some theoretical ideas for the explanation of these phenomena are discussed.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

An investigation of the effect of the shape and density of solid particles on their motion in an isothermal curvilinear flow

The results of an experimental and theoretical investigation of the motion of an aerosol with variation of its shape, density, and size are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 5, pp. 929–932, November, 1970.