SOME PROBLEMS WITH THE MATHEMATICAL MODELING OF ELECTROMAGNETIC VIBRATORS USED FOR TRANSPORTING BULK MATERIALS

Mathematical modeling with the original approach is used to study the dynamics of low-frequency electro-vibration machines while taking the technological load into account. Based on the mathematical analysis of differential equations describing the oscillatory motion of electromagnetic vibration exciters, the existing mathematical model has been corrected to describe the action of a semiconductor diode in the power circuits of single-cycle vibrators. Modeling nonlinear dynamic systems reveals the difficulties of obtaining the amplitude-frequency characteristics of the associated discrete change in the frequency of the driving force, as well as ways to overcome them

Modeling of the burning process in the piston engines with various concepts of the working proces

In this paper, the results of modeling of the burning process in the piston engines whose working process is realized on the basis of various conceptual approaches are presented: in diesel with direct injection of the fuel; in a gas engine with spark ignition; and in a two-fuel engine (in the gas-diesel), where the mixture of natural gas and air ignites with the help of the fuse dose of the diesel fuel. The models of burning based on the different in-principle approaches are analyzed and used. Verification of the models is performed by a comparison of the results of modeling with the experimental diagrams. The specific values of the empirical coefficients, used in modeling of the burning proces in the engines under study, are determined. The practical recommendations on the choice of the burning model depending on the working process conception are given

Structuring and Electric Conductivity of Polymer Composites Pyrolysed at High Temperatures

The new conductive monolithic materials have been created on the basis of phenolformaldehyde mixtures and epoxy resins at the presence of some silicon organic compounds and fiber glasses annealed in vacuum and hydrogen media. The conductive, magnetic and some other properties of these materials were investigated. It is proved experimentally that the obtained products are characterized by semi-conductive properties, the level of conductivity and conductive type of which, are regulated by the selection of technological methods. The density and mobility of carriers can be increased by increasing the annealing temperature up to definite levels. The temperature dependence of the electrical conductivity and charge mobility are described by Mott formulas. The magnetic properties of the annealed materials are investigated by ESR method. It is established that in the annealing process free radicals and other paramagnetic centers are formed. On the basis of obtained results it is proposed to form the conducting clusters for transporting the charge between them