Математический анализ процесса СВЧ нагрева технологическими комплексами

Анотація

MATHEMATICAL ANALYSIS OF PROCESS SHF HEATING BY TECHNOLOGICAL COMPLEXES

Y. Fedyushko А. Fedyushko

It is known that the temperature change of the dielectric leads to a change in its electrical parameters such as the complex dielectric constant, the damping coefficient, thermal conductivity, specific heat and density. To account for changes in these parameters in the mathematical modeling of microwave heating is necessary to conduct preliminary experiments to reveal the dependence of these parameters on the temperature.

The purpose of research - study approach, consisting in the collection and processing in the process of changing the microwave processing of information directly in the operation of microwave technology complex.

Materials and methods of research. Microwave processing plants is carried out specially organized exposure of electromagnetic energy of microwave and EHF (microwave processing) on materials, substances and biological objects in order to change their properties. At high intensity and long duration exposure to electromagnetic energy is a significant increase in the temperature of the dielectric with a possible phase change.

Design and development of universal microwave process plants are often hampered by the fact that no adequate mathematical models of processes of electromagnetic and thermal fields in dielectrics. The complexity of the situation lies in the fact that the electrical and thermal parameters of the dielectric and electric field changes as the temperature changes. The dependence of these parameters on the temperature can be determined as a rule, only experimentally.

However, in reality, it may happen that dielectrics to be microwave treated, these parameters are depending on the temperature, different from those obtained in the experiment. For example, when the microwave processing of multicomponent mixtures, even a slight change of the percentage of its component parts can lead to a noticeable change of these parameters depending on the temperature. Therefore microwave technology unit must track these changes and automatically adjust quickly enough.

The results of research. During the microwave treatment should be carried out such a control pulse duration and amplitude supplied to the anode magnetrons multi-element electromagnetic field excitation system, in which will be achieved and will be supported by the required distribution of the temperature field in the dielectric.

In the latter case, the control is carried out on the basis of the constructed mathematical model whose parameters are adjusted if necessary.

Therefore, the microwave process plant was seen as a system of automatic control the adaptation parameters of a mathematical model of the measured values of the dielectric parameters (dielectric permittivity, attenuation coefficient, speed of the dielectric strength of the electric field, and others.), Varies with the temperature of the dielectric.

It is obvious that the work of this microwave process plant will be of a cyclical nature, with which will alternate control cycles and cycles of correction parameters and the structure of the mathematical model.

To select the control points used approaches based on a more complete account of a priori information about the fields to be monitored.

In each cycle, the measurement of these fields are described by deterministic, but advance unknown functions of spatial coordinates, changing from one measurement cycle to the next. In this regard, the function describing the dependence of the temperature field of the spatial coordinates, can be considered the implementation of a number of statistical functions. This approach was used in the design of control system of temperature field and the electromagnetic field.

Synthesis of spatial field (electromagnetic or temperature) control system consists of two main tasks: determining the coordinates of the placement of sensors, and a moderate recovery of the continuous function from the measured values of the field in the control points.

Сonclusions

Simultaneous optimization of coordinates of control points and the algorithm for computing the estimates is difficult solvable problem, so the problem of choosing the coordinate control points and the algorithm for calculating the coefficients estimates should be considered separately.

Each of the random temperature field corresponds to the value of the probability density, which characterizes the frequency of occurrence of this implementation. That is, we can talk about a "more likely" and "less likely" implementations. With this in mind, the task of restoring the temperature field in the measured values of the control points can be summarized as follows: among all continuous functions which have the points control the measured values, to find a function for which the probability density value is the highest.