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Practical use of mathematical models, that describe complex physical processes, connected with heat and mass transfer (the working process of diesel engine in particular), often runs into considerable difficulties. These difficulties are engendered by the general character of the problem, the large amount of characteristics considered, the complexity of their interdependence and as a sequence the cumbersomeness and inconvenience the mathematical apparatus itself. To overcome these obstacles it is helpful in some cases to introduce some auxiliary parameters, and in other cases - to find a successful functional parametric representation of the characteristics investigated. Both above mentioned approaches are components of the parameterization method and play a significant role in solving technological problems by means of mathematical modeling. Use of parameterization is shown by three examples.

A method of calculation is proposed that allows, on the basis of cause-and-sequence approach, to improve the main quantitative characteristics of diesel engines by means of optimization of fuel injection conditions and finding out parameters of fuel injection equipment (TA) for their realization. When using the method, it is assumed that certain technical requirements and limits are to be observed (for instance, the maximum combustion pressure, engine noise, emission standards etc.). The two stages of the method are reflecting the natural sequence of TA design. Components of a developed mathematical model are described in this paper. In particular, special attention is paid to an original phenomenological model of a dispersed fuel spray on the basis of experimental data pertaining to its structure and mixture formation mechanism.