РАСЧЕТ ЭНТРОПИИ РАБОЧЕГО ТЕЛА В ЦИЛИНДРЕ ДИЗЕЛЯ

Abstract

When using the method of numerical modeling for working processes in diesel engines, parameters are described by three equations: the first law of thermodynamics, mass balance and Clapeyron equation. They are combined in a system of differential equations and solved together at each step of the modeling. If the angular velocity ω of crankshaft is the same, it’s convenient to take a crankshaft angle φ as the argument. If the system is solved with reference to pressure p , temperature T ц and mass G it’s also possible to determine entropy s of working medium. In order to achieve acceptable accuracy of modeling the isochoric heat capacity cv cannot be considered as constant value as it results big calculating error. In order to avoid this, it’s enough to determine cv by quadratic polynomial of absolute temperature of working medium. The offered procedure was checked by numerical modeling of working process of two-stroke engine MAN-B&W 6S26MC and four stroke engine 6 ChN 25/34-2. Results showed that working processes of two- and four-stroke engines in T - s coordinates are looking identically. Moreover, the working processes of engines in T - s coordinates have the likeness of kind with theoretical diagram of Sabathe cycle. This suggests that it’s possible to create quality indexes in order to assess the difference between theoretical and real processes and work out recommendations for process improving.