A DIFFERENTIAL EQUATION OF THE FIRST LAW OF THERMODYNAMICS FOR MODELING THE INDICATOR PROCESS OF A DIESEL ENGINE

摘要

Several improvements to the mathematical model of theindicator process taking place at a diesel engine cylinder areproposed. The thermodynamic behavior of working medium isdescribed by the equation of state, valid for real gases.Mathematical dependencies between thermal parameters (P, T,v) and caloric parameters (u, h, cv , cp ) have been obtained. Animproved mathematical model, based on the first law ofthermodynamics, has been developed, taking into accountworking medium imperfections. The numerical solution of thesimultaneous differential equations is made by a method ofRunge-Kutta type. The computing procedure is iterative.Calculations in respect to the caloric parameters (u, h, cv and cp) for various gases under pressure up to 25 MPa andtemperature up to 3000oC have been carried out. The resultsshow, that there are significant differences between the values,calculated by equations for ideal gases, and the proposedequations for real gases under high pressure and temperature.Actual applied problems for two-stroke turbocharged enginesSulzer-RLB66 and 8DKRN 74/160 have been solved. Thecomparison between the experimental data and numericalresults show very good agreement. The numerical experimentsshow that if the pressure is above 8-9 MPa, the workingmedium imperfections must be taken into consideration.