The well-known algorithm of mathematical modeling in nodal values has been used to analyze the operation of a rotary-blade engine with external heat supply. The calculation procedure allows obtaining the required combination of exchange processes between the introduced elements using the formation of a graph in the form of a connection matrix when the switching of nodes depends on time. The values of thermodynamic functions found as a result of calculation by a known algorithm were compared with their values taken from indicator diagram characteristics. The influence of the finite rate of heat and mass transfer processes on the pressure and temperature values within a repetitive cyclic process was demonstrated.