Lytviak O. Models and methods of analysis of dynamic processes in the automatic control system of a turboshaft gas turbine engine of a helicopter

The thesis is devoted to the solution of the actual scientific and applied problem of predicting and eliminating the development of self-oscillations in the automatic control sys-tem of the revolutions of a free turbine of a turboshaft gas turbine engine of a helicopter based on the development of appropriate mathematical models and methods. As a result of the analysis of the state of the problem, it was found that at the moment the problem of the development of self-oscillations in the automatic control system of the free turbine revolu-tions of turboshaft GTEs of helicopters with a hydromechanical control system has not been completely solved, which necessitated the improvement of the classical mathematical tools. In the dissertation work, a complex of interrelated models of the dynamics of the au-tomatic control system of revolutions of a free turbine of a turboshaft GTE of a helicopter and a nonlinear element-by-element model of the static characteristics of a hydromechani-cal regulator was developed. On the basis of in-depth experimental studies of the processes and characteristics of the elements of the hydromechanical regulator, new data were ob-tained, which made it possible to eliminate contradictions in the mathematical representa-tion of the functions of the ACS elements and improve their mathematical models. Meth-ods for studying self-oscillations in complex mechanical systems were further developed and a criterion for predicting self-oscillations in the automatic control system of the revolu-tions of a free turbine of a turboshaft GTE during its ground tests on a hydraulic brake system and flight tests as part of a twin-engine power plant of a helicopter was determined. The developed models and the obtained research results form the basis of the method for predicting the tendency of the automatic control system of revolutions of the free turbine of a turboshaft GTE to the development of self-oscillations. To carry out correct ground tests of turboshaft gas turbine engines of helicopters, the requirements for the dynamic characteristics of the hydraulic brake system were formulated for the first time and the law for regulating its load was substantiated, which provides complete emulation of the charac-teristics of helicopter rotor. The reliability of the new scientific provisions and conclusions of the thesis is confirmed by the results of experimental data obtained in the study of phys-ical objects. The practical significance of the obtained results lies in the fact that the devel-oped methods and models make it possible to predict the tendency of pump-regulators of the HP-3 type (SE KhMP "FED", Ukraine) to the development of self-oscillations without carrying out motor tests, reduce the repair time and eliminate the problem of self-oscillations for motors of the type TV3-117 (Motor Sich JSC, Ukraine).