Khoryak N. The low-frequency stability analysis of a main liquid rocket propulsion system and its dynamic compatibility with a rocket structure

Object of research - a low-frequency all-engine oscillations in the main liquid rocket propulsion systems and POGO-oscillation of launch vehicles at the active trajectory leg ; aim of research - an improvement of the method of the determination of the rocket propulsion systems low-frequency stability and its dynamic compatibility with the rocket structure ; methods of research - mathematical modeling methods involving control theory of the liquid propulsion engines, theory of cavitation oscillations in the pump systems , theory of automatic control systems and vibration theory, the first method of Lyapunov, phenomenological approach to the description of the low-frequency dynamics of the gas path; approximation methods, numerical linear algebra and non-linear mathematical programming; scientific novelty - the method of determination of the rocket propulsion systems low-frequency stability and it's dynamic compatibility with the rocket structure which is based on the the matrix spectrum calculation and decomposition of multiple-loop dynamic system "a liquid rocket propulsion system - a rocket structure" is improved; first, based on the mathematical modeling, the necessity of taking into account the influence of energy dissipation on the natural longitudinal vibration characteristics of the liquid rocket structure in determining of dynamic compatibility liquid rocket propulsion system with rocket structure is substantiated; first a linear mathematical model of the dynamic interaction of liquid rocket propulsion system and rocket structure, which include the effect of energy dissipation on the longitudinal vibration characteristics and dissipative connection between the longitudinal modes of structure, is build; first as a result of numerical studies it's found out that low-frequency instability of liquid rocket propulsion engine with staged combustion can be caused by vibration in the loop "turbo-pump assembly - gas generator", with an important influence had by the lag time in the equations of gas generator dynamics; branch - aerospace.