Frequency characteristics of a coaxial gas damper for booster feed line

In development and maintenance of liquid rockets it is essential to ensure its stability in relation to longitudinal oscillations of the body (longitudinal stability, pogo effect) for all possible disturbances. It is known that one of the most effective ways to ensure the longitudinal stability is to use gas dampers-accumulators installed in the feed line at the engine inlet. The damper in the feed line produces additional compliance, thus making it possible to eliminate the coincidence of the fundamental natural frequency of the pressure fluctuations in the feed line and the natural frequencies of the rocket body, which is necessary for providing the longitudinal stability. The damper parameters are selected on the basis of mathematical modeling and experimental data. In this paper, a nonlinear mathematical model of a coaxial gas damper is developed with the use of the ideal-gas law equation for an adiabatic process and the Bernoulli and Saint-Venant – Vantsel equations. The mathematical model is used to calculate the frequency characteristics of the damper in the form of input acoustic conductance. The results obtained make it possible to take into account the contribution of passage sections of the throttles to the performance of the damper at the design stage, as well as to select its parameters in simulating processes in the feed lines to solve the longitudinal stability problem.