Regularities of thermoacoustic oscillations in Lehmann's system with a reverse movement of the coolant

The technique is developed for calculations of boundaries of instability, frequencies and amplitudes of self-oscillations of the heat carrier, self-excited at its movement in the vertical channel when warmth from a source of constant power is locally brought to it. Unlike classical generators of thermoacoustic fluctuations: Rijke's pipe and Lehmann's system, it is supposed that the main stationary flow is collinear with gravity. To exclude a surge of self-oscillations of nature is assumed that the flow is created with a supercharger pressure of a monotonically decreasing characteristic. The resulting mathematical model allows theoretically to determine the conditions of self-excitation of self-oscillations under consideration and to assess the influence of various parameters on their shape.