SELF-SUSTAINED JET OSCILLATION PHENOMENA RELATED TO AXISYMMETRIC ROCKET JETS INTERACTION DURING TAKE-OFF

摘要

Powerful self –sustained oscillations of axisymmetric set of rocket jets are predicted duringrntake-off, slow lift and initial stage of flight due to jets interaction with symmetric take-offrntable construction elements, such as rocket supporting ring and mutual jet interaction duringrninitial stage of flight. Discrete jets system is modeled by continuos circular jet issuing out ofrncircular orifice in an impedance plate. Circular jet could either collapse in unconfined space orrninteract with symmetric take-off table elements (say, rocket-supporting ring). Both kinds of jetrninteraction lead to generation of volume- flow sources formed in the region of jet collision orrnobstacle interaction. These sources production rates are related directly to jet deflectionsrninside or outside inner jet-bounded axisymmetric volume. Values of jet roots deflection inrntheir turn are governed by system of axial standing acoustic waves formed in sad volume. Byrnmeans of Nyquist stability criteria (both phase and amplitude) conditions of self-sustainedrnloop process in axisymmetric volume are derived and their dependence on system parametersrnare determined. Subsonic and supersonic jet flow cases are analyzed. Slowly changing central oscillation frequency with system lift (narrow band) oscillation phenomenon is thus predicted.rnPredictions are compared to available experimental data.