Design of Injectors for Self-sustaining of Combustion Chambers Acoustic Stability

CHAMBERS ACOUSTIC STABILITY Vladimir Bazarov Moscow Aviation Institute (State Technical University) 4, Volokolamskoe Shosse, Moscow 125080, RUSSIA E-mail: [email protected] Abstract Comparative analysis of the injector development history in order to eliminate acoustic instability in combustion chambers of LOX/kerosene big thrust engines both of gas generator and staged combustion cycle such as F-1, RD-170 and some experimental engines is presented in the Paper. It was studied what stationary and dynamic parameters of injector elements and the injector assembly as a whole were changed during such a development and what kind of influence on instability they provided. It was discovered that in every case of successful efforts to achieve stability, alongside with the decreasing of amplification qualities of the combustion zone by means of decreasing atomization and mixing efficiency that decreased to some extend combustion chamber specific impulse, increasing acoustic losses in the combustion chamber by means of installation of baffles and/or acoustic cavities, injectors in stable operated combustion chambers provided selfsustaining of the operational process, which under the influence of pulsation amplitude provided decreasing of the combustion zone amplification qualities. Methods of instability mechanisms diagnostics and instability elimination by means of changing of injector dynamic characteristics are proposed and compared with the results of fire tests in model combustion chamber. Some useful expressions are presented in the Paper to define dynamic characteristics of jet and swirl injectors as well as interference of swirled fuel flow with the central Ox-rich gas stream.