Self-exited oscillation in a combustion chamber driven by phase change in the liquid fuel feed system C. Hassa 1, *, J. Heinze, U. Meier, Ch. Heeger 2 , Ph. Trunk and A. Dreizler 1 German Aerospace Center, Institute of Propulsion Technology, Linder Höhe, 51147 Köln 2 TU Darmstadt, Fachbereich Maschinenbau, Fachgebiet Reaktive Strömungen und Messtechnik, Petersenstraße 32, 64287 Darmstadt [Submission: July 31, 2010; Revised Submission: April 29, 2011; Accepted: June 14, 2011] A new mechanism for the generation of a self-exited oscillation of combustion in a generic combustion chamber typical for aeroengine combustors is described. The cause of the oscillation is the phase change from liquid to vapour which happens when the preheat temperature of the air flowing through the burner exceeds the boiling temperature at the operating pressure and the fuel flow is so low that heat transfer to the liquid fuel causes evaporation within the fuel channels of the burner. Liquid fuel and vapour alternatively enter the airstream of the burner. This leads to an unstable situation for the flame. Measurements of chemiluminescence and liquid fuel show nearly complete extinction and re-ignition for the limit cycle. Prevention of the oscillation is possible by better thermal management of the fuel path. 1. INTRODUCTION Operating cycles of aero-engines lead to combustor inlet temperatures, which are higher than the boiling point of kerosene for a majority of the operating points. For conventional rich-lean combustors, the residence time of the fuel in the fuel lines, if properly isolated from the hot gas path, is small enough to prevent boiling. However for lean combustors, the circumference of the exit of the fuel lines is longer due to the larger size of lean burners having more than twice of the size of the airflow of conventional burners. Since minimal channel heights are imposed for practical fuel systems, the velocity of the liquid decreases, augmenting the residence time. For the validation of 2-phase flow codes, a research burner was built. It is investigated in a generic single sector combustor with optical access operating at intermediate pressures with respect to aeroengine cycles. During the commissioning, on the search of a lean operating point representing a part load condition, a combustion International journal of spray and combustion dynamics · Volume . 3 · Number . 4 . 2011 – pages 273–284 273 * Corresponding Author: christoph.hassa@dlr.de