Affiliations: Space Propulsion, German Aerospace Center (DLR),
Langer Grund, D-74239 Hardthausen, Germany. e-mail: Volker.Schmidt@dlr.de
Abstract: Phenomena such as flame propagation, flame/spray interaction and
flame stabilization during the transient ignition process in a cryogenic model
rocket combustor are investigated on sub-millisecond time scale. Diagnostic
techniques developed to characterize the stationary spray flame are applied to
investigate the transient evolution of the LOX-spray and the flame front during
the ignition process. Ignition is initiated by focusing a pulsed laser into the
combustion chamber. Thus, ignition time as well as the position of ignition is
well defined. This and the exact control of the delay between ignition and
detection time allowed the observation of the evolution of the flame front. The
distribution of the liquid oxygen phase and the velocity of LOX droplets and
ligaments are determined by light sheet techniques using a double-pulsed laser
system. Simultaneously the position of the flame front is measured by recording
the spontaneous emission of the OH-radical. By varying the delay time t between
ignition and detection in a series of test runs, the transient ignition
phenomena has been investigated in the interval from 0 to 5 ms after
ignition.